Forecast Discussions mentioning any of
"HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 08/21/13
AREA FORECAST DISCUSSION
NWS PHOENIX AZ
833 PM MST TUE AUG 20 2013
.SYNOPSIS...
STRONG HIGH PRESSURE ALOFT WILL KEEP TEMPERATURES WELL ABOVE NORMAL
ACROSS THE REGION THROUGH WEDNESDAY. TEMPERATURES WILL THEN SLOWLY
FALL FROM THURSDAY ONWARD INTO THE UPCOMING WEEKEND AS THE HIGH
PRESSURE WEAKENS. THUNDERSTORM ACTIVITY WILL BE MAINLY CONFINED TO
THE HIGHER TERRAIN NORTH AND EAST OF PHOENIX THROUGH FRIDAY...THEN
INCREASE DRAMATICALLY FROM SATURDAY ONWARD INTO EARLY NEXT WEEK AS
DEEP SOUTHERLY FLOW ALOFT DEVELOPS OVER THE REGION...WHICH WILL THEN
BEGIN TO IMPORT DEEP MOISTURE NORTHWARD INTO THE DESERT SOUTHWEST.
&&
.DISCUSSION...
ALTHOUGH MONSOON MOISTURE IS ON THE SCANT SIDE...A SUFFICIENT AMOUNT
OF THUNDERSTORMS DEVELOPED THIS AFTERNOON ACROSS SOUTHEAST ARIZONA
TO PRODUCE OUTFLOWS THAT RUSHED INTO OUR LOWER DESERTS EARLY THIS
EVENING. A FEW AREAS ACROSS FAR SOUTHERN MARICOPA AND PINAL COUNTIES
SAW A BIT OF LIGHT RAIN...BUT THE BIGGEST IMPACT WAS THE 20-30MPH
SOUTHERLY OUTFLOW WINDS AND THE LARGE AREA OF BLOWING DUST THAT
DEVELOPED BECAUSE OF THE OUTFLOWS. CURRENT RADAR TRENDS SHOW
ACTIVITY QUICKLY WINDING DOWN ACROSS SOUTHEAST ARIZONA...BUT SOME
ONGOING SHOWERS AND THUNDERSTORMS REMAIN ACROSS THE MOGOLLON RIM
AND INTO CENTRAL GILA COUNTY. THIS ACTIVITY IS MAKING SOME HEADWAY
TO THE WEST INTO THE DRIER AIR WITH PWATS OF BETWEEN 1-1.25 INCHES.
LATEST RUN OF THE HRRR DOES SHOW THESE SHOWERS AND STORMS CONTINUING
FOR A FEW MORE HOURS AND POSSIBLY REACHING THE SOUTH-CENTRAL LOWER
DESERTS. HAVE ADDED SOME LOW END SLIGHT CHANCE POPS ACROSS THE
EASTERN HALF OF MARICOPA AND SOUTHERN GILA COUNTIES FOR THE EARLY
OVERNIGHT HOURS. QUITE A LARGE EXPANSE OF MID AND HIGH CLOUDS HAVE
ALSO SPREAD ACROSS THE REGION AND LIKELY LASTING THROUGH MUCH OF THE
OVERNIGHT HOURS. TAKING THIS INTO ACCOUNT...THINK OVERNIGHT LOWS
ACROSS SOUTH-CENTRAL ARIZONA WERE A BIT ON THE LOW SIDE...SO WARMED
UP SOME AREAS A FEW DEGREES WITH CENTRAL PHOENIX NEAR 90 FOR
TONIGHT.
&&
.PREVIOUS DISCUSSION...
THIS WEEKEND...LATEST GFS/ECMWF CONTINUE TO INDICATE THAT DEEPER
MOISTURE WILL BE ADVECTED INTO THE DESERT SOUTHWEST AND POPS WERE
INCREASED THIS MORNING FOR THE SATURDAY-MONDAY PERIOD. ADDITIONAL
ADJUSTMENTS WERE MADE THIS AFTERNOON TO LOWER HIGH
TEMPERATURES...DUE TO THE EXPECTED CLOUDINESS AND SCATTERED
PRECIPITATION.
&&
.PREVIOUS DISCUSSION...
A VERY SLOW INCREASE IN CONVECTIVE ACTIVITY IS LIKELY FROM WEDNESDAY
ONWARD INTO FRIDAY AS LEFTOVER MOISTURE FROM THUNDERSTORMS OVER
MEXICO IS PUSHED NORTHWARD INTO THE REGION. THE MAIN CONCERN OVER
THE NEXT COUPLE OF DAYS IS THE VERY HOT TEMPERATURES. CURRENT MODEL
DATA IS FORECASTING AFTERNOON 850MB TEMPERATURES IN THE 28-30C RANGE
BOTH TODAY AND ON WEDNESDAY. THESE TEMPERATURES SUPPORT HIGHS IN THE
LOWER DESERTS IN THE 110-114F RANGE EACH DAY...WITH EXCESSIVE HEAT
CRITERIA BEING MET ACROSS THE LOWER DESERTS. TEMPERATURES SHOULD
COOL A BIT ON THURSDAY AND FRIDAY AS THE RIDGE WEAKENS...WITH 500MB
HEIGHTS FALLING FROM THE 590-592DM RANGE ON WEDNESDAY TO THE
586-588DM RANGE BY FRIDAY.
A DRAMATIC UPTICK IN THE MONSOON ACTIVITY NOW APPEARS QUITE LIKELY
FROM SATURDAY ONWARD INTO EARLY NEXT WEEK AS THE MAIN LONG-WAVE
UPPER RIDGE AXIS SHIFTS OFF TO THE EAST OVER THE CENTRAL PLAINS AND
A LONG-WAVE TROF DIGS SOUTHWARD JUST OFF THE WEST COAST. THIS
PATTERN CHANCE WILL ALLOW DEEP SOUTHERLY FLOW TO DEVELOP ALL THE WAY
FROM THE DEEP TROPICS OFF THE WEST COAST OF MEXICO NORTHWARD INTO
THE SOUTHWEST US. ATMOSPHERIC MOISTURE VALUES ARE EXPECTED TO
SHARPLY INCREASE OVER THE REGION...WITH THE ECMWF SHOWING 1000-700MB
MIXING RATIOS RISING FROM AROUND 8 G/KG ON FRIDAY TO 12-16 G/KG FROM
SUNDAY ONWARD INTO NEXT TUESDAY...WITH PWATS IN THE 1.80-2.00 INCH
RANGE. IN ADDITION...BOTH THE GFS AND ECMWF TAKE A POTENTIAL
TROPICAL CYCLONE NORTHWESTWARD ALONG OR JUST WEST OF THE WEST COAST
OF BAJA CALIFORNIA. THE COMBINATION OF THE DEEP SOUTHERLY FLOW AND
POSSIBLE TROPICAL LOW PRESSURE TO THE WEST WILL LIKELY PRODUCE THE
1ST SIGNIFICANT GULF SURGE THAT WE HAVE SEEN FOR A WHILE...LIKELY
PUSHING SFC DEWPOINTS UP WELL INTO THE 60S...OR EVEN LOWER 70S
ACROSS THE LOWER DESERTS LATE FRIDAY NIGHT OR EARLY SATURDAY...WHICH
WOULD ALLOW WIDESPREAD THUNDERSTORM ACTIVITY TO DEVELOP EACH
DAY...WITH THE POTENTIAL FOR HEAVY RAINFALL FROM THESE
STORMS...ESPECIALLY IF A TROPICAL SYSTEM DOES INDEED TRACK
NORTHWESTWARD ALONG OR NEAR BAJA CALIFORNIA. THE INCREASE IN
CLOUDS...MOISTURE...AND RAINFALL IS EXPECTED TO PUSH HIGH
TEMPERATURES DOWNWARD TO BELOW-NORMAL VALUES...PERHAPS KEEPING HIGHS
BELOW 100F AT SOME LOWER DESERT LOCATIONS ON ONE OR MORE OF THE DAYS.
&&
.AVIATION...
SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA AND KSDL...
THUNDERSTORM OUTFLOWS THAT HAVE AFFECTED THE PHOENIX TERMINALS THIS
EVENING WILL ABATE WITH SOUTHERLY WINDS DIMINISHING AND TURNING TO
THE EAST AFTER MIDNIGHT. AN AREA OF SHOWERS AND THUNDERSTORMS OVER
THE HIGH TERRAIN OF GILA COUNTY COULD MAKE IT/S WAY INTO THE FOR
EAST PHOENIX AREA BY 06Z...BUT WITH THE DRY AIR IN PLACE THIS
ACTIVITY IS EXPECTED TO DIMINISH BEFORE REACHING KPHX. EXPECT TO SEE
A BROKEN TO OVERCAST MID LEVEL CLOUD DECK THROUGH MOST OF THE
OVERNIGHT HOURS. MONSOON ACTIVITY FOR WEDNESDAY WILL AGAIN HAVE THE
CHANCE TO AFFECT THE AREA TAF SITES...BUT MOSTLY FROM THUNDERSTORM
OUTFLOWS.
SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH...
CONTINUED QUIET WEATHER FOR THE TERMINALS WITH PATCHES OF FEW TO SCT
SKIES LINGERING OVERNIGHT. WINDS WILL REMAIN LIGHT AND LESS THAN
12KTS THROUGH THE TAF PERIOD WITH NO WEATHER IMPACTS TO AVIATION
OPERATIONS.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
FRIDAY THROUGH TUESDAY...
SOUTHERLY FLOW BETWEEN THE MONSOON HIGH IN THE SOUTHERN PLAINS AND A
LOW PRESSURE SYSTEM ALONG THE WEST COAST WILL TRANSPORT DEEPER
MOISTURE INTO THE DESERT SOUTHWEST. LATE WEEK THROUGH THE WEEKEND
WILL SEE ABOVE NORMAL RAIN CHANCES...PARTICULARLY ACROSS
ARIZONA...ALONG WITH AT OR BELOW NORMAL TEMPERATURES. RAINFALL
AMOUNTS MAY EVEN BE ENHANCED BY INCREASING TROPICAL MOISTURE SUNDAY
AND MONDAY...MAINLY EAST OF THE COLORADO RIVER. WINDS WILL BE
RELATIVELY LIGHT THROUGH FRIDAY AND FAVOR NORMAL DIURNAL SPEEDS AND
DIRECTIONS...WITH INCREASING MAINLY SOUTHERLY WIND EXPECTED OVER THE
WESTERN DESERTS THIS WEEKEND WITH GUSTS IN EXCESS OF 25 MPH
POSSIBLE.
$$
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...EXCESSIVE HEAT WARNING UNTIL 8 PM MST WEDNESDAY
AZZ022-023-027-028.
CA...NONE.
&&
$$
VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX
DISCUSSION...KUHLMAN
PREVIOUS DISCUSSION...HIRSH/PERCHA
AVIATION...NOLTE
FIRE WEATHER...CB/HIRSCH
AREA FORECAST DISCUSSION
NWS PHOENIX AZ
955 PM MST SUN AUG 18 2013
.SYNOPSIS...
VERY WARM DAYS WITH A RELATIVELY HIGH DEGREE OF MONSOON MOISTURE
WILL CONTINUE THE THREAT OF AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS THIS WEEK OVER SOUTHWEST AND SOUTH CENTRAL ARIZONA.
SHOWER INTENSITY AND COVERAGE WILL VARY FROM DAY TO DAY. A VERY WARM
AIRMASS OVER THE REGION HAS THE POTENTIAL TO RESULT IN DESERT HIGH
TEMPERATURES NEAR THE 110 DEGREE MARK THROUGH THURSDAY.
&&
.DISCUSSION...
UPPER LEVEL LOW CENTERED JUST OFF THE CENTRAL CALIFORNIA COAST
HELPED ADVECT MOISTURE INTO THE MOHAVE DESERT REGION TODAY ALONG
WITH UPPER LEVEL DIFFLUENCE TO AID STORM DEVELOPMENT. IT ALSO
PROVIDED SOME VERTICAL WIND SHEAR TO AID IN STORM INTENSITY. MOST OF
THE ACTIVITY WAS OUTSIDE OF OUR FORECAST AREA IN VEF CWA.
HOWEVER...ON THE EASTERN PERIPHERY OF THE INFLUENCE FROM THE UPPER
LOW...SOUTHERN ARIZONA HAD ANOTHER FAIRLY ACTIVE NIGHT. WHILE
OUTFLOWS DID MAKE THEIR WAY THROUGH THE PHOENIX METRO AREA...ONLY
ISOLATED STORMS HAVE MANAGED TO FORM...THIS TIME OVER THE WEST
VALLEY. IR IMAGERY SHOWS A LARGE AREA OF COLD CLOUD TOPS...FROM
DECAYING CONVECTION ALONG AND NEAR THE MEXICO BORDER. THIS
MAY HAVE BEEN AIDED BY AN APPROACHING WAVE NEAR CENTRAL AND SOUTHERN
BAJA MEXICO. BOTH THE 00Z GFS AND NAM FORECAST THE WAVE TO MOVE
SLOWLY NORTHWARD ACROSS BAJA...NORTHWEST MEXICO...AND ARIZONA
TONIGHT AND MONDAY. IN THE PROCESS...THE MODELS DEPICT VARYING
AMOUNTS OF UPPER LEVEL DIVERGENCE AHEAD OF THE WAVE AXIS. THIS MAY
HELP KEEP PESKY STORM ACTIVITY GOING OVERNIGHT INTO THE MORNING
HOURS. THERE ARE ALSO SOME INDICATIONS IN RADAR DATA OF AN MCV
ASSOCIATED WITH THE THE SOUTHERN ARIZONA STORM REMNANTS. EARLIER
RUNS OF HRRR MODEL FORECAST THE BORDERLAND CONVECTION PRETTY WELL.
IT ALSO DID A PRETTY GOOD JOB OF NOT SHOWING WIDESPREAD STORM
ACTIVITY OVER THE SOUTH-CENTRAL DESERTS THIS EVENING. THE LATEST RUN
IS NOT THAT OPTIMISTIC WITH LATE NIGHT SHOWERS...NOR ARE THE GFS AND
NAM...BUT WILL HOLD ON TO SLIGHT CHANCE POPS FOR THE AFOREMENTIONED
REASONS. WITH LINGERING CLOUD COVER...OVERNIGHT TEMPS WILL REMAIN
WARM AND THUS WILL ALLOW EXCESSIVE HEAT WARNING TO EXPIRE EARLY
MONDAY.
&&
.PREVIOUS DISCUSSION ISSUED 255 PM...
TONIGHT...
AN UNSCHEDULED MORNING YUMA PROVING GROUNDS (YPG) WEATHER BALLOON
SOUNDING SHOWED A PLUME OF RELATIVELY HIGH LOW LEVEL MOISTURE MOVING
NORTH UP THE COLORADO RIVER. AFTERNOON WATER VAPOR IMAGERY ALSO
SHOWED A NOTICEABLE DEGREE OF UPPER LEVEL DIFLUENCE ACROSS SOUTHEAST
CA...SOUTHERN NEVADA...AND NORTHWEST MEXICO RELATED TO THE PACIFIC
TROF ALONG THE CENTRAL CA COAST. THEREFORE THE CHANCE OF SHOWERS AND
THUNDERSTORMS WILL CONTINUE ACROSS PARTS SOUTHEAST CA AND THE
COLORADO RIVER VALLEY THROUGH THIS EVENING. A BROAD BRUSH THREAT FOR
SHOWERS AND THUNDERSTORMS WILL CONTINUE ELSEWHERE IN SOUTHWEST AND
SOUTH CENTRAL AZ THE REMAINDER OF THE AFTERNOON AND EVENING...WITH A
HINT THAT CONVECTIVE ACTIVITY MAY LAST INTO THE NIGHT DUE TO A
DISTURBANCE MOVING INTO THE REGION FROM THE BAJA.
MONDAY THROUGH FRIDAY...
SOME DRYING IS EXPECTED OVER PORTIONS OF SOUTHEAST CA AND THE
COLORADO RIVER RELATED TO THE CA TROF MONDAY AND TUESDAY. OTHERWISE
THE REMAINDER OF AZ WILL BE UNSEASONABLY WARM AND MARGINALLY MOIST.
A THREAT OF AFTERNOON AND EVENING SHOWER AND THUNDERSTORM ACTIVITY
WILL CONTINUE THIS WEEK...WITH STORM INTENSITY AND COVERAGE VARYING
FROM DAY TO DAY. LITTLE CHANGE IN ATMOSPHERIC HEIGHTS AND THICKNESS
VALUES PORTEND A CONTINUATION OF UNSEASONABLY WARM DAYS...WITH
DESERT HIGHS POTENTIALLY HITTING THE 110 DEGREE MARK THROUGH
THURSDAY. HOWEVER...HIGH TEMPERATURE VARIABILITY WILL OF COURSE
RESULT FROM NEARBY CLOUD AND SHOWER DEVELOPMENT.
&&
.AVIATION...
SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA AND KSDL...
STORM ACTIVITY OVER THE LOWER DESERTS IS WINDING DOWN THIS EVENING.
SPOTTY LIGHT SHOWERS AND ISOLATED THUNDERSTORMS WILL REMAIN A
POSSIBILITY DURING THE OVERNIGHT HOURS AS AN UPPER LEVEL WAVE
APPROACHES FROM BAJA MEXICO BUT NOT ENOUGH TO PUT PREVAILING SHOWERS
OR TEMPO SHWRS IN THE TAFS. SURFACE WINDS WILL BE VARIABLE ACROSS
THE METRO AREA OVERNIGHT BEFORE SLOWLY TRENDING TO WESTERLY
DIRECTIONS MONDAY AFTERNOON. DEBRIS CLOUDS WILL DECREASE TOWARD
MORNING.
SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH...
CLOUDINESS WILL INCREASE OVERNIGHT...MAINLY ABOVE 10 KFT MSL...AHEAD
OF AN APPROACHING UPPER LEVEL WAVE CURRENTLY NEAR BAJA MEXICO.
ISOLATED SHWRS/TSTMS WILL BE POSSIBLE OVER THE REGION BUT
PROBABILITY TO LOW TO SHOW PREVAILING OR TEMPO SHWRS/TSTMS IN THE
TAFS. SURFACE WINDS WILL FAVOR SOUTHERLY DIRECTIONS THROUGH THE DAY
MONDAY.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
THROUGH MIDWEEK...STRONG RIDGING ALOFT OVER THE DESERT SOUTHWEST
WILL KEEP TEMPERATURES ABOVE NORMAL...AND MONSOON THUNDERSTORM
ACTIVITY CONFINED MAINLY TO THE HIGHER TERRAIN OF SOUTH-CENTRAL
ARIZONA WITH ISOLATED THUNDERSTORMS POSSIBLE OVER THE DESERTS OF
SOUTH-CENTRAL ARIZONA. A DEEPER MONSOON MOISTURE PROFILE IS EXPECTED
TO WORK BACK INTO THE REGION LATER IN THE WEEK AS THE RIDGING
WEAKENS AND SOUTHERLY FLOW ALOFT STRENGTHENS...HELPING INCREASE
THUNDERSTORM ACTIVITY WHILE ALSO ALLOWING FOR COOLER TEMPERATURES.
MINIMUM HUMIDITIES WILL GENERALLY REMAIN IN THE TEENS ACROSS THE
LOWER DESERTS...AND IN THE 20-30 PERCENT RANGE ACROSS THE HIGHER
TERRAIN...WITH GOOD TO EXCELLENT OVERNIGHT RECOVERIES THROUGH THE
PERIOD. WINDS TO REMAIN MAINLY ON THE LIGHT SIDE...WITH THE USUAL
DIURNAL TRENDS IN DIRECTION AND SPEED...EXCEPT NEAR THUNDERSTORMS.
$$
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...EXCESSIVE HEAT WARNING ACROSS THE SOUTH CENTRAL DESERTS...
AZZ022...AZ023...AZZ027...AZZ028...THROUGH 5 AM MONDAY.
CA...NONE.
&&
$$
VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX
DISCUSSION...AJ
PREVIOUS DISCUSSION...VASQUEZ
AVIATION...AJ
FIRE WEATHER...CB/NOLTE
AREA FORECAST DISCUSSION
NWS SAN JOAQUIN VALLEY - HANFORD CA
309 PM PDT MON AUG 19 2013
.SYNOPSIS...
A LOW PRESSURE CENTER OFF THE CENTRAL COAST WILL BRING A CHANCE OF
MAINLY AFTERNOON AND EVENING THUNDERSTORMS OVER THE SIERRA NEVADA
THROUGH WEDNESDAY. THERE WILL ALSO BE A SLIGHT CHANCE OF
THUNDERSHOWERS FOR THE SAN JOAQUIN VALLEY THROUGH TUESDAY MORNING.
THE LOW WILL LIFT NORTHEAST OUT OF THE REGION BY THURSDAY AND BRING
A RETURN OF DRIER WEATHER FOR THE END OF THE WEEK.
&&
.DISCUSSION...
UPPER LOW OFF THE COAST IN CONJUNCTION WITH LARGE SCALE UPPER
RIDGE OVER THE FOUR CORNERS IS PROVIDING A SQUEEZE PLAY TO STREAM
MID LEVEL SUB TROPICAL MOISTURE INTO THE CENTRAL CA INTERIOR.
T-STORMS ARE ONCE AGAIN FIRING UP OVER THE SIERRA AND ALONG THE
TEHACHAPI RANGE ATTM. UPSLOPE CONDITIONS IN ASSOCIATION WITH
MODERATE MUCAPES FROM THE VEGAS SOUNDING OF OVER 2000 J/KG ARE
PROVIDING ENOUGH LIFT TO GET IT GOING AGAIN TODAY. BLENDED PWAT
VALUES OF 1.0-1.5 ARE OVER THE REGION WILL PROVIDE ENOUGH MOISTURE
TO SUPPORT THUNDERSTORMS. ACTIVE PATTERN WILL CONTINUE INTO THE
OVERNIGHT HOURS AS UPPER LOW REMAINS STATIONARY OFF THE COAST AND
MOISTURE FEED CONTINUES.
19Z RUN OF THE HRRR IS PAINTING MOST OF THE CWA WITH QPF FOR THIS
EVENING. EVEN SPREADS QPF INTO THE VALLEY AND OVER TO THE WEST
SIDE OF THE SJV. SOME FLASH FLOODING IS POSSIBLE WITH THE STORMS
IN THE MOUNTAINS AS MOVEMENT IS ONLY AROUND 10 MPH. ADDITIONAL
FIRE STARTS ARE ALSO POSSIBLE WITH NUMEROUS LIGHTNING STROKES
ASSOCIATED THE STORMS.
THE UPPER LOW BEGINS TO OPEN UP AND LIFT NE. BOTH THE MEAN
ENSEMBLE GFS AND THE 12Z OPERATIONAL ECM ARE IN DECENT AGREEMENT
WITH LIFTING THE FEATURE NE BY WED AND SW FLOW ALOFT SETTING UP
WITH DRIER CONDITIONS. EPAC TROUGH WILL DIG SOUTH AND FEED ANOTHER
ROUND OF SUB TROPICAL MOISTURE INTO THE REGION. HAVE INTRODUCED
POPS FOR SUNDAY AND MONDAY OVER THE SIERRA AND OVER THE
TEHACHAPIS.
&&
.AVIATION...
SCATTERED SHOWERS AND THUNDERSTORMS WITH LOCAL MVFR/IFR CONDITIONS
EXPECTED TODAY...MAINLY OVER THE MOUNTAINS AND DESERT. OTHERWISE...
VFR CONDITIONS WILL PREVAIL THROUGHOUT THE CENTRAL CALIFORNIA
INTERIOR DURING THE NEXT 24 HOURS.
&&
.AIR QUALITY ISSUES...
ON MONDAY AUGUST 19 2013... UNHEALTHY FOR SENSITIVE GROUPS IN
SEQUOIA NATIONAL PARK AND FOREST.
FURTHER INFORMATION IS AVAILABLE AT VALLEYAIR.ORG
&&
.CERTAINTY...
THE LEVEL OF CERTAINTY FOR DAYS 1 AND 2 IS MEDIUM.
THE LEVEL OF CERTAINTY FOR DAYS 3 THROUGH 7 IS HIGH.
THIS INFORMATION IS PROVIDED AS PART OF A TRIAL PROJECT CONDUCTED
BY THE NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD.
CERTAINTY LEVELS INCLUDE LOW...MEDIUM...AND HIGH. PLEASE VISIT
WWW.WEATHER.GOV/HNX/CERTAINTY.PHP /ALL LOWER CASE/ FOR ADDITIONAL
INFORMATION AND/OR TO PROVIDE FEEDBACK.
&&
.CLIMATE...
RECORDS
SITE DATE HI_MAX:YEAR LO_MAX:YEAR HI_MIN:YEAR LO_MIN:YEAR
KFAT 08-19 108:1892 67:1976 74:2012 54:1916
KFAT 08-20 108:1919 76:1959 75:1986 54:1974
KFAT 08-21 108:1919 80:1968 76:1913 51:1959
KBFL 08-19 109:1950 78:1959 79:1961 52:1913
KBFL 08-20 112:1950 77:1959 79:1950 52:1912
KBFL 08-21 110:1919 80:1968 77:1982 51:1918
&&
.HNX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
PUBLIC...JDB
AVN/FW...MV
SYNOPSIS...ANDERSEN
WEATHER.GOV/HANFORD
AREA FORECAST DISCUSSION
NWS SACRAMENTO CA
1030 AM PDT MON AUG 19 2013
.SYNOPSIS...
CHANCE OF THUNDERSTORMS INTO THURSDAY AS A LOW PRESSURE SYSTEM
ALONG THE CENTRAL COAST GRADUALLY MOVES THROUGH NORTHERN
CALIFORNIA. HOT WEATHER WILL CONTINUE TODAY FOLLOWED BY A RETURN
TO NEAR SEASONAL TEMPERATURES BY MID-WEEK.
&&
.DISCUSSION...
UPPER LEVEL LOW PRESSURE OFF THE COAST HAS DROPPED FURTHER TO SOUTH
AND WEST. THIS SYSTEM IS PUMPING SIGNIFICANT MOISTURE INTO THE
AREA. THE OAKLAND MORNING SOUNDING SHOWS THIS WITH PRECIPITABLE
WATER AT OAKLAND AROUND 200 PERCENT OF NORMAL. SATELLITE SHOWS CLOUDS
WRAPPING AROUND AND STREAMING WESTWARD THROUGH THE VALLEY,
CURRENTLY EXTENDING NORTH AND SOUTH BETWEEN RED BLUFF AND GALT.
THIS IS BRINGING OVERCAST SKIES TO THAT AREA. RADAR ALSO SHOWS
SOME EMBEDDED RETURNS WITH PERHAPS SOME SPRINKLES IN THE VALLEY OR
A FEW LIGHT RAIN SHOWERS THE MOUNTAINS AND FOOTHILLS. MESOSCALE
MODELS SHOW MORE SIGNIFICANT PRECIPITATION SPREADING INTO THE
MOUNTAINS BY THIS AFTERNOON. THE WRF EXTENDS SOME SHOWERS AND
THUNDERSTORMS INTO THE NORTHERN AND PORTIONS OF THE CENTRAL
SACRAMENTO VALLEY BY LATE AFTERNOON AND AM FORECASTING SCATTERED
STORMS FOR THAT AREA. THE HRRR KEEPS MOST OF THE CONVECTION OVER
HIGHER TERRAIN...THOUGH. THIS MAY BE DUE TO RELATIVELY DRY AIR
NEAR THE SURFACE, WHICH IS EVIDENT IN AIRCRAFT SOUNDINGS THIS
MORNING. THE SOUTHERN VALLEY LOOKS LIKE IT HAS LESS CHANCE OF
ACTIVITY ALTHOUGH WILL KEEP SOME ISOLATED SHOWERS AND
THUNDERSTORMS THERE FOR THIS EVENING. OVERALL, THE STRONGEST
THUNDERSTORM ACTIVITY IS EXPECTED TO BE OVER THE SIERRA AND
MOUNTAINS OF WESTERN PLUMAS COUNTY AND DOWN INTO THE FOOTHILLS
WITH LOCALLY HEAVY RAIN AND SIGNIFICANT AMOUNTS OF CLOUD TO GROUND
LIGHTNING POSSIBLE. RED FLAG WARNING CONTINUES FOR THE THREAT OF
WILDFIRE STARTS DUE TO LIGHTNING. LIGHTNING STRIKES
YESTERDAY/OVERNIGHT WERE REPORTED TO HAVE STARTED SOME FIRES.
A VERY WARM START TO THE DAY TODAY WITH SOME LOCATIONS OVER THE
NORTHERN SACRAMENTO VALLEY AND FOOTHILLS ONLY DROPPING TO THE
UPPER 70S TO LOWER 80S. A LACK OF A DELTA BREEZE ALSO CONTRIBUTED
TO THIS. HIGH TEMPERATURES TODAY COULD BE TRICKY AS CLOUDS MAY ACT
TO LIMIT SOLAR HEATING. MAY NEED TO MAKE SOME ADJUSTMENTS TO
AFTERNOON HIGHS.
MORE WIDESPREAD CONVECTION IS EXPECTED ON TUESDAY AS THE LOW
BEGINS TO SLOWLY SHIFT NORTHWARD. EK
&&
.EXTENDED DISCUSSION (FRIDAY THROUGH MONDAY)
SOME CHANGES TO THE FORECAST ON THURSDAY WITH INCREASED CHANCES OF
SHOWERS AND THUNDERSTORMS OVER THE NORTHERN MOUNTAINS AND
NORTHERN SACRAMENTO VALLEY THROUGH THE DAY AND INTO THE EARLY
EVENING. MODELS HAVE SLOWED DOWN THE DEPARTURE OF THE UPPER LOW
WITH IT LINGERING OVER NORTHERN CALIFORNIA THROUGH THE DAY
THURSDAY. THERE IS FAIRLY GOOD AGREEMENT NOW BETWEEN THE ECMWF,
THE GFS AND THE GEM WITH THE CORE OF THE LOW CENTERED AROUND
SACRAMENTO BY LATE MORNING. CONVECTIVE ACTIVITY SHOULD BE LIMITED
TO THE NORTHERN PORTION OF THE FORECAST AREA WITH DRIER MORE
STABLE MOVING IN TO THE SOUTH. HIGH TEMPERATURES SHOULD BE AROUND
NORMAL LEVELS BUT WILL DEPEND ON THE DEGREE OF CLEARING DURING THE
DAY. THE LOW WILL SHOULD HAVE EXITED THE AREA BY LATE FRIDAY
EVENING.
THIS TIMING SUGGESTS THE LOW SHOULD WEAKEN AND EXIT THE REGION
OVERNIGHT WITH DRY WEATHER FOR FRIDAY AND SATURDAY WITH STABLE
SOUTHWEST FLOW. TEMPERATURES SHOULD BE AT TO A LITTLE BELOW
NORMAL. EK
&&
.AVIATION...
SMOKE IN VICINITY OF WILDFIRES WILL CONTINUE TO CAUSE LOCAL
IFR/MVFR VISIBILITIES SOUTH OF KBLU TO KAUN AND EAST OF KOVE.
OTHERWISE, VFR CONDITIONS WILL PREVAIL ACROSS THE REGION. MAIN
AVIATION CONCERN TODAY WILL BE ISOLATED TO SCATTERED
SHOWER/THUNDERSTORM DEVELOPMENT BOTH IN THE MOUNTAINS AND OVER THE
VALLEY WITH LOCAL MVFR/IFR CONDITIONS ASSOCIATED WITH STORMS.
MOUNTAINS ARE MORE LIKELY TO HAVE SCATTERED COVERAGE OF -SHRA/-TSRA STARTING
AFTER 18Z. VALLEY LOCATIONS WILL INITIALLY JUST HAVE ISOLATED
-SHRA/-TSRA DURING MORNING AND AFTERNOON BUT THEN BECOME SCATTERED
AFTER 00Z, ESPECIALLY NORTH OF I-80. LIGHT WINDS FOR ALL TAF SITES
TODAY AROUND 10-12 KTS OR LESS, HOWEVER, ERRATIC GUSTY WINDS
POSSIBLE IF THUNDERSTORMS DEVELOP. JBB
&&
.STO WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 5 AM PDT THURSDAY NORTHEAST
FOOTHILLS/SACRAMENTO VALLEY...WESTERN PLUMAS COUNTY/LASSEN PARK.
RED FLAG WARNING UNTIL 11 PM PDT WEDNESDAY CLEAR LAKE/SOUTHERN
LAKE COUNTY...MOTHERLODE...MOUNTAINS SOUTHWESTERN SHASTA COUNTY
TO NORTHERN LAKE COUNTY...WEST SLOPE NORTHERN SIERRA NEVADA.
RED FLAG WARNING FROM 2 PM THIS AFTERNOON TO 11 PM PDT WEDNESDAY
CENTRAL SACRAMENTO VALLEY.
RED FLAG WARNING FROM 2 PM THIS AFTERNOON TO 5 AM PDT THURSDAY
BURNEY BASIN / EASTERN SHASTA COUNTY...NORTHERN SACRAMENTO
VALLEY...SHASTA LAKE AREA / NORTHERN SHASTA COUNTY.
&&
$$
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
950 AM PDT MON AUG 19 2013
.SYNOPSIS...
UPPER LEVEL LOW PRESSURE WEST OF POINT CONCEPTION WILL DRAW A
LIMITED AMOUNT OF MID LEVEL MONSOONAL MOISTURE INTO SOUTHERN
CALIFORNIA WITH WIDELY SCATTERED THUNDERSTORMS FOR THE MOUNTAINS AND
DESERTS OF SAN BERNARDINO AND RIVERSIDE COUNTIES THROUGH THIS
EVENING. THE THUNDERSTORMS WILL PRODUCE LIGHTNING STRIKES...LOCALLY
STRONG GUSTY WINDS...AND BRIEF HEAVY RAINFALL. AS THE TROUGH OF LOW
PRESSURE WEAKENS AND MOVES INLAND THROUGH NORTHERN AND CENTRAL
CALIFORNIA...DRIER SOUTHWEST FLOW ALOFT AND STRONGER ONSHORE FLOW
WILL FOLLOW FOR TUESDAY AND WEDNESDAY...WEAKENING LATE IN THE WEEK.
A GREATER INFLUX OF MONSOONAL MOISTURE IS POSSIBLE FOR NEXT WEEKEND
THROUGH EARLY NEXT WEEK.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
REMAINDER OF TODAY THROUGH THIS EVENING...
MOST OF SAN BERNARDINO COUNTY HAD NATURES ALARM CLOCK GO OFF THIS
MORNING WITH THUNDERSTORMS BEGINNING SHORTLY BEFORE 0400 PDT AND
CONTINUING UP UNTIL 0830 PDT. THE 19/12Z ANALYSES SHOWED THE LOW IS
VERTICALLY STACKED AND CLOSED FROM 925 MB UP TO 200 MB. THIS WOULD
ARGUE FOR A BAROTROPIC MODEL SOLUTION AND THE ONLY AVAILABLE MODELS
AT THE FIELD OFFICE LEVEL ARE ALL BAROCLINIC. THOUGH THESE ARE SLOW
IN MOVING THE LOW OUT TO THE NORTHEAST...2 KTS/LESS THAN 3
MPH...THEY MAY STILL BE TOO FAST. PLAN TO USE HRRR MODEL AS MODEL OF
CHOICE FOR FIRST/SECOND PERIODS. ALREADY DID SOME QUICK
MODIFICATIONS TO THE GRIDS AND ISSUED UPDATES TO THE ZONE FORECAST
PRODUCTS.
REMAINDER OF TONIGHT INTO WEDNESDAY...
NO CHANGES ANTICIPATED TO CURRENT GRIDS/FORECAST AS THEY AGREE WITH
LATEST GUIDANCE...ASSUMING THESE BAROCLINIC MODELS ARE NOT TOO FAST
ON DRYING OUT AIR MASS.
THURSDAY THROUGH SUNDAY...FROM EARLY MORNING DISCUSSION...
A TROUGH OF LOW PRESSURE WILL DEVELOP OVER THE EASTERN PACIFIC. THIS
MAY DRAW INCREASING MONSOONAL MOISTURE INTO SOUTHERN CALIFORNIA FOR
NEXT WEEKEND INTO EARLY NEXT WEEK WITH SOME CONTINUING MODEL TO
MODEL AND RUN TO RUN DIFFERENCES WITH THE DETAILS AND DEGREE OF THE
POSSIBLE MOISTURE INFLUX. THE CURRENT FORECAST NOW SHOWS SLOWLY
INCREASING POPS FOR THE MOUNTAINS AND DESERTS FOR SATURDAY THROUGH
EARLY NEXT WEEK.
&&
.HYDROLOGY...
FLASH FLOOD THREAT IS LOW TO MODERATE...GROUND BASED GPS
PRECIPITABLE WATER SENSORS ACROSS SW CALIFORNIA SHOW AMOUNTS RANGING
FROM 1.2 INCHES WEST OF THE MOUNTAINS TO 1.6 INCHES OVER THE
MOUNTAINS AND DESERTS. HOWEVER ONLY ONE STATION REPORTED ANY
SIGNIFICANT RAIN EARLY THIS MORNING...HEAPS PEAK ON THE FRONT RANGE
OF THE SAN BERNARDINO MOUNTAINS WITH 0.25 INCHES RAINFALL. ALTHOUGH
RAINSHAFTS WERE OBSERVED OVER THE HIGH DESERTS...RAINFALL AMOUNTS
THERE AS WELL AS ELSEWHERE HAVE GENERALLY BEEN LESS THAN 0.10
INCHES. THESE LOW NUMBERS PROBABLY DUE TO THE TRANSPORT
WINDS...SOUTHEAST WINDS 15-25 MPH IN THE LOWER 15000 FEET...WHICH
DOES NOT ALLOW THE CELLS TO STICK AROUND LONG ENOUGH TO DUMP MUCH
MORE THAN WHAT HAS BEEN OBSERVED SO FAR. STILL HAVE TO WORRY ABOUT
TRAINING OF CELLS AKA SEVERAL CYCLES OF THUNDERSTORMS MOVING ACROSS
THE SAME AREA UNTIL EARLY EVENING HOURS TONIGHT...IF THIS DEVELOPS
WOULD LIKELY PRODUCE FLASH FLOODING EAST/SOUTHEAST SLOPES OF
MOUNTAINS WITH RUNOFF DOWN INTO DESERT VALLEY FLOORS. JUST MODIFIED
THE 11AM THROUGH 11 PM GRIDS TO REFLECT MORE WIDESPREAD
THUNDERSTORMS AND A LITTLE MORE RAIN. EVEN SO...STILL
UNDERFORECASTING SREF POPS BY HALF SO THAT SGX GRIDS DO NOT CLASH
TOO MUCH WITH NEIGHBORING OFFICES. WILL PROBABLY TWEAK A LITTLE MORE
LATER THIS MORNING AND ISSUE ANOTHER QPS/UPDATED ESF.
&&
.AVIATION...
191457Z...COAST/VALLEYS...STRATUS ABOUT 20 SM INLAND...WITH BASES
800-1200 FT MSL AND TOPS 1600-1800 FT MSL...WILL SLOWLY CLEAR TO THE
COAST THROUGH 1900 UTC. 1900-20/0100 UTC...UNRESTRICTED VIS WITH
SCT-FEW CLDS AOA 9000 FT MSL...IN ADDITION TO SCT-BKN CLDS 1200-1500
FT MSL LINGERING WITHIN 5 SM OF THE COAST...POSSIBLY IMPACTING
KSAN...KCRQ AND KSNA WITH BKN CIGS AT TIMES. 20/0100-0700
UTC...STRATUS MOVING BACK INLAND...EVENTUALLY REACHING 20 SM INLAND
BY 20/1400 UTC...WITH BASES AND TOPS SIMILAR TO THIS MORNING.
MTNS/DESERTS...ISOLATED SHOWERS/TSTMS OVER WESTERN SAN BERNARDINO
COUNTY WILL TAPER OFF THROUGH 1700 UTC. HOWEVER...THERE IS ANOTHER
CHANCE OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING OVER
THE RIVERSIDE AND SAN BERNARDINO MTNS AND HIGH DESERTS WITH BASES
NEAR 9000 FT MSL AND TOPS TO 35000 FT MSL. THESE STORMS MAY PRODUCE
SMALL HAIL...STRONG UPDRAFTS...2-5SM VIS IN HEAVY RAIN...AND LOCAL
GUSTY SFC WINDS TO 40 KT. OTHERWISE...SCT-BKN CLDS AOA 9000 FT MSL
AND UNRESTRICTED VIS THROUGH TUESDAY MORNING.
&&
.MARINE...
ASTRONOMICAL HIGH TIDES OF 7 FEET OR GREATER WILL OCCUR DURING THE
EVENINGS THROUGH TUESDAY...INCLUDING A PEAK OF 7.2 FEET THIS
EVENING. SOME VULNERABLE LOW-LYING AREAS ALONG THE COAST MAY
EXPERIENCE SOME MINOR TIDAL OVERFLOW DURING TIMES OF HIGHEST TIDE.
&&
.FIRE WEATHER...
LOT OF DRY LIGHTNING BETWEEN 0400 AND 0800 PDT THIS MORNING...A
CONSERVATIVE COUNT OF 500 STRIKES DURING THIS TIME PERIOD WITH AT
LEAST 9 LIGHTNING STARTED FIRES ON THE SAN BERNARDINO NATIONAL
FOREST. WITH EXCEPTION OF HEAPS PEAK...STATIONS WITH NEARBY
LIGHTNING REPORTED NO RAINFALL OR AMOUNTS LESS THAN 0.10 INCHES.
EXPECT A TEMPORARY BREAK IN THUNDERSTORM ACTIVITY UNTIL 1100 PDT
THEN SCATTERED THUNDERSTORMS OVER MOUNTAINS AND DESERTS...MOVING
NORTH NORTHWEST AROUND 15 MPH. MOST OF THESE SHOULD BE A MIXTURE OF
WET AND DRY...HAVE LAL OF 3 AND 4 FOR REMAINDER OF TODAY/THIS
EVENING. STILL NO WIDESPREAD SIGNIFICANT RAINFALL AMOUNTS EXPECTED
DUE TO SPEED OF MOVEMENT AND DRY LAYER FROM BELOW THUNDERSTORM BASES
AND TOP OF ANY MARINE AIR INFLUENCE...ROUGHLY 10,000 FT TO 2000 FT
MSL....WHICH PRETTY MUCH COVERS ALL OF THE MOUNTAINS AND DESERTS.
FOR TUESDAY AND WEDNESDAY...THE LOW IS MOVING EVER SO SLOWLY TOWARDS
THE NORTHEAST...ASSUMING THE MODELS ARE CORRECT AND IT`S STILL NOT
SITTING IN THE SAME POSITIONS OR FURTHER SOUTH. SO BASED ON MODEL
MOVEMENT SOUTHWEST CALIFORNIA SHOULD BE UNDER MORE STABLE AND
SOMEWHAT DRIER AIRMASS AND PREVAILING SOUTHWEST FLOW. PERHAPS NO
NEW FIRE STARTS BUT A DRIER AND POTENTIALLY BREEZIER PATTERN WOULD
FAN TO LIFE ANY SLEEPERS AND INCREASE FIRE ACTIVITY ACROSS ONGOING
FIRES.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
$$
PUBLIC/FIRE WEATHER...BALFOUR
AVIATION/MARINE...HARRISON
SHORT TERM WARNINGS/STATEMENTS...HARRISON/JJT
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATED
NWS LOS ANGELES/OXNARD CA
1100 PM PDT SUN AUG 18 2013
.SYNOPSIS...
A SLIGHT CHANCE FOR THUNDERSTORMS ARE POSSIBLE IN THE SAN GABRIEL
MOUNTAINS AND ANTELOPE VALLEY AGAIN TOMORROW...WITH THE UPPER LOW
OFF THE CALIFORNIA COAST CONTINUING TO PULL SOME MONSOON MOISTURE
INTO THE AREA FROM THE SOUTHEAST. THE UPPER LOW WILL BEGIN TO LIFT
NORTHEAST ON THURSDAY...BUT WILL BE REPLACED BY ANOTHER TROUGH OF
LOW PRESSURE MOVING IN FROM THE NORTHWEST. THE RESULT WILL BE
CONTINUED NEAR OR SLIGHTLY BELOW NORMAL TEMPERATURES AND NIGHT
THROUGH MORNING LOW CLOUDS ALONG THE COAST.
&&
.SHORT TERM (TODAY-WED)...
A FEW VERY IMPRESSIVE THUNDERSTORMS DEVELOPED ACROSS THE NORTHEAST
PORTION OF LOS ANGELES COUNTY THIS AFTERNOON...MAINLY NORTH AND EAST
OF PALMDALE TODAY. A COUPLE STORM CELLS WERE RIGHT ON THE LOS
ANGELES...SAN BERNARDINO AND KERN COUNTY BORDER. CLOUD TOPS WERE AS
HIGH AS 45000 FT WITH VERY IMPRESSIVE RAIN AND HAIL CORES. LATEST
NWS RADAR WAS SHOWING MOST OF THE CONVECTIVE ACTIVITY OCCURRING IN
THE EASTERN PART OF SAN BERNARDINO COUNTY AND NORTH INTO KERN COUNTY
OVER THE LAST HOUR AND LIKELY SETTLING DOWN OVER OUR AREA. MANY
PARAMETERS CAME TOGETHER THIS AFTERNOON TO CAUSE THESE EXPLOSIVE
THUNDERSTORMS. ALTHOUGH PRECIPITABLE WATERS (PWAT) VALUES WERE NOT
THAT IMPRESSIVE AROUND 1.20" AND BEST MID LEVEL MOISTURE WAS ABOVE
600 MB (ABOVE 12000 FT). THE INSTABILITY LOOKED VERY IMPRESSIVE BY
MID MORNING AS RAP SOUNDINGS OVER THE MOUNTAINS INDICATED CAPE
VALUES WELL OVER 1000 J/KG. SINCE STORMS WERE ABLE TO
INITIATE...THEY HAD NO PROBLEM GROWING VERTICALLY. RADAR RETURNS
INDICATED VERY HIGH VIL (VERTICAL INTEGRATED LIQUID) AVAILABLE WITH
THE STORM WHICH WAS A GOOD REASON WHY THERE WAS NICKEL SIZE HAIL
REPORTED IN SOME HIGH DESERT LOCATIONS THIS AFTERNOON.
BY LOOKING AT THE WATER VAPOR IMAGERY...IT IS EASY TO SPOT THE
DIFFLUENT REGION OVER EASTERN LA COUNTY AND POINTS EAST AND NORTH
BASED ON WHERE THE UPPER LOW WAS SITUATED TO HELP LIFT THESE STORMS
AND EXPLODE LIKE THEY DID. THERE WAS AN IMPRESSIVE LANDSPOUT SPOTTED
NEAR HELENDALE WHICH IS NORTH OF VICTORVILLE IN SAN BERNARDINO
COUNTY. AS THE UPPER LOW BEGINS TO PIVOT FARTHER OFFSHORE THIS
EVENING...THERE LOOKS TO BE SOME POTENTIAL FOR A FEW NOCTURNAL
SHOWERS OVER THE COASTAL WATERS N OF POINT CONCEPTION. I DID ADD
SLIGHT CHANCE FOR THUNDERSTORMS FOR AREAS N OF POINT CONCEPTION FROM
THE COAST TO SLO INTERIOR VALLEYS AFTER MIDNIGHT THROUGH THE
OVERNIGHT HOURS...BUT NOT VERY CONFIDENT. AS FAR AS THE LOWER AND
MORE STABLE PART OF THE ATMOSPHERE...(THE MARINE LAYER) WAS AROUND
1000 FT DEEP EARLY THIS EVENING...WHICH IS A BIT DEEPER THEN LAST
NIGHT. WITH THE UPPER LOW JUST OFF THE CENTRAL COAST...THERE WILL BE
A SLIGHT DEEPENING OF THE MARINE LAYER WHICH WILL ALLOW FOR SOME LOW
CLOUDS TO CREEP INTO THE SAN GABRIEL AND POSSIBLY THE SAN FERNANDO
VALLEY AFTER MIDNIGHT. TODAY`S HIGH TEMPS WERE OVERALL A TAD
LOWER...BUT A FEW INTERIOR AREAS WERE AROUND THE SAME AS YESTERDAY.
LONG BEACH WAS MUCH COOLER TODAY AT ONLY 74 COMPARED TO 86 ON
SATURDAY DUE TO A PERSISTENT SOUTHERLY FLOW AND LOW CLOUDS HANGING
AROUND.
FOR MONDAY...NOT MUCH MOVEMENT IS EXPECTED WITH CUTOFF LOW...BUT
THERE WILL CONTINUE TO BE SOME MODEST MID LEVEL MOISTURE ADVECTING
NORTH OVER EASTERN LA COUNTY AND AREAS TO THE EAST. BOTH THE NAM-WRF
AND GFS ARE INDICATING MORE INSTABILITY OVER THE LA COUNTY
MOUNTAINS...HAVE ADDED A SLIGHT CHANCE OF THUNDERSTORMS FOR THE
EASTERN PORTION OF THE SAN GABRIEL VALLEY AND ANTELOPE VALLEY ONCE
AGAIN. THERE WILL BE LESS MOISTURE TO WORK WITH...BUT A SLIGHT
CHANCE SEEMS REASONABLE FOR TOMORROW AFTERNOON AND EARLY EVENING. AT
THE LEAST EXPECT PARTLY CLOUDY SKIES WITH SOME CUMULUS BUILDUPS IN
THE MOUNTAINS AND OVER THE ANTELOPE VALLEY. LOOK FOR A MODEST
COOLING TREND FOR TOMORROW AS THE UPPER RIDGE WEAKENS A
BIT...ESPECIALLY ACROSS THE NORTHERN PORTION OF THE FORECAST AREA N
OF POINT CONCEPTION. THERE WILL LIKELY BE SOME HIGH CLOUDS MOVING
TO THE NORTH ACROSS THE SKY...BUT WILL CONTINUE WITH MOSTLY SUNNY
SKIES. THE MID SHIFT CAN ADJUST IF NEED BE.
***FROM PREVIOUS DISCUSSION***
VERY LITTLE CHANGE TUE/WED. POSSIBLY SOME HIGH CLOUDS MOVING THROUGH
AT TIMES TUESDAY AS MOISTURE WRAPS AROUND THE STILL STATIONARY UPPER
LOW. BUT AT THIS TIME NOT SEEING ANYTHING TO WARRANT POPS OR EVEN
PARTLY CLOUDY SKIES. DAYTIME HIGHS EXPECTED TO CHANGE LITTLE.
.LONG TERM (THU-SUN)...UPPER LOW FINALLY EXITING THE STATE ON
THURSDAY TO BE REPLACED BY A WEAK TROF THROUGH THE WEEKEND. THE
ECMWF IS DEEPER WITH THE TROF AND THUS COOLER AS WELL. FOR NOW WILL
JUST INDICATE LITTLE CHANGE THROUGH THE PERIOD WITH HIGHS NEAR TO
SLIGHTLY BELOW SEASONAL NORMS. ALL MODEL SOLUTIONS KEEP MONSOON
MOISTURE WELL EAST INTO EARLY NEXT WEEK.
&&
.AVIATION...
19/0600Z.
VERY LOW CONFIDENCE FORECAST OVERNIGHT AS A GUST FRONT FROM THE
DESERT CONVECTION COULD WREAK HAVOC WITH THE MARINE LAYER. THERE IS
A SLIGHT CHC OF TSTMS OVER THE DESERT AND MTNS AS WELL AS ALL OF SLO
COUNTY OVERNIGHT.
KLAX...LOW CONFIDENCE IN TAF THERE IS A 30 PERCENT CHANCE OF A BRIEF
EAST WIND ALONG WITH A TOTAL DISRUPTION OF THE MARINE LAYER.
KBUR...LOW CONFIDENCE IN TAF THERE IS A 40 PERCENT CHANCE OF LIFR
CIGS 13Z-16Z.
&&
.FIRE...
A CUTOFF LOW PRESSURE SYSTEM OFF THE CENTRAL COAST WILL REMAIN
NEARLY STATIONARY THROUGH TUESDAY. THIS LOW PRESSURE SYSTEM IS
DRAWING SOME MOISTURE INTO SOUTHERN AND CENTRAL CALIFORNIA. AT THE
PRESENT TIME...THE MOISTURE AXIS IS FOCUSED ACROSS EASTERN LOS
ANGELES COUNTY AND POINTS EASTWARD. THIS INFLUX OF MOISTURE COMBINED
WITH AN UNSTABLE AIR MASS WILL CONTINUE TO GENERATE ISOLATED
THUNDERSTORMS ACROSS THE EASTERN PORTIONS OF THE SAN GABRIEL
MOUNTAINS AND ANTELOPE VALLEY THROUGH THIS EVENING. THESE STORMS
WILL HAVE THE POTENTIAL TO PRODUCE STRONG DOWNDRAFT
WINDS...HAIL...AND BRIEF HEAVY DOWNPOURS. AROUND THE PERIPHERY OF
STORMS...ISOLATED DRY LIGHTNING STRIKES WILL BE POSSIBLE. CLOSER TO
THE CLOSED LOW...THERE IS A VERY SLIGHT CHANCE OF STORMS TONIGHT
INTO MONDAY FOR AREAS NORTH OF POINT CONCEPTION.
THE LOW PRESSURE SYSTEM WILL BRING GUSTY SOUTHERLY WINDS TO INTERIOR
SECTIONS THROUGH MONDAY. WITH THE EXCEPTION OF EASTERN LOS ANGELES
COUNTY...REMAINING AREAS ARE FORECASTED TO BE QUITE DRY AT LOWER
ELEVATIONS. THIS COMBINATION OF GUSTY SOUTHERLY WINDS...LOW
HUMIDITIES...VERY WARM TEMPERATURES...AND VERY DRY FUELS WILL
CONTINUE TO BRING ELEVATED FIRE DANGER ACROSS INLAND AREAS THROUGH
MONDAY. BRIEF CRITICAL FIRE WEATHER CONDITIONS WILL BE LIKELY
THROUGH MONDAY ACROSS THE MOUNTAINS.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
PUBLIC...KAPLAN/MW
FIRE...GOMBERG
AVIATION...ASR
SYNOPSIS...SUKUP
WWW.WEATHER.GOV/LOSANGELES
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATED
NWS LOS ANGELES/OXNARD CA
815 PM PDT SUN AUG 18 2013
.SYNOPSIS...
A SLIGHT CHANCE FOR THUNDERSTORMS ARE POSSIBLE IN THE SAN GABRIEL
MOUNTAINS AND ANTELOPE VALLEY AGAIN TOMORROW...WITH THE UPPER LOW
OFF THE CALIFORNIA COAST CONTINUING TO PULL SOME MONSOON MOISTURE
INTO THE AREA FROM THE SOUTHEAST. THE UPPER LOW WILL BEGIN TO LIFT
NORTHEAST ON THURSDAY...BUT WILL BE REPLACED BY ANOTHER TROUGH OF
LOW PRESSURE MOVING IN FROM THE NORTHWEST. THE RESULT WILL BE
CONTINUED NEAR OR SLIGHTLY BELOW NORMAL TEMPERATURES AND NIGHT
THROUGH MORNING LOW CLOUDS ALONG THE COAST.
&&
.SHORT TERM (TODAY-WED)...
A FEW VERY IMPRESSIVE THUNDERSTORMS DEVELOPED ACROSS THE NORTHEAST
PORTION OF LOS ANGELES COUNTY THIS AFTERNOON...MAINLY NORTH AND EAST
OF PALMDALE TODAY. A COUPLE STORM CELLS WERE RIGHT ON THE LOS
ANGELES...SAN BERNARDINO AND KERN COUNTY BORDER. CLOUD TOPS WERE AS
HIGH AS 45000 FT WITH VERY IMPRESSIVE RAIN AND HAIL CORES. LATEST
NWS RADAR WAS SHOWING MOST OF THE CONVECTIVE ACTIVITY OCCURRING IN
THE EASTERN PART OF SAN BERNARDINO COUNTY AND NORTH INTO KERN COUNTY
OVER THE LAST HOUR AND LIKELY SETTLING DOWN OVER OUR AREA. MANY
PARAMETERS CAME TOGETHER THIS AFTERNOON TO CAUSE THESE EXPLOSIVE
THUNDERSTORMS. ALTHOUGH PRECIPITABLE WATERS (PWAT) VALUES WERE NOT
THAT IMPRESSIVE AROUND 1.20" AND BEST MID LEVEL MOISTURE WAS ABOVE
600 MB (ABOVE 12000 FT). THE INSTABILITY LOOKED VERY IMPRESSIVE BY
MID MORNING AS RAP SOUNDINGS OVER THE MOUNTAINS INDICATED CAPE
VALUES WELL OVER 1000 J/KG. SINCE STORMS WERE ABLE TO
INITIATE...THEY HAD NO PROBLEM GROWING VERTICALLY. RADAR RETURNS
INDICATED VERY HIGH VIL (VERTICAL INTEGRATED LIQUID) AVAILABLE WITH
THE STORM WHICH WAS A GOOD REASON WHY THERE WAS NICKEL SIZE HAIL
REPORTED IN SOME HIGH DESERT LOCATIONS THIS AFTERNOON.
BY LOOKING AT THE WATER VAPOR IMAGERY...IT IS EASY TO SPOT THE
DIFFLUENT REGION OVER EASTERN LA COUNTY AND POINTS EAST AND NORTH
BASED ON WHERE THE UPPER LOW WAS SITUATED TO HELP LIFT THESE STORMS
AND EXPLODE LIKE THEY DID. THERE WAS AN IMPRESSIVE LANDSPOUT SPOTTED
NEAR HELENDALE WHICH IS NORTH OF VICTORVILLE IN SAN BERNARDINO
COUNTY. AS THE UPPER LOW BEGINS TO PIVOT FARTHER OFFSHORE THIS
EVENING...THERE LOOKS TO BE SOME POTENTIAL FOR A FEW NOCTURNAL
SHOWERS OVER THE COASTAL WATERS N OF POINT CONCEPTION. I DID ADD
SLIGHT CHANCE FOR THUNDERSTORMS FOR AREAS N OF POINT CONCEPTION FROM
THE COAST TO SLO INTERIOR VALLEYS AFTER MIDNIGHT THROUGH THE
OVERNIGHT HOURS...BUT NOT VERY CONFIDENT. AS FAR AS THE LOWER AND
MORE STABLE PART OF THE ATMOSPHERE...(THE MARINE LAYER) WAS AROUND
1000 FT DEEP EARLY THIS EVENING...WHICH IS A BIT DEEPER THEN LAST
NIGHT. WITH THE UPPER LOW JUST OFF THE CENTRAL COAST...THERE WILL BE
A SLIGHT DEEPENING OF THE MARINE LAYER WHICH WILL ALLOW FOR SOME LOW
CLOUDS TO CREEP INTO THE SAN GABRIEL AND POSSIBLY THE SAN FERNANDO
VALLEY AFTER MIDNIGHT. TODAY`S HIGH TEMPS WERE OVERALL A TAD
LOWER...BUT A FEW INTERIOR AREAS WERE AROUND THE SAME AS YESTERDAY.
LONG BEACH WAS MUCH COOLER TODAY AT ONLY 74 COMPARED TO 86 ON
SATURDAY DUE TO A PERSISTENT SOUTHERLY FLOW AND LOW CLOUDS HANGING
AROUND.
FOR MONDAY...NOT MUCH MOVEMENT IS EXPECTED WITH CUTOFF LOW...BUT
THERE WILL CONTINUE TO BE SOME MODEST MID LEVEL MOISTURE ADVECTING
NORTH OVER EASTERN LA COUNTY AND AREAS TO THE EAST. BOTH THE NAM-WRF
AND GFS ARE INDICATING MORE INSTABILITY OVER THE LA COUNTY
MOUNTAINS...HAVE ADDED A SLIGHT CHANCE OF THUNDERSTORMS FOR THE
EASTERN PORTION OF THE SAN GABRIEL VALLEY AND ANTELOPE VALLEY ONCE
AGAIN. THERE WILL BE LESS MOISTURE TO WORK WITH...BUT A SLIGHT
CHANCE SEEMS REASONABLE FOR TOMORROW AFTERNOON AND EARLY EVENING. AT
THE LEAST EXPECT PARTLY CLOUDY SKIES WITH SOME CUMULUS BUILDUPS IN
THE MOUNTAINS AND OVER THE ANTELOPE VALLEY. LOOK FOR A MODEST
COOLING TREND FOR TOMORROW AS THE UPPER RIDGE WEAKENS A
BIT...ESPECIALLY ACROSS THE NORTHERN PORTION OF THE FORECAST AREA N
OF POINT CONCEPTION. THERE WILL LIKELY BE SOME HIGH CLOUDS MOVING
TO THE NORTH ACROSS THE SKY...BUT WILL CONTINUE WITH MOSTLY SUNNY
SKIES. THE MID SHIFT CAN ADJUST IF NEED BE.
***FROM PREVIOUS DISCUSSION***
VERY LITTLE CHANGE TUE/WED. POSSIBLY SOME HIGH CLOUDS MOVING THROUGH
AT TIMES TUESDAY AS MOISTURE WRAPS AROUND THE STILL STATIONARY UPPER
LOW. BUT AT THIS TIME NOT SEEING ANYTHING TO WARRANT POPS OR EVEN
PARTLY CLOUDY SKIES. DAYTIME HIGHS EXPECTED TO CHANGE LITTLE.
.LONG TERM (THU-SUN)...UPPER LOW FINALLY EXITING THE STATE ON
THURSDAY TO BE REPLACED BY A WEAK TROF THROUGH THE WEEKEND. THE
ECMWF IS DEEPER WITH THE TROF AND THUS COOLER AS WELL. FOR NOW WILL
JUST INDICATE LITTLE CHANGE THROUGH THE PERIOD WITH HIGHS NEAR TO
SLIGHTLY BELOW SEASONAL NORMS. ALL MODEL SOLUTIONS KEEP MONSOON
MOISTURE WELL EAST INTO EARLY NEXT WEEK.
&&
.FIRE...
A CUTOFF LOW PRESSURE SYSTEM OFF THE CENTRAL COAST WILL REMAIN
NEARLY STATIONARY THROUGH TUESDAY. THIS LOW PRESSURE SYSTEM IS
DRAWING SOME MOISTURE INTO SOUTHERN AND CENTRAL CALIFORNIA. AT THE
PRESENT TIME...THE MOISTURE AXIS IS FOCUSED ACROSS EASTERN LOS
ANGELES COUNTY AND POINTS EASTWARD. THIS INFLUX OF MOISTURE COMBINED
WITH AN UNSTABLE AIR MASS WILL CONTINUE TO GENERATE ISOLATED
THUNDERSTORMS ACROSS THE EASTERN PORTIONS OF THE SAN GABRIEL
MOUNTAINS AND ANTELOPE VALLEY THROUGH THIS EVENING. THESE STORMS
WILL HAVE THE POTENTIAL TO PRODUCE STRONG DOWNDRAFT
WINDS...HAIL...AND BRIEF HEAVY DOWNPOURS. AROUND THE PERIPHERY OF
STORMS...ISOLATED DRY LIGHTNING STRIKES WILL BE POSSIBLE. CLOSER TO
THE CLOSED LOW...THERE IS A VERY SLIGHT CHANCE OF STORMS TONIGHT
INTO MONDAY FOR AREAS NORTH OF POINT CONCEPTION.
THE LOW PRESSURE SYSTEM WILL BRING GUSTY SOUTHERLY WINDS TO INTERIOR
SECTIONS THROUGH MONDAY. WITH THE EXCEPTION OF EASTERN LOS ANGELES
COUNTY...REMAINING AREAS ARE FORECASTED TO BE QUITE DRY AT LOWER
ELEVATIONS. THIS COMBINATION OF GUSTY SOUTHERLY WINDS...LOW
HUMIDITIES...VERY WARM TEMPERATURES...AND VERY DRY FUELS WILL
CONTINUE TO BRING ELEVATED FIRE DANGER ACROSS INLAND AREAS THROUGH
MONDAY. BRIEF CRITICAL FIRE WEATHER CONDITIONS WILL BE LIKELY
THROUGH MONDAY ACROSS THE MOUNTAINS.
&&
.AVIATION...19/00Z.
WILL GO WITH PERSISTENCE ONCE AGAIN IN RESPECT TO STRATUS AND FOG
OVER THE NEXT 24 HOURS. HIGH CONFIDENCE WITH LIFR/IFR CIGS FOR
COASTAL AREAS...WITH SOME VLIFR CONDS FOR A FEW COASTAL SITES.
TIMING FOR LOW CLOUDS WILL BE MODERATE IN CONFIDENCE +/-2 HOURS AS
WELL AS SCOUR OUT TIMES MON MORNING. LATEST AMDAR SOUNDING NEAR KLAX
SHOWED A STRONG INVERSION AROUND 1200 FT DEEP. WITH THE MARINE LAYER
THIS DEEP...THERE WILL BE A 30 PERCENT CHANCE THAT KBUR AND KVNY
WILL EXPERIENCE IFR/LIFR CIGS AFTER 10Z TONIGHT.
KLAX...HIGH CONFIDENCE FOR IFR/MVFR CIGS TO PERSIST THROUGH THE
OVERNIGHT HOURS. 30 PERCENT CHANCE FOR CIGS TO SCOUR OUT +/- W HOURS
FROM 00Z TAF.
KBUR...HIGH CONFIDENCE WITH 00Z TAF THROUGH 10Z. THEN 30 PERCENT
CHANCE FOR LIFR/IFR CIGS AFTER 10Z THROUGH 15Z.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
PUBLIC...KAPLAN/MW
FIRE...GOMBERG
AVIATION...CK
SYNOPSIS...SUKUP
WWW.WEATHER.GOV/LOSANGELES
AREA FORECAST DISCUSSION
NWS GRAND JUNCTION CO
1043 AM MDT MON AUG 19 2013
.UPDATE...
ISSUED AT 1037 AM MDT MON AUG 19 2013
SUNSHINE THIS MORNING WILL PROVIDE GOOD SURFACE HEATING TO START
THE CONVECTIVE CLOUD BUILDUPS OVER THE MTNS BY LATE MORNING. 12Z
MODELS REMAIN HIGHER TERRAIN-CENTRIC WITH THEIR PRECIPITATION
FORECAST THIS AFTERNOON AND EVENING. NOT TOO SURPRISING WITH THE
UPPER RIDGE OVERHEAD AND LIGHT WINDS ALOFT. STORMS THAT DO DEVELOP
THIS AFTERNOON WILL SHOW LITTLE MOVEMENT AND LIKELY COLLAPSE UPON
THEMSELVES FOR THE POTENTIAL OF SOME GUSTY OUTFLOW WINDS AND
ACCENTUATED BY A DRIER SUB-CLOUD LAYER. ONE AREA TO WATCH FOR HEAVY
RAIN POTENTIAL IS SE UT ACROSS THE SW CO. VORTICITY AXIS EXTENDS
ACROSS THIS AREA FROM A WEAK SHORTWAVE MOVING UP THE NV/UT BORDER
AND MAY SERVE AS A BIT OF A FOCUS. THIS ALSO IS AN AXIS OF HIGHER
PRECIPITABLE WATER ESTIMATES OF 0.8 TO 1.0 INCH. WILL ADJUST POPS
UPWARDS A BIT FOR SE UT/SW CO THIS AFTERNOON AS A RESULT.
UPDATE ISSUED AT 830 AM MDT MON AUG 19 2013
QUICK UPDATE TO THE GRIDDED FORECAST TO BETTER REFLECT THE CURRENT
SUNNY/MOSTLY SUNNY CONDITIONS ACROSS MOST OF FORECAST AREA EARLY
THIS MORNING. EXCEPTION IS SOME ALTOCUMULUS CLOUDS OVER SE UT LEFT
OVER FROM LAST NIGHT AND WHERE THE RAP MODEL PUTS A WEAK VORTICITY
MAX. CURRENT FORECAST FOR THIS AFTERNOON SEEMS ON TRACK PER QUICK
LOOK AT THE LATEST RAP/HRRR MODELS.
&&
.SHORT TERM...(TODAY THROUGH TUESDAY)
300 AM MDT MON AUG 19 2013
HIGH PRESSURE WILL REMAIN ANCHORED OVER THE REGION FOR THE NEXT
SEVERAL DAYS. MOISTURE WORKING NORTHWARD WILL BRING ANOTHER ROUND
OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING...WITH THE
FOCUS TODAY GENERALLY SOUTH OF INTERSTATE 70. STORMS WILL
INITIALLY FIRE ALONG THE HIGHER TERRAIN...WITH ACTIVITY DRIFTING
OFF OVER THE VALLEYS LATE THIS AFTERNOON AND EVENING...WITH AN
EMPHASIS ON DRIFT. WINDS ALOFT WILL BE WEAK WITH THE RIDGE
DIRECTLY OVERHEAD AND POTENTIAL FOR LOCALLY HEAVY RAINFALL WILL BE
UP A BIT WITH SLOW STORM MOTIONS. TEMPERATURES WILL BE RUNNING
NEAR SEASONAL NORMS WITH LIGHT WINDS OUTSIDE OF CONVECTIVE GUSTS
TO NEAR 40 MPH WITH THE STRONGER STORMS.
A STRONGER SURGE OF SUBTROPICAL MOISTURE CONTINUES TO WORK INTO
THE GREAT BASIN AND THEN LEAKS EASTWARD INTO TUESDAY FOR AN UPTURN
IN SHOWERS AND THUNDERSTORMS. THE SHEARED ENERGY FROM THE BAJA
DISTURBANCE IS PROGGED TO STAY WELL WEST OF THIS CWA WITH TIME
HEIGHT SECTIONS SHOWING LITTLE ORGANIZED DYNAMICAL LIFT. STILL
PRECIPITABLE WATER VALUES CLIMB TO AN INCH OVER EASTERN UTAH AND
FAR WESTERN COLORADO. BROKEN TO OVERCAST SKIES MAY LIMIT OR DELAY
AFTERNOON HEATING AND INSTABILITY SOMEWHAT. SLOW STORM MOTION WILL
PRODUCE LOCALLY HEAVY RAIN AND POTENTIAL RUNOFF PROBLEMS. A
RELATIVELY DRY NEAR- SURFACE LAYER WILL ALSO ASSIST WITH ENHANCED
LOCAL OUTFLOW WINDS.
.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
300 AM MDT MON AUG 19 2013
BOUNDARY INTERACTION MAY PRODUCE ISOLATED NOCTURNAL CONVECTION
INTO WEDNESDAY MORNING. THE 593 HIGH REBOUNDS WESTWARD BACK TO
NEAR THE FOUR CORNERS. BOTH THE GFS AND NAM ERODE PRECIPITABLE
WATER VALUES SOMEWHAT UNDER THE HIGH. SUBSIDENCE WILL ALSO CAP
LATE DAY CONVECTION A BIT COMPARED TO TUESDAY. STILL ALL MTN
RANGES WILL LIKELY FIRE SOME AFTERNOON STORMS. STORM MOTION
REMAINS SLOW FOR A CONTINUED THREAT OF LOCALLY HEAVY SHOWERS.
MOISTURE WORKING NORTHWARD ALONG THE WESTERN EDGE OF HIGH PRESSURE
CENTERED ACROSS THE CENTRAL PLAINS WILL KEEP CONDITIONS UNSETTLED
AS WE MOVE THROUGH THE WEEK AND INTO THE WEEKEND. HARD TO PIN
POINT ANY INDIVIDUAL WAVE IN THIS PATTERN FOR ENHANCED
POTENTIAL...SO FOR NOW WILL CONTINUE WITH THE BROAD BRUSH APPROACH
OF DAILY CONVECTION...PRIMARILY FOCUSED ON THE AFTERNOON AND
EVENING HOURS. TEMPERATURES WILL BE RUNNING NEAR SEASONAL NORMS
THROUGH THE PERIOD.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1037 AM MDT MON AUG 19 2013
SCATTERED SHOWERS AND THUNDERSTORMS WILL AGAIN DEVELOP ACROSS
EASTERN UTAH AND WESTERN COLORADO THIS AFTERNOON AND EVENING. THE
STORMS WILL BE MOST NUMEROUS SOUTH AND EAST OF A LINE FROM K4HV TO
KEGE...ESPECIALLY BETWEEN 20Z THIS AFTERNOON AND 03Z THIS EVENING.
OUTSIDE OF THIS WINDOW...STORMS WILL BE MORE ISOLATED IN NATURE.
EXPECT BRIEF HEAVY RAIN...SMALL HAIL AND GUSTY OUTFLOW WINDS TO 40
MPH IN THE VICINITY OF SHOWERS WITH BRIEF MOUNTAIN OBSCURATIONS
POSSIBLE. STORMS DISSIPATE AFTER 03Z THIS EVENING WITH VFR CONDS
PREVAILING AT ALL TERMINAL SITES.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.
&&
$$
UPDATE...JAD
SHORT TERM...JDC/JOE
LONG TERM...JOE/JDC
AVIATION...TGJT
AREA FORECAST DISCUSSION
NWS GRAND JUNCTION CO
900 AM MDT MON AUG 19 2013
CORRECTION TO ADD MISSING WORD IN FIRST SENTENCE OF THE UPDATE
.UPDATE...
ISSUED AT 830 AM MDT MON AUG 19 2013
QUICK UPDATE TO THE GRIDDED FORECAST TO BETTER REFLECT THE CURRENT
SUNNY/MOSTLY SUNNY CONDITIONS ACROSS MOST OF FORECAST AREA EARLY
THIS MORNING. EXCEPTION IS SOME ALTOCUMULUS CLOUDS OVER SE UT LEFT
OVER FROM LAST NIGHT AND WHERE THE RAP MODEL PUTS A WEAK VORTICITY
MAX. CURRENT FORECAST FOR THIS AFTERNOON SEEMS ON TRACK PER QUICK
LOOK AT THE LATEST RAP/HRRR MODELS.
&&
.SHORT TERM...(TODAY THROUGH TUESDAY)
300 AM MDT MON AUG 19 2013
HIGH PRESSURE WILL REMAIN ANCHORED OVER THE REGION FOR THE NEXT
SEVERAL DAYS. MOISTURE WORKING NORTHWARD WILL BRING ANOTHER ROUND
OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING...WITH THE
FOCUS TODAY GENERALLY SOUTH OF INTERSTATE 70. STORMS WILL
INITIALLY FIRE ALONG THE HIGHER TERRAIN...WITH ACTIVITY DRIFTING
OFF OVER THE VALLEYS LATE THIS AFTERNOON AND EVENING...WITH AN
EMPHASIS ON DRIFT. WINDS ALOFT WILL BE WEAK WITH THE RIDGE
DIRECTLY OVERHEAD AND POTENTIAL FOR LOCALLY HEAVY RAINFALL WILL BE
UP A BIT WITH SLOW STORM MOTIONS. TEMPERATURES WILL BE RUNNING
NEAR SEASONAL NORMS WITH LIGHT WINDS OUTSIDE OF CONVECTIVE GUSTS
TO NEAR 40 MPH WITH THE STRONGER STORMS.
A STRONGER SURGE OF SUBTROPICAL MOISTURE CONTINUES TO WORK INTO
THE GREAT BASIN AND THEN LEAKS EASTWARD INTO TUESDAY FOR AN UPTURN
IN SHOWERS AND THUNDERSTORMS. THE SHEARED ENERGY FROM THE BAJA
DISTURBANCE IS PROGGED TO STAY WELL WEST OF THIS CWA WITH TIME
HEIGHT SECTIONS SHOWING LITTLE ORGANIZED DYNAMICAL LIFT. STILL
PRECIPITABLE WATER VALUES CLIMB TO AN INCH OVER EASTERN UTAH AND
FAR WESTERN COLORADO. BROKEN TO OVERCAST SKIES MAY LIMIT OR DELAY
AFTERNOON HEATING AND INSTABILITY SOMEWHAT. SLOW STORM MOTION WILL
PRODUCE LOCALLY HEAVY RAIN AND POTENTIAL RUNOFF PROBLEMS. A
RELATIVELY DRY NEAR- SURFACE LAYER WILL ALSO ASSIST WITH ENHANCED
LOCAL OUTFLOW WINDS.
.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
300 AM MDT MON AUG 19 2013
BOUNDARY INTERACTION MAY PRODUCE ISOLATED NOCTURNAL CONVECTION
INTO WEDNESDAY MORNING. THE 593 HIGH REBOUNDS WESTWARD BACK TO
NEAR THE FOUR CORNERS. BOTH THE GFS AND NAM ERODE PRECIPITABLE
WATER VALUES SOMEWHAT UNDER THE HIGH. SUBSIDENCE WILL ALSO CAP
LATE DAY CONVECTION A BIT COMPARED TO TUESDAY. STILL ALL MTN
RANGES WILL LIKELY FIRE SOME AFTERNOON STORMS. STORM MOTION
REMAINS SLOW FOR A CONTINUED THREAT OF LOCALLY HEAVY SHOWERS.
MOISTURE WORKING NORTHWARD ALONG THE WESTERN EDGE OF HIGH PRESSURE
CENTERED ACROSS THE CENTRAL PLAINS WILL KEEP CONDITIONS UNSETTLED
AS WE MOVE THROUGH THE WEEK AND INTO THE WEEKEND. HARD TO PIN
POINT ANY INDIVIDUAL WAVE IN THIS PATTERN FOR ENHANCED
POTENTIAL...SO FOR NOW WILL CONTINUE WITH THE BROAD BRUSH APPROACH
OF DAILY CONVECTION...PRIMARILY FOCUSED ON THE AFTERNOON AND
EVENING HOURS. TEMPERATURES WILL BE RUNNING NEAR SEASONAL NORMS
THROUGH THE PERIOD.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
300 AM MDT MON AUG 19 2013
SCATTERED SHOWERS AND THUNDERSTORMS WILL AGAIN DEVELOP ACROSS
EASTERN UTAH AND WESTERN COLORADO THIS AFTERNOON AND EVENING. THE
STORMS WILL BE MOST NUMEROUS SOUTH AND EAST OF A LINE FROM K4HV TO
KEGE...ESPECIALLY BETWEEN 20Z THIS AFTERNOON AND 03Z THIS EVENING.
OUTSIDE OF THIS WINDOW...STORMS WILL BE MORE ISOLATED IN NATURE.
EXPECT BRIEF HEAVY RAIN...SMALL HAIL AND GUSTY OUTFLOW WINDS TO
40 MPH IN THE VICINITY OF SHOWERS WITH BRIEF MOUNTAIN OBSCURATIONS
POSSIBLE. STORMS DISSIPATE AFTER 03Z THIS EVENING WITH VFR CONDS
PREVAILING AT ALL TERMINAL SITES.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.
&&
$$
UPDATE...JAD
SHORT TERM...JDC/JOE
LONG TERM...JOE/JDC
AVIATION...JDC
AREA FORECAST DISCUSSION
NWS GRAND JUNCTION CO
837 AM MDT MON AUG 19 2013
.UPDATE...
ISSUED AT 830 AM MDT MON AUG 19 2013
QUICK UPDATE TO THE GRIDDED FORECAST TO BETTER REFLECT THE CURRENT
SUNNY/MOSTLY CONDITIONS ACROSS MOST OF FORECAST AREA EARLY THIS
MORNING. EXCEPTION IS SOME ALTOCUMULUS CLOUDS OVER SE UT LEFT OVER
FROM LAST NIGHT AND WHERE THE RAP MODEL PUTS A WEAK VORTICITY MAX.
CURRENT FORECAST FOR THIS AFTERNOON SEEMS ON TRACK PER QUICK LOOK
AT THE LATEST RAP/HRRR MODELS.
&&
.SHORT TERM...(TODAY THROUGH TUESDAY)
300 AM MDT MON AUG 19 2013
HIGH PRESSURE WILL REMAIN ANCHORED OVER THE REGION FOR THE NEXT
SEVERAL DAYS. MOISTURE WORKING NORTHWARD WILL BRING ANOTHER ROUND
OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING...WITH THE
FOCUS TODAY GENERALLY SOUTH OF INTERSTATE 70. STORMS WILL
INITIALLY FIRE ALONG THE HIGHER TERRAIN...WITH ACTIVITY DRIFTING
OFF OVER THE VALLEYS LATE THIS AFTERNOON AND EVENING...WITH AN
EMPHASIS ON DRIFT. WINDS ALOFT WILL BE WEAK WITH THE RIDGE
DIRECTLY OVERHEAD AND POTENTIAL FOR LOCALLY HEAVY RAINFALL WILL BE
UP A BIT WITH SLOW STORM MOTIONS. TEMPERATURES WILL BE RUNNING
NEAR SEASONAL NORMS WITH LIGHT WINDS OUTSIDE OF CONVECTIVE GUSTS
TO NEAR 40 MPH WITH THE STRONGER STORMS.
A STRONGER SURGE OF SUBTROPICAL MOISTURE CONTINUES TO WORK INTO
THE GREAT BASIN AND THEN LEAKS EASTWARD INTO TUESDAY FOR AN UPTURN
IN SHOWERS AND THUNDERSTORMS. THE SHEARED ENERGY FROM THE BAJA
DISTURBANCE IS PROGGED TO STAY WELL WEST OF THIS CWA WITH TIME
HEIGHT SECTIONS SHOWING LITTLE ORGANIZED DYNAMICAL LIFT. STILL
PRECIPITABLE WATER VALUES CLIMB TO AN INCH OVER EASTERN UTAH AND
FAR WESTERN COLORADO. BROKEN TO OVERCAST SKIES MAY LIMIT OR DELAY
AFTERNOON HEATING AND INSTABILITY SOMEWHAT. SLOW STORM MOTION WILL
PRODUCE LOCALLY HEAVY RAIN AND POTENTIAL RUNOFF PROBLEMS. A
RELATIVELY DRY NEAR- SURFACE LAYER WILL ALSO ASSIST WITH ENHANCED
LOCAL OUTFLOW WINDS.
.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
300 AM MDT MON AUG 19 2013
BOUNDARY INTERACTION MAY PRODUCE ISOLATED NOCTURNAL CONVECTION
INTO WEDNESDAY MORNING. THE 593 HIGH REBOUNDS WESTWARD BACK TO
NEAR THE FOUR CORNERS. BOTH THE GFS AND NAM ERODE PRECIPITABLE
WATER VALUES SOMEWHAT UNDER THE HIGH. SUBSIDENCE WILL ALSO CAP
LATE DAY CONVECTION A BIT COMPARED TO TUESDAY. STILL ALL MTN
RANGES WILL LIKELY FIRE SOME AFTERNOON STORMS. STORM MOTION
REMAINS SLOW FOR A CONTINUED THREAT OF LOCALLY HEAVY SHOWERS.
MOISTURE WORKING NORTHWARD ALONG THE WESTERN EDGE OF HIGH PRESSURE
CENTERED ACROSS THE CENTRAL PLAINS WILL KEEP CONDITIONS UNSETTLED
AS WE MOVE THROUGH THE WEEK AND INTO THE WEEKEND. HARD TO PIN
POINT ANY INDIVIDUAL WAVE IN THIS PATTERN FOR ENHANCED
POTENTIAL...SO FOR NOW WILL CONTINUE WITH THE BROAD BRUSH APPROACH
OF DAILY CONVECTION...PRIMARILY FOCUSED ON THE AFTERNOON AND
EVENING HOURS. TEMPERATURES WILL BE RUNNING NEAR SEASONAL NORMS
THROUGH THE PERIOD.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
300 AM MDT MON AUG 19 2013
SCATTERED SHOWERS AND THUNDERSTORMS WILL AGAIN DEVELOP ACROSS
EASTERN UTAH AND WESTERN COLORADO THIS AFTERNOON AND EVENING. THE
STORMS WILL BE MOST NUMEROUS SOUTH AND EAST OF A LINE FROM K4HV TO
KEGE...ESPECIALLY BETWEEN 20Z THIS AFTERNOON AND 03Z THIS EVENING.
OUTSIDE OF THIS WINDOW...STORMS WILL BE MORE ISOLATED IN NATURE.
EXPECT BRIEF HEAVY RAIN...SMALL HAIL AND GUSTY OUTFLOW WINDS TO
40 MPH IN THE VICINITY OF SHOWERS WITH BRIEF MOUNTAIN OBSCURATIONS
POSSIBLE. STORMS DISSIPATE AFTER 03Z THIS EVENING WITH VFR CONDS
PREVAILING AT ALL TERMINAL SITES.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.
&&
$$
UPDATE...JAD
SHORT TERM...JDC/JOE
LONG TERM...JOE/JDC
AVIATION...JDC
AREA FORECAST DISCUSSION
NWS NEW YORK NY
1122 AM EDT MON AUG 19 2013
.SYNOPSIS...
A HIGH PRESSURE WILL REMAIN OVER THE REGION THROUGH TUESDAY. A
BROAD...WEAK TROUGH OF LOW PRESSURE WILL REMAIN OVER THE
NORTHEASTERN U.S. TUESDAY NIGHT THROUGH WEDNESDAY NIGHT AS HIGH
PRESSURE REMAINS CENTERED TO OUR SOUTH. A COLD FRONT APPROACHES
FROM THE NORTHWEST THURSDAY...THEN CROSSES THE TRI-STATE THURSDAY
NIGHT AND FRIDAY MORNING. HIGH PRESSURE THEN BUILDS IN FROM THE
NORTHWEST FOR THE UPCOMING WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
SOMEWHAT COMPLICATED SCENARIO UNFOLDING THIS AFTERNOON/EVENING AS
AN ANTICYCLONIC UPPER LEVEL JET STREAK MOVES ACROSS THIS
AFTERNOON...FOLLOWED BY A MID LEVEL TROUGH THIS EVENING. THE JET
STREAK IS INDUCING AN INCREASE IN HIGH CLOUDS ATTM...AND MID LEVEL
CLOUDS SHOULD FOLLOW LATE THIS AFTERNOON AS WELL. SCT SHOWERS OVER
CENTRAL/ERN PA MAY SNEAK IN TO FAR WRN SECTIONS...AND THERE
APPEARS TO BE ENOUGH ELEVATED MUCAPE TO LEAVE IN A SLIGHT CHANCE
MENTION OF THUNDER THERE. FARTHER EAST...SHOULD SEE
SPRINKLES/SHOWERS OUT OF THE ADVANCING MID LEVEL CLOUD DECK.
FORCING AND MOISTURE ADVECTION ARE DISJOINTED...WITH THE UPPER
LEVEL JET STREAK OUTRUNNING OTHER LOWER LEVEL FEATURES...BUT HAVE
SEEN THESE JET STREAKS OUTPERFORM MODEL EXPECTATIONS AND THINK
LAST COUPLE OF RUNS OF THE RAP ARE POINTING IN THE RIGHT DIRECTION
TO WARRANT SPATIAL/TEMPORAL EXTENSION OF AT LEAST SLIGHT CHANCE
POP TO THE REST OF THE CWA...MAINLY THIS EVENING.
AS THE MID LEVEL TROUGH EXITS...THE MID AND UPR LVL MOISTURE WILL
FINALLY START TO BE SHUNTED S AND E OF THE CWA. THIS WILL RESULT
IN CLEARING SKIES OVERNIGHT.
&&
.SHORT TERM /TUESDAY/...
MOSTLY SUNNY WITH BUILDING HEIGHTS AND WARMER TEMPS. WITH WEAK
SUBSIDENCE THRU THE COLUMN...WILL CONTINUE DRY FCST.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
DEEP LAYERED RIDGING BUILDS OVER THE AREA TUESDAY NIGHT AND
WEDNESDAY...WITH THE RIDGE AXIS PASSING TO THE EAST WEDNESDAY
AFTERNOON AND NIGHT. DUE TO SUBSIDENCE UNDER THE RIDGE IT SHOULD BE
DRY WITH MINIMAL CLOUD COVER.
LOWS TUESDAY NIGHT SHOULD BE SLIGHTLY ABOVE NORMAL...CONSISTENT WITH
A BLEND OF MAV/MET GUIDANCE. HIGHS WEDNESDAY WILL RUN 5-10 DEGREES
ABOVE NORMAL...WITH THE POSSIBILITY OF LOCATIONS IN NYC AND URBAN NE
NJ REACHING OR JUST GOING ABOVE THE 90 DEGREE MARK. THIS IS
CONSISTENT WITH A BLEND OF MIXING DOWN FROM 850 HPA NEAR THE COAST
AND 825 HPA INLAND...NAM 2-METER TEMPERATURES AND A BLEND OF MAV/MET
GUIDANCE. FOR NOW IT APPEARS THAT HEAT INDICES WEDNESDAY AFTERNOON
WILL NOT BE MUCH MORE THAN THE AIR TEMPERATURE...SO A HEAT ADVISORY
IS NOT ANTICIPATED TO BE REQUIRED.
USED A BLEND OF MEX/MEN/ECE/WPC GUIDANCE FOR LOWS WEDNESDAY NIGHT
WITH VALUES A FEW DEGREES ABOVE NORMAL FORECAST.
SW FLOW ALOFT ON THURSDAY WITH A PASSING SHORTWAVE...THEN A 700-500
HPA TROUGH CROSSES THE AREA THURSDAY NIGHT AND FRIDAY. FOR NOW
LEANED TOWARDS FASTER ECMWF/CMC OVER SLOWER GFS WITH THE TROUGH
(THOUGH CONVERSELY SLOWER ECMWF/CMC FRONTAL TIMING VICE FASTER GFS).
AS A RESULT...LIMIT POPS TO SLIGHT CHANCE THURSDAY OVER WESTERN
ZONES TO REFLECT THE POTENTIAL FOR SHRA/TSTM WITH PASSING SHORTWAVE
AND THE DEVELOPMENT OF A PRE-FRONTAL TROUGH. GO WITH CHANCE POPS
AHEAD OF THE FRONT/MID-UPPER TROUGH THURSDAY NIGHT...AS IT APPEARS
DYNAMICS SHOULD BE SUFFICIENT TO OVERCOME MEAGER CAPE.
HOWEVER...GIVEN MEAGER CAPE...DID RESTRICT CHANCE OF THUNDER
THURSDAY NIGHT TO SLIGHT CHANCE. THE FRONT SHOULD FINISH MOVING
THROUGH PRETTY QUICKLY FRIDAY MORNING...SO ONLY HAVE SLIGHT CHANCE
POPS ACROSS THE NORTHERN TIER IN RESPONSE TO PASSING OF 700-500 HPA
TROUGH AXIS.
NW FLOW ALOFT IN THE WAKE OF THE DEPARTING TROUGH FRIDAY
NIGHT-SUNDAY. FOR NOW BELIEVE GFS IS TOO PROGRESSIVE - AS IT OFTEN
IS IN THE EXTENDED - IN BUILDING IN THE RIDGE AXIS FROM THE
SPRAWLING 500 HPA RIDGE FORECAST TO BE OVER THE MIDDLE PART OF THE
COUNTRY NEXT WEEKEND. SO DO NOT THINK IT WILL GET QUITE AS WARM AS
THE GFS WOULD SUGGEST. NOTING NO SHORTWAVES/MCS CURRENTLY FORECAST
HAVE GONE DRY SATURDAY-SUNDAY - HOWEVER THIS PATTERN IF THE FORECAST
BEARS OUT IS CONDUCIVE TO MCS DIVING DOWN FROM THE GREAT LAKES SO
WILL NEED TO MONITOR.
FOR TEMPERATURES THURSDAY-SUNDAY USED A BLEND OF MEX/MEN/ECE/WPC
GUIDANCE. TEMPERATURES START OUT ABOVE NORMAL AHEAD OF THE
FRONT...BUT RETURN TO NEAR TO SLIGHTLY BELOW NORMAL LEVELS FOR THE
WEEKEND BEHIND THE FRONT.
&&
.AVIATION /14Z MONDAY THROUGH FRIDAY/...
VFR FOR THE PERIOD.
W TO SW FLOW THROUGH THIS AFTERNOON WITH WIND GENERALLY BETWEEN 5
AND 10 KT. WINDS BECOME LIGHT AFTER 02/03Z THIS EVENING. SEA BREEZE
DEVELOPMENT EXPECTED TODAY.
SCT-BKN MID AND HIGH LEVEL CLOUDS...SCATTERING OUT LATER TONIGHT.
LOW CONFIDENCE OF LIGHT RAIN SHOWERS MAINLY WEST AND NORTH OF NYC
LATE AFTN...NOT INCLUDING IN TAFS WITH MINIMAL IMPACT ON CIGS/VIS.
NY METRO ENHANCED AVIATION WEATHER SUPPORT...
DETAILED INFORMATION...INCLUDING HOURLY TAF WIND COMPONENT FCSTS
CAN BE FOUND AT: HTTP:/WWW.ERH.NOAA.GOV/ZNY/N90 (LOWER CASE)
KJFK FCSTER COMMENTS: SEA BREEZE BETWEEN 16 AND 18Z...GENERALLY
SSW FLOW AROUND 12 KT. OCCASIONAL GUSTS UP TO 16 KT AFTN.
KLGA FCSTER COMMENTS: LOW CONFIDENCE OF SEA BREEZE. W FLOW WITH
OCCASIONAL GUSTS UP TO 15 KT THIS AFTN.
KEWR FCSTER COMMENTS: W FLOW WITH PSBL GUSTS UP TO 15 KT THIS
AFTN.
THE AFTERNOON KEWR HAZE POTENTIAL FORECAST IS GREEN...WHICH
IMPLIES SLANT RANGE VISIBILITY 7SM OR GREATER OUTSIDE OF CLOUD.
KTEB FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED.
KHPN FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED.
KISP FCSTER COMMENTS: MOD CONFIDENCE ON SEA BREEZE BETWEEN 16 AND
18Z.
OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY...
.TUE-WED...VFR.
.THU...CHC SUB-VFR IN SHOWERS/TSTM.
.FRI...VFR.
&&
.MARINE...
HIGH PRESSURE CENTERED SW OF THE WATERS WILL KEEP WINDS AND SEAS
BELOW SCA LEVELS THROUGH TUE. WINDS/SEAS E OF MORICHES INLET IN
LONGER FETCH WSW FLOW MAY HOWEVER GET CLOSE TO SCA LEVELS THIS
AFTERNOON.
A RELATIVELY RELAXED PRESSURE GRADIENT OVER THE REGION TUESDAY
NIGHT-FRIDAY WILL KEEP WINDS 10 KT AND SEAS TO 3 FT OR LESS OVER THE
COASTAL OCEAN WATERS AND TO 1 FT OR LESS OVER THE REMAINDER OF THE
WATERS AROUND LONG ISLAND.
&&
.HYDROLOGY...
ORGANIZED RAINFALL IS NOT EXPECTED THROUGH TUE. IT SHOULD THEN BE DRY
THOUGH THE MIDDLE OF THE WEEK.
&&
.EQUIPMENT...
THE NOAA ALL HAZARDS WEATHER RADIO TRANSMITTER IN NEW YORK CITY
HAS BEEN DE-ACTIVATED UNTIL FURTHER NOTICE.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...JMC/MALOIT
NEAR TERM...JMC
SHORT TERM...JMC
LONG TERM...MALOIT
AVIATION...BC/SEARS
MARINE...JMC/MALOIT
HYDROLOGY...JMC/MALOIT
AREA FORECAST DISCUSSION
NWS ALBANY NY
1037 AM EDT MON AUG 19 2013
.SYNOPSIS...
DRY WEATHER IS EXPECTED TO CONTINUE INTO THE MID WEEK PERIOD WITH
WARMING TEMPERATURES...AS HIGH PRESSURE REMAINS IN PLACE ACROSS OUR
REGION. A COLD FRONT IS EXPECTED TO DROP SOUTHEAST FROM THE UPPER
GREAT LAKES AND SOUTHEAST CANADA BRINGING A CHANCE OF SHOWERS AND
THUNDERSTORMS LATE THURSDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 1037 AM EDT...MORNING FOG HAS BURNED OFF ACROSS THE REGION.
WHILE THE ADIRONDACKS ARE NEARLY CLEAR...A BAND OF MID AND HIGH
LEVEL CLOUDS IS STREAMING NORTHEASTWARD ACROSS THE
CATSKILLS...CAPITAL REGION...AND INTO SRN VT AND THE BERKSHIRES.
THESE CLOUDS...ASSOCIATED WITH A SHORTWAVE TROUGH OVER PA AND A
100+ KT JET STREAK OVER THE NORTHEAST...WILL CONTINUE FOR THE NEXT
SEVERAL HOURS. THE TROUGH WILL BEGIN TO SHEAR OUT BY LATER
TODAY...AND THE BEST BAND OF CLOUDS WILL BEGIN TO SHIFT SOUTH AND
EAST OF THE REGION...ALLOWING FOR SOME IMPROVEMENT IN THE SKY
COVER...WITH MOST AREAS PARTLY CLOUDY BY LATER THIS AFTERNOON.
ANY LIGHT SHOWERS WITH THIS SHORTWAVE SHOULD REMAIN SOUTH OF THE
AREA ACROSS PA AND NJ...SO NO POPS ACROSS OUR REGION TODAY. THE
LATEST 12Z LOCAL HIRES WRF AND 3KM HRRR ALL AGREE THAT WE
SHOULDN/T HAVE ANY SHOWERS IN OUR AREA TODAY AS WELL...WITH THE
BEST MOISTURE/FORCING TO THE SOUTH.
WITH CLOUDS EXPECTED TO CLEAR OR THIN OUT...WE STILL APPEAR ON
TRACK FOR MAX TEMPS IN THE UPPER 70S TO LOW 80S ACROSS LOWER
TERRAIN PORTIONS OF THE AREA. THE HILLS AND MTNS WILL SEE MAX
TEMPS RANGING FROM THE UPPER 60S TO THE MID 70S.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
TRANQUIL WEATHER IS EXPECTED THROUGH THE PERIOD WITH WARMING
TEMPERATURES AND SLOWLY RISING HUMIDITY LEVELS. OUR REGION WILL BE
UNDER THE INFLUENCE OF SURFACE HIGH PRESSURE...WITH UPPER LEVEL
HEIGHTS GRADUALLY RISING THROUGH THE PERIOD AS WELL. SO DESPITE
STRONG SURFACE HEATING...CONVECTION IS NOT EXPECTED SINCE UPPER
LEVEL TEMPERATURES WILL BE QUITE WARM /AROUND -7C AT 500 MB TUESDAY
INTO WEDNESDAY/.
WITH THE WARMING ALOFT...MAX TEMPS ON TUESDAY ARE EXPECTED TO REACH
THE MID 80S IN MOST VALLEY LOCATIONS WITH UPPER 80S ON WEDNESDAY.
OVERNIGHT LOWS ARE EXPECTED TO BE ABOVE NORMAL AS WELL...ESPECIALLY
TUESDAY NIGHT AND WEDNESDAY NIGHT WHEN THE WARMEST AIR ALOFT WILL BE
OVER THE REGION. LATE NIGHT/EARLY MORNING PATCHY FOG WILL BE
COMMON IN FAVORED AREAS AGAIN...ESPECIALLY TONIGHT AND TUESDAY
NIGHT.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
MAINLY DRY WEATHER IS EXPECTED DURING THE LONG TERM PERIOD EXCEPT
FOR LATE THURSDAY INTO THURSDAY EVENING WHEN SHOWERS AND
THUNDERSTORMS ARE POSSIBLE ESPECIALLY NORTHERN AREAS AHEAD OF A COLD
FRONT DROPPING SOUTHEASTWARD THROUGH THE FA. WHILE THERE IS LIMITED
MOISTURE TO WORK WITH AHEAD OF THE COLD FRONT...SHOWALTER INDICES
ARE SLIGHTLY NEGATIVE AND SB CAPES RISE BRIEFLY TO BTWN 500 AND 1000
J/KG. WL HAV CHANCE POPS ACRS THE SRN ADIRONDACKS AND LAKE GEORGE
REGION AND SLIGHT CHANCE POPS ELSEWHERE LATE THURSDAY. FRIDAY
THROUGH SUNDAY EXPECT MAINLY DRY CONDITIONS...ALTHOUGH WIDELY
SCATTERED SHOWERS ARE POSSIBLE ON FRIDAY WITH THE UPPER TROF AXIS
CROSSING THE FA.
TEMPS ARE EXPECTED TO BE VERY WARM AHEAD OF THE FRONT ON THURSDAY
FOLLOWED BY A GRADUAL COOL DOWN HEADING INTO THE WEEKEND IN THE WAKE
OF THE COLD FRONT. HIGHS ON THURSDAY ARE EXPECTED TO BE IN THE 80S
TO AROUND 90 WITH MID 70S TO MID 80S ON FRIDAY...70S TO AROUND 80 ON
SATURDAY AND MID 70S TO LOWER 80S ON SUNDAY. LOWS WILL BE IN THE MID
50S TO MID 60S THURSDAY NIGHT AND 50S TO AROUND 60 FRIDAY NIGHT AND
SATURDAY NIGHT.
&&
.AVIATION /15Z MONDAY THROUGH FRIDAY/...
ANY AREAS OF FOG AND ASSOCIATED IFR CONDITIONS SHOULD LIFT/BECOME
VFR BY 13Z...WITH VFR CONDITIONS THEN PREVAILING THROUGH THE DAY
MONDAY. A RETURN TO IFR CONDITIONS IS HIGHLY LIKELY AGAIN THIS
EVENING AT KGFL AND KPSF WITH MVFR CONDITIONS POSSIBLE LATE
TONIGHT AT KALB AND KPOU.
LIGHT/VARIABLE WINDS WILL BECOME WEST TO SOUTHWEST AT 5-10 KTS BY
THIS AFTERNOON AND THEN LIGHT AND VARIABLE THIS EVENING.
OUTLOOK...
TUESDAY-WEDNESDAY NIGHT: NO OPERATIONAL IMPACT. NO SIG WX.
THURSDAY-THURSDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF
SHRA...TSRA.
FRIDAY: LOW OPERATIONAL IMPACT. SLIGHT CHANCE OF SHRA.
&&
.FIRE WEATHER...
NO FIRE WEATHER RELATED ISSUED ARE EXPECTED THROUGH THE PERIOD.
MINIMUM RELATIVE HUMIDITY VALUES WILL RANGE FROM AROUND 40 TO 50
PERCENT THIS AFTERNOON...WITH FULL RECOVERY TO BETWEEN 95 AND 100
PERCENT TONIGHT WITH DEW FORMATION. RH VALUES WILL DROP TO AROUND 35
TO 45 PERCENT TUESDAY AFTERNOON. WINDS WILL BE WESTERLY AT 5 TO 10
MPH TONIGHT...BECOMING LIGHT AND VARIABLE TONIGHT. WINDS ON TUESDAY
WILL ONCE AGAIN BE WESTERLY AROUND 5 TO 10 MPH.
&&
.HYDROLOGY...
DRY WEATHER IS EXPECTED TO CONTINUE THROUGH THE MIDDLE OF THE
WEEK...WITH RIVER LEVELS NEAR NORMAL FOR MID TO LATE AUGUST. THE
NEXT CHANCE OF ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS
ARRIVES LATE THURSDAY ASSOCIATED WITH A COLD FRONT. THE
PRECIPITATION IS NOT EXPECTED TO BE WIDESPREAD AND SHOULD HAVE
MINIMAL IMPACT ON MAIN STEM RIVERS.
FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED
AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE
ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
MA...NONE.
VT...NONE.
&&
$$
SYNOPSIS...JPV
NEAR TERM...FRUGIS
SHORT TERM...JPV
LONG TERM...11
AVIATION...11
FIRE WEATHER...JPV
HYDROLOGY...JPV
AREA FORECAST DISCUSSION
NWS CHARLESTON SC
1033 AM EDT MON AUG 19 2013
.SYNOPSIS...
A STATIONARY FRONT OVER THE AREA WILL DISSIPATE AS HIGH PRESSURE
BUILDS WEST ACROSS THE AREA MID TO LATE WEEK. A WEAK TROUGH OF LOW
PRESSURE WILL APPROACH FROM THE NORTHWEST THIS WEEKEND...FOLLOWED BY
HIGH PRESSURE INTO EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
LATE MONDAY MORNING...ONGOING FORECASTS REMAINED ON TRACK AND
REQUIRED ONLY MINOR ADJUSTMENTS. RAISED POPS BY 10-20 PERCENT
ACROSS SC/INLAND COUNTIES..CERTAINLY NOT A MAJOR CHANGE BUT STILL
SUFFICIENT TO GENERATE LIKELY POPS CLOSE TO THE CONVERGENCE AXIS
ON THE PERIPHERY OF THE WEDGE STILL IN PLACE N/NW OF THE REGION.
SOUTHEAST GEORGIA AND SOUTHERN SOUTH CAROLINA WILL REMAIN IN THE
NW FLANKS OF THE ATLC SUBTROPICAL RIDGE TODAY. THE DEPARTING UPPER
TROUGH FROM THE OHIO VALLEY TO THE MID SOUTH REGION IS PROGGED TO
LIFT OUT TO THE NE INTO NEW ENGLAND BY LATE DAY. THE TAIL OF THE
MID LEVEL VORT WILL INDUCE SOME VERY WEAK HEIGHT FALLS OVER THE
INLAND CAROLINAS TODAY WHILE DEEP MID SUMMER MOISTURE PERSISTS
REGION-WIDE. THE OLD WEDGE FRONT WILL CONTINUE TO DECAY OVER THE
CAROLINAS TODAY.
MODIFIED 12Z SOUNDINGS AND 00Z-06Z MODEL PROGS SUGGEST AN ACTIVE
CONVECTIVE REGIME TODAY FEATURING EXPANDING COVERAGE OF SHOWERS/
THUNDERSTORMS. POPS ARE GRADUATED FROM HIGH CHANCE/LIKELY ACROSS
INLAND COUNTIES OF SC/GA AND SC COUNTIES FROM COLLETON COUNTY EAST
THROUGH COASTAL LOCATIONS TO 30-40 PERCENT ACROSS FROM JASPER
COUNTY S/SW THROUGH AREAS ALONG/SOUTH OF I-16 INCLUDING THE
SAVANNAH VICINITY. BEST COVERAGE WILL OCCUR SOME OF OUR INLAND
AREAS COULD SEE SOME VERY HEAVY DOWNPOURS IN DEEP CONVECTION THIS
AFTERNOON.
THE 12Z HRRR INDICATES A COMPLEX MESOSCALE ENVIRONMENT FEATURING
NUMEROUS BOUNDARIES INCLUDING THE SE BREEZE...THE INLAND TROUGH
AND OUTFLOW BOUNDARIES. THUS...EXPECT SOME REPEATING SHOWERS/
THUNDERSTORMS WITH LOCALLY HEAVY CONVECTIVE RAINS ESPECIALLY N OF
I-16 AND INLAND FROM U.S. 17 WHERE THE SUBTLE MID LEVEL HEIGHT
FALLS OCCUR. WILL CONTINUE TO HIGHLIGHT A RISK FOR LOCALLY HEAVY
DOWNPOURS AND MINOR TEMPORARY FLOODING CONCERNS FOR OUR NW INLAND
ZONES IN OUR HAZARDOUS WEATHER OUTLOOK. THIS IS MAINLY IN RESPECT
TO THE SOGGY SOIL CONDITIONS AND ONGOING RIVER FLOODING PLUS
SWOLLEN TIDAL CREEKS WITH THE FULL MOON CYCLE.
WE RAISED HIGH TEMPS A DEGREE OR SO IN SOME AREAS AS GUIDANCE IS
RUNNING TOO COOL NOW THE WEDGE TO GONE.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
TUESDAY THROUGH THURSDAY...A TYPICAL SUMMERTIME PATTERN WILL EVOLVE
OVER THE SOUTHEASTERN UNITED STATES AS ATLANTIC HIGH PRESSURE
EXPANDS OVER THE AREA THROUGH MIDWEEK. AS THIS OCCURS...DEEPEST
MOISTURE WILL SHIFT INLAND AND WILL BE THE MAIN SOURCE OF PRECIP
ACTIVITY EACH AFTERNOON WHILE WEAK H5 SHORTWAVES PASS OVERHEAD.
DESPITE THE INLAND SHIFT OF DEEPEST MOISTURE...LIGHT ONSHORE FLOW
WILL SUPPORT PWATS BETWEEN 1.5 TO 2 INCHES AS WELL AS SCATTERED
SHOWERS AND/OR THUNDERSTORMS OVER SOUTHEAST SOUTH CAROLINA AND
SOUTHEAST GEORGIA. HOWEVER...EXPECT MOST SHOWERS/THUNDERSTORMS TO
GRADUALLY SHIFT INLAND BY EARLY AFTERNOON EACH DAY ALONG OR AHEAD A
SEABREEZE.
OVERALL HIGH TEMPS SHOULD RANGE IN THE UPPER 80S TO AROUND 90 EACH
AFTERNOON. OVERNIGHT LOWS WILL RANGE IN THE LOW 70S INLAND TO
MID/UPPER 70S ALONG THE COAST.
&&
.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
A TYPICAL SUMMERTIME PATTERN WILL PERSIST THROUGH LATE WEEK AS
ATLANTIC HIGH PRESSURE REMAINS OVER THE SOUTHEAST. CONDITIONS SHOULD
REMAIN SOMEWHAT DRYER THROUGH FRIDAY WITH WEST/SOUTHWEST FLOW ALOFT.
HIGH PRESSURE WILL THEN GRADUALLY RETREAT SOUTH AND EAST INTO THE
WEEKEND AS A WEAK TROUGH OF LOW PRESSURE APPROACHES FROM THE NORTHWEST.
A SLIGHT CHANCE OF SHOWERS AND/OR THUNDERSTORMS WILL BE POSSIBLE
EACH DAY...WITH POSSIBLY INCREASING CHANCES ON SUNDAY BEFORE SFC
HIGH PRESSURE AND DRYER MID LVL AIR SHIFTS OVER THE SOUTHEAST INTO
EARLY NEXT WEEK. OVERALL HIGH TEMPS SHOULD RANGE IN THE UPPER 80S
TO LOWER 90S EACH AFTERNOON...HIGHEST OVER INLAND AREAS IN
SOUTHEAST GEORGIA. OVERNIGHT LOW TEMPS SHOULD RANGE IN THE LOW 70S
INLAND TO LOW/MID 70S ALONG THE COAST.
&&
.AVIATION /14Z MONDAY THROUGH FRIDAY/...
SHOWER/TSTM COVERAGE WILL INCREASE TODAY...AND THE POTENTIAL FOR
DIRECT IMPACTS AT TERMINALS WILL INCREASE. HOWEVER...ASIDE FROM
OCCASIONAL SHOWERS WHICH WILL IMPACT KCHS THROUGH EARLY AFTERNOON
PRECISE TIMING OF SHOWERS/TSTMS AND ASSOCIATED IMPACTS WILL BE
INCLUDED WITHIN AMENDMENTS...WITH VCTS OTHERWISE INDICATED UNTIL
AROUND 00Z. OUTSIDE PRECIPITATION...MAINLY VFR CONDITIONS WILL
PREVAIL...WITH ONLY A LOW PROBABILITY FOR FLIGHT RESTRICTIONS LATE
TONIGHT/EARLY TUESDAY.
EXTENDED AVIATION OUTLOOK...VFR CONDITIONS ARE EXPECTED TO PREVAIL
TUESDAY THROUGH SATURDAY AS HIGH PRESSURE PERSISTS OVER THE
SOUTHEAST. BRIEF MVFR CIGS/VSBYS ARE POSSIBLE EACH AFTERNOON WITH
INLAND MOVING SHOWERS AND/OR THUNDERSTORMS.
&&
.MARINE...
ATLC HIGH PRES WILL BE THE MAIN PLAYER FOR THE WATERS. MAINLY A
S TO SE FLOW 10 KT OR LESS THROUGH TONIGHT WITH SEAS 2 TO 3 FT.
HIGHER WINDS/SEAS COULD DEVELOP LOCALLY WITHIN/NEAR LOCALIZED
SHOWERS/TSTMS.
TUESDAY THROUGH FRIDAY...WINDS/SEAS ARE EXPECTED TO REMAIN WELL
BELOW SMALL CRAFT ADVISORY LEVELS THROUGH LATE WEEK WITH HIGH
PRESSURE DOMINATING THE WATERS. IN GENERAL...SOUTH TO SOUTHEAST
WINDS WILL REMAIN AT OR BELOW 10-12 KT...HIGHEST NEAR SEABREEZE
CIRCULATIONS ALONG THE COAST. SEAS WILL REMAIN AT OR BELOW
3 FT...HIGHEST IN OUTER GEORGIA WATERS.
WATERSPOUTS...IT IS LOOKING DECENT THIS MORNING GIVEN INSTABILITY
AND LIGHT CHAOTIC WIND FIELDS. WILL BE WAITING FOR SUNRISE TO SPOT
CU LINES AND LAND BREEZE BOUNDARIES BEFORE ISSUING ANY MARINE WEATHER
STATEMENTS.
RIP CURRENTS...A SLIGHT INCREASE IN SWELLS COULD LEAD TO A MODERATE
RISK OF RIPS BY MID WEEK. LOW RISK AT AREA BEACHES TODAY.
&&
.TIDES/COASTAL FLOODING...
GIVEN THE PERIGEAN SPRING TIDES...ADDITIONAL COASTAL FLOOD
ADVISORIES ARE POSSIBLE THROUGH MID-WEEK WITH THE EVENING HIGH
TIDE CYCLE. THIS EVENINGS HIGH TIDE SHORTLY BEFORE SUNSET COULD
PRODUCE SHALLOW COASTAL FLOODING IN DOWNTOWN CHARLESTON AND FORT
PULASKI ONCE AGAIN.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...
NEAR TERM...SPR
SHORT TERM...DPB
LONG TERM...DPB
AVIATION...SPR
MARINE...DPB/SPR
TIDES/COASTAL FLOODING...
AREA FORECAST DISCUSSION
NWS CHARLESTON SC
732 AM EDT MON AUG 19 2013
.SYNOPSIS...
A STATIONARY FRONT OVER THE AREA WILL DISSIPATE AS HIGH PRESSURE
BUILDS WEST ACROSS THE AREA MID TO LATE WEEK. A WEAK TROUGH OF LOW
PRESSURE WILL APPROACH FROM THE NORTHWEST THIS WEEKEND...FOLLOWED BY
HIGH PRESSURE INTO EARLY NEXT WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
SOUTHEAST GEORGIA AND SOUTHERN SOUTH CAROLINA WILL REMAIN IN THE
NW FLANKS OF THE ATLC SUBTROPICAL RIDGE TODAY. THE DEPARTING UPPER
TROUGH FROM THE OHIO VALLEY TO THE MID SOUTH REGION IS PROGGED TO
LIFT OUT TO THE NE INTO NEW ENGLAND BY LATE DAY. THE TAIL OF THE
MID LEVEL VORT WILL INDUCE SOME VERY WEAK HEIGHT FALLS OVER THE
INLAND CAROLINAS TODAY WHILE DEEP MID SUMMER MOISTURE PERSISTS
REGION-WIDE. THE OLD WEDGE FRONT CONTINUES TO DECAY OVER THE
CAROLINAS TODAY.
FORECAST SOUNDINGS AND 00Z MODEL PROGS INDICATE POTENTIAL FOR
SCATTERED CONVECTIVE RAINS TO DEVELOP OVER PORTIONS THE AREA BY
MID MORNING ONCE THE LAND MASS BEGINS TO QUICKLY WARM AND
ESPECIALLY SINCE SATELLITE IMAGERY SHOWS STRONG POTENTIAL FOR
DIFFERENTIAL HEATING WITH I-95 THE DIVIDING LINE. CHANCE POPS ARE
EXPECTED TO SPREAD INLAND THIS AFTERNOON WITH MANY AREAS ALONG AND
W OF U.S. 17 EXPECTED TO SEE SCATTERED SHOWERS AND TSTMS. SOME OF
OUR INLAND AREAS COULD SEE SOME VERY HEAVY DOWNPOURS IN DEEP
CONVECTION THIS AFTERNOON. THE LATEST 3KM RAP MODEL INDICATES A
PRETTY COMPLEX MESOSCALE AND THUS EXPECT SOME LOCALLY HEAVY
CONVECTIVE RAINS WILL DEVELOP N OF I-16 AND INLAND FROM U.S. 17
WHERE THE SUBTLE MID LEVEL HEIGHT FALLS OCCUR. WE WILL HIGHLIGHT A
RISK FOR LOCALLY HEAVY DOWNPOURS AND MINOR TEMPORARY FLOODING
CONCERNS FOR OUR NW INLAND ZONES IN OUR HAZARDOUS WEATHER OUTLOOK.
THIS IS MAINLY IN RESPECT TO THE SOGGY SOIL CONDITIONS AND ONGOING
RIVER FLOODING PLUS SWOLLEN TIDAL CREEKS WITH THE FULL MOON CYCLE.
WE RAISED HIGH TEMPS A DEGREE OR SO IN SOME AREAS AS GUIDANCE IS
RUNNING TOO COOL NOW THE WEDGE TO GONE.
&&
.SHORT TERM /TUESDAY THROUGH THURSDAY/...
TUESDAY THROUGH THURSDAY...A TYPICAL SUMMERTIME PATTERN WILL EVOLVE
OVER THE SOUTHEASTERN UNITED STATES AS ATLANTIC HIGH PRESSURE
EXPANDS OVER THE AREA THROUGH MIDWEEK. AS THIS OCCURS...DEEPEST
MOISTURE WILL SHIFT INLAND AND WILL BE THE MAIN SOURCE OF PRECIP
ACTIVITY EACH AFTERNOON WHILE WEAK H5 SHORTWAVES PASS OVERHEAD.
DESPITE THE INLAND SHIFT OF DEEPEST MOISTURE...LIGHT ONSHORE FLOW
WILL SUPPORT PWATS BETWEEN 1.5 TO 2 INCHES AS WELL AS SCATTERED
SHOWERS AND/OR THUNDERSTORMS OVER SOUTHEAST SOUTH CAROLINA AND
SOUTHEAST GEORGIA. HOWEVER...EXPECT MOST SHOWERS/THUNDERSTORMS TO
GRADUALLY SHIFT INLAND BY EARLY AFTERNOON EACH DAY ALONG OR AHEAD A
SEABREEZE.
OVERALL HIGH TEMPS SHOULD RANGE IN THE UPPER 80S TO AROUND 90 EACH
AFTERNOON. OVERNIGHT LOWS WILL RANGE IN THE LOW 70S INLAND TO
MID/UPPER 70S ALONG THE COAST.
&&
.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
A TYPICAL SUMMERTIME PATTERN WILL PERSIST THROUGH LATE WEEK AS
ATLANTIC HIGH PRESSURE REMAINS OVER THE SOUTHEAST. CONDITIONS SHOULD
REMAIN SOMEWHAT DRYER THROUGH FRIDAY WITH WEST/SOUTHWEST FLOW ALOFT.
HIGH PRESSURE WILL THEN GRADUALLY RETREAT SOUTH AND EAST INTO THE
WEEKEND AS A WEAK TROUGH OF LOW PRESSURE APPROACHES FROM THE NORTHWEST.
A SLIGHT CHANCE OF SHOWERS AND/OR THUNDERSTORMS WILL BE POSSIBLE
EACH DAY...WITH POSSIBLY INCREASING CHANCES ON SUNDAY BEFORE SFC
HIGH PRESSURE AND DRYER MID LVL AIR SHIFTS OVER THE SOUTHEAST INTO
EARLY NEXT WEEK. OVERALL HIGH TEMPS SHOULD RANGE IN THE UPPER 80S
TO LOWER 90S EACH AFTERNOON...HIGHEST OVER INLAND AREAS IN
SOUTHEAST GEORGIA. OVERNIGHT LOW TEMPS SHOULD RANGE IN THE LOW 70S
INLAND TO LOW/MID 70S ALONG THE COAST.
&&
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
A MAINLY VFR FORECAST THIS TAF CYCLE AT THE KCHS/KSAV TERMINALS
WITH POTENTIAL FOR BRIEF MVFR CIGS JUST AFTER SUNRISE AS THE LAND
HEATS AND CUMULUS FIELDS DEVELOP. SCATTERED SHOWERS DEVELOPING
THIS MORNING IN THE COASTAL CORRIDOR PER LATEST RADAR AND MODEL
OUTPUT...PUSHING INLAND THIS AFTERNOON. IF DEEPER CONVECTION
DEVELOPS IT COULD SLIDE BACK INTO THE THE TAF CORRIDOR AFTER MID
AFTERNOON AS STEERING FAVORS A SW-NE TRAJECTORY. CONFIDENCE LOW
ON TIMING OF ANY TSTMS AT THE TERMINALS TODAY.
EXTENDED AVIATION OUTLOOK...VFR CONDITIONS ARE EXPECTED TO PREVAIL
TUESDAY THROUGH SATURDAY AS HIGH PRESSURE PERSISTS OVER THE
SOUTHEAST. BRIEF MVFR CIGS/VSBYS ARE POSSIBLE EACH AFTERNOON WITH
INLAND MOVING SHOWERS AND/OR THUNDERSTORMS.
&&
.MARINE...
ATLC HIGH PRES WILL BE THE MAIN PLAYER FOR THE WATERS. MAINLY A
LIGHT SE TO SSE FLOW THROUGH TONIGHT WITH SEAS 2 TO 3 FT.
TUESDAY THROUGH FRIDAY...WINDS/SEAS ARE EXPECTED TO REMAIN WELL
BELOW SMALL CRAFT ADVISORY LEVELS THROUGH LATE WEEK WITH HIGH
PRESSURE DOMINATING THE WATERS. IN GENERAL...SOUTH TO SOUTHEAST
WINDS WILL REMAIN AT OR BELOW 10-12 KT...HIGHEST NEAR SEABREEZE
CIRCULATIONS ALONG THE COAST. SEAS WILL REMAIN AT OR BELOW
3 FT...HIGHEST IN OUTER GEORGIA WATERS.
WATERSPOUTS...IT IS LOOKING DECENT THIS MORNING GIVEN INSTABILITY
AND LIGHT CHAOTIC WIND FIELDS. WILL BE WAITING FOR SUNRISE TO SPOT
CU LINES AND LAND BREEZE BOUNDARIES BEFORE ISSUING ANY MARINE WEATHER
STATEMENTS.
RIP CURRENTS...A SLIGHT INCREASE IN SWELLS COULD LEAD TO A MODERATE
RISK OF RIPS BY MID WEEK. LOW RISK AT AREA BEACHES TODAY.
&&
.TIDES/COASTAL FLOODING...
GIVEN THE PERIGEAN SPRING TIDES...ADDITIONAL COASTAL FLOOD
ADVISORIES ARE POSSIBLE THROUGH MID-WEEK WITH THE EVENING HIGH
TIDE CYCLE. THIS EVENINGS HIGH TIDE SHORTLY BEFORE SUNSET COULD
PRODUCE SHALLOW COASTAL FLOODING IN DOWNTOWN CHARLESTON AND FORT
PULASKI ONCE AGAIN.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...DPB
LONG TERM...DPB
AVIATION...
MARINE...DPB
TIDES/COASTAL FLOODING...
AREA FORECAST DISCUSSION
NWS CHARLESTON SC
424 AM EDT MON AUG 19 2013
.SYNOPSIS...
A STATIONARY FRONT OVER THE AREA WILL DISSIPATE AS HIGH PRESSURE
BUILDS WEST ACROSS THE AREA MID TO LATE WEEK. A WEAK TROUGH OF LOW
PRESSURE WILL APPROACH FROM THE NORTHWEST THIS WEEKEND...FOLLOWED BY
HIGH PRESSURE INTO EARLY NEXT WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
PRE-DAWN...A MOIST AND RELATIVELY UNSTABLE AIR MASS ACROSS THE REGION
EARLY THIS MORNING...QUITE TYPICAL FOR THE SEASON. THROUGH DAWN...MOST
AREAS SHOULD REMAIN DRY WITH A FEW SHOWERS POSSIBLE NEAR/ALONG THE
COAST AND ADJACENT TO THE CSRA AREA PRIOR TO DAYBREAK. TEMPS AND DEW
POINTS IN THE MID 70S MOST AREAS.
SOUTHEAST GEORGIA AND SOUTHERN SOUTH CAROLINA WILL REMAIN IN THE
NW FLANKS OF THE ATLC SUBTROPICAL RIDGE TODAY. THE DEPARTING UPPER
TROUGH FROM THE OHIO VALLEY TO THE MID SOUTH REGION IS PROGGED TO
LIFT OUT TO THE NE INTO NEW ENGLAND BY LATE DAY. THE TAIL OF THE MID
LEVEL VORT WILL INDUCE SOME VERY WEAK HEIGHT FALLS OVER THE INLAND
CAROLINAS TODAY WHILE DEEP MID SUMMER MOISTURE PERSISTS REGION-WIDE.
THE OLD WEDGE FRONT CONTINUES TO DECAY OVER THE CAROLINAS TODAY.
FORECAST SOUNDINGS AND 00Z MODEL PROGS INDICATE POTENTIAL FOR
SCATTERED CONVECTIVE RAINS TO DEVELOP OVER THE EASTERN THIRD OF
THE AREA BY MID MORNING ONCE THE LAND MASS BEGINS TO QUICKLY WARM
AND ESPECIALLY SINCE SATELLITE IMAGERY SHOWS STRONG POTENTIAL FOR
DIFFERENTIAL HEATING WITH I-95 THE DIVIDING LINE. CHANCE POPS ARE
EXPECTED TO SPREAD INLAND THIS AFTERNOON WITH MANY AREAS ALONG AND
W OF U.S. 17 EXPECTED TO SEE SCATTERED SHOWERS AND TSTMS. SOME OF
OUR INLAND AREAS COULD SEE SOME VERY HEAVY DOWNPOURS IN DEEP
CONVECTION THIS AFTERNOON. THE LATEST 3KM RAP MODEL INDICATES A
PRETTY COMPLEX MESOSCALE AND THUS EXPECT SOME LOCALLY HEAVY
CONVECTIVE RAINS WILL DEVELOP N OF I-16 AND INLAND FROM U.S. 17
WHERE THE SUBTLE MID LEVEL HEIGHT FALLS OCCUR. WE WILL HIGHLIGHT A
RISK FOR LOCALLY HEAVY DOWNPOURS AND MINOR TEMPORARY FLOODING
CONCERNS FOR OUR NW INLAND ZONES IN OUR HAZARDOUS WEATHER OUTLOOK.
THIS IS MAINLY IN RESPECT TO THE SOGGY SOIL CONDITIONS AND ONGOING
RIVER FLOODING PLUS SWOLLEN TIDAL CREEKS WITH THE FULL MOON CYCLE.
WE RAISED HIGH TEMPS A DEGREE OR SO IN SOME AREAS AS GUIDANCE IS
RUNNING TOO COOL NOW THE WEDGE TO GONE.
&&
.SHORT TERM /TUESDAY THROUGH THURSDAY/...
TUESDAY THROUGH THURSDAY...A TYPICAL SUMMERTIME PATTERN WILL EVOLVE
OVER THE SOUTHEASTERN UNITED STATES AS ATLANTIC HIGH PRESSURE
EXPANDS OVER THE AREA THROUGH MIDWEEK. AS THIS OCCURS...DEEPEST
MOISTURE WILL SHIFT INLAND AND WILL BE THE MAIN SOURCE OF PRECIP
ACTIVITY EACH AFTERNOON WHILE WEAK H5 SHORTWAVES PASS OVERHEAD.
DESPITE THE INLAND SHIFT OF DEEPEST MOISTURE...LIGHT ONSHORE FLOW
WILL SUPPORT PWATS BETWEEN 1.5 TO 2 INCHES AS WELL AS SCATTERED
SHOWERS AND/OR THUNDERSTORMS OVER SOUTHEAST SOUTH CAROLINA AND
SOUTHEAST GEORGIA. HOWEVER...EXPECT MOST SHOWERS/THUNDERSTORMS TO
GRADUALLY SHIFT INLAND BY EARLY AFTERNOON EACH DAY ALONG OR AHEAD A
SEABREEZE.
OVERALL HIGH TEMPS SHOULD RANGE IN THE UPPER 80S TO AROUND 90 EACH
AFTERNOON. OVERNIGHT LOWS WILL RANGE IN THE LOW 70S INLAND TO
MID/UPPER 70S ALONG THE COAST.
&&
.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
A TYPICAL SUMMERTIME PATTERN WILL PERSIST THROUGH LATE WEEK AS
ATLANTIC HIGH PRESSURE REMAINS OVER THE SOUTHEAST. CONDITIONS SHOULD
REMAIN SOMEWHAT DRYER THROUGH FRIDAY WITH WEST/SOUTHWEST FLOW ALOFT.
HIGH PRESSURE WILL THEN GRADUALLY RETREAT SOUTH AND EAST INTO THE
WEEKEND AS A WEAK TROUGH OF LOW PRESSURE APPROACHES FROM THE
NORTHWEST. A SLIGHT CHANCE OF SHOWERS AND/OR THUNDERSTORMS WILL BE
POSSIBLE EACH DAY...WITH POSSIBLY INCREASING CHANCES ON SUNDAY
BEFORE SFC HIGH PRESSURE AND DRYER MID LVL AIR SHIFTS OVER THE
SOUTHEAST INTO EARLY NEXT WEEK. OVERALL HIGH TEMPS SHOULD RANGE IN THE
UPPER 80S TO LOWER 90S EACH AFTERNOON...HIGHEST OVER INLAND AREAS IN
SOUTHEAST GEORGIA. OVERNIGHT LOW TEMPS SHOULD RANGE IN THE LOW 70S
INLAND TO LOW/MID 70S ALONG THE COAST.
&&
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
A MAINLY VFR FORECAST THIS TAF CYCLE AT THE KCHS/KSAV TERMINALS
WITH POTENTIAL FOR BRIEF MVFR CIGS JUST AFTER SUNRISE AS THE LAND
HEATS AND CUMULUS FIELDS DEVELOP. SCATTERED SHOWERS DEVELOPING
THIS MORNING IN THE COASTAL CORRIDOR PER LATEST MODEL OUTPUT...
PUSHING INLAND THIS AFTERNOON. IF DEEPER CONVECTION DEVELOPS IT
COULD SLIDE BACK INTO THE THE TAF CORRIDOR AFTER MID AFTERNOON
AS STEERING FAVORS A SW-NE TRAJECTORY. VCSH THE BEST WE DO FOR
NOW...SIMILAR TO THE LAST PACKAGE.
EXTENDED AVIATION OUTLOOK...VFR CONDITIONS ARE EXPECTED TO PREVAIL
TUESDAY THROUGH SATURDAY AS HIGH PRESSURE PERSISTS OVER THE
SOUTHEAST. BRIEF MVFR CIGS/VSBYS ARE POSSIBLE EACH AFTERNOON WITH
INLAND MOVING SHOWERS AND/OR THUNDERSTORMS.
&&
.MARINE...
ATLC HIGH PRES WILL BE THE MAIN PLAYER FOR THE WATERS. MAINLY A
LIGHT SE TO SSE FLOW THROUGH TONIGHT WITH SEAS 2 TO 3 FT.
TUESDAY THROUGH FRIDAY...WINDS/SEAS ARE EXPECTED TO REMAIN WELL
BELOW SMALL CRAFT ADVISORY LEVELS THROUGH LATE WEEK WITH HIGH
PRESSURE DOMINATING THE WATERS. IN GENERAL...SOUTH TO SOUTHEAST
WINDS WILL REMAIN AT OR BELOW 10-12 KT...HIGHEST NEAR SEABREEZE
CIRCULATIONS ALONG THE COAST. SEAS WILL REMAIN AT OR BELOW
3 FT...HIGHEST IN OUTER GEORGIA WATERS.
WATERSPOUTS...IT IS LOOKING DECENT THIS MORNING GIVEN INSTABILITY
AND LIGHT CHAOTIC WIND FIELDS. WILL BE WAITING FOR SUNRISE TO SPOT
CU LINES AND LAND BREEZE BOUNDARIES BEFORE ISSUING ANY MARINE WEATHER
STATEMENTS.
RIP CURRENTS...A SLIGHT INCREASE IN SWELLS COULD LEAD TO A MODERATE
RISK OF RIPS BY MID WEEK. LOW RISK AT AREA BEACHES TODAY.
&&
.TIDES/COASTAL FLOODING...
GIVEN THE PERIGEAN SPRING TIDES...ADDITIONAL COASTAL FLOOD
ADVISORIES ARE POSSIBLE THROUGH MID-WEEK WITH THE EVENING HIGH
TIDE CYCLE. THIS EVENINGS HIGH TIDE SHORTLY BEFORE SUNSET COULD
PRODUCE SHALLOW COASTAL FLOODING IN DOWNTOWN CHARLESTON AND FORT
PULASKI ONCE AGAIN.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...DPB
LONG TERM...DPB
AVIATION...
MARINE...DPB
TIDES/COASTAL FLOODING...
AREA FORECAST DISCUSSION...UPDATED
NWS PEACHTREE CITY GA
149 AM EDT MON AUG 19 2013
.UPDATE...
/ISSUED AT 940 PM EDT SUN AUG 18 2013/
HAVE ADJUSTED POPS FOR A FEW HOURS BASED ON RADAR. SCATTERED
CONVECTION STILL MOSTLY ACROSS CENTRAL ZONES. WEDGE STILL HOLDING
JUST ABOUT ATLANTA TO ATHENS AND MAY NOT MUCH MUCH MORE OVERNIGHT.
WILL KEEP THE FLASH FLOOD WATCH UNTIL EXPIRATION.
41
.PREVIOUS...
/ISSUED AT 250 PM EDT SUN AUG 18 2013/
.SHORT TERM /TONIGHT THROUGH MONDAY/...
PRIMARY CONCERNS FOR THE SHORT TERM PERIOD WILL BE WHERE MODERATE
TO HEAVY RAIN AXIS SETS UP AND WHAT NEEDS TO BE DONE WITH THE
FLASH FLOOD WATCH AS A RESULT. AFTER A WET START TO THE
DAY...ACTIVITY HAS DWINDLED FOR THE MOST PART WITH JUST SOME
PASSING SHOWERS THROUGH THE ATLANTA METRO NOW HEADING INTO
NORTHEAST GEORGIA. FOCUS NOW SHIFTS TO THE SOUTHEAST WHERE LOCAL
WRF AND HRRR HAVE BEEN BEEN HONING IN ON WITH THUNDERSTORMS
DEVELOPING NICELY OVER THE FAR SOUTHEAST AT THIS HOUR. SPC SREF
SHOWS INSTABILITY INCREASING AS WARM FRONT EASES NORTHWARD WITH
AREAS AROUND TOOMBS AND MONTGOMERY COUNTIES SHOWING IN EXCESS OF
1000 J/KG OF AVAILABLE CAPE. WOULD EXPECT A LINE OF SHOWERS AND
STORMS TO DEVELOP IN THIS AREA AND PROGRESS TOWARD MACON LATER THIS
AFTERNOON INTO THE EVENING. ADDITIONAL ACTIVITY COULD FORM AHEAD
OF THIS AS WELL IN THE MORE UNSTABLE SECTION FROM COLUMBUS TO JUST
SOUTH OF ATHENS.
ALSO WATCHING GULF INITIATED STORMS AS THESE LOOK TO AFFECT THE
SOUTH AS WELL TONIGHT WITH STORMS ALREADY PUSHING INTO THE GEORGIA
PORTION FROM THE FLORIDA PANHANDLE. THERE IS SOME DISPARITY IN
SHORT TERM MODELS ON HOW THIS WILL EVENTUALLY EVOLVE THIS EVENING
WITH NAM12 INDICATING MORE DEVELOPMENT ON THE WESTERN SIDE OF THE
AREA VERSUS THE SOUTH. THIS UNCERTAINTY IS PROBLEMATIC GIVEN THE
FLOOD WATCH ORIENTATION WHICH IS CURRENTLY OVER THE WEST. IF
CURRENT TRENDS HOLD HOWEVER...THE SOUTHERN SECTIONS WOULD BE MORE
UNDER THE GUN. WITH THE UNCERTAINTY INVOLVED...WILL LET THE
EVENING SHIFT TAKE ANOTHER LOOK AT THIS DEVELOPING EVENT TO SEE
IF FLOOD WATCH NEEDS TO CONTINUE AND FOR WHAT AREAS.
FOR MONDAY...PRETTY MUCH THE SAME PATTERN BUT WITH WEDGE
CONTINUING TO WEAKEN AND MORE MOISTURE AVAILABLE FOR THE NORTHERN
ZONES AS WELL AS INSTABILITY. WENT LIKELY FOR MOST
AREAS...FAVORING THE SOUTH ONCE AGAIN...CLOSER TO THE VICINITY OF
STALLED OUT BOUNDARY. STILL USED SOME SLIGHT CAD INFLUENCES FOR
THE HIGH TEMPS MONDAY BUT SHOULD WARM NICELY TO UPPER 70S NORTH TO
LOWER 80S SOUTH.
DEESE
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
/ISSUED AT 250 PM EDT SUN AUG 18 2013/
BUMPED POPS UP SOME INTO THURSDAY TO ACCOUNT FOR THE VERY MOIST
AIRMASS OVER THE AREA. OTHERWISE NO MAJOR CHANGES.
BDL
PREVIOUS DISCUSSION...
THE WET PATTERN CONTINUES INTO THE EXTENDED. THE STATIONARY FRONT
OVER SOUTH GA TODAY WILL MOVE SLOWLY NORTHWARD THROUGH MONDAY AND
SHOULD BE SOME WHERE BETWEEN ATL AND MCN BY TUE MORNING. THIS FRONT
WILL WEAKEN SOME BUT IT WILL STILL ACT AS A GUIDE FOR GULF MOISTURE
TO MOVE NORTHWARD ACROSS THE REGION THROUGH THE MIDDLE OF THE WEEK.
THE WEDGE LOOKS TO FINALLY BREAK DOWN SOMETIME MONDAY WHICH WILL
ALSO ALLOW FOR A MORE DIURNALLY DRIVEN PRECIP PATTERN THROUGH DAY 7.
BEST TIMING FOR THE HEAVIEST RAIN WILL BE IN THE SHORT TERM BUT DEEP
TROPICAL MOISTURE REMAINS OVER THE REGION THROUGH WED/THU WITH
PRECIPITABLE WATERS IN THE 1.5 TO 2.0 INCH RANGE THROUGH THU. THE
DEEPER MOISTURE MOVES NORTH AND EAST OF THE STATE BY THU NIGHT BUT
THE DIURNAL CONVECTIVE TREND WILL CONTINUE INTO NEXT WEEKEND. TEMPS
WILL BEGIN TO REBOUND BY TUE AND BE BACK TO NEAR SEASONAL NORMS BY
THU/FRI.
01
&&
.AVIATION...
06Z UPDATE...
FRONTAL BOUNDARY JUST SOUTH OF ATL SHOULD REMAIN THERE TONIGHT...
THEN DRIFT NORTH OF ATL MON AFTERNOON. LIGHT EAST WINDS WILL PERSIST
TONIGHT...THEN BECOME MORE SE BY MON AFTERNOON AT 7-9KTS. EXPECT
IFR/LIFR CIGS TO PREVAIL AGAIN TONIGHT WITH -DZ/BR RESTRICTING VSBY
DOWN TO 1-3SM AT TIMES. CIGS GRADUALLY IMPROVE TO MVFR BY 15Z...THEN
POSSIBLY LOW VFR LEVELS BY 17-19Z MON AS THE WARM FRONT DRIFTS
NORTH. MODELS SHOW SCT -SHRA/-TSRA AROUND BY MON AFTERNOON SO WILL
INCLUDE A PROB30 -TSRA 20-24Z MON AS ATL GETS IN THE WARM SECTOR.
//ATL CONFIDENCE...06Z UPDATE...
MEDIUM ON ALL ELEMENTS
39
&&
.PRELIMINARY POINT TEMPS/POPS...
ATHENS 69 81 69 79 / 50 60 50 70
ATLANTA 69 79 70 79 / 70 50 40 60
BLAIRSVILLE 65 76 66 78 / 70 50 50 60
CARTERSVILLE 69 79 69 78 / 70 50 50 60
COLUMBUS 71 83 72 85 / 50 60 40 70
GAINESVILLE 68 78 69 76 / 70 50 50 70
MACON 70 82 70 82 / 40 60 40 60
ROME 69 80 70 80 / 70 50 50 60
PEACHTREE CITY 70 80 71 79 / 60 50 40 60
VIDALIA 72 86 72 86 / 40 60 40 40
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR THE FOLLOWING
ZONES: BARTOW...BIBB...BLECKLEY...BUTTS...CARROLL...CATOOSA...
CHATTAHOOCHEE...CHATTOOGA...CHEROKEE...CLAYTON...COBB...COWETA...
CRAWFORD...CRISP...DADE...DEKALB...DODGE...DOOLY...DOUGLAS...
FANNIN...FAYETTE...FLOYD...GILMER...GORDON...HARALSON...HARRIS...
HEARD...HENRY...HOUSTON...LAMAR...MACON...MARION...MERIWETHER...
MONROE...MURRAY...MUSCOGEE...NORTH FULTON...PAULDING...PEACH...
PICKENS...PIKE...POLK...PULASKI...ROCKDALE...SCHLEY...SOUTH
FULTON...SPALDING...STEWART...SUMTER...TALBOT...TAYLOR...
TELFAIR...TROUP...TWIGGS...UPSON...WALKER...WEBSTER...
WHITFIELD...WILCOX.
&&
$$
SHORT TERM...DEESE
LONG TERM....BDL
AVIATION...39
AREA FORECAST DISCUSSION
NWS POCATELLO ID
222 PM MDT MON AUG 19 2013
.DISCUSSION...STRONG UPPER LOW REMAINS OFF CALIFORNIA COAST WITH
MOISTURE STREAMING NORTH THROUGH GREAT BASIN. SHORTWAVE AXIS HAS
MOVED THROUGH PANHANDLE INTO MONTANA EARLY THIS AFTERNOON...WHICH
HAS KEPT MOISTURE SURGE LIMITED. CONVECTION SO FAR LIMITED TO
AREAS SOUTH OF STATE LINE BUT HAVE LEFT WEAK POPS NORTH OF BORDER
INTO SOUTHERN HIGHLANDS FOR OVERNIGHT. HRRR PUSHES CONVECTION
NORTH INTO THE REGION BY LATE AFTERNOON THEN SLOWLY SPREADS
NORTHEAST AFTER MIDNIGHT. GFS LENDS SUPPORT TO THIS IDEA BUT NAM
LESS SO. MOISTURE SURGE CONTINUES INTO MIDWEEK WITH STRONG
GRADIENT LAYING ACROSS EASTERN IDAHO MIDDAY TUESDAY...THEN
GRADIENT PUSHING WELL NORTH OF FORECAST AREA FOR WEDNESDAY AND
BEYOND. STILL SOME QUESTION AS TO HOW FAR NORTH CONVECTION WILL
PUSH ON TUESDAY AFTERNOON WITH SUBSEQUENT IMPACT ON FIRE
HEADLINES. SEE DISCUSSION BELOW. OTHERWISE BEST CHANCE FOR
SIGNIFICANT COVERAGE OF STORMS APPEARS TO BE ON WEDNESDAY WITH PW
OVER AN INCH MOST AREAS. COULD SEE LOCALLY HEAVY RAINFALL AND WILL
NOT BE SURPRISED IF FLASH FLOOD WATCH MAY BE NECESSARY IN ADDITION
TO RED FLAG FOR FIRE CONCERNS...ESPECIALLY IN VICINITY OF RECENT
BURN SCARS LIKE BEAVER CREEK/LODGEPOLE/STATE FIRES IN
URBAN/WILDLAND INTERFACE AREAS. BOTH GFS AND ECMWF CONTINUE IDEA
OF WEAKENING UPPER LOW WEDNESDAY NIGHT INTO THURSDAY AND EJECTING
LOW NORTHEAST THROUGH PACNW/PANHANDLE ON FRIDAY. SOME IDEA OF A
DRY SLOT ON FRIDAY...THEN SOUTH FLOW CONTINUES THROUGH THE GREAT
BASIN INTO EASTERN IDAHO THROUGH THE REMAINDER OF THE WEEKEND WITH
STRONG HIGH OVER GREAT PLAINS AND AMPLIFYING TROUGH JUST OFF
PACIFIC COAST. WILL KEEP SOME MENTION OF THUNDERSTORMS OVER HIGHER
ELEVATIONS FRIDAY THROUGH THE WEEKEND. DMH
&&
.AVIATION...SMOKE AT KSUN WILL CONTINUE TO BE THE GREATEST IMPACT.
LOOK FOR IFR VISIBILITIES AGAIN TONIGHT THROUGH TOMORROW MORNING.
LOOK FOR ISOLATED THUNDERSTORMS ACROSS OUR SOUTHERN AREAS LATE THIS
AFTERNOON INTO EARLY EVENING BRINGING VICINITY THUNDERSTORMS FOR
KBYI AND TO AN LESSER EXTENT KPIH. TOMORROW AFTERNOON LOOK FOR A
BETTER CHANCE FOR VICINITY THUNDERSTORMS PARTICULARLY FOR KBYI AND
KSUN. WYATT
&&
.FIRE WEATHER...A RED FLAG HAS BEEN CONTINUED FOR ZONE 475 THROUGH
EARLY THIS EVENING. RELATIVE HUMIDITY HAS ALREADY GONE BELOW 15 PERCENT
WITH WINDS IN THE UPPER TEENS TO LOWER TWENTIES. FIRE ZONES 422 AND
475 ARE RUNNING SLIGHTLY STRONGER WINDS BUT HAVE SLIGHTLY HIGHER
RELATIVE HUMIDITY WITH MOISTURE MOVING UP FROM THE SOUTH. EXPECT
AFTERNOON ISOLATED THUNDERSTORMS ACROSS THE SOUTHERN HIGHLANDS
TODAY. A FIRE WEATHER WATCH FOR SCATTERED SHOWERS AND THUNDERSTORMS
IS CONTINUED FOR TUESDAY AFTERNOON THROUGH THURSDAY. HAVE HELD OFF
ON UPGRADING TO A RED FLAG FOR TUESDAY AS IT LOOKS MARGINAL FOR
SCATTERED AFTERNOON THUNDERSTORMS AT THIS POINT. WEDNESDAY AND
THURSDAY AFTERNOONS STILL LOOK LIKE A RED FLAG WARNING WILL BE
NEEDED FOR SCATTERED TO NUMEROUS THUNDERSTORMS. A FLASH FLOOD WATCH
FOR WEDNESDAY AFTERNOON MAY BE NEEDED AS WELL FOR THE MOUNTAIN ZONES
PARTICULARLY FOR RECENT BURN AREAS. MODELS SHOW SLIGHT THUNDERSTORM
CHANCES FOR OUR NORTHERN AREAS FRIDAY AFTERNOON IN SOUTHWEST FLOW.
SATURDAY LOOKS SLIGHTLY DRIER BEFORE ANOTHER SYSTEM STARTS TO
APPROACH THE AREA BRINGING BACK BETTER PRECIPITATION CHANCES FOR
SUNDAY AND MONDAY. WYATT
&&
.AIR STAGNATION...AREAS OF SMOKE WILL REMAIN IN THE FORECAST OVER
THE CENTRAL MOUNTAINS WHILE LARGE FIRES CONTINUE TO BURN.
INCREASING MOISTURE OVER THE NEXT FEW DAYS WILL ALLOW
THUNDERSTORMS TO FORM. OVERALL IMPACT TOUGH TO SAY WITH POTENTIAL
FOR BOTH NEW STARTS DUE TO LIGHTNING AND LOCALLY HEAVY RAIN WHICH
MAY HELP CURRENT FIRE SITATION. IDAHO DEQ HAS LIFTED AIR QUALITY
STATEMENT FOR CUSTER COUNTY WHILE CONTINUING FOR BLAINE AND HAVE
ISSUED UPDATED STATEMENTS. DMH
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
FIRE WEATHER WATCH FROM TUESDAY AFTERNOON THROUGH THURSDAY
EVENING IDZ413-427.
FIRE WEATHER WATCH FROM TUESDAY AFTERNOON THROUGH THURSDAY
EVENING IDZ410-425.
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING IDZ475.
FIRE WEATHER WATCH FROM TUESDAY AFTERNOON THROUGH THURSDAY
EVENING IDZ422-475-476.
&&
$$
AREA FORECAST DISCUSSION
NWS GOODLAND KS
208 PM MDT MON AUG 19 2013
.SHORT TERM...(TONIGHT THROUGH TUESDAY AFTERNOON)
ISSUED AT 203 PM MDT MON AUG 19 2013
AS OF 3 PM CDT...2 PM MDT...SKIES ACROSS THE TRI-STATE AREA WERE
CLEAR. TEMPERATURES HAVE RESPONDED NICELY WITH THE LACK OF CLOUD
COVER AND RANGED FROM THE MID 80S TO LOW 90S. WINDS WERE FROM THE
SOUTHEAST AT 10 TO 15 MPH WITH GUSTS TO 20 MPH. THE RIDGE OF HIGH
PRESSURE OVER THE SOUTHWEST HAS STRENGTHENED SOME TODAY. SUBSIDENCE
ALOFT WAS ENTRENCHED OVER THE REGION AT THIS TIME.
FOR THE REST OF TODAY AND TONIGHT...WITH THE INFLUENCE OF THE RIDGE
AND SUBSIDENCE ALOFT FIRMLY IN PLACE...PRECIPITATION CHANCES WILL BE
NEAR ZERO. THE HRRR KEEPS SUGGESTING A ISOLATED SHOWER OR STORM IS
POSSIBLE OVER CHEYENNE COUNTY COLORADO BUT NO OTHER MODEL IS
PRODUCING PRECIPITATION OVER THE FORECAST AREA. TEMPERATURES FOR
TONIGHT ARE EXPECTED TO FALL INTO THE LOW 60S UNDER MOSTLY CLEAR
SKIES. LIGHT WINDS AND SOME LINGERING LOW LEVEL MOISTURE MAY ALLOW
FOR SOME PATCHY LIGHT FOG TO FORM...MAINLY ACROSS SOUTHWEST
NEBRASKA. DID NOT THINK THIS WAS WORTHY OF A MENTION IN THE GRIDS AS
VISIBILITIES SHOULD NOT FALL LOWER THAN 4 MILES AT WORSE.
FOR TOMORROW...THE RIDGE OF HIGH PRESSURE WILL STRENGTHEN SLIGHTLY
AGAIN. MODELS PROJECT THAT 850 MB TEMPERATURES WILL WARM A DEGREE OR
TWO OVER TODAYS 850 TEMPS SO A SIMILAR RESPONSE IS EXPECTED IN
SURFACE TEMPERATURES. AS A RESULT...HIGH TEMPERATURES IN THE MID TO
UPPER 90S ARE FORECAST UNDER CLEAR SKIES. SOUTH TO SOUTHEAST WINDS
WILL CONTINUE AS A LEE TROUGH TO THE WEST WILL CONTINUE TO INFLUENCE
THE LOW LEVEL FLOW. BASED ON THE UPPER LEVEL PATTERN AND THE LACK OF
A STRONG DISTURBANCE...PRECIPITATION IS NOT FORECAST FOR TOMORROW.
.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 203 PM MDT MON AUG 19 2013
THE UPPER HIGH CURRENTLY OVER COLORADO/ARIZONA IS FORECAST TO
MOVE EAST TO KANSAS/OKLAHOMA BY THE END OF THE WEEK AND
ULTIMATELY WIND UP OVER ILLINOIS BY THE END OF THE PERIOD. THIS
WILL BE THE PRIMARY FEATURE AFFECTING THE WEATHER...AND IN GENERAL
THIS WILL TRANSLATE INTO A WARM AND DRY PERIOD FOR THE FORECAST
AREA.
ONE POSSIBLE CAVEAT TO THE DRY SCENARIO MENTIONED ABOVE WILL BE A
WEAK SHORT WAVE TROUGH FORECAST BY THE NAM AND GFS TO RIDE OVER
THE TOP OF THE RIDGE WEDNESDAY NIGHT. BOTH MODELS INDICATE A
CHANCE FOR SCATTERED CONVECTION WED NIGHT WHILE THE ECMWF KEEPS
THINGS DRY AND THE GEM SHOWS CONVECTION JUST NORTH OF THE AREA.
FOR NOW HAVE KEPT PREVIOUS FORECAST OF LOW CHANCE POPS DURING THIS
TIME WITH AN EMPHASIS ON THE NORTHWEST AND CENTRAL COUNTIES.
TEMPERATURES WILL BE ABOVE NORMAL IN THE LOW-MID 90S FOR MUCH OF
THE PERIOD WHICH IS 5-8 DEGREES ABOVE NORMAL...WHILE LOWS REMAIN
GENERALLY IN THE 60S.
AT THE END OF THE PERIOD AND INTO THE MIDDLE OF NEXT WEEK WHEN THE
UPPER HIGH HAS SHIFTED EAST...THERE WILL BE AN INCREASING WINDOW
OF OPPORTUNITY FOR SCATTERED CONVECTION AS THE AREA COMES UNDER
MORE OF A WEAK SOUTHWEST FLOW ALOFT. UNTIL THEN...PRECIP CHANCES
LOOK MEAGER.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1125 AM MDT MON AUG 19 2013
AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL CONTINUE TO DOMINATE
THE WEATHER PATTERN FOR THE NEXT 24 HOURS. THIS RIDGE SHOULD
SUPPRESS ANY POSSIBLE SHOWER OR THUNDERSTORM ACTIVITY. A SLIGHT
DECREASE IN LOW LEVEL MOISTURE IS EXPECTED TONIGHT AND WITH DRIER
AIR ALOFT. THINKING THAT FOG CHANCES ARE TOO SMALL TO MENTION IN
THE KGLD TAF. FOG WAS INDICATED IN THE MAV...MET AND LAV GUIDANCE
FOR KMCK SO HAVE INTRODUCED A BRIEF PERIOD OF MVFR VISIBILITIES.
LIGHT SOUTH WINDS WILL CONTINUE THROUGHOUT THE TAF PERIOD.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...RRH
LONG TERM...DLF
AVIATION...RRH
AREA FORECAST DISCUSSION
NWS GOODLAND KS
205 PM MDT MON AUG 19 2013
.SHORT TERM...(TONIGHT THORUGH TUESDAY AFTERNOON)
ISSUED AT 203 PM MDT MON AUG 19 2013
AS OF 3 PM CDT...2 PM MDT...SKIES ACROSS THE TRI-STATE AREA WERE
CLEAR. TEMPERATURES HAVE RESPONDED NICELY WITH THE LACK OF CLOUD
COVER AND RANGED FROM THE MID 80S TO LOW 90S. WINDS WERE FROM THE
SOUTHEAST AT 10 TO 15 MPH WITH GUSTS TO 20 MPH. THE RIDGE OF HIGH
PRESSURE OVER THE SOUTHWEST HAS STRENGTHENED SOME TODAY. SUBSIDENCE
ALOFT WAS ENTRENCHED OVER THE REGION AT THIS TIME.
FOR THE REST OF TODAY AND TONIGHT...WITH THE INFLUENCE OF THE RIDGE
AND SUBSIDENCE ALOFT FIRMLY IN PLACE...PRECIPITATION CHANCES WILL BE
NEAR ZERO. THE HRRR KEEPS SUGGESTING A ISOLATED SHOWER OR STORM IS
POSSIBLE OVER CHEYENNE COUNTY COLORADO BUT NO OTHER MODEL IS
PRODUCING PRECIPITATION OVER THE FORECAST AREA. TEMPERATURES FOR
TONIGHT ARE EXPECTED TO FALL INTO THE LOW 60S UNDER MOSTLY CLEAR
SKIES. LIGHT WINDS AND SOME LINGERING LOW LEVEL MOISTURE MAY ALLOW
FOR SOME PATCHY LIGHT FOG TO FORM...MAINLY ACROSS SOUTHWEST
NEBRASKA. DID NOT THINK THIS WAS WORTHY OF A MENTION IN THE GRIDS AS
VISIBILITIES SHOULD NOT FALL LOWER THAN 4 MILES AT WORSE.
FOR TOMORROW...THE RIDGE OF HIGH PRESSURE WILL STRENGTHEN SLIGHTLY
AGAIN. MODELS PROJECT THAT 850 MB TEMPERATURES WILL WARM A DEGREE OR
TWO OVER TODAYS 850 TEMPS SO A SIMILAR RESPONSE IS EXPECTED IN
SURFACE TEMPERATURES. AS A RESULT...HIGH TEMPERATURES IN THE MID TO
UPPER 90S ARE FORECAST UNDER CLEAR SKIES. SOUTH TO SOUTHEAST WINDS
WILL CONTINUE AS A LEE TROUGH TO THE WEST WILL CONTINUE TO INFLUENCE
THE LOW LEVEL FLOW. BASED ON THE UPPER LEVEL PATTERN AND THE LACK OF
A STRONG DISTURBANCE...PRECIPITATION IS NOT FORECAST FOR TOMORROW.
.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 203 PM MDT MON AUG 19 2013
THE UPPER HIGH CURRENTLY OVER COLORADO/ARIZONA IS FORECAST TO
MOVE EAST TO KANSAS/OKLAHOMA BY THE END OF THE WEEK AND
ULTIMATELY WIND UP OVER ILLINOIS BY THE END OF THE PERIOD. THIS
WILL BE THE PRIMARY FEATURE AFFECTING THE WEATHER...AND IN GENERAL
THIS WILL TRANSLATE INTO A WARM AND DRY PERIOD FOR THE FORECAST
AREA.
ONE POSSIBLE CAVEAT TO THE DRY SCENARIO MENTIONED ABOVE WILL BE A
WEAK SHORT WAVE TROUGH FORECAST BY THE NAM AND GFS TO RIDE OVER
THE TOP OF THE RIDGE WEDNESDAY NIGHT. BOTH MODELS INDICATE A
CHANCE FOR SCATTERED CONVECTION WED NIGHT WHILE THE ECMWF KEEPS
THINGS DRY AND THE GEM SHOWS CONVECTION JUST NORTH OF THE AREA.
FOR NOW HAVE KEPT PREVIOUS FORECAST OF LOW CHANCE POPS DURING THIS
TIME WITH AN EMPHASIS ON THE NORTHWEST AND CENTRAL COUNTIES.
TEMPERATURES WILL BE ABOVE NORMAL IN THE LOW-MID 90S FOR MUCH OF
THE PERIOD WHICH IS 5-8 DEGREES ABOVE NORMAL...WHILE LOWS REMAIN
GENERALLY IN THE 60S.
AT THE END OF THE PERIOD AND INTO THE MIDDLE OF NEXT WEEK WHEN THE
UPPER HIGH HAS SHIFTED EAST...THERE WILL BE AN INCREASING WINDOW
OF OPPORTUNITY FOR SCATTERED CONVECTION AS THE AREA COMES UNDER
MORE OF A WEAK SOUTHWEST FLOW ALOFT. UNTIL THEN...PRECIP CHANCES
LOOK MEAGER.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1125 AM MDT MON AUG 19 2013
AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL CONTINUE TO DOMINATE
THE WEATHER PATTERN FOR THE NEXT 24 HOURS. THIS RIDGE SHOULD
SUPPRESS ANY POSSIBLE SHOWER OR THUNDERSTORM ACTIVITY. A SLIGHT
DECREASE IN LOW LEVEL MOISTURE IS EXPECTED TONIGHT AND WITH DRIER
AIR ALOFT. THINKING THAT FOG CHANCES ARE TOO SMALL TO MENTION IN
THE KGLD TAF. FOG WAS INDICATED IN THE MAV...MET AND LAV GUIDANCE
FOR KMCK SO HAVE INTRODUCED A BRIEF PERIOD OF MVFR VISIBILITIES.
LIGHT SOUTH WINDS WILL CONTINUE THROUGHOUT THE TAF PERIOD.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...RRH
LONG TERM...DLF
AVIATION...RRH
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
132 PM EDT Mon Aug 19 2013
...Updated Aviation Discussion...
...Forecast Update...
Issued at 1107 AM EDT Mon Aug 19 2013
Fog continues to mix out across the southern forecast area this
morning. In most locations, the fog has transitioned over to a low
stratus deck which will take some time to mix out more fully. We
expect that to occur around lunch time or early this afternoon. Cu
field has become better defined across southern KY this morning
despite having a bit more capping aloft. A few isolated showers
will be possible mainly along and SE of the BG Parkway. Additional
isolated showers/storms will be possible later this afternoon.
Forcing is fairly weak from a dynamical standpoint, but differential
heating is probably going to be main forcing mechanism this
afternoon. Temperatures are currently in the lower 70s across the
south, with a belt of mid-upper 70s along and just north of the Ohio
River. Obviously the thicker cloud cover to the south will augment
the solar insolation a bit this afternoon which will likely lead to
a N-S temperature gradient. Highs in the 80-85 degree range in
areas from the KY Parkways and northward still look good. Lower 80s
down across the south and southeastern sections are still
attainable, but will probably occur a little later in the afternoon
due to the cloud cover delaying insolation.
Update issued at 530 AM EDT Mon Aug 19 2013
Updated the forecast to remove areas of fog with patchy dense fog
from southeast Indiana and the Bluegrass region of KY. Mid level
clouds and lesser low level moisture than central and southern KY
(where patches of dense fog have been reported) have limited fog
formation over southeast Indiana and the Bluegrass. Downgraded this
area to just patchy fog for the rest of the pre-dawn hours.
Issued an SPS for portions of south and central KY where patchy
dense fog has been reported and where it rained yesterday (which
should be fog prone). Few-sct mid level clouds continue to move
over this area improving fog at times so feel dense fog coverage
will remain patchy.
.SHORT TERM (Now through Tuesday)...
Issued at 330 AM EDT Mon Aug 19 2013
The main forecast concern in the short term will be fog this
morning. A very moist low level atmosphere along with very light or
nearly calm winds have created an ideal environment for fog
formation which we`ve already seen develop in our area. The worst
fog spots remain over southern IL/western KY and over southwest
Ohio. The 5Z RAP model has these fog areas handled well and expect
them to expand into central KY and portions of southeast IN. Low
clouds will also accompany the fog as soundings indicate a shallow
layer of trapped moisture under a weak inversion. With these
thoughts in mind, think that most locations over southern IN and
central KY will see areas of fog this morning. Some locations over
central KY and southeast IN will probably see patches of dense fog
as well assuming the low clouds don`t inhibit fog density too much.
Will highlight the patchy dense fog in the HWO this morning and
monitor closely in case it becomes more widespread and an SPS or
dense fog advisory is need.
For the rest of the day, fog should burn off fairly quickly after
sunrise. With an upper trough passing through the region, can`t
rule out an isld shower over portions of south and east central KY.
However, did scale the area of potential precip back a bit. High
temperatures should reach the low to mid 80s this afternoon.
Tonight a second upper trough will settle into the mid Mississippi
River Valley. Some fog may be possible but not as widespread as
this morning. Will continue inherited patchy fog mainly in river
valleys. Lows tonight will be in the mid 60s.
For Tues, expect a 20% chance of showers/t-storms to expand from
south to north over the area throughout the day as a vort wave on
the eastern side of the upper trough push north through our area.
Any convection would be on the weak side. Tuesday afternoon high
temps should be in the low to mid 80s with southern Indiana being
the hottest due to a longer period of sunshine before clouds/isld
convection move in.
.LONG TERM (Tuesday Night through Sunday)...
Issued at 311 AM EDT Mon Aug 19 2013
The models have finally come into agreement with a mid-level low
that forms over the Ohio Valley at the start of this forecast
period. This cutoff low hangs out in the region through Thursday
night when it undergoes a transformation into an open wave in
response to an approaching shortwave. This shortwave rides around
the periphery of a stout ridge building in over the Plains and looks
to exit the forecast area by early Saturday. The ridge continues to
build in from the west, giving us dry conditions through the end of
the weekend and into early next week.
Tuesday night through Thursday:
For this issuance, have introduced slight chance PoPs for Tuesday
night as the low establishes itself overhead and surface southerly
flow allows for moisture to be pulled in. Chance PoPs continues for
Wednesday as daytime heating assists in convection across the area.
With the loss of daytime heating and in conjunction with general
model consensus, have kept PoPs out overnight Wednesday into early
Thursday. As the low is depicted to begin traversing eastward
Thursday, have only slight chance during the day with the primary
focus for possible convection more toward eastern KY. The models
have the low slowly but surely progressing eastward during this time
frame and am a little skeptical on its speed. How quickly the low
exits will depend on the timing of a weak frontal boundary
attempting to lay out across the southern Great Lakes by Thursday
night.
Thursday night through Friday night:
Have gone with slight chance PoPs strictly across the northern
sections as the alluded to frontal boundary approaches from the
north. The front stalls well to our north and does not currently
appear to be a factor for us beyond Friday. The aforementioned
shortwave swings around the region Friday, hence the slight to
chance PoPs under diurnally-driven conditions. Again, skepticism
sets in for the timing of it all as it seems to really move through
a little too quickly. For now, have kept the area dry Friday night
until a better handle on the progression of everything plays out.
Temperatures will be more difficult to predict Tuesday night through
Friday night as cloudy skies and/or rain will obviously wreck havoc.
What can be said with confidence is that highs will continue to run
slightly below normal and lows will flirt with normal.
Saturday through Sunday:
With that ridge building in, we`ll begin to see real signs of summer
return as temperatures look to rebound back toward normal and partly
to mostly sunny skies prevail.
&&
.AVIATION (18Z TAF Update)...
Issued at 131 PM EDT Mon Aug 19 2013
VFR conditions are expected through much of the period. Some
scattered showers and storms will be possible this afternoon across
the Bluegrass region that could affect the KLEX area. For now, will
carry a VCSH group through the afternoon. Surface winds are
expected to be light and variable. VFR conditions are expected this
evening and into the overnight period. However, guidance suggests
fog is likely again at KBWG and KLEX, so will carry some tempo IFR
vsbys between 20/08-12Z at KBWG and KLEX. KSDF should remain VFR
overnight with some patchy haze possible toward 20/12Z.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
Update.........MJ
Short Term.....AMS
Long Term......lg
Aviation.......MJ
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
1109 AM EDT Mon Aug 19 2013
...Forecast Update...
Issued at 1107 AM EDT Mon Aug 19 2013
Fog continues to mix out across the southern forecast area this
morning. In most locations, the fog has transitioned over to a low
stratus deck which will take some time to mix out more fully. We
expect that to occur around lunch time or early this afternoon. Cu
field has become better defined across southern KY this morning
despite having a bit more capping aloft. A few isolated showers
will be possible mainly along and SE of the BG Parkway. Additional
isolated showers/storms will be possible later this afternoon.
Forcing is fairly weak from a dynamical standpoint, but differential
heating is probably going to be main forcing mechanism this
afternoon. Temperatures are currently in the lower 70s across the
south, with a belt of mid-upper 70s along and just north of the Ohio
River. Obviously the thicker cloud cover to the south will augment
the solar insolation a bit this afternoon which will likely lead to
a N-S temperature gradient. Highs in the 80-85 degree range in
areas from the KY Parkways and northward still look good. Lower 80s
down across the south and southeastern sections are still
attainable, but will probably occur a little later in the afternoon
due to the cloud cover delaying insolation.
Update issued at 530 AM EDT Mon Aug 19 2013
Updated the forecast to remove areas of fog with patchy dense fog
from southeast Indiana and the Bluegrass region of KY. Mid level
clouds and lesser low level moisture than central and southern KY
(where patches of dense fog have been reported) have limited fog
formation over southeast Indiana and the Bluegrass. Downgraded this
area to just patchy fog for the rest of the pre-dawn hours.
Issued an SPS for portions of south and central KY where patchy
dense fog has been reported and where it rained yesterday (which
should be fog prone). Few-sct mid level clouds continue to move
over this area improving fog at times so feel dense fog coverage
will remain patchy.
.SHORT TERM (Now through Tuesday)...
Issued at 330 AM EDT Mon Aug 19 2013
The main forecast concern in the short term will be fog this
morning. A very moist low level atmosphere along with very light or
nearly calm winds have created an ideal environment for fog
formation which we`ve already seen develop in our area. The worst
fog spots remain over southern IL/western KY and over southwest
Ohio. The 5Z RAP model has these fog areas handled well and expect
them to expand into central KY and portions of southeast IN. Low
clouds will also accompany the fog as soundings indicate a shallow
layer of trapped moisture under a weak inversion. With these
thoughts in mind, think that most locations over southern IN and
central KY will see areas of fog this morning. Some locations over
central KY and southeast IN will probably see patches of dense fog
as well assuming the low clouds don`t inhibit fog density too much.
Will highlight the patchy dense fog in the HWO this morning and
monitor closely in case it becomes more widespread and an SPS or
dense fog advisory is need.
For the rest of the day, fog should burn off fairly quickly after
sunrise. With an upper trough passing through the region, can`t
rule out an isld shower over portions of south and east central KY.
However, did scale the area of potential precip back a bit. High
temperatures should reach the low to mid 80s this afternoon.
Tonight a second upper trough will settle into the mid Mississippi
River Valley. Some fog may be possible but not as widespread as
this morning. Will continue inherited patchy fog mainly in river
valleys. Lows tonight will be in the mid 60s.
For Tues, expect a 20% chance of showers/t-storms to expand from
south to north over the area throughout the day as a vort wave on
the eastern side of the upper trough push north through our area.
Any convection would be on the weak side. Tuesday afternoon high
temps should be in the low to mid 80s with southern Indiana being
the hottest due to a longer period of sunshine before clouds/isld
convection move in.
.LONG TERM (Tuesday Night through Sunday)...
Issued at 311 AM EDT Mon Aug 19 2013
The models have finally come into agreement with a mid-level low
that forms over the Ohio Valley at the start of this forecast
period. This cutoff low hangs out in the region through Thursday
night when it undergoes a transformation into an open wave in
response to an approaching shortwave. This shortwave rides around
the periphery of a stout ridge building in over the Plains and looks
to exit the forecast area by early Saturday. The ridge continues to
build in from the west, giving us dry conditions through the end of
the weekend and into early next week.
Tuesday night through Thursday:
For this issuance, have introduced slight chance PoPs for Tuesday
night as the low establishes itself overhead and surface southerly
flow allows for moisture to be pulled in. Chance PoPs continues for
Wednesday as daytime heating assists in convection across the area.
With the loss of daytime heating and in conjunction with general
model consensus, have kept PoPs out overnight Wednesday into early
Thursday. As the low is depicted to begin traversing eastward
Thursday, have only slight chance during the day with the primary
focus for possible convection more toward eastern KY. The models
have the low slowly but surely progressing eastward during this time
frame and am a little skeptical on its speed. How quickly the low
exits will depend on the timing of a weak frontal boundary
attempting to lay out across the southern Great Lakes by Thursday
night.
Thursday night through Friday night:
Have gone with slight chance PoPs strictly across the northern
sections as the alluded to frontal boundary approaches from the
north. The front stalls well to our north and does not currently
appear to be a factor for us beyond Friday. The aforementioned
shortwave swings around the region Friday, hence the slight to
chance PoPs under diurnally-driven conditions. Again, skepticism
sets in for the timing of it all as it seems to really move through
a little too quickly. For now, have kept the area dry Friday night
until a better handle on the progression of everything plays out.
Temperatures will be more difficult to predict Tuesday night through
Friday night as cloudy skies and/or rain will obviously wreck havoc.
What can be said with confidence is that highs will continue to run
slightly below normal and lows will flirt with normal.
Saturday through Sunday:
With that ridge building in, we`ll begin to see real signs of summer
return as temperatures look to rebound back toward normal and partly
to mostly sunny skies prevail.
&&
.AVIATION (12Z TAF Update)...
Issued at 635 AM EDT Mon Aug 19 2013
While VLIFR conditions exist at BWG, vsbys/cigs at SDF/LEX have not
been near as bad as originally thought thanks to a persistent mid
level cloud deck overnight. So for the rest of the day, expect VFR
conditions at all TAF sites after fog burns off at BWG within the
next few hours. Winds will be light out of the ENE throughout the
TAF period. BWG will once again be fog prone tomorrow morning, but
it should not be as dense as this morning`s fog.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
Update.........MJ
Short Term.....AMS
Long Term......lg
Aviation.......AMS
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
702 AM EDT Mon Aug 19 2013
...Updated Aviation Discussion...
...Forecast Update...
Issued at 530 AM EDT Mon Aug 19 2013
Updated the forecast to remove areas of fog with patchy dense fog
from southeast Indiana and the Bluegrass region of KY. Mid level
clouds and lesser low level moisture than central and southern KY
(where patches of dense fog have been reported) have limited fog
formation over southeast Indiana and the Bluegrass. Downgraded this
area to just patchy fog for the rest of the pre-dawn hours.
Issued an SPS for portions of south and central KY where patchy
dense fog has been reported and where it rained yesterday (which
should be fog prone). Few-sct mid level clouds continue to move
over this area improving fog at times so feel dense fog coverage
will remain patchy.
.SHORT TERM (Now through Tuesday)...
Issued at 330 AM EDT Mon Aug 19 2013
The main forecast concern in the short term will be fog this
morning. A very moist low level atmosphere along with very light or
nearly calm winds have created an ideal environment for fog
formation which we`ve already seen develop in our area. The worst
fog spots remain over southern IL/western KY and over southwest
Ohio. The 5Z RAP model has these fog areas handled well and expect
them to expand into central KY and portions of southeast IN. Low
clouds will also accompany the fog as soundings indicate a shallow
layer of trapped moisture under a weak inversion. With these
thoughts in mind, think that most locations over southern IN and
central KY will see areas of fog this morning. Some locations over
central KY and southeast IN will probably see patches of dense fog
as well assuming the low clouds don`t inhibit fog density too much.
Will highlight the patchy dense fog in the HWO this morning and
monitor closely in case it becomes more widespread and an SPS or
dense fog advisory is need.
For the rest of the day, fog should burn off fairly quickly after
sunrise. With an upper trough passing through the region, can`t
rule out an isld shower over portions of south and east central KY.
However, did scale the area of potential precip back a bit. High
temperatures should reach the low to mid 80s this afternoon.
Tonight a second upper trough will settle into the mid Mississippi
River Valley. Some fog may be possible but not as widespread as
this morning. Will continue inherited patchy fog mainly in river
valleys. Lows tonight will be in the mid 60s.
For Tues, expect a 20% chance of showers/t-storms to expand from
south to north over the area throughout the day as a vort wave on
the eastern side of the upper trough push north through our area.
Any convection would be on the weak side. Tuesday afternoon high
temps should be in the low to mid 80s with southern Indiana being
the hottest due to a longer period of sunshine before clouds/isld
convection move in.
.LONG TERM (Tuesday Night through Sunday)...
Issued at 311 AM EDT Mon Aug 19 2013
The models have finally come into agreement with a mid-level low
that forms over the Ohio Valley at the start of this forecast
period. This cutoff low hangs out in the region through Thursday
night when it undergoes a transformation into an open wave in
response to an approaching shortwave. This shortwave rides around
the periphery of a stout ridge building in over the Plains and looks
to exit the forecast area by early Saturday. The ridge continues to
build in from the west, giving us dry conditions through the end of
the weekend and into early next week.
Tuesday night through Thursday:
For this issuance, have introduced slight chance PoPs for Tuesday
night as the low establishes itself overhead and surface southerly
flow allows for moisture to be pulled in. Chance PoPs continues for
Wednesday as daytime heating assists in convection across the area.
With the loss of daytime heating and in conjunction with general
model consensus, have kept PoPs out overnight Wednesday into early
Thursday. As the low is depicted to begin traversing eastward
Thursday, have only slight chance during the day with the primary
focus for possible convection more toward eastern KY. The models
have the low slowly but surely progressing eastward during this time
frame and am a little skeptical on its speed. How quickly the low
exits will depend on the timing of a weak frontal boundary
attempting to lay out across the southern Great Lakes by Thursday
night.
Thursday night through Friday night:
Have gone with slight chance PoPs strictly across the northern
sections as the alluded to frontal boundary approaches from the
north. The front stalls well to our north and does not currently
appear to be a factor for us beyond Friday. The aforementioned
shortwave swings around the region Friday, hence the slight to
chance PoPs under diurnally-driven conditions. Again, skepticism
sets in for the timing of it all as it seems to really move through
a little too quickly. For now, have kept the area dry Friday night
until a better handle on the progression of everything plays out.
Temperatures will be more difficult to predict Tuesday night through
Friday night as cloudy skies and/or rain will obviously wreck havoc.
What can be said with confidence is that highs will continue to run
slightly below normal and lows will flirt with normal.
Saturday through Sunday:
With that ridge building in, we`ll begin to see real signs of summer
return as temperatures look to rebound back toward normal and partly
to mostly sunny skies prevail.
&&
.AVIATION (12Z TAF Update)...
Issued at 635 AM EDT Mon Aug 19 2013
While VLIFR conditions exist at BWG, vsbys/cigs at SDF/LEX have not
been near as bad as originally thought thanks to a persistent mid
level cloud deck overnight. So for the rest of the day, expect VFR
conditions at all TAF sites after fog burns off at BWG within the
next few hours. Winds will be light out of the ENE throughout the
TAF period. BWG will once again be fog prone tomorrow morning, but
it should not be as dense as this morning`s fog.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
Update.........AMS
Short Term.....AMS
Long Term......lg
Aviation.......AMS
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
535 AM EDT Mon Aug 19 2013
...Forecast Update...
Issued at 530 AM EDT Mon Aug 19 2013
Updated the forecast to remove areas of fog with patchy dense fog
from southeast Indiana and the Bluegrass region of KY. Mid level
clouds and lesser low level moisture than central and southern KY
(where patches of dense fog have been reported) have limited fog
formation over southeast Indiana and the Bluegrass. Downgraded this
area to just patchy fog for the rest of the pre-dawn hours.
Issued an SPS for portions of south and central KY where patchy
dense fog has been reported and where it rained yesterday (which
should be fog prone). Few-sct mid level clouds continue to move
over this area improving fog at times so feel dense fog coverage
will remain patchy.
.SHORT TERM (Now through Tuesday)...
Issued at 330 AM EDT Mon Aug 19 2013
The main forecast concern in the short term will be fog this
morning. A very moist low level atmosphere along with very light or
nearly calm winds have created an ideal environment for fog
formation which we`ve already seen develop in our area. The worst
fog spots remain over southern IL/western KY and over southwest
Ohio. The 5Z RAP model has these fog areas handled well and expect
them to expand into central KY and portions of southeast IN. Low
clouds will also accompany the fog as soundings indicate a shallow
layer of trapped moisture under a weak inversion. With these
thoughts in mind, think that most locations over southern IN and
central KY will see areas of fog this morning. Some locations over
central KY and southeast IN will probably see patches of dense fog
as well assuming the low clouds don`t inhibit fog density too much.
Will highlight the patchy dense fog in the HWO this morning and
monitor closely in case it becomes more widespread and an SPS or
dense fog advisory is need.
For the rest of the day, fog should burn off fairly quickly after
sunrise. With an upper trough passing through the region, can`t
rule out an isld shower over portions of south and east central KY.
However, did scale the area of potential precip back a bit. High
temperatures should reach the low to mid 80s this afternoon.
Tonight a second upper trough will settle into the mid Mississippi
River Valley. Some fog may be possible but not as widespread as
this morning. Will continue inherited patchy fog mainly in river
valleys. Lows tonight will be in the mid 60s.
For Tues, expect a 20% chance of showers/t-storms to expand from
south to north over the area throughout the day as a vort wave on
the eastern side of the upper trough push north through our area.
Any convection would be on the weak side. Tuesday afternoon high
temps should be in the low to mid 80s with southern Indiana being
the hottest due to a longer period of sunshine before clouds/isld
convection move in.
.LONG TERM (Tuesday Night through Sunday)...
Issued at 311 AM EDT Mon Aug 19 2013
The models have finally come into agreement with a mid-level low
that forms over the Ohio Valley at the start of this forecast
period. This cutoff low hangs out in the region through Thursday
night when it undergoes a transformation into an open wave in
response to an approaching shortwave. This shortwave rides around
the periphery of a stout ridge building in over the Plains and looks
to exit the forecast area by early Saturday. The ridge continues to
build in from the west, giving us dry conditions through the end of
the weekend and into early next week.
Tuesday night through Thursday:
For this issuance, have introduced slight chance PoPs for Tuesday
night as the low establishes itself overhead and surface southerly
flow allows for moisture to be pulled in. Chance PoPs continues for
Wednesday as daytime heating assists in convection across the area.
With the loss of daytime heating and in conjunction with general
model consensus, have kept PoPs out overnight Wednesday into early
Thursday. As the low is depicted to begin traversing eastward
Thursday, have only slight chance during the day with the primary
focus for possible convection more toward eastern KY. The models
have the low slowly but surely progressing eastward during this time
frame and am a little skeptical on its speed. How quickly the low
exits will depend on the timing of a weak frontal boundary
attempting to lay out across the southern Great Lakes by Thursday
night.
Thursday night through Friday night:
Have gone with slight chance PoPs strictly across the northern
sections as the alluded to frontal boundary approaches from the
north. The front stalls well to our north and does not currently
appear to be a factor for us beyond Friday. The aforementioned
shortwave swings around the region Friday, hence the slight to
chance PoPs under diurnally-driven conditions. Again, skepticism
sets in for the timing of it all as it seems to really move through
a little too quickly. For now, have kept the area dry Friday night
until a better handle on the progression of everything plays out.
Temperatures will be more difficult to predict Tuesday night through
Friday night as cloudy skies and/or rain will obviously wreck havoc.
What can be said with confidence is that highs will continue to run
slightly below normal and lows will flirt with normal.
Saturday through Sunday:
With that ridge building in, we`ll begin to see real signs of summer
return as temperatures look to rebound back toward normal and partly
to mostly sunny skies prevail.
&&
.AVIATION (06Z TAF Update)...
Issued at 125 AM EDT Mon Aug 19 2013
The TAF challenge this morning will be the extent and intensity of
fog and low cigs over the TAF sites as we sit in a very moist
environment with weak or calm winds. Observations across the region
reveal 2 areas of fog/low cigs...one over Illinois/western KY and
the other over southwest Ohio. The RAP is picking up on these areas
of fog/low cigs well and forecasts that they will expand into
SDF/BWG/LEX as the morning progresses. LEX seems to be the most
likely to see the worst flight conditions with MVFR conditions
likely to develop within the next few hours and decline to LIFR by
around 9 or 10Z. BWG/SDF seem to be more on the edges of the
projected fog/low cigs. Since BWG is very fog prone, did go ahead
and bring flight conditions into the LIFR cat by 9Z with a slightly
slower progression to that restriction than LEX. SDF seems to be
the least likely to see really low vsbys/cigs although based on the
latest RAP guidance, they will probably drop into the IFR cat just
before sunrise. If the fog/low cigs expand more than projected by
the RAP, SDF TAF will need to be amended with more flight
restrictions.
Fog/low cigs should improve by 13 or 14Z with VFR conditions
expected the rest of the day with a light ENE wind.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
Update.........AMS
Short Term.....AMS
Long Term......lg
Aviation.......AMS
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
333 AM EDT Mon Aug 19 2013
.SHORT TERM (Now through Tuesday)...
Issued at 330 AM EDT Mon Aug 19 2013
The main forecast concern in the short term will be fog this
morning. A very moist low level atmosphere along with very light or
nearly calm winds have created an ideal environment for fog
formation which we`ve already seen develop in our area. The worst
fog spots remain over southern IL/western KY and over southwest
Ohio. The 5Z RAP model has these fog areas handled well and expect
them to expand into central KY and portions of southeast IN. Low
clouds will also accompany the fog as soundings indicate a shallow
layer of trapped moisture under a weak inversion. With these
thoughts in mind, think that most locations over southern IN and
central KY will see areas of fog this morning. Some locations over
central KY and southeast IN will probably see patches of dense fog
as well assuming the low clouds don`t inhibit fog density too much.
Will highlight the patchy dense fog in the HWO this morning and
monitor closely in case it becomes more widespread and an SPS or
dense fog advisory is need.
For the rest of the day, fog should burn off fairly quickly after
sunrise. With an upper trough passing through the region, can`t
rule out an isld shower over portions of south and east central KY.
However, did scale the area of potential precip back a bit. High
temperatures should reach the low to mid 80s this afternoon.
Tonight a second upper trough will settle into the mid Mississippi
River Valley. Some fog may be possible but not as widespread as
this morning. Will continue inherited patchy fog mainly in river
valleys. Lows tonight will be in the mid 60s.
For Tues, expect a 20% chance of showers/t-storms to expand from
south to north over the area throughout the day as a vort wave on
the eastern side of the upper trough push north through our area.
Any convection would be on the weak side. Tuesday afternoon high
temps should be in the low to mid 80s with southern Indiana being
the hottest due to a longer period of sunshine before clouds/isld
convection move in.
.LONG TERM (Tuesday Night through Sunday)...
Issued at 311 AM EDT Mon Aug 19 2013
The models have finally come into agreement with a mid-level low
that forms over the Ohio Valley at the start of this forecast
period. This cutoff low hangs out in the region through Thursday
night when it undergoes a transformation into an open wave in
response to an approaching shortwave. This shortwave rides around
the periphery of a stout ridge building in over the Plains and looks
to exit the forecast area by early Saturday. The ridge continues to
build in from the west, giving us dry conditions through the end of
the weekend and into early next week.
Tuesday night through Thursday:
For this issuance, have introduced slight chance PoPs for Tuesday
night as the low establishes itself overhead and surface southerly
flow allows for moisture to be pulled in. Chance PoPs continues for
Wednesday as daytime heating assists in convection across the area.
With the loss of daytime heating and in conjunction with general
model consensus, have kept PoPs out overnight Wednesday into early
Thursday. As the low is depicted to begin traversing eastward
Thursday, have only slight chance during the day with the primary
focus for possible convection more toward eastern KY. The models
have the low slowly but surely progressing eastward during this time
frame and am a little skeptical on its speed. How quickly the low
exits will depend on the timing of a weak frontal boundary
attempting to lay out across the southern Great Lakes by Thursday
night.
Thursday night through Friday night:
Have gone with slight chance PoPs strictly across the northern
sections as the alluded to frontal boundary approaches from the
north. The front stalls well to our north and does not currently
appear to be a factor for us beyond Friday. The aforementioned
shortwave swings around the region Friday, hence the slight to
chance PoPs under diurnally-driven conditions. Again, skepticism
sets in for the timing of it all as it seems to really move through
a little too quickly. For now, have kept the area dry Friday night
until a better handle on the progression of everything plays out.
Temperatures will be more difficult to predict Tuesday night through
Friday night as cloudy skies and/or rain will obviously wreck havoc.
What can be said with confidence is that highs will continue to run
slightly below normal and lows will flirt with normal.
Saturday through Sunday:
With that ridge building in, we`ll begin to see real signs of summer
return as temperatures look to rebound back toward normal and partly
to mostly sunny skies prevail.
&&
.AVIATION (06Z TAF Update)...
Issued at 125 AM EDT Mon Aug 19 2013
The TAF challenge this morning will be the extent and intensity of
fog and low cigs over the TAF sites as we sit in a very moist
environment with weak or calm winds. Observations across the region
reveal 2 areas of fog/low cigs...one over Illinois/western KY and
the other over southwest Ohio. The RAP is picking up on these areas
of fog/low cigs well and forecasts that they will expand into
SDF/BWG/LEX as the morning progresses. LEX seems to be the most
likely to see the worst flight conditions with MVFR conditions
likely to develop within the next few hours and decline to LIFR by
around 9 or 10Z. BWG/SDF seem to be more on the edges of the
projected fog/low cigs. Since BWG is very fog prone, did go ahead
and bring flight conditions into the LIFR cat by 9Z with a slightly
slower progression to that restriction than LEX. SDF seems to be
the least likely to see really low vsbys/cigs although based on the
latest RAP guidance, they will probably drop into the IFR cat just
before sunrise. If the fog/low cigs expand more than projected by
the RAP, SDF TAF will need to be amended with more flight
restrictions.
Fog/low cigs should improve by 13 or 14Z with VFR conditions
expected the rest of the day with a light ENE wind.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
Short Term........AMS
Long Term.........lg
Aviation..........AMS
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
152 AM EDT Mon Aug 19 2013
...Forecast Update...
Issued at 145 AM EDT Mon Aug 19 2013
Updated to remove isld POPs over south and east central KY. Looks
like the stream of moisture/forcing for those light precip chances
has moved mostly to our east.
The main forecast challenge for this morning will be fog and low
clouds. The latest RAP model has the best handle on fog/low cloud
areas developing over southern IL/western KY and southwest OH this
morning. It projects those areas will expand into much of central
KY and southeast IN. Current forecast handles the areal extent of
fog well, but a mention of patchy dense fog may be needed with the
4am forecast package. Low clouds would be the main inhibitor of
dense fog but even so, the model indicates visibilities should drop
below a half mile. For now will hold off on a dense fog mention,
and watch fog/low cloud development over the next few hours.
Issued at 1140 PM EDT Sun Aug 18 2013
One more update to bump up coverage of fog some. Seeing visibilities
drop in a few spots late this evening. The clear spot to our west
has seen PAH drop down to a quarter mile in its latest ob. Will have
to watch for worse visibilities over our area tonight, but for now
the trend looks good. Still cannot rule out a stray shower
developing, as the upper trough axis still has not passed our
region. Have left in a slight chance across the southeast for a few
more hours tonight.
Issued at 625 PM EDT Sun Aug 18 2013
Active convection appears confined to a line running from north of
Hartford to west of Lawrenceburg in KY. Fine tuned the rain chances
to focus on this region next couple of hours. Still expect activity
to quiet down with loss of heating and as the upper low, which has
been near us for days, weakens and accelerates northeast.
Next issue will be the chance for fog. Statistical guidance hints at
visibilities lowering during the night, and this makes sense with
residual moisture. Cloud cover should keep us from going too dense
however. For now have added in patchy fog everywhere after midnight.
.SHORT TERM (Now through Monday Night)...
Issued at 300 PM EDT Sun Aug 18 2013
The cutoff upper low that was centered over the Mississippi and Ohio
River confluence this morning is filling, becoming an open wave, and
meandering eastward, as another shortwave trough begins to dive
southeast into the upper Mississippi Valley. Scattered showers and
isolated storms will be possible through the afternoon and early
evening hours, as heating combines with large-scale ascent. The
mid-level trough axis will swing across the area tonight, combined
with loss of heating, will put an end to convection. So, will have
scattered precipitation tapering off from west to east through the
evening hours, with a dry forecast from about midnight onward.
Will continue with dry conditions through Monday morning. However,
the trough across the upper Mississippi Valley tonight will spread
across the Ohio Valley by Monday afternoon. Appears some low-level
moisture will remain in place and with afternoon heating, could
spark some convection. Soundings indicate there should be slight
capping across much of the CWA, allowing mainly low-topped showers
to develop. By late in the afternoon the cap could weaken just
enough to squeeze out an isolated thunderstorm or two, but that
chance appears minimal. So, will run with isolated showers in the
forecast through the afternoon and early evening hours Monday. This
will generally be along and southeast of a line from Frankfort
southwestward to Bowling Green. Any activity will dissipate with
loss of heating, leaving the overnight hours dry.
Temperatures will drop into the lower 60s tonight, with a few breaks
in the cloud cover. Highs in the low to middle 80s will be common
Monday under partly cloudy skies. Expect lows in the low and middle
60s Monday night under partly cloudy to mostly clear skies. Cannot
rule out some patchy fog tonight and Monday night, but tonight will
depend on how much cloud cover is lost and Monday night will depend
on how much drying occurs through Monday afternoon.
.LONG TERM (Tuesday through Sunday)...
Issued at 300 PM EDT Sun Aug 18 2013
The long term period continues to look rather unsettled for much of
the upcoming work week as the Ohio Valley will remain in a rather
stagnant upper level pattern. However, the overall pattern looks to
improve a bit by the end of the week and into the weekend as the
latest forecast datasets point to upper level ridging building in
from the west which will result in warmer and more seasonal
temperatures for the region.
Until late week, the upper level flow is forecast to remain rather
blocky and complex as the band of westerlies remains holed up along
the US/Canadian border. Overall, there is not much forcing in the
hemispheric flow to kick things into gear and smooth the wave
pattern out. With that said, the model solutions show that a
bagging long wave trough axis will remain over the eastern part of
the US from Tuesday through at least late Thursday. With the trough
axis overhead, diurnally driven convection will be possible across
the region. While the overall coverage for the week looks to be
isolated to scattered, it does appear that the best chances for
rainfall would be Wednesday as the actual trough pulls through the
region. With this forecast we plan on keeping isolated-scattered
PoPs in the forecast each afternoon for Tuesday-Thursday with the
highest chances Wednesday. With regards to convection strength, the
combination of weak flow aloft and rather modest instability
suggests that severe weather is not likely. However, high
atmospheric moisture content combined with the weak steering flow
could lead to heavy rain production with any storm that develops.
Temperatures through the period will remain below normal. Have
sided again with the consensus raw datasets for max/min temperatures
as they have verified well over the last few days. This actually
results in a cooling trend applied for Tuesday/Wednesday due to
expected clouds and precipitation. Tues/Wed highs will average in
the lower 80s across the central/east/southeast with lower-middle
80s across the northwest/west sections. With the upper trough
passing to our east on Thursday, we expect less clouds and
precipitation which should allow temperatures to warm into the
middle 80s. Overnight lows will be rather mild with readings in the
upper 60s to the lower 70s.
By Friday, the model solutions start to show their normal spread.
The GFS solutions suggest a weak cold front will pass through the
region and then stall out to our south. On the other hand, the Euro
solution is not as progressive and allow the upper ridging to build
in which would keep the frontal boundary up to our north. For now
have, opted to keep the forecast on the dry side, but will continue
to monitor later forecasts to see if PoPs will be required. With the
upper ridge building in, Sat/Sun continue to look dry at this point.
Temperatures should continue to moderate through the period with
afternoon highs in the middle to upper 80s with overnight lows in
the upper 60s to the lower 70s.
&&
.AVIATION (06Z TAF Update)...
Issued at 125 AM EDT Mon Aug 19 2013
The TAF challenge this morning will be the extent and intensity of
fog and low cigs over the TAF sites as we sit in a very moist
environment with weak or calm winds. Observations across the region
reveal 2 areas of fog/low cigs...one over Illinois/western KY and
the other over southwest Ohio. The RAP is picking up on these areas
of fog/low cigs well and forecasts that they will expand into
SDF/BWG/LEX as the morning progresses. LEX seems to be the most
likely to see the worst flight conditions with MVFR conditions
likely to develop within the next few hours and decline to LIFR by
around 9 or 10Z. BWG/SDF seem to be more on the edges of the
projected fog/low cigs. Since BWG is very fog prone, did go ahead
and bring flight conditions into the LIFR cat by 9Z with a slightly
slower progression to that restriction than LEX. SDF seems to be
the least likely to see really low vsbys/cigs although based on the
latest RAP guidance, they will probably drop into the IFR cat just
before sunrise. If the fog/low cigs expand more than projected by
the RAP, SDF TAF will need to be amended with more flight
restrictions.
Fog/low cigs should improve by 13 or 14Z with VFR conditions
expected the rest of the day with a light ENE wind.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
Update.........AMS/RJS
Short Term.....MJP
Long Term......MJ
Aviation.......AMS
AREA FORECAST DISCUSSION
NWS JACKSON KY
137 AM EDT MON AUG 19 2013
.UPDATE...
ISSUED AT 137 AM EDT MON AUG 19 2013
FORECAST PRETTY MUCH ON TRACK SO FAR TONIGHT. A LINE OF RAIN SHOWERS
CURRENTLY MOVING UP THE VIRGINIA AND WEST VIRGINIA BORDERS TONIGHT
ARE CONTINUING TO SPREAD EVER SO SLOWLY WESTWARD INTO FAR EASTERN
KENTUCKY. THIS EVOLUTION IS EXPECTED TO CONTINUE OVERNIGHT AND DURING
THE DAY ON MONDAY PER THE LATEST MODEL DATA. THEREFORE...NO MAJOR
UPDATE WAS MADE TO THE FORECAST.
UPDATE ISSUED AT 942 PM EDT SUN AUG 18 2013
THE WIDELY SCATTERED SHOWERS AFFECTING THE AREA DURING THE EVENING
HAVE DECREASED IN COVERAGE AT THIS TIME ON THIS SIDE OF THE KY/VA
BORDER. TO THE EAST OF THE BORDER...A BAND OF SHOWERS CONTINUES TO
ADVANCE NORTHEASTWARD. THESE SHOWERS WILL SKIRT OUR VA BORDER
COUNTIES THROUGH THE NIGHT INTO TOMORROW MORNING AND WILL MAINTAIN
HIGHEST POPS IN THAT AREA...WITH DIMINISHING RAIN CHANCES TO THE
WEST. LATEST HRRR RUN SHOWS SOME SHOWERS DEVELOPING BACK FURTHER TO
THE WEST TOWARDS DAWN AND WITH THE FILLING UPPER LOW NEARBY...WILL
MAINTAIN AT LEAST A 20 POP EVERYWHERE THROUGH THE NIGHT INTO THE DAY
TOMORROW.
OTHERWISE...ADDED PATCHY FOG INTO THE FORECAST AS ANY BREAKS IN THE
CLOUDS WILL ALLOW IT TO FORM RATHER QUICKLY OVERNIGHT BUT NO OTHER
CHANGES WERE NEEDED AT THIS TIME.
&&
.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 220 PM EDT SUN AUG 18 2013
UPPER LOW SPINNING OVER WRN KY WILL CONTINUE TO EASE TO THE EAST AS
HIGH PRESSURE SLOWLY RELEASES IT/S HOLD ON THE REGION AND SLIPS TO
THE MID ATLANTIC COAST. MEANWHILE A SFC LOW COMING ONSHORE NEAR THE
MID GULF COAST CONTINUES TO PUSH MOISTURE AND A BLANKET OF CLOUDS
INTO ERN KY. EXPECT THE RAIN TO CONTINUE OVER ERN KY FOR THE NEXT
24-30 HRS AS THE UPPER LOW EDGES ACROSS THE STATE AND FINALLY MOVES
NE TOWARDS THE NEW ENG COAST. THE GULF COAST LOW WILL SLOWLY TRACK NE
AND LINK UP WITH THE UPPER LEVEL SYSTEM BEFORE SWEEPING INTO THE
POCONOS. HIGH PRESSURE WILL THEN BUILD BACK INTO THE AREA AND GIVE
THE REGION A SMALL WINDOW TO DRY OUT ON MON NIGHT. BUT THE MOISTURE
SPLAYED ACROSS THE AREA TODAY AND TONIGHT WILL SET THE STAGE FOR FOG
MON NIGHT AS A FEW BREAKS IN THE CLOUD COVER WILL ALLOW TEMPS TO
DROP FROM A MON HIGH AROUND 80 TO LOWS AT OR NEAR THE DEWPOINT TEMPS
IN THE LOWER 60S FOR MON NIGHT.
.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 231 PM EDT SUN AUG 18 2013
MODELS HAVE CHANGED COURSE A BIT GOING INTO TUESDAY AND WEDNESDAY AS
ANOTHER MID/UPPER LEVEL LOW WILL DEVELOP OVERHEAD. ON
TUESDAY...MOISTURE WILL BE ON THE INCREASE FROM THE SOUTH. MUCH LIKE
ON SATURDAY...DOWNSLOPING SOUTHEAST WINDS WILL HAMPER THE NORTHWARD
PROGRESS OF ANY PRECIPITATION AND KEEP INSTABILITY AT BAY.
THUS...GOING TO CONFINE POPS TO MAINLY THE SOUTHERN 2 ROWS OF
COUNTIES IN KENTUCKY WITH ONLY A SLIGHT CHANCE. AREAS FURTHER NORTH
WILL LIKELY BE AFFECTED BY THE DOWNSLOPING CONDITIONS. BY TUESDAY
NIGHT...AS THE UPPER LEVEL LOW PUSHES SLIGHTLY EAST...WINDS WILL
VEER AROUND TO THE SOUTH OR SOUTHWEST ALLOWING MOISTURE TO SURGE
NORTHWARD. CLOUDS AND SHOWERS WILL OVERSPREAD THE AREA FROM LATE
TUESDAY NIGHT INTO WEDNESDAY. A MID LEVEL VORTICITY MAXIMUM WILL
PUSH EAST DURING THE DAY TO AID IN MORE VIGOROUS SHOWER ACTIVITY.
STILL SOME QUESTION AS TO INSTABILITY DURING THE DAY...AND MUCH LIKE
TODAY...CLOUD COVER COULD LIMIT INSTABILITY KEEPING ANY THUNDER AT
BAY. GOING TO CARRY A SLIGHT CHANCE FOR NOW...BUT FEEL THIS THUNDER
PROBABLY WILL NOT PAN OUT. THIS SYSTEM WILL FINALLY BE ON THE WAY
OUT BY THURSDAY WITH THE EXPECTED RIDGING FINALLY BUILDING ACROSS
THE REGION. THIS WILL SET UP THE SUMMER-LIKE PATTERN BY THURSDAY AND
THROUGH NEXT WEEKEND. THIS WILL YIELD A MINIMAL CHANCE FOR SHOWERS
OR STORMS EACH AFTERNOON...BUT ANTICIPATING THAT MOST AREAS WILL
REMAIN DRY FROM WEDNESDAY NIGHT ONWARD. TEMPERATURES WILL REMAIN A
TOUCH BELOW NORMAL INTO WEDNESDAY WITH THE CLOUD COVER AND
PRECIPITATION...BUT WILL WARM TO NEAR NORMAL FOR THE SECOND HALF OF
THE WEEK...AND AT THIS POINT...LOOKING FOR SLIGHTLY ABOVE NORMAL
READINGS BY NEXT WEEKEND.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 137 AM EDT MON AUG 19 2013
STILL BELOW AVERAGE CONFIDENCE IN FORECAST DETAILS FOR AREA AIRPORTS
TONIGHT AS CLOUDS ARE EXPECTED TO BREAK UP ENOUGH TO ALLOW FURTHER
LOW CLOUD AND FOG DEVELOPMENT OVERNIGHT WITH AMPLE LOW LEVEL MOISTURE
IN PLACE. HAVE FORECAST DETERIORATING CONDITIONS AT ALL 3 TAF SITES
WITH A PERIOD OF LIFR CIGS AND VSBYS AROUND DAWN. SHOULD MID LEVEL
CLOUDS HOLD ON THROUGH THE NIGHT...THIS WILL BE TOO PESSIMISTIC.
OTHERWISE...A FEW STRAY SHOWERS WILL BE POSSIBLE OVERNIGHT AND AGAIN
TOMORROW. WILL HANDLE THIS WITH A VCSH MENTION AT THIS TIME.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...AR
SHORT TERM...DUSTY
LONG TERM...KAS
AVIATION...AR
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
128 AM EDT Mon Aug 19 2013
...Updated Aviation Discussion...
...Forecast Update...
Issued at 1140 PM EDT Sun Aug 18 2013
One more update to bump up coverage of fog some. Seeing visibilities
drop in a few spots late this evening. The clear spot to our west
has seen PAH drop down to a quarter mile in its latest ob. Will have
to watch for worse visibilities over our area tonight, but for now
the trend looks good. Still cannot rule out a stray shower
developing, as the upper trough axis still has not passed our
region. Have left in a slight chance across the southeast for a few
more hours tonight.
Issued at 625 PM EDT Sun Aug 18 2013
Active convection appears confined to a line running from north of
Hartford to west of Lawrenceburg in KY. Fine tuned the rain chances
to focus on this region next couple of hours. Still expect activity
to quiet down with loss of heating and as the upper low, which has
been near us for days, weakens and accelerates northeast.
Next issue will be the chance for fog. Statistical guidance hints at
visibilities lowering during the night, and this makes sense with
residual moisture. Cloud cover should keep us from going too dense
however. For now have added in patchy fog everywhere after midnight.
.SHORT TERM (Now through Monday Night)...
Issued at 300 PM EDT Sun Aug 18 2013
The cutoff upper low that was centered over the Mississippi and Ohio
River confluence this morning is filling, becoming an open wave, and
meandering eastward, as another shortwave trough begins to dive
southeast into the upper Mississippi Valley. Scattered showers and
isolated storms will be possible through the afternoon and early
evening hours, as heating combines with large-scale ascent. The
mid-level trough axis will swing across the area tonight, combined
with loss of heating, will put an end to convection. So, will have
scattered precipitation tapering off from west to east through the
evening hours, with a dry forecast from about midnight onward.
Will continue with dry conditions through Monday morning. However,
the trough across the upper Mississippi Valley tonight will spread
across the Ohio Valley by Monday afternoon. Appears some low-level
moisture will remain in place and with afternoon heating, could
spark some convection. Soundings indicate there should be slight
capping across much of the CWA, allowing mainly low-topped showers
to develop. By late in the afternoon the cap could weaken just
enough to squeeze out an isolated thunderstorm or two, but that
chance appears minimal. So, will run with isolated showers in the
forecast through the afternoon and early evening hours Monday. This
will generally be along and southeast of a line from Frankfort
southwestward to Bowling Green. Any activity will dissipate with
loss of heating, leaving the overnight hours dry.
Temperatures will drop into the lower 60s tonight, with a few breaks
in the cloud cover. Highs in the low to middle 80s will be common
Monday under partly cloudy skies. Expect lows in the low and middle
60s Monday night under partly cloudy to mostly clear skies. Cannot
rule out some patchy fog tonight and Monday night, but tonight will
depend on how much cloud cover is lost and Monday night will depend
on how much drying occurs through Monday afternoon.
.LONG TERM (Tuesday through Sunday)...
Issued at 300 PM EDT Sun Aug 18 2013
The long term period continues to look rather unsettled for much of
the upcoming work week as the Ohio Valley will remain in a rather
stagnant upper level pattern. However, the overall pattern looks to
improve a bit by the end of the week and into the weekend as the
latest forecast datasets point to upper level ridging building in
from the west which will result in warmer and more seasonal
temperatures for the region.
Until late week, the upper level flow is forecast to remain rather
blocky and complex as the band of westerlies remains holed up along
the US/Canadian border. Overall, there is not much forcing in the
hemispheric flow to kick things into gear and smooth the wave
pattern out. With that said, the model solutions show that a
bagging long wave trough axis will remain over the eastern part of
the US from Tuesday through at least late Thursday. With the trough
axis overhead, diurnally driven convection will be possible across
the region. While the overall coverage for the week looks to be
isolated to scattered, it does appear that the best chances for
rainfall would be Wednesday as the actual trough pulls through the
region. With this forecast we plan on keeping isolated-scattered
PoPs in the forecast each afternoon for Tuesday-Thursday with the
highest chances Wednesday. With regards to convection strength, the
combination of weak flow aloft and rather modest instability
suggests that severe weather is not likely. However, high
atmospheric moisture content combined with the weak steering flow
could lead to heavy rain production with any storm that develops.
Temperatures through the period will remain below normal. Have
sided again with the consensus raw datasets for max/min temperatures
as they have verified well over the last few days. This actually
results in a cooling trend applied for Tuesday/Wednesday due to
expected clouds and precipitation. Tues/Wed highs will average in
the lower 80s across the central/east/southeast with lower-middle
80s across the northwest/west sections. With the upper trough
passing to our east on Thursday, we expect less clouds and
precipitation which should allow temperatures to warm into the
middle 80s. Overnight lows will be rather mild with readings in the
upper 60s to the lower 70s.
By Friday, the model solutions start to show their normal spread.
The GFS solutions suggest a weak cold front will pass through the
region and then stall out to our south. On the other hand, the Euro
solution is not as progressive and allow the upper ridging to build
in which would keep the frontal boundary up to our north. For now
have, opted to keep the forecast on the dry side, but will continue
to monitor later forecasts to see if PoPs will be required. With the
upper ridge building in, Sat/Sun continue to look dry at this point.
Temperatures should continue to moderate through the period with
afternoon highs in the middle to upper 80s with overnight lows in
the upper 60s to the lower 70s.
&&
.AVIATION (06Z TAF Update)...
Issued at 125 AM EDT Mon Aug 19 2013
The TAF challenge this morning will be the extent and intensity of
fog and low cigs over the TAF sites as we sit in a very moist
environment with weak or calm winds. Observations across the region
reveal 2 areas of fog/low cigs...one over Illinois/western KY and
the other over southwest Ohio. The RAP is picking up on these areas
of fog/low cigs well and forecasts that they will expand into
SDF/BWG/LEX as the morning progresses. LEX seems to be the most
likely to see the worst flight conditions with MVFR conditions
likely to develop within the next few hours and decline to LIFR by
around 9 or 10Z. BWG/SDF seem to be more on the edges of the
projected fog/low cigs. Since BWG is very fog prone, did go ahead
and bring flight conditions into the LIFR cat by 9Z with a slightly
slower progression to that restriction than LEX. SDF seems to be
the least likely to see really low vsbys/cigs although based on the
latest RAP guidance, they will probably drop into the IFR cat just
before sunrise. If the fog/low cigs expand more than projected by
the RAP, SDF TAF will need to be amended with more flight
restrictions.
Fog/low cigs should improve by 13 or 14Z with VFR conditions
expected the rest of the day with a light ENE wind.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
Update.........RJS
Short Term.....MJP
Long Term......MJ
Aviation.......AMS
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
341 AM EDT MON AUG 19 2013
.SYNOPSIS...
AN UPPER-LEVEL DISTURBANCE WILL PASS THROUGH THE REGION TODAY AND
HIGH PRESSURE WILL BUILD OVERHEAD TONIGHT THROUGH TUESDAY. A TROUGH
WILL IMPACT THE REGION DURING THE MIDDLE PORTION OF THE WEEK BEFORE
A COLD FRONT MOVES THROUGH FRIDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
HAVE HAD SOME POCKETS OF CLEARING EARLY THIS MORNING WITH WEAK
SURFACE HIGH PRESSURE NEARBY. WITH LINGERING LOW LEVEL
MOISTURE...THIS HAS RESULTED IN PATCHY FOG MAINLY ACROSS THE
SHENANDOAH VALLEY/NORTHERN VIRGINIA PIEDMONT AREA. THIS WILL
PERSIST UNTIL SUNRISE.
ALSO HAVE SOME SHOWERS ACROSS SOUTHWEST VIRGINIA THAT EXIST AHEAD
OF AN UPPER TROUGH OVER THE OHIO VALLEY. HRRR HAS SHOWERS MAKING
THEIR WAY INTO THE SOUTHWEST CWA OVER THE NEXT SEVERAL HOURS. AS
THE TROUGH ADVANCES EASTWARD THROUGH THE DAY...ANTICIPATE NEW
SHOWER DEVELOPMENT IN THE PVA ZONE LATER THIS MORNING WEST OF THE
BLUE RIDGE AND THEN SPREADING EAST TOWARD THE METRO CORRIDOR IN
THE AFTERNOON.
DUE TO CLOUD COVER...INSTABILITY IS FORECAST TO BE WEAK AND LIKELY
LESS THAN 500 J/KG. THEREFORE HAVE ONLY ALLOWED FOR ISOLATED
THUNDER DURING THE AFTERNOON AND NO SEVERE IS EXPECTED.
SHOWERS WILL BE QUICK TO DISSIPATE THIS EVENING WITH THE SETTING
OF THE SUN AND WITH THE SHORTWAVE EXITING THE AREA. HIGH PRESSURE
BUILDS IN OVERNIGHT...AND FOG COULD BE MORE WIDESPREAD ESPECIALLY
IF CLEARING OCCURS.
&&
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
SURFACE HIGH PRESSURE WILL REMAIN OVER THE REGION TUESDAY INTO
TUESDAY NIGHT...BRINGING DRY AND SEASONABLE CONDITIONS. MAX TEMPS
TUESDAY WILL RANGE FROM THE UPPER 70S IN THE MOUNTAINS TO THE
MIDDLE AND UPPER 80S ACROSS MOST OTHER LOCATIONS. MIN TEMPS
TUESDAY NIGHT WILL RANGE FROM THE 50S IN PORTIONS OF THE POTOMAC
HIGHLANDS TO THE LOWER AND MIDDLE 70S IN DOWNTOWN WASHINGTON AND
BALTIMORE.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
HIGH PRESSURE WILL MOVE OFF THE COAST WEDNESDAY AND A RETURN FLOW
WILL USHER IN WARM AND HUMID CONDITIONS. AN UPPER-LEVEL LOW WILL
ALSO BUILD TOWARD THE REGION FROM THE OHIO VALLEY. A FEW SHOWERS AND
THUNDERSTORMS ARE POSSIBLE...ESPECIALLY ACROSS THE SHENANDOAH VALLEY
AND POTOMAC HIGHLANDS...CLOSER TO THE UPPER-LEVEL LOW.
THE UPPER-LEVEL LOW WILL WEAKEN AND ROTATE THROUGH AS AN UPPER-LEVEL
TROUGH WEDNESDAY NIGHT AND THURSDAY. A SURFACE TROUGH WILL ALSO
REMAIN OVER THE REGION DURING THIS TIME. A FEW SHOWERS AND
THUNDERSTORMS ARE POSSIBLE...BUT MUCH OF THE TIME MAY TURN OUT DRY.
TEMPERATURES WILL BE NEAR CLIMO.
A COLD FRONT WILL PASS THROUGH THE REGION FRIDAY...BRINGING THE
CHANCE FOR MORE SHOWERS AND THUNDERSTORMS. HIGH PRESSURE MAY BUILD
IN BEHIND THIS SYSTEM DURING THE WEEKEND.
&&
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
GREATEST POTENTIAL FOR FOG THIS MORNING WILL BE CHO...WITH A PERIOD
OF IFR IN THE TAF. CONFIDENCE IN LOW VIS DECREASES FURTHER NORTHEAST
WHERE DEWPOINTS ARE LOWER BUT BRIEF MVFR AT MRB/IAD IS POSSIBLE.
SHORTWAVE TROUGH WILL BRING SCATTERED SHOWERS...PROBABLY NOT UNTIL
THE AFTERNOON AT THE HUBS. AS HIGH PRESSURE BUILDS IN TONIGHT...VIS
RESTRICTIONS COULD BE MORE WIDESPREAD AND/OR LOWER LATE TONIGHT.
AREAS OF BR/FOG WILL LIKELY IMPACT THE TERMINALS EARLY TUESDAY
MORNING. VFR CONDITIONS ARE EXPECTED FOR THE REST OF TUESDAY INTO
TUESDAY NIGHT. PATCHY BR/FOG MAY IMPACT THE TERMINALS LATE TUESDAY
NIGHT.
A FEW SHOWERS AND THUNDERSTORMS ARE POSSIBLE WEDNESDAY AND
THURSDAY...BUT MUCH OF THE TIME MAY TURN OUT DRY. A COLD FRONT MAY
PASS THROUGH THE TERMINALS FRIDAY.
&&
.MARINE...
WEAK GRADIENT WILL GENERALLY KEEP WINDS AOA 10 KT THROUGH TONIGHT.
WEAK TROUGH MAY BRING A FEW SHOWERS THIS AFTERNOON...THEN HIGH
PRESSURE BUILDS IN OVERNIGHT.
HIGH PRESSURE WILL REMAIN OVER THE WATERS TUESDAY BEFORE MOVING OFF
THE COAST WEDNESDAY. A RETURN FLOW WILL DEVELOP WEDNESDAY THROUGH
THURSDAY. WIND SPEEDS SHOULD REMAIN BELOW SCA CRITERIA DURING THIS
TIME. A COLD FRONT WILL PASS THROUGH THE WATERS LATE FRIDAY.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...BJL
NEAR TERM...BPP
SHORT TERM...BJL
LONG TERM...BJL
AVIATION...BJL/BPP
MARINE...BJL/BPP
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
738 PM EDT TUE AUG 20 2013
.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 416 PM EDT TUE AUG 20 2013
WV IMAGERY AND RUC ANALYSIS INDICATED A MAINLY ZONAL MID/UPPER LEVEL
FLOW ACROSS SRN CANADA AND THE NRN CONUS ATOP RIDING OVER THE PLAINS
AND A CUTOFF LOW NEAR KSTL. THE MAIN UPSTREAM SHORTWAVE TROUGH WAS
LOCATED WELL UPSTREAM...FROM SASK INTO ERN ALBERTA. AT THE SFC...SW
FLOW PREVAILED THROUGH THE WRN GREAT LAKES BTWN HIGH PRES OVER THE
ERN OH VALLEY AND A TROUGH FROM NW ONTARIO INTO CNTRL ND. A COLD
FRONT EXTENDED FROM NEAR WINNIPEG INTO SRN SASK. ALTHOUGH VIS LOOP
SHOWED ABUNDANT CU ACROSS THE REGION AND A LAKE BREEZE BOUNDARY OFF
OF LAKE MI...CAPPING EVIDENT ON AREA SOUNDINGS WITH 800-700 MB TEMPS
AROUND 13C HAS SUPPRESSED ANY CONVECTION THAT WOULD PRODUCE ANY
SHRA/TSRA.
TONIGHT...AS THE ALBERTA/SASK MOVES INTO MANITOBA AND THE PLAINS
TROUGH SLIDES TO THE EAST THE STRONGEST LOW LEVEL MOISTURE
ADVECTION...FOCUS OF THE LOW LEVEL JET...AND 310K ISENTROPIC LIFT
THROUGH THE 850-700 MB FRONT WILL REMAIN JUST NORTH OF LAKE SUPERIOR
BUT MAY BRUSH THE NRN PORTION OF THE LAKE. OTHERWISE...THE PERSISTENT
SW FLOW THROUGH THE WRN LAKES WILL KEEP TEMPS WELL ABOVE
NORMAL...ESPECIALLY FOR DOWNSLOPE LOCATIONS NEAR LAKE SUPERIOR. MIN
READINGS IN THE MID 60S TO LOWER 70S...NEAR THE HIGHER END OF
GUIDANCE ARE EXPECTED.
WED...AS THE SHRTWV MOVES THROUGH NRN ONTARIO IT WILL DRAG THE COLD
FRONT THROUGH LAKE SUPERIOR AND UPPER MI. THE COMBINATION OF LOW
LEVEL CONV ALONG THE FRONT...REINFORCED BY THE LAKE SUPERIOR
BREEZE...AND WEAK TO MODERATE MID LEVEL QVECTOR CONV WITH THE TAIL
OF THE SHRTWV SHOULD TRIGGER TSRA OVER WEST UPPER MI IN THE EARLY
AFTERNOON WHICH WILL SPREAD INTO THE CNTRL CWA BY MID AND LATE
AFTERNOON. DEWPOINTS INTO THE UPPER 60S AND TEMPS IN THE UPPER 80S
WILL RESULT IN MLCAPE VALUES INTO THE 2K-3K J/KG RANGE. THE STRONG
INSTABILITY(BY U.P. STANDARDS) ALONG WITH 0-6KM SHEAR TO AROUND 30
KT WILL BE ENOUGH TO SUPPORT MULTICELL CLUSTERS WITH SOME SEVERE
THUNDERSTORMS. WITH DCAPE VALUES OF 1K J/KG...DAMAGING WINDS WILL BE
THE MAIN THREAT. SOME ISOLATED LARGE HAIL MAY ALSO BE POSSIBLE WITH
THE STRONGEST STORMS.
.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 416 PM EDT TUE AUG 20 2013
COLD FRONT AND ASSOCIATED SHOWERS/THUNDERSTORMS WILL BE MOVING
SOUTHEAST ACROSS CENTRAL AND EASTERN UPPER MICHIGAN AT THE
START OF THE LONG TERM PERIOD. EXPECT THESE STRONG TO POTENTIALLY
SEVERE THUNDERSTORMS TO BE SLIDING EAST-SOUTHEAST ACROSS THOSE AREAS
DURING THE EVENING HOURS AND BE MOVING INTO LAKE MICHIGAN TOWARDS
MIDNIGHT OR THE EARLY OVERNIGHT HOURS. 12Z MODELS TODAY SEEM TO BE
A LITTLE SLOWER WITH THE FRONTAL PASSAGE THAN YESTERDAY...SO WILL
FOLLOW THE IDEA OF THE MID SHIFT WITH THE TIMING.
A SHORTWAVE DIVING SOUTHEAST FROM LAKE WINNIPEG WEDNESDAY NIGHT
WILL CROSS THE U.P. ON THURSDAY MORNING. WITH THE DRY AIR AND
HIGH PRESSURE THAT ARRIVES BEHIND THE COLD FRONT...SHOULDN/T SEE
MUCH INFLUENCE FROM THE SHORTWAVE ON THE WEATHER AND EXPECT MOSTLY
SUNNY SKIES. HIGHS THURSDAY WILL BE MUCH COOLER (BY 10-15
DEGREES) THAN WEDNESDAY WITH THE NORTHERLY WINDS OFF LAKE SUPERIOR.
FORTUNATELY...MOST AREAS WILL SEE RAIN TOMORROW...OTHERWISE THERE
COULD BE AN ELEVATED FIRE WX RISK WITH NORTH WINDS OF 10-20MPH AND
RH VALUES FALLING TOWARDS 30 PERCENT.
ANOTHER SHORTWAVE ROUNDING THE UPPER RIDGE IN CENTRAL CANADA WILL
DIVE SOUTHEAST ACROSS THE EASTERN CWA ON FRIDAY. AT THIS
TIME...WOULD EXPECT SOME INCREASE IN CLOUD COVER BASED OFF
925-850MB MOISTURE AND DIURNAL HEATING OVER THE EASTERN PART OF THE
CWA (MAINLY FROM MARQUETTE/DICKINSON COUNTIES AND EAST). WON/T GO
TOO HIGH ON CLOUD COVER...BUT AT LEAST GIVE A PERIOD OF PARTLY
CLOUDY SKIES OVER THE EAST AS THAT MOISTURE MOVES THROUGH.
UPPER RIDGE THAT WAS OVER THE NORTHERN PLAINS AND CENTRAL CANADA
WILL THEN SHIFT EAST ON FRIDAY NIGHT WITH THE AXIS OF THE RIDGE
OVER UPPER MICHIGAN BY 12Z SATURDAY. THIS MOVEMENT OF THE RIDGE
WILL ALSO SLIDE THE SURFACE HIGH EAST OF THE AREA AND ALLOW
SOUTHERLY FLOW AND GRADUALLY WARMING TEMPERATURES TO RETURN. MODELS
ARE STILL STRUGGLING TO COME UP WITH A CONSENSUS ON THE SERIES OF
SHORTWAVES MOVING INTO THE UPPER RIDGE AND GRADUALLY BREAKING IT
DOWN FROM SATURDAY AFTERNOON THROUGH THE FIRST HALF OF NEXT WEEK.
THE FIRST WAVE WILL MOVE THROUGH THE AREA SATURDAY AFTERNOON AND
NIGHT (OVER THE NORTH HALF OF THE CWA) AND THE NEXT ONE LATE SUNDAY
AFTERNOON INTO MONDAY MORNING. THE DISCREPANCIES GROW FURTHER ON
MONDAY NIGHT INTO TUESDAY...WITH GFS BRINGING ANOTHER SHORTWAVE
THROUGH ON TUESDAY WHILE THE ECMWF/GEM HAS HIGH PRESSURE OVER THE
AREA. THESE PERIODS OF SHOWERS/THUNDERSTORMS ALSO LEADS TO
UNCERTAINTY WITH HIGHS BUT SHOULD AT LEAST BE ABOVE NORMAL.
&&
.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 717 PM EDT TUE AUG 20 2013
EXPECT VFR CONDITIONS AT ALL 3 TAF SITES DESPITE THE CHANCE FOR
SHRA/TSRA WED AFTERNOON WITH THE PASSAGE OF A COLD FRONT. WITH SUNSET
THIS EVENING AN INVERSION WL FORM AND RESULT IN LLWS WITH
STRENGTHENING NOCTURNAL SW LOW LEVEL JET UNDER A SHARPENING PRES
GRADIENT AHEAD OF APPROACHING COLD FRONT. EXPECT SHRA AND POSSIBLE
TSRA EARLY WED AFTERNOON AT KIWD AND KCMX AND LATE WED AFTERNOON AT
KSAW WITH THE FRONTAL PASSAGE.
&&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 416 PM EDT TUE AUG 20 2013
OVERALL...EXPECT WINDS LESS THAN 20KT THRU THE PERIOD AS A
RELATIVELY WEAK PRES GRADIENT TYPICAL OF SUMMER PERSISTS OVER THE
GREAT LAKES REGION. ONE PERIOD OF STRONGER WINDS (GUSTS TO 20-25KT)
MAY OCCUR TONIGHT AS THE PRES GRADIENT TIGHTENS AHEAD OF THE
APPROACHING COLD FRONT...BUT HIGH OVERWATER STABILITY WITH INFLUX
OF A VERY WARM AIRMASS WILL LIMIT THE INCREASE OF WIND SPEED NEAR THE
COOLER LAKE SURFACE. THE ARRIVAL OF MORE HUMID AIR MAY RESULT IN
SOME FOG FORMATION OVER THE COOLER LAKE WATERS...BUT RESTRICTED THE
FOG FORECAST TO AREAS WHERE SOME SHOWERS OR THUNDERSTORMS ARE
EXPECTED. ANY FOG WILL DISSIPATE WED AFTN AND EVENING FOLLOWING A
COLD FRONTAL PASSAGE AND THE ARRIVAL OF DRIER AIR.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...JLB
LONG TERM...SRF
AVIATION...VOSS
MARINE...JLB
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
422 PM EDT MON AUG 19 2013
.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 422 PM EDT MON AUG 19 2013
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW ZONAL FLOW ACROSS MUCH OF
SRN CANADA. SHORTWAVE TROF THAT WAS OVER MT/SRN SASKATCHEWAN 24HRS
AGO IS NOW OVER THE UPPER LAKES THOUGH MUCH OF THE ENERGY APPEARS TO
BE SETTLING SSE INTO THE WEAKENING REMNANT OF THE TROF THAT HAS BEEN
OVER THE LOWER MISSISSIPPI VALLEY THE LAST FEW DAYS. WAVE PRODUCED A
CLUSTER OF SHRA/TSRA OVER WRN LAKE SUPERIOR THIS MORNING. THE SHRA
RAPIDLY DIMINISHED AS THEY APPROACHED WRN UPPER MI AND DISSIPATED
SOON AFTER REACHING THAT AREA. SO...FAR NO NEW SHRA/TSRA HAVE
DEVELOPED WITH DAYTIME HEATING.
LATEST SPC MESOANALYSIS SHOWS MLCAPE OF 500-1000J/KG OVER ROUGHLY
THE W HALF OF UPPER MI. VIS SATELLITE IMAGERY SHOWS CU DEVELOPING
OVER THE LAST COUPLE OF HRS...AND LATEST OBS ALONG THE SHORE
INDICATE LAKE BREEZE JUST BEGINNING TO DEVELOP OFF LAKE SUPERIOR.
PERHAPS A FEW SHRA/TSRA MAY YET DEVELOP OVER THE NEXT COUPLE OF HRS
AS LAKE BREEZE MAKES SOME INLAND PROGRESS. SINCE LATEST HIGH RES
RAPID REFRESH MODEL STILL GENERATES SOME CONVECTION OVER THE NCNTRL
LATE THIS AFTN...WILL HOLD ONTO SCHC POPS FOR THE NEXT SEVERAL HRS.
IF ANY SHRA/TSRA DO DEVELOP...THEY WILL DISSIPATE WITH LOSS OF
DAYTIME HEATING...ESPECIALLY SINCE HEIGHTS ARE IN THE PROCESS OF
STEADILY RISING AND DEEP LAYER QVECTOR DIVERGENCE IS DEVELOPING.
THERE IS SOME THETA-E ADVECTION OVERNIGHT...AND THE GEM SUGGESTS
SOME ISOLD CONVECTION LATE TONIGHT/TUE MORNING AT LEADING EDGE OF
THETA-E AXIS APPROACHING WRN UPPER MI. HOWEVER...WITH 850MB WINDS
ANTICYCLONIC AND NOT MUCH OF A LOW-LEVEL JET...POTENTIAL OF ANY
ISOLD CONVECTION LATE SEEMS VERY UNLIKELY. WILL CARRY DRY FCST THRU
THE OVERNIGHT. ALTHOUGH SKIES WILL TURN MOSTLY CLEAR...A LIGHT BUT
STEADY SW WIND AND INCREASED COLUMN MOISTURE WILL WORK TO LIMIT THE
DIURNAL TEMP FALL. UNDER S TO SW WINDS...THE HIGHEST MIN TEMPS WILL
BE IN THE DOWNSLOPE AREAS NEAR LAKE SUPERIOR OVER THE W HALF. EXPECT
MINS IN THE MID 60S THERE. INLAND...MID 50S TO AROUND 60F SHOULD BE
THE RULE.
ON TUE...PRES GRADIENT TIGHTENS A BIT BTWN SFC HIGH OVER THE MID
ATLANTIC STATES AND A LOW PRES TROF MOVING ACROSS THE NRN
PLAINS/SCNTRL CANADA. STRENGTHENING SW FLOW WILL BRING AN INCREASE
IN LOW-LEVEL DWPTS TUE...RESULTING IN A MUCH MORE UNCOMFORTABLE DAY.
MIXING TOWARD 800MB ON FCST SOUNDINGS SUGGESTS MAX TEMPS EASILY INTO
THE MID/UPPER 80S. STRONGER SW WINDS WILL PREVENT LAKE BREEZE
DEVELOPMENT OFF LAKE SUPERIOR AND SHOULD LEAD TO SOME OF THE
WARMEST READINGS IN THE DOWNSLOPE AREAS NEAR THE LAKE. EXPECT SOME
LOCATIONS TO REACH OR JUST EXCEED 90F. S/SW WINDS WILL KEEP
CONDITIONS COOLER NEAR LAKE MICHIGAN. COMBINATION OF TEMPS WELL INTO
THE 80S AND HIGHER DWPTS INTO THE 60S WILL MAKE TUE THE MOST
UNCOMFORTABLE DAY SINCE THE HOT WEATHER STRETCH IN MID JULY. NAM
SHOWS MLCAPE INCREASING TO 2000-3000J/KG TUE AFTN WHILE THE GFS IS
LOWER IN THE 1000-2000J/KG RANGE. LACK OF LAKE BREEEZE DEVELOPMENT
OFF LAKE SUPERIOR WILL BE ONE MISSING FORCING MECHANISM TO TRIGGER
CONVECTION. SINCE THERE ARE HINTS OF A SUBTLE SHORTWAVE MOVING
TOWARD THE UPPER LAKES...OPTED TO MAINTAIN SCHC POPS OVER PORTIONS
OF CNTRL UPPER MI WHERE THERE IS SOME LOW-LEVEL CONVERGENCE AS A
RESULT OF LAKE MICHIGAN LAKE BREEZE COMPONENT. IN THE ABSENCE OF ANY
SHORTWAVE...TUE WILL LIKELY END UP DRY ACROSS THE BOARD.
.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 422 PM EDT MON AUG 19 2013
NORTHERN STREAM UPPER TROUGH WILL SLIDE THROUGH THE AREA DURING
THE FIRST PART OF THE LONG TERM PERIOD AND LEAD TO A DECENT CHANCE
OF RAIN OVER THE AREA WEDNESDAY.
FIRST FOR TUESDAY NIGHT...THERE MAY BE SOME SHOWERS/THUNDERSTORMS
OVER LAKE SUPERIOR ON AHEAD OF THE COLD FRONT. THIS A CONTINUATION
OF THE CONVECTION THAT DEVELOPS IN SOUTHWEST ONTARIO AND NORTHEAST
MINNESOTA FROM THE AFTERNOON AND A WEAK SHORTWAVE MOVING EAST
ACROSS LAKE SUPERIOR. IN ADDITION...THIS IS ALSO THE AREA OF THE
STRENGTHENING LOW LEVEL JET AND 850-700MB THERMAL RIDGE. WITH STORM
MOTIONS TO THE EAST...WOULD THINK ISLE ROYALE AND NORTHERN LAKE
SUPERIOR WOULD HAVE THE BEST SHOT OF SEEING PRECIPITATION...BUT IT
COULD BRUSH THE KEWEENAW PENINSULA.
ON WEDNESDAY...THE MAIN SHORTWAVE WILL BE MOVING THROUGH SOUTHWEST
ONTARIO AND BE DISCONNECTED FROM THE COLD FRONT MOVING EAST ACROSS
WESTERN LAKE SUPERIOR ON WEDNESDAY MORNING. BUT...THERE ARE HINTS
THAT A SECOND WEAKER WAVE WILL BE SLIDING EAST ACROSS NORTHERN
WISCONSIN AND WESTERN UPPER MICHIGAN IN THE AFTERNOON. IF THIS
OCCURS...IT WOULD ASSIST WITH CONVECTIVE DEVELOPMENT AS THE COLD
FRONT MOVES THROUGH WESTERN/CENTRAL U.P. DURING THE DAY WEDNESDAY.
MODELS SEEM TO HAVE SPED IT UP A TOUCH WITH IT MOVING THROUGH THE
WESTERN U.P. IN THE LATE MORNING OR EARLY AFTERNOON AND THEN THE
CENTRAL U.P. IN THE MID AFTERNOON HOURS. IT THEN EXITS THE AREA
OVER LAKE MICHIGAN DURING THE EVENING. WITH THE WARM...HUMID
AIRMASS...INSTABILITY WILL BE PRETTY GOOD FOR U.P. STANDARDS (MLCAPE
VALUES OF 1500-3000 J/KG DEPENDING ON THE MODEL) WHICH ARE AIDED BY
STEEP MID LEVEL LAPSE RATES (AROUND 7-7.5C/KM FROM 850-700MB). THIS
HELPS BOOST HAIL CAPE VALUES TOWARDS 800 J/KG...BUT WITH FREEZING
LEVELS AROUND 12KFT...IT MAY COUNTERACT THE HAIL POTENTIAL. 0-6KM
AND EFFECTIVE SHEAR VALUES ARE MARGINAL FOR THUNDERSTORM
ORGANIZATION (ONLY AROUND 20-25KTS) AND FAIRLY UNIDIRECTIONAL. 09Z
SREF RUN AGREES WITH THAT BASIC IDEA AND ONLY HAS 50 PERCENT PROBS
FOR EFFECTIVE SHEAR OVER 30KTS. BUT WITH THE COLD FRONT...WOULD
EXPECT SOME CLUSTERS OR LINE OF STORMS TO FORM. STORM MOTION AND
MOVEMENT OF THE COLD FRONT WOULD SUPPORT AN EAST TO SOUTHEAST
MOVEMENT OF THE THUNDERSTORMS. FINALLY...THINK THERE WILL BE SOME
WIND THREAT DUE TO DCAPE VALUES PEAKING OVER THE SOUTH CENTRAL WHERE
THERE WILL BE LESS OF AN INFLUENCE OF CLOUDS TO AID
DESTABILIZATION. THUS...HAVE TRENDED SOME LOCATIONS UP TO
SHOWERS/THUNDERSTORMS LIKELY OVER THE CENTRAL AND WEST-CENTRAL IN
THE AFTERNOON. SPC HAS WESTERN/CENTRAL PORTIONS OF THE U.P. IN A
SLIGHT RISK AND THAT SEEMS REASONABLE AT THIS POINT ALTHOUGH THE
LIMITED SHEAR LEAVES SOME CONCERN FOR WIDESPREAD SEVERE WEATHER.
THE WARM AIR AHEAD OF THE COLD FRONT WILL PRODUCE ANOTHER WARM
DAY...ESPECIALLY OVER THE CENTRAL/EAST (HIGHS IN UPPER 80S OR
LOWER 90S). THE WEST MAY BE LIMITED BY MID CLOUDS MOVING IN AHEAD OF
THE COLD FRONT AND HAVE HIGHS IN THE 80S THERE.
AS THE UPPER TROUGH SHIFT EAST ON THURSDAY...HIGH PRESSURE WILL
BUILD OVER THE AREA WHILE AN UPPER RIDGE BUILD OVER THE NORTH
CENTRAL CONUS AND CENTRAL CANADA. WITH THIS HIGH IN PLACE...EXPECT
ANOTHER PERIOD OF DRIER WEATHER INTO THE FIRST PART OF THE WEEKEND.
A SECONDARY SHORTWAVE MOVES THROUGH ON THURSDAY...BUT WITH THE DRY
ATMOSPHERE...DON/T EXPECT MUCH MORE THAN PASSING MID CLOUDS.
TEMPERATURES DURING THE LONG TERM PERIOD WILL BE COOLEST ON
THURSDAY/FRIDAY BEHIND THE COLD FRONT (HIGHS IN THE
70S)...BUT THEN AS THE HIGH SHIFTS EAST SATURDAY...SOUTH-SOUTHWEST
LOW LEVEL FLOW WILL ALLOW TEMPERATURES TO WARM BACK ABOVE NORMAL
FOR THE WEEKEND (HIGHS AROUND 80S...ALTHOUGH THE LATEST ECMWF IS
SHOWING VALUES NEAR 90).
MODELS DIFFER SOMEWHAT FOR SATURDAY INTO MONDAY...DUE TO CONVECTION
FIRING OR NOT FIRING ALONG THE REMNANTS OF THE COLD FRONT
STRETCHING FROM SOUTHERN MINNESOTA THROUGH THE OHIO RIVER VALLEY.
THE ECMWF HAS BEEN SHOWING THIS FRONT SLOWLY PUSHING NORTH AS A
WARM FRONT THROUGH THE WEEKEND...WHICH WOULD GIVE BETTER CHANCES
FOR PRECIPITATION FOR THE END OF THE WEEKEND INTO THE BEGINNING OF
NEXT WEEK. THE GFS ON THE OTHERHAND AS BEEN SHOWING A STRONGER HIGH
LINGERING OVER THE AREA AND KEEPING THE BROAD AREA OF LOW PRESSURE
FOCUSED IN THE DAKOTAS (SIMILAR TO WHAT WE HAVE EXPERIENCED OVER
THE LAST COUPLE OF DAYS). BOTH MODELS HAVE BEEN VARYING ON THEIR
SOLUTIONS OVER THE LAST COUPLE OF DAYS...SO CONFIDENCE IS LIMITED
THIS FAR OUT. THEREFORE...WILL FOLLOW A GENERAL CONSENSUS WITH
CHANCE OR SLIGHT CHANCE POPS FOR THE WEEKEND INTO EARLY NEXT WEEK.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 128 PM EDT MON AUG 19 2013
WITH RELATIVELY DRY LOW-LEVELS PERSISTING...VFR CONDITIONS ARE
EXPECTED THRU THIS FCST PERIOD AT KIWD/KCMX/KSAW. A WEAK DISTURBANCE
PASSING OVER THE UPPER LAKES COMBINED WITH BUILDING DAYTIME
INSTABILITY COULD SPARK ISOLD CONVECTION THIS AFTN WHICH MIGHT
AFFECT KIWD/KSAW. HOWEVER...CONFIDENCE IN DEVELOPMENT/LOCATION OF
ANY SHRA/TSRA IS VERY LOW. SO...NO MENTION OF SHRA/TSRA WAS INCLUDED
IN THIS FCST. AS WITH RECENT NIGHTS...INCREASING SW WINDS TONIGHT
ABOVE NOCTURNAL INVERSION WILL APPROACH LLWS CRITERIA.
&&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 422 PM EDT MON AUG 19 2013
OVERALL...EXPECT WINDS LESS THAN 20KT THRU THE PERIOD AS A
RELATIVELY WEAK PRES GRADIENT TYPICAL OF SUMMER PERSISTS OVER THE
GREAT LAKES REGION. ONE PERIOD OF STRONGER WINDS (GUSTS TO 20-25KT)
MAY OCCUR TUE NIGHT AS PRES GRADIENT TIGHTENS DUE TO APPROACHING
COLD FRONT. THE ARRIVAL OF MORE HUMID AIR TUE/WED MAY RESULT IN SOME
FOG FORMATION OVER THE COOLER LAKE WATERS. HOWEVER...FOG WILL BE
MUCH MORE LIKELY TO DEVELOP IF SOME SHOWERS OCCUR OVER THE LAKE. ANY
FOG WILL DISSIPATE WED AFTN/EVENING FOLLOWING A COLD FRONTAL PASSAGE
AND THE ARRIVAL OF DRIER AIR.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...ROLFSON
LONG TERM...SRF
AVIATION...ROLFSON
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
129 PM EDT MON AUG 19 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 359 AM EDT MON AUG 19 2013
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW A ZONAL FLOW OVER
SRN CANADA TO THE N OF UPR RDG EXTENDING FM THE WRN PLAINS INTO THE
GREAT LKS. THE WX OVER UPR MI IS QUIET EARLY THIS MRNG...WITH
DRY/STABLE AIRMASS DEPICTED ON THE 00Z MPX/GRB RAOBS DOMINATING THE
AREA. THERE ARE 2 SHRTWVS EMBEDDED IN THE ZONAL FLOW THAT ARE OF
CONCERN. THE FIRST OF THESE IS MOVING EWD THRU THE DAKOTAS
AND ARPCHG NW MN...ACCOMPANIED BY SCT SHRA/TS. THE SECOND IS MOVING
THRU NW ONTARIO WITH A CLUSTER OF SHRA/TS NW OF LK NIPIGON...BUT
SOME ISOLD SHRA/TS WITHIN THE COMMA TAIL OF THIS FEATURE EXTEND
FARTHER S INTO THE MN ARROWHEAD UNDER SOME H85-5 QVECTOR CNVGC
ASSOCIATED WITH FAIRLY VIGOROUS H85 THETA E ADVECTION IN ADVANCE OF
AXIS OF HIER H85 DEWPTS UP TO 15C AT ABERDEEN SDAKOTA AND 13C AT
INL. WHILE THE 00Z MPX/GRB RAOBS ARE QUIET DRY/STABLE WITH KINX OF
0/-2 RESPECTIVELY AND PWAT ARND 0.75 INCH /NEAR 75 PCT OF
NORMAL/...THE 00Z INL RAOB IS MORE MOIST AND CONDITIONALLY
UNSTABLE...WITH KINX OF 36 AND PWAT 1.47 INCH /175 PCT OF NORMAL/.
DESPITE THE RATHER IMPRESSIVE MOISTENING...LATEST TRENDS INDICATE
FEW IF ANY LTG STRIKES WITHIN THE CONVECTION.
MAIN FCST CONCERNS IN THE SHORT TERM ARE RELATED TO PCPN CHCS
ASSOCIATED WITH PAIR OF SHRTWVS NOTED ABOVE.
TDAY...SHRTWVS MOVING INTO MN AND THRU ONTARIO ARE PROGGED TO
CONTINUE DRIFTING E THRU THE DAY. AS AXIS OF VIGOROUS H85 THETA E
ADVECTION/H85-5 QVECTOR CNVGC SHIFT E THIS MRNG...EXPECT SOME ISOLD
SHRA TO INVADE THE WRN COUNTIES. BUT MODEL GUIDANCE IN GENERAL SHOWS
THE SHARPER H85-5 QVECTOR CNVGC ASSOCIATED WITH THE ONTARIO SHRTWV
PASSING TO THE N AND MORE VIGOROUS FORCING IN ADVANCE OF THE MN
DISTURBANCE FOCUSING TO THE S BEFORE FADING IN THE AFTN. SO GOING
FCST SHOWING A DIMINISHING TREND IN THE POPS THRU THE MRNG SEEMS ON
TRACK. GIVEN OBSVD LTG STRIKES AND TENDENCY FOR DIMINISHING DYNAMIC
SUPPORT...REMOVED MENTION OF TS THIS MRNG. WHETHER DAYTIME HEATING
/DESTABILIZATION CAN REINVIGORATE/SUSTAIN ANY CONVECTION WL BE THE
CONCERN FOR THE AFTN. IN FACT...THE 00Z REGIONAL GEM AND GFS ARE THE
ONLY MODELS THAT GENERATE ANY PCPN OVER THE CWA THIS AFTN. THE GFS
FCST SDNGS SHOW RATHER UNIMPRESSIVE LAPSE RATES WITH A TENDENCY FOR
A PERSISTENT CAP AND WARMING MID LVL TEMPS IN THE 18Z-24Z TIME FRAME
ASSOCIATED WITH THE FADING DYNAMIC SUPPORT. NAM/GFS MOS POPS ARE
UNDER 10 AT MOST PLACES...BUT OPTED TO RETAIN SCHC POPS TO INCLUDE
TS WITH ARRIVAL OF MOISTER AIR/PWAT UP TO 1.5 INCH AND SFC TEMPS
EXPECTED TO REACH ARND 85 THAT WL LIFT MUCAPE UP TO 800-1000J/KG
AWAY FM THE MODERATING INFLUENCE OF THE LKS.
TNGT...WITH RISING HGTS/DNVA/DEEP QVECTOR DVGC...TNGT WL BE DRY AS
ANY AFTN CONVECTION FIZZLES BEFORE SUNSET UNDER THE MID LVL
WARMING/LOWERING SUN ANGLE. ALTHOUGH SKIES WL TURN MOCLR...STEADY SW
WIND SHOULD ACT TO LIMIT THE DIURNAL TEMP FALL. THE WARMEST MIN
TEMPS ARE MOST LIKELY NEAR LK SUP OVER THE W HALF...WHERE THE PRES
GRADIENT WL BE A BIT TIGHER/H925 WINDS 20-25 KTS AND THIS FLOW WL
DOWNSLOPE.
.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 359 AM EDT MON AUG 19 2013
STARTING TUE...THE CWA WILL BE BETWEEN A SFC HIGH OVER THE
ATLANTIC/ERN CONUS AND AND SFC TROUGH FROM HUDSON BAY INTO THE NRN
PLAINS STATES. SOME OF THE MODELS ARE HINTING AT SOME PRECIP TUE
AFTERNOON...BUT ANY PRECIP SHOULD BE ISOLATED AT BEST GIVEN THAT
THERE WILL NOT BE MUCH MOISTURE AVAILABLE. BEST CHANCE FOR ISOLATED
SHOWERS AND THUNDERSTORMS WILL BE OVER NCENTRAL UPPER MI WHERE LAKE
BREEZE CONVERGENCE WILL HELP ENCOURAGE CONVECTION ALONG. 850MB TEMPS
AT 18Z TUE WILL BE RIGHT AROUND 17-18C AND WITH MOSTLY SUNNY SKIES
SHOULD BE ABLE TO GET HIGH TEMPS IN THE 80S TO AROUND 90.
MODELS ARE IN BETTER AGREEMENT FOR THAT TROUGH/COLD FRONT TO THE NW
TO DROP ACROSS THE CWA ON WED/WED NIGHT...BUT THERE REMAINS SOME
SUBTLE YET IMPORTANT UNCERTAINTY FOR THE SYSTEM. MAIN QUESTION IS
WITH THE EXACT TIMING OF THE COLD FRONT...WHICH EVEN THOUGH MODELS
AGREE WELL ON...THINK THAT IT WILL NOT BE CERTAIN UNTIL A LATER
TIME. THE TIMING OF FROPA IS IMPORTANT BECAUSE WITH 850MB TEMPS UP
TO 20C...TEMPS MAY BE COLDER THAN WHAT IS IN THE FORECAST /MAINLY
OVER THE W WHERE THE FRONT MAY COME IN EARLIER THAN PREVIOUSLY
INDICATED BY MODELS/. THINK THAT AREAS THAT HAVE NOT BEEN IMPACTED
BY THE FRONT /AND ASSOCIATED PRECIP AND CLOUD COVER/ BY AROUND PEAK
HEATING TIME WILL GET INTO THE LOW 90S /AWAY FROM LAKE MICHIGAN/.
SO...IF THE COLD FRONT COMES IN AS THE MODELS ARE CURRENTLY
INDICATING /INTO WRN UPPER MI BY 18Z WED AND CENTRAL UPPER MI BY 00Z
THU/...PORTIONS OF WRN UPPER MI WOULD SEE HIGH TEMPS POSSIBLY 10
DEGREES COLDER THAN WHAT THE PREVIOUS FORECAST HAD. ON THE FLIP
SIDE...THE FRONT COULD VERY WELL COME IN LATER THAN INDICATED BY
MODELS...MEANING THE PREVIOUS FORECAST MAY BE RIGHT ON. AT THIS
POINT WITH THE UNCERTAINTY...WILL NOT CHANGE TEMPS MUCH FOR WED. THE
OTHER IMPACT WITH FROPA TIMING IS ON CONVECTION...SIGNIFICANT SBCAPE
VALUES OF 1500-2500J/KG SHOULD BE PRESENT IN AIRMASS AHEAD OF COLD
FRONT AROUND PEAK HEATING...SO WHEN THE FRONT MOVES THROUGH WILL
DETERMINE STRENGTH/COVERAGE OF CONVECTION. AT THIS POINT...NOT TOO
EXCITED WITH AREAL EXTENT OF CONVECTION GIVEN THAT MOISTURE WILL BE
SOMEWHAT LIMITED /AT LEAST EARLY ON/. AT THE SAME TIME...THAT DRY
AIR WILL HELP DCAPE VALUES GET UP TO AROUND 1000J/KG AND WITH HIGH
FREEZING LEVEL AROUND 14KFT...MAIN THREAT FROM ANY STRONGER OR
ISOLATED SEVERE STORMS WOULD BE STRONG WINDS.
THURSDAY CERTAINLY LOOKS COOLER AND DRIER AS 850MB TEMPS AT 18Z THU
WILL BE AROUND 13C WITH SFC HIGH PRESSURE MOVING IN FROM THE W. HIGH
TEMPS LOOK TO BE IN THE 70S TO AROUND 80 OVER THE SCENTRAL CWA.
AMPLIFIED UPPER LEVEL RIDGE WILL BE WELL TO THE W OF THE CWA.
MODELS IN MUCH BETTER AGREEMENT FOR FRI WITH HAVING THE SFC HIGH
EXIT TO THE E ON FRI AS THE UPPER RIDGE AXIS MOVES OVERHEAD LATE IN
THE DAY. WITH SLY FLOW NOT KICKING IN AND UPPER RIDGE NOT ARRIVING
UNTIL LATE IN THE DAY OR UNTIL FRI NIGHT...WILL NOT HAVE SUFFICIENT
ADVECTION OF WARMER AIRMASS INTO THE AREA. HIGH TEMPS LOOK SIMILAR
OR A DEGREE OR TWO COOLER THAN THURSDAY...WITH HIGHS PRIMARILY IN
THE 70S /WITH SOME COOLER SPOTS NEAR LAKE SUPERIOR/.
UNCERTAINTY INCREASES CONSIDERABLY FOR SAT AND SUN DUE TO MODEL
DISAGREEMENT AND RUN TO RUN DISCONTINUITY. WILL JUST USE CONSENSUS
OF MODELS FOR THIS PERIOD.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 128 PM EDT MON AUG 19 2013
WITH RELATIVELY DRY LOW-LEVELS PERSISTING...VFR CONDITIONS ARE
EXPECTED THRU THIS FCST PERIOD AT KIWD/KCMX/KSAW. A WEAK DISTURBANCE
PASSING OVER THE UPPER LAKES COMBINED WITH BUILDING DAYTIME
INSTABILITY COULD SPARK ISOLD CONVECTION THIS AFTN WHICH MIGHT
AFFECT KIWD/KSAW. HOWEVER...CONFIDENCE IN DEVELOPMENT/LOCATION OF
ANY SHRA/TSRA IS VERY LOW. SO...NO MENTION OF SHRA/TSRA WAS INCLUDED
IN THIS FCST. AS WITH RECENT NIGHTS...INCREASING SW WINDS TONIGHT
ABOVE NOCTURNAL INVERSION WILL APPROACH LLWS CRITERIA.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 359 AM EDT MON AUG 19 2013
OVERALL...EXPECT WINDS LESS THAN 20 KTS THRU THE PERIOD AS A
RELATIVELY WEAK PRES GRADIENT TYPICAL OF SUMMER PERSISTS OVER THE
GREAT LAKES REGION. THE ARRIVAL OF MORE HUMID AIR FOR TUE/WED MAY
RESULT IN SOME FOG FORMATION OVER THE COOLER LAKE WATERS.
HOWEVER...FOG WILL BE MUCH MORE LIKELY TO DEVELOP IF SOME SHOWERS
OCCUR OVER THE LAKE. ANY FOG WILL DISSIPATE THU FOLLOWING A COLD
FRONTAL PASSAGE AND THE ARRIVAL OF DRIER AIR.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...KC
LONG TERM...TITUS
AVIATION...ROLFSON
MARINE...KC
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
701 AM EDT MON AUG 19 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 359 AM EDT MON AUG 19 2013
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW A ZONAL FLOW OVER
SRN CANADA TO THE N OF UPR RDG EXTENDING FM THE WRN PLAINS INTO THE
GREAT LKS. THE WX OVER UPR MI IS QUIET EARLY THIS MRNG...WITH
DRY/STABLE AIRMASS DEPICTED ON THE 00Z MPX/GRB RAOBS DOMINATING THE
AREA. THERE ARE 2 SHRTWVS EMBEDDED IN THE ZONAL FLOW THAT ARE OF
CONCERN. THE FIRST OF THESE IS MOVING EWD THRU THE DAKOTAS
AND ARPCHG NW MN...ACCOMPANIED BY SCT SHRA/TS. THE SECOND IS MOVING
THRU NW ONTARIO WITH A CLUSTER OF SHRA/TS NW OF LK NIPIGON...BUT
SOME ISOLD SHRA/TS WITHIN THE COMMA TAIL OF THIS FEATURE EXTEND
FARTHER S INTO THE MN ARROWHEAD UNDER SOME H85-5 QVECTOR CNVGC
ASSOCIATED WITH FAIRLY VIGOROUS H85 THETA E ADVECTION IN ADVANCE OF
AXIS OF HIER H85 DEWPTS UP TO 15C AT ABERDEEN SDAKOTA AND 13C AT
INL. WHILE THE 00Z MPX/GRB RAOBS ARE QUIET DRY/STABLE WITH KINX OF
0/-2 RESPECTIVELY AND PWAT ARND 0.75 INCH /NEAR 75 PCT OF
NORMAL/...THE 00Z INL RAOB IS MORE MOIST AND CONDITIONALLY
UNSTABLE...WITH KINX OF 36 AND PWAT 1.47 INCH /175 PCT OF NORMAL/.
DESPITE THE RATHER IMPRESSIVE MOISTENING...LATEST TRENDS INDICATE
FEW IF ANY LTG STRIKES WITHIN THE CONVECTION.
MAIN FCST CONCERNS IN THE SHORT TERM ARE RELATED TO PCPN CHCS
ASSOCIATED WITH PAIR OF SHRTWVS NOTED ABOVE.
TDAY...SHRTWVS MOVING INTO MN AND THRU ONTARIO ARE PROGGED TO
CONTINUE DRIFTING E THRU THE DAY. AS AXIS OF VIGOROUS H85 THETA E
ADVECTION/H85-5 QVECTOR CNVGC SHIFT E THIS MRNG...EXPECT SOME ISOLD
SHRA TO INVADE THE WRN COUNTIES. BUT MODEL GUIDANCE IN GENERAL SHOWS
THE SHARPER H85-5 QVECTOR CNVGC ASSOCIATED WITH THE ONTARIO SHRTWV
PASSING TO THE N AND MORE VIGOROUS FORCING IN ADVANCE OF THE MN
DISTURBANCE FOCUSING TO THE S BEFORE FADING IN THE AFTN. SO GOING
FCST SHOWING A DIMINISHING TREND IN THE POPS THRU THE MRNG SEEMS ON
TRACK. GIVEN OBSVD LTG STRIKES AND TENDENCY FOR DIMINISHING DYNAMIC
SUPPORT...REMOVED MENTION OF TS THIS MRNG. WHETHER DAYTIME HEATING
/DESTABILIZATION CAN REINVIGORATE/SUSTAIN ANY CONVECTION WL BE THE
CONCERN FOR THE AFTN. IN FACT...THE 00Z REGIONAL GEM AND GFS ARE THE
ONLY MODELS THAT GENERATE ANY PCPN OVER THE CWA THIS AFTN. THE GFS
FCST SDNGS SHOW RATHER UNIMPRESSIVE LAPSE RATES WITH A TENDENCY FOR
A PERSISTENT CAP AND WARMING MID LVL TEMPS IN THE 18Z-24Z TIME FRAME
ASSOCIATED WITH THE FADING DYNAMIC SUPPORT. NAM/GFS MOS POPS ARE
UNDER 10 AT MOST PLACES...BUT OPTED TO RETAIN SCHC POPS TO INCLUDE
TS WITH ARRIVAL OF MOISTER AIR/PWAT UP TO 1.5 INCH AND SFC TEMPS
EXPECTED TO REACH ARND 85 THAT WL LIFT MUCAPE UP TO 800-1000J/KG
AWAY FM THE MODERATING INFLUENCE OF THE LKS.
TNGT...WITH RISING HGTS/DNVA/DEEP QVECTOR DVGC...TNGT WL BE DRY AS
ANY AFTN CONVECTION FIZZLES BEFORE SUNSET UNDER THE MID LVL
WARMING/LOWERING SUN ANGLE. ALTHOUGH SKIES WL TURN MOCLR...STEADY SW
WIND SHOULD ACT TO LIMIT THE DIURNAL TEMP FALL. THE WARMEST MIN
TEMPS ARE MOST LIKELY NEAR LK SUP OVER THE W HALF...WHERE THE PRES
GRADIENT WL BE A BIT TIGHER/H925 WINDS 20-25 KTS AND THIS FLOW WL
DOWNSLOPE.
.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 359 AM EDT MON AUG 19 2013
STARTING TUE...THE CWA WILL BE BETWEEN A SFC HIGH OVER THE
ATLANTIC/ERN CONUS AND AND SFC TROUGH FROM HUDSON BAY INTO THE NRN
PLAINS STATES. SOME OF THE MODELS ARE HINTING AT SOME PRECIP TUE
AFTERNOON...BUT ANY PRECIP SHOULD BE ISOLATED AT BEST GIVEN THAT
THERE WILL NOT BE MUCH MOISTURE AVAILABLE. BEST CHANCE FOR ISOLATED
SHOWERS AND THUNDERSTORMS WILL BE OVER NCENTRAL UPPER MI WHERE LAKE
BREEZE CONVERGENCE WILL HELP ENCOURAGE CONVECTION ALONG. 850MB TEMPS
AT 18Z TUE WILL BE RIGHT AROUND 17-18C AND WITH MOSTLY SUNNY SKIES
SHOULD BE ABLE TO GET HIGH TEMPS IN THE 80S TO AROUND 90.
MODELS ARE IN BETTER AGREEMENT FOR THAT TROUGH/COLD FRONT TO THE NW
TO DROP ACROSS THE CWA ON WED/WED NIGHT...BUT THERE REMAINS SOME
SUBTLE YET IMPORTANT UNCERTAINTY FOR THE SYSTEM. MAIN QUESTION IS
WITH THE EXACT TIMING OF THE COLD FRONT...WHICH EVEN THOUGH MODELS
AGREE WELL ON...THINK THAT IT WILL NOT BE CERTAIN UNTIL A LATER
TIME. THE TIMING OF FROPA IS IMPORTANT BECAUSE WITH 850MB TEMPS UP
TO 20C...TEMPS MAY BE COLDER THAN WHAT IS IN THE FORECAST /MAINLY
OVER THE W WHERE THE FRONT MAY COME IN EARLIER THAN PREVIOUSLY
INDICATED BY MODELS/. THINK THAT AREAS THAT HAVE NOT BEEN IMPACTED
BY THE FRONT /AND ASSOCIATED PRECIP AND CLOUD COVER/ BY AROUND PEAK
HEATING TIME WILL GET INTO THE LOW 90S /AWAY FROM LAKE MICHIGAN/.
SO...IF THE COLD FRONT COMES IN AS THE MODELS ARE CURRENTLY
INDICATING /INTO WRN UPPER MI BY 18Z WED AND CENTRAL UPPER MI BY 00Z
THU/...PORTIONS OF WRN UPPER MI WOULD SEE HIGH TEMPS POSSIBLY 10
DEGREES COLDER THAN WHAT THE PREVIOUS FORECAST HAD. ON THE FLIP
SIDE...THE FRONT COULD VERY WELL COME IN LATER THAN INDICATED BY
MODELS...MEANING THE PREVIOUS FORECAST MAY BE RIGHT ON. AT THIS
POINT WITH THE UNCERTAINTY...WILL NOT CHANGE TEMPS MUCH FOR WED. THE
OTHER IMPACT WITH FROPA TIMING IS ON CONVECTION...SIGNIFICANT SBCAPE
VALUES OF 1500-2500J/KG SHOULD BE PRESENT IN AIRMASS AHEAD OF COLD
FRONT AROUND PEAK HEATING...SO WHEN THE FRONT MOVES THROUGH WILL
DETERMINE STRENGTH/COVERAGE OF CONVECTION. AT THIS POINT...NOT TOO
EXCITED WITH AREAL EXTENT OF CONVECTION GIVEN THAT MOISTURE WILL BE
SOMEWHAT LIMITED /AT LEAST EARLY ON/. AT THE SAME TIME...THAT DRY
AIR WILL HELP DCAPE VALUES GET UP TO AROUND 1000J/KG AND WITH HIGH
FREEZING LEVEL AROUND 14KFT...MAIN THREAT FROM ANY STRONGER OR
ISOLATED SEVERE STORMS WOULD BE STRONG WINDS.
THURSDAY CERTAINLY LOOKS COOLER AND DRIER AS 850MB TEMPS AT 18Z THU
WILL BE AROUND 13C WITH SFC HIGH PRESSURE MOVING IN FROM THE W. HIGH
TEMPS LOOK TO BE IN THE 70S TO AROUND 80 OVER THE SCENTRAL CWA.
AMPLIFIED UPPER LEVEL RIDGE WILL BE WELL TO THE W OF THE CWA.
MODELS IN MUCH BETTER AGREEMENT FOR FRI WITH HAVING THE SFC HIGH
EXIT TO THE E ON FRI AS THE UPPER RIDGE AXIS MOVES OVERHEAD LATE IN
THE DAY. WITH SLY FLOW NOT KICKING IN AND UPPER RIDGE NOT ARRIVING
UNTIL LATE IN THE DAY OR UNTIL FRI NIGHT...WILL NOT HAVE SUFFICIENT
ADVECTION OF WARMER AIRMASS INTO THE AREA. HIGH TEMPS LOOK SIMILAR
OR A DEGREE OR TWO COOLER THAN THURSDAY...WITH HIGHS PRIMARILY IN
THE 70S /WITH SOME COOLER SPOTS NEAR LAKE SUPERIOR/.
UNCERTAINTY INCREASES CONSIDERABLY FOR SAT AND SUN DUE TO MODEL
DISAGREEMENT AND RUN TO RUN DISCONTINUITY. WILL JUST USE CONSENSUS
OF MODELS FOR THIS PERIOD.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 701 AM EDT MON AUG 19 2013
A LO PRES TROF CROSSING THE AREA WL BRING SOME ISOLD -SHRA AND
PERHAPS A TS TO THE TAF SITES W-E TODAY. EVEN IF THERE IS A SHRA AT
ONE OF THE AIRPORTS...CONDITIONS ARE LIKELY TO REMAIN VFR GIVEN THE
RELATIVELY DRY NATURE OF THE AIRMASS. OTRW...EXPECT A GUSTY SW WIND
UNDER THE SHARPER PRES GRADIENT IN ADVANCE OF THE APRCHG TROF AND
WITH DAYTIME HEATING/MIXING. LARGE SCALE SUBSIDENCE BEHIND THE TROF
AND LOSS OF DAYTIME HEATING WL ALLOW FOR DRY/VFR CONDITIONS TNGT.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 359 AM EDT MON AUG 19 2013
OVERALL...EXPECT WINDS LESS THAN 20 KTS THRU THE PERIOD AS A
RELATIVELY WEAK PRES GRADIENT TYPICAL OF SUMMER PERSISTS OVER THE
GREAT LAKES REGION. THE ARRIVAL OF MORE HUMID AIR FOR TUE/WED MAY
RESULT IN SOME FOG FORMATION OVER THE COOLER LAKE WATERS.
HOWEVER...FOG WILL BE MUCH MORE LIKELY TO DEVELOP IF SOME SHOWERS
OCCUR OVER THE LAKE. ANY FOG WILL DISSIPATE THU FOLLOWING A COLD
FRONTAL PASSAGE AND THE ARRIVAL OF DRIER AIR.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...KC
LONG TERM...TITUS
AVIATION...KC
MARINE...KC
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
404 AM EDT MON AUG 19 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 359 AM EDT MON AUG 19 2013
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW A ZONAL FLOW OVER
SRN CANADA TO THE N OF UPR RDG EXTENDING FM THE WRN PLAINS INTO THE
GREAT LKS. THE WX OVER UPR MI IS QUIET EARLY THIS MRNG...WITH
DRY/STABLE AIRMASS DEPICTED ON THE 00Z MPX/GRB RAOBS DOMINATING THE
AREA. THERE ARE 2 SHRTWVS EMBEDDED IN THE ZONAL FLOW THAT ARE OF
CONCERN. THE FIRST OF THESE IS MOVING EWD THRU THE DAKOTAS
AND ARPCHG NW MN...ACCOMPANIED BY SCT SHRA/TS. THE SECOND IS MOVING
THRU NW ONTARIO WITH A CLUSTER OF SHRA/TS NW OF LK NIPIGON...BUT
SOME ISOLD SHRA/TS WITHIN THE COMMA TAIL OF THIS FEATURE EXTEND
FARTHER S INTO THE MN ARROWHEAD UNDER SOME H85-5 QVECTOR CNVGC
ASSOCIATED WITH FAIRLY VIGOROUS H85 THETA E ADVECTION IN ADVANCE OF
AXIS OF HIER H85 DEWPTS UP TO 15C AT ABERDEEN SDAKOTA AND 13C AT
INL. WHILE THE 00Z MPX/GRB RAOBS ARE QUIET DRY/STABLE WITH KINX OF
0/-2 RESPECTIVELY AND PWAT ARND 0.75 INCH /NEAR 75 PCT OF
NORMAL/...THE 00Z INL RAOB IS MORE MOIST AND CONDITIONALLY
UNSTABLE...WITH KINX OF 36 AND PWAT 1.47 INCH /175 PCT OF NORMAL/.
DESPITE THE RATHER IMPRESSIVE MOISTENING...LATEST TRENDS INDICATE
FEW IF ANY LTG STRIKES WITHIN THE CONVECTION.
MAIN FCST CONCERNS IN THE SHORT TERM ARE RELATED TO PCPN CHCS
ASSOCIATED WITH PAIR OF SHRTWVS NOTED ABOVE.
TDAY...SHRTWVS MOVING INTO MN AND THRU ONTARIO ARE PROGGED TO
CONTINUE DRIFTING E THRU THE DAY. AS AXIS OF VIGOROUS H85 THETA E
ADVECTION/H85-5 QVECTOR CNVGC SHIFT E THIS MRNG...EXPECT SOME ISOLD
SHRA TO INVADE THE WRN COUNTIES. BUT MODEL GUIDANCE IN GENERAL SHOWS
THE SHARPER H85-5 QVECTOR CNVGC ASSOCIATED WITH THE ONTARIO SHRTWV
PASSING TO THE N AND MORE VIGOROUS FORCING IN ADVANCE OF THE MN
DISTURBANCE FOCUSING TO THE S BEFORE FADING IN THE AFTN. SO GOING
FCST SHOWING A DIMINISHING TREND IN THE POPS THRU THE MRNG SEEMS ON
TRACK. GIVEN OBSVD LTG STRIKES AND TENDENCY FOR DIMINISHING DYNAMIC
SUPPORT...REMOVED MENTION OF TS THIS MRNG. WHETHER DAYTIME HEATING
/DESTABILIZATION CAN REINVIGORATE/SUSTAIN ANY CONVECTION WL BE THE
CONCERN FOR THE AFTN. IN FACT...THE 00Z REGIONAL GEM AND GFS ARE THE
ONLY MODELS THAT GENERATE ANY PCPN OVER THE CWA THIS AFTN. THE GFS
FCST SDNGS SHOW RATHER UNIMPRESSIVE LAPSE RATES WITH A TENDENCY FOR
A PERSISTENT CAP AND WARMING MID LVL TEMPS IN THE 18Z-24Z TIME FRAME
ASSOCIATED WITH THE FADING DYNAMIC SUPPORT. NAM/GFS MOS POPS ARE
UNDER 10 AT MOST PLACES...BUT OPTED TO RETAIN SCHC POPS TO INCLUDE
TS WITH ARRIVAL OF MOISTER AIR/PWAT UP TO 1.5 INCH AND SFC TEMPS
EXPECTED TO REACH ARND 85 THAT WL LIFT MUCAPE UP TO 800-1000J/KG
AWAY FM THE MODERATING INFLUENCE OF THE LKS.
TNGT...WITH RISING HGTS/DNVA/DEEP QVECTOR DVGC...TNGT WL BE DRY AS
ANY AFTN CONVECTION FIZZLES BEFORE SUNSET UNDER THE MID LVL
WARMING/LOWERING SUN ANGLE. ALTHOUGH SKIES WL TURN MOCLR...STEADY SW
WIND SHOULD ACT TO LIMIT THE DIURNAL TEMP FALL. THE WARMEST MIN
TEMPS ARE MOST LIKELY NEAR LK SUP OVER THE W HALF...WHERE THE PRES
GRADIENT WL BE A BIT TIGHER/H925 WINDS 20-25 KTS AND THIS FLOW WL
DOWNSLOPE.
.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 359 AM EDT MON AUG 19 2013
STARTING TUE...THE CWA WILL BE BETWEEN A SFC HIGH OVER THE
ATLANTIC/ERN CONUS AND AND SFC TROUGH FROM HUDSON BAY INTO THE NRN
PLAINS STATES. SOME OF THE MODELS ARE HINTING AT SOME PRECIP TUE
AFTERNOON...BUT ANY PRECIP SHOULD BE ISOLATED AT BEST GIVEN THAT
THERE WILL NOT BE MUCH MOISTURE AVAILABLE. BEST CHANCE FOR ISOLATED
SHOWERS AND THUNDERSTORMS WILL BE OVER NCENTRAL UPPER MI WHERE LAKE
BREEZE CONVERGENCE WILL HELP ENCOURAGE CONVECTION ALONG. 850MB TEMPS
AT 18Z TUE WILL BE RIGHT AROUND 17-18C AND WITH MOSTLY SUNNY SKIES
SHOULD BE ABLE TO GET HIGH TEMPS IN THE 80S TO AROUND 90.
MODELS ARE IN BETTER AGREEMENT FOR THAT TROUGH/COLD FRONT TO THE NW
TO DROP ACROSS THE CWA ON WED/WED NIGHT...BUT THERE REMAINS SOME
SUBTLE YET IMPORTANT UNCERTAINTY FOR THE SYSTEM. MAIN QUESTION IS
WITH THE EXACT TIMING OF THE COLD FRONT...WHICH EVEN THOUGH MODELS
AGREE WELL ON...THINK THAT IT WILL NOT BE CERTAIN UNTIL A LATER
TIME. THE TIMING OF FROPA IS IMPORTANT BECAUSE WITH 850MB TEMPS UP
TO 20C...TEMPS MAY BE COLDER THAN WHAT IS IN THE FORECAST /MAINLY
OVER THE W WHERE THE FRONT MAY COME IN EARLIER THAN PREVIOUSLY
INDICATED BY MODELS/. THINK THAT AREAS THAT HAVE NOT BEEN IMPACTED
BY THE FRONT /AND ASSOCIATED PRECIP AND CLOUD COVER/ BY AROUND PEAK
HEATING TIME WILL GET INTO THE LOW 90S /AWAY FROM LAKE MICHIGAN/.
SO...IF THE COLD FRONT COMES IN AS THE MODELS ARE CURRENTLY
INDICATING /INTO WRN UPPER MI BY 18Z WED AND CENTRAL UPPER MI BY 00Z
THU/...PORTIONS OF WRN UPPER MI WOULD SEE HIGH TEMPS POSSIBLY 10
DEGREES COLDER THAN WHAT THE PREVIOUS FORECAST HAD. ON THE FLIP
SIDE...THE FRONT COULD VERY WELL COME IN LATER THAN INDICATED BY
MODELS...MEANING THE PREVIOUS FORECAST MAY BE RIGHT ON. AT THIS
POINT WITH THE UNCERTAINTY...WILL NOT CHANGE TEMPS MUCH FOR WED. THE
OTHER IMPACT WITH FROPA TIMING IS ON CONVECTION...SIGNIFICANT SBCAPE
VALUES OF 1500-2500J/KG SHOULD BE PRESENT IN AIRMASS AHEAD OF COLD
FRONT AROUND PEAK HEATING...SO WHEN THE FRONT MOVES THROUGH WILL
DETERMINE STRENGTH/COVERAGE OF CONVECTION. AT THIS POINT...NOT TOO
EXCITED WITH AREAL EXTENT OF CONVECTION GIVEN THAT MOISTURE WILL BE
SOMEWHAT LIMITED /AT LEAST EARLY ON/. AT THE SAME TIME...THAT DRY
AIR WILL HELP DCAPE VALUES GET UP TO AROUND 1000J/KG AND WITH HIGH
FREEZING LEVEL AROUND 14KFT...MAIN THREAT FROM ANY STRONGER OR
ISOLATED SEVERE STORMS WOULD BE STRONG WINDS.
THURSDAY CERTAINLY LOOKS COOLER AND DRIER AS 850MB TEMPS AT 18Z THU
WILL BE AROUND 13C WITH SFC HIGH PRESSURE MOVING IN FROM THE W. HIGH
TEMPS LOOK TO BE IN THE 70S TO AROUND 80 OVER THE SCENTRAL CWA.
AMPLIFIED UPPER LEVEL RIDGE WILL BE WELL TO THE W OF THE CWA.
MODELS IN MUCH BETTER AGREEMENT FOR FRI WITH HAVING THE SFC HIGH
EXIT TO THE E ON FRI AS THE UPPER RIDGE AXIS MOVES OVERHEAD LATE IN
THE DAY. WITH SLY FLOW NOT KICKING IN AND UPPER RIDGE NOT ARRIVING
UNTIL LATE IN THE DAY OR UNTIL FRI NIGHT...WILL NOT HAVE SUFFICIENT
ADVECTION OF WARMER AIRMASS INTO THE AREA. HIGH TEMPS LOOK SIMILAR
OR A DEGREE OR TWO COOLER THAN THURSDAY...WITH HIGHS PRIMARILY IN
THE 70S /WITH SOME COOLER SPOTS NEAR LAKE SUPERIOR/.
UNCERTAINTY INCREASES CONSIDERABLY FOR SAT AND SUN DUE TO MODEL
DISAGREEMENT AND RUN TO RUN DISCONTINUITY. WILL JUST USE CONSENSUS
OF MODELS FOR THIS PERIOD.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 121 AM EDT MON AUG 19 2013
WITH SW FLOW OF RELATIVELY DRY AIR...EXPECT VFR CONDITIONS TO
PREVAIL THRU THIS FCST PERIOD AT KIWD/KCMX/KSAW. INCREASING SW WINDS
ABOVE NOCTURNAL INVERSION LATE TONIGHT WILL APPROACH LLWS CRITERIA.
ALSO A DISTURBANCE APPROACHING FROM THE W MAY BRING ISOLD/SCT
CONVECTION INTO CENTRAL UPPER MI LATE MON AFTERNOON. AT THIS
POINT...CONFIDENCE IS VERY LOW ON LOCATION/COVERAGE OF SHRA/TSRA.
THUS...WILL ONLY MENTION VCSH AT KSAW AROUND 21Z MON.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 359 AM EDT MON AUG 19 2013
OVERALL...EXPECT WINDS LESS THAN 20 KTS THRU THE PERIOD AS A
RELATIVELY WEAK PRES GRADIENT TYPICAL OF SUMMER PERSISTS OVER THE
GREAT LAKES REGION. THE ARRIVAL OF MORE HUMID AIR FOR TUE/WED MAY
RESULT IN SOME FOG FORMATION OVER THE COOLER LAKE WATERS.
HOWEVER...FOG WILL BE MUCH MORE LIKELY TO DEVELOP IF SOME SHOWERS
OCCUR OVER THE LAKE. ANY FOG WILL DISSIPATE THU FOLLOWING A COLD
FRONTAL PASSAGE AND THE ARRIVAL OF DRIER AIR.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...KC
LONG TERM...TITUS
AVIATION...VOSS
MARINE...KC
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
121 AM EDT MON AUG 19 2013
.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 409 PM EDT SUN AUG 18 2013
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A RIDGE OVER THE SRN U.S.
ROCKIES WITH A TROF LINGERING OVER THE LWR MISSISSIPPI VALLEY. TO
THE N...ZONAL FLOW DOMINATES SRN CANADA. THERE ARE A COUPLE OF
SHORTWAVES OF INTEREST UPSTREAM IN THIS ZONAL FLOW. THE FIRST IS
OVER SE MANITOBA...AND THE SECOND IS OVER SRN SASKATCHEWAN/ERN MT.
THE FIRST WAVE IS GENERATING CONVECTION OVER FAR SE MANITOBA INTO
ADJACENT NRN ONTARIO. THE SECOND WAVE IS GENERATING SCT SHRA/TSRA
OVER THE WRN DAKOTAS INTO SRN SASKATCHEWAN. CLOSER TO HOME...12Z
SOUNDINGS FROM KGRB/KMPX SHOWED VERY DRY MID LEVELS AND A HEALTHY
CAP...AND THUS NO PCPN IS OCCURRING OVER THE FCST AREA THIS AFTN.
SOME CI AND A RATHER THICK ELEVATED SMOKE LAYER HAS HELD TEMPS DOWN
A BIT FROM EXPECTATIONS WITH READINGS MOSTLY IN THE UPPER 70S TO LOW
80S AS OF 19Z. NEAR LAKE MICHIGAN...SOUTHERLY WINDS OFF THE LAKE ARE
HOLDING TEMPS TO THE LOW/MID 70S.
AFTER A DRY START TO THE SHORT TERM...ATTENTION TURNS TO THE
POTENTIAL OF SHRA/TSRA LATE TONIGHT/MON AS THE PAIR OF SHORTWAVES
CURRENTLY OVER SE MANITOBA AND OVER SRN SASKATCHEWAN/ERN MT MOVES
EASTWARD. INITIAL DRY/CAPPED AIR MASS WILL ENSURE DRY WEATHER ACROSS
THE FCST AREA THIS EVENING. THEN...SW FLOW AHEAD OF SHORTWAVES WILL
TRANSPORT INTO THE UPPER LAKES THE MORE HUMID AIR MASS EVIDENT OVER
THE CNTRL PLAINS THIS MORNING PER 12Z RAOBS. WHILE THE ANTECEDENT
DRY AIR WILL WORK TO DELAY SHRA...DEGREE OF MOISTENING/MAGNITUDE OF
THETA-E ADVECTION SUGGESTS THERE WILL BE SOME RISK OF PCPN. THERE MAY
BE 2 RATHER DISTINCT CLUSTERS OF SCT SHRA/TSRA. THE FIRST ASSOCIATED
WITH THE SE MANITOBA SHORTWAVE COULD REACH NW LAKE SUPERIOR/ISLE
ROYALE AREA EARLY IN THE OVERNIGHT. 850-300MB THICKNESS FIELD
SUGGESTS SOME OF THE CURRENT SHRA/TSRA ASSOCIATED WITH THE WAVE MAY
TAKE A SHARP TURN TO THE RIGHT AS THEY APPROACH THE LAKE...SO IT
REMAINS TO BE SEEN WHERE THESE SHRA MAY END UP. THE SECOND AREA OF
CONVECTION MAY DEVELOP ACROSS NRN MN TOWARD WRN LAKE SUPERIOR LATE
IN THE NIGHT OR MON MORNING WITH THE FOLLOWING SHORTWAVE. IN BOTH
CASES...THERE IS AN INDICATION OF WEAKENING MOISTURE TRANSPORT
EASTWARD WITH TIME...SO SHRA WILL PROBABLY BE ON A DIMINISHING TREND
AS THEY MOVE TOWARD LAKE SUPERIOR/UPPER MI. AT THIS POINT...SEE NO
REASON TO DEVIATE MUCH FROM INHERITED FCST WHICH BROUGHT CHC POPS TO
WRN LAKE SUPERIOR OVERNIGHT AND SCHC POPS TO WRN UPPER MI LATE.
INCREASING COLUMN MOISTURE AND STIRRING S TO SW WINDS WILL WORK TO
KEEP TEMPS HIGHER THAN LAST NIGHT. EXPECT MINS IN THE MID 60S IN THE
DOWNSLOPE AREAS NEAR LAKE SUPERIOR. MINS IN THE MID 50S TO PERHAPS
AS LOW AS 50F IN TRADITIONAL COLD SPOTS SHOULD BE THE RULE INLAND.
ON MON...SHORTWAVE TROF MOVES ACROSS THE UPPER LAKES...BUT WILL BE
WEAKENING AS EVIDENT IN HEIGHT FIELD AND DEEP LAYER FORCING PER
QVECTORS. IF ANY SHRA/TSRA REACH THE W LATE TONIGHT...THEY WILL
LIKELY WEAKEN IN THE MORNING. DURING THE AFTN...MLCAPE IS FCST TO
INCREASE TO POSSSIBLY AS MUCH AS 800-1000J/KG. HOWEVER...WITH
DIMINISHING FORCING AND POTENTIALLY LITTLE IN THE WAY OF LAKE BREEZE
CONVERGENCE...COVERAGE OF ANY DIURNALLY DRIVEN CONVECTION WILL
PROBABLY BE QUITE LIMITED. WILL MAINTAIN JUST SCHC POPS FOR THE AFTN
HRS. MAX TEMPS SHOULD GENERALLY BE IN THE MID 80S PER FCST
SOUNDINGS. OF COURSE...SOUTHERLY WINDS WILL KEEP AREAS NEAR LAKE
MICHIGAN A LITTLE COOLER.
.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 409 PM EDT SUN AUG 18 2013
STARTING OUT ON MONDAY EVENING THE UPPER AIR PATTERN LOOKS ZONAL
WITH WEAK TROUGHING OVER THE GREAT LAKES AND A RIDGE CENTERED OVER
THE SOUTHWEST CONUS. RIDGE WILL HAVE HARD TIME AMPLIFYING FARTHER
NORTH INTO CANADA THIS WEEK THOUGH AS STRONGER WESTERLIES H5-H3
STREAM ACROSS SOUTHERN TIER OF CANADA OUT OF A MORE OR LESS
PERSISTENT TROUGH SET UP OVER GULF OF ALASKA. EVENTUALLY...WEDNESDAY
NIGHT INTO THURSDAY...LARGER SCALE HEIGHTS FALL SOME AS STRONGER
SHORTWAVE/JET MAX...PART OF WHICH IS STREAMING TOWARD WESTERN SHORE
OF BRITISH COLUMBIA TODAY...DIGS ACROSS NORTHERN ONTARIO TO WESTERN
QUEBEC. SFC COLD FRONT CROSSES UPPER LAKES WEDNESDAY AFTN INTO
WEDNESDAY NIGHT JUST AHEAD OF BETTER HEIGHT FALLS BEGIN LATE
WEDNESDAY. FRONT REPRESENTS BEST CHANCE OF SHRA/TSRA THIS WEEK. HIGH
PRESSURE BUILDS IN BEHIND THE FRONT...BUT QUESTION OF THE DAY IS FOR
HOW LONG. THIS WILL HAVE IMPACT ON FORECAST FOR FRIDAY THROUGH NEXT
WEEKEND.
INITIAL SHORTWAVE THAT ROLLS ACROSS UPPER LAKES ON MONDAY WILL
MAINLY BE EAST OF CWA MONDAY EVENING. SOUNDINGS SHOW PERHAPS MID
CLOUDS THROUGH THE NIGHT BUT WITH SUBSIDENCE IN WAKE OF WAVE...NOT
EXPECTING ANY SHRA/TSRA. ANOTHER WARM NIGHT IN THE 60S WITH STEADY
SW SFC WINDS BENEATH STRONGER WINDS AT 950-925MB. STRONGER WINDS
ALOFT FADE BY TUESDAY AFTN WHICH MAY RESULT IN LOCALIZED BACKING OF
WINDS/LAKE BREEZE ALONG LK SUPERIOR NCNTRL. LAKE MODIFICATION ONLY
ALONG LK MICHIGAN ELSEWHERE. MID CLOUDS MAY DAMPEN SUN INITIALLY...
BUT SHOULD SEE FULL SUN FOR A WHILE BTWN MID MORNING AND MID AFTN
ALLOWING TEMPS TO WARM WELL INTO THE 80S AND PROBABLY TO THE LOWER
90S IN SOME WESTERN CWA LOCATIONS. WILL HAVE TO REACH AT LEAST MID
80S BEFORE CU BEGINS TO FORM AND CONVECTIVE TEMPS ARE ON THE HIGH
SIDE IN THE LOWER 90S. SUPPOSE ALONG THE CONVERGENCE OF LAKE BREEZE
THERE COULD BE AN ISOLD STORM GIVEN MLCAPES OVER 2000J/KG. MOISTURE
THAT IS AROUND PER SOUNDINGS IS VERY SHALLOW SO WITHOUT MUCH
ADDITIONAL LARGE SCALE SUPPORT...THINK CHANCES ARE VERY MINIMAL. IF
A STORM CAN FORM...WOULD HAVE POTENTIAL FOR GUSTY WINDS AS DCAPE
VALUES ARE OVER 1000J/KG. SOUNDINGS POINT TO QUIET...WARM AND HUMID
CONDITIONS TUESDAY NIGHT IN THE WARM SECTOR. MAY SEE A TOUCH OF
FOG...THOUGH SOME WIND JUST OFF THE SFC WILL LIMIT THE EXTENT.
MOIST ONSHORE FLOW MAY LEAD TO MORE FOG CLOSER TO LK MICHIGAN SHORE.
WARM WEATHER CONTINUES ON WEDNESDAY. AFTER A WARM START NEAR 70
DEGREES IN SOME SPOTS IT WILL NOT TAKE MUCH TO SEE READINGS REACH
THOSE SIMILAR TO TUESDAY. COLD FRONT MAKES IT TO MN ARROWHEAD JUST
TO WEST OF DLH BY MIDDAY SO A LOT OF TIME FOR WARMING IN A CAPPED
AIRMASS WITH WARM NOSE AROUND 800MB. SOUNDINGS THROUGH 00Z THURSDAY
LOOK PRETTY DRY WHICH MAKES SENSE AS PRIMARY SHORTWAVE AND MOISTURE
ADVECTION IS NORTH OVR ONTARIO. SW WINDS COULD INCREASE THROUGH THE
DAY AS 950-925MB WINDS INCREASE. STILL THINK TEMPS ON WEDNESDAY MAY
END UP A BIT WARMER THAN TUESDAY WITH LATER ARRIVAL TO FRONT AND AS
H85 TEMPS ARE NEAR +20C TO START THE DAY. DOWNSLOPE MAY LEAD TO
FURTHER WARMING ALONG LK SUPERIOR FROM ONTONAGON TO MUNISING. WILL
BUMP TEMPS INTO UPR 80S ON AVERAGE AND PUSH DOWNSLOPE AREAS TO
AROUND 90. INSTABILITY OBVIOUSLY PRESENT AHEAD OF FRONT WITH THE
VERY WARM TEMPERATURES AND INCREASE IN BLYR MOISTURE /DWPNTS ARE WELL
INTO THE 60S/. RESULT IS MLCAPES 1500-2000J/KG JUST AHEAD OF THE
FRONT. THINK QUALITY OF MOISTURE ULTIMATELY WILL LIMIT CONVECTION
COVERAGE WITH THE FROPA. GIVEN THE INSTABILITY AND DEEP LAYER SHEAR
UP TO 30 KTS THERE IS AT LEAST A MARGINAL POTENTIAL FOR ISOLD SVR
STORMS THROUGH WEDNESDAY EVENING. HIGHER FREEZING LEVEL OVER 14KFT
AND DRY AIR ALOFT /DCAPE OVER 1000J/KG/ POINTS TO STRONG WIND GUSTS
AS MAIN HAZARD.
GOOD AGREEMENT THAT STRONG DRYING/SUBSIDENCE ENDS ANY SHRA/TSRA
OVERNIGHT WEDNESDAY NIGHT WITH THURSDAY STILL LOOKING MUCH COOLER
AND MAINLY DRY AS HIGH PRESSURE BUILDS ACROSS UPPER GREAT LAKES.
GUSTY NORTH TO NORTHWEST WINDS ALONG WITH COLD AIR ADVECTION SHOULD
KICK UP WINDS AND WAVES ON LK SUPERIOR LEADING TO ELEVATED SWIM
RISK. TEMPS WILL STRUGGLE TO 70 DEGREES NEAR LK SUPERIOR AND COULD
REACH LOWER 80S FAR SOUTH.
EVEN THOUGH THURSDAY IS AGREED UPON FOR COOLER AND MAINLY DRY
WEATHER THE FORECAST FOR THURSDAY NIGHT INTO FRIDAY NOT NEARLY AS
CLEAR CUT. GFS MAINTAINS CONTINUITY WITH RECENT RUNS BY SHOWING
SPRAWLING HIGH SHUNTING MAIN FRONTAL BOUNDARY AND FOCUS FOR RETURN
FLOW SHRA/TSRA OVER THE NORTHERN PLAINS AND OHIO VALLEY UNTIL AT
LEAST SATURDAY NIGHT. MEANWHILE...ECMWF UP TO 12Z RUN TODAY WAS
CONSISTENT SINCE 00Z RUN ON 17 AUG INDICATING ONLY A BRIEF HIGH
PRESSURE INTRUSION. ECMWF THEN SHOWS NEXT SHORTWAVE IN WESTERLY FLOW
FORMING A STRONGER SFC-H85 LOW OVER THE NORTHERN PLAINS THURSDAY
WITH ASSOCIATED WARM AIR ADVECTION SHRA/TSRA IMPACTING UPPER LAKES
AS EARLY AS THURSDAY NIGHT AND FRIDAY. ECMWF CERTAINLY ON THE
AMPLIFIED SIDE COMPARED TO ECMWF ENSEMBLE WHICH LOOKS MORE LIKE THE
OPERATIONAL GFS. LATEST ECMWF HAS BACKED AWAY FROM THIS IDEA THOUGH
JUST ADDING MORE UNCERTAINTY TO THIS TIME FRAME. DROPPED POPS FOR
THU NIGHT AND FRIDAY TO SLIGHT CHANCE...BUT WANTED TO KEEP SOME POPS
IN THERE IN CASE MODELS SHIFT BACK TO WETTER IDEA. MUDDLED FORECAST
CONTINUES THROUGH NEXT WEEKEND AS TIMING FOR SYSTEMS MOVING
THROUGH REST OF THE WEEKEND IS STILL OUT OF WHACK BTWN THE GFS AND
ECMWF. CONSENSUS APPROACH WORKS FOR NOW UNTIL THESE DETAILS CAN BE
BETTER SORTED OUT. AFTER THE COOLER TEMPS THURSDAY AND FRIDAY...SEEMS
THAT TEMPS WILL REACH BACK TOWARD NORMAL AND MAYBE EVEN ABOVE NORMAL
IF THERE IS NOT MUCH IN WAY OF CLOUDS OR PRECIPITATION.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 121 AM EDT MON AUG 19 2013
WITH SW FLOW OF RELATIVELY DRY AIR...EXPECT VFR CONDITIONS TO
PREVAIL THRU THIS FCST PERIOD AT KIWD/KCMX/KSAW. INCREASING SW WINDS
ABOVE NOCTURNAL INVERSION LATE TONIGHT WILL APPROACH LLWS CRITERIA.
ALSO A DISTURBANCE APPROACHING FROM THE W MAY BRING ISOLD/SCT
CONVECTION INTO CENTRAL UPPER MI LATE MON AFTERNOON. AT THIS
POINT...CONFIDENCE IS VERY LOW ON LOCATION/COVERAGE OF SHRA/TSRA.
THUS...WILL ONLY MENTION VCSH AT KSAW AROUND 21Z MON.
&&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 409 PM EDT SUN AUG 18 2013
OVERALL...EXPECT WINDS LESS THAN 20 KTS THRU THE PERIOD AS A
RELATIVELY WEAK PRES GRADIENT TYPICAL OF SUMMER PERSISTS OVER THE
GREAT LAKES REGION. SOME STRONGER SW WIND GUSTS UP TO 20-25KT MAY
OCCUR TONIGHT UNDER A SHARPER PRES GRADIENT AHEAD OF AN APPROACHING
DISTURBANCE. THE ARRIVAL OF MORE HUMID AIR FOR TUE/WED MAY RESULT IN
SOME FOG FORMATION OVER THE COOLER LAKE WATERS. HOWEVER...FOG WILL
BE MUCH MORE LIKELY TO DEVELOP IF SOME SHOWERS OCCUR OVER THE LAKE.
ANY FOG WILL DISSIPATE THU FOLLOWING A COLD FRONTAL PASSAGE AND THE
ARRIVAL OF DRIER AIR.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...ROLFSON
LONG TERM...JLA
AVIATION...VOSS
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS OMAHA/VALLEY NE
1006 PM CDT TUE AUG 20 2013
.UPDATE...
INCLUDED PRECIP MENTION IN THE FAR NORTH AND ADJUSTED CLOUDS DUE
TO CONVECTIVE DEBRIS AND TWEAKS TO DEWPOINTS AND LOW TEMPS.
&&
.DISCUSSION...
THUNDERSTORMS IN WESTERN NEBRASKA INTO SOUTH CENTRAL SOUTH DAKOTA
PROVIDING SOME CONVECTIVE DEBRIS/CLOUDS FOR PARTS OF NEBRASKA
THIS EVENING WITH A SHORTWAVE TROF. THIS SHORTWAVE IS FORECAST TO
CONTINUE TO PUSH EAST THRU 12Z. THE BULK OF THE PRECIPITATION SHOULD
REMAIN TO THE NORTH...HOWEVER THE 12Z 4KM WRF/ AND LATEST HRRR AND
00Z NAM ARE TRYING TO DEVELOP SOME SHRA/TSRA INTO NORTHEAST
NEBRASKA AND PARTS OF WESTERN IOWA...HOWEVER IT WILL HAVE A TOUGH
TIME WITH WARM MID LEVEL TEMPERATURES IN PLACE. WITH A DECENT
45KT LOW LEVEL JET AND THETA-E ADVECTION...FORECAST SOUNDINGS ARE
MOIST ABOVE H85 AND COULD SEE SOME ELEVATED SHRA/TSRA TRY TO GET
GOING. WITH LIMITED COVERAGE...ONLY MENTIONED ISOLATED POPS IN THE
FAR NORTH.
&&
.PREV DISCUSSION... /ISSUED 616 PM CDT TUE AUG 20 2013/
AVIATION...
00Z TAFS FOR KOMA...KLNK...KOFK.
VFR CONDITIONS SHOULD PERSIST THROUGH THE TAF PERIOD...WITH ANY
CLOUDS MAINLY ABOVE 10K FEET. SOUTHERLY WINDS WILL CONTINUE...
MAINLY UNDER 12 KNOTS. THE CHANCE OF TSRA WILL INCREASE AT KOFK
AFTER 00Z.
MILLER
PREV DISCUSSION... /ISSUED 331 PM CDT TUE AUG 20 2013/
DISCUSSION...
MAIN FORECAST CONCERNS IN THE NEAR TERM ARE TEMPERATURES AND
DEWPOINTS WITH FOCUS THEN TURNING TO TSTM CHANCES WED AFTERNOON
INTO THURSDAY.
LOW LEVEL WARM AIR ADVECTION IS UNDERWAY ACROSS THE FORECAST
AREA. TEMPERATURES BY MID AFTERNOON HAVE RISEN INTO THE UPPER 80S
TO LOW 90S. IN ADDITION...AN AXIS OF HIGHER DEWPOINTS INTO THE
MID 70S ARE OCCURRING OVER OUR NORTHERN CWA THIS AFTERNOON.
OTHERWISE...UPPER LEVEL HIGH PRESSURE CONTINUES TO DOMINATE A GOOD
PORTION OF THE CENTRAL U.S.
850MB TEMPS WILL BE A DEGREE OR TWO WARMER ON WEDNESDAY SO WILL
RAISE HIGHS JUST A BIT. A COLD FRONT IS PROGGED TO MOVE INTO THE
NORTHERN CWA BY WEDNESDAY AFTERNOON. A FEW STORMS COULD DEVELOP IN
THE AFTERNOON...BUT BULK SHEAR WILL BE RELATIVELY WEAK AND SOME
CONVECTIVE INHIBITION WILL NEED TO BE OVERCOME IN ORDER TO GET
ANY SEVERE STORMS. BETTER CHANCE FOR PCPN WILL BE INTO THE
EVENING HOURS AND OVERNIGHT INTO THURSDAY MORNING. ALL MODELS ARE
COMING INTO GOOD CONSENSUS...INCLUDING THE 12Z ECMWF...IN THAT
PCPN AREA WILL GENERALLY REMAIN POST FRONTAL AND MOVE SOUTH TOWARD
I-80 THROUGH EARLY THURSDAY. HAVE COOLED TEMPS IN THE NORTH FOR
WEDNESDAY BEHIND THE FRONT.
THE UPPER RIDGE AXIS WILL MOVE OVER THE CENTRAL PLAINS REGION BY
FRIDAY ALLOWING A WARM AND HUMID AIRMASS TO RETURN TO ALL OF THE
FORECAST AREA INTO THE WEEKEND.
KERN
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
ZAPOTOCNY
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
647 AM EDT MON AUG 19 2013
.SYNOPSIS...
A WARM FRONT WILL GRADUALLY BRING MORE SEASONABLE TEMPERATURES
OVER THE NEXT FEW DAYS. WEAK UPPER LEVEL DISTURBANCES WILL KEEP
THUNDERSTORMS SCATTERED THROUGH THE MIDDLE OF THE WEEK. THE LATE
WEEK PERIOD WILL TURN EVEN WARMER WITH LOWER RAIN CHANCES.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 630 AM...BASED ON CURRENT RADAR TRENDS...INCREASED RAIN
CHANCES TO CATEGORICAL VALUES NW THIS MORNING AND TO LIKELY VALUES
OVER MUCH OF THE REST OF THE AREA LATER TODAY EXPECTING A LITTLE
MORE COVERAGE THAN PREVIOUSLY THOUGHT. SYNOPSIS...TEMPERATURES AND
SKY INFORMATION IN THE PREVIOUS DISCUSSION FROM 3 AM IS STILL VALID.
THE 3 AM DISCUSSION FOLLOWS:
AS OF 3 AM MONDAY...MODEL GUIDANCE EJECTS THE UPPER LOW OVER THE
MISSISSIPPI VALLEY TO THE NORTHEAST TODAY AND TONIGHT. THE MOTION
OF THIS FEATURE WILL ALLOW LIFT ASSOCIATED WITH THE ENTRANCE REGION
OF THE UPPER JET TO AFFECT THE AREA TODAY...PARTICULARLY NW
SECTIONS. IN ADDITION MODEL GUIDANCE SHOWS WEAK ISENTROPIC LIFT
OVER THE AREA TODAY AND THE OLD FRONTAL BOUNDARY REMAINS IN THE
AREA AS WELL. FORECAST WILL HAVE HIGH CHANCE TO LIKELY POPS TODAY
WITH HIGHEST NUMBERS NW...TAPERING BACK TO SLIGHT CHANCE TONIGHT.
AFTERNOON MAXIMUM TEMPERATURES UNDER A PARTLY TO MOSTLY CLOUDY SKY
SHOULD BE LIMITED TO THE MIDDLE 80S. MINS TONIGHT SHOULD FALL TO
THE LOWER 70S...PERHAPS UPPER 60S NW.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 3 AM MONDAY...MODELS HAVE SLOWED IN SHOWING THE INLAND
PROGRESSION OF THE MID LEVEL WEST ATLANTIC RIDGE. NOW TUESDAY IS
DEPICTED AS ONE LAST DAY WHERE MOISTURE REMAINS DEEP AND A FEW WEAK
SHORTWAVES EMBEDDED IN THE 10KT 500MB FLOW PROVIDE SOME SYNOPTIC
SCALE ASCENT. TEMPERATURES WILL BE CLOSE CLIMO BUT SLIGHTLY HIGHER
THAN NORMAL POPS APPEAR TO BE WARRANTED. WEDNESDAY THE WEST ATLANTIC
RIDGE GAINS IN AMPLITUDE BACKING LOCAL FLOW ALMOST TO SOUTHERLY.
MEANWHILE THE CHANNEL OF DEEPEST MOISTURE GETS SHUNTED JUST TO OUR
WEST. ISO TO WIDELY SCATTERED CONVECTION TILL POSSIBLE ALONG
MESOSCALE BOUNDARIES AND TEMPS MAY RISE A FEW DEG ABOVE TUESDAY
COUNTERPARTS.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 3 AM MONDAY...FOR THE FIRST FEW DAYS OF THE LONG TERM THE WEST
ATLANTIC UPPER RIDGE BUILDS IN FAVOR OF THE BUILDING RIDGE OVER THE
WESTERN U.S. A WEAK SHEAR AXIS CROSSES THE REGION THURSDAY NIGHT
INTO FRIDAY. WEAK ASCENT ASSOCIATED WITH THIS FEATURES SHOULD BRING
SOME HIGHER RAIN CHANCES THAN WEDNESDAY BUT STILL PROBABLY NOT MUCH
HIGHER THAN CLIMO. THE REMAINDER OF THE PERIOD KEEPS A STRONG UPPER
RIDGE ACROSS THE MIDDLE OF THE NATION WITH TROUGHINESS ALONG BOTH
COASTLINES. BARRING THE RELATIVELY NEW IDEA OF THE GFS OF A BACKDOOR
COLD FRONT OVER THE WEEKEND THIS WILL MEAN SLIGHTLY ABOVE CLIMO
TEMPS AND SLIGHTLY LOWER THAN NORMAL THUNDERSTORM COVERAGE.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AS OF 06Z...SURFACE DEWPOINTS IN THE LOW TO MID 70S WITH CALM/LIGHT
WINDS SUGGEST THE LOW-LEVEL CONDITIONS ARE PRIMED FOR FOG/STRATUS
OVERNIGHT. MVFR CIGS/VSBYS ARE EXPECTED AT THE COASTAL TERMS...WITH
PERHAPS SOME BRIEF IFR VSBYS AT FOG-PRONE KCRE. KFLO/KLBT HAVE THE
BEST CHANCES FOR IFR...AS THE LATEST GUIDANCE FAVORS STRATUS
DEVELOPING AROUND DAYBREAK AT THE INLAND SITES. THE LATEST HRRR RUNS
SHOW SOME SHOWERS MOVING ONSHORE IN THE EARLY MORNING HOURS...SO
HAVE MENTIONED PCPN FOR THE COASTAL SITES AS WELL. CURRENT SHOWER
ACTIVITY INLAND HAS A CHANCE TO AFFECT THE INLAND TERMINALS THROUGH
ABOUT 09Z...PARTICULARLY FLO. MORE WIDELY SCATTERED SHOWERS ARE
EXPECTED WITH DAYTIME HEATING AS A COASTAL TROUGH WILL BE POSITIONED
OVER THE CAROLINAS. CIGS MAY BOUNCE AROUND BETWEEN VFR AND MVFR
DURING THE DAY...WITH MVFR MORE LIKELY DURING PERIODS OF SHRA.
SLIGHTLY HIGHER POPS INLAND ARE REFLECTED IN THE TAFS. CALM TO LIGHT
WINDS WILL BECOME S-SE AOB 10 KTS AT KMYR...KCRE AND KILM IN THE
AFTN HOURS.
EXTENDED OUTLOOK...EARLY MORNING FOG/STRATUS POSSIBLE TUESDAY AND
WEDNESDAY. ISOLATED TO SCATTERED AFTN SHOWERS/T-STORMS EXPECTED
THROUGH THE EXTENDED PERIOD.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 3 AM MONDAY...OUTSIDE OF LIGHT N TO NW WINDS EARLY TODAY DUE
TO A LAND BREEZE...EXPECT SE TO S FLOW AT 10 KT OR LESS THROUGH THE
PERIOD. SEAS ARE EXPECTED TO RUN 2 TO 3 FT.
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 3 AM MONDAY...TWIN CENTERED HIGH PRESSURE ON TUESDAY...ONE OFF
THE COAST AND THE OTHER OVER THE MOUNTAINS. RESULTING FLOW ACROSS
THE WATERS WILL BE QUITE LIGHT AND SOMEWHAT VARIABLE ALTHOUGH A
PREDOMINANTLY SOUTHERLY COMPONENT WILL BE PRESENT. THE OVER LAND
HIGH WILL BE SHRINKING ON WEDNESDAY WITH LITTLE EFFECT ON LOCAL
WINDS AND THE CONTINUED DIMINUTIVE SEAS.
LONG TERM /THURSDAY THROUGH FRIDAY/...
AS OF 3 AM MONDAY...HIGH PRESSURE OVER THE LANDMASS/EASTERN U.S.
DURING THE SHORT TERM FINALLY WASHES OUT ENOUGH TO BRING A MORE
SEASONABLE SW FLOW ON THURSDAY AROUND THE WEST ATLANTIC HIGH. THIS
FLOW CONTINUES INTO FRIDAY BUT MAY BE EQUALLY BORNE OF PIEDMONT
TROUGHINESS AS THE WEAKENING WEST ATLANTIC RIDGE.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...MBB
NEAR TERM...RAN
SHORT TERM...MBB
LONG TERM...MBB
AVIATION...BJR/31
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
326 AM EDT MON AUG 19 2013
.SYNOPSIS...
A WARM FRONT WILL GRADUALLY BRING MORE SEASONABLE TEMPERATURES
OVER THE NEXT FEW DAYS. WEAK UPPER LEVEL DISTURBANCES WILL KEEP
THUNDERSTORMS SCATTERED THROUGH THE MIDDLE OF THE WEEK. THE LATE
WEEK PERIOD WILL TURN EVEN WARMER WITH LOWER RAIN CHANCES.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 3 AM MONDAY...MODEL GUIDANCE EJECTS THE UPPER LOW OVER THE
MISSISSIPPI VALLEY TO THE NORTHEAST TODAY AND TONIGHT. THE MOTION
OF THIS FEATURE WILL ALLOW LIFT ASSOCIATED WITH THE ENTRANCE REGION
OF THE UPPER JET TO AFFECT THE AREA TODAY...PARTICULARLY NW
SECTIONS. IN ADDITION MODEL GUIDANCE SHOWS WEAK ISENTROPIC LIFT
OVER THE AREA TODAY AND THE OLD FRONTAL BOUNDARY REMAINS IN THE
AREA AS WELL. FORECAST WILL HAVE HIGH CHANCE TO LIKELY POPS TODAY
WITH HIGHEST NUMBERS NW...TAPERING BACK TO SLIGHT CHANCE TONIGHT.
AFTERNOON MAXIMUM TEMPERATURES UNDER A PARTLY TO MOSTLY CLOUDY SKY
SHOULD BE LIMITED TO THE MIDDLE 80S. MINS TONIGHT SHOULD FALL TO
THE LOWER 70S...PERHAPS UPPER 60S NW.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 3 AM MONDAY...MODELS HAVE SLOWED IN SHOWING THE INLAND
PROGRESSION OF THE MID LEVEL WEST ATLANTIC RIDGE. NOW TUESDAY IS
DEPICTED AS ONE LAST DAY WHERE MOISTURE REMAINS DEEP AND A FEW WEAK
SHORTWAVES EMBEDDED IN THE 10KT 500MB FLOW PROVIDE SOME SYNOPTIC
SCALE ASCENT. TEMPERATURES WILL BE CLOSE CLIMO BUT SLIGHTLY HIGHER
THAN NORMAL POPS APPEAR TO BE WARRANTED. WEDNESDAY THE WEST ATLANTIC
RIDGE GAINS IN AMPLITUDE BACKING LOCAL FLOW ALMOST TO SOUTHERLY.
MEANWHILE THE CHANNEL OF DEEPEST MOISTURE GETS SHUNTED JUST TO OUR
WEST. ISO TO WIDELY SCATTERED CONVECTION TILL POSSIBLE ALONG
MESOSCALE BOUNDARIES AND TEMPS MAY RISE A FEW DEG ABOVE TUESDAY
COUNTERPARTS.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 3 AM MONDAY...FOR THE FIRST FEW DAYS OF THE LONG TERM THE WEST
ATLANTIC UPPER RIDGE BUILDS IN FAVOR OF THE BUILDING RIDGE OVER THE
WESTERN U.S. A WEAK SHEAR AXIS CROSSES THE REGION THURSDAY NIGHT
INTO FRIDAY. WEAK ASCENT ASSOCIATED WITH THIS FEATURES SHOULD BRING
SOME HIGHER RAIN CHANCES THAN WEDNESDAY BUT STILL PROBABLY NOT MUCH
HIGHER THAN CLIMO. THE REMAINDER OF THE PERIOD KEEPS A STRONG UPPER
RIDGE ACROSS THE MIDDLE OF THE NATION WITH TROUGHINESS ALONG BOTH
COASTLINES. BARRING THE RELATIVELY NEW IDEA OF THE GFS OF A BACKDOOR
COLD FRONT OVER THE WEEKEND THIS WILL MEAN SLIGHTLY ABOVE CLIMO
TEMPS AND SLIGHTLY LOWER THAN NORMAL THUNDERSTORM COVERAGE.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AS OF 06Z...SURFACE DEWPOINTS IN THE LOW TO MID 70S WITH CALM/LIGHT
WINDS SUGGEST THE LOW-LEVEL CONDITIONS ARE PRIMED FOR FOG/STRATUS
OVERNIGHT. MVFR CIGS/VSBYS ARE EXPECTED AT THE COASTAL TERMS...WITH
PERHAPS SOME BRIEF IFR VSBYS AT FOG-PRONE KCRE. KFLO/KLBT HAVE THE
BEST CHANCES FOR IFR...AS THE LATEST GUIDANCE FAVORS STRATUS
DEVELOPING AROUND DAYBREAK AT THE INLAND SITES. THE LATEST HRRR RUNS
SHOW SOME SHOWERS MOVING ONSHORE IN THE EARLY MORNING HOURS...SO
HAVE MENTIONED PCPN FOR THE COASTAL SITES AS WELL. CURRENT SHOWER
ACTIVITY INLAND HAS A CHANCE TO AFFECT THE INLAND TERMINALS THROUGH
ABOUT 09Z...PARTICULARLY FLO. MORE WIDELY SCATTERED SHOWERS ARE
EXPECTED WITH DAYTIME HEATING AS A COASTAL TROUGH WILL BE POSITIONED
OVER THE CAROLINAS. CIGS MAY BOUNCE AROUND BETWEEN VFR AND MVFR
DURING THE DAY...WITH MVFR MORE LIKELY DURING PERIODS OF SHRA.
SLIGHTLY HIGHER POPS INLAND ARE REFLECTED IN THE TAFS. CALM TO LIGHT
WINDS WILL BECOME S-SE AOB 10 KTS AT KMYR...KCRE AND KILM IN THE
AFTN HOURS.
EXTENDED OUTLOOK...EARLY MORNING FOG/STRATUS POSSIBLE TUESDAY AND
WEDNESDAY. ISOLATED TO SCATTERED AFTN SHOWERS/T-STORMS EXPECTED
THROUGH THE EXTENDED PERIOD.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 3 AM MONDAY...OUTSIDE OF LIGHT N TO NW WINDS EARLY TODAY DUE
TO A LAND BREEZE...EXPECT SE TO S FLOW AT 10 KT OR LESS THROUGH THE
PERIOD. SEAS ARE EXPECTED TO RUN 2 TO 3 FT.
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 3 AM MONDAY...TWIN CENTERED HIGH PRESSURE ON TUESDAY...ONE OFF
THE COAST AND THE OTHER OVER THE MOUNTAINS. RESULTING FLOW ACROSS
THE WATERS WILL BE QUITE LIGHT AND SOMEWHAT VARIABLE ALTHOUGH A
PREDOMINANTLY SOUTHERLY COMPONENT WILL BE PRESENT. THE OVER LAND
HIGH WILL BE SHRINKING ON WEDNESDAY WITH LITTLE EFFECT ON LOCAL
WINDS AND THE CONTINUED DIMINUTIVE SEAS.
LONG TERM /THURSDAY THROUGH FRIDAY/...
AS OF 3 AM MONDAY...HIGH PRESSURE OVER THE LANDMASS/EASTERN U.S.
DURING THE SHORT TERM FINALLY WASHES OUT ENOUGH TO BRING A MORE
SEASONABLE SW FLOW ON THURSDAY AROUND THE WEST ATLANTIC HIGH. THIS
FLOW CONTINUES INTO FRIDAY BUT MAY BE EQUALLY BORNE OF PIEDMONT
TROUGHINESS AS THE WEAKENING WEST ATLANTIC RIDGE.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...MBB
NEAR TERM...RAN
SHORT TERM...MBB
LONG TERM...MBB
AVIATION...BJR/31
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
210 AM EDT MON AUG 19 2013
.SYNOPSIS...
A DECAYING FRONTAL BOUNDARY WILL SLOWLY DISSIPATE ACROSS THE AREA
AS A WESTERN ATLANTIC RIDGE BUILDS TOWARD THE COAST. TEMPERATURES
MORE TYPICAL OF AUGUST WILL RETURN MUCH OF THIS UPCOMING WEEK WITH
A FEW AFTERNOON THUNDERSTORMS.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
AS OF 1045 PM SUNDAY...LATEST SAT IMAGERY CONTINUES TO SHOW THE
MOISTURE PLUME EXTENDING ALONG AND JUST EAST OF THE SPINE OF THE
APPALACHIANS...FROM THE FLORIDA PAN HANDLE TO THE NE STATES. FLOW
AROUND THE WESTERN ATLANTIC RIDGE HAS MUSCLED ITS WAY ACROSS THE
COASTAL CAROLINAS...AND THUS PREVENTING THIS MOISTURE PLUME FROM
ENCOMPASSING THE ENTIRE CWA TONIGHT INTO MONDAY. LATEST SREF
INDICATES A LOW PROBABILITY FOR MEASURE-ABLE RAIN TONIGHT...AND
HIGHLIGHTS 2 LOCATIONS...THE WESTERN FRINGES OF THE FA...AND
ACROSS THE IMMEDIATE COAST FROM ANY ONSHORE MOVEMENT OF PCPN. LOOK
FOR A RANGE OF 15 TO 40 POPS ACROSS THE FA OVERNIGHT. EARLIER
INCREASE TO THE MIN TEMPS TONIGHTS REMAINS ON TARGET...NO
ADDITIONAL TWEAKING NEEDED. WITH ONSHORE FLOW ACROSS 80+ DEGREE
SSTS...MIN TEMPS ALONG THE IMMEDIATE BEACHES MAY STAY IN THE UPPER
70S TO AROUND 80.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
AS OF 3 PM SUNDAY...PRIMARY WEATHER STORY MONDAY AND TUESDAY WILL
BE THE RETURN OF MORE TYPICAL AUGUST WEATHER ACROSS THE FORECAST
AREA...AS REMNANTS OF AN UNSEASONABLE FRONTAL BOUNDARY THAT
BROUGHT MINIMUM TEMPERATURES WELL INTO THE 60S AND HEARTY RAINFALL
AMOUNTS RECENTLY...LOSES IDENTITY AND DISSIPATES OVER THE AREA.
AN UPPER TROUGH PRESENTLY OVER THE MISSISSIPPI VALLEY WILL LIFT
NE AND DAMPEN ACROSS NEW ENGLAND BY MONDAY NIGHT. THIS WILL ALLOW
THE WESTERN EXTENT OF A STACKED BERMUDA RIDGE TO POKE LANDWARD
ACROSS THE SE US COAST MONDAY AND TUESDAY. LINGERING LOW AND MID
LEVEL MOISTURE ON MONDAY COUPLED WITH A WEAK COASTAL TROUGH MOVING
INLAND SHOULD TRIGGER SCATTERED SHOWERS AND ISOLATED TSTMS DURING
THE DAY ON MONDAY. BY TUESDAY HOWEVER...THE EFFECTS OF THE BERMUDA
RIDGE PROGRESSING INLAND...WILL BE SEEN BY DRYING IN THE MIDDLE
LEVELS OF THE ATMOSPHERE. WHILE WE CANNOT RULE OUT SHOWERS ON
TUESDAY...COVERAGE SHOULD BE SUBSTANTIALLY HINDERED BY SUBSIDENT
DRYING ALOFT.
WE MAY SEE LOW CLOUDS EARLY MONDAY AS WELL AS CONVECTIVE DEBRIS
CLOUDS DURING THE DAY...SO FOR MAXIMUMS AM EXPECTING MIDDLE AND
UPPER 80S ACROSS THE REGION. EFFECTS OF THE RIDGE TUESDAY SHOULD
ALLOW UPPER 80S MOST LOCATIONS WITH A FEW 90S ACROSS THE INTERIOR.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 3 PM SUNDAY...THE 500 MB UPPER LEVEL RIDGE AXIS IS STILL
TRYING TO TO BUILD WESTWARD AND WILL BE ALIGNED ALONG A LINE FROM
MOBILE TO SAVANNAH ON THURSDAY. THE 12 UTC CYCLE OF THE GFS DEVELOPS
A SECOND CUTOFF LOW SOUTH OF LAKE MICHIGAN ON WEDNESDAY AND LIFTS
THIS FEATURE WELL NORTH OF THE AREA BY LATE THURSDAY. ALOFT A TROUGH
IS CENTERED ALONG THE COAST AND NORTHWEST FLOW ALOFT WILL BE
ESTABLISHED. THE GFS IS SHOWING AN UPPER LEVEL DISTURBANCE SHIFTING
INTO THE CAROLINA BY THE END OF THE WEEK.
AT THE SURFACE THE FRONTAL BOUNDARY WILL REMAIN AND THE MODELS
CONTINUE TO SHOW A WEAKNESS IN THE SURFACE PRESSURE PATTERN THROUGH
FRIDAY. PRECIPITABLE WATERS WILL REMAIN HIGH AND THE ONLY UPPER
LEVEL SUPPORT MAY BE FROM SHORTWAVE IN THE NORTHWEST FLOW BY FRIDAY.
THE UNCERTAINTY IS HOW MUCH IMPACT THESE DISTURBANCES WILL HAVE ON
THE COAST. SO WITH THE CONFIDENCE NOT HIGH WENT WITH A CHANCE OF
DIURNAL CONVECTION EACH DAY AND ONLY A SLIGHT CHANCE OVERNIGHT.
MAXIMUM TEMPERATURES ARE EXPECTED TO BE NEAR 90 EACH DAY AND LOWS
IN THE LOWER 70S INLAND AND MID 70S AT THE BEACHES.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AS OF 06Z...SURFACE DEWPOINTS IN THE LOW TO MID 70S WITH CALM/LIGHT
WINDS SUGGEST THE LOW-LEVEL CONDITIONS ARE PRIMED FOR FOG/STRATUS
OVERNIGHT. MVFR CIGS/VSBYS ARE EXPECTED AT THE COASTAL TERMS...WITH
PERHAPS SOME BRIEF IFR VSBYS AT FOG-PRONE KCRE. KFLO/KLBT HAVE THE
BEST CHANCES FOR IFR...AS THE LATEST GUIDANCE FAVORS STRATUS
DEVELOPING AROUND DAYBREAK AT THE INLAND SITES. THE LATEST HRRR RUNS
SHOW SOME SHOWERS MOVING ONSHORE IN THE EARLY MORNING HOURS...SO
HAVE MENTIONED PCPN FOR THE COASTAL SITES AS WELL. CURRENT SHOWER
ACTIVITY INLAND HAS A CHANCE TO AFFECT THE INLAND TERMINALS THROUGH
ABOUT 09Z...PARTICULARLY FLO. MORE WIDELY SCATTERED SHOWERS ARE
EXPECTED WITH DAYTIME HEATING AS A COASTAL TROUGH WILL BE POSITIONED
OVER THE CAROLINAS. CIGS MAY BOUNCE AROUND BETWEEN VFR AND MVFR
DURING THE DAY...WITH MVFR MORE LIKELY DURING PERIODS OF SHRA.
SLIGHTLY HIGHER POPS INLAND ARE REFLECTED IN THE TAFS. CALM TO LIGHT
WINDS WILL BECOME S-SE AOB 10 KTS AT KMYR...KCRE AND KILM IN THE
AFTN HOURS.
EXTENDED OUTLOOK...EARLY MORNING FOG/STRATUS POSSIBLE TUESDAY AND
WEDNESDAY. ISOLATED TO SCATTERED AFTN SHOWERS/T-STORMS EXPECTED
THROUGH THE EXTENDED PERIOD.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 1045 PM SUNDAY...THE INVERTED SFC TROF OR COASTAL FRONTAL
BOUNDARY...REMAINS STATIONARY ALONG THE IMMEDIATE COAST OF THE
CAROLINAS FROM CAPE HATTERAS SOUTHWARD. OVERALL...MODELS INDICATE
THE SFC PRESSURE PATTERN WILL YIELD AN E-SE WIND OVERNIGHT. THE
NEAR-SHORE WATERS...SAY WITHIN 5 NM FROM THE COAST...MAY OBSERVE
A NE WIND DIRECTION DURING THE MON PRE-DAWN HOURS. A RATHER
RELAXED SFC PG WILL YIELD 10 KT OR LESS FOR SPEEDS. SIGNIFICANT
SEAS GENERALLY AROUND 2 FT...EXCEPTION...ACROSS THE ILM SC WATERS
WHERE AN ESE GROUNDSWELL..ALBEIT SMALL AND AT 9-10 SECOND
PERIODS...COULD PUSH SIGNIFICANT SEAS UP TO 3 FEET. THIS GROUND
SWELL IS COMPLEMENTS OF THE SOUTHERN PERIPHERY FETCH OF THE WESTERN
ATLANTIC HIGH.
SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 3 PM SUNDAY...MARINE REGIME MONDAY AND TUESDAY WILL SEE THE SW
PORTION OF AN EXPANDING BERMUDA HIGH PRESSURE CELL MOVING ONTO THE
COAST...WHILE A WEAK SURFACE COASTAL TROUGH PUSHES INLAND. THIS
SHOULD IMPART A LIGHT S-SE WIND FLOW ACROSS THE 0-20NM WATERS. SEAS
2-3 FEET MOST AREAS...COMPOSED PRIMARILY OF SE WAVES EVERY 8-10
SECONDS WITH A LIGHT SOUTHERLY CHOP. WE MAY SEE A FEW SHOWERS AND
TSTMS OVER THE WATERS EARLY MONDAY AS CONVERGENCE INCREASES IN
RESPONSE TO THE COASTAL TROUGH ALONG THE COAST. NOT A BAD IDEA
A GET A RADAR FIX MONDAY MORNING BEFORE HEADING OUT.
LONG TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 3 PM SUNDAY...THE FRONTAL BOUNDARY ALONG THE COAST CONTINUES
THROUGH THE FIRST PART OF THIS FORECAST PERIOD. WITH A VERY WEAK
PRESSURE GRADIENT EXPECTED WINDS WILL BE BE LESS THAN 10 KNOTS AND
VARIABLE THROUGH THURSDAY MORNING. THE LOCAL WAVE MODEL COUPLED
WITH THE WAVEWATCH III MODEL IS SHOWING SEAS AROUND 2 FEET THROUGH
THURSDAY MORNING AND A SLIGHT INCREASE IN SEAS TO 2 TO 3 FEET BY
LATE THURSDAY INTO FRIDAY AS A MORE SOUTH TO SOUTHWEST FLOW OF 10
KNOTS BECOMES ESTABLISHED.
&&
.TIDES/COASTAL FLOODING...
AS OF 1045 PM SUNDAY...THE TIDE GAGE ALONG THE CAPE FEAR RIVER
PEAKED AT 5.74 FT MLLW AT HIGH TIDE THIS EVENING...ABOVE THE 5.50
FT MLLW MINOR COASTAL FLOODING THRESHOLD. THE GAGE READING IS NOW
BELOW 5 FT MLLW AND CONTINUING TO DECLINE. WILL HAVE ANOTHER RUN
AT BREACHING MINOR COASTAL FLOODING THRESHOLDS DURING MONDAY
EVENINGS HIGH TIDE...WHICH MAY REQUIRE ANOTHER COASTAL HAZARD
MESSAGE.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...MJC
NEAR TERM...DCH
SHORT TERM...MJC
LONG TERM...DRH
AVIATION...BJR/31
TIDES/COASTAL FLOODING...DCH
AREA FORECAST DISCUSSION
NWS WILMINGTON OH
159 AM EDT MON AUG 19 2013
.SYNOPSIS...
SEVERAL WEAK WEATHER SYSTEMS WILL DRIFT SLOWLY THROUGH THE GREAT
LAKES FROM TONIGHT THROUGH MID-WEEK...AS TEMPERATURES AND
HUMIDITY CONTINUE TO SLOWLY INCREASE AT THE SAME TIME. NEITHER OF
THE DISTURBANCES IS EXPECTED TO BRING MUCH COVERAGE OF RAIN...BUT
THREATS FOR SHOWERS OR A FEW THUNDERSTORMS ON A LIMITED BASIS WILL
BE PRESENT TONIGHT INTO MONDAY MAINLY EAST OF I-71...AND ON
WEDNESDAY ESPECIALLY SOUTH OF I-70. IN BOTH CASES...MOST AREAS
WILL STAY DRY...WITH MUGGY AND WARM AFTERNOONS AND MILD NIGHTS WITH
LIGHT WINDS. ABOVE NORMAL TEMPERATURES WILL REMAIN ENTRENCHED
THROUGH THE WEEK INTO NEXT WEEKEND...AS A VERY TYPICAL LATE SUMMER
PATTERN REMAINS IN PLACE.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
UPDATED TONIGHT TO REMOVE ALL PRECIPITATION FOR THE OVERNIGHT
HOURS. WITH LOSS OF HEATING OF THE DAY AND WEAK FORCING
REMAINING...THERE IS ONLY SMALL CHANCE OF SHOWERS. ALSO ADJUSTED
SKY COVER FOR CURRENT TRENDS. NO OTHER SIGNIFICANT CHANGES WERE
MADE WITH THIS UPDATE.
AFTERNOON DISCUSSION FOLLOWS BELOW....
DISORGANIZED SHIELD OF VERY LIGHT
RAIN/SPRINKLES HAS BEEN PUSHING STEADILY NORTHEAST THROUGH THE
AFTERNOON UP THE SCIOTO RIVER VALLEY...IMMEDIATELY IN ADVANCE OF A
MID-LEVEL VORTICITY MAX SEEN SWIRLING BOTH ON VISIBLE SATELLITE
IMAGERY AND ON RADAR MOSAICS OVER NRN KENTUCKY. THIS IS NEAR THE
NOSE OF A NARROW 250MB JETLET /115KT/ THAT IS SHIFTING NORTHEAST
AND ALLOWING THE OPENING/SHEARING OF THE OLD CLOSED LOW THAT HAD
BEEN SPINNING WELL SOUTHWEST OF THE AREA THE PAST FEW DAYS. THE
MID/UPPER LEVEL SHORTWAVE TROUGH IS POSITIVELY TILTED...AND
WEAKENING WITH TIME...WITH DECREASING LARGE SCALE ASCENT AND VERY
WEAK SURFACE FEATURES UNDERNEATH. THE 18.18Z RAP HAD A NICE HANDLE
ON THE MID LEVEL VORT MAX DRIVING NORTHEAST THROUGH SCNTL OH...AND
CONTINUES TO LIFT THIS FEATURE OUT OF THE AREA THROUGH MID
EVENING...WITH THE SHIELD OF LIGHT RAIN/SPRINKLES LIKELY EXITING
THE AREA BY 00Z OR SO...IF IT DOESN/T FALL APART COMPLETELY BEFORE
THEN. MESOANALYSIS CURRENTLY /19Z/ SHOWS A FAIRLY NICE
DIFFERENTIAL HEATING ZONE /CAPE AXIS/ ON THE IMMEDIATE WEST SIDE
OF THE RAIN SHIELD...RUNNING FROM OWEN/GRANT COUNTIES UP THROUGH
THE WILMINGTON AREA TOWARDS CMH. VARIOUS AND SUNDRY CONVECTION
ALLOWING MODEL RUNS /3-4KM RESOLUTION/ HAVE TRIED TO DEVELOP
ISOLATED STORMS IN THIS CORRIDOR IN THE NEXT FEW HOURS UP THROUGH
ABOUT 02Z...SO WE ARE IN NO HURRY TO DECREASE/SHRINK RAIN CHANCES
WEST OR SOUTHWEST OF CURRENT RAIN SHIELD OVER SCNTL OH. WHILE
MLCAPE IS LARGELY WEAK /300-700 J/KG/...THE PASSING OF THE
MID/UPPER LEVEL PV ANOMALY ACROSS THIS AREA THROUGH THE NEXT FEW
HOURS MAY AGITATE THE WEAK BAROCLINIC ZONE FOR A STORM OR TWO.
LATER THIS EVENING/OVERNIGHT...ONE MORE SURGE /IF YOU CAN CALL IT
THAT - IT IS QUITE WEAK/ OF MOISTURE ADVECTION RIDES FROM ERN
TN/KY INTO CNTL/ERN OH AND MAY PROMOTE SOME -SHRA REGENERATION
OVER THE SCIOTO VALLEY AND UP TOWARD/EAST OF CMH...SO WE HOLD ON
TO HIGHER RAIN CHANCES HERE LATER THIS EVENING AND OVERNIGHT. NOT
SURE IF THIS WILL LEAD TO MUCH ACTIVITY OR NOT...CONFIDENCE IS
LOW...BUT THE SIGNAL HAS BEEN PRESENT FOR A FEW DAYS THUS DON/T
WANT TO BACK AWAY YET. KEPT MIN TEMP FORECAST RIGHT WHERE IT WAS
FOR THE MOST PART...WELL TRENDED IN THE LOWER 60S MOST
AREAS...THOUGH MIXED OUT DEW POINTS IN WCNTL OHIO/ERN IND SUGGEST
SOME MID TO UPPER 50S IN THAT AREA WHERE PRECIPITABLE WATER
MINIMUM EXISTS.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
THE LAST WEAK SURGE OF MOISTURE MAY LINGER SHOWER CHANCES IN THE
EAST IN THE MORNING...AND THERE MAY BE JUST ENOUGH DIURNAL INSTBY
FOR A SHOWER/STORM IN THE FAR EAST/SOUTH IN THE AFTERNOON...BUT
MONDAY IS LARGELY A DRY DAY FOR THE FORECAST AREA WITH INCREASING
SUBSIDENCE IN THE WAKE OF THE DEPARTING SHORTWAVE TROUGH WHICH
WILL BE SHEARING DOWNSTREAM THROUGH PA/NY. DESPITE ITS
DEPARTURE...THERE REMAINS A WEAKNESS IN THE LARGER SCALE HEIGHT
FIELD BETWEEN TWO LARGE ANTICYCLONES OFF THE SOUTHEAST CONUS AND
OVER THE CNTL CONUS. THIS WEAKNESS IS A SOURCE OF LINGERING WEAK
SHORTWAVE ENERGY...AND WITH THIS AXIS LINGERING IN THE FAR
SOUTH/EAST...THUS THE SMALL RAIN CHANCES LINGERING UNTIL THAT AXIS
CAN CLEAR IN THE MID AFTERNOON HOURS. MOST AREAS WILL SEE A FAIR
AMOUNT OF SUNSHINE ON MONDAY...WITH TEMPS ADDING A FEW MORE
DEGREES TO PUT MOST AREAS IN THE LOW-MID 80S.
BRIEF SHORTWAVE RIDGING SLIDES IN FOR MONDAY NIGHT...WITH SKIES
GOING CLEAR. THIS SHOULD ALLOW A LITTLE BETTER TEMP DROP WITH
PWAT DROPPING OFF BACK TOWARD 1 INCH /BELOW SEASONAL NORMS/.
THUS...SIDED WITH SOME OF THE MOS DATASETS THAT ALLOWED COOL SPOTS
TO DROP OFF PRETTY DECENTLY MON NIGHT INTO THE UPPER 50S. WITH
SUCH LIGHT WINDS OVER THE NEXT COUPLE NIGHTS...ALMOST CERTAIN TO
BE COMMON SUMMER NIGHT FOG IN LOW LYING AREAS...BUT NOT SEEING A
GREAT SIGNAL FOR SOMETHING WIDESPREAD TO INCLUDE IN THE FORECAST
AS OF YET.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
SURFACE HIGH PRESSURE WILL ESTABLISH ITSELF TO OUR SE ON TUESDAY IN
WAKE OF DEPARTING UPR LVL SYSTEM. WE SHOULD SEE A MOSTLY SUNNY TO
PARTLY SUNNY DAY. MODELS HAD BEEN SUGGESTING THAT PERHAPS A POP OF
SHOWER OR STORM COULD OCCUR IN THE FAR SOUTH DURING THE HEAT OF THE
DAY. THIS STILL MAY OCCUR...BUT DO NOT FEEL IT WARRANTS A 20 POP
MENTION SO HAVE ALLOW THE FORECAST TO REMAIN DRY. HIGHS WILL BE A
LITTLE WARMER...GENERALLY IN THE MID 80S.
FOR THE PERIOD TUESDAY NIGHT INTO WEDNESDAY NIGHT...MAJORITY OF
MODELS HAVE COME MORE IN LINE ON WHAT WILL HAPPEN TO EMBEDDED S/WV
ENERGY WITHIN THE NW FLOW ALOFT. IT APPEARS THIS ENERGY WILL DEVELOP
INTO A CLOSED LOW TO OUR WEST...THEN WILL SLOWLY PROGRESS EAST THROUGH
THE REGION WEDNESDAY INTO WEDNESDAY NIGHT. ECMWF/GFS SUGGEST THAT
SOME EMBEDDED S/WV ENERGY MOVING NE AROUND DEVELOPING CLOSED LOW
COULD SPARK A FEW SHOWERS AND THUNDERSTORMS BEGINNING ACRS OUR SW
TUESDAY NIGHT. HAVE GIVEN ALL LOCATIONS AT LEAST A THREAT FOR
SHOWERS AND STORMS ON WEDNESDAY WITH THE HIGHER CHANCES FAVORING THE
SRN ZONES DUE TO HIGHER INSTABILITY AND MOISTURE. HAVE ALLOWED POPS
TO FALL OFF OVERNIGHT WEDNESDAY NIGHT AS SYSTEM HEADS EAST. HIGHS ON
WEDNESDAY WILL BE SLIGHTLY COOLER...ESPECIALLY SOUTHWEST CLOSER TO
THE UPR LVL LOW.
FOR THE PERIOD THURSDAY INTO FRIDAY NIGHT...MODELS CONTINUE TO
STRUGGLE ON HOW LONG WAVE TROUGH ENERGY WILL DIG SE INTO SE CANADA
AND NEW ENGLAND DURING THE PERIOD. AS SUCH...ASSOCIATED COLD FRONT
AND WHERE IT WILL END UP...I.E. WILL IT PUSH THROUGH...STALL OUT
OVER OUR AREA...OR PERHAPS FALL APART...IS STILL IN QUESTION. HAVE
TAKEN A BLEND OF WPC AND THE LATEST 18.12Z ECMWF...WHICH ALLOWS THE
FRONT TO APPROACH THE REGION FROM THE NORTH THURSDAY NIGHT...SLOW IT
UP AS IT PUSHES INTO THE REMAINDER OF THE AREA ON FRIDAY...THEN
WASHES IT OUT FRIDAY NIGHT INTO SATURDAY AS ANOTHER HIGH PRESSURE
RIDGE BUILDS IN FROM THE NORTH. GIVEN LACK OF STRONG UPR
SUPPORT...AS IT IS FCST TO REMAIN WELL OFF TO THE NE...ALONG WITH
WEAK LOW LEVEL FORCING...HAVE KEPT POPS LOW THURSDAY NIGHT INTO
FRIDAY. HAVE THEN ALLOWED CONDITIONS TO DRY OUT BY FRIDAY NIGHT.
TEMPERATURES WILL BE CLOUD DEPENDENT BUT SHOULD SEE A SLIGHT BUMP UP
AHEAD OF THE FRONT ON THURSDAY WITH SIMILAR OR SLIGHTLY COOLER
CONDITIONS POSSIBLE ON FRIDAY.
SURFACE HIGH PRESSURE WILL MOVE EAST THROUGH THE UPCOMING WEEKEND AS
A MID LVL RIDGE BEGINS TO NUDGE INTO FROM THE CNTRL PLAINS.
CONDITIONS SHOULD REMAIN DRY. TEMPERATURES WILL BE SEASONABLY WARM
FOR LATE AUGUST.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
FOG AND IN SOME INSTANCES LOW CIGS HAVE DEVELOPED ACROSS THE AREA
AND WILL CONTINUE THROUGH THE OVERNIGHT HOURS. EXPECT VSBYS TO
FLUCTUATE THROUGH THE NIGHT HOWEVER CONDITIONS WILL IMPROVE
SHORTLY AFTER SUNRISE. WINDS WILL BE LESS THAN 10 KNOTS THROUGH
THE TAF PERIOD. ADDITIONAL FOG WILL BE POSSIBLE MONDAY NIGHT AS
WELL.
OUTLOOK...FOG WILL BE POSSIBLE MONDAY NIGHT. THUNDERSTORMS ARE
POSSIBLE ON WEDNESDAY.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.
&&
$$
SYNOPSIS...BINAU
NEAR TERM...BINAU/PARKER
SHORT TERM...BINAU
LONG TERM...HICKMAN
AVIATION...NOVAK
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
156 AM EDT MON AUG 19 2013
.SYNOPSIS...
A WEAK DISTURBANCE WILL PASS ACROSS PA TODAY...BRINGING CLOUDS
AND SOME RAIN. HIGH PRESSURE CENTERED NEAR BERMUDA WILL CONTROL
THE WEATHER ACROSS PA DURING MIDWEEK...DELIVERING WARMER AND MORE
HUMID CONDITIONS BEFORE A COLD FRONT ARRIVES AROUND FRIDAY.
&&
.NEAR TERM /UNTIL 8 AM THIS MORNING/...
UPPER LVL TROUGH LIFTING NE THRU THE OHIO VALLEY THIS AM. LG SCALE
FORCING AHEAD OF THIS FEATURE IS RESULTING IN A FEW -SHRA ACROSS
WESTERN PA AS OF 05Z AND EXPECT SCT -SHRA TO MOVE INTO THE
ALLEGHENIES AND CENTRAL MTNS BY 12Z. CLOUD COVER AND INCREASING
LOW LVL MOISTURE SHOULD KEEP TEMPS FROM FALLING MUCH FROM 05Z
READINGS WITH LOWS IN THE M-U50S.
&&
.SHORT TERM /8 AM THIS MORNING THROUGH 6 PM TUESDAY/...
SLOW MOVING UPPER TROF WILL TAP 1.5" PW FOR MORE WIDESPREAD CHC
OF SHOWERS AND TSTORMS ACROSS MOST AREAS ON MONDAY. PASSAGE OF
UPPER TROF AXIS WILL BRING A DECREASING CHC OF SHOWERS ACROSS THE
WESTERN COUNTIES DURING MID TO LATE AFTN. A GOOD DEAL OF CLOUD
COVER SHOULD LIMIT CAPES...SO SEVERE WEATHER IS NOT EXPECTED.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
INTERESTING LOW OFF NORFOLK VA THIS AFT...STARTING TO PULL AREA
OF SHOWERS EAST OF THE AREA THIS AFT...BUT MORE SHOWERS ACROSS
THE OH VLY WITH THE UPPER LVL LOW.
EXPECT SHOWERS TO LINGER INTO MONDAY...BEFORE CONDITIONS IMPROVE
LATE. AFTER THIS...MAINLY DRY EXPECT FOR LATER THU INTO FRIDAY...
WHEN A COLD FRONT MOVES ACROSS PA. SOME RISK OF SHOWERS ON WED
ACROSS THE SE LIKE TODAY...BUT LEFT OUT FOR NOW. OVERALL A
COMPLEX PATTERN...WITH THE TENDENCY FOR MORE STABLE AND LESS
HUMID AIR TO TRY TO BUILD SOUTHWARD EAST OF THE MOUNTAINS...
GIVEN HIGH OVER EASTERN CANADA AND NEW ENGLAND THIS WEEK. AT
THE SAME TIME...WARMER AND MORE HUMID AIR WORKS NORTHWARD
WEST OF THE MOUNTAINS. FOR NOW...LEFT MAX TEMPS CLOSE TO WHAT
WAS IN THE GRIDS. REAL STRONG WARM ADVECTION WITH STRONG
WESTERLY FLOW WILL BE WELL NORTH OF THE US...CANADIAN BORDER
FROM LATE TUE INTO EARLY THU.
MAIN CHANGE WAS TO UP MIN TEMPS MONDAY NIGHT AND TUE NIGHT...GIVEN
GUIDANCE AND OTHER OFFICES.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
VERY SUBTLE FEATURES DRIVING THE FORECAST FOR THE NEXT 24
HOURS...AND THEREFORE FORECAST IS OF SOMEWHAT LOWER CONFIDENCE.
VERY LITTLE PRECIPITATION REMAINS ON RADAR...AS WESTERN PA
ACTIVITY HAS DWINDLED TO JUST A FEW SCATTERED SHOWERS. SHORT RANGE
MODELS CONTINUE TO SUPPORT THE IDEA OF SHOWERS REDEVELOPING
OVERNIGHT ACROSS THE WEST...AND SPREADING INTO CENTRAL PA BY
MORNING. RUC ALSO CONTINUES THE THINKING OF DEVELOPING SCATTERED
CONVECTION ACROSS CENTRAL AREAS TOMORROW AFTERNOON...PROPAGATING
TO THE SOUTH AND EAST.
HOWEVER...BASED ON RADAR TRENDS...HAVE CUT BACK ON PRECIPITATION
IN MOST TAFS OVERNIGHT. FOG AND LOWER STRATUS FORECAST BY MODELS
ALSO SLOWER THAN EXPECTED IN PREVIOUS FORECAST...WITH ALL
LOCATIONS AT 03Z STILL VFR. WILL CONTINUE THE THINKING ALONG THE
LINES OF LOWER CLOUDS AND FOG FORMATION...BUT HAVE BACKED OFF A
BIT ON LOWER LIMITS OF RESTRICTIONS.
UPPER TROF AXIS LIFTS NORTHEAST MONDAY. RESULT WILL BE SLIGHT
SURFACE RIDGING DEVELOPING DURING THE DAY AND A SUBTLE/GRADUAL
WIND SHIFT TO THE WEST DURING THE AFTERNOON. HOWEVER...REMNANTS OF
UPPER TROF MOVING THROUGH THE REGION COULD DEVELOP SOME CONVECTION.
WITHOUT A REAL PUSH OF DRIER AIR...EXPECT MORE FOG FORMATION
MONDAY NIGHT INTO TUESDAY...BEFORE A RETURN TO VFR BY MID WEEK.
OUTLOOK...
MON...AM MVFR/IFR...WITH IMPROVEMENTS DURING THE AFTERNOON MOST
LOCATIONS. ADDITIONALLY...SCATTERED SHOWERS AND ISOLATED TSRA.
TUE...AM FOG POSS. THEN MAINLY VFR.
WED-THU...VFR.
FRI...MVFR WITH SCT SHRA/TSRA.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...DEVOIR
NEAR TERM...FITZGERALD
SHORT TERM...DEVOIR/FITZGERALD
LONG TERM...MARTIN
AVIATION...JUNG
AREA FORECAST DISCUSSION...UPDATED
NWS MILWAUKEE/SULLIVAN WI
1051 PM CDT TUE AUG 20 2013
.UPDATE...
NARROW BAND OF SHOWERS FROM PORTAGE COUNTY INTO ADAMS COUNTY IN
REGION OF INCREASING 850 MB MOISTURE BEING ADVECTED IN ON POCKET
OF 30 KNOT 850 MB WINDS. BEST 850 MB CONVERGENCE LOOKS TO REMAIN
NORTH OF CWA...BUT NRN-MOST COUNTIES COULD BE CLIPPED BY THIS
BAND. HRRR HINTING AT MORE SCATTERED WARM ADVECTION SHOWERS
DEVELOPING AFTER MIDNIGHT IN S CENTRAL WISCONSIN ALONG MOIST AXIS
AND MOVING INTO SOUTHEAST WISCONSIN DURING THE MORNING. 21/00Z NAM
IN AGREEMENT WITH EARLIER GFS/ECMWF RUNS SHOWING BEST CHANCES FOR
SHOWERS/STORMS TO BE WEDNESDAY EVENING...THOUGH AREAS NW OF
MADISON COULD SEE PCPN BY LATE IN THE AFTERNOON.
&&
.AVIATION/06Z TAFS/...
WILL KEEP AN EYE ON FOG DEVELOPMENT ELSEWHERE PRIOR TO ISSUANCE
TIME...BUT APPEARS KENW AND THE WISCONSIN RIVER VALLEY WILL BE
THE MOST LIKELY TO SEE MVFR VSBYS IN FOG AGAIN OVERNIGHT. INITIAL
WARM AIR ADVECTION SHOWERS WILL REMAIN NORTH OF TAF SITES
OVERNIGHT...THOUGH A FEW OF THE HI-RES/RAPID UPDATE MODELS
HINTING AT MORE SCATTERED WARM ADVECTION SHOWERS DEVELOPING AFTER
MIDNIGHT IN SOUTH CENTRAL WISCONSIN ALONG MOIST AXIS AND MOVING
INTO SOUTHEAST WISCONSIN DURING THE MORNING...WITH THE LATEST GFS
JOINING THE PRIOR RUN OF THE ECMWF IN BRINGING PCPN ACROSS MOST OF
THE FORECAST AREA PRIOR TO 18Z. WILL LEAVE WEDNESDAY MORNING DRY
FOR NOW AND FOCUS BEST THUNDERSTORM CHANCES WITH THE FRONTAL
PASSAGE LATE WEDNESDAY AFTERNOON/EVENING...POSSIBLY LINGERING AT
EASTERN TAF SITES INTO THE OVERNIGHT HOURS. EXPECT MVFR CONDITIONS
WITH THE SHOWERS AND STORMS...WITH SOME BRIEF IFR VSBYS IN THE
HEAVIER STORMS.
&&
.PREV DISCUSSION... /ISSUED 348 PM CDT TUE AUG 20 2013/
TONIGHT AND WEDNESDAY...FORECAST CONFIDENCE IS HIGH.
EXPECTING LOW TEMPS IN THE UPPER 60S WITH A MODERATE TO WEAK
INVERSION AND A BIT OF CLOUD COVER. KEPT THE PATCHY FOG IN RIVER
VALLEYS AND LOW LYING AREAS...BUT OTHERWISE THE LAYER JUST ABOVE
THE SURFACE LOOKS TOO DRY FOR FOG.
WEDNESDAY/S HIGH TEMPERATURES WERE THE MAIN FORECAST QUESTION FOR
THIS PERIOD. ECMWF 925 MB TEMPS AT 00Z ON THURSDAY ARE AROUND 25 TO
27 C. THIS WOULD YIELD 89 TO 93 F HIGHS WITH DRY ADIABATIC LAPSE
RATES...BUT MOST MODEL MAX TEMP FORECASTS ARE NOT THAT WARM. MID TO
UPPER LEVEL CLOUDS COULD KEEP TEMPERATURES IN CHECK...BUT RIGHT NOW
IT LOOKS LIKE THEY WILL STAY MAINLY TO OUR NORTHWEST UNTIL LATER IN
THE DAY...BASED ON 500 MB RH. EXPECTING CLOUD COVER TO BE SIMILAR TO
TODAY...JUST INCREASING AS THE PRECIP APPROACHES. ALSO...A NUMBER OF
SITES TODAY REACHED THE UPPER 80S AND JANESVILLE HAS EVEN HIT 90.
WITH SIMILAR CONDITIONS...BUT ADDITIONAL WAA...WOULD EXPECT SITES TO
BE AT LEAST A FEW DEGREES WARMER THAN TODAY.
WEDNESDAY NIGHT AND THURSDAY...FORECAST CONFIDENCE IS MEDIUM.
THE MODELS HAVE COME INTO BETTER AGREEMENT NOW WITH THE SPEED OF
THE FRONT. THE ECMWF HAS PICKED UP A LITTLE SPEED AND LOOKS
SIMILAR TO THE NAM/GFS NOW. FRONTAL PASSAGE...FROPA...SHOULD BE
AROUND MIDNIGHT FOR OUR NORTHWEST FORECAST AREA...MARQUETTE...GREEN
LAKE AND SAUK COUNTIES...AND RIGHT AROUND 6 AM THURSDAY FOR THE
KENOSHA AREA. SHOWERS AND STORMS SHOULD BE ONGOING ALONG AND AHEAD
OF THE FRONT BEFORE IT ARRIVES. HOWEVER...GIVEN THE LATER
ARRIVAL...THERE MAY NOT BE ENOUGH CAPE AND TOO MUCH CIN DEVELOPING
TO SUPPORT SEVERE THUNDERSTORMS. THE DEEP FORCING WILL BE LIMITED
AS THE MAIN MID LEVEL SHORT WAVE JUST BRINGS US A GLANCING BLOW.
THE UPPER JET DYNAMICS AREN/T IMPRESSIVE AND THE LOW LEVEL JET IS
RATHER BENIGN LOOKING. SPC HAS BACKED OFF THE DAY 2 SLIGHT RISK TO
ONLY INCLUDE OUR FAR NORTHWEST COUNTIES...THIS FITS THE
DYNAMICS/FORCING BETTER.
WILL CONTINUE THE LIKELY POPS WITH FROPA AND HANG ONTO A SMALL
CHANCE THURSDAY MORNING FOR ANY SLOW TO EXIT PRECIP AREAS. COOLER
WEATHER ARRIVES ON NORTH TO NORTHEAST WINDS. A WELCOME RELIEF FROM
THE PREVIOUS HOT DAY.
FRIDAY AND BEYOND...FORECAST CONFIDENCE IS MEDIUM TO HIGH.
HIGH PRESSURE SETTLES OVER THE GREAT LAKES FOR FRIDAY AND MOVES
EAST TOWARD THE EAST COAST BY SUNDAY. AS IT DOES THIS...WE GET
BACK INTO A WARM SOUTHWEST FLOW. THE WARM ADVECTION...WAA..RESPONSE
SATURDAY NIGHT LOOKS LIMITED. THE ECMWF SUGGEST THE BULK OF ANY
LIGHT QPF WITH THE WAA WILL STAY ACROSS NORTHERN WISCONSIN WHILE
THE GFS HAS NO QPF. CAN/T TOTALLY RULE IT OUT ACROSS THE
SOUTH...BUT THERE ISN/T ENOUGH EVIDENCE TO INCLUDE PRECIP AT THIS
TIME FOR SATURDAY NIGHT. HIGHS BY SUNDAY AND MONDAY WILL BE BACK
INTO THE MID OR UPPER 80S. THE ECMWF SUGGESTS A FRONT WITH SOME
CONVECTION MAY DROP IN TOWARD TUESDAY OF NEXT WEEK. THE GFS WILL
HAVE NONE OF THAT. STAY TUNED.
AVIATION/00Z TAFS/...
PREDOMINATELY VFR CONDITIONS AND SOUTH TO SOUTHWEST WINDS EXPECTED
THROUGH THE FORECAST PERIOD...WITH FEW OR SCT LOW CLOUDS LINGERING
ABOVE 3000 FT. PATCHY FOG WILL BE POSSIBLE TONIGHT IN LOW LYING
AREAS AND NEAR RIVER VALLEYS...INCLUDING AROUND THE ENW AREA.
LOOK FOR THUNDERSTORMS TO MOVE IN TOMORROW NIGHT AS A COLD FRONT
PUSHES THROUGH. THE THUNDERSTORMS ARE EXPECTED TO BE AROUND MSN
BETWEEN 00Z AND 03Z...UES BETWEEN 03Z AND 06Z...AND MKE AND ENW
AFTER 06Z.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&
$$
UPDATE...REM
TONIGHT/WEDNESDAY AND AVIATION/MARINE...MEB
WEDNESDAY NIGHT THROUGH TUESDAY...DAVIS
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
1027 PM CDT TUE AUG 20 2013
UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE
.UPDATE...
ISSUED AT 926 PM CDT TUE AUG 20 2013
SML CLUSTER OF SHRA OVER CENTRAL WI HAS BEEN MAINTAINING
ITSELF...AND NOW EVEN INCREASED DURING THE PAST HR. HAVE BEEN
HANDLING IT AN HOUR OR TWO AT A TIME IN THE GRIDS. THE SHRA SEEM
TO BE TIED TO WK MID-LVL SHRTWV...WHICH SHOULD SHIFT EWD
OVERNIGHT. JUST DID A LITTLE MORE SUBSTANTIAL UPDATE TO KEEP SCT
SHRA IN CENTRAL WI THROUGH MIDNIGHT...THEN DECREASE THEM AFTER
THAT. WE/LL SEE HOW WELL THIS WORKS OUT.
&&
.SHORT TERM...TONIGHT AND WEDNESDAY
ISSUED AT 230 PM CDT TUE AUG 20 2013
LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A NEARLY
STATIONARY UPPER LOW SPINNING OVER THE CENTRAL MISSISSIPPI VALLEY
AND A COLD FRONT MOVING ACROSS THE NORTHERN PLAINS. AHEAD OF THE
FRONT...SOUTHWEST WINDS ARE ADVECTION MOISTURE IN THE 900-800MB
LAYER FROM THE CENTRAL PLAINS INTO WESTERN AND CENTRAL WISCONSIN
WHERE A WIDESPREAD CU FIELD FORMED MIDDAY. AREA RADARS SHOWED A FEW CELLS
POPPED UP THIS MORNING OVER IOWA BUT HAVE SINCE FIZZLED. NO OTHER
SIGNS OF SHOWERS POPPING DESPITE INHIBITION ERODING. AS THE FRONT
MOVES INTO THE REGION TOMORROW...SEVERE WEATHER CHANCES IS THE MAIN
FORECAST CONCERN.
TONIGHT...LOW LEVEL MOISTURE AXIS WILL INITIALLY EXTEND FROM CENTRAL
IOWA TO NORTH-CENTRAL WISCONSIN AT THE START OF THE PERIOD. WITH
SCT TO BKN 5-7KFT CIGS UPSTREAM...WILL KEEP SKIES SCT FOR A GOOD
PART OF THE NIGHT. HAVE NOT SEEN MORE SPECKLES ON RADAR ASSOCIATED
WITH THIS MOISTURE TRANSPORT REGIME...SO WILL STICK WITH A DRY
FORECAST DESPITE FORECAST SOUNDINGS SHOWING 1300 J/KG OF ELEVATED
CAPE. THE MOISTURE AXIS WILL SHIFT EAST THROUGH THE NIGHT AND REACH
EAST-CENTRAL AND NORTHEAST WISCONSIN AFTER MIDNIGHT. SO SHOULD SEE
SOME CLEARING OVER WESTERN SECTIONS AND AN INCREASE OF CLOUDS OVER
EASTERN WISCONSIN LATE. A WARM SOUTHWEST BREEZE AND INCREASING
MOISTURE WILL KEEP CONDITIONS MUGGY. LOWS MAINLY IN THE 60S.
WEDNESDAY...THE DAY WILL START OUT QUIET...AS THE MOISTURE AXIS
SHIFTS SOUTHEAST OF THE REGION...WHILE THE THERMAL AXIS ARRIVES
AHEAD OF A COLD FRONT WHICH WILL MOVE INTO NORTHWEST WISCONSIN BY
18Z. TEMPS SHOULD NOT HAVE MUCH OF A PROBLEM RISING INTO THE UPPER
80S TO LOW 90S AHEAD OF THE FRONT WEDNESDAY AFTERNOON. SOME HEAT
INDICES WILL LIKELY REACH INTO THE MIDDLE 90S. BUT THE BIGGER STORY
IS SEVERE WEATHER CHANCES WEDNESDAY AFTERNOON. THE COLD FRONT WILL
PUSH INTO NORTH-CENTRAL WISCONSIN MID TO LATE AFTERNOON DURING THE
TIME OF PEAK HEATING. THOUGH HEIGHT FALLS WILL EXIST WELL BEHIND
THE FRONT...CONVERGENCE AND FGEN ALONG THE FRONT LOOK DECENT. SOME
POTENTIAL FOR DEWPOINTS TO MIX OUT INTO THE MIDDLE 60S AHEAD OF THE
FRONT BUT THAT SHOULD NOT HURT INSTABILITY TOO MUCH. MODIFYING A NAM
PROGGED SOUNDING AT 21Z NEAR RHINELANDER USING A 88/68 PARCEL YIELDS
NEARLY 3500 J/KG OF ML CAPE. IF DEWPOINTS DO MIX OUT INTO THE MID
60S...INSTABILITY WILL DROP TO 2500 J/KG. FREEZING LEVELS ARE QUITE
HIGH AT 14.5 KFT...BUT MID-LEVEL LAPSE RATES OF 6.5-7 C/KM AND
PLENTY OF CAPE SAYS THAT LARGE HAIL IS ALSO A THREAT IN ADDITION TO
DAMAGING WINDS. 0-6KM BULK SHEAR IS 25-30 KTS WHICH SUGGESTS
MULTI-CELLS TO SOME SMALL BOWS ARE POSSIBLE. TIMING WISE...LOOKING
AT A MID AFTERNOON FOR N-C WISCONSIN...AND LATE AFTERNOON TO EARLY
EVENING OVER CENTRAL AND FAR NORTHEAST WISCONSIN.
.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY
ISSUED AT 230 PM CDT TUE AUG 20 2013
LITTLE CHANGE WITH THE GOING FORECAST FOR WEDNESDAY NIGHT WITH
RESPECT TO THE POTENTIAL OF STRONG TO SEVERE STORMS. PLENTY OF
INSTABILITY WITH CAPES BETWEEN 2000 TO 3000 J/KG AVAILABLE ALONG
AND AHEAD OF A COLD FRONT DROPPING OVER THE GREAT LAKES REGION.
SHORT WAVE TROUGH DIVING INTO THE NORTHERN GREAT LAKES REGION WITH
A RRQ REGION OF A JET WILL BE ASSOCIATED WITH THE FRONTAL PASSAGE.
INCREASING W/NW MID LEVEL WINDS LATER AFTERNOON AND EVENING WILL
PROVIDE SOME DEEPER SHEAR WITH THE FRONT. DAMAGING WINDS AND HAIL
THE PRIMARY THREATS. PWATS NEAR 1.85 INCHES AHEAD AND ALONG THE
FRONT AND HEAVY RAIN FALL POSSIBLE AFTERNOON AND EVENING NEAR THE
RRQ REGION OF THE JET ACROSS THE NORTH IF STORMS TRAIN FOR A
PERIOD OF TIME.
HIGH PRESSURE DRIFTING OVER THE STATE THURSDAY INTO FRIDAY WILL
PROVIDE QUIET CONDITIONS ALONG WITH NEAR NORMAL TEMPERATURES AND A
DRIER AIR MASS.
WARM AND MORE HUMID AIR TO RETURN AGAIN THIS WEEKEND AND INTO
EARLY NEXT WEEK...AS THE UPPER RIDGE BUILDS INTO THE NORTHERN
PLAINS AND GREAT LAKES REGION. MDM RANGE MODELS IN GENERAL WERE
MAINLY FOCUSING PERIODS OF CONVECTION ON THE PERIMETER OF THE
RIDGE WITH PWATS INCREASING TO 1.50 TO 2.00 OVER THE NORTHERN
GREAT LAKES REGION. WITH THE RETURN OF AN UNSTABLE AIR MASS ALONG
WITH A CAP EDGE LOOMING NEAR OR OVER NORTHERN WISCONSIN...POTENTIAL
OF AT LEAST STRONG STORMS FOR LATER INTO THE WEEKEND AND INTO NEXT
WEEK FOR PART OF THE FORECAST AREA.
&&
.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1025 PM CDT TUE AUG 20 2013
LINGERING SHRA WORKING EWD FM CENTRAL WI. MAY NEED TO MENTION FOR
A FEW HRS IN THE GRB/AUW TAFS. OTHERWISE...LITTLE CHG FM PREVIOUS
THINKING. INCREASED LOW-LEVEL MOISTURE WL PROBABLY LEAD TO SOME FG
OVERNIGHT...BUT VSBYS PROBABLY WON/T DROP BLO MVFR CATEGORY DUE TO
SUSTAINED SFC PRESSURE GRADIENT/MIXING. PRETTY SHARP FRONT WL PUSH
ACRS THE AREA TOMORROW. THAT SEEMS WORTHY OF EXPLICIT INCLUSION OF
THUNDER IN THE TAFS. WL FOCUS TIMING IN THE TAFS ON MOST LIKELY
TIME OF OCCURRENCE...THOUGH ACTUAL WINDOW OF OPPORTUNITY FOR TSRA
WL BE SOMEWHAT LARGER. &&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE.........SKOWRONSKI
SHORT TERM.....MPC
LONG TERM......TDH
AVIATION.......SKOWRONSKI
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
931 PM CDT TUE AUG 20 2013
NEW INFORMATION ADDED TO UPDATE SECTION
.UPDATE...
ISSUED AT 926 PM CDT TUE AUG 20 2013
SML CLUSTER OF SHRA OVER CENTRAL WI HAS BEEN MAINTAINING
ITSELF...AND NOW EVEN INCREASED DURING THE PAST HR. HAVE BEEN
HANDLING IT AN HOUR OR TWO AT A TIME IN THE GRIDS. THE SHRA SEEM
TO BE TIED TO WK MID-LVL SHRTWV...WHICH SHOULD SHIFT EWD
OVERNIGHT. JUST DID A LITTLE MORE SUBSTANTIAL UPDATE TO KEEP SCT
SHRA IN CENTRAL WI THROUGH MIDNIGHT...THEN DECREASE THEM AFTER
THAT. WE/LL SEE HOW WELL THIS WORKS OUT.
&&
.SHORT TERM...TONIGHT AND WEDNESDAY
ISSUED AT 230 PM CDT TUE AUG 20 2013
LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A NEARLY
STATIONARY UPPER LOW SPINNING OVER THE CENTRAL MISSISSIPPI VALLEY
AND A COLD FRONT MOVING ACROSS THE NORTHERN PLAINS. AHEAD OF THE
FRONT...SOUTHWEST WINDS ARE ADVECTION MOISTURE IN THE 900-800MB
LAYER FROM THE CENTRAL PLAINS INTO WESTERN AND CENTRAL WISCONSIN
WHERE A WIDESPREAD CU FIELD FORMED MIDDAY. AREA RADARS SHOWED A FEW CELLS
POPPED UP THIS MORNING OVER IOWA BUT HAVE SINCE FIZZLED. NO OTHER
SIGNS OF SHOWERS POPPING DESPITE INHIBITION ERODING. AS THE FRONT
MOVES INTO THE REGION TOMORROW...SEVERE WEATHER CHANCES IS THE MAIN
FORECAST CONCERN.
TONIGHT...LOW LEVEL MOISTURE AXIS WILL INITIALLY EXTEND FROM CENTRAL
IOWA TO NORTH-CENTRAL WISCONSIN AT THE START OF THE PERIOD. WITH
SCT TO BKN 5-7KFT CIGS UPSTREAM...WILL KEEP SKIES SCT FOR A GOOD
PART OF THE NIGHT. HAVE NOT SEEN MORE SPECKLES ON RADAR ASSOCIATED
WITH THIS MOISTURE TRANSPORT REGIME...SO WILL STICK WITH A DRY
FORECAST DESPITE FORECAST SOUNDINGS SHOWING 1300 J/KG OF ELEVATED
CAPE. THE MOISTURE AXIS WILL SHIFT EAST THROUGH THE NIGHT AND REACH
EAST-CENTRAL AND NORTHEAST WISCONSIN AFTER MIDNIGHT. SO SHOULD SEE
SOME CLEARING OVER WESTERN SECTIONS AND AN INCREASE OF CLOUDS OVER
EASTERN WISCONSIN LATE. A WARM SOUTHWEST BREEZE AND INCREASING
MOISTURE WILL KEEP CONDITIONS MUGGY. LOWS MAINLY IN THE 60S.
WEDNESDAY...THE DAY WILL START OUT QUIET...AS THE MOISTURE AXIS
SHIFTS SOUTHEAST OF THE REGION...WHILE THE THERMAL AXIS ARRIVES
AHEAD OF A COLD FRONT WHICH WILL MOVE INTO NORTHWEST WISCONSIN BY
18Z. TEMPS SHOULD NOT HAVE MUCH OF A PROBLEM RISING INTO THE UPPER
80S TO LOW 90S AHEAD OF THE FRONT WEDNESDAY AFTERNOON. SOME HEAT
INDICES WILL LIKELY REACH INTO THE MIDDLE 90S. BUT THE BIGGER STORY
IS SEVERE WEATHER CHANCES WEDNESDAY AFTERNOON. THE COLD FRONT WILL
PUSH INTO NORTH-CENTRAL WISCONSIN MID TO LATE AFTERNOON DURING THE
TIME OF PEAK HEATING. THOUGH HEIGHT FALLS WILL EXIST WELL BEHIND
THE FRONT...CONVERGENCE AND FGEN ALONG THE FRONT LOOK DECENT. SOME
POTENTIAL FOR DEWPOINTS TO MIX OUT INTO THE MIDDLE 60S AHEAD OF THE
FRONT BUT THAT SHOULD NOT HURT INSTABILITY TOO MUCH. MODIFYING A NAM
PROGGED SOUNDING AT 21Z NEAR RHINELANDER USING A 88/68 PARCEL YIELDS
NEARLY 3500 J/KG OF ML CAPE. IF DEWPOINTS DO MIX OUT INTO THE MID
60S...INSTABILITY WILL DROP TO 2500 J/KG. FREEZING LEVELS ARE QUITE
HIGH AT 14.5 KFT...BUT MID-LEVEL LAPSE RATES OF 6.5-7 C/KM AND
PLENTY OF CAPE SAYS THAT LARGE HAIL IS ALSO A THREAT IN ADDITION TO
DAMAGING WINDS. 0-6KM BULK SHEAR IS 25-30 KTS WHICH SUGGESTS
MULTI-CELLS TO SOME SMALL BOWS ARE POSSIBLE. TIMING WISE...LOOKING
AT A MID AFTERNOON FOR N-C WISCONSIN...AND LATE AFTERNOON TO EARLY
EVENING OVER CENTRAL AND FAR NORTHEAST WISCONSIN.
.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY
ISSUED AT 230 PM CDT TUE AUG 20 2013
LITTLE CHANGE WITH THE GOING FORECAST FOR WEDNESDAY NIGHT WITH
RESPECT TO THE POTENTIAL OF STRONG TO SEVERE STORMS. PLENTY OF
INSTABILITY WITH CAPES BETWEEN 2000 TO 3000 J/KG AVAILABLE ALONG
AND AHEAD OF A COLD FRONT DROPPING OVER THE GREAT LAKES REGION.
SHORT WAVE TROUGH DIVING INTO THE NORTHERN GREAT LAKES REGION WITH
A RRQ REGION OF A JET WILL BE ASSOCIATED WITH THE FRONTAL PASSAGE.
INCREASING W/NW MID LEVEL WINDS LATER AFTERNOON AND EVENING WILL
PROVIDE SOME DEEPER SHEAR WITH THE FRONT. DAMAGING WINDS AND HAIL
THE PRIMARY THREATS. PWATS NEAR 1.85 INCHES AHEAD AND ALONG THE
FRONT AND HEAVY RAIN FALL POSSIBLE AFTERNOON AND EVENING NEAR THE
RRQ REGION OF THE JET ACROSS THE NORTH IF STORMS TRAIN FOR A
PERIOD OF TIME.
HIGH PRESSURE DRIFTING OVER THE STATE THURSDAY INTO FRIDAY WILL
PROVIDE QUIET CONDITIONS ALONG WITH NEAR NORMAL TEMPERATURES AND A
DRIER AIR MASS.
WARM AND MORE HUMID AIR TO RETURN AGAIN THIS WEEKEND AND INTO
EARLY NEXT WEEK...AS THE UPPER RIDGE BUILDS INTO THE NORTHERN
PLAINS AND GREAT LAKES REGION. MDM RANGE MODELS IN GENERAL WERE
MAINLY FOCUSING PERIODS OF CONVECTION ON THE PERIMETER OF THE
RIDGE WITH PWATS INCREASING TO 1.50 TO 2.00 OVER THE NORTHERN
GREAT LAKES REGION. WITH THE RETURN OF AN UNSTABLE AIR MASS ALONG
WITH A CAP EDGE LOOMING NEAR OR OVER NORTHERN WISCONSIN...POTENTIAL
OF AT LEAST STRONG STORMS FOR LATER INTO THE WEEKEND AND INTO NEXT
WEEK FOR PART OF THE FORECAST AREA.
&&
.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 602 PM CDT TUE AUG 20 2013
FAIRLY QUIET WX EXPECTED UNTIL COLD FRONT SURGES INTO THE AREA
TOMORROW AFTN. INCREASED LOW-LEVEL MOISTURE WL PROBABLY LEAD TO
MORE WIDESPREAD FG OVERNIGHT...BUT VSBYS PROBABLY WON/T DROP BLO
MVFR CATEGORY DUE TO SUSTAINED SFC PRESSURE GRADIENT/MIXING.
PRETTY SHARP FRONT WL PUSH ACRS THE AREA TOMORROW. THAT SEEMS
WORTHY OF EXPLICIT INCLUSION OF THUNDER IN THE TAFS. WL FOCUS
TIMING IN THE TAFS ON MOST LIKELY TIME OF OCCURRENCE...THOUGH
ACTUAL WINDOW OF OPPORTUNITY FOR TSRA WL BE SOMEWHAT LARGER.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE.........SKOWRONSKI
SHORT TERM.....MPC
LONG TERM......TDH
AVIATION.......SKOWRONSKI
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
607 PM CDT TUE AUG 20 2013
UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE
.SHORT TERM...TONIGHT AND WEDNESDAY
ISSUED AT 230 PM CDT TUE AUG 20 2013
LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A NEARLY
STATIONARY UPPER LOW SPINNING OVER THE CENTRAL MISSISSIPPI VALLEY
AND A COLD FRONT MOVING ACROSS THE NORTHERN PLAINS. AHEAD OF THE
FRONT...SOUTHWEST WINDS ARE ADVECTION MOISTURE IN THE 900-800MB
LAYER FROM THE CENTRAL PLAINS INTO WESTERN AND CENTRAL WISCONSIN
WHERE A WIDESPREAD CU FIELD FORMED MIDDAY. AREA RADARS SHOWED A FEW CELLS
POPPED UP THIS MORNING OVER IOWA BUT HAVE SINCE FIZZLED. NO OTHER
SIGNS OF SHOWERS POPPING DESPITE INHIBITION ERODING. AS THE FRONT
MOVES INTO THE REGION TOMORROW...SEVERE WEATHER CHANCES IS THE MAIN
FORECAST CONCERN.
TONIGHT...LOW LEVEL MOISTURE AXIS WILL INITIALLY EXTEND FROM CENTRAL
IOWA TO NORTH-CENTRAL WISCONSIN AT THE START OF THE PERIOD. WITH
SCT TO BKN 5-7KFT CIGS UPSTREAM...WILL KEEP SKIES SCT FOR A GOOD
PART OF THE NIGHT. HAVE NOT SEEN MORE SPECKLES ON RADAR ASSOCIATED
WITH THIS MOISTURE TRANSPORT REGIME...SO WILL STICK WITH A DRY
FORECAST DESPITE FORECAST SOUNDINGS SHOWING 1300 J/KG OF ELEVATED
CAPE. THE MOISTURE AXIS WILL SHIFT EAST THROUGH THE NIGHT AND REACH
EAST-CENTRAL AND NORTHEAST WISCONSIN AFTER MIDNIGHT. SO SHOULD SEE
SOME CLEARING OVER WESTERN SECTIONS AND AN INCREASE OF CLOUDS OVER
EASTERN WISCONSIN LATE. A WARM SOUTHWEST BREEZE AND INCREASING
MOISTURE WILL KEEP CONDITIONS MUGGY. LOWS MAINLY IN THE 60S.
WEDNESDAY...THE DAY WILL START OUT QUIET...AS THE MOISTURE AXIS
SHIFTS SOUTHEAST OF THE REGION...WHILE THE THERMAL AXIS ARRIVES
AHEAD OF A COLD FRONT WHICH WILL MOVE INTO NORTHWEST WISCONSIN BY
18Z. TEMPS SHOULD NOT HAVE MUCH OF A PROBLEM RISING INTO THE UPPER
80S TO LOW 90S AHEAD OF THE FRONT WEDNESDAY AFTERNOON. SOME HEAT
INDICES WILL LIKELY REACH INTO THE MIDDLE 90S. BUT THE BIGGER STORY
IS SEVERE WEATHER CHANCES WEDNESDAY AFTERNOON. THE COLD FRONT WILL
PUSH INTO NORTH-CENTRAL WISCONSIN MID TO LATE AFTERNOON DURING THE
TIME OF PEAK HEATING. THOUGH HEIGHT FALLS WILL EXIST WELL BEHIND
THE FRONT...CONVERGENCE AND FGEN ALONG THE FRONT LOOK DECENT. SOME
POTENTIAL FOR DEWPOINTS TO MIX OUT INTO THE MIDDLE 60S AHEAD OF THE
FRONT BUT THAT SHOULD NOT HURT INSTABILITY TOO MUCH. MODIFYING A NAM
PROGGED SOUNDING AT 21Z NEAR RHINELANDER USING A 88/68 PARCEL YIELDS
NEARLY 3500 J/KG OF ML CAPE. IF DEWPOINTS DO MIX OUT INTO THE MID
60S...INSTABILITY WILL DROP TO 2500 J/KG. FREEZING LEVELS ARE QUITE
HIGH AT 14.5 KFT...BUT MID-LEVEL LAPSE RATES OF 6.5-7 C/KM AND
PLENTY OF CAPE SAYS THAT LARGE HAIL IS ALSO A THREAT IN ADDITION TO
DAMAGING WINDS. 0-6KM BULK SHEAR IS 25-30 KTS WHICH SUGGESTS
MULTI-CELLS TO SOME SMALL BOWS ARE POSSIBLE. TIMING WISE...LOOKING
AT A MID AFTERNOON FOR N-C WISCONSIN...AND LATE AFTERNOON TO EARLY
EVENING OVER CENTRAL AND FAR NORTHEAST WISCONSIN.
.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY
ISSUED AT 230 PM CDT TUE AUG 20 2013
LITTLE CHANGE WITH THE GOING FORECAST FOR WEDNESDAY NIGHT WITH
RESPECT TO THE POTENTIAL OF STRONG TO SEVERE STORMS. PLENTY OF
INSTABILITY WITH CAPES BETWEEN 2000 TO 3000 J/KG AVAILABLE ALONG
AND AHEAD OF A COLD FRONT DROPPING OVER THE GREAT LAKES REGION.
SHORT WAVE TROUGH DIVING INTO THE NORTHERN GREAT LAKES REGION WITH
A RRQ REGION OF A JET WILL BE ASSOCIATED WITH THE FRONTAL PASSAGE.
INCREASING W/NW MID LEVEL WINDS LATER AFTERNOON AND EVENING WILL
PROVIDE SOME DEEPER SHEAR WITH THE FRONT. DAMAGING WINDS AND HAIL
THE PRIMARY THREATS. PWATS NEAR 1.85 INCHES AHEAD AND ALONG THE
FRONT AND HEAVY RAIN FALL POSSIBLE AFTERNOON AND EVENING NEAR THE
RRQ REGION OF THE JET ACROSS THE NORTH IF STORMS TRAIN FOR A
PERIOD OF TIME.
HIGH PRESSURE DRIFTING OVER THE STATE THURSDAY INTO FRIDAY WILL
PROVIDE QUIET CONDITIONS ALONG WITH NEAR NORMAL TEMPERATURES AND A
DRIER AIR MASS.
WARM AND MORE HUMID AIR TO RETURN AGAIN THIS WEEKEND AND INTO
EARLY NEXT WEEK...AS THE UPPER RIDGE BUILDS INTO THE NORTHERN
PLAINS AND GREAT LAKES REGION. MDM RANGE MODELS IN GENERAL WERE
MAINLY FOCUSING PERIODS OF CONVECTION ON THE PERIMETER OF THE
RIDGE WITH PWATS INCREASING TO 1.50 TO 2.00 OVER THE NORTHERN
GREAT LAKES REGION. WITH THE RETURN OF AN UNSTABLE AIR MASS ALONG
WITH A CAP EDGE LOOMING NEAR OR OVER NORTHERN WISCONSIN...POTENTIAL
OF AT LEAST STRONG STORMS FOR LATER INTO THE WEEKEND AND INTO NEXT
WEEK FOR PART OF THE FORECAST AREA.
&&
.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 602 PM CDT TUE AUG 20 2013
FAIRLY QUIET WX EXPECTED UNTIL COLD FRONT SURGES INTO THE AREA
TOMORROW AFTN. INCREASED LOW-LEVEL MOISTURE WL PROBABLY LEAD TO
MORE WIDESPREAD FG OVERNIGHT...BUT VSBYS PROBABLY WON/T DROP BLO
MVFR CATEGORY DUE TO SUSTAINED SFC PRESSURE GRADIENT/MIXING.
PRETTY SHARP FRONT WL PUSH ACRS THE AREA TOMORROW. THAT SEEMS
WORTHY OF EXPLICIT INCLUSION OF THUNDER IN THE TAFS. WL FOCUS
TIMING IN THE TAFS ON MOST LIKELY TIME OF OCCURRENCE...THOUGH
ACTUAL WINDOW OF OPPORTUNITY FOR TSRA WL BE SOMEWHAT LARGER.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......TDH
AVIATION.......SKOWRONSKI
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
537 PM CDT MON AUG 19 2013
UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE
.SHORT TERM...TONIGHT AND TUESDAY
ISSUED AT 227 PM CDT MON AUG 19 2013
LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A SHORTWAVE
TROUGH MOVING EAST OVER EASTERN MINNESOTA EARLY THIS AFTERNOON.
EARLIER SHOWERS AND STORMS OVER NORTHWEST WISCONSIN FIZZLED AND
THINGS REMAIN QUIET DESPITE DECENT MU CAPES OF OVER 1000 J/KG. WILL
LEAVE A SLIGHT CHANCE OF PRECIP FOR THE REST OF THE AFTERNOON OVER
N-C WISCONSIN THOUGH. CLOUD COVER HAS HELD BACK TEMPS
SOMEWHAT...AND ARE ONLY IN THE UPPER 70S ACROSS THE NORTH. LOOKING
FARTHER UPSTREAM...PLENTY OF CLEAR CONDITIONS OVER THE NORTHERN
PLAINS. SMALL PRECIP CHANCES AND TEMPS ARE THE MAIN FORECAST
CONCERNS IN THE SHORT-TERM.
TONIGHT...THE SHORTWAVE TROUGH MOVING OVER THE WESTERN GREAT LAKES
WILL SHEAR APART INTO TWO FEATURES. ONE WAVE WILL CONTINUE TO MOVE
EAST OVER SOUTHERN ONTARIO WHILE THE OTHER DIVES SOUTH ACROSS IOWA.
AS THIS OCCURS...BAND OF MID AND HIGH LEVEL MOISTURE WILL GET
STRETCHED AND DIMINISH...SO ANTICIPATE CLEARING SKIES TO OCCUR THIS
EVENING. THEN THE 850MB MOISTURE PLUME OVER THE CENTRAL AND
NORTHERN PLAINS EDGES EAST AND NOSES INTO WESTERN AND NORTHERN
WISCONSIN LATE TONIGHT. SCT TO WIDELY SCT CLOUDS ARE OCCURRING
WITHIN THIS MOISTURE PLUME AND BUFKIT SOUNDINGS AT RHI INDICATE
SKINNY CAPE UPWARDS OF 1000 J/KG DEVELOPING BY 09Z. WITH MOISTURE
TRANSPORT OCCURRING...CHANCES OF PRECIP ARE NOT NEGLIGIBLE...BUT
PLENTY OF DRY AIR EXISTS ABOVE 850MB AND MID-LEVEL LAPSE RATES ARE
RATHER POOR. WILL CONTINUE WITH THE DRY FORECAST. MUGGIER CONDITIONS
WITH LOWS IN THE UPPER 50S TO LOW 60S.
TUESDAY...LOW LEVEL MOISTURE PLUME WILL STRETCH FROM KANSAS TO
NORTHWEST WISCONSIN...PUSHING DEWPOINTS INTO THE MIDDLE 60S. WITH
TEMPS RISING INTO THE MID TO UPPER 80S...SHOULD SEE A DECENT CU
FIELD DEVELOP OVER CENTRAL AND NORTH-CENTRAL WISCONSIN. DESPITE
MID-LEVEL CAPPING...ML CAPES TOMORROW WILL REACH UPWARDS OF 2K J/KG
WITH NO CIN. NO TRIGGER ALOFT SO WILL GO WITH THE CONSENSUS WHICH
IS A DRY FORECAST.
.LONG TERM...TUESDAY NIGHT THROUGH MONDAY
ISSUED AT 227 PM CDT MON AUG 19 2013
FOCUS OF THIS PERIOD OF THE FORECAST WILL BE THE COLD FRONT
PASSAGE WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. THIS COLD FRONT
WILL BE SUPPORTED BY A SHORT WAVE TROUGH DROPPING INTO THE
NORTHERN GREAT LAKES REGION ALONG WITH A RRQ REGION OF THE UPPER
JET. INCREASING MOIST WARM UNSTABLE AIR MASS PRODUCING CAPES FROM
2500 TO 3000 J/KG FOR THE AFTERNOON HOURS AHEAD OF THE FRONT.
GOING HWO WILL CONTINUE TO HIGHLIGHT THE SVR THREAT. HEAT INDEX
NUMBERS ALSO CLIMB INTO THE LOWER 90S AHEAD OF THE FRONT ON
WEDNESDAY.
MEDIUM RANGE MODELS CONSISTENT WITH DRIVING THE FRONT SOUTH ON
THURSDAY FOR DRIER CONDITIONS AND MORE NORMAL TEMPERATURES.
PRECIPITATION TRENDS BECOME A CHALLENGE AGAIN LATER FRIDAY INTO
NEXT MONDAY. RETURN FLOW FRIDAY NIGHT INTO SATURDAY MAY PRODUCE A
PERIOD OF WAA CONVECTION...FOLLOWED BY PERIODS OF CONVECTION ON
THE NORTHERN PERIMETER OF THE BUILDING UPPER RIDGE LATER WEEKEND
INTO NEXT MONDAY. ORIENTATION OF THIS RIDGE WILL PLAY A ROLE WHERE
THE BEST CHANCE OF CONVECTION OCCURS. WITH THE BUILDING RIDGE
AGAIN THIS WEEKEND INTO NEXT WEEK...THE WARM AND MORE HUMID
AIR MASS WILL RETURN. HEAT INDEX NUMBERS LIKELY TO CLIMB BACK INTO
THE LOWER 90S EXCEPT FOR LOCATIONS ACROSS THE NORTH WHWERE
CONVECTION CAN DEVELOP.
&&
.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 532 PM CDT MON AUG 19 2013
DECOUPLING OVERNIGHT WL ALLOW WINDS TO DIMINISH AND GUSTINESS TO
END. INCREASED MOISTURE COULD RESULT IN SOME MVFR VSBYS BY MORNING
IN FG/HZ. DEEPENING MIXING WL BRING BACK THE GUSTINESS TO THE WIND
AGAIN TOMORROW. INCREASED MOISTURE COULD RESULT IN SOME LOWER-END
VFR CIGS BY EARLY TOMORROW AFTN...ESP IN C/N-C WI. ATM WL
DESTABILIZE SOME AND THERE DOESN/T APPEAR TO BE ANY CINH REMAINING
IN FCST SOUDNINGS. BUT GIVEN THE LACK OF A TRIGGER...EXPECT
CONVECTION TO BE ISOLD AT BEST AND THUS RISK OF GETTING TSRA AT
TAF SITES NOT GREAT ENOUGH TO WARRANT INCLUSION IN TAFS AT THIS
POINT.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......TDH
AVIATION.......SKOWRONSKI
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
249 PM CDT MON AUG 19 2013
.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 249 PM CDT MON AUG 19 2013
MAIN FORECAST CONCERNS ARE ON ANY POTENTIAL PRECIPITATION TONIGHT
AND THEN TEMPERATURES FOR TUESDAY.
CURRENTLY AS OF 19Z...
WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS SHOWED TROUGHING
ALONG THE WEST COAST OF BRITISH COLUMBIA...UPPER RIDGING FROM THE
SOUTHWESTERN U.S. INTO THE DAKOTAS...AND A SHORTWAVE TROUGH OVER
CENTRAL MN. THE MAIN IMPACT TO THE FORECAST AREA WITH THE SHORTWAVE
TROUGH HAS BEEN TO SPREAD SOME MID AND HIGH CLOUDS ACROSS. DRY AIR
IN THE MID LEVELS OF THE ATMOSPHERE SEEN ON THE 12Z MPX SOUNDING...
AS WELL AS A CAPPING INVERSION AT 750MB ON THAT SOUNDING...HAS
PREVENTED THE SHORTWAVE FROM PRODUCING PRECIPITATION IN THE FORECAST
AREA. THE CLOUD COVER HAS ALSO HELD BACK TEMPERATURES FROM REACHING
THEIR MAXIMUM POTENTIAL. 16C 850MB TEMP ON THE MPX SOUNDING WAS
ADVECTING EAST INTO THE FORECAST AREA...WHICH NORMALLY WOULD SUPPORT
MID TO EVEN UPPER 80S WITH CLEAR SKIES. HOWEVER...THE CLOUDS HAVE
HELD TEMPS DOWN INTO THE UPPER 70S TO LOW 80S THUS FAR. LOW LEVEL
SOUTHERLY FLOW HAS SLOWLY BEEN BRINGING IN MORE MOISTURE WITH
DEWPOINTS IN THE UPPER 50S TO LOW 60S. TO THE NORTHWEST...A COLD
FRONT STRETCHED FROM CENTRAL MANITOBA INTO WESTERN MONTANA. AHEAD OF
THE FRONT...12Z RAOBS SHOWED EVEN WARMER AIR ACROSS THE NORTHERN
PLAINS...WITH 850MB READINGS OF 20-25C AT BIS...ABR...UNR AND GGW.
700MB TEMPS WERE WARMING AS WELL...BETWEEN 8-13C.
SYNOPTIC OVERVIEW...
THE SHORTWAVE TROUGH OVER CENTRAL MN IS PROGGED TO DROP SOUTH
THROUGH THE FORECAST AREA THIS EVENING...WITH THE EXTENSION OF THE
UPPER RIDGE OVER THE DAKOTAS FOLLOWING IN BEHIND IT FOR THE
OVERNIGHT HOURS INTO TUESDAY.
DETAILS...
GIVEN THE DRY AIRMASS IN PLACE SUB THE MID-CLOUD LAYER AS WELL AS
THE CAPPING...NOT ANTICIPATING ANY PRECIPITATION TO ACCOMPANY THE
SHORTWAVE AS IT DROPS THROUGH THE FORECAST AREA THIS EVENING. WE
SHOULD SEE SOME CLEARING AS WELL...BOTH OF THE MID/HIGH CLOUDS AND
DIURNAL CUMULUS...AS SUBSIDENCE WORKS IN BEHIND THE SHORTWAVE
TROUGH. 850MB MOISTURE TRANSPORT THEN KICKS IN...TRANSPORTING MORE
LOW LEVEL MOISTURE INTO THE AREA. THE 19.12Z NAM/REGIONAL CANADIAN
BOTH DEVELOP A FEW ACCAS TYPE SHOWERS AND THUNDERSTORMS ON THE EDGE
OF THIS MOISTURE TRANSPORT FROM SOUTHEAST MN INTO NORTHWEST WI.
THESE ARE REALLY THE ONLY MODELS SHOWING THIS...AND WITH A BROAD
850MB MOISTURE TRANSPORT PLUME PROGGED COMBINED WITH SUBSIDENCE...
THINK THEY ARE OVERDONE AND KEPT A DRY FORECAST GOING. WORTH KEEPING
AN EYE ON...THOUGH.
THE MORE MOISTURE COMING IN COMBINED WITH DAYTIME HEATING SHOULD
YIELD TO PLENTY OF CUMULUS ON TUESDAY. LITTLE IN THE WAY OF CAPPING
IS PROGGED TOMORROW WITH MLCIN VALUES DROPPING TO 30-40 J/KG IN THE
AFTERNOON...WHILE MLCAPES GROW TO 1500-2500 J/KG. HOWEVER...THERE IS
NO TRIGGER PRESENT TO ALLOW THE RELEASE OF THE INSTABILITY.
THEREFORE...DRY CONDITIONS ARE FORECAST THROUGH TUESDAY.
TEMPERATURES TONIGHT EXPECTED TO BE WARMER...ESPECIALLY OVER THE
NORTHWEST HALF OF THE FORECAST AREA...DUE TO A SOUTHERLY BREEZE AND
HIGHER DEWPOINTS. THE SOUTHERLY BREEZE SHOULD PRECLUDE VALLEY
FOG PRETTY MUCH EVERYWHERE EXCEPT FOR THE WISCONSIN RIVER VALLEY.
850MB AND 925MB TEMPS ARE PROGGED ABOUT 2-3C HIGHER ON TUESDAY
AFTERNOON COMPARED TO THIS AFTERNOON. THESE WARMER TEMPS COMBINED
WITH MORE SUN WILL LEAD TO WARMER CONDITIONS...LIKELY BY 5 OR SO
DEGREES.
.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 249 PM CDT MON AUG 19 2013
HAZARDS...
HEAT INDICES MAY GET CLOSE TO ADVISORY CRITERIA ON WEDNESDAY AND
AGAIN SUNDAY AND MONDAY. ALSO MONITORING POTENTIAL SEVERE WEATHER
FOR LATE WEDNESDAY.
SYNOPTIC OVERVIEW...
TROUGHING ALONG THE WEST COAST OF BRITISH COLUMBIA IS FORECAST
CONCERN NUMBER 1...WITH MODELS STRUGGLING A BIT ON THE AMPLITUDE OF
THE TROUGH AS IT CROSSES SOUTHERN CANADA THE NEXT COUPLE OF DAYS.
SOME PAST GFS RUNS INDICATED THE TROUGH COULD DIP INTO NORTHERN
MINNESOTA LATE WEDNESDAY...WHEREAS THE ECMWF AS WELL AS THE 19.12Z
GFS KEEP IT TO THE NORTH CROSSING NORTHERN ONTARIO. THIS IS
IMPORTANT AS IT IMPACTS HOW FAR SOUTH DYNAMICAL FORCING WILL REACH
INTO THE FORECAST AREA. ADDITIONALLY...THIS SHORTWAVE TROUGH IS
GOING TO DICTATE THE SPEED OF THE COLD FRONT OVER MONTANA...THE
FORCING ON THE FRONT...AND HOW FAR SOUTH THE FRONT GETS HEADING INTO
THURSDAY AND THURSDAY NIGHT. GOOD MODEL AGREEMENT PERSISTS HEADING
INTO NEXT WEEKEND AS THE SUMMER HEAT RIDGE BUILDS AND STRENGTHENS
OVER THE NATIONS HEARTLAND. VERY LITTLE MOVEMENT OF THIS RIDGE IS
SUGGESTED BY MONDAY.
TUESDAY NIGHT THROUGH THURSDAY...
FOCUS IS ON THE COLD FRONT APPROACHING THE AREA. ALL MODELS ARE
SHOWING AN ELEVATED MIX LAYER...I.E. THE WARMER 850MB AND 700MB AIR
PRESENT CURRENTLY OVER THE NORTHERN PLAINS...ADVECTING INTO THE
FORECAST AREA TUESDAY NIGHT AND WEDNESDAY AHEAD OF THE FRONT. THE
EXACT WARMTH IS ONE FACTOR THAT WILL PLAY INTO WHETHER OR NOT THIS
FRONT CAN INITIATE CONVECTION WEDNESDAY AFTERNOON. ANOTHER FACTOR IS
MOISTURE...WHICH THE 19.12Z GFS AND NAM BOTH APPEAR TO BE OVERDOING
THE SURFACE DEWPOINTS. THEY PROG VALUES IN THE 70-75 RANGE WHILE
MIXING AND THE DRYING SOILS SHOULD RESULT IN READINGS MORE IN THE
MID/UPPER 60S. THESE MIXED LAYER DEWPOINTS RESULT IN MLCIN VALUES OF
30-50 J/KG. A THIRD FACTOR OF CONCERN IS LOW LEVEL CONVERGENCE...
WHICH THE NAM AND GFS BOTH PROG WEAK TO NOTHING PRIOR TO THEIR
CONVECTIVE SCHEMES GOING OFF. THUS...THERE IS PLENTY OF UNCERTAINTY
ON THE EXTENT OF POTENTIAL CONVECTION. IN REALITY...THERE IS A
BETTER SHOT FOR CONVECTION ONCE THE FRONT PASSES...DUE TO THE
DEVELOPMENT OF A POST-FRONTAL LOW TO MID LEVEL FRONTOGENESIS ZONE.
HAVE TAILORED PRECIPITATION CHANCES IN THIS WAY WITH HIGHER VALUES
WEDNESDAY NIGHT. PRECIPITATION CHANCES CONTINUE INTO THURSDAY...
MAINLY SOUTH OF I-90...WHERE THE FRONTOGENESIS ZONE MAY STILL BE
LINGERING. THIS IS ALL DEPENDS ON HOW FAR SOUTH THE FRONT MAKES
IT...THOUGH.
FOR SEVERE WEATHER POTENTIAL...THE 0-6KM SHEAR IS SERIOUSLY LAGGING
THE FRONT. 25 KT IS ABOUT THE HIGHEST AT 00Z AND THATS UP NEAR EAU
CLAIRE. 0-3 KM IS NOT MUCH BETTER WITH SIMILAR VALUES. THUS THINKING
THAT IF THERE IS A SEVERE RISK...MORE LIKELY IT IS UP NORTH OF HWY
10 DURING THE LATE AFTERNOON/EVENING HOURS.
ON THE TEMPERATURE SIDE OF THINGS...925MB READINGS FROM THE
ECMWF/GFS ARE PROGGED TO CLIMB TO 24-26C LATE WEDNESDAY. WITH PLENTY
OF SUN MUCH OF THE DAY AND A SOUTHWEST BREEZE...HIGHS SHOULD TOP OUT
BETWEEN THE UPPER 80S AND MID 90S. DEWPOINTS MIXING DOWN INTO THE
MID TO UPPER 60S WILL HELP TO HOLD HEAT INDICES BELOW ADVISORY
CRITERIA. 925MB TEMPS COOLING TO 20-22C FOR THURSDAY LIKELY TO DROP
TEMPS 5-10 DEGREES FROM WEDNESDAY.
THURSDAY NIGHT THROUGH MONDAY...
INITIAL FOCUS FOR THIS TIME PERIOD IS THE RETURN BACK NORTH OF THE
COLD FRONT...I.E. SWITCHING TO A WARM FRONT...AND IF ANY CONVECTION
CAN FIRE ON THAT. THE 19.00Z ECMWF IS THE MOST BULLISH ON FIRING
CONVECTION FOR THURSDAY NIGHT AND FRIDAY AS THE FRONT LIFTS THROUGH
THE FORECAST AREA. 19.12Z GFS/CANADIAN ARE BOTH DRY.
NEXT CONCERN TURNS TO THE HEAT FOR THE WEEKEND INTO MONDAY AS THE
STRONG SUBTROPICAL RIDGE FORMS OVER NEBRASKA...IOWA...KANSAS AND
MISSOURI. THE BULK OF THE HEAT WITH 850MB TEMPS OF 24C OR HIGHER
LOOKS TO STAY WELL OFF TO THE WEST OVER THE DAKOTAS INTO WESTERN
PORTIONS OF NEBRASKA AND KANSAS. HOWEVER...THEY SHOULD STILL TOP OUT
IN THE 18-22C RANGE FOR SATURDAY THROUGH MONDAY...WITH THE HIGHER
READINGS OF 20-22C LIKELY OCCURRING SUNDAY AND MONDAY. THESE ARE
1.5-2 STANDARD DEVIATIONS ABOVE NORMAL...WHICH WOULD IMPLY CLOSE TO
BUT NOT REACHING OR EXCEEDING RECORD HIGHS. LOW TEMPERATURES COULD
TURN OUT QUITE WARM AS WELL WITH A PERSISTENT SOUTH TO SOUTHWEST
BREEZE. INDICATIONS FROM THE 19.12Z ECMWF THAT THE WELL ABOVE NORMAL
TEMPERATURES COULD STICK AROUND WELL BEYOND MONDAY.
PRECIPITATION CHANCES FOR THE WEEKEND INTO EARLY NEXT WEEK SHOULD
STAY CONFINED MOSTLY NORTH OF THE FORECAST AREA...WHERE THE WARM
FRONT FROM THURSDAY NIGHT/FRIDAY WILL BE LOCATED. THERE ARE
POSSIBILITIES THAT THE FRONT COULD SLIP BACK SOUTH INTO NORTHERN
SECTIONS OF THE FORECAST AREA AT TIMES SUNDAY NIGHT AND
MONDAY...THUS HAVE SOME CHANCES IN FOR THIS PERIOD.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1220 PM CDT MON AUG 19 2013
SHORT WAVE TROUGH MOVING SLOWLY ACROSS THE UPPER MIDWEST TODAY
CONTINUES TO PRODUCE A HIGH VFR CEILINGS OVER BOTH TAF SITES. RADAR
SUGGESTS SOME SPRINKLES FROM TIME TO TIME ARE POSSIBLE...BUT THIS
HAS BEEN TO THE NORTH. CANNOT TOTALLY RULE THESE OUT THROUGH THE
REMAINDER OF THE AFTERNOON AS BOTH THE 19.12Z NAM AND 19.15Z RAP
SHOW AN INCREASE IN THE LOW LEVEL MOISTURE TRANSPORT. DESPITE THIS
EXPECTED INCREASE IN THE MOISTURE TRANSPORT...FORECAST SOUNDINGS
CONTINUE TO SHOW QUITE A BIT OF DRY AIR IN THE LOW LEVELS SO WOULD
NOT EXPECT ANYTHING MORE THAN SPRINKLES. ONCE THIS WAVE MOVES
PAST...SKIES SHOULD CLEAR OUT THIS EVENING AND REMAIN THAT WAY
INTO TUESDAY MORNING. WITH HIGH PRESSURE REMAINING OVER THE OHIO
RIVER VALLEY AND A COLD FRONT SLOWLY APPROACHING FROM THE
NORTHWEST...ENOUGH OF A GRADIENT TO KEEP THE WINDS UP OVERNIGHT
WHICH SHOULD PRECLUDE THE FORMATION OF ANY VALLEY FOG.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM...AJ
AVIATION...04
FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE
.SHORT TERM...TONIGHT AND TUESDAY
ISSUED AT 227 PM CDT MON AUG 19 2013
LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A SHORTWAVE
TROUGH MOVING EAST OVER EASTERN MINNESOTA EARLY THIS AFTERNOON.
EARLIER SHOWERS AND STORMS OVER NORTHWEST WISCONSIN FIZZLED AND
THINGS REMAIN QUIET DESPITE DECENT MU CAPES OF OVER 1000 J/KG. WILL
LEAVE A SLIGHT CHANCE OF PRECIP FOR THE REST OF THE AFTERNOON OVER
N-C WISCONSIN THOUGH. CLOUD COVER HAS HELD BACK TEMPS
SOMEWHAT...AND ARE ONLY IN THE UPPER 70S ACROSS THE NORTH. LOOKING
FARTHER UPSTREAM...PLENTY OF CLEAR CONDITIONS OVER THE NORTHERN
PLAINS. SMALL PRECIP CHANCES AND TEMPS ARE THE MAIN FORECAST
CONCERNS IN THE SHORT-TERM.
TONIGHT...THE SHORTWAVE TROUGH MOVING OVER THE WESTERN GREAT LAKES
WILL SHEAR APART INTO TWO FEATURES. ONE WAVE WILL CONTINUE TO MOVE
EAST OVER SOUTHERN ONTARIO WHILE THE OTHER DIVES SOUTH ACROSS IOWA.
AS THIS OCCURS...BAND OF MID AND HIGH LEVEL MOISTURE WILL GET
STRETCHED AND DIMINISH...SO ANTICIPATE CLEARING SKIES TO OCCUR THIS
EVENING. THEN THE 850MB MOISTURE PLUME OVER THE CENTRAL AND
NORTHERN PLAINS EDGES EAST AND NOSES INTO WESTERN AND NORTHERN
WISCONSIN LATE TONIGHT. SCT TO WIDELY SCT CLOUDS ARE OCCURRING
WITHIN THIS MOISTURE PLUME AND BUFKIT SOUNDINGS AT RHI INDICATE
SKINNY CAPE UPWARDS OF 1000 J/KG DEVELOPING BY 09Z. WITH MOISTURE
TRANSPORT OCCURRING...CHANCES OF PRECIP ARE NOT NEGLIGIBLE...BUT
PLENTY OF DRY AIR EXISTS ABOVE 850MB AND MID-LEVEL LAPSE RATES ARE
RATHER POOR. WILL CONTINUE WITH THE DRY FORECAST. MUGGIER CONDITIONS
WITH LOWS IN THE UPPER 50S TO LOW 60S.
TUESDAY...LOW LEVEL MOISTURE PLUME WILL STRETCH FROM KANSAS TO
NORTHWEST WISCONSIN...PUSHING DEWPOINTS INTO THE MIDDLE 60S. WITH
TEMPS RISING INTO THE MID TO UPPER 80S...SHOULD SEE A DECENT CU
FIELD DEVELOP OVER CENTRAL AND NORTH-CENTRAL WISCONSIN. DESPITE
MID-LEVEL CAPPING...ML CAPES TOMORROW WILL REACH UPWARDS OF 2K J/KG
WITH NO CIN. NO TRIGGER ALOFT SO WILL GO WITH THE CONSENSUS WHICH
IS A DRY FORECAST.
.LONG TERM...TUESDAY NIGHT THROUGH MONDAY
ISSUED AT 227 PM CDT MON AUG 19 2013
FOCUS OF THIS PERIOD OF THE FORECAST WILL BE THE COLD FRONT
PASSAGE WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. THIS COLD FRONT
WILL BE SUPPORTED BY A SHORT WAVE TROUGH DROPPING INTO THE
NORTHERN GREAT LAKES REGION ALONG WITH A RRQ REGION OF THE UPPER
JET. INCREASING MOIST WARM UNSTABLE AIR MASS PRODUCING CAPES FROM
2500 TO 3000 J/KG FOR THE AFTERNOON HOURS AHEAD OF THE FRONT.
GOING HWO WILL CONTINUE TO HIGHLIGHT THE SVR THREAT. HEAT INDEX
NUMBERS ALSO CLIMB INTO THE LOWER 90S AHEAD OF THE FRONT ON
WEDNESDAY.
MEDIUM RANGE MODELS CONSISTENT WITH DRIVING THE FRONT SOUTH ON
THURSDAY FOR DRIER CONDITIONS AND MORE NORMAL TEMPERATURES.
PRECIPITATION TRENDS BECOME A CHALLENGE AGAIN LATER FRIDAY INTO
NEXT MONDAY. RETURN FLOW FRIDAY NIGHT INTO SATURDAY MAY PRODUCE A
PERIOD OF WAA CONVECTION...FOLLOWED BY PERIODS OF CONVECTION ON
THE NORTHERN PERIMETER OF THE BUILDING UPPER RIDGE LATER WEEKEND
INTO NEXT MONDAY. ORIENTATION OF THIS RIDGE WILL PLAY A ROLE WHERE
THE BEST CHANCE OF CONVECTION OCCURS. WITH THE BUILDING RIDGE
AGAIN THIS WEEKEND INTO NEXT WEEK...THE WARM AND MORE HUMID
AIR MASS WILL RETURN. HEAT INDEX NUMBERS LIKELY TO CLIMB BACK INTO
THE LOWER 90S EXCEPT FOR LOCATIONS ACROSS THE NORTH WHWERE
CONVECTION CAN DEVELOP.
&&
.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1202 PM CDT MON AUG 19 2013
MAINLY VFR CONDITIONS ACROSS THE REGION THROUGH THE TAF
PERIOD. WIDELY SCT SHOWERS AND THUNDERSTORMS ARE POSSIBLE THIS
AFTERNOON OVER NORTH-CENTRAL WISCONSIN. COVERAGE IS EXPECTED TO BE
LOW ENOUGH TO LEAVE OUT OF TAFS. PATCHY MVFR VSBYS IN MIST IS
POSSIBLE LATE TONIGHT. MOISTURE INCREASES FROM THE SOUTHERN PLAINS
TOMORROW...WHICH SHOULD LEAD TO BUILDING CLOUDS OVER THE COURSE OF
THE MORNING...MAINLY FOR CENTRAL AND NORTH-CENTRAL WISCONSIN.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......TDH
AVIATION.......MPC
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1220 PM CDT MON AUG 19 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 327 AM CDT MON AUG 19 2013
THE MAIN FOCUS FOR TODAY IS ON A MID LEVEL TROUGH THAT WILL COME
THROUGH AND WHETHER IT WILL HAVE ENOUGH LIFT TO OVERCOME THE DRY
LOW LEVEL AIR AND PRODUCE SOME RAIN SHOWERS.
THIS MID LEVEL TROUGH IS CURRENTLY ANALYZED VIA WATER VAPOR IR AND
19.06Z RAP 500MB ANALYSIS FROM SOUTHWESTERN ONTARIO THROUGH
MINNESOTA AND EASTERN NEBRASKA. SOME VERY HIGH BASED RADAR RETURNS
HAVE BEEN SHOWING UP ACROSS EASTERN SOUTH DAKOTA AND WESTERN
MINNESOTA THOUGH THERE HAVE NOT BEEN MANY SIGHTS REPORTING THAT
THE RAIN IS REACHING THE GROUND. THIS IS ALSO IN A BELT OF HIGHER
LOW LEVEL MOISTURE TRANSPORT THAT IS TRAPPED UNDER A 700MB
INVERSION...BUT IS HELPING TO RAISE SURFACE DEW POINTS. THIS IN
TURN HAS CREATED A MORE UNSTABLE AIR MASS FROM THE DAKOTAS UP INTO
NORTHERN MINNESOTA. THE 19.07Z RAP KEEPS MUCH OF THIS MOISTURE
TRANSPORT AND HIGHER INSTABILITY OUT TO THE WEST TODAY...SO THIS
TROUGH WILL BE ENTERING AN ENVIRONMENT THAT IS LESS FAVORABLE TO
SEE THE SHOWERS CONTINUE. CONSIDERED PUTTING IN A MENTION OF
SPRINKLES TODAY IN FOR SOUTHEAST MINNESOTA AND WESTERN TO NORTH
CENTRAL WISCONSIN...BUT HELD OFF FOR THE TIME BEING SINCE
REFLECTIVITIES OUT WEST APPEAR TO BE ON A WEAKENING TREND.
MID TO HIGH LEVEL CLOUD COVER WILL BE FAIRLY WIDESPREAD FOR A
PORTION OF THE DAY WHICH WILL KEEP TEMPERATURES DOWN A LITTLE BIT.
THE 19.00Z NAM/GFS SHOW SOME WARMER 850/925MB AIR MOVING IN THIS
AFTERNOON AS SOME OF THIS CLOUD COVER EXITS. EXPECT THAT WE WILL
WARM UP PRETTY QUICKLY AS THIS OCCURS...BUT PERHAPS NOT AS HIGH AS
PREVIOUSLY ADVERTISED.
.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 327 AM CDT MON AUG 19 2013
CONDITIONS WILL CONTINUE TO WARM INTO MID WEEK AHEAD OF A COLD
FRONT/TROUGH THAT WILL PROPAGATE INTO THE REGION ON WEDNESDAY.
WEDNESDAY IS EXPECTED TO BE THE WARMEST DAY OF THE WEEK WITH LOW
LEVEL WARM AIR ADVECTION BUMPING 925MB TEMPERATURES UP TO AROUND
26C AND 850MB TEMPERATURES TO 20C. THIS WARM LAYER SHOULD ALSO
HELP TO KEEP THE WARM SECTOR CAPPED OFF UNTIL THE COLD FRONT DROPS
DOWN LATE WEDNESDAY AFTERNOON AND EVENING. THE AIR MASS WILL
BECOME UNSTABLE WITH MODIFIED 19.00Z NAM/GFS SOUNDINGS...MODIFIED
FOR LOWER DEW POINTS IN THE MID/UPPER 60S...SHOWING BETWEEN
1500-2500 J/KG OF 0-3KM MUCAPE ALONG A NARROW CORRIDOR JUST AHEAD
OF THE FRONT. WIND SHEAR LOOKS MARGINAL WITH THE BETTER DEEP SHEAR
IN CENTRAL MINNESOTA/NORTHERN WISCONSIN WHERE 500MB WINDS WILL BE
AROUND 40KTS DUE TO THE MID LEVEL SHORT WAVE TROUGH DROPPING INTO
THE NORTHERN GREAT LAKES. FURTHER SOUTHWEST ALONG THE FRONT CLOSER
TO SOUTHERN MINNESOTA AND NORTHERN IOWA...19.00Z NAM/GFS
SOUNDINGS/HODOGRAPHS DO SHOW SOME DIRECTIONAL/SPEED SHEAR IN THE
LOWEST 2KM WHICH WOULD BE MORE FAVORABLE FOR STRONGER WINDS. BASED
ON THE INSTABILITY AND SHEAR...IT APPEARS THAT LARGE HAIL AND
DAMAGING WINDS STILL APPEAR TO BE THE MAIN THREATS IN THE LATE
AFTERNOON INTO THE EVENING...PARTICULARLY ACROSS SOUTHEAST
MINNESOTA...WESTERN WISCONSIN AND NORTHEAST IOWA.
THE ISSUE THEN CONTINUES TO BE WITH HOW FAR SOUTH WILL THE COLD
FRONT MAKE IT AND THEN HOW FAST DOES IT GET PUSHED BACK TO THE
NORTH AS A WARM FRONT BY THE END OF THE WEEK. THE ECMWF HAS
TRENDED TOWARD WHAT THE GFS/GEM HAVE BEEN ADVERTISING THE PAST FEW
DAYS WITH HAVING THE FRONT DROP SOUTH INTO IOWA/NORTHERN ILLINOIS
BY THURSDAY MORNING...BUT THE 19.00Z ECMWF STILL REMAINS THE
FURTHEST NORTH WITH WHERE IT STALLS OUT. THERE ALSO IS BETTER
CONTINUITY WITH THE NEXT TROUGH TRACKING ACROSS THE NORTHERN
PLAINS ON FRIDAY INTO SATURDAY WHICH IS WHEN THE FRONT COMES BACK
NORTH AS A WARM FRONT.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1220 PM CDT MON AUG 19 2013
SHORT WAVE TROUGH MOVING SLOWLY ACROSS THE UPPER MIDWEST TODAY
CONTINUES TO PRODUCE A HIGH VFR CEILINGS OVER BOTH TAF SITES. RADAR
SUGGESTS SOME SPRINKLES FROM TIME TO TIME ARE POSSIBLE...BUT THIS
HAS BEEN TO THE NORTH. CANNOT TOTALLY RULE THESE OUT THROUGH THE
REMAINDER OF THE AFTERNOON AS BOTH THE 19.12Z NAM AND 19.15Z RAP
SHOW AN INCREASE IN THE LOW LEVEL MOISTURE TRANSPORT. DESPITE THIS
EXPECTED INCREASE IN THE MOISTURE TRANSPORT...FORECAST SOUNDINGS
CONTINUE TO SHOW QUITE A BIT OF DRY AIR IN THE LOW LEVELS SO WOULD
NOT EXPECT ANYTHING MORE THAN SPRINKLES. ONCE THIS WAVE MOVES
PAST...SKIES SHOULD CLEAR OUT THIS EVENING AND REMAIN THAT WAY
INTO TUESDAY MORNING. WITH HIGH PRESSURE REMAINING OVER THE OHIO
RIVER VALLEY AND A COLD FRONT SLOWLY APPROACHING FROM THE
NORTHWEST...ENOUGH OF A GRADIENT TO KEEP THE WINDS UP OVERNIGHT
WHICH SHOULD PRECLUDE THE FORMATION OF ANY VALLEY FOG.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...HALBACH
LONG TERM...HALBACH
AVIATION...04
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
641 AM CDT MON AUG 19 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 327 AM CDT MON AUG 19 2013
THE MAIN FOCUS FOR TODAY IS ON A MID LEVEL TROUGH THAT WILL COME
THROUGH AND WHETHER IT WILL HAVE ENOUGH LIFT TO OVERCOME THE DRY
LOW LEVEL AIR AND PRODUCE SOME RAIN SHOWERS.
THIS MID LEVEL TROUGH IS CURRENTLY ANALYZED VIA WATER VAPOR IR AND
19.06Z RAP 500MB ANALYSIS FROM SOUTHWESTERN ONTARIO THROUGH
MINNESOTA AND EASTERN NEBRASKA. SOME VERY HIGH BASED RADAR RETURNS
HAVE BEEN SHOWING UP ACROSS EASTERN SOUTH DAKOTA AND WESTERN
MINNESOTA THOUGH THERE HAVE NOT BEEN MANY SIGHTS REPORTING THAT
THE RAIN IS REACHING THE GROUND. THIS IS ALSO IN A BELT OF HIGHER
LOW LEVEL MOISTURE TRANSPORT THAT IS TRAPPED UNDER A 700MB
INVERSION...BUT IS HELPING TO RAISE SURFACE DEW POINTS. THIS IN
TURN HAS CREATED A MORE UNSTABLE AIR MASS FROM THE DAKOTAS UP INTO
NORTHERN MINNESOTA. THE 19.07Z RAP KEEPS MUCH OF THIS MOISTURE
TRANSPORT AND HIGHER INSTABILITY OUT TO THE WEST TODAY...SO THIS
TROUGH WILL BE ENTERING AN ENVIRONMENT THAT IS LESS FAVORABLE TO
SEE THE SHOWERS CONTINUE. CONSIDERED PUTTING IN A MENTION OF
SPRINKLES TODAY IN FOR SOUTHEAST MINNESOTA AND WESTERN TO NORTH
CENTRAL WISCONSIN...BUT HELD OFF FOR THE TIME BEING SINCE
REFLECTIVITIES OUT WEST APPEAR TO BE ON A WEAKENING TREND.
MID TO HIGH LEVEL CLOUD COVER WILL BE FAIRLY WIDESPREAD FOR A
PORTION OF THE DAY WHICH WILL KEEP TEMPERATURES DOWN A LITTLE BIT.
THE 19.00Z NAM/GFS SHOW SOME WARMER 850/925MB AIR MOVING IN THIS
AFTERNOON AS SOME OF THIS CLOUD COVER EXITS. EXPECT THAT WE WILL
WARM UP PRETTY QUICKLY AS THIS OCCURS...BUT PERHAPS NOT AS HIGH AS
PREVIOUSLY ADVERTISED.
.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 327 AM CDT MON AUG 19 2013
CONDITIONS WILL CONTINUE TO WARM INTO MID WEEK AHEAD OF A COLD
FRONT/TROUGH THAT WILL PROPAGATE INTO THE REGION ON WEDNESDAY.
WEDNESDAY IS EXPECTED TO BE THE WARMEST DAY OF THE WEEK WITH LOW
LEVEL WARM AIR ADVECTION BUMPING 925MB TEMPERATURES UP TO AROUND
26C AND 850MB TEMPERATURES TO 20C. THIS WARM LAYER SHOULD ALSO
HELP TO KEEP THE WARM SECTOR CAPPED OFF UNTIL THE COLD FRONT DROPS
DOWN LATE WEDNESDAY AFTERNOON AND EVENING. THE AIR MASS WILL
BECOME UNSTABLE WITH MODIFIED 19.00Z NAM/GFS SOUNDINGS...MODIFIED
FOR LOWER DEW POINTS IN THE MID/UPPER 60S...SHOWING BETWEEN
1500-2500 J/KG OF 0-3KM MUCAPE ALONG A NARROW CORRIDOR JUST AHEAD
OF THE FRONT. WIND SHEAR LOOKS MARGINAL WITH THE BETTER DEEP SHEAR
IN CENTRAL MINNESOTA/NORTHERN WISCONSIN WHERE 500MB WINDS WILL BE
AROUND 40KTS DUE TO THE MID LEVEL SHORT WAVE TROUGH DROPPING INTO
THE NORTHERN GREAT LAKES. FURTHER SOUTHWEST ALONG THE FRONT CLOSER
TO SOUTHERN MINNESOTA AND NORTHERN IOWA...19.00Z NAM/GFS
SOUNDINGS/HODOGRAPHS DO SHOW SOME DIRECTIONAL/SPEED SHEAR IN THE
LOWEST 2KM WHICH WOULD BE MORE FAVORABLE FOR STRONGER WINDS. BASED
ON THE INSTABILITY AND SHEAR...IT APPEARS THAT LARGE HAIL AND
DAMAGING WINDS STILL APPEAR TO BE THE MAIN THREATS IN THE LATE
AFTERNOON INTO THE EVENING...PARTICULARLY ACROSS SOUTHEAST
MINNESOTA...WESTERN WISCONSIN AND NORTHEAST IOWA.
THE ISSUE THEN CONTINUES TO BE WITH HOW FAR SOUTH WILL THE COLD
FRONT MAKE IT AND THEN HOW FAST DOES IT GET PUSHED BACK TO THE
NORTH AS A WARM FRONT BY THE END OF THE WEEK. THE ECMWF HAS
TRENDED TOWARD WHAT THE GFS/GEM HAVE BEEN ADVERTISING THE PAST FEW
DAYS WITH HAVING THE FRONT DROP SOUTH INTO IOWA/NORTHERN ILLINOIS
BY THURSDAY MORNING...BUT THE 19.00Z ECMWF STILL REMAINS THE
FURTHEST NORTH WITH WHERE IT STALLS OUT. THERE ALSO IS BETTER
CONTINUITY WITH THE NEXT TROUGH TRACKING ACROSS THE NORTHERN
PLAINS ON FRIDAY INTO SATURDAY WHICH IS WHEN THE FRONT COMES BACK
NORTH AS A WARM FRONT.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 641 AM CDT MON AUG 19 2013
MVFR CONDITIONS ARE EXPECTED AT KLSE THROUGH 14Z THIS
MORNING. OTHERWISE...VFR CONDITIONS ARE EXPECTED AT THE TAF SITES
THROUGH THE FORECAST PERIOD. PATCHY FOG HAS DEVELOPED ALONG THE
MISSISSIPPI RIVER THIS MORNING. PLAN ON VISIBILITIES BEING REDUCED
TO AROUND 4SM AT KLSE BEFORE THE FOG FINALLY DISSIPATES AROUND
14Z. A WEAK UPPER LEVEL DISTURBANCE WILL MOVE ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY TODAY BRINGING SCATTERED TO BROKEN VFR
CEILINGS. ALSO...SOUTHWEST WINDS WILL INCREASES TO AROUND 10KTS
WITH GUSTS AROUND 20 KTS POSSIBLE THIS AFTERNOON. THE WINDS WILL
SUBSIDE INTO THE 5 TO 7 KT RANGE TONIGHT.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...HALBACH
LONG TERM...HALBACH
AVIATION...WETENKAMP
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
327 AM CDT MON AUG 19 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 327 AM CDT MON AUG 19 2013
THE MAIN FOCUS FOR TODAY IS ON A MID LEVEL TROUGH THAT WILL COME
THROUGH AND WHETHER IT WILL HAVE ENOUGH LIFT TO OVERCOME THE DRY
LOW LEVEL AIR AND PRODUCE SOME RAIN SHOWERS.
THIS MID LEVEL TROUGH IS CURRENTLY ANALYZED VIA WATER VAPOR IR AND
19.06Z RAP 500MB ANALYSIS FROM SOUTHWESTERN ONTARIO THROUGH
MINNESOTA AND EASTERN NEBRASKA. SOME VERY HIGH BASED RADAR RETURNS
HAVE BEEN SHOWING UP ACROSS EASTERN SOUTH DAKOTA AND WESTERN
MINNESOTA THOUGH THERE HAVE NOT BEEN MANY SIGHTS REPORTING THAT
THE RAIN IS REACHING THE GROUND. THIS IS ALSO IN A BELT OF HIGHER
LOW LEVEL MOISTURE TRANSPORT THAT IS TRAPPED UNDER A 700MB
INVERSION...BUT IS HELPING TO RAISE SURFACE DEW POINTS. THIS IN
TURN HAS CREATED A MORE UNSTABLE AIR MASS FROM THE DAKOTAS UP INTO
NORTHERN MINNESOTA. THE 19.07Z RAP KEEPS MUCH OF THIS MOISTURE
TRANSPORT AND HIGHER INSTABILITY OUT TO THE WEST TODAY...SO THIS
TROUGH WILL BE ENTERING AN ENVIRONMENT THAT IS LESS FAVORABLE TO
SEE THE SHOWERS CONTINUE. CONSIDERED PUTTING IN A MENTION OF
SPRINKLES TODAY IN FOR SOUTHEAST MINNESOTA AND WESTERN TO NORTH
CENTRAL WISCONSIN...BUT HELD OFF FOR THE TIME BEING SINCE
REFLECTIVITIES OUT WEST APPEAR TO BE ON A WEAKENING TREND.
MID TO HIGH LEVEL CLOUD COVER WILL BE FAIRLY WIDESPREAD FOR A
PORTION OF THE DAY WHICH WILL KEEP TEMPERATURES DOWN A LITTLE BIT.
THE 19.00Z NAM/GFS SHOW SOME WARMER 850/925MB AIR MOVING IN THIS
AFTERNOON AS SOME OF THIS CLOUD COVER EXITS. EXPECT THAT WE WILL
WARM UP PRETTY QUICKLY AS THIS OCCURS...BUT PERHAPS NOT AS HIGH AS
PREVIOUSLY ADVERTISED.
.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 327 AM CDT MON AUG 19 2013
CONDITIONS WILL CONTINUE TO WARM INTO MID WEEK AHEAD OF A COLD
FRONT/TROUGH THAT WILL PROPAGATE INTO THE REGION ON WEDNESDAY.
WEDNESDAY IS EXPECTED TO BE THE WARMEST DAY OF THE WEEK WITH LOW
LEVEL WARM AIR ADVECTION BUMPING 925MB TEMPERATURES UP TO AROUND
26C AND 850MB TEMPERATURES TO 20C. THIS WARM LAYER SHOULD ALSO
HELP TO KEEP THE WARM SECTOR CAPPED OFF UNTIL THE COLD FRONT DROPS
DOWN LATE WEDNESDAY AFTERNOON AND EVENING. THE AIR MASS WILL
BECOME UNSTABLE WITH MODIFIED 19.00Z NAM/GFS SOUNDINGS...MODIFIED
FOR LOWER DEW POINTS IN THE MID/UPPER 60S...SHOWING BETWEEN
1500-2500 J/KG OF 0-3KM MUCAPE ALONG A NARROW CORRIDOR JUST AHEAD
OF THE FRONT. WIND SHEAR LOOKS MARGINAL WITH THE BETTER DEEP SHEAR
IN CENTRAL MINNESOTA/NORTHERN WISCONSIN WHERE 500MB WINDS WILL BE
AROUND 40KTS DUE TO THE MID LEVEL SHORT WAVE TROUGH DROPPING INTO
THE NORTHERN GREAT LAKES. FURTHER SOUTHWEST ALONG THE FRONT CLOSER
TO SOUTHERN MINNESOTA AND NORTHERN IOWA...19.00Z NAM/GFS
SOUNDINGS/HODOGRAPHS DO SHOW SOME DIRECTIONAL/SPEED SHEAR IN THE
LOWEST 2KM WHICH WOULD BE MORE FAVORABLE FOR STRONGER WINDS. BASED
ON THE INSTABILITY AND SHEAR...IT APPEARS THAT LARGE HAIL AND
DAMAGING WINDS STILL APPEAR TO BE THE MAIN THREATS IN THE LATE
AFTERNOON INTO THE EVENING...PARTICULARLY ACROSS SOUTHEAST
MINNESOTA...WESTERN WISCONSIN AND NORTHEAST IOWA.
THE ISSUE THEN CONTINUES TO BE WITH HOW FAR SOUTH WILL THE COLD
FRONT MAKE IT AND THEN HOW FAST DOES IT GET PUSHED BACK TO THE
NORTH AS A WARM FRONT BY THE END OF THE WEEK. THE ECMWF HAS
TRENDED TOWARD WHAT THE GFS/GEM HAVE BEEN ADVERTISING THE PAST FEW
DAYS WITH HAVING THE FRONT DROP SOUTH INTO IOWA/NORTHERN ILLINOIS
BY THURSDAY MORNING...BUT THE 19.00Z ECMWF STILL REMAINS THE
FURTHEST NORTH WITH WHERE IT STALLS OUT. THERE ALSO IS BETTER
CONTINUITY WITH THE NEXT TROUGH TRACKING ACROSS THE NORTHERN
PLAINS ON FRIDAY INTO SATURDAY WHICH IS WHEN THE FRONT COMES BACK
NORTH AS A WARM FRONT.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1100 PM CDT SUN AUG 18 2013
A TIGHTENING PRESSURE GRADIENT IN PLACE THIS MORNING WILL HELP TO
PRODUCE A DEEPER AND STRONGER LAYER OF WINDS...WITH SPEEDS OF
10-20 KTS FROM JUST RIGHT ABOVE THE SURFACE TO 5000 FT. THESE
WINDS COMBINED WITH SOME PASSING CIRRUS SHOULD HELP KEEP RIVER
VALLEY FOG TO A MINIMUM. HOWEVER...HAVE LEFT THE MVFR VISIBILITIES
AND THE POTENTIAL FOR A SCATTERED 400 FT STRATUS DECK TO DEVELOP
ALONG THE CHANNEL. IF WINDS DO NOT INCREASE AS FORECAST...
VISIBILITIES AND CEILINGS COULD END UP A LOT LOWER. OTHERWISE...
SCATTERED TO BROKEN HIGH LEVEL CLOUDS ASSOCIATED WITH A PASSING
WEATHER SYSTEM TO THE NORTH WILL SPILL OVER THE TAF SITES.
AFTERNOON CUMULUS WITH BASES BETWEEN 4 AND 5 KFT LIKELY AS WELL.
MODEL SOUNDINGS SHOW MORE MIXING...ESPECIALLY ACROSS THE OPEN
AREAS OF MINNESOTA...RESULTING IN THE NEED FOR GUSTS AT KRST FOR
THE AFTERNOON. PLAN ON WINDS TO DIMINISH IN THE EVENING WITH LOSS
OF HEATING...ALONG WITH CLEARING SKIES.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...HALBACH
LONG TERM...HALBACH
AVIATION...ZT/AJ
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
1128 PM CDT SUN AUG 18 2013
UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE
.SHORT TERM...TONIGHT AND MONDAY
ISSUED AT 256 PM CDT SUN AUG 18 2013
LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW HIGH PRESSURE
CENTERED OVER THE NE U.S...BUT WITH A RIDGE AXIS THAT EXTENDS WEST
INTO THE GREAT LAKES. THE MAIN STORM TRACK REMAINS NORTH OF THE
REGION OVER SOUTHERN CANADA...BUT IS GRADUALLY SINKING TO THE
SOUTH. AS THIS OCCURS...A SHORTWAVE OVER EASTERN MONTANA IS MOVING
EAST AND PRODUCING THUNDERSTORMS...WHICH WILL TRACK TOWARDS THE
REGION TOMORROW. BESIDES TEMPERATURES...SMALL THUNDERSTORM CHANCES
REMAIN THE MAIN FORECAST CONCERNS.
TONIGHT...THE SHORTWAVE TROUGH OVER EASTERN MONTANA WILL MOVE EAST
INTO THE NORTHERN MISSISSIPPI VALLEY BY 12Z MONDAY. THE 850MB
MOISTURE AND INSTABILITY AXES WILL SHIFT INTO NORTHEAST MINNESOTA BY
THIS TIME...WHICH LOOKS TOO FAR WEST FOR MUCH OF AN IMPACT ON THE
FORECAST AREA. OTHERWISE...SCATTERED HIGH CLOUDS WILL BE PASSING
OVERHEAD FOR MUCH OF NIGHT...AND THEN SEE THE HIGH CLOUDS THICKEN
AND LOWER A BIT LATE AS THE SHORTWAVE DRAWS CLOSER. THE PRESSURE
GRADIENT WILL BE TIGHTENING TONIGHT...WHICH SHOULD ALLOW A LIGHT SW
WIND TO PERSIST AND KEEP ANY FOG FROM FORMING. LOWS WILL CONTINUE
THEIR WARMING TREND...AND RESIDE IN THE 50S.
MONDAY...THE SHORTWAVE TROUGH WILL MOVE INTO WISCONSIN. FORCING
WITH THE WAVE APPEARS TO SUBTLY WEAKEN...SO WILL LIKELY NEED THE
HELP OF DIURNAL INSTABILITY TO GET CONVECTION GOING. THE MOISTURE
AXIS WILL BE SNEAKING INTO NORTH-CENTRAL WISCONSIN IN THE
AFTERNOON...BUT PROGGED NAM SOUNDINGS AT 21Z NEAR EAGLE RIVER SHOW
DECENT CAPPING CENTERED AT ABOUT 800 MB. USING A PARCEL OF
82/62...ML CAPES WILL REACH AROUND 1000 J/KG...WHILE CINS REMAIN A
ROBUST 70-80 J/KG. UNLESS THE CAP IS ADVERTISED TOO
STRONGLY...CANNOT SEE MORE THAN ISOLATED STORM DEVELOPMENT GIVEN THE
WEAK FORCING. IF STORMS DO DEVELOP...WEAK SHEAR ALOFT WILL KEEP THE
SEVERE THREAT RATHER LOW. MADE ONLY MINOR TWEAKS TO TIMING AND
COVERAGE OF POPS. DESPITE AN INCREASE IN CLOUD COVER...LOW LEVEL
TEMPS WILL ALSO BE WARMING...AND PUSH HIGHS INTO THE MIDDLE 80S.
.LONG TERM...MONDAY NIGHT THROUGH SUNDAY
ISSUED AT 256 PM CDT SUN AUG 18 2013
TUESDAY THROUGH NEXT WEEKEND WILL BE HIGHLIGHTED WITH ABOVE
NORMAL TEMPERATURES. THE NEXT MAIN CHANCE FOR WIDESPREAD
PRECIPITATION WILL BE STARTING WEDNESDAY AFTERNOON OVER NORTHWEST
WISCONSIN THEN OVER THE REST OF THE STATE WEDNESDAY NIGHT INTO
THURSDAY WITH THE PASSAGE OF A COLD FRONT.
THERE IS A SMALLER CHANCE OF CONVECTION ON TUESDAY OVER THE
NORTHWEST HALF OF THE STATE DUE TO CONTINUED WAA...AND IN A REGION
OF UPPER DIVERGENCE AHEAD OF THE WESTERLIES OVER THE NORTHERN
PLAINS. CONVECTION MAY BE CONFINED TOWARD WESTERN PORTION OF THE
STATE BUT WILL LEAVE PARTS OF NC WI WITH SMALL CHANCE DUE TO TOTAL
TOTALS INCREASE IN THE AFTERNOON.
THE WESTERLY FLOW OVER THE NORTHERN PLAINS BEGINS TO BUCKLE
WEDNESDAY AS A SHORT WAVE TROUGH DEVELOPS OVER SOUTHERN CANADA
AND A COLD FRONT SAGS INTO THE NORTHERN GREAT LAKES REGION
INCLUDING NORTHWEST WISCONSIN. MEDIUM RANGE MODELS ARE IN GOOD
AGREEMENT WITH THE TIMING OFF THIS FRONT AND CONVECTION UNTIL
WEDNESDAY NIGHT FOR MOST LOCATIONS EXCEPT NORTH CENTRAL WISCONSIN.
SEVERE POTENTIAL REMAINS FOR WEDNESDAY AFTERNOON INTO WEDNESDAY
NIGHT. TOTAL TOTALS CLIMB INTO THE LOWER 50S WITH THE FRONT WHILE
PWATS INCREASE TO NEAR 2.00
GFS...GEM DROP THE CONVECTION AND FRONT WELL SOUTH ON THURSDAY
FOR A DRIER TREND WHICH COULD LAST INTO FRIDAY. BUT THE ECMWF
SLOWS THIS FRONT DOWN WHILE A HIGH PRESSURE SYSTEM DRIFTS OVER
THE NORTHERN GREAT LAKES REGION THURSDAY THROUGH FRIDAY.
THE UPPER RIDGE CONTINUES TO BUILD INTO THE WEEKEND FOR MORE HEAT
ALONG WITH CHANCES OF CONVECTION ON THE PERIPHERY OF THE RIDGE OR
MAINLY THE NORTHERN GREAT LAKES REGION.
&&
.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1125 PM CDT SUN AUG 18 2013
VFR CONDITIONS EXPECTED AS ANTICYCLONE SLOWLY SHIFTS SE OF THE
AREA. SHOULD SEE A LITTLE MORE GUSTINESS IN THE WINDS TOMORROW AS
FAIRLY DEEP MIXING IS EXPECTED TO OCCUR. CAN/T RULE OUT A SHRA/TSRA
ACRS THE N TOMORROW AFTN...BUT SUPPORT IS VERY LIMITED SO WL KEEP
THE TAFS DRY.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......TDH
AVIATION.......SKOWRONSKI
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
131 AM EDT WED AUG 21 2013
.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 416 PM EDT TUE AUG 20 2013
WV IMAGERY AND RUC ANALYSIS INDICATED A MAINLY ZONAL MID/UPPER LEVEL
FLOW ACROSS SRN CANADA AND THE NRN CONUS ATOP RIDING OVER THE PLAINS
AND A CUTOFF LOW NEAR KSTL. THE MAIN UPSTREAM SHORTWAVE TROUGH WAS
LOCATED WELL UPSTREAM...FROM SASK INTO ERN ALBERTA. AT THE SFC...SW
FLOW PREVAILED THROUGH THE WRN GREAT LAKES BTWN HIGH PRES OVER THE
ERN OH VALLEY AND A TROUGH FROM NW ONTARIO INTO CNTRL ND. A COLD
FRONT EXTENDED FROM NEAR WINNIPEG INTO SRN SASK. ALTHOUGH VIS LOOP
SHOWED ABUNDANT CU ACROSS THE REGION AND A LAKE BREEZE BOUNDARY OFF
OF LAKE MI...CAPPING EVIDENT ON AREA SOUNDINGS WITH 800-700 MB TEMPS
AROUND 13C HAS SUPPRESSED ANY CONVECTION THAT WOULD PRODUCE ANY
SHRA/TSRA.
TONIGHT...AS THE ALBERTA/SASK MOVES INTO MANITOBA AND THE PLAINS
TROUGH SLIDES TO THE EAST THE STRONGEST LOW LEVEL MOISTURE
ADVECTION...FOCUS OF THE LOW LEVEL JET...AND 310K ISENTROPIC LIFT
THROUGH THE 850-700 MB FRONT WILL REMAIN JUST NORTH OF LAKE SUPERIOR
BUT MAY BRUSH THE NRN PORTION OF THE LAKE. OTHERWISE...THE PERSISTENT
SW FLOW THROUGH THE WRN LAKES WILL KEEP TEMPS WELL ABOVE
NORMAL...ESPECIALLY FOR DOWNSLOPE LOCATIONS NEAR LAKE SUPERIOR. MIN
READINGS IN THE MID 60S TO LOWER 70S...NEAR THE HIGHER END OF
GUIDANCE ARE EXPECTED.
WED...AS THE SHRTWV MOVES THROUGH NRN ONTARIO IT WILL DRAG THE COLD
FRONT THROUGH LAKE SUPERIOR AND UPPER MI. THE COMBINATION OF LOW
LEVEL CONV ALONG THE FRONT...REINFORCED BY THE LAKE SUPERIOR
BREEZE...AND WEAK TO MODERATE MID LEVEL QVECTOR CONV WITH THE TAIL
OF THE SHRTWV SHOULD TRIGGER TSRA OVER WEST UPPER MI IN THE EARLY
AFTERNOON WHICH WILL SPREAD INTO THE CNTRL CWA BY MID AND LATE
AFTERNOON. DEWPOINTS INTO THE UPPER 60S AND TEMPS IN THE UPPER 80S
WILL RESULT IN MLCAPE VALUES INTO THE 2K-3K J/KG RANGE. THE STRONG
INSTABILITY(BY U.P. STANDARDS) ALONG WITH 0-6KM SHEAR TO AROUND 30
KT WILL BE ENOUGH TO SUPPORT MULTICELL CLUSTERS WITH SOME SEVERE
THUNDERSTORMS. WITH DCAPE VALUES OF 1K J/KG...DAMAGING WINDS WILL BE
THE MAIN THREAT. SOME ISOLATED LARGE HAIL MAY ALSO BE POSSIBLE WITH
THE STRONGEST STORMS.
.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 416 PM EDT TUE AUG 20 2013
COLD FRONT AND ASSOCIATED SHOWERS/THUNDERSTORMS WILL BE MOVING
SOUTHEAST ACROSS CENTRAL AND EASTERN UPPER MICHIGAN AT THE
START OF THE LONG TERM PERIOD. EXPECT THESE STRONG TO POTENTIALLY
SEVERE THUNDERSTORMS TO BE SLIDING EAST-SOUTHEAST ACROSS THOSE AREAS
DURING THE EVENING HOURS AND BE MOVING INTO LAKE MICHIGAN TOWARDS
MIDNIGHT OR THE EARLY OVERNIGHT HOURS. 12Z MODELS TODAY SEEM TO BE
A LITTLE SLOWER WITH THE FRONTAL PASSAGE THAN YESTERDAY...SO WILL
FOLLOW THE IDEA OF THE MID SHIFT WITH THE TIMING.
A SHORTWAVE DIVING SOUTHEAST FROM LAKE WINNIPEG WEDNESDAY NIGHT
WILL CROSS THE U.P. ON THURSDAY MORNING. WITH THE DRY AIR AND
HIGH PRESSURE THAT ARRIVES BEHIND THE COLD FRONT...SHOULDN/T SEE
MUCH INFLUENCE FROM THE SHORTWAVE ON THE WEATHER AND EXPECT MOSTLY
SUNNY SKIES. HIGHS THURSDAY WILL BE MUCH COOLER (BY 10-15
DEGREES) THAN WEDNESDAY WITH THE NORTHERLY WINDS OFF LAKE SUPERIOR.
FORTUNATELY...MOST AREAS WILL SEE RAIN TOMORROW...OTHERWISE THERE
COULD BE AN ELEVATED FIRE WX RISK WITH NORTH WINDS OF 10-20MPH AND
RH VALUES FALLING TOWARDS 30 PERCENT.
ANOTHER SHORTWAVE ROUNDING THE UPPER RIDGE IN CENTRAL CANADA WILL
DIVE SOUTHEAST ACROSS THE EASTERN CWA ON FRIDAY. AT THIS
TIME...WOULD EXPECT SOME INCREASE IN CLOUD COVER BASED OFF
925-850MB MOISTURE AND DIURNAL HEATING OVER THE EASTERN PART OF THE
CWA (MAINLY FROM MARQUETTE/DICKINSON COUNTIES AND EAST). WON/T GO
TOO HIGH ON CLOUD COVER...BUT AT LEAST GIVE A PERIOD OF PARTLY
CLOUDY SKIES OVER THE EAST AS THAT MOISTURE MOVES THROUGH.
UPPER RIDGE THAT WAS OVER THE NORTHERN PLAINS AND CENTRAL CANADA
WILL THEN SHIFT EAST ON FRIDAY NIGHT WITH THE AXIS OF THE RIDGE
OVER UPPER MICHIGAN BY 12Z SATURDAY. THIS MOVEMENT OF THE RIDGE
WILL ALSO SLIDE THE SURFACE HIGH EAST OF THE AREA AND ALLOW
SOUTHERLY FLOW AND GRADUALLY WARMING TEMPERATURES TO RETURN. MODELS
ARE STILL STRUGGLING TO COME UP WITH A CONSENSUS ON THE SERIES OF
SHORTWAVES MOVING INTO THE UPPER RIDGE AND GRADUALLY BREAKING IT
DOWN FROM SATURDAY AFTERNOON THROUGH THE FIRST HALF OF NEXT WEEK.
THE FIRST WAVE WILL MOVE THROUGH THE AREA SATURDAY AFTERNOON AND
NIGHT (OVER THE NORTH HALF OF THE CWA) AND THE NEXT ONE LATE SUNDAY
AFTERNOON INTO MONDAY MORNING. THE DISCREPANCIES GROW FURTHER ON
MONDAY NIGHT INTO TUESDAY...WITH GFS BRINGING ANOTHER SHORTWAVE
THROUGH ON TUESDAY WHILE THE ECMWF/GEM HAS HIGH PRESSURE OVER THE
AREA. THESE PERIODS OF SHOWERS/THUNDERSTORMS ALSO LEADS TO
UNCERTAINTY WITH HIGHS BUT SHOULD AT LEAST BE ABOVE NORMAL.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 130 AM EDT WED AUG 21 2013
EXPECT VFR CONDITIONS AT ALL 3 TAF SITES DESPITE THE CHANCE FOR
SHRA/TSRA WED AFTERNOON/EVENING WITH THE PASSAGE OF A COLD FRONT.
LLWS SHOULD CONTINUE OVERNIGHT WITH STRENGTHENING NOCTURNAL SW LOW
LEVEL JET UNDER A SHARPENING PRES GRADIENT AHEAD OF APPROACHING COLD
FRONT. EXPECT SHRA AND POSSIBLE TSRA EARLY WED AFTERNOON AT KIWD AND
KCMX WITH A BETTER CHANCE LATE WED AFTERNOON/EARLY EVENING AT KSAW
WITH THE FRONTAL PASSAGE.
&&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 416 PM EDT TUE AUG 20 2013
OVERALL...EXPECT WINDS LESS THAN 20KT THRU THE PERIOD AS A
RELATIVELY WEAK PRES GRADIENT TYPICAL OF SUMMER PERSISTS OVER THE
GREAT LAKES REGION. ONE PERIOD OF STRONGER WINDS (GUSTS TO 20-25KT)
MAY OCCUR TONIGHT AS THE PRES GRADIENT TIGHTENS AHEAD OF THE
APPROACHING COLD FRONT...BUT HIGH OVERWATER STABILITY WITH INFLUX
OF A VERY WARM AIRMASS WILL LIMIT THE INCREASE OF WIND SPEED NEAR THE
COOLER LAKE SURFACE. THE ARRIVAL OF MORE HUMID AIR MAY RESULT IN
SOME FOG FORMATION OVER THE COOLER LAKE WATERS...BUT RESTRICTED THE
FOG FORECAST TO AREAS WHERE SOME SHOWERS OR THUNDERSTORMS ARE
EXPECTED. ANY FOG WILL DISSIPATE WED AFTN AND EVENING FOLLOWING A
COLD FRONTAL PASSAGE AND THE ARRIVAL OF DRIER AIR.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...JLB
LONG TERM...SRF
AVIATION...VOSS
MARINE...JLB
AREA FORECAST DISCUSSION
NWS NORTH PLATTE NE
331 AM CDT WED AUG 21 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM CDT WED AUG 21 2013
SATELLITE AND LIGHTNING SUGGEST A DISTURBANCE ACROSS NERN UT/NWRN
COLO THIS MORNING. THIS DISTURBANCE SHOULD FIRE OFF THE LARAMIE
RANGE AROUND 18Z MARKING THE START OF CONVECTION LATER THIS
AFTERNOON ACROSS WRN AND EVENTUALLY NCNTL NEB TONIGHT. THE RAP
MODEL SHOWS A TSTM COMPLEX DEVELOPING OFF THE PINE RIDGE AROUND
19Z AND THE HRRR IS VERY BUSY ACROSS THE NEB PANHANDLE AT 20Z. IT
ALSO INDICATES STORM INTENSIFICATION ACROSS HOLT COUNTY IN THE
DEEP MOISTURE SECTOR.
GIVEN THAT THE MODELS ARE SHOWING PRECIPITABLE WATER INCREASING
TO AROUND 1.75 INCHES EAST OF HIGHWAY 83 TONIGHT AND THAT WEAK
WINDS ALOFT WILL PRODUCE STORM MOTION OF 10 KTS OR LESS...LOCALLY
HEAVY RAIN SHOULD DEVELOP IN THIS AREA OF RICH MOISTURE.
ELSEWHERE STORM ACTIVITY SHOULD BE SCATTERED OR LESS. NOTE THAT A
MIDLEVEL COLD FRONT IS OPERATING THIS MORNING ACROSS NRN NEB
WHICH WOULD ACTIVATE SCATTERED CONVECTION EARLY THIS AFTERNOON IN
RESPONSE TO DAYTIME HEATING. A STATIONARY FRONT...CURRENTLY
ACROSS SRN SD SHOULD DRIFT SOUTH INTO NRN NEB AT THE SAME TIME
WITH LOW LEVEL MOISTURE POOLING ALONG THE FRONT ADDING FOCUS TO
THE RAIN EVENT.
WINDS ALOFT ARE WEAK AT 35 KTS OR LESS WHICH WILL LIMIT SEVERE
WEATHER POTENTIAL TO ISOLATED COVERAGE. SCATTERED LIGHT SHOWERS
SHOULD CONTINUE THIS MORNING ALONG THE MID LEVEL FRONT ACROSS NRN
NEB WHICH WOULD THEN INTENSIFY TO THUNDERSTORMS EARLY THIS
AFTERNOON AND PERHAPS APPROACH SEVERE LIMITS LATE THIS AFTERNOON
AS THE DISTURBANCE APPROACHES.
MOISTURE TRANSPORT VECTORS ARE RELATIVELY WEAK THIS AFTERNOON AND
THIS EVENING WHICH WOULD LIMIT THE OVERALL HEAVY RAIN THREAT.
STILL ALL THE GFS ENSEMBLE MEMBERS SHOW A HEAVY RAIN CENTER
DEVELOPING ACROSS NCNTL NEB TONIGHT...LIKELY A RESULT OF THE LOW
LEVEL JET INCREASING TO AROUND 30 KT. NONE OF THE OTHER MODELS
SHOW THIS. THE GEMREG IS THE CLOSEST BUT HAS THE FRONT AND HEAVY
RAIN ACROSS SERN SD WHILE THE NAM AND ECM ARE VERY MODEST WITH
QPF BUT SHOW NCNTL NEB LIKE THE GFS ENSEMBLE.
HIGHS TODAY RANGE FROM THE LOWER 80S NORTH TO MID 90S SOUTH.
EXTENSIVE MID AND HIGH LEVEL CLOUDINESS WILL LIMIT HIGHS.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 330 AM CDT WED AUG 21 2013
MAIN CONCERNS WITH THE LONG TERM FOCUS WITH THUNDERSTORM CHANCES
EARLY ON...THEN TRANSITION INTO TEMPERATURES BY THE WEEKEND INTO
NEXT WEEK.
UPPER LEVEL RIDGE WILL BUILD EAST FROM THE SOUTHERN/CENTRAL
ROCKIES OVER THE CENTRAL PLAINS BY THE WEEKEND. MEANWHILE A WEAK
COLD FRONT WILL DRIFT SOUTH ACROSS THE STATE...THEN BECOMES
REPLACED BY A HIGH PRESSURE BUILDING OVER THE UPPER MISS RVR
VALLEY AND THE GREAT LAKES. A SFC LEE TROUGH DEVELOPS ALONG THE
FRONT...AND REMAINS QUASI-STATIONARY THROUGH THE WEEKEND.
THUNDERSTORM CHANCES INITIALLY ON THURSDAY...GENERALLY
ALONG/NORTH OF THE FRONT...WHERE STEEPER LAPSE RATE PERSIST. ALSO
GOING TO BE ALONG THE NORTHERN SIDE OF THE DEVELOPING RIDGE...AND
ASSOCIATED WITH A MID LEVEL DISTURBANCE. AS THE SHORT WAVE PUSHES
EAST...CHANCE FOR STORMS DIMINISHES THURSDAY NIGHT. THE NEXT
CHANCE FOR STORMS IS ALONG THE HIGHER TERRAIN AND THE LEE SIDE
TROUGH GENERALLY TO THE WEST OF THE CWA. MODELS BRING ANOTHER
DISTURBANCE ACROSS THE ROCKIES SATURDAY WHICH HAS THE POTENTIAL TO
SUSTAIN ACTIVITY INTO THE WESTERN ZONES...AND WILL HAVE SOME LOW
POPS. OTHERWISE RIDGE WILL BRING DRY CONDITIONS.
TEMPERATURES ON THURSDAY ARE EXPECTED TO BE COOL WITH SOME CLOUDS
AND COOLER AIR FROM THE COLD FRONT. 00Z MODEL GUIDANCE HAS COME
IN SEVERAL DEGREE ABOVE THE 12Z RUN...HOWEVER FORECAST DOES NOT
JUMP AS FAR AS GUIDANCE YET...AS EXPECT THE CLOUDS TO KEEP TEMPS
IN THE LOWER TO MID 80S. BY FRIDAY THE WARM UP BEGINS...AS HIGH
RETURN TO WELL ABOVE NORMAL 90S FOR THE WEEKEND AND TO START NEXT
WEEK.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1223 AM CDT WED AUG 21 2013
SCATTERED TO OCCASIONALLY NUMEROUS TSTMS ARE EXPECTED TO DEVELOP
FROM ROUGHLY 21Z THIS AFTN ONWARD THROUGH 06Z TONIGHT. MOST OF
THE TSTM ACTIVITY SHOULD BE LOCATED EAST OF HIGHWAY 83 WITH
COVERAGE DECREASING WESTWARD. OTHERWISE VFR IS EXPECTED WITH MID
AND HIGH LEVEL CLOUDINESS.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...CDC
LONG TERM...MASEK
AVIATION...CDC
AREA FORECAST DISCUSSION
NWS OMAHA/VALLEY NE
300 AM CDT WED AUG 21 2013
.DISCUSSION...
TEMPERATURES THROUGH THE PERIOD AND RAIN CHANCES LATE TODAY INTO
FRIDAY WILL BE THE MAIN FORECAST CONCERNS.
WV/IR SATELLITE LOOP SHOWS A PULSING AREA OF CONVECTION FROM
SOUTHEAST SOUTH DAKOTA INTO NORTHWEST NEBRASKA AT 07Z IN ADVANCE
OF A WEAK SURFACE COLD FRONT FROM NORTHWEST MINNESOTA INTO FAR
NORTHWEST NEBRASKA. 00Z MODELS SIMILAR IN PLACING ISOLATED TO
WIDELY SCATTERED CONVECTION IN THE VICINITY OF THE FRONT TODAY AND
ESPECIALLY LATE THIS AFTERNOON AS IT WORKS INTO NORTHERN PORTIONS
OF IOWA AND NEBRASKA WITH RAP FORECAST SOUNDINGS SHOWING LITTLE
CAP IN PLACE. CONVECTION LIKELY TO EXPAND DURING THE EVENING AS
LOW LEVEL JET FEEDS INTO THE COMPLEX. SURFACE FRONT STALLS NEAR
THE SOUTHERN NEBRASKA BORDER BY THURSDAY MORNING THEN BEGINS TO
LIFT BACK NORTH DURING THE DAY WITH A CONTINUED CHANCE OF SHOWERS
AND THUNDERSTORMS NORTH AND EAST OF THE BOUNDARY INTO FRIDAY.
SOME COOLING ON THURSDAY...ESPECIALLY NORTH...ASSOCIATED WITH
CLOUDS AND PRECIP BEFORE THE WARM AIR WORKS BACK INTO THE AREA
ON FRIDAY.
EXTENDED PERIOD STILL HOT AND DRY WITH UPPER LEVEL HIGH PRESSURE
CENTERED OVER THE CENTRAL PART OF THE NATION.
&&
.AVIATION...
06Z TAFS FOR KOMA...KLNK...KOFK.
VFR CONDITIONS SHOULD PERSIST THROUGH THE TAF PERIOD AT KOMA AND
KLNK. INCLUDED A PROB30 GROUP AT KOFK FOR -TSRA AND MVFR VSBY AFTER
00Z AS A COLD FRONT APPROACHES. SOUTHERLY WINDS WILL CONTINUE AHEAD
OF THE FRONT...MAINLY UNDER 14 KNOTS.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
FOBERT/MILLER
AREA FORECAST DISCUSSION
NWS OMAHA/VALLEY NE
1140 PM CDT TUE AUG 20 2013
.AVIATION...
06Z TAFS FOR KOMA...KLNK...KOFK.
VFR CONDITIONS SHOULD PERSIST THROUGH THE TAF PERIOD AT KOMA AND
KLNK. INCLUDED A PROB30 GROUP AT KOFK FOR -TSRA AND MVFR VSBY AFTER
00Z AS A COLD FRONT APPROACHES. SOUTHERLY WINDS WILL CONTINUE AHEAD
OF THE FRONT...MAINLY UNDER 14 KNOTS.
MILLER
&&
.PREV DISCUSSION... /ISSUED 1006 PM CDT TUE AUG 20 2013/
UPDATE...
INCLUDED PRECIP MENTION IN THE FAR NORTH AND ADJUSTED CLOUDS DUE
TO CONVECTIVE DEBRIS AND TWEAKS TO DEWPOINTS AND LOW TEMPS.
DISCUSSION...
THUNDERSTORMS IN WESTERN NEBRASKA INTO SOUTH CENTRAL SOUTH DAKOTA
PROVIDING SOME CONVECTIVE DEBRIS/CLOUDS FOR PARTS OF NEBRASKA
THIS EVENING WITH A SHORTWAVE TROF. THIS SHORTWAVE IS FORECAST TO
CONTINUE TO PUSH EAST THRU 12Z. THE BULK OF THE PRECIPITATION SHOULD
REMAIN TO THE NORTH...HOWEVER THE 12Z 4KM WRF/ AND LATEST HRRR AND
00Z NAM ARE TRYING TO DEVELOP SOME SHRA/TSRA INTO NORTHEAST
NEBRASKA AND PARTS OF WESTERN IOWA...HOWEVER IT WILL HAVE A TOUGH
TIME WITH WARM MID LEVEL TEMPERATURES IN PLACE. WITH A DECENT
45KT LOW LEVEL JET AND THETA-E ADVECTION...FORECAST SOUNDINGS ARE
MOIST ABOVE H85 AND COULD SEE SOME ELEVATED SHRA/TSRA TRY TO GET
GOING. WITH LIMITED COVERAGE...ONLY MENTIONED ISOLATED POPS IN THE
FAR NORTH.
ZAPOTOCNY
PREV DISCUSSION... /ISSUED 331 PM CDT TUE AUG 20 2013/
DISCUSSION...
MAIN FORECAST CONCERNS IN THE NEAR TERM ARE TEMPERATURES AND
DEWPOINTS WITH FOCUS THEN TURNING TO TSTM CHANCES WED AFTERNOON
INTO THURSDAY.
LOW LEVEL WARM AIR ADVECTION IS UNDERWAY ACROSS THE FORECAST
AREA. TEMPERATURES BY MID AFTERNOON HAVE RISEN INTO THE UPPER 80S
TO LOWER 90S. IN ADDITION...AN AXIS OF HIGHER DEWPOINTS INTO THE
MID 70S ARE OCCURRING OVER OUR NORTHERN CWA THIS AFTERNOON.
OTHERWISE...UPPER LEVEL HIGH PRESSURE CONTINUES TO DOMINATE A GOOD
PORTION OF THE CENTRAL U.S.
850MB TEMPS WILL BE A DEGREE OR TWO WARMER ON WEDNESDAY SO WILL
RAISE HIGHS JUST A BIT. A COLD FRONT IS PROGGED TO MOVE INTO THE
NORTHERN CWA BY WEDNESDAY AFTERNOON. A FEW STORMS COULD DEVELOP IN
THE AFTERNOON...BUT BULK SHEAR WILL BE RELATIVELY WEAK AND SOME
CONVECTIVE INHIBITION WILL NEED TO BE OVERCOME IN ORDER TO GET
ANY SEVERE STORMS. BETTER CHANCE FOR PCPN WILL BE INTO THE
EVENING HOURS AND OVERNIGHT INTO THURSDAY MORNING. ALL MODELS ARE
COMING INTO GOOD CONSENSUS...INCLUDING THE 12Z ECMWF...IN THAT
PCPN AREA WILL GENERALLY REMAIN POST FRONTAL AND MOVE SOUTH TOWARD
I-80 THROUGH EARLY THURSDAY. HAVE COOLED TEMPS IN THE NORTH FOR
WEDNESDAY BEHIND THE FRONT.
THE UPPER RIDGE AXIS WILL MOVE OVER THE CENTRAL PLAINS REGION BY
FRIDAY ALLOWING A WARM AND HUMID AIRMASS TO RETURN TO ALL OF THE
FORECAST AREA INTO THE WEEKEND.
KERN
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS RALEIGH NC
356 AM EDT WED AUG 21 2013
.SYNOPSIS...
AN UPPER LEVEL TROUGH WILL APPROACH THE CAROLINAS FROM THE WEST THIS
EVENING...THEN TRACK EAST ACROSS THE REGION ON THURSDAY. SURFACE
HIGH PRESSURE WILL STRENGTHEN ACROSS THE OHIO VALLEY IN THE WAKE OF
THE UPPER LEVEL TROUGH...DRIVING A COLD FRONT SOUTHWARD INTO THE
CAROLINAS DURING THE DAY FRIDAY.
&&
.NEAR TERM /TODAY AND TONIGHT/...
AS OF 330 AM WEDNESDAY...
OVERVIEW:
AN UPPER LEVEL LOW CENTERED OVER INDIANA AT 06Z WILL TRACK EASTWARD
INTO EASTERN OH/KY BY 00Z THIS EVENING...AND INTO THE MID-ATLANTIC
BY 12Z THU. SW FLOW ALOFT TODAY WILL STRENGTHEN AND VEER TOWARD THE
WEST ACROSS THE REGION TONIGHT AS THE UPPER LEVEL WAVE TRACKS INTO
THE MID-ATLANTIC...WITH 30 METER H5 HEIGHT FALLS PROGGED BETWEEN
00-12Z THU. THE BERMUDA RIDGE EXTENDING WESTWARD INTO THE CAROLINAS
WILL WEAKEN THIS AFTERNOON INTO TONIGHT AS A LOW-LEVEL TROUGH
ATTENDANT THE AFOREMENTIONED UPPER LEVEL WAVE PROGRESSES INTO THE
MID-ATLANTIC.
PRECIPITATION CHANCES:
SHOWER ACTIVITY EXTENDING WSW-ENE FROM VUJ-HBI-RDU-RWI AT 07Z THIS
MORNING APPEARS TO BE ASSOCIATED WITH WEAK DPVA FROM SMALL AMPLITUDE
DISTURBANCES EMBEDDED IN SW FLOW ALOFT IN THE PRESENCE OF A VERY
MOIST (2.00" PWAT) AND MARGINALLY UNSTABLE (500-1000 J/KG MUCAPE)
ENVIRONMENT. LATEST RAP GUIDANCE SUGGESTS THE AFOREMENTIONED
SHORTWAVE ENERGY SHOULD LIFT NORTHWARD TOWARD THE N/NW PIEDMONT THIS
MORNING...AND EXPECT THE BEST CHANCE OF SHOWER ACTIVITY ALONG AND
NORTH OF THE I-85 CORRIDOR THROUGH 15Z. THIS AFT/EVE INTO TONIGHT...
CONFIDENCE IN CONVECTIVE COVERAGE...TIMING AND LOCATION IS LOWER
THAN NORMAL. GIVEN A VERY MOIST AIRMASS...500-1500 J/KG MLCAPE AT
PEAK HEATING AND A GOOD PROBABILITY OF SMALL AMPLITUDE WAVES IN SW
(INCREASINGLY WSW) FLOW ALOFT ACROSS THE NORTHERN AND WESTERN
PIEDMONT...ONE WOULD EXPECT ABOVE AVERAGE CHANCES FOR PRECIP... ESP
IN THE N/NW PIEDMONT. THE LATEST CONVECTION ALLOWING MODELS DIFFER
IN TIMING AND COVERAGE...BUT ALL SEEM TO INDICATE A BETTER POTENTIAL
FOR CONVECTION IN THE N/NW PIEDMONT AND PERHAPS ALSO IN THE SE
COASTAL PLAIN IN ASSOC/W THE SEABREEZE AND LIGHT ONSHORE FLOW...
WITH THE BEST CHANCE BETWEEN 20-03Z. THIS SEEMS PRETTY REASONABLE
GIVEN THE SETUP. EXPECT CHANCES TO DIMINISH WITHIN A FEW HRS AFTER
SUNSET...THOUGH A TOKEN SLIGHT CHANCE WILL PERSIST GIVEN SUCH DEEP
MOISTURE AND MARGINAL HEIGHT FALLS ALOFT AS THE UPPER LEVEL WAVE
TRACKS INTO THE MID-ATLANTIC TO THE NORTH OF CENTRAL NC.
TEMPERATRUES:
HIGHS TODAY SOMEWHAT CHALLENGING AS IN PREVIOUS DAYS WITH TEMPS
PRIMARILY DEPENDENT ON CLOUD COVER AND CONVECTION. EXPECT HIGHS
GENERALLY IN THE LOWER/MID 80S...WARMEST IN THE COASTAL PLAIN AND
COOLEST IN THE N/NW PIEDMONT WHERE HIGHS IN THE UPPER 70S (SIMILAR
TO WINSTON-SALEM YESTERDAY) ARE NOT OUT OF THE QUESTION. LOWS
TONIGHT SIMILAR TO PREVIOUS NIGHTS IN THE 68-73F RANGE. -VINCENT
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 300 AM WEDNESDAY...
A PRE-FRONTAL TROUGH WILL SET UP OVER THE EASTERN PIEDMONT/SANDHILLS
THURSDAY AS THE MEAN FLOW BECOMES MORE WESTERLY IN THE REAR OF THE
DEPARTING MID/UPPER TROUGH OFFSHORE. THIS SHOULD LEAD TO A REDUCTION
IN THE CHANCE OF CONVECTION EXCEPT ALONG AND EAST OF THE TROUGH
THURSDAY AFTERNOON INTO THE EVENING. QPF OF AROUND 0.25 WILL BE
FORECAST FROM AROUND KFAY NE TO KRDU AND RWI (AREAL AVERAGE)... WITH
0.01 TO THE WEST OVER THE TRIAD REGION. CHANCE POP ALL ZONES BUT
ONLY LOW CHANCE (25-30 PERCENT) NW... TO 50 IN THE SE. HIGHS SHOULD
REBOUND INTO THE MID TO UPPER 80S EXCEPT AROUND 90 IN THE SE. PW`S
WILL ALSO REDUCE TO LESS THAN 1.25 IN THE NW TO AROUND 1.5 IN THE
EAST. DEW POINTS SHOULD MIX OUT INTO THE LOWER TO MID 60S NW...
ENHANCING CONFIDENCE IN THE LOWER POP FORECAST.
THURSDAY NIGHT AND FRIDAY... THE COLD FRONT SHOULD EVENTUALLY
OVERTAKE THE PRE-FRONTAL TROUGH OVER THE SOUTHERN AND EASTERN ZONES
FRIDAY. UNTIL THEN... ANOTHER DAY OF MOSTLY SCATTERED SHOWERS AND
THUNDERSTORMS IS EXPECTED... MAINLY IN THE SOUTH AND EAST (WHERE
PW`S REMAIN NEARLY 1.5 INCHES)... ALONG AND AHEAD OF THE CONVERGENCE
ZONE. THE CHANCE OF SHOWERS/STORMS WILL DIMINISH OVERNIGHT FRIDAY
NIGHT AS THE FRONT SETTLES NEAR THE SC BORDER 12Z SATURDAY. LOWS
65-70. HIGHS FRIDAY WITH A WIND SHIFT TO THE NE... 86-91.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 300 AM WEDNESDAY...
A LARGE UPPER TROUGH IS FORECAST TO BE ANCHORED IN THE WESTERN
ATLANTIC AS AN UPPER RIDGE BECOMES ESTABLISHED OVER THE PLAINS THIS
PERIOD. AN ANOMALOUS MEAN NORTHERLY FLOW WILL RESULT FROM THE GREAT
LAKES AND NEW ENGLAND SOUTHWARD DEEP INTO SC/GA. THIS WILL BE A DRY
AND COOL FLOW FOR LATE AUGUST. SURFACE CAA WILL BE MOST PRONOUNCED
SATURDAY AND SUNDAY AS STRONG (~1026+ MB) SURFACE HIGH PRESSURE
BUILDS INTO NC FROM NY/PA. SATURDAY WILL BE THE DAY WITH THE
STRONGEST DAA AS THE MAIN COLD FRONT WILL BEGIN THE DAY NEAR THE SC
BORDER... BUT SHIFT DEEP INTO SC/GA BY LATE SATURDAY. SENSIBLE
WEATHER... PARTLY TO MOSTLY SUNNY SATURDAY. MOSTLY SUNNY SUNDAY.
CLEAR SATURDAY NIGHT. HIGHS SATURDAY AND SUNDAY SHOULD BE ONLY 80-85
(A GOOD 5-8 DEGREES BELOW NORMAL). LOWS SUNDAY AND MONDAY SHOULD BE
IN THE 50S NORTH... AND LOWER 60S SOUTH (ALMOST 10 DEGREES BELOW
NORMAL).
FOR MONDAY THROUGH TUESDAY... A GRADUAL WARMING TREND BUT STILL DRY.
SURFACE HIGH PRESSURE SHOULD BECOME ANCHORED OVER THE APPALACHIANS
AS THE UPPER RIDGE OVER THE MID-MISSISSIPPI VALLEY REMAINS STRONG.
SENSIBLE WEATHER... MOSTLY CLEAR/MOSTLY SUNNY. LOWS 58-65. HIGHS IN
THE 80S.
&&
.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
AS OF 230 AM WEDNESDAY...
24-HR TAF PERIOD:
A WIDE VARIETY OF CONDITIONS ARE EXPECTED ACROSS CENTRAL NC THIS
MORNING...RANGING FROM LIFR CEILINGS/FOG AT THE FAY TERMINAL TO MVFR
CEILINGS AND LIGHT RAIN AT THE INT/GSO TERMINALS TO VFR CEILINGS
WITH OCCASIONAL MVFR CEILINGS AT THE RDU/RWI TERMINALS. SUB-VFR
CONDITIONS WILL IMPROVE TO MVFR AND EVENTUALLY VFR IN MOST AREAS
BETWEEN 12-16Z AS INSOLATION/MIXING STRENGTHENS...THOUGH ISOLD/SCT
SHOWER ACTIVITY MAY ALLOW MVFR CONDITIONS TO PERSIST A WHILE
LONGER...PRIMARILY AT THE INT/GSO TERMINALS. EXPECT AN INCREASING
POTENTIAL FOR SHOWERS AND THUNDERSTORMS THIS AFTERNOON
(18-21Z)...WITH THE BEST CHANCE LATE THIS AFT/EVE BETWEEN 21-04Z AS
AN UPPER LEVEL DISTURBANCES TRACKS EAST INTO THE MID-ATLANTIC. AREAS
OF SUB-VFR FOG AND CEILINGS CAN BE EXPECTED AGAIN LATE TONIGHT INTO
THURSDAY MORNING GIVEN A MOIST AIRMASS AND SIMILAR PATTERN.
LOOKING AHEAD:
AN INCREASED POTENTIAL FOR SHOWERS AND THUNDERSTORMS CAN BE EXPECTED
THURSDAY/FRIDAY AS A COLD FRONT SLOWLY APPROACHES FROM THE NORTH.
VFR CONDITIONS AND A NORTHEAST BREEZE ARE EXPECTED TO PREVAIL IN THE
WAKE OF THE FRONT SAT/SUN AS DRY HIGH PRESSURE BUILDS INTO THE
MID-ATLANTIC. -VINCENT
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...VINCENT
NEAR TERM...VINCENT
SHORT TERM...BADGETT
LONG TERM...BADGETT
AVIATION...VINCENT
AREA FORECAST DISCUSSION
NWS SIOUX FALLS SD
429 AM CDT WED AUG 21 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 349 AM CDT WED AUG 21 2013
CONVECTION ACROSS CENTRAL SOUTH DAKOTA RUNNING INTO THE CAP AS IT
WORKS EAST OF THE JAMES RIVER VALLEY. THE DYING CONVECTION HAS
PRODUCED HEAT BURSTS OVER THE PAST FEW HOURS IN BOTH CHAMBERLAIN
AND MITCHELL. HRRR SHOWS CONVECTION DEVELOPING IN THE NEXT FEW
HOURS ALONG WEAK BOUNDARY SLOWLY EAKING SOUTH THROUGH THE NORTHERN
CWA THIS MORNING. HAVE SOME 20 POPS TO COVER THE POTENTIAL OF
THIS...BUT STILL NOT CONVINCED THAT STORMS ARE GOING TO BE ABLE TO
GET AROUND THE CAP. AHEAD OF THE BOUNDARY...WILL BE ANOTHER WARM
AND HUMID DAY WITH HEAT INDEX VALUES A FEW DEGREES SHY OF ADVISORY
CRITERIA. MODELS INDICATE THAT A WEAK SHORTWAVE MOVING OUT OF
WESTERN SOUTH DAKOTA THIS MORNING MAY TRY TO INTERACT WITH THE
BOUNDARY POTENTIALLY PRODUCING THUNDERSTORMS ACROSS MAINLY
NORTHWEST IOWA. STEEP MID LEVEL LAPSE RATES LEAD TO MOST UNSTABLE
CAPE VALUES OF 2000-2500 J/KG....THOUGH STILL FAIRLY STRONG CAP TO
OVERCOME. IF STORMS ARE ABLE TO DEVELOP...VEERING PROFILE MAY AID
IN STORM ORGANIZATION...THOUGH WIND SPEEDS ARE SOMEWHAT WEAK. AS
SUCH...THE SEE TEXT SEVERE WEATHER OUTLOOK SEEMS REASONABLE WITH
CHANCE OF CONVECTION BEING VERY CONDITIONAL.
BOUNDARY IS EXPECTED TO STALL ACROSS THE SOUTHERN EDGE OF THE
FORECAST AREA TONIGHT CREATING ADDITIONAL CHANCES FOR
THUNDERSTORMS. TRIMMED BACK THE NORTHERN EXTENT OF POPS TONIGHT
WITH DRIER AIRMASS BEHIND THE FRONT MAKING IT DIFFICULT FOR
SHOWERS AND THUNDERSTORMS TO DEVELOP. EXPECT QUITE A THERMAL
GRADIENT ACROSS THE AREA FROM THE UPPER 50S ACROSS SOUTHWEST
MINNESOTA TO NEAR 70 ACROSS THE SOUTHERN EDGE OF THE FORECAST AREA
NEAR THE FRONT.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 349 AM CDT WED AUG 21 2013
CONVECTION CHANCES ARE SOMEWHAT TRICKY ON THURSDAY AS
BOUNDARY/THEATE ADVECTION LIFTS BACK TO THE NORTH. FORCING APPEARS
TO OUTRUN THE MOISTURE...AS LOW LEVEL MOISTURE APPEARS TO BE HARD TO COME
BY ACROSS THE NORTHERN CWA. THEREFORE...HAVE LIMITED CONVECTION CHANCES TO
SOUTHERN EDGE OF THE FORECAST AREA WHERE THE SLIGHTLY DEEPER
MOISTURE EXISTS.
HUMID CONDITIONS RETURN ON FRIDAY AS THE GULF OPENS BACK UP WITH
SOUTHERLY FLOW FEEDING INTO THE PLAINS. 850 HPA TEMPS WARM TO NEAR
20C DURING THE DAY LEADING TO HIGHS IN THE 80S TO NEAR 90.
STRONG LOW LEVEL JET OF 40-50 KNOTS IS EXPECTED TO DEVELOP FRIDAY
NIGHT. HAVE RAISED LOWS IN SW MN ALONG THE BUFFALO RIDGE AS
EXPOSED LOCATIONS WILL LIKELY HAVE TROUBLE COOLING OFF.
IN THE EXTENDED...SATURDAY THROUGH TUESDAY OF NEXT WEEK...A BROAD
UPPER LEVEL RIDGE REMAINS PARKED OVER THE CENTRAL PORTION OF THE
U.S. THROUGH THE PERIOD. WITH OUR AREA IN A SOUTHERLY FLOW IN
RESPONSE TO SURFACE RIDGING PARKED OVER THE EASTERN PART OF THE
NATION...MUCH ABOVE NORMAL TEMPERATURES WILL BE THE RULE. WITH
PROGGED 850 MB TEMPERATURES IN THE MID AND UPPER 20S C HIGHS WILL
GENERALLY RUN LOWER TO MID 90S EACH DAY...WITH HUMIDITY RETURNING AS
DEWPOINTS CLIMB INTO THE MID AND UPPER 60S. 925 MB TEMPERATURES
WOULD SUPPORT LOWS IN THE UPPER 60S TO LOWER 70S. IN TERMS OF
PRECIPITATION CHANCES DURING THE EXTENDED...MODELS HAVING USUAL
DIFFERENCES WITH REGARD TO MINOR SHORTWAVES ROUNDING THE UPPER THE
LEVEL RIDGE...THOUGH KEPT IT DRY THROUGH THE PERIOD WITH SUPPORT
FROM BOTH THE 00Z ECMWF AND GEM.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1103 PM CDT TUE AUG 20 2013
VFR CONDITIONS EXPECTED TO DOMINATE THROUGH THE FORECAST PERIOD...
ALTHOUGH WITH HIGH BOUNDARY LAYER MOISTURE LEVELS...PATCHY FOG AGAIN
POSSIBLE THROUGH SHORTLY AFTER SUNRISE WEDNESDAY. NOT EXPECTING THE
WIDESPREAD IFR-LIFR CONDITIONS AS WAS SEEN TUESDAY MORNING...BUT
PATCHY MVFR VISIBILITY POSSIBLE IN AREAS WHERE WINDS DROP OFF AND
HAVE ADDED TO KHON FOR A FEW HOURS AROUND SUNRISE. SOUTHWESTERLY LOW
LEVEL JET OF 30-35KT DEVELOPING AHEAD OF THE BOUNDARY TONIGHT COULD
CREATE LOW LEVEL WIND SHEAR CONDITIONS AT KSUX. LATEST SHORT RANGE
MODELS STARTING TO SHOW THIS MORE THAN PREVIOUS RUNS...SO HAVE ADDED
LLWS TO KSUX THROUGH THE EARLY MORNING.
SCATTERED HIGH BASED THUNDERSTORMS IN FAR WESTERN CWA AT START OF
THE PERIOD EXPECTED TO WEAKEN AS THEY TRY TO MOVE EAST AWAY FROM
WEAK COLD FRONT IN CENTRAL SD. EXPECT THIS ACTIVITY TO REMAIN SOUTH
OF KHON AND WEAKEN BEFORE IT REACHES I-29 CORRIDOR. CHANCE OF SPOTTY
THUNDERSTORMS THEN SHIFTS INTO SOUTHWEST MINNESOTA AND SOUTH OF I-90
BY LATE WEDNESDAY AFTERNOON AS THE COLD FRONT MOVES INTO THAT AREA.
CAPPING LIKELY TO LIMIT DEVELOPMENT THROUGH 22/00Z...BUT CHANCE WILL
INCREASE THROUGH THE MISSOURI RIVER VALLEY AS LOW LEVEL JET IMPINGES
ON THE BOUNDARY WHICH STALLS NEAR FAR SOUTHERN CWA. HAVE ADDED A FEW
HOURS OF THUNDER TO KSUX WEDNESDAY EVENING...BUT TIMING/LOCATION IS
STILL UNCERTAIN...SO TIMING MAY CHANGE IN LATER FORECASTS.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
SHORT TERM...
LONG TERM...JM
AVIATION...JH
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
428 AM EDT WED AUG 21 2013
.SYNOPSIS...
AN UPPER LEVEL LOW WILL MOVE FROM THE OHIO VALLEY TO THE MID
ATLANTIC COAST BY LATE THURSDAY. A COLD FRONT WILL MOVE FROM THE
GREAT LAKES ON THURSDAY INTO THE CAROLINAS BY SATURDAY. DRIER AND
COOLER HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT FOR THE
WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 410 AM EDT WEDNESDAY...
WHEN I FIRST JOINED THE NATIONAL WEATHER SERVICE MY ELDERS TOLD ME
A CODE THEY WOULD USE WHEN THERE WAS LOW CONFIDENCE IN THE
FORECAST. THEY WOULD APPEND A NUMBER 9 TO THE END OF THEIR NAME
WHEN ISSUING THE FORECAST. TODAY IS DEFINITELY A 9 DAY.
MODELS SHOWING SIGNIFICANT DIFFERENCES IN THE TIMING AND LOCATION
OF PRECIPITATION FOR TODAY AND TONIGHT. HOWEVER...THE LATEST RAP
AND HRRR GUIDANCE HAVE SOMEWHAT OF A REASONABLE TREND WITH THE
PRECIPITATION MOVING NORTH FROM THE CAROLINAS AND THE 00Z LOCAL
WRF SHOWED DECENT CONTINUITY WITH THE PRECIPITATION IN WEST
VIRGINIA.
EXPECT A MAJORITY OF THE PRECIPITATION FROM THE CAROLINAS TO MOVE
THROUGH THE FORECAST AREA THIS MORNING. BY LATE THIS
AFTERNOON...THE UPPER LOW TRACKING WEST OUT OF THE OHIO VALLEY
SHOULD BE TRIGGERING SHOWERS AND THUNDERSTORMS IN THE MOUNTAINS.
AS THIS FEATURE MOVES EAST THIS EVENING...THE COUNTY WARNING AREA
WILL BE IN A FAVORABLE QUADRANT OF THE ASSOCIATED UPPER JET. NET
RESULT IS NOT MUCH CHANGE IN THE PROBABILITY OF PRECIPITATION FOR
TODAY AND TONIGHT.
BUFKIT SHOWED WINDS THROUGH MID LAYERS OF THE ATMOSPHERE LESS THAN
15 KNOTS...WHICH SUGGESTS INDIVIDUAL STORMS THAT DEVELOP MAY BE
MOVING SLOWLY. FLASH FLOOD GUIDANCE IS LESS THAN 2 INCHES FROM THE
NEW RIVER VALLEY AND SOUTHEAST WEST VIRGINIA INTO NORTHWEST NORTH
CAROLINA. WITH PRECIPITABLE WATER VALUES AROUND 1.5 INCHES TODAY
AND TONIGHT HEAVY RAIN REMAINS A THREAT.
TRENDED TOWARD GRIDDED LAMP GUIDANCE FOR MAXIMUM TEMPERATURES
TODAY...BUT WITH CLOUDS AND PRECIPITATION THIS MORNING...WITH BE
COUNTING ON SOME BREAKS IN THE CLOUDS FOR THIS AFTERNOON.
MILD SURFACE DEW POINTS AND CLOUD COVER WILL LIMIT COOLING
OVERNIGHT. LEANED TOWARD WARMER NUMBERS FOR OVERNIGHT LOWS.
&&
.SHORT TERM /THURSDAY THROUGH SATURDAY/...
AS OF 330 AM EDT WEDNESDAY...
UPPER LOW CENTER AROUND LAFAYETTE INDIANA THIS MORNING WILL TRAVEL
EAST AND REACH THE EAST COAST ON FRIDAY. THIS LOW CENTER MOVES INTO
THE ATLANTIC BY SATURDAY...ALLOWING A SURFACE HIGH TO PUSH INTO THE
REGION JUST IN TIME FOR THE WEEKEND.
SHOWERS AND THUNDERSTORMS WILL DEVELOP AHEAD OF THE COLD FRONT ON
THURSDAY. KEPT THE ISOLATED TO SCATTERED POPS IN FOR THURSDAY. WENT
WITH HIGH TEMPERATURES CLOSER TO THE COOLER ADJMET WITH READINGS
FROM THE MID 70S IN THE MOUNTAINS TO THE MID 80S IN THE SOUTHEAST.
A COLD FRONT WILL CROSS THE REGION THURSDAY NIGHT INTO FRIDAY.
PLACED THE HIGHEST POPS (GOOD CHANCE TO LIKELY) IN THE WEST THURSDAY
NIGHT INTO FRIDAY. LEANED TOWARDS THE WARMER MOS LOW TEMPERATURES
THURSDAY NIGHT WITH READINGS FROM THE LOWER 60S IN THE MOUNTAINS TO
NEAR 70 DEGREES IN THE PIEDMONT. HIGHS ON FRIDAY WILL VARY FROM THE
LOWER 70S IN THE WEST TO THE UPPER 80S IN THE SOUTHEAST. LOWERED
POPS FRIDAY NIGHT FROM NORTH TO SOUTH. USED THE ENSEMBLE LOWS FRIDAY
NIGHT WITH VALUES FROM LOWER 50S IN THE NORTHWEST TO THE LOWER 60S
IN THE SOUTH. UNDER THE UPPER RIDGE...PLEASANT SATURDAY ON TAP WITH
SUNSHINE AND HIGH TEMPERATURES GENERALLY FROM MID 70S TO THE LOWER
80S.
&&
.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
AS OF 115 PM EDT TUESDAY...
DURING SUNDAY...FLOW AROUND THE SURFACE HIGH WILL BRING SOUTHEAST
FLOW INTO THE SOUTHWEST PART OF THE REGION. THIS MAY YIELD SOME
ISOLATED UPSLOPE SHOWERS. A COLD FRONT IS PROGGED TO TRY TO MAKE ITS
WAY INTO THE NORTHERN PART OF THE AREA MONDAY NIGHT INTO TUESDAY.
THERE MAY BE SOME ISOLATED SHOWERS IN ADVANCE OF THIS FRONT THAT
REACH NORTHERN PARTS OF THE AREA LATE IN THE DAY MONDAY. SEVERAL
WEAK SHORTWAVES WILL DROP SOUTH IN THE NORTHWEST FLOW ALOFT ACROSS
NORTHERN PORTIONS OF OUR REGION TUESDAY INTO WEDNESDAY.
&&
.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
AS OF 135 AM EDT WEDNESDAY...
WITH MORE CLOUDS EARLY THIS MORNING...AREAS OF IFR CIG/VIS MAY BE
LESS EXPANSIVE AND PERSISTENT THAN TUESDAY MORNING. MID AND HIGH
CLOUDS STRETCH FROM THE MID ATLANTIC ALL THE WAY INTO THE GULF
COAST STATES. AS USUAL LWB SEEMS THE MOST LIKELY TO EXPERIENCE
LIFR/IFR CONDS.
A BETTER UPPER SHORT WAVE IS EXPECTED TO MOVE IN EARLY TODAY...AND
THIS SHOULD RESULT IN BETTER COVERAGE OF SHOWERS AND
THUNDERSTORMS...ESPECIALLY IN THE MOUNTAINS...PERHAPS AS EARLY AS
MID MORNING...SOME WELL BEFORE 18Z. CLOSET PRECIPITATION WITH THIS
SHORT WAVE AT 1AM WAS IN CENTRAL GEORGIA...SO FUTURE TAF UPDATES
MAY END UP SLOWING DOWN ARRIVAL TIME OF SHOWERS AND THUNDERSTORMS.
PATTERN WILL TRANSITION TO MORE TYPICAL OF MID AUGUST THURSDAY...WITH
SOUTHWEST FLOW AND DIURNALLY DRIVEN SHOWERS AND THUNDERSTORMS.
SCATTERED LOW CLOUDS WILL LINGER DURING THE MORNING IN AREAS...
RESULTING IN A MIXTURE OF MVFR AND VFR CONDITIONS...BEFORE
IMPROVING TO MOSTLY VFR BY EARLY AFTERNOON. PATCHY DENSE FOG WILL
ALSO BE AN ISSUE EACH NIGHT. A FRONTAL BOUNDARY SHOULD MOVE
THROUGH BY FRIDAY...POSSIBLY PROVIDING BETTER COVERAGE OF SHOWERS
AND THUNDERSTORMS. BEHIND THIS FRONT DRIER AIR AND VFR CONDITIONS
ARE EXPECTED SATURDAY AND SUNDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...AMS
NEAR TERM...AMS9
SHORT TERM...KK
LONG TERM...DS/KK
AVIATION...AMS/KM
AREA FORECAST DISCUSSION
NWS PEACHTREE CITY GA
1136 AM EDT WED AUG 21 2013
.UPDATE...
LOCALIZED HEAVY RAIN AND THUNDERSTORM DEVELOPMENT HAS PERSISTED
ACROSS PORTIONS OF NORTHEAST GEORGIA THIS MORNING DUE TO PLUME OF
ENHANCED MOISTURE /AND NEAR 2.0 INCH PWATS/ ALONG A WEAK
DISTURBANCE. HAVE MAINLY ADJUSTED MORNING POPS TO BE A BIT HIGHER
IN THE NE AND HAVE BUMPED DAYTIME MAX TEMPS DOWN A BIT PER RECENT
GUIDANCE BLEND WITH LINGERING LOW LEVEL CLOUDS IN THE NORTH AND
WEST CENTRAL PORTIONS OF THE CWA. UNCERTAINTY EXISTS IN FLASH
FLOODING THREAT THROUGH REST OF DAY AS MAJORITY OF GUIDANCE IS
SUGGESTING HIGHER QPF AMOUNTS AND MORE WIDESPREAD PRECIP COVERAGE
IN THE NORTHWESTERN HALF OF THE CWA THIS AFTERNOON...WHILE A
LINGERING BOUNDARY LOOKS TO BISECT THE AREA AND ANY LATE DAY SEA
BREEZE INFLUENCE MAY SHIFT PRECIP COVERAGE ACROSS THE WATCH AREA
IN THE SOUTHEAST. ALL CONSIDERED...WILL CONTINUE WITH CURRENT
FLASH FLOOD WATCH IN THE SOUTHEAST AND MAY EXTEND ACROSS NORTHWEST
IF AFTERNOON DEVELOPMENT RAMPS UP. REST OF FORECAST LOOKS TO BE ON
TRACK AND PREVIOUS DISCUSSION FOLLOWS...
BAKER
&&
.PREV DISCUSSION... /ISSUED 750 AM EDT WED AUG 21 2013/
.SHORT TERM /TODAY THROUGH THURSDAY/...
/ISSUED AT 443 AM EDT WED AUG 21 2013/
LATEST SURFACE MAP CONTINUES TO SHOW A WEAK FRONTAL BOUNDARY STALLED
ACROSS CENTRAL GA... SOMEWHERE JUST SOUTH OF A CSG TO MCN TO AGS
LINE... WHILE A COOL WEDGE OF HIGH PRESSURE WAS STILL NOTED OVER THE
MID ATLANTIC STATES. THE SURFACE RIDGE IS PROGGED BY SHORT RANGE
MODELS TO SETTLE OFF THE CAROLINA`S COASTS THIS AFTERNOON. THIS WILL
PRODUCE A DEEPER SOUTHERLY WIND FLOW... WHICH WILL CONTINUE TO HELP
SPREAD ATLANTIC AND GULF MOISTURE NORTHWARD. SATELLITE WATER VAPOR
SHOWS A DEEP TROPICAL MOISTURE PLUME ANCHORED OVER THE STATE WHILE
AN UPPER LOW PRESSURE SYSTEM SPINS OVER THE OHIO VALLEY. EXPECT THE
WEAK FRONT TO MEANDER ACROSS CENTRAL GA AGAIN TODAY... WITH A MOIST
/2.0+ PW`S/ AND MODERATELY UNSTABLE AIRMASS /2000-2500 CAPE/ ALONG
AND SOUTH OF THE FRONT. THIS COUPLED WITH A SERIES OF DISTURBANCES
SWINGING AROUND THE BASE OF THE UPPER LOW WILL PRODUCE ANOTHER ROUND
OF SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS THIS AFTERNOON
AND EVENING. ALTHOUGH SCATTERED STORMS COULD OCCUR JUST ABOUT
ANYWHERE TODAY... EXPECT THE GREATER POTENTIAL FOR REOCCURRING
STORMS WITH HEAVY RAINFALL TO BE ACROSS CENTRAL GA WHERE THE DEEPER
MOISTURE AND GREATER INSTABILITIES WILL BE POOLED. WITH THE
POTENTIAL FOR ANOTHER 1 TO 3 INCHES OF RAINFALL OVER AN ALREADY
SATURATED GROUND... DECIDED TO PLAY IT SAFE AND POST ANOTHER FLASH
FLOOD WATCH FOR PARTS OF CENTRAL GA AGAIN TODAY... GENERALLY ALONG
AND SOUTH OF A COLUMBUS TO MACON TO WARRENTON LINE... FROM NOON
THROUGH THIS EVENING. THESE RAINFALL AMOUNTS WILL CAUSE RAPID RISES
ON AREA CREEKS... STREAMS AND RIVERS... AS WELL AS PONDING OF WATER
ACROSS LOW LYING... FLOOD PRONE AREAS IN AND AROUND THE WATCH AREA.
THE FLOOD THREAT WILL GREATLY DIMINISH BY MIDNIGHT AS CONVECTION
DIMINISHES WITH LOSS OF DAYTIME HEATING. ALTHOUGH NO WIDESPREAD
SEVERE STORMS ARE EXPECTED... SOME MID LEVEL DRY AIR SPREADING IN
FROM THE EAST COULD ENHANCE STORM DOWNDRAFT WIND GUSTS. THIS COUPLED
WITH SATURATED SOIL COULD EASILY DOWN TREES. THE OVERALL WET PATTERN
MAY BE LESSENED ON THURSDAY WITH INCREASING UPPER RIDGING FROM THE
WEST AND SURFACE HIGH PRESSURE NOSING IN FROM THE EAST. HOWEVER...
STILL EXPECT ISOLATED TO LOW SCATTERED COVERAGE OF STORMS THURSDAY
AFTERNOON AS DAYTIME TEMPS CLIMB BACK TOWARD MORE SEASONAL NORMALS
OF UPPER 80S TO LOWER 90S.
39
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
/ISSUED AT 443 AM EDT WED AUG 21 2013/
THE WET PATTERN CONTINUES INTO THE EXTENDED...BUT THERE IS AN END
IN SIGHT. DEEPER MOISTURE THAT IS OVER THE AREA IN THE SHORT TERM
FINALLY MOVES NORTH AND EAST OF THE REGION BY 00Z FRI. THERE IS
STILL A DECENT AMOUNT OF MOISTURE ACROSS THE AREA THROUGH THE
WEEKEND BUT NO WHERE NEAR AS MUCH AS WE HAVE SEEN OVER THE PAST
WEEK. PRECIPITABLE WATERS FINALLY GET BELOW 1.5 INCHES BY 12Z FRI
AND STAY THERE THROUGH THE REST OF THE EXTENDED. THE MAIN FEATURE
THAT HELPS TO DRY THINGS OUT A BIT IS THE LARGE HIGH PRESSURE
RIDGE THAT BUILDS SOUTH OUT OF THE GREAT LAKE AND NEW ENGLAND
STATES. THIS RIDGE PUSHES DON INTO N GA BEGINNING SAT NIGHT AND
BRINGS WITH IT A MUCH DRIER AIRMASS. THE RIDGE CENTER MOVES OF THE
MID ATLANTIC COAST MON MORNING BUT ITS MAIN AXIS STAYS ACROSS THE
CAROLINAS...GA...AND AL THROUGH TUE/WED. WILL KEEP A SLIGHT CHANCE
OF SHRA/TSRA IN THE FORECAST THROUGH DAY 7 AS THERE IS STILL DECENT
MOISTURE AND SOME INSTABILITY AS THIS RIDGE MOVES IN. WITH JUST
ENOUGH DAY TIME HEATING WE COULD STILL SEE SOME AFTERNOON POP UP
THUNDERSTORMS. TH GOOD NEWS IS ANYTHING THAT DEVELOPS WONT HAVE
THE DEEPER TROPICAL MOISTURE TO WORK WITH SO FLOODING WILL BECOME
LESS OF A FACTOR THROUGH THE END OF THE FORECAST PERIOD.
01
&&
.HYDROLOGY...
/ISSUED AT 443 AM EDT WED AUG 21 2013/
AN UPPER TROUGH TO THE NW WILL INTERACT WITH A STALLED FRONTAL
BOUNDARY ACROSS CENTRAL GA AND DEEP TROPICAL MOISTURE ENTRENCHED
ACROSS THE STATE TO PRODUCE ANOTHER ROUND OF SCATTERED TO NUMEROUS
SHOWERS AND THUNDERSTORMS ACROSS MUCH OF CENTRAL GA THIS AFTERNOON
AND EVENING. SLOW MOVING... REDEVELOPING STORMS COULD PRODUCE
ANOTHER 1 TO 3 INCHES OF RAINFALL ACROSS PARTS OF CENTRAL GA
TODAY... THIS OVER AN ALREADY VERY SATURATED GROUND FROM NUMEROUS
STORMS THE PAST SEVERAL DAYS. AS A RESULT... HAVE POSTED ANOTHER
FLASH FLOOD WATCH FOR AREAS GENERALLY ALONG AND SOUTH OF A COLUMBUS
TO MACON TO WARRENTON LINE FROM NOON THROUGH THIS EVENING.
HOWEVER... ITS IMPORTANT TO REMEMBER... LOCALIZED HEAVY RAIN COULD
OCCUR JUST ABOUT ANYWHERE TODAY... AND ALL INTEREST ACROSS NORTH AND
CENTRAL GA AROUND FLOOD PRONE AREAS ARE ENCOURAGED TO MONITOR STORMS
CLOSELY THIS AFTERNOON AND EVENING.
&&
.AVIATION...
12Z UPDATE...
INCREASING INSTABILITIES AND AREA SHOWERS HAVE PREVENTED LIFR/IFR
CIGS FROM DEVELOPING AROUND ATLANTA TAF SITES THIS MORNING. RADAR
SHOWS PATCHES OF -RA/-SHRA DEVELOPING FROM NEAR FFC NEWD ACROSS ATL
AND JUST NORTH OF AHN. THE HRRR MODEL SHOWS THIS AREA BECOMING MORE
ACTIVE THROUGH LATE MORNING-EARLY AFTERNOON WITH A THREAT OF -TSRA
BY 17-18Z AT ATL AND CONTINUING THRU 21-23Z TODAY. HAVE TWEAKED
TAF`S ACCORDINGLY. MODELS INDICATE IFR/MVFR CIGS WILL DEVELOP TOWARD
10-12Z THU... SO WILL SHOW MVFR BY 10Z FOR NOW. EXPECT CURRENT LIGHT
EAST WINDS TO BECOME MORE SE AROUND 7-9KTS TODAY... AND 3-4KTS
TONIGHT.
//ATL CONFIDENCE...12Z UPDATE...
MEDIUM CONFIDENCE ON MORNING CIGS AND TIMING OF -TSRA THIS
AFTERNOON. HIGH ALL OTHER ELEMENTS.
39
&&
.PRELIMINARY POINT TEMPS/POPS...
ATHENS 84 69 87 70 / 70 40 30 20
ATLANTA 83 71 87 71 / 60 40 30 20
BLAIRSVILLE 79 65 83 64 / 70 40 30 20
CARTERSVILLE 83 68 88 70 / 60 40 30 20
COLUMBUS 87 72 90 72 / 60 40 30 20
GAINESVILLE 81 69 85 69 / 70 40 30 20
MACON 87 71 90 71 / 50 40 30 20
ROME 84 67 89 70 / 60 40 30 20
PEACHTREE CITY 83 68 87 69 / 60 40 30 20
VIDALIA 89 72 90 72 / 50 40 30 20
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH THIS EVENING FOR THE FOLLOWING ZONES:
BALDWIN...BIBB...BLECKLEY...CHATTAHOOCHEE...CRAWFORD...CRISP...
DODGE...DOOLY...EMANUEL...GLASCOCK...HANCOCK...HOUSTON...
JEFFERSON...JOHNSON...JONES...LAURENS...MACON...MARION...
MONTGOMERY...PEACH...PULASKI...SCHLEY...STEWART...SUMTER...
TAYLOR...TELFAIR...TOOMBS...TREUTLEN...TWIGGS...WARREN...
WASHINGTON...WEBSTER...WHEELER...WILCOX...WILKINSON.
&&
$$
SHORT TERM...39/BAKER
LONG TERM....01
AVIATION...39
AREA FORECAST DISCUSSION...UPDATED
NWS PEACHTREE CITY GA
750 AM EDT WED AUG 21 2013
.SHORT TERM /TODAY THROUGH THURSDAY/...
/ISSUED AT 443 AM EDT WED AUG 21 2013/
LATEST SURFACE MAP CONTINUES TO SHOW A WEAK FRONTAL BOUNDARY STALLED
ACROSS CENTRAL GA... SOMEWHERE JUST SOUTH OF A CSG TO MCN TO AGS
LINE... WHILE A COOL WEDGE OF HIGH PRESSURE WAS STILL NOTED OVER THE
MID ATLANTIC STATES. THE SURFACE RIDGE IS PROGGED BY SHORT RANGE
MODELS TO SETTLE OFF THE CAROLINA`S COASTS THIS AFTERNOON. THIS WILL
PRODUCE A DEEPER SOUTHERLY WIND FLOW... WHICH WILL CONTINUE TO HELP
SPREAD ATLANTIC AND GULF MOISTURE NORTHWARD. SATELLITE WATER VAPOR
SHOWS A DEEP TROPICAL MOISTURE PLUME ANCHORED OVER THE STATE WHILE
AN UPPER LOW PRESSURE SYSTEM SPINS OVER THE OHIO VALLEY. EXPECT THE
WEAK FRONT TO MEANDER ACROSS CENTRAL GA AGAIN TODAY... WITH A MOIST
/2.0+ PW`S/ AND MODERATELY UNSTABLE AIRMASS /2000-2500 CAPE/ ALONG
AND SOUTH OF THE FRONT. THIS COUPLED WITH A SERIES OF DISTURBANCES
SWINGING AROUND THE BASE OF THE UPPER LOW WILL PRODUCE ANOTHER ROUND
OF SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS THIS AFTERNOON
AND EVENING. ALTHOUGH SCATTERED STORMS COULD OCCUR JUST ABOUT
ANYWHERE TODAY... EXPECT THE GREATER POTENTIAL FOR REOCCURRING
STORMS WITH HEAVY RAINFALL TO BE ACROSS CENTRAL GA WHERE THE DEEPER
MOISTURE AND GREATER INSTABILITIES WILL BE POOLED. WITH THE
POTENTIAL FOR ANOTHER 1 TO 3 INCHES OF RAINFALL OVER AN ALREADY
SATURATED GROUND... DECIDED TO PLAY IT SAFE AND POST ANOTHER FLASH
FLOOD WATCH FOR PARTS OF CENTRAL GA AGAIN TODAY... GENERALLY ALONG
AND SOUTH OF A COLUMBUS TO MACON TO WARRENTON LINE... FROM NOON
THROUGH THIS EVENING. THESE RAINFALL AMOUNTS WILL CAUSE RAPID RISES
ON AREA CREEKS... STREAMS AND RIVERS... AS WELL AS PONDING OF WATER
ACROSS LOW LYING... FLOOD PRONE AREAS IN AND AROUND THE WATCH AREA.
THE FLOOD THREAT WILL GREATLY DIMINISH BY MIDNIGHT AS CONVECTION
DIMINISHES WITH LOSS OF DAYTIME HEATING. ALTHOUGH NO WIDESPREAD
SEVERE STORMS ARE EXPECTED... SOME MID LEVEL DRY AIR SPREADING IN
FROM THE EAST COULD ENHANCE STORM DOWNDRAFT WIND GUSTS. THIS COUPLED
WITH SATURATED SOIL COULD EASILY DOWN TREES. THE OVERALL WET PATTERN
MAY BE LESSENED ON THURSDAY WITH INCREASING UPPER RIDGING FROM THE
WEST AND SURFACE HIGH PRESSURE NOSING IN FROM THE EAST. HOWEVER...
STILL EXPECT ISOLATED TO LOW SCATTERED COVERAGE OF STORMS THURSDAY
AFTERNOON AS DAYTIME TEMPS CLIMB BACK TOWARD MORE SEASONAL NORMALS
OF UPPER 80S TO LOWER 90S.
39
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
/ISSUED AT 443 AM EDT WED AUG 21 2013/
THE WET PATTERN CONTINUES INTO THE EXTENDED...BUT THERE IS AN END
IN SIGHT. DEEPER MOISTURE THAT IS OVER THE AREA IN THE SHORT TERM
FINALLY MOVES NORTH AND EAST OF THE REGION BY 00Z FRI. THERE IS
STILL A DECENT AMOUNT OF MOISTURE ACROSS THE AREA THROUGH THE
WEEKEND BUT NO WHERE NEAR AS MUCH AS WE HAVE SEEN OVER THE PAST
WEEK. PRECIPITABLE WATERS FINALLY GET BELOW 1.5 INCHES BY 12Z FRI
AND STAY THERE THROUGH THE REST OF THE EXTENDED. THE MAIN FEATURE
THAT HELPS TO DRY THINGS OUT A BIT IS THE LARGE HIGH PRESSURE
RIDGE THAT BUILDS SOUTH OUT OF THE GREAT LAKE AND NEW ENGLAND
STATES. THIS RIDGE PUSHES DON INTO N GA BEGINNING SAT NIGHT AND
BRINGS WITH IT A MUCH DRIER AIRMASS. THE RIDGE CENTER MOVES OF THE
MID ATLANTIC COAST MON MORNING BUT ITS MAIN AXIS STAYS ACROSS THE
CAROLINAS...GA...AND AL THROUGH TUE/WED. WILL KEEP A SLIGHT CHANCE
OF SHRA/TSRA IN THE FORECAST THROUGH DAY 7 AS THERE IS STILL DECENT
MOISTURE AND SOME INSTABILITY AS THIS RIDGE MOVES IN. WITH JUST
ENOUGH DAY TIME HEATING WE COULD STILL SEE SOME AFTERNOON POP UP
THUNDERSTORMS. TH GOOD NEWS IS ANYTHING THAT DEVELOPS WONT HAVE
THE DEEPER TROPICAL MOISTURE TO WORK WITH SO FLOODING WILL BECOME
LESS OF A FACTOR THROUGH THE END OF THE FORECAST PERIOD.
01
&&
.HYDROLOGY...
/ISSUED AT 443 AM EDT WED AUG 21 2013/
AN UPPER TROUGH TO THE NW WILL INTERACT WITH A STALLED FRONTAL
BOUNDARY ACROSS CENTRAL GA AND DEEP TROPICAL MOISTURE ENTRENCHED
ACROSS THE STATE TO PRODUCE ANOTHER ROUND OF SCATTERED TO NUMEROUS
SHOWERS AND THUNDERSTORMS ACROSS MUCH OF CENTRAL GA THIS AFTERNOON
AND EVENING. SLOW MOVING... REDEVELOPING STORMS COULD PRODUCE
ANOTHER 1 TO 3 INCHES OF RAINFALL ACROSS PARTS OF CENTRAL GA
TODAY... THIS OVER AN ALREADY VERY SATURATED GROUND FROM NUMEROUS
STORMS THE PAST SEVERAL DAYS. AS A RESULT... HAVE POSTED ANOTHER
FLASH FLOOD WATCH FOR AREAS GENERALLY ALONG AND SOUTH OF A COLUMBUS
TO MACON TO WARRENTON LINE FROM NOON THROUGH THIS EVENING.
HOWEVER... ITS IMPORTANT TO REMEMBER... LOCALIZED HEAVY RAIN COULD
OCCUR JUST ABOUT ANYWHERE TODAY... AND ALL INTEREST ACROSS NORTH AND
CENTRAL GA AROUND FLOOD PRONE AREAS ARE ENCOURAGED TO MONITOR STORMS
CLOSELY THIS AFTERNOON AND EVENING.
&&
.AVIATION...
12Z UPDATE...
INCREASING INSTABILITIES AND AREA SHOWERS HAVE PREVENTED LIFR/IFR
CIGS FROM DEVELOPING AROUND ATLANTA TAF SITES THIS MORNING. RADAR
SHOWS PATCHES OF -RA/-SHRA DEVELOPING FROM NEAR FFC NEWD ACROSS ATL
AND JUST NORTH OF AHN. THE HRRR MODEL SHOWS THIS AREA BECOMING MORE
ACTIVE THROUGH LATE MORNING-EARLY AFTERNOON WITH A THREAT OF -TSRA
BY 17-18Z AT ATL AND CONTINUING THRU 21-23Z TODAY. HAVE TWEAKED
TAF`S ACCORDINGLY. MODELS INDICATE IFR/MVFR CIGS WILL DEVELOP TOWARD
10-12Z THU... SO WILL SHOW MVFR BY 10Z FOR NOW. EXPECT CURRENT LIGHT
EAST WINDS TO BECOME MORE SE AROUND 7-9KTS TODAY... AND 3-4KTS
TONIGHT.
//ATL CONFIDENCE...12Z UPDATE...
MEDIUM CONFIDENCE ON MORNING CIGS AND TIMING OF -TSRA THIS
AFTERNOON. HIGH ALL OTHER ELEMENTS.
39
&&
.PRELIMINARY POINT TEMPS/POPS...
ATHENS 83 69 87 70 / 50 40 30 20
ATLANTA 84 71 87 71 / 60 40 30 20
BLAIRSVILLE 79 65 83 64 / 60 40 30 20
CARTERSVILLE 85 68 88 70 / 60 40 30 20
COLUMBUS 88 72 90 72 / 50 40 30 20
GAINESVILLE 82 69 85 69 / 60 40 30 20
MACON 87 71 90 71 / 50 40 30 20
ROME 86 67 89 70 / 60 40 30 20
PEACHTREE CITY 85 68 87 69 / 50 40 30 20
VIDALIA 90 72 90 72 / 50 40 30 20
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH FROM NOON EDT TODAY THROUGH THIS EVENING FOR
THE FOLLOWING ZONES: BALDWIN...BIBB...BLECKLEY...CHATTAHOOCHEE...
CRAWFORD...CRISP...DODGE...DOOLY...EMANUEL...GLASCOCK...
HANCOCK...HOUSTON...JEFFERSON...JOHNSON...JONES...LAURENS...
MACON...MARION...MONTGOMERY...PEACH...PULASKI...SCHLEY...
STEWART...SUMTER...TAYLOR...TELFAIR...TOOMBS...TREUTLEN...
TWIGGS...WARREN...WASHINGTON...WEBSTER...WHEELER...WILCOX...
WILKINSON.
&&
$$
SHORT TERM...39
LONG TERM....01
AVIATION...39
AREA FORECAST DISCUSSION
NWS POCATELLO ID
910 AM MDT WED AUG 21 2013
.UPDATE...QUITE A BIT OF UNCERTAINTY REMAINS WITH TODAYS FORECAST.
SHORTWAVE OVER NORTHEAST NEVADA SLOWLY SHEARING NORTHEAST THROUGH
EASTERN IDAHO TODAY WITH LONG BAND OF MOSTLY WEAK CONVECTION
SPREAD WEST TO EAST ACROSS THE FORECAST AREA AND AN OCCASSIONAL
LIGHTNING STRIKE IN SOUTHEAST CORNER. VERY MOIST AIR MASS IN PLACE
WITH UPSTREAM SOUNDING PWAT AROUND ONE INCH AND NAM PWAT WELL OVER
AN INCH BY AFTERNOON. WV SAT IMAGERY SHOWS THAT MOISTURE HAS
PUSHED THROUGH NEARLY THE ENTIRE FORECAST AREA THOUGH NAM MODEL
PWAT CONSIDERABLY LESS AGGRESSIVE OVER PORTIONS OF THE CENTRAL
MOUNTAINS...WHICH HAS BEEN THE THEME FROM THE MODEL THE PAST
SEVERAL DAYS. NAM-BASED LOCAL WRF SPREADS AFTERNOON INSTABILITY
INTO THE CENTRAL MOUNTAINS WITH POCKET OF LIGHT QPF FROM ROUGHLY
KSUN NORTHEAST...BUT CANT QUITE PUSH THE INSTABILITY FURTHER
NORTH. LATEST HRRR SEEMS TO FOLLOW WITH THIS SOLUTION AS WELL WITH
QPF IN NEARLY THE SAME LOCATION. CLOUD COVER FROM CURRENT
CONVECTION MAY BE THE LIMITING FACTOR BUT NORTH HALF OF FORECAST
AREA CLEAR OTHER THAN SMOKE SO SHOULD BE NO HINDERANCE TO VERTICAL
DEVELOPMENT. ALREADY HAD MULTIPLE LIGHTNING STARTS EVEN OUTSIDE
OF HEAVY RAINFALL CORES WITH CONVECTION IN SOUTHERN HIGHLANDS
YESTERDAY SO HAVE A DIFFICULT TIME JUSTIFYING ANY CHANGE IN
THUNDERSTORM COVERAGE OR WITH CURRENT RED FLAG HEADLINES. WILL
MAINTAIN A WATCH AND SEE STANCE...AND STILL OPEN TO FLASH FLOOD
WATCH LATER TODAY FOR SOUTHERN AND PORTIONS OF EASTERN HIGHLANDS
DEPENDING ON DEVELOPMENT. DMH
&&
.PREV DISCUSSION... /ISSUED 213 AM MDT WED AUG 21 2013/
DISCUSSION...A CLOSED LOW OFF THE COAST OF CENTRAL CALIFORNIA IS
PUMPING MONSOONAL MOISTURE INTO THE REGION. NAM/GFS IS SHOWING
BETTER CHANCES FOR STORMS TODAY OVER THE SOUTHEAST HIGHLANDS
WHERE AN UPPER LEVEL VORTICITY MAXIMUM WILL TRACK. SOME STORMS
WILL BE POSSIBLE ELSEWHERE BECAUSE OF THE HIGH MOISTURE CONTENT
OVER THE AREA. CENTRAL MOUNTAINS WILL SEE ISOLATED TO SCATTERED
STORMS TODAY...TOPOGRAPHY MAY AID DEVELOPMENT THERE. HIGH
PRECIPITABLE WATER VALUES OF 0.75 TO 1.15 SUGGEST AN ISOLATED
FLASH FLOOD THREAT ESPECIALLY OVER THE EASTERN HIGHLANDS. ON
THURSDAY THE CLOSED LOW LIFTS INTO OREGON. THIS WILL SHIFT THE
BEST CHANCE FOR STORMS INTO THE CENTRAL MOUNTAINS ALONG WITH THE
FLASH FLOOD THREAT. PRECIPITABLE WATER VALUES DO NOT CHANGE MUCH.
GIVEN THE RECENT FIRE SCARS IN THE CENTRAL MOUNTAINS...A FLASH
FLOOD THREAT INCLUDING MUDSLIDES IS MORE POSSIBLE. LATER SHIFTS
MAY NEED TO REEVALUATE FOR A POSSIBLE FLASH FLOOD WATCH OVER THE
CENTRAL MOUNTAINS FOR THURSDAY. ON FRIDAY THE LOW WEAKENS AND
LIFTS INTO MONTANA. ENOUGH MOISTURE WILL REMAIN OVER THE AREA FOR
FRIDAY AND THROUGH THE WEEKEND TO PRODUCE ISOLATED THUNDERSTORMS.
MOIST ATMOSPHERE PERSISTS INTO EARLY NEXT WEEK WITH THE GFS
SUGGESTING ANOTHER STRONG PUSH OF MONSOONAL MOISTURE.
VALLE
AVIATION...SMOKE WILL LIKELY IMPACT KSUN ONCE AGAIN THIS MORNING.
MOISTURE IS WORKING ITS WAY NORTH TODAY BRINGING SHOWERS AND
THUNDERSTORMS TO THE ENTIRE AREA. HAVE VCTS PRESENT FOR ALL SITES
THIS AFTERNOON WITH THE POSSIBILITY OF THUNDERSTORMS ON SITE. EXPECT
MORE WIDESPREAD THUNDERSTORM ACTIVITY ON THURSDAY. EP/DV
FIRE WEATHER...MONSOON MOISTURE IS MOVING IN TO THE AREA FROM THE
SOUTH BRINGING ISOLATED TO SCATTERED THUNDERSTORMS
TODAY...ESPECIALLY IN THE SOUTHERN AND EASTERN HIGHLANDS. MODELS
SHOWING PWAT VALUES OVER ONE INCH IN MANY AREAS WHICH LENDS TO THE
THREAT OF HEAVY RAINFALL CAUSING FLASH FLOODING...ESPECIALLY OVER
BURN SCARS. GUSTY WINDS UNDER AND NEAR THUNDERSTORMS IS POSSIBLE AS
WELL. EXCEPTING A REPEAT ON THURSDAY WITH MORE WIDESPREAD AND
SCATTERED THUNDERSTORMS...WITH THE THREAT OF GUSTY WINDS AND
FLASH FLOODING. A RED FLAG WARNING IS IN EFFECT FOR BOTH WEDNESDAY
AND THURSDAY FOR ALL SE IDAHO FIRE WEATHER ZONES EXCEPT 411 FOR
GUSTY OUTFLOW WINDS AND THUNDERSTORMS. ON FRIDAY... AN INCREASE IN
WINDS IS EXPECTED AS UPPER LOW MOVES ACROSS THE PANHANDLE OF IDAHO.
EP/DV
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL MIDNIGHT MDT THURSDAY NIGHT IDZ410.
RED FLAG WARNING UNTIL MIDNIGHT MDT THURSDAY NIGHT IDZ413-427.
RED FLAG WARNING UNTIL MIDNIGHT MDT THURSDAY NIGHT
IDZ422-475-476.
RED FLAG WARNING UNTIL MIDNIGHT MDT THURSDAY NIGHT IDZ425.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1100 AM CDT WED AUG 21 2013
.DISCUSSION...
625 AM CDT
HAVE UPDATED THE FORECAST EARLY THIS MORNING TO ACCOUNT FOR MORE
MORNING AND EARLY AFTERNOON CLOUD COVER. WHAT IS LEFT OF A SHEARED
OUT SHORT WAVE ON WATER VAPOR CENTERED ACROSS WI IS HELPING TO
CAUSE ENOUGH ASCENT AND FOCUS FOR 5000-8000 FT CLOUDS ACROSS
NORTHERN IL AND WI. THE RAP 750-850MB CAPTURES THE RH DEPICTION
PRETTY WELL...AND THE SPC WRF COLUMN CONDENSATE DOES TOO ALTHOUGH
A BIT LATE WITH IT. BOTH SHOW INDICATIONS OF THE CLOUDS STICKING
AROUND INTO THIS AFTERNOON AND WITH THE SLOW MOVEMENT OF THE
SHEARED WAVE THAT SEEMS MORE PLAUSIBLE THAN EARLIER. SO HAVE
BUMPED UP SKY COVER QUITE A BIT AND EASED THE TEMPERATURE CLIMB
ALONG WITH BUMPING DOWN HIGHS 2-4 DEGREES IN THE NORTHERN HALF OF
THE AREA. ITS POSSIBLE MORE MAY NEED TO BE PEELED AWAY IF CLOUDS
ARE THICK ENOUGH. CONFIDENCE IS NOT THAT HIGH ON HOW THICK THE
CLOUDS WILL REMAIN AS RAP DIAGNOSTIC SOUNDINGS INDICATE THE RH TO
BE FAIRLY SHALLOW. EVEN IF SCATTERED AT TIMES THOUGH IT LIKELY
WILL SLOW THE TEMPERATURE JUMP...SO FELT ENOUGH CONFIDENCE TO
LOWER THEM SOME.
MTF
//PREV DISCUSSION...
328 AM CDT
THE FORECAST FOCUS WAS FIRST ON THE CHANCES FOR STORMS TONIGHT AND
MAINLY EARLY THU...WHICH EVEN THOUGH THE COVERAGE IS NOT EXPECTED
TO BE PARTICULARLY HIGH THIS IS THE BEST CHANCE FOR RAIN IN OVER A
WEEK. THEN ATTENTION TURNED TO TEMPERATURES WITH LIKELY 90 TODAY
IN MANY COMMUNITIES...THEN A SHORT TERM COOL DOWN FOLLOWED BY AN
APPRECIABLE WARM UP INTO THE FINAL WEEK OF METEOROLOGICAL SUMMER
/ALREADY???/.
TODAY...WHAT HAS BEEN A STAGNANT BUT VERY PLEASANT PATTERN OVER
THE REGION IS BEGINNING TO SHOW SOME SHIFTING EARLY THIS
MORNING...WITH WATER VAPOR SHOWING A STRONG 110 KT+ JET ACROSS FAR
SOUTHERN CANADA BUCKLING SLIGHTLY INTO THE UPPER MIDWEST. MULTIPLE
SHORT WAVES ARE NOTED ACROSS THE NORTHERN ROCKIES AND UPPER
MIDWEST ON THE LEADING EDGE OF THE IMPINGING UPPER TROUGH. AREA
SOUNDINGS LAST EVENING AND VARIOUS SATELLITE CHANNELS CONTINUE TO
INDICATE A FAIRLY DRY MID LEVEL AIR MASS OVER OUR AREA WHICH WILL
TAKE TIME TO SATURATE...SO NOT EXPECTING BLOWOFF FROM ANY MORNING
CONVECTION TO THE NORTHWEST TO REALLY SPREAD OVER WITH ONLY SOME
CUMULUS THROUGH EARLY AFTERNOON. THE THERMAL RIDGE AT 850-925MB IN
ADVANCE OF THE TROUGH LEANS ESE TODAY OVER THE AREA AND THESE
VALUES DO SUPPORT 90 ABOUT A QUARTER OF THE TIME BASED ON LOCAL
CLIMATOLOGY. GIVEN LOCAL HIGHS YESTERDAY AT 87-88 IN MOST
PLACES...UPSTREAM HIGHS IN CENTRAL IA WERE AT 90...AND WITH OUR
DRYING GROUND OFFERING SENSIBLE HEAT TO BE A BIGGER
FACTOR...BELIEVE 88 TO 92 SHOULD PREVAIL ACROSS MUCH OF THE AREA.
DEW POINTS FAVORED IN THE MID TO UPPER 60S WILL ALLOW FOR HEAT
INDEX READINGS TO INCH INTO THE MID 90S IN A SOME COMMUNITIES.
TONIGHT INTO THU MORNING...AS PRIMARY HEIGHT FALLS DEVELOP EAST
ACROSS ONTARIO...THE DEVELOPING SURFACE LOW WILL TRACK EAST UP
THERE...WITH A WEAK SECONDARY LOW /1011MB OR SO/ FAVORED IN
GUIDANCE TO MOVE ALONG THE FRONT FROM IA TO CENTRAL LAKE MI
TONIGHT. THIS FEATURE ALONG WITH THE UPPER TO MID JET TURNING MORE
NORTHWEST GIVING THE FRONT A GOOD PUSH SOUTHWARD ACROSS THE AREA
ON THU. SOME GUIDANCE INDICATES CONVECTION INTO THE AREA THIS
EVE...BUT THAT JUST SEEMS TO QUICK GIVEN THE DRY RH AND LIMITED
MOISTURE TRANSPORT IN ADVANCE OF THE SYSTEM. THE FOCUS OF THE
BOUNDARY CONVERGENCE WILL BE IN WI LATE AFTERNOON AND EVE WITH
SCATTERED POSSIBLY STRONG CONVECTION EXPECTED THERE. GIVEN HIGH
INSTABILITY AND ASSOCIATED DCAPE VALUES UPSTREAM A FEW CLUSTERS
MAY MAKE QUICK PROGRESS SE BY MID TO LATE EVE INTO
OVERNIGHT...ESPECIALLY IF OVER THE LAKE. BUT AGAIN COVERAGE LOOKS
SCATTERED. THIS SYSTEM HAS THE MAKINGS OF A LATE SUMMER FRONT BY
OVERNIGHT WITH WEAKENING SURFACE PRESSURES ALONG IT IN THE WAKE OF
THE AFOREMENTIONED LOW...WEAKENING WARM AIR ADVECTION/DIFFERENTIAL
TEMPERATURE ADVECTION IN ADVANCE OF IT...AND AGAIN LIMITED
MOISTURE. THE DEEP LAYER SHEAR ALSO IS MARGINAL WITH VECTORS
ORIENTED POORLY FOR ANY MCS TYPE ORGANIZATION. OVERALL THE MODEL
SUITE SUPPORTS LIMITED AREAL COVERAGE OF QPF GREATER THAN 0.25 IN.
SO KEEP MAINLY CHANCE POPS EVERYWHERE TONIGHT WITH ONLY MINOR
TWEAKS TO WHAT WAS IN THERE...AND MAINTAIN THE HIGHEST OVERNIGHT.
REST OF THU AND FRI....DRY AIR AND SUPPRESSION MOVE QUICKLY
SOUTHWARD BEHIND THE SURFACE COOL FRONT...WHICH LOOKS TO MOVE
DOWN THE LAKE AND THROUGH CHICAGO SOMETIME IN THE MID-MORNING.
THIS MAY CONTINUE TO SUPPORT SCATTERED SHOWERS AND SOME STORMS
ALONG IT...SO MAINTAIN POPS ESPECIALLY FOR THE SOUTHERN CWA
THROUGH THE DAY. THE PATTERN SUPPORTS TEMPS LIKELY FALLING ALONG
THE LAKE SHORE BY LATE MORNING INTO EARLY AFTERNOON AND REACHING
THEIR PEAK IN OUTLYING AREAS EARLY IN THE AFTERNOON AND THEN
HOLDING STEADY. DRIER AIR REALLY WORKS ITS WAY IN WITHIN THE LOW-
LEVELS THU NIGHT. WITH MOSTLY SUNNY CONDITIONS FRI THIS SHOULD
SUPPORT GOOD MIXING OUT WITH RELATIVE HUMIDITY EXPECTED TO DROP TO
AROUND 30 PERCENT FRI AFTERNOON...AN EARLY SIGN THAT THE NEXT
SEASON IS INDEED NOT FAR AWAY. WITH 850MB TEMPERATURES IN THE MID
TEENS...TEMPS ON FRI LOOK TO BE IN THE MID 70S TO LOWER 80S. FRI
NIGHT SHOULD BE THE COOLEST WITH HIGH PRESSURE STILL PRIMARILY
INFLUENCING THE AREA AND LITTLE CIRRUS EXPECTED. WHILE DEW POINTS
IN THE 40S ARE LIKELY DURING FRI AFTERNOON...THESE SHOULD COME
BACK INTO THE EVE AND LOWS RIGHT NOW LOOK TO BOTTOM OUT IN THE
LOWER TO MID 50S IN MOST OUTLYING LOCATIONS.
BEYOND...THE UPPER RIDGE LOOKS TO BUILD BACK NORTHEAST AS THE
WEEKEND PROGRESSES AND INTO NEXT WEEK...SUPPORTING WARMING
TEMPS AS WELL AS LIKELY PRECIP-FREE CONDITIONS WITH THE FOCUS OF
SYSTEMS AGAIN SHIFTING NORTHWARD. WHILE 90 DEGREES OR WARMER LOOKS
POSSIBLE ON MULTIPLE DAYS WITH MID TO UPPER 60S DEW POINTS...THE
SIGNAL IS STRONGEST ON MON AND TUE WITH THEN SOME BUCKLING DUE TO
POSSIBLE SHORT WAVES/UPSTREAM STORMS. HAVE BLENDED BIAS-
CORRECTED DATA FROM MODELS INTO THE GOING FORECAST WHICH SUPPORTS
WARMER TEMPS THAN A STRAIGHT MODEL BLEND.
MTF
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 16Z...
* CHANCE OF SHRA/TSRA EARLY THURSDAY MORNING AND WIND SHIFT
ASSOCIATED WITH A COLD FRONT PASSAGE.
* CHANCE OF MVFR CIGS THURSDAY MORNING BEHIND COLD FRONT.
KREIN
//DISCUSSION...UPDATED 12Z...
OVERALL EXPECT A FAIRLY QUIET DAY LOCALLY DOMINATED BY SOUTHWEST
WINDS AND VFR CONDITIONS. GUSTS INTO THE MID TO HIGH TEENS CAN BE
EXPECTED LATE THIS MORNING AND INTO THIS EVENING AHEAD OF AN
APPROACHING COLD FRONT. BY 18Z THIS AFTERNOON...EXPECT THE FRONT TO
STRETCH FROM ROUGHLY DLH SOUTHWEST TO FSD WITH MODERATE TO STRONG
INSTABILITY DEVELOPING AHEAD OF THE FRONT ACROSS PORTIONS OF
SOUTHERN MINNESOTA AND CENTRAL WISCONSIN...WHERE CONVECTIVE
INITIATION IS EXPECTED TO TAKE PLACE BY EARLY TO MID AFTERNOON. SOME
CONVECTIVE ALLOWING MODELS ARE SHOWING THUNDERSTORMS DEVELOPING
FARTHER SOUTHEAST...OVER NORTH CENTRAL ILLINOIS AND SOUTHERN
WISCONSIN...BUT EXPECT THIS AREA TO BE MOSTLY CAPPED WITH VERY
ISOLATED ACTIVITY IF ANY.
THE FRONT IS NOT EXPECTED TO PASS INTO ILLINOIS UNTIL AROUND 09Z
TONIGHT..AND INTO THE TERMINALS A COUPLE HOURS THEREAFTER. BY THIS
TIME...EXPECT THUNDERSTORMS PUSHING WELL AHEAD OF THE FRONT AND
INTENSITY TO BE ON A DECLINING TREND GIVEN THE UNFAVORABLE DIURNAL
TIMING AND THE LACK OF ANY SIGNIFICANT UPPER LEVEL SUPPORT. COVERAGE
SHOULD BECOME MORE WIDELY SCATTERED AS THE OVERNIGHT HOURS PROGRESS
LEADING TO UNCERTAINTY IN IMPACTS AT THE TERMINALS. IN FACT SOME
CAMS SUGGEST THAT ACTIVITY MAY DIMINISH COMPLETELY OVER NORTHERN
ILLINOIS...THEN REFORM SOUTH OF THE TERMINALS TOMORROW.
ONCE THE FRONT PASSES THROUGH...THERE MAY BE A BRIEF WINDOW IN THE
MORNING WHERE LOWER MFVR CIGS DEVELOP BEHIND THE FRONT AS THE COOLER
AIR PUSHES INTO THE UPPER 60 DEWPOINTS...BUT SHOULD BE ON THE ORDER
OF AN HOUR OR TWO BEFORE DRIER AIR STARTS TO TRICKLE SOUTH AND
DAYTIME MIXING COMMENCES. WINDS ARE EXPECTED TO BECOME NORTHEASTERLY
AS HIGH PRESSURE BUILDS ACROSS MINNESOTA AND WISCONSIN.
BMD
//ORD AND MDW CONFIDENCE...UPDATED 16Z...
* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH THE EARLY
OVERNIGHT HOURS.
* MEDIUM TO HIGH CONFIDENCE IN AT LEAST WIDELY SCATTERED TSRA
MOVING INTO THE AREA LATE TONIGHT/EARLY THURSDAY.
* MEDIUM CONFIDENCE IN TIMING FRONTAL WIND SHIFT EARLY THURSDAY.
* LOW CONFIDENCE IN MVFR CIGS BEHIND THE FRONT EARLY THURSDAY.
KREIN
//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...
THURSDAY NIGHT THROUGH MONDAY...VFR.
TUESDAY...SLT CHC TSRA.
BMD
&&
.MARINE...
237 AM CDT
SOUTHWEST WINDS TO AROUND 25 KT WILL CONTINUE THROUGH THE DAY TODAY
ACROSS NORTHERN LAKE MICHIGAN AHEAD OF AN APPROACHING COLD FRONT
WHICH CURRENTLY STRETCHES FROM SOUTHERN MANITOBA INTO THE DAKOTAS.
WINDS WILL BE A LITTLE WEAKER ON THE SOUTH END OF THE LAKE WHERE THE
GRADIENT ISNT QUITE AS TIGHT. STABLE CONDITIONS ARE EXPECTED OVER
THE LAKE WHICH WILL HELP KEEP HIGHER END GUSTS IN CHECK...THOUGH
WOULDNT BE SURPRISED TO SEE SHIPS REPORT OCCASIONAL GUSTS TO 30
KTS. WINDS TURN NORTHERLY LATE TONIGHT AND EARLY THURSDAY...WITH
GUSTS AROUND 25 KT MAINTAINING ACROSS THE SOUTH HALF OF THE LAKE.
WINDS BEGIN TO TAPER THURSDAY EVENING AS HIGH PRESSURE BUILDS
ACROSS THE WESTERN LAKES REGION. WINDS WILL TURN SOUTHERLY AGAIN
SATURDAY AS ANOTHER LOW PRESSURE SYSTEM MOVES ACROSS THE CANADIAN
PRAIRIES...AND FRESHEN UP ESPECIALLY ON SUNDAY WHEN WE MAY ONCE
AGAIN BE LOOKING AT 20 TO 25 KT WINDS.
BMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)
FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
902 AM CDT WED AUG 21 2013
.DISCUSSION...
625 AM CDT
HAVE UPDATED THE FORECAST EARLY THIS MORNING TO ACCOUNT FOR MORE
MORNING AND EARLY AFTERNOON CLOUD COVER. WHAT IS LEFT OF A SHEARED
OUT SHORT WAVE ON WATER VAPOR CENTERED ACROSS WI IS HELPING TO
CAUSE ENOUGH ASCENT AND FOCUS FOR 5000-8000 FT CLOUDS ACROSS
NORTHERN IL AND WI. THE RAP 750-850MB CAPTURES THE RH DEPICTION
PRETTY WELL...AND THE SPC WRF COLUMN CONDENSATE DOES TOO ALTHOUGH
A BIT LATE WITH IT. BOTH SHOW INDICATIONS OF THE CLOUDS STICKING
AROUND INTO THIS AFTERNOON AND WITH THE SLOW MOVEMENT OF THE
SHEARED WAVE THAT SEEMS MORE PLAUSIBLE THAN EARLIER. SO HAVE
BUMPED UP SKY COVER QUITE A BIT AND EASED THE TEMPERATURE CLIMB
ALONG WITH BUMPING DOWN HIGHS 2-4 DEGREES IN THE NORTHERN HALF OF
THE AREA. ITS POSSIBLE MORE MAY NEED TO BE PEELED AWAY IF CLOUDS
ARE THICK ENOUGH. CONFIDENCE IS NOT THAT HIGH ON HOW THICK THE
CLOUDS WILL REMAIN AS RAP DIAGNOSTIC SOUNDINGS INDICATE THE RH TO
BE FAIRLY SHALLOW. EVEN IF SCATTERED AT TIMES THOUGH IT LIKELY
WILL SLOW THE TEMPERATURE JUMP...SO FELT ENOUGH CONFIDENCE TO
LOWER THEM SOME.
MTF
//PREV DISCUSSION...
328 AM CDT
THE FORECAST FOCUS WAS FIRST ON THE CHANCES FOR STORMS TONIGHT AND
MAINLY EARLY THU...WHICH EVEN THOUGH THE COVERAGE IS NOT EXPECTED
TO BE PARTICULARLY HIGH THIS IS THE BEST CHANCE FOR RAIN IN OVER A
WEEK. THEN ATTENTION TURNED TO TEMPERATURES WITH LIKELY 90 TODAY
IN MANY COMMUNITIES...THEN A SHORT TERM COOL DOWN FOLLOWED BY AN
APPRECIABLE WARM UP INTO THE FINAL WEEK OF METEOROLOGICAL SUMMER
/ALREADY???/.
TODAY...WHAT HAS BEEN A STAGNANT BUT VERY PLEASANT PATTERN OVER
THE REGION IS BEGINNING TO SHOW SOME SHIFTING EARLY THIS
MORNING...WITH WATER VAPOR SHOWING A STRONG 110 KT+ JET ACROSS FAR
SOUTHERN CANADA BUCKLING SLIGHTLY INTO THE UPPER MIDWEST. MULTIPLE
SHORT WAVES ARE NOTED ACROSS THE NORTHERN ROCKIES AND UPPER
MIDWEST ON THE LEADING EDGE OF THE IMPINGING UPPER TROUGH. AREA
SOUNDINGS LAST EVENING AND VARIOUS SATELLITE CHANNELS CONTINUE TO
INDICATE A FAIRLY DRY MID LEVEL AIR MASS OVER OUR AREA WHICH WILL
TAKE TIME TO SATURATE...SO NOT EXPECTING BLOWOFF FROM ANY MORNING
CONVECTION TO THE NORTHWEST TO REALLY SPREAD OVER WITH ONLY SOME
CUMULUS THROUGH EARLY AFTERNOON. THE THERMAL RIDGE AT 850-925MB IN
ADVANCE OF THE TROUGH LEANS ESE TODAY OVER THE AREA AND THESE
VALUES DO SUPPORT 90 ABOUT A QUARTER OF THE TIME BASED ON LOCAL
CLIMATOLOGY. GIVEN LOCAL HIGHS YESTERDAY AT 87-88 IN MOST
PLACES...UPSTREAM HIGHS IN CENTRAL IA WERE AT 90...AND WITH OUR
DRYING GROUND OFFERING SENSIBLE HEAT TO BE A BIGGER
FACTOR...BELIEVE 88 TO 92 SHOULD PREVAIL ACROSS MUCH OF THE AREA.
DEW POINTS FAVORED IN THE MID TO UPPER 60S WILL ALLOW FOR HEAT
INDEX READINGS TO INCH INTO THE MID 90S IN A SOME COMMUNITIES.
TONIGHT INTO THU MORNING...AS PRIMARY HEIGHT FALLS DEVELOP EAST
ACROSS ONTARIO...THE DEVELOPING SURFACE LOW WILL TRACK EAST UP
THERE...WITH A WEAK SECONDARY LOW /1011MB OR SO/ FAVORED IN
GUIDANCE TO MOVE ALONG THE FRONT FROM IA TO CENTRAL LAKE MI
TONIGHT. THIS FEATURE ALONG WITH THE UPPER TO MID JET TURNING MORE
NORTHWEST GIVING THE FRONT A GOOD PUSH SOUTHWARD ACROSS THE AREA
ON THU. SOME GUIDANCE INDICATES CONVECTION INTO THE AREA THIS
EVE...BUT THAT JUST SEEMS TO QUICK GIVEN THE DRY RH AND LIMITED
MOISTURE TRANSPORT IN ADVANCE OF THE SYSTEM. THE FOCUS OF THE
BOUNDARY CONVERGENCE WILL BE IN WI LATE AFTERNOON AND EVE WITH
SCATTERED POSSIBLY STRONG CONVECTION EXPECTED THERE. GIVEN HIGH
INSTABILITY AND ASSOCIATED DCAPE VALUES UPSTREAM A FEW CLUSTERS
MAY MAKE QUICK PROGRESS SE BY MID TO LATE EVE INTO
OVERNIGHT...ESPECIALLY IF OVER THE LAKE. BUT AGAIN COVERAGE LOOKS
SCATTERED. THIS SYSTEM HAS THE MAKINGS OF A LATE SUMMER FRONT BY
OVERNIGHT WITH WEAKENING SURFACE PRESSURES ALONG IT IN THE WAKE OF
THE AFOREMENTIONED LOW...WEAKENING WARM AIR ADVECTION/DIFFERENTIAL
TEMPERATURE ADVECTION IN ADVANCE OF IT...AND AGAIN LIMITED
MOISTURE. THE DEEP LAYER SHEAR ALSO IS MARGINAL WITH VECTORS
ORIENTED POORLY FOR ANY MCS TYPE ORGANIZATION. OVERALL THE MODEL
SUITE SUPPORTS LIMITED AREAL COVERAGE OF QPF GREATER THAN 0.25 IN.
SO KEEP MAINLY CHANCE POPS EVERYWHERE TONIGHT WITH ONLY MINOR
TWEAKS TO WHAT WAS IN THERE...AND MAINTAIN THE HIGHEST OVERNIGHT.
REST OF THU AND FRI....DRY AIR AND SUPPRESSION MOVE QUICKLY
SOUTHWARD BEHIND THE SURFACE COOL FRONT...WHICH LOOKS TO MOVE
DOWN THE LAKE AND THROUGH CHICAGO SOMETIME IN THE MID-MORNING.
THIS MAY CONTINUE TO SUPPORT SCATTERED SHOWERS AND SOME STORMS
ALONG IT...SO MAINTAIN POPS ESPECIALLY FOR THE SOUTHERN CWA
THROUGH THE DAY. THE PATTERN SUPPORTS TEMPS LIKELY FALLING ALONG
THE LAKE SHORE BY LATE MORNING INTO EARLY AFTERNOON AND REACHING
THEIR PEAK IN OUTLYING AREAS EARLY IN THE AFTERNOON AND THEN
HOLDING STEADY. DRIER AIR REALLY WORKS ITS WAY IN WITHIN THE LOW-
LEVELS THU NIGHT. WITH MOSTLY SUNNY CONDITIONS FRI THIS SHOULD
SUPPORT GOOD MIXING OUT WITH RELATIVE HUMIDITY EXPECTED TO DROP TO
AROUND 30 PERCENT FRI AFTERNOON...AN EARLY SIGN THAT THE NEXT
SEASON IS INDEED NOT FAR AWAY. WITH 850MB TEMPERATURES IN THE MID
TEENS...TEMPS ON FRI LOOK TO BE IN THE MID 70S TO LOWER 80S. FRI
NIGHT SHOULD BE THE COOLEST WITH HIGH PRESSURE STILL PRIMARILY
INFLUENCING THE AREA AND LITTLE CIRRUS EXPECTED. WHILE DEW POINTS
IN THE 40S ARE LIKELY DURING FRI AFTERNOON...THESE SHOULD COME
BACK INTO THE EVE AND LOWS RIGHT NOW LOOK TO BOTTOM OUT IN THE
LOWER TO MID 50S IN MOST OUTLYING LOCATIONS.
BEYOND...THE UPPER RIDGE LOOKS TO BUILD BACK NORTHEAST AS THE
WEEKEND PROGRESSES AND INTO NEXT WEEK...SUPPORTING WARMING
TEMPS AS WELL AS LIKELY PRECIP-FREE CONDITIONS WITH THE FOCUS OF
SYSTEMS AGAIN SHIFTING NORTHWARD. WHILE 90 DEGREES OR WARMER LOOKS
POSSIBLE ON MULTIPLE DAYS WITH MID TO UPPER 60S DEW POINTS...THE
SIGNAL IS STRONGEST ON MON AND TUE WITH THEN SOME BUCKLING DUE TO
POSSIBLE SHORT WAVES/UPSTREAM STORMS. HAVE BLENDED BIAS-
CORRECTED DATA FROM MODELS INTO THE GOING FORECAST WHICH SUPPORTS
WARMER TEMPS THAN A STRAIGHT MODEL BLEND.
MTF
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 12Z...
* CHANCE OF SHRA/TSRA EARLY THURSDAY MORNING AND WIND SHIFT
ASSOCIATED WITH A COLD FRONT PASSAGE.
* POTENTIAL FOR MVFR CIGS THURSDAY MORNING BEHIND COLD FRONT.
KREIN
//DISCUSSION...UPDATED 12Z...
OVERALL EXPECT A FAIRLY QUIET DAY LOCALLY DOMINATED BY SOUTHWEST
WINDS AND VFR CONDITIONS. GUSTS INTO THE MID TO HIGH TEENS CAN BE
EXPECTED LATE THIS MORNING AND INTO THIS EVENING AHEAD OF AN
APPROACHING COLD FRONT. BY 18Z THIS AFTERNOON...EXPECT THE FRONT TO
STRETCH FROM ROUGHLY DLH SOUTHWEST TO FSD WITH MODERATE TO STRONG
INSTABILITY DEVELOPING AHEAD OF THE FRONT ACROSS PORTIONS OF
SOUTHERN MINNESOTA AND CENTRAL WISCONSIN...WHERE CONVECTIVE
INITIATION IS EXPECTED TO TAKE PLACE BY EARLY TO MID AFTERNOON. SOME
CONVECTIVE ALLOWING MODELS ARE SHOWING THUNDERSTORMS DEVELOPING
FARTHER SOUTHEAST...OVER NORTH CENTRAL ILLINOIS AND SOUTHERN
WISCONSIN...BUT EXPECT THIS AREA TO BE MOSTLY CAPPED WITH VERY
ISOLATED ACTIVITY IF ANY.
THE FRONT IS NOT EXPECTED TO PASS INTO ILLINOIS UNTIL AROUND 09Z
TONIGHT..AND INTO THE TERMINALS A COUPLE HOURS THEREAFTER. BY THIS
TIME...EXPECT THUNDERSTORMS PUSHING WELL AHEAD OF THE FRONT AND
INTENSITY TO BE ON A DECLINING TREND GIVEN THE UNFAVORABLE DIURNAL
TIMING AND THE LACK OF ANY SIGNIFICANT UPPER LEVEL SUPPORT. COVERAGE
SHOULD BECOME MORE WIDELY SCATTERED AS THE OVERNIGHT HOURS PROGRESS
LEADING TO UNCERTAINTY IN IMPACTS AT THE TERMINALS. IN FACT SOME
CAMS SUGGEST THAT ACTIVITY MAY DIMINISH COMPLETELY OVER NORTHERN
ILLINOIS...THEN REFORM SOUTH OF THE TERMINALS TOMORROW.
ONCE THE FRONT PASSES THROUGH...THERE MAY BE A BRIEF WINDOW IN THE
MORNING WHERE LOWER MFVR CIGS DEVELOP BEHIND THE FRONT AS THE COOLER
AIR PUSHES INTO THE UPPER 60 DEWPOINTS...BUT SHOULD BE ON THE ORDER
OF AN HOUR OR TWO BEFORE DRIER AIR STARTS TO TRICKLE SOUTH AND
DAYTIME MIXING COMMENCES. WINDS ARE EXPECTED TO BECOME NORTHEASTERLY
AS HIGH PRESSURE BUILDS ACROSS MINNESOTA AND WISCONSIN.
BMD
//ORD AND MDW CONFIDENCE...UPDATED 14Z...
* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH THE EARLY
OVERNIGHT HOURS.
* MEDIUM TO HIGH CONFIDENCE IN AT LEAST WIDELY SCATTERED TSRA
MOVING INTO THE AREA LATE TONIGHT/EARLY THURSDAY.
* MEDIUM CONFIDENCE IN TIMING FRONTAL WIND SHIFT EARLY THURSDAY.
* LOW CONFIDENCE IN MVFR CIGS BEHIND THE FRONT EARLY THURSDAY.
KREIN
//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...
THURSDAY NIGHT THROUGH MONDAY...VFR.
TUESDAY...SLT CHC TSRA.
BMD
&&
.MARINE...
237 AM CDT
SOUTHWEST WINDS TO AROUND 25 KT WILL CONTINUE THROUGH THE DAY TODAY
ACROSS NORTHERN LAKE MICHIGAN AHEAD OF AN APPROACHING COLD FRONT
WHICH CURRENTLY STRETCHES FROM SOUTHERN MANITOBA INTO THE DAKOTAS.
WINDS WILL BE A LITTLE WEAKER ON THE SOUTH END OF THE LAKE WHERE THE
GRADIENT ISNT QUITE AS TIGHT. STABLE CONDITIONS ARE EXPECTED OVER
THE LAKE WHICH WILL HELP KEEP HIGHER END GUSTS IN CHECK...THOUGH
WOULDNT BE SURPRISED TO SEE SHIPS REPORT OCCASIONAL GUSTS TO 30
KTS. WINDS TURN NORTHERLY LATE TONIGHT AND EARLY THURSDAY...WITH
GUSTS AROUND 25 KT MAINTAINING ACROSS THE SOUTH HALF OF THE LAKE.
WINDS BEGIN TO TAPER THURSDAY EVENING AS HIGH PRESSURE BUILDS
ACROSS THE WESTERN LAKES REGION. WINDS WILL TURN SOUTHERLY AGAIN
SATURDAY AS ANOTHER LOW PRESSURE SYSTEM MOVES ACROSS THE CANADIAN
PRAIRIES...AND FRESHEN UP ESPECIALLY ON SUNDAY WHEN WE MAY ONCE
AGAIN BE LOOKING AT 20 TO 25 KT WINDS.
BMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)
FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
641 AM CDT WED AUG 21 2013
.DISCUSSION...
625 AM CDT
HAVE UPDATED THE FORECAST EARLY THIS MORNING TO ACCOUNT FOR MORE
MORNING AND EARLY AFTERNOON CLOUD COVER. WHAT IS LEFT OF A SHEARED
OUT SHORT WAVE ON WATER VAPOR CENTERED ACROSS WI IS HELPING TO
CAUSE ENOUGH ASCENT AND FOCUS FOR 5000-8000 FT CLOUDS ACROSS
NORTHERN IL AND WI. THE RAP 750-850MB CAPTURES THE RH DEPICTION
PRETTY WELL...AND THE SPC WRF COLUMN CONDENSATE DOES TOO ALTHOUGH
A BIT LATE WITH IT. BOTH SHOW INDICATIONS OF THE CLOUDS STICKING
AROUND INTO THIS AFTERNOON AND WITH THE SLOW MOVEMENT OF THE
SHEARED WAVE THAT SEEMS MORE PLAUSIBLE THAN EARLIER. SO HAVE
BUMPED UP SKY COVER QUITE A BIT AND EASED THE TEMPERATURE CLIMB
ALONG WITH BUMPING DOWN HIGHS 2-4 DEGREES IN THE NORTHERN HALF OF
THE AREA. ITS POSSIBLE MORE MAY NEED TO BE PEELED AWAY IF CLOUDS
ARE THICK ENOUGH. CONFIDENCE IS NOT THAT HIGH ON HOW THICK THE
CLOUDS WILL REMAIN AS RAP DIAGNOSTIC SOUNDINGS INDICATE THE RH TO
BE FAIRLY SHALLOW. EVEN IF SCATTERED AT TIMES THOUGH IT LIKELY
WILL SLOW THE TEMPERATURE JUMP...SO FELT ENOUGH CONFIDENCE TO
LOWER THEM SOME.
MTF
//PREV DISCUSSION...
328 AM CDT
THE FORECAST FOCUS WAS FIRST ON THE CHANCES FOR STORMS TONIGHT AND
MAINLY EARLY THU...WHICH EVEN THOUGH THE COVERAGE IS NOT EXPECTED
TO BE PARTICULARLY HIGH THIS IS THE BEST CHANCE FOR RAIN IN OVER A
WEEK. THEN ATTENTION TURNED TO TEMPERATURES WITH LIKELY 90 TODAY
IN MANY COMMUNITIES...THEN A SHORT TERM COOL DOWN FOLLOWED BY AN
APPRECIABLE WARM UP INTO THE FINAL WEEK OF METEOROLOGICAL SUMMER
/ALREADY???/.
TODAY...WHAT HAS BEEN A STAGNANT BUT VERY PLEASANT PATTERN OVER
THE REGION IS BEGINNING TO SHOW SOME SHIFTING EARLY THIS
MORNING...WITH WATER VAPOR SHOWING A STRONG 110 KT+ JET ACROSS FAR
SOUTHERN CANADA BUCKLING SLIGHTLY INTO THE UPPER MIDWEST. MULTIPLE
SHORT WAVES ARE NOTED ACROSS THE NORTHERN ROCKIES AND UPPER
MIDWEST ON THE LEADING EDGE OF THE IMPINGING UPPER TROUGH. AREA
SOUNDINGS LAST EVENING AND VARIOUS SATELLITE CHANNELS CONTINUE TO
INDICATE A FAIRLY DRY MID LEVEL AIR MASS OVER OUR AREA WHICH WILL
TAKE TIME TO SATURATE...SO NOT EXPECTING BLOWOFF FROM ANY MORNING
CONVECTION TO THE NORTHWEST TO REALLY SPREAD OVER WITH ONLY SOME
CUMULUS THROUGH EARLY AFTERNOON. THE THERMAL RIDGE AT 850-925MB IN
ADVANCE OF THE TROUGH LEANS ESE TODAY OVER THE AREA AND THESE
VALUES DO SUPPORT 90 ABOUT A QUARTER OF THE TIME BASED ON LOCAL
CLIMATOLOGY. GIVEN LOCAL HIGHS YESTERDAY AT 87-88 IN MOST
PLACES...UPSTREAM HIGHS IN CENTRAL IA WERE AT 90...AND WITH OUR
DRYING GROUND OFFERING SENSIBLE HEAT TO BE A BIGGER
FACTOR...BELIEVE 88 TO 92 SHOULD PREVAIL ACROSS MUCH OF THE AREA.
DEW POINTS FAVORED IN THE MID TO UPPER 60S WILL ALLOW FOR HEAT
INDEX READINGS TO INCH INTO THE MID 90S IN A SOME COMMUNITIES.
TONIGHT INTO THU MORNING...AS PRIMARY HEIGHT FALLS DEVELOP EAST
ACROSS ONTARIO...THE DEVELOPING SURFACE LOW WILL TRACK EAST UP
THERE...WITH A WEAK SECONDARY LOW /1011MB OR SO/ FAVORED IN
GUIDANCE TO MOVE ALONG THE FRONT FROM IA TO CENTRAL LAKE MI
TONIGHT. THIS FEATURE ALONG WITH THE UPPER TO MID JET TURNING MORE
NORTHWEST GIVING THE FRONT A GOOD PUSH SOUTHWARD ACROSS THE AREA
ON THU. SOME GUIDANCE INDICATES CONVECTION INTO THE AREA THIS
EVE...BUT THAT JUST SEEMS TO QUICK GIVEN THE DRY RH AND LIMITED
MOISTURE TRANSPORT IN ADVANCE OF THE SYSTEM. THE FOCUS OF THE
BOUNDARY CONVERGENCE WILL BE IN WI LATE AFTERNOON AND EVE WITH
SCATTERED POSSIBLY STRONG CONVECTION EXPECTED THERE. GIVEN HIGH
INSTABILITY AND ASSOCIATED DCAPE VALUES UPSTREAM A FEW CLUSTERS
MAY MAKE QUICK PROGRESS SE BY MID TO LATE EVE INTO
OVERNIGHT...ESPECIALLY IF OVER THE LAKE. BUT AGAIN COVERAGE LOOKS
SCATTERED. THIS SYSTEM HAS THE MAKINGS OF A LATE SUMMER FRONT BY
OVERNIGHT WITH WEAKENING SURFACE PRESSURES ALONG IT IN THE WAKE OF
THE AFOREMENTIONED LOW...WEAKENING WARM AIR ADVECTION/DIFFERENTIAL
TEMPERATURE ADVECTION IN ADVANCE OF IT...AND AGAIN LIMITED
MOISTURE. THE DEEP LAYER SHEAR ALSO IS MARGINAL WITH VECTORS
ORIENTED POORLY FOR ANY MCS TYPE ORGANIZATION. OVERALL THE MODEL
SUITE SUPPORTS LIMITED AREAL COVERAGE OF QPF GREATER THAN 0.25 IN.
SO KEEP MAINLY CHANCE POPS EVERYWHERE TONIGHT WITH ONLY MINOR
TWEAKS TO WHAT WAS IN THERE...AND MAINTAIN THE HIGHEST OVERNIGHT.
REST OF THU AND FRI....DRY AIR AND SUPPRESSION MOVE QUICKLY
SOUTHWARD BEHIND THE SURFACE COOL FRONT...WHICH LOOKS TO MOVE
DOWN THE LAKE AND THROUGH CHICAGO SOMETIME IN THE MID-MORNING.
THIS MAY CONTINUE TO SUPPORT SCATTERED SHOWERS AND SOME STORMS
ALONG IT...SO MAINTAIN POPS ESPECIALLY FOR THE SOUTHERN CWA
THROUGH THE DAY. THE PATTERN SUPPORTS TEMPS LIKELY FALLING ALONG
THE LAKE SHORE BY LATE MORNING INTO EARLY AFTERNOON AND REACHING
THEIR PEAK IN OUTLYING AREAS EARLY IN THE AFTERNOON AND THEN
HOLDING STEADY. DRIER AIR REALLY WORKS ITS WAY IN WITHIN THE LOW-
LEVELS THU NIGHT. WITH MOSTLY SUNNY CONDITIONS FRI THIS SHOULD
SUPPORT GOOD MIXING OUT WITH RELATIVE HUMIDITY EXPECTED TO DROP TO
AROUND 30 PERCENT FRI AFTERNOON...AN EARLY SIGN THAT THE NEXT
SEASON IS INDEED NOT FAR AWAY. WITH 850MB TEMPERATURES IN THE MID
TEENS...TEMPS ON FRI LOOK TO BE IN THE MID 70S TO LOWER 80S. FRI
NIGHT SHOULD BE THE COOLEST WITH HIGH PRESSURE STILL PRIMARILY
INFLUENCING THE AREA AND LITTLE CIRRUS EXPECTED. WHILE DEW POINTS
IN THE 40S ARE LIKELY DURING FRI AFTERNOON...THESE SHOULD COME
BACK INTO THE EVE AND LOWS RIGHT NOW LOOK TO BOTTOM OUT IN THE
LOWER TO MID 50S IN MOST OUTLYING LOCATIONS.
BEYOND...THE UPPER RIDGE LOOKS TO BUILD BACK NORTHEAST AS THE
WEEKEND PROGRESSES AND INTO NEXT WEEK...SUPPORTING WARMING
TEMPS AS WELL AS LIKELY PRECIP-FREE CONDITIONS WITH THE FOCUS OF
SYSTEMS AGAIN SHIFTING NORTHWARD. WHILE 90 DEGREES OR WARMER LOOKS
POSSIBLE ON MULTIPLE DAYS WITH MID TO UPPER 60S DEW POINTS...THE
SIGNAL IS STRONGEST ON MON AND TUE WITH THEN SOME BUCKLING DUE TO
POSSIBLE SHORT WAVES/UPSTREAM STORMS. HAVE BLENDED BIAS-
CORRECTED DATA FROM MODELS INTO THE GOING FORECAST WHICH SUPPORTS
WARMER TEMPS THAN A STRAIGHT MODEL BLEND.
MTF
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 12Z...
* SHRA/TSRA THURSDAY MORNING AND WIND SHIFT ASSOCIATED WITH A COLD
FRONT PASSAGE.
* POTENTIAL FOR MVFR CIGS THURSDAY MORNING BEHIND COLD FRONT.
BMD
//DISCUSSION...UPDATED 12Z...
OVERALL EXPECT A FAIRLY QUIET DAY LOCALLY DOMINATED BY SOUTHWEST
WINDS AND VFR CONDITIONS. GUSTS INTO THE MID TO HIGH TEENS CAN BE
EXPECTED LATE THIS MORNING AND INTO THIS EVENING AHEAD OF AN
APPROACHING COLD FRONT. BY 18Z THIS AFTERNOON...EXPECT THE FRONT TO
STRETCH FROM ROUGHLY DLH SOUTHWEST TO FSD WITH MODERATE TO STRONG
INSTABILITY DEVELOPING AHEAD OF THE FRONT ACROSS PORTIONS OF
SOUTHERN MINNESOTA AND CENTRAL WISCONSIN...WHERE CONVECTIVE
INITIATION IS EXPECTED TO TAKE PLACE BY EARLY TO MID AFTERNOON. SOME
CONVECTIVE ALLOWING MODELS ARE SHOWING THUNDERSTORMS DEVELOPING
FARTHER SOUTHEAST...OVER NORTH CENTRAL ILLINOIS AND SOUTHERN
WISCONSIN...BUT EXPECT THIS AREA TO BE MOSTLY CAPPED WITH VERY
ISOLATED ACTIVITY IF ANY.
THE FRONT IS NOT EXPECTED TO PASS INTO ILLINOIS UNTIL AROUND 09Z
TONIGHT..AND INTO THE TERMINALS A COUPLE HOURS THEREAFTER. BY THIS
TIME...EXPECT THUNDERSTORMS PUSHING WELL AHEAD OF THE FRONT AND
INTENSITY TO BE ON A DECLINING TREND GIVEN THE UNFAVORABLE DIURNAL
TIMING AND THE LACK OF ANY SIGNIFICANT UPPER LEVEL SUPPORT. COVERAGE
SHOULD BECOME MORE WIDELY SCATTERED AS THE OVERNIGHT HOURS PROGRESS
LEADING TO UNCERTAINTY IN IMPACTS AT THE TERMINALS. IN FACT SOME
CAMS SUGGEST THAT ACTIVITY MAY DIMINISH COMPLETELY OVER NORTHERN
ILLINOIS...THEN REFORM SOUTH OF THE TERMINALS TOMORROW.
ONCE THE FRONT PASSES THROUGH...THERE MAY BE A BRIEF WINDOW IN THE
MORNING WHERE LOWER MFVR CIGS DEVELOP BEHIND THE FRONT AS THE COOLER
AIR PUSHES INTO THE UPPER 60 DEWPOINTS...BUT SHOULD BE ON THE ORDER
OF AN HOUR OR TWO BEFORE DRIER AIR STARTS TO TRICKLE SOUTH AND
DAYTIME MIXING COMMENCES. WINDS ARE EXPECTED TO BECOME NORTHEASTERLY
AS HIGH PRESSURE BUILDS ACROSS MINNESOTA AND WISCONSIN.
BMD
//ORD AND MDW CONFIDENCE...UPDATED 12Z...
* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH THE EARLY
OVERNIGHT HOURS.
* MEDIUM TO HIGH CONFIDENCE IN AT LEAST WIDELY SCATTERED TSRA
MOVING INTO THE AREA LATE TONIGHT/EARLY THURSDAY.
* MEDIUM CONFIDENCE IN TIMING FRONTAL WIND SHIFT EARLY THURSDAY.
* LOW CONFIDENCE IN MVFR CIGS BEHIND THE FRONT EARLY THURSDAY.
BMD
//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...
THURSDAY NIGHT THROUGH MONDAY...VFR.
TUESDAY...SLT CHC TSRA.
BMD
&&
.MARINE...
237 AM CDT
SOUTHWEST WINDS TO AROUND 25 KT WILL CONTINUE THROUGH THE DAY TODAY
ACROSS NORTHERN LAKE MICHIGAN AHEAD OF AN APPROACHING COLD FRONT
WHICH CURRENTLY STRETCHES FROM SOUTHERN MANITOBA INTO THE DAKOTAS.
WINDS WILL BE A LITTLE WEAKER ON THE SOUTH END OF THE LAKE WHERE THE
GRADIENT ISNT QUITE AS TIGHT. STABLE CONDITIONS ARE EXPECTED OVER
THE LAKE WHICH WILL HELP KEEP HIGHER END GUSTS IN CHECK...THOUGH
WOULDNT BE SURPRISED TO SEE SHIPS REPORT OCCASIONAL GUSTS TO 30
KTS. WINDS TURN NORTHERLY LATE TONIGHT AND EARLY THURSDAY...WITH
GUSTS AROUND 25 KT MAINTAINING ACROSS THE SOUTH HALF OF THE LAKE.
WINDS BEGIN TO TAPER THURSDAY EVENING AS HIGH PRESSURE BUILDS
ACROSS THE WESTERN LAKES REGION. WINDS WILL TURN SOUTHERLY AGAIN
SATURDAY AS ANOTHER LOW PRESSURE SYSTEM MOVES ACROSS THE CANADIAN
PRAIRIES...AND FRESHEN UP ESPECIALLY ON SUNDAY WHEN WE MAY ONCE
AGAIN BE LOOKING AT 20 TO 25 KT WINDS.
BMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
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FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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WWW.TWITTER.COM/NWSCHICAGO
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AREA FORECAST DISCUSSION...UPDATED
NWS CHICAGO/ROMEOVILLE IL
625 AM CDT WED AUG 21 2013
.DISCUSSION...
625 AM CDT
HAVE UPDATED THE FORECAST EARLY THIS MORNING TO ACCOUNT FOR MORE
MORNING AND EARLY AFTERNOON CLOUD COVER. WHAT IS LEFT OF A SHEARED
OUT SHORT WAVE ON WATER VAPOR CENTERED ACROSS WI IS HELPING TO
CAUSE ENOUGH ASCENT AND FOCUS FOR 5000-8000 FT CLOUDS ACROSS
NORTHERN IL AND WI. THE RAP 750-850MB CAPTURES THE RH DEPICTION
PRETTY WELL...AND THE SPC WRF COLUMN CONDENSATE DOES TOO ALTHOUGH
A BIT LATE WITH IT. BOTH SHOW INDICATIONS OF THE CLOUDS STICKING
AROUND INTO THIS AFTERNOON AND WITH THE SLOW MOVEMENT OF THE
SHEARED WAVE THAT SEEMS MORE PLAUSIBLE THAN EARLIER. SO HAVE
BUMPED UP SKY COVER QUITE A BIT AND EASED THE TEMPERATURE CLIMB
ALONG WITH BUMPING DOWN HIGHS 2-4 DEGREES IN THE NORTHERN HALF OF
THE AREA. ITS POSSIBLE MORE MAY NEED TO BE PEELED AWAY IF CLOUDS
ARE THICK ENOUGH. CONFIDENCE IS NOT THAT HIGH ON HOW THICK THE
CLOUDS WILL REMAIN AS RAP DIAGNOSTIC SOUNDINGS INDICATE THE RH TO
BE FAIRLY SHALLOW. EVEN IF SCATTERED AT TIMES THOUGH IT LIKELY
WILL SLOW THE TEMPERATURE JUMP...SO FELT ENOUGH CONFIDENCE TO
LOWER THEM SOME.
MTF
&&
.PREV DISCUSSION...
328 AM CDT
THE FORECAST FOCUS WAS FIRST ON THE CHANCES FOR STORMS TONIGHT AND
MAINLY EARLY THU...WHICH EVEN THOUGH THE COVERAGE IS NOT EXPECTED
TO BE PARTICULARLY HIGH THIS IS THE BEST CHANCE FOR RAIN IN OVER A
WEEK. THEN ATTENTION TURNED TO TEMPERATURES WITH LIKELY 90 TODAY
IN MANY COMMUNITIES...THEN A SHORT TERM COOL DOWN FOLLOWED BY AN
APPRECIABLE WARM UP INTO THE FINAL WEEK OF METEOROLOGICAL SUMMER
/ALREADY???/.
TODAY...WHAT HAS BEEN A STAGNANT BUT VERY PLEASANT PATTERN OVER
THE REGION IS BEGINNING TO SHOW SOME SHIFTING EARLY THIS
MORNING...WITH WATER VAPOR SHOWING A STRONG 110 KT+ JET ACROSS FAR
SOUTHERN CANADA BUCKLING SLIGHTLY INTO THE UPPER MIDWEST. MULTIPLE
SHORT WAVES ARE NOTED ACROSS THE NORTHERN ROCKIES AND UPPER
MIDWEST ON THE LEADING EDGE OF THE IMPINGING UPPER TROUGH. AREA
SOUNDINGS LAST EVENING AND VARIOUS SATELLITE CHANNELS CONTINUE TO
INDICATE A FAIRLY DRY MID LEVEL AIR MASS OVER OUR AREA WHICH WILL
TAKE TIME TO SATURATE...SO NOT EXPECTING BLOWOFF FROM ANY MORNING
CONVECTION TO THE NORTHWEST TO REALLY SPREAD OVER WITH ONLY SOME
CUMULUS THROUGH EARLY AFTERNOON. THE THERMAL RIDGE AT 850-925MB IN
ADVANCE OF THE TROUGH LEANS ESE TODAY OVER THE AREA AND THESE
VALUES DO SUPPORT 90 ABOUT A QUARTER OF THE TIME BASED ON LOCAL
CLIMATOLOGY. GIVEN LOCAL HIGHS YESTERDAY AT 87-88 IN MOST
PLACES...UPSTREAM HIGHS IN CENTRAL IA WERE AT 90...AND WITH OUR
DRYING GROUND OFFERING SENSIBLE HEAT TO BE A BIGGER
FACTOR...BELIEVE 88 TO 92 SHOULD PREVAIL ACROSS MUCH OF THE AREA.
DEW POINTS FAVORED IN THE MID TO UPPER 60S WILL ALLOW FOR HEAT
INDEX READINGS TO INCH INTO THE MID 90S IN A SOME COMMUNITIES.
TONIGHT INTO THU MORNING...AS PRIMARY HEIGHT FALLS DEVELOP EAST
ACROSS ONTARIO...THE DEVELOPING SURFACE LOW WILL TRACK EAST UP
THERE...WITH A WEAK SECONDARY LOW /1011MB OR SO/ FAVORED IN
GUIDANCE TO MOVE ALONG THE FRONT FROM IA TO CENTRAL LAKE MI
TONIGHT. THIS FEATURE ALONG WITH THE UPPER TO MID JET TURNING MORE
NORTHWEST GIVING THE FRONT A GOOD PUSH SOUTHWARD ACROSS THE AREA
ON THU. SOME GUIDANCE INDICATES CONVECTION INTO THE AREA THIS
EVE...BUT THAT JUST SEEMS TO QUICK GIVEN THE DRY RH AND LIMITED
MOISTURE TRANSPORT IN ADVANCE OF THE SYSTEM. THE FOCUS OF THE
BOUNDARY CONVERGENCE WILL BE IN WI LATE AFTERNOON AND EVE WITH
SCATTERED POSSIBLY STRONG CONVECTION EXPECTED THERE. GIVEN HIGH
INSTABILITY AND ASSOCIATED DCAPE VALUES UPSTREAM A FEW CLUSTERS
MAY MAKE QUICK PROGRESS SE BY MID TO LATE EVE INTO
OVERNIGHT...ESPECIALLY IF OVER THE LAKE. BUT AGAIN COVERAGE LOOKS
SCATTERED. THIS SYSTEM HAS THE MAKINGS OF A LATE SUMMER FRONT BY
OVERNIGHT WITH WEAKENING SURFACE PRESSURES ALONG IT IN THE WAKE OF
THE AFOREMENTIONED LOW...WEAKENING WARM AIR ADVECTION/DIFFERENTIAL
TEMPERATURE ADVECTION IN ADVANCE OF IT...AND AGAIN LIMITED
MOISTURE. THE DEEP LAYER SHEAR ALSO IS MARGINAL WITH VECTORS
ORIENTED POORLY FOR ANY MCS TYPE ORGANIZATION. OVERALL THE MODEL
SUITE SUPPORTS LIMITED AREAL COVERAGE OF QPF GREATER THAN 0.25 IN.
SO KEEP MAINLY CHANCE POPS EVERYWHERE TONIGHT WITH ONLY MINOR
TWEAKS TO WHAT WAS IN THERE...AND MAINTAIN THE HIGHEST OVERNIGHT.
REST OF THU AND FRI....DRY AIR AND SUPPRESSION MOVE QUICKLY
SOUTHWARD BEHIND THE SURFACE COOL FRONT...WHICH LOOKS TO MOVE
DOWN THE LAKE AND THROUGH CHICAGO SOMETIME IN THE MID-MORNING.
THIS MAY CONTINUE TO SUPPORT SCATTERED SHOWERS AND SOME STORMS
ALONG IT...SO MAINTAIN POPS ESPECIALLY FOR THE SOUTHERN CWA
THROUGH THE DAY. THE PATTERN SUPPORTS TEMPS LIKELY FALLING ALONG
THE LAKE SHORE BY LATE MORNING INTO EARLY AFTERNOON AND REACHING
THEIR PEAK IN OUTLYING AREAS EARLY IN THE AFTERNOON AND THEN
HOLDING STEADY. DRIER AIR REALLY WORKS ITS WAY IN WITHIN THE LOW-
LEVELS THU NIGHT. WITH MOSTLY SUNNY CONDITIONS FRI THIS SHOULD
SUPPORT GOOD MIXING OUT WITH RELATIVE HUMIDITY EXPECTED TO DROP TO
AROUND 30 PERCENT FRI AFTERNOON...AN EARLY SIGN THAT THE NEXT
SEASON IS INDEED NOT FAR AWAY. WITH 850MB TEMPERATURES IN THE MID
TEENS...TEMPS ON FRI LOOK TO BE IN THE MID 70S TO LOWER 80S. FRI
NIGHT SHOULD BE THE COOLEST WITH HIGH PRESSURE STILL PRIMARILY
INFLUENCING THE AREA AND LITTLE CIRRUS EXPECTED. WHILE DEW POINTS
IN THE 40S ARE LIKELY DURING FRI AFTERNOON...THESE SHOULD COME
BACK INTO THE EVE AND LOWS RIGHT NOW LOOK TO BOTTOM OUT IN THE
LOWER TO MID 50S IN MOST OUTLYING LOCATIONS.
BEYOND...THE UPPER RIDGE LOOKS TO BUILD BACK NORTHEAST AS THE
WEEKEND PROGRESSES AND INTO NEXT WEEK...SUPPORTING WARMING
TEMPS AS WELL AS LIKELY PRECIP-FREE CONDITIONS WITH THE FOCUS OF
SYSTEMS AGAIN SHIFTING NORTHWARD. WHILE 90 DEGREES OR WARMER LOOKS
POSSIBLE ON MULTIPLE DAYS WITH MID TO UPPER 60S DEW POINTS...THE
SIGNAL IS STRONGEST ON MON AND TUE WITH THEN SOME BUCKLING DUE TO
POSSIBLE SHORT WAVES/UPSTREAM STORMS. HAVE BLENDED BIAS-
CORRECTED DATA FROM MODELS INTO THE GOING FORECAST WHICH SUPPORTS
WARMER TEMPS THAN A STRAIGHT MODEL BLEND.
MTF
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* SHRA/TSRA THURSDAY MORNING ASSOCIATED WITH A COLD FRONT.
BMD
//DISCUSSION...UPDATED 06Z...
A COLD FRONT STRETCHES FROM SOUTHERN MANITOBA SOUTHWEST ACROSS THE
DAKOTAS LATE THIS EVENING...WHILE A BROAD AREA OF HIGH PRESSURE
SPANS THE EASTERN CONUS. IN BETWEEN THESE SYSTEMS...CONTINUE TO
EXPECT SOUTHWEST FLOW THROUGH THE PERIOD. PATCHY SHALLOW FOG HAS
DEVELOPED THE PAST FEW MORNINGS AND MAY ONCE AGAIN WEDNESDAY MORNING
AT DPA/RFD AND POSSIBLY GYY. BRIEF MVFR CONDITIONS MAY DEVELOP IN
THE SHALLOW GROUND FOG FOR AN HOUR OR TWO AT THESE SITES. WINDS
SHOULD BEGIN TO PICK AFTER SUNRISE WITH GUSTS INTO THE HIGH TEENS BY
LATE MORNING AND THROUGH THE AFTERNOON.
THE COLD FRONT IS EXPECTED TO MOVE INTO THE AREA THURSDAY MORNING.
BEST GUESS NOW IS APPROX 12-14Z TIMING FOR A WINDSHIFT ACROSS THE
NORTHERN ILLINOIS TERMINALS. MODELS DEVELOP SHOWERS AND
THUNDERSTORMS ALONG AND AHEAD OF THE FRONT...BUT THERE ARE A LOT OF
INDICATIONS THAT GUIDANCE MAY BE OVERDOING QPF. THE BEST UPPER LEVEL
SUPPORT DEVELOPS WELL NORTH OF THE AREA AND WE LIE UNDER A PRETTY
WEAK FLOW ENVIRONMENT ALOFT...WITH ONLY ABOUT 25KT WINDS AT 500 MB.
MODELS ALSO INDICATE FAIRLY DRY AIR IN THE LOW AND MID LEVELS. THERE
IS LITTLE SIGNAL FOR ROBUST CONVECTION TO CONTINUE WELL INTO THE
OVERNIGHT HOURS. WHILE THERE WILL PROBABLY BE SOME CONVECTION
FOCUSED NEAR AND JUST AHEAD OF THE FRONT WHERE MODERATE ELEVATED
INSTABILITY IS EXPECTED...COVERAGE MAY BE LOW LENDING TO LOWER
CONFIDENCE IN IMPACTS AT THE TERMINALS. WILL INCLUDE A PROB30
MENTION FOR NOW.
BMD
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* LOW CONFIDENCE IN IMPACTS AT THE TERMINALS FROM SHRA/TSRA IN THE
CURRENT TAF PERIOD.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH WEDNESDAY NIGHT.
BMD
//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...
THURSDAY...CHC TSRA.
FRIDAY THROUGH MONDAY...VFR.
JEE
&&
.MARINE...
237 AM CDT
SOUTHWEST WINDS TO AROUND 25 KT WILL CONTINUE THROUGH THE DAY TODAY
ACROSS NORTHERN LAKE MICHIGAN AHEAD OF AN APPROACHING COLD FRONT
WHICH CURRENTLY STRETCHES FROM SOUTHERN MANITOBA INTO THE DAKOTAS.
WINDS WILL BE A LITTLE WEAKER ON THE SOUTH END OF THE LAKE WHERE THE
GRADIENT ISNT QUITE AS TIGHT. STABLE CONDITIONS ARE EXPECTED OVER
THE LAKE WHICH WILL HELP KEEP HIGHER END GUSTS IN CHECK...THOUGH
WOULDNT BE SURPRISED TO SEE SHIPS REPORT OCCASIONAL GUSTS TO 30
KTS. WINDS TURN NORTHERLY LATE TONIGHT AND EARLY THURSDAY...WITH
GUSTS AROUND 25 KT MAINTAINING ACROSS THE SOUTH HALF OF THE LAKE.
WINDS BEGIN TO TAPER THURSDAY EVENING AS HIGH PRESSURE BUILDS
ACROSS THE WESTERN LAKES REGION. WINDS WILL TURN SOUTHERLY AGAIN
SATURDAY AS ANOTHER LOW PRESSURE SYSTEM MOVES ACROSS THE CANADIAN
PRAIRIES...AND FRESHEN UP ESPECIALLY ON SUNDAY WHEN WE MAY ONCE
AGAIN BE LOOKING AT 20 TO 25 KT WINDS.
BMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)
FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
957 AM CDT WED AUG 21 2013
.UPDATE...
ISSUED AT 947 AM CDT WED AUG 21 2013
WEAK ISOLATED SHOWERS CONTINUE TO PERSIST AT MID MORNING. THE
SHOWERS BETWEEN KCID AND KDBQ ARE RAPIDLY DISSIPATING WITH NEW
ISOLATED SHOWERS BETWEEN KMLI AND KOTM.
THE RAP MODEL HAS A SUBTLE VORT MAX MOVING THROUGH EASTERN IOWA
WHICH APPEARS TO BE RESPONSIBLE FOR THE ISOLATED SHOWERS. IF THE
RAP TRENDS ARE CORRECT...THESE NEW SHOWERS WILL DISSIPATE WITHIN
THE NEXT SEVERAL HOURS AS THE VORT MAX EXITS THE CWFA AND DOWNWARD
MOTION TAKES OVER.
THE QUESTION THEN BECOMES WHEN WILL NEW CONVECTION DEVELOP. THE
MCS AND LIFT TOOLS SUGGEST NORTH OF THE CWFA BY LATE AFTERNOON
ALONG THE FRONT. THERE ARE DIFFERENCES BETWEEN THE VARIOUS MODEL
SOLUTIONS AS TO WHEN PRECIPITATION WILL ARRIVE IN THE CWFA. THE
OVERALL FORCING REMAINS WEAK AND FCST SOUNDINGS SUGGEST A CAP
REMAINING IN PLACE THROUGH THE DAY. PRECIPITATION MAY HOLD OFF
UNTIL AFTER SUNSET.
WHAT LLJ IS PRESENT IS EXTREMELY WEAK AND GENERALLY WELL WEST OF
THE CWFA. THE CHANCES FOR PRECIPITATION ARE NOT OVERLY GOOD BUT
WILL MAINTAIN THE CURRENT POPS FOR TONIGHT. ..08..
&&
.SYNOPSIS...
ISSUED AT 331 AM CDT WED AUG 21 2013
WARM AIR IS FINALLY IN TOTAL CONTROL OVER THE ENTIRE CWA EARLY
TODAY...WITH TEMPERATURES HOVERING AROUND 70...WITH DEW POINTS IN THE
MID 60S. A COLD FRONT IS MOVING SLOWLY SOUTHEAST THROUGH THE
DAKOTA...SPARKING A FEW AREAS OF SHOWERS AND THUNDERSTORMS. THE AREA
LOCATED IN SOUTH DAKOTA IS ASSOCIATED WITH A WEAK SHORT WAVE THAT
SHOULD INITIATE STORMS CLOSE TO OUR CWA THIS EVENING.
&&
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 331 AM CDT WED AUG 21 2013
FOR THE FIRST TIME IN WEEKS...THERE IS A REASONABLE CHANCE FOR RAIN
TONIGHT. HOWEVER...WITH WEAK DYNAMICS...AND LESS THAN OPTIMAL
FRONTAL TIMING...THERE REMAINS LOW CONFIDENCE ON A
MATURE...BENEFICIAL RAIN PRODUCING MCS. WHILE THIS IS
POSSIBLE...ESPECIALLY IN THE NORTH 1/2...SIGNALS INDICATING A MATURE
MCS ARE JUST NOT COMING TOGETHER IN A CONFIDENT PICTURE. INFLOW AT
850MB TONIGHT APPEARS WEAK..AND LACKING FOCUSED CONVERGENCE. WHILE
MUCAPE VALUES WILL SUPPORT THUNDER...WE WILL LIKELY NEED A
CONVECTIVE OUTFLOW FROM THE NORTH TO RESULT IN WIDESPREAD
CONVECTION. THIS IS TOO MANY IFS TO RESULT IN A LIKELY COVERAGE
FORECAST ISSUANCE...AND I AM LEFT WITH A RANGE OF CHANCE POPS FROM
20 SOUTH TO 50 NORTH TO BEST DESCRIBE THE EVENT POTENTIAL OVERNIGHT.
RAINFALL WHERE IT OCCURS...COULD BE 0.2 TO 0.5...BUT WIDESPREAD
TOTALS MAY NOT EXCEED 0.1 SHOULD MESOSCALE PROCESSES NOT COME
TOGETHER.
TEMPERATURES AND HUMIDITY WILL BOTH BE QUITE HIGH TODAY...WITH
UPSTREAM TRAJECTORIES AND MIX DOWN IN MODELS SUGGESTING UPPER 80S TO
VERY LOW 90S SHOULD BE WIDESPREAD FOR HIGHS TODAY. TONIGHT...UPPER
60S NORTH TO AROUND 70 SOUTH APPEARS MOST LIKELY FOR LOWS...UNLESS
AN ORGANIZED COLD POOL CAN PUSH RAIN COOLED TEMPERATURES TO THE MID
60S.
ERVIN
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 331 AM CDT WED AUG 21 2013
FOCUS IN THE LONG TERM IS WITH WALKING OUT PCPN CHANCES THU/THU
NIGHT AS FRONT CONTINUES TO MOVE SOUTHWARD THROUGH THE AREA AND
DRIER AIR INTRUDES FROM THE NORTH. LOW CHANCE POPS /26-30/
ARE EXPECTED AS THE FRONT SAGS SOUTHWARD INTO MO AND CENTRAL IL
DURING THE DAY THU. LINGERING SLIGHT CHANCES ARE IN THE SOUTH FOR
THU NIGHT. SURFACE HIGH PRESSURE WILL NUDGE INTO THE AREA FRIDAY
BEFORE QUICKLY MOVING OFF TO THE NE. THEN AN UPPER LEVEL RIDGE OF
HIGH PRESSURE IS EXPECTED TO BUILD INTO THE MID MS RIVER VALLEY
REGION ON ITS HEELS. FRIDAY AND BEYOND...DRY CONDITIONS ARE
ANTICIPATED WITH A WARMING TREND...AS A HEAT WAVE COMMENCES SUN...
LASTING THROUGH TUE. HIGHS THU-SAT WILL BE IN THE 80S /POSSIBLY SOME
UPPER 70S NORTH FRI/...WHILE HIGHS SUN-TUE RISE INTO THE UPPER 80S
AND LOWER 90S...WITH HEAT INDICES IN THE 90S.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 606 AM CDT WED AUG 21 2013
A COLD FRONT WILL SLOWLY MOVE TOWARD EASTERN IOWA LATE THIS
EVENING...TRIGGERING A SCATTERED TO BROKEN LINE OF SHOWERS AND
THUNDERSTORMS. THIS LINE MAY BE WIDESPREAD OR SCATTERED...AND THIS
IS NOT YET CLEAR DUE TO THE TIMING OF THE FRONT. IN ANY
CASE...TODAY WILL BE VFR...WITH SOUTH TO SOUTHWEST WINDS AT 10 TO
20 KTS...BECOMING LIGHT SOUTH THIS EVENING...AND AT DBQ AND
CID...AS THE FRONT APPROACHES...THE WINDS WILL SWITCH TO WEST OR
NORTHWEST AFTER 06Z/22. THE FRONT WILL BE SLOW TO MOVE OUT OF THE
AREA...AND A VICINITY SHOWER THREAT CONTINUES THROUGH 12Z/22. AS
DETAILS BECOME MORE CONFIDENT ON FRONTAL TIMING AND CONVECTIVE
TRENDS...WE WILL LIKELY ADD THUNDERSTORMS TO THE MLI AND BRL
TAFS...BUT FOR NOW...A SHOWER CHANCE IS ALL THAT IS INCLUDED DUE
TO POOR CONFIDENCE ON TIMING AND COVERAGE OF STORMS.
ERVIN
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
UPDATE...08
SYNOPSIS...ERVIN
SHORT TERM...ERVIN
LONG TERM...14
AVIATION...ERVIN
AREA FORECAST DISCUSSION...CORRECTED
NWS MARQUETTE MI
1036 AM EDT WED AUG 21 2013
.UPDATE...
ISSUED AT 1029 AM EDT WED AUG 21 2013
JUST A QUICK UPDATE FOR THE EXPECTATIONS FOR THIS AFTERNOON AND
EARLY EVENING BASED OFF LATEST HIGHER RESOLUTION MODEL RUNS AND
NEWLY ARRIVING 12Z RUNS. OVERALL...FEEL THAT THE EXPECTATIONS OVER
THE LAST COUPLE OF DAYS STILL SEEM VALID. AT THE PRESENT
TIME...COLD FRONT IS STRETCHING SOUTHWEST FROM JUST NORTH OF LAKE
SUPERIOR THROUGH THE MN ARROWHEAD AND INTO WEST CENTRAL MN.
ISOLATED SHOWERS AND THUNDERSTORMS CONTINUE TO DEVELOP ALONG THE
FRONT BUT THEN DECAY AS THEY SLIDE AHEAD OF IT. VERY SHARP CONTRAST
IN DEWPOINTS AHEAD (UPPER 60S AND LOWER 70S) OF THE FRONT AND MID
50S BEHIND. THIS FRONT WILL BE THE FOCUS FOR CONVECTION EARLY-MID
AFTERNOON (18-20Z) AS IT MOVES INTO THE WESTERN U.P. AND THEN STORM
MOTIONS AND FRONT MOVING THE THUNDERSTORMS EAST-SOUTHEAST. SEVERE
WEATHER PARAMETERS LOOK TO BE SIMILAR AS MENTIONED IN THE SHORT TERM
DISCUSSION. AM FAIRLY CONFIDENT ON THUNDERSTORM OCCURRENCE...BUT
SEVERE THREAT IS A LITTLE UNCERTAIN...LARGELY DUE TO THE LIMITED
EFFECTIVE AND 0-6KM BULK SHEAR OF 25-30KT. THIS MAY LIMIT SOME OF THE
TILTING/ORGANIZATION OF THE THUNDERSTORMS. LATEST RAP RUN HAS PUSHED
VALUES UP A LITTLE MORE (TOWARDS 35KTS)...ALONG WITH 09Z SREF
PROBABILITIES...WHICH WITH THE PUSH/FORCING OF THE COLD FRONT LEADS
TO A LITTLE HIGHER CONFIDENCE OF SOME ORGANIZATION AND SEVERE THREAT.
WITH THE SLIGHT INCREASE IN SHEAR...OPTED TO ADD DAMAGING WINDS TO
THE WEATHER GRIDS ALONG WITH SMALL HAIL. &&
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 250 AM EDT WED AUG 21 2013
CURRENTLY /MIDNIGHT EARLY WED/...THE CWA IS BETWEEN A SFC HIGH OVER
THE ERN SEABOARD AND A SFC TROUGH/COLD FRONT FROM HUDSON BAY TO NW
MN TO SD AND CO. ALOFT...THE CWA IS UNDER THE INFLUENCE OF ZONAL
FLOW OVER CANADA AND THE NRN CONUS...WITH AN UPPER TROUGH NW OF THE
SFC TROUGH.
THE SFC TROUGH/COLD FRONT WILL MOVE ACROSS THE CWA TODAY INTO EARLY
TONIGHT...AND MODELS ARE IN PRETTY GOOD AGREEMENT ON THE TIMING OF
THE FRONT SO TIMING OF POPS WILL BE PRETTY EASY. THE SW/NE ORIENTED
FRONT WILL MOVE TO WRN UPPER MI AROUND 18Z WED...THEN TO ERN LAKE
SUPERIOR AND CENTRAL UPPER MI BY 00Z THU...THEN JUST E OF THE CWA BY
06Z THU. WITH 850MB TEMPS AROUND 20C ALONG AND AHEAD OF THE
FRONT...THOSE AREAS THAT DO NOT EXPERIENCE MUCH CLOUD COVER AND
PRECIP BY PEAK HEATING /MAINLY CENTRAL AND ERN UPPER MI/ WILL SEE
HIGH TEMPS AROUND 90F WED...WITH THE EXCEPTION BEING LOCATIONS N/NE
OF LAKE SUPERIOR DUE TO SW WINDS. OTHERWISE...EXPECT HIGHS IN THE
80S OVER WRN UPPER MI WHERE CLOUDS/PRECIP WILL MOVE IN EARLIER IN
THE DAY WITH THE FRONT. SBCAPES OF 2000-3500 J/KG SHOULD RESULT IN
THE WARM SECTOR...BUT 0-6KM WIND SHEAR IS ONLY 20-30KTS AND ALMOST
COMPLETELY UNIDIRECTIONAL. DCAPE VALUES AROUND 1000 J/KG ARE
POSSIBLE...HIGHEST OVER SCENTRAL UPPER MI. WITH ALL THIS IN
MIND...WIND SHEAR LOOKS TO BE THE LIMITING FACTOR FOR SEVERE
STORMS...BUT WITH THE CAPE AND DCAPE SO HIGH...EXPECT ISOLATED TO
SCATTERED SEVERE STORMS IN PRIMARILY MULTICELL STORM CLUSTER/S WITH
A LIMITED POSSIBILITY OF SUPERCELL THUNDERSTORMS /ESPECIALLY ALONG
LAKE BREEZE BOUNDARIES/. GREATEST THREAT STILL LOOKS LIKE DAMAGING
WINDS...WITH ONLY AN ISOLATED SEVERE HAIL THREAT DUE TO THE FREEZING
LEVEL BEING AROUND 12KFT.
CONVECTION SHOULD EXIT E/SE BY AROUND 06Z-09Z THU...WITH SFC HIGH
PRESSURE QUICKLY FILLING IN BEHIND THE TROUGH. THIS WILL RESULT IN
SOME LOCATIONS OVER WRN UPPER MI BEING ABLE TO FALL TO AROUND 50F
FOR LOWS LATE WED NIGHT.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 250 AM EDT WED AUG 21 2013
MAIN FCST CONCERNS IN THE LONGER TERM ARE TEMPS ON THU/FRI WITH DRY
HI PRES DOMINATING. FOCUS FOR THE WEEKEND INTO EARLY NEXT WEEK ALSO
INCLUDES SHRA/TS CHCS AS A MORE ACTIVE SUMMER-LIKE PATTERN EVOLVES
OVER THE UPR LKS ON THE SRN EDGE OF ZONAL FLOW IN SRN CANADA AND N
OF STRONG RDG IN THE CONUS.
THU...ARRIVAL OF VIGOROUS DNVA/DEEP LYR QVECTOR DVGC UNDER CONFLUENT
UPR FLOW/MUCH DRIER AIR WITH PWAT FCST ARND 0.5 INCH /OR 50 PCT OF
NORMAL/ IN THE WAKE OF SHRTWV PASSAGE EARLY IN THE DAY WL BRING
MOSUNNY WX TO THE CWA ON THU. THE DAY WL ALSO BE MUCH COOLER DESPITE
BRIGHT SUNSHINE WITH H85 TEMPS PROGGED TO BE WITHIN A DEGREE OR 2 OF
10C.
THU NGT...ALTHOUGH SOME OF THE MODELS SHOW ANOTHER SHRTWV DROPPING
SEWD THRU THE GRT LKS IN THE NW FLOW ALF...THIS DISTURBANCE WL HAVE
LTL IMPACT DUE TO THE DRYNESS OF THE AIRMASS AND LARGER SCALE ACYC
FLOW ASSOCIATED WITH SFC HI CENTERED OVER THE AREA. THERE COULD BE
SOME PATCHY CLDS OVER MANLY THE NE HALF OF THE CWA CLOSER TO THE
TRACK OF THIS FEATURE...BUT OVERALL LGT WINDS/PWAT STILL 0.50-0.75
INCH WL ALLOW FOR A HEALTHY DIURNAL TEMP FALL WELL INTO THE 40S AT
THE COOLER INTERIOR LOCATIONS.
FRI...AS THE UPR RDG AXIS SHIFTS E INTO THE WRN GRT LKS AND DEEP LYR
QVECTOR DVGC/DRY AIR DOMINATE...EXPECT MOSUNNY SKIES. THE DAY SHOULD
ALSO TURN A BIT WARMER WITH LARGE SCALE SUBSIDENCE/RETURN SLY FLOW
ON THE WRN FLANK OF SFC HI PRES SHIFTING OVER LOWER MI LIFTING H85
TEMPS UP NEAR 15C OVER THE W BY 00Z SAT. LK BREEZES THAT DVLP NEAR
LK MI AND LK SUP E OF THE KEWEENAW UNDER THE WEAKER PRES GRADIENT
CLOSER TO THE DEPARTING SFC HI PRES WL ALLOW FOR SOME COOLING NEAR
THE LK SHORES IN THOSE AREAS.
FRI NGT...STRENGTHENING SSW WIND ON THE WRN FLANK OF SLOWLY
DEPARTING SFC HI PRES WL LIMIT NOCTURNAL COOLING...ESPECIALLY NEAR
LK SUP OVER THE W HALF WHERE THE STRONGER S WIND UNDER SHARPEST PRES
GRADIENT WL DOWNSLOPE AND SOME HI CLDS SPILLING OVER THE SLOWLY
APRCHG UPR RDG AXIS WL ARRIVE THRU THE NGT. EXPECT THE COOLEST
OVERNGT LO TEMPS ACROSS THE INTERIOR CENTRAL AND E.
THIS WEEKEND...UPR RDG IN THE PLAINS IS PROGGED TO BUILD INTO THE
UPR LKS IN WAD PATTERN/SSW FLOW BTWN HI PRES DRIFTING INTO THE MID
ATLANTIC STATES AND LOWER PRES IN CENTRAL CANADA. A NUMBER OF THE
EXTENDED MODELS SHOW H85 TEMPS NEARING 20C AND PWAT REACHING 1.50 TO
1.75 INCHES BY SUN...SO THE WX WL TURN WARMER AND MORE HUMID.
WHETHER SHRTWVS RIDING THRU THE ZONAL FLOW ON THE TOP OF THIS UPR
RDG WL INTERACT WITH THE INCRSGLY UNSTABLE AIRMASS AND GENERATE
SHRA/TS IS A SGNFT FCST CONCERN. SUSPECT THE BEST SHOT AT SHRA/TS WL
BE SAT NGT/SUN FOLLOWING DEPARTURE OF DRY AIRMASS AND OVER THE NRN
TIER CLOSER TO THE SHRTWVS TRACKING THRU ONTARIO AND LOWER HGTS.
EXTENDED...THE CWA IS FCST TO REMAIN NEAR THE SRN FLANK OF ZONAL
FLOW OVER SRN CANADA AND ON TOP OF UPR RDG DOMINATING THE CONUS.
THIS SUMMER-LIKE PATTERN WITH RECENT ECMWF/GFS RUNS SHOWING H85
TEMPS NEAR 20C IN VCNTY OF A STNRY FNT IS ONE THAT FAVORS EPISODES
OF SHRA WITH HEAVY RA/PERHAPS SVR TSRA ACCOMPANYING THE PASSAGE OF
SHRTWVS THRU THE UPR LKS/ONTARIO NEAR EDGE OF CAPPING INVRN
ASSOCIATED WITH THE STRONG RDG TO THE S. SPECIFYING THE DAY-TO-DAY
DETAILS IN THIS PATTERN IS IMPOSSIBLE ATTM...SO WL STICK TO THE
CONSENSUS FCST. THE CURRENT CPC DAY 3-7 OUTLOOK DOES INDICATE A
THREAT OF HEAVY RA FOR UPR MI OVER THE WEEKEND AND INTO EARLY NEXT
WEEK. TEMPS WL BE ABV NORMAL.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 731 AM EDT WED AUG 21 2013
EXPECT VFR CONDITIONS AT ALL 3 TAF SITES DESPITE THE CHANCE FOR
SHRA/TSRA THIS AFTERNOON/EVENING WITH THE PASSAGE OF A COLD FRONT.
EXPECT TSRA/SHRA EARLY THIS AFTERNOON AT KIWD AND KCMX WITH A BETTER
CHANCE LATE THIS AFTERNOON/EARLY EVENING AT KSAW WITH THE FRONTAL
PASSAGE.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 250 AM EDT WED AUG 21 2013
OVERALL...EXPECT STRONGEST WINDS /TO AROUND 20KTS/ OVER THE NEXT FEW
DAYS TO BE EARLY THIS MORNING INTO TODAY AS THE PRESSURE GRADIENT
TIGHTENS UP AHEAD OF A COLD FRONT THAT WILL MOVE THROUGH LATE THIS
MORNING INTO THIS EVENING...BUT HIGH OVERWATER STABILITY WITH INFLUX
OF A VERY WARM AIRMASS WILL LIMIT THE INCREASE OF WIND SPEED NEAR
THE COOLER LAKE SURFACE. THE ARRIVAL OF MORE HUMID AIR MAY RESULT IN
SOME FOG FORMATION OVER THE COOLER LAKE WATERS...BUT RESTRICTED THE
FOG FORECAST TO AREAS WHERE SOME SHOWERS OR THUNDERSTORMS ARE
EXPECTED. ANY FOG WILL DISSIPATE THIS AFTERNOON AND EVENING
FOLLOWING A COLD FRONTAL PASSAGE AND THE ARRIVAL OF DRIER AIR.
ANOTHER PERIOD OF STRONGER WINDS /FROM THE SW/ MAY OCCUR ON
SATURDAY NIGHT INTO SUNDAY AS LAKE SUPERIOR SITS BETWEEN A HIGH
PRESSURE SYSTEM TO THE SE AND A TROUGH OF LOW PRESSURE TO THE NW...
BUT HIGH OVERWATER STABILITY WILL REMAIN A LIMITING FACTOR ON HOW
STRONG THE NEAR SURFACE WINDS WILL BECOME.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
UPDATE...SRF
SHORT TERM...TITUS
LONG TERM...KC
AVIATION...TITUS
MARINE...TITUS
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1030 AM EDT WED AUG 21 2013
.UPDATE...
ISSUED AT 1029 AM EDT WED AUG 21 2013
JUST A QUICK UPDATE FOR THE EXPECTATIONS FOR THIS AFTERNOON AND
EARLY EVENING BASED OFF LATEST HIGHER RESOLUTION MODEL RUNS AND
NEWLY ARRIVING 12Z RUNS. OVERALL...FEEL THAT THE EXPECTATIONS OVER
THE LAST COUPLE OF DAYS STILL SEEM VALID. AT THE PRESENT
TIME...COLD FRONT IS STRETCHING SOUTHWEST FROM JUST NORTH OF LAKE
SUPERIOR THROUGH THE MN ARROWHEAD AND INTO WEST CENTRAL MN.
ISOLATED SHOWERS AND THUNDERSTORMS CONTINUE TO DEVELOP ALONG THE
FRONT BUT THEN DECAY AS THEY SLIDE AHEAD OF IT. VERY SHARP CONTRAST
IN DEWPOINTS AHEAD (UPPER 60S AND LOWER 70S) OF THE FRONT AND MID
50S BEHIND. THIS FRONT WILL BE THE FOCUS FOR CONVECTION EARLY-MID
AFTERNOON (18-20Z) AS IT MOVES INTO THE WESTERN U.P. AND THEN STORM
MOTIONS AND FRONT MOVING THE THUNDERSTORMS EAST-SOUTHEAST. SEVERE
WEATHER PARAMETERS LOOK TO BE SIMILAR AS MENTIONED IN THE SHORT TERM
DISCUSSION. AM FAIRLY CONFIDENT ON THUNDERSTORM OCCURRENCE...BUT
SEVERE THREAT IS A LITTLE UNCERTAIN...LARGELY DUE TO THE LIMITED
EFFECT AND 0-6KM BULK SHEAR OF 25-30KT. THIS MAY LIMIT SOME OF THE
TILTING/ORGANIZATION OF THE THUNDERSTORMS. LATEST RAP RUN HAS PUSHED
VALUES UP A LITTLE MORE (TOWARDS 35KTS)...ALONG WITH 09Z SREF
PROBABILITIES...WHICH WITH THE PUSH/FORCING OF THE COLD FRONT LEADS
TO A LITTLE HIGHER CONFIDENCE OF SOME ORGANIZATION AND SEVERE THREAT.
WITH THE SLIGHT INCREASE IN SHEAR...OPTED TO ADD DAMAGING WINDS TO
THE WEATHER GRIDS ALONG WITH SMALL HAIL. &&
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 250 AM EDT WED AUG 21 2013
CURRENTLY /MIDNIGHT EARLY WED/...THE CWA IS BETWEEN A SFC HIGH OVER
THE ERN SEABOARD AND A SFC TROUGH/COLD FRONT FROM HUDSON BAY TO NW
MN TO SD AND CO. ALOFT...THE CWA IS UNDER THE INFLUENCE OF ZONAL
FLOW OVER CANADA AND THE NRN CONUS...WITH AN UPPER TROUGH NW OF THE
SFC TROUGH.
THE SFC TROUGH/COLD FRONT WILL MOVE ACROSS THE CWA TODAY INTO EARLY
TONIGHT...AND MODELS ARE IN PRETTY GOOD AGREEMENT ON THE TIMING OF
THE FRONT SO TIMING OF POPS WILL BE PRETTY EASY. THE SW/NE ORIENTED
FRONT WILL MOVE TO WRN UPPER MI AROUND 18Z WED...THEN TO ERN LAKE
SUPERIOR AND CENTRAL UPPER MI BY 00Z THU...THEN JUST E OF THE CWA BY
06Z THU. WITH 850MB TEMPS AROUND 20C ALONG AND AHEAD OF THE
FRONT...THOSE AREAS THAT DO NOT EXPERIENCE MUCH CLOUD COVER AND
PRECIP BY PEAK HEATING /MAINLY CENTRAL AND ERN UPPER MI/ WILL SEE
HIGH TEMPS AROUND 90F WED...WITH THE EXCEPTION BEING LOCATIONS N/NE
OF LAKE SUPERIOR DUE TO SW WINDS. OTHERWISE...EXPECT HIGHS IN THE
80S OVER WRN UPPER MI WHERE CLOUDS/PRECIP WILL MOVE IN EARLIER IN
THE DAY WITH THE FRONT. SBCAPES OF 2000-3500 J/KG SHOULD RESULT IN
THE WARM SECTOR...BUT 0-6KM WIND SHEAR IS ONLY 20-30KTS AND ALMOST
COMPLETELY UNIDIRECTIONAL. DCAPE VALUES AROUND 1000 J/KG ARE
POSSIBLE...HIGHEST OVER SCENTRAL UPPER MI. WITH ALL THIS IN
MIND...WIND SHEAR LOOKS TO BE THE LIMITING FACTOR FOR SEVERE
STORMS...BUT WITH THE CAPE AND DCAPE SO HIGH...EXPECT ISOLATED TO
SCATTERED SEVERE STORMS IN PRIMARILY MULTICELL STORM CLUSTER/S WITH
A LIMITED POSSIBILITY OF SUPERCELL THUNDERSTORMS /ESPECIALLY ALONG
LAKE BREEZE BOUNDARIES/. GREATEST THREAT STILL LOOKS LIKE DAMAGING
WINDS...WITH ONLY AN ISOLATED SEVERE HAIL THREAT DUE TO THE FREEZING
LEVEL BEING AROUND 12KFT.
CONVECTION SHOULD EXIT E/SE BY AROUND 06Z-09Z THU...WITH SFC HIGH
PRESSURE QUICKLY FILLING IN BEHIND THE TROUGH. THIS WILL RESULT IN
SOME LOCATIONS OVER WRN UPPER MI BEING ABLE TO FALL TO AROUND 50F
FOR LOWS LATE WED NIGHT.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 250 AM EDT WED AUG 21 2013
MAIN FCST CONCERNS IN THE LONGER TERM ARE TEMPS ON THU/FRI WITH DRY
HI PRES DOMINATING. FOCUS FOR THE WEEKEND INTO EARLY NEXT WEEK ALSO
INCLUDES SHRA/TS CHCS AS A MORE ACTIVE SUMMER-LIKE PATTERN EVOLVES
OVER THE UPR LKS ON THE SRN EDGE OF ZONAL FLOW IN SRN CANADA AND N
OF STRONG RDG IN THE CONUS.
THU...ARRIVAL OF VIGOROUS DNVA/DEEP LYR QVECTOR DVGC UNDER CONFLUENT
UPR FLOW/MUCH DRIER AIR WITH PWAT FCST ARND 0.5 INCH /OR 50 PCT OF
NORMAL/ IN THE WAKE OF SHRTWV PASSAGE EARLY IN THE DAY WL BRING
MOSUNNY WX TO THE CWA ON THU. THE DAY WL ALSO BE MUCH COOLER DESPITE
BRIGHT SUNSHINE WITH H85 TEMPS PROGGED TO BE WITHIN A DEGREE OR 2 OF
10C.
THU NGT...ALTHOUGH SOME OF THE MODELS SHOW ANOTHER SHRTWV DROPPING
SEWD THRU THE GRT LKS IN THE NW FLOW ALF...THIS DISTURBANCE WL HAVE
LTL IMPACT DUE TO THE DRYNESS OF THE AIRMASS AND LARGER SCALE ACYC
FLOW ASSOCIATED WITH SFC HI CENTERED OVER THE AREA. THERE COULD BE
SOME PATCHY CLDS OVER MANLY THE NE HALF OF THE CWA CLOSER TO THE
TRACK OF THIS FEATURE...BUT OVERALL LGT WINDS/PWAT STILL 0.50-0.75
INCH WL ALLOW FOR A HEALTHY DIURNAL TEMP FALL WELL INTO THE 40S AT
THE COOLER INTERIOR LOCATIONS.
FRI...AS THE UPR RDG AXIS SHIFTS E INTO THE WRN GRT LKS AND DEEP LYR
QVECTOR DVGC/DRY AIR DOMINATE...EXPECT MOSUNNY SKIES. THE DAY SHOULD
ALSO TURN A BIT WARMER WITH LARGE SCALE SUBSIDENCE/RETURN SLY FLOW
ON THE WRN FLANK OF SFC HI PRES SHIFTING OVER LOWER MI LIFTING H85
TEMPS UP NEAR 15C OVER THE W BY 00Z SAT. LK BREEZES THAT DVLP NEAR
LK MI AND LK SUP E OF THE KEWEENAW UNDER THE WEAKER PRES GRADIENT
CLOSER TO THE DEPARTING SFC HI PRES WL ALLOW FOR SOME COOLING NEAR
THE LK SHORES IN THOSE AREAS.
FRI NGT...STRENGTHENING SSW WIND ON THE WRN FLANK OF SLOWLY
DEPARTING SFC HI PRES WL LIMIT NOCTURNAL COOLING...ESPECIALLY NEAR
LK SUP OVER THE W HALF WHERE THE STRONGER S WIND UNDER SHARPEST PRES
GRADIENT WL DOWNSLOPE AND SOME HI CLDS SPILLING OVER THE SLOWLY
APRCHG UPR RDG AXIS WL ARRIVE THRU THE NGT. EXPECT THE COOLEST
OVERNGT LO TEMPS ACROSS THE INTERIOR CENTRAL AND E.
THIS WEEKEND...UPR RDG IN THE PLAINS IS PROGGED TO BUILD INTO THE
UPR LKS IN WAD PATTERN/SSW FLOW BTWN HI PRES DRIFTING INTO THE MID
ATLANTIC STATES AND LOWER PRES IN CENTRAL CANADA. A NUMBER OF THE
EXTENDED MODELS SHOW H85 TEMPS NEARING 20C AND PWAT REACHING 1.50 TO
1.75 INCHES BY SUN...SO THE WX WL TURN WARMER AND MORE HUMID.
WHETHER SHRTWVS RIDING THRU THE ZONAL FLOW ON THE TOP OF THIS UPR
RDG WL INTERACT WITH THE INCRSGLY UNSTABLE AIRMASS AND GENERATE
SHRA/TS IS A SGNFT FCST CONCERN. SUSPECT THE BEST SHOT AT SHRA/TS WL
BE SAT NGT/SUN FOLLOWING DEPARTURE OF DRY AIRMASS AND OVER THE NRN
TIER CLOSER TO THE SHRTWVS TRACKING THRU ONTARIO AND LOWER HGTS.
EXTENDED...THE CWA IS FCST TO REMAIN NEAR THE SRN FLANK OF ZONAL
FLOW OVER SRN CANADA AND ON TOP OF UPR RDG DOMINATING THE CONUS.
THIS SUMMER-LIKE PATTERN WITH RECENT ECMWF/GFS RUNS SHOWING H85
TEMPS NEAR 20C IN VCNTY OF A STNRY FNT IS ONE THAT FAVORS EPISODES
OF SHRA WITH HEAVY RA/PERHAPS SVR TSRA ACCOMPANYING THE PASSAGE OF
SHRTWVS THRU THE UPR LKS/ONTARIO NEAR EDGE OF CAPPING INVRN
ASSOCIATED WITH THE STRONG RDG TO THE S. SPECIFYING THE DAY-TO-DAY
DETAILS IN THIS PATTERN IS IMPOSSIBLE ATTM...SO WL STICK TO THE
CONSENSUS FCST. THE CURRENT CPC DAY 3-7 OUTLOOK DOES INDICATE A
THREAT OF HEAVY RA FOR UPR MI OVER THE WEEKEND AND INTO EARLY NEXT
WEEK. TEMPS WL BE ABV NORMAL.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 731 AM EDT WED AUG 21 2013
EXPECT VFR CONDITIONS AT ALL 3 TAF SITES DESPITE THE CHANCE FOR
SHRA/TSRA THIS AFTERNOON/EVENING WITH THE PASSAGE OF A COLD FRONT.
EXPECT TSRA/SHRA EARLY THIS AFTERNOON AT KIWD AND KCMX WITH A BETTER
CHANCE LATE THIS AFTERNOON/EARLY EVENING AT KSAW WITH THE FRONTAL
PASSAGE.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 250 AM EDT WED AUG 21 2013
OVERALL...EXPECT STRONGEST WINDS /TO AROUND 20KTS/ OVER THE NEXT FEW
DAYS TO BE EARLY THIS MORNING INTO TODAY AS THE PRESSURE GRADIENT
TIGHTENS UP AHEAD OF A COLD FRONT THAT WILL MOVE THROUGH LATE THIS
MORNING INTO THIS EVENING...BUT HIGH OVERWATER STABILITY WITH INFLUX
OF A VERY WARM AIRMASS WILL LIMIT THE INCREASE OF WIND SPEED NEAR
THE COOLER LAKE SURFACE. THE ARRIVAL OF MORE HUMID AIR MAY RESULT IN
SOME FOG FORMATION OVER THE COOLER LAKE WATERS...BUT RESTRICTED THE
FOG FORECAST TO AREAS WHERE SOME SHOWERS OR THUNDERSTORMS ARE
EXPECTED. ANY FOG WILL DISSIPATE THIS AFTERNOON AND EVENING
FOLLOWING A COLD FRONTAL PASSAGE AND THE ARRIVAL OF DRIER AIR.
ANOTHER PERIOD OF STRONGER WINDS /FROM THE SW/ MAY OCCUR ON
SATURDAY NIGHT INTO SUNDAY AS LAKE SUPERIOR SITS BETWEEN A HIGH
PRESSURE SYSTEM TO THE SE AND A TROUGH OF LOW PRESSURE TO THE NW...
BUT HIGH OVERWATER STABILITY WILL REMAIN A LIMITING FACTOR ON HOW
STRONG THE NEAR SURFACE WINDS WILL BECOME.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
UPDATE...SRF
SHORT TERM...TITUS
LONG TERM...KC
AVIATION...TITUS
MARINE...TITUS
AREA FORECAST DISCUSSION
NWS OMAHA/VALLEY NE
630 AM CDT WED AUG 21 2013
.AVIATION...12Z TAFS FOR KOFK...KLNK AND KOMA.
VFR CONDITIONS ARE EXPECTED INTO THE EVENING AS SOUTH WINDS NEAR
15KT AND SCT/BKN MID/HIGH LEVEL CLOUDS MOVE OVER EASTERN NEBRASKA.
A COLD FRONT WILL BE MOVING INTO NORTHEAST NEBRASKA LATE IN THE
DAY...AND WILL APPROACH KOFK BY 04Z. SCATTERED SHOWERS AND
THUNDERSTORMS ARE POSSIBLE ALONG THE FRONT...AFFECTING KOFK FROM
04Z THROUGH THE END OF THE TAF PERIOD...AND THE KLNK AND KOMA
AREAS AFTER 06Z. ATTENDANT MVFR/IFR CONDITIONS COULD OCCUR IN ANY
THUNDERSTORM. SHOWERS AND STORMS WILL LIKELY REMAIN IN THE AREA
THROUGH AT LEAST MIDDAY ON THURSDAY.
DERGAN
&&
.PREV DISCUSSION... /ISSUED 300 AM CDT WED AUG 21 2013/
DISCUSSION...
TEMPERATURES THROUGH THE PERIOD AND RAIN CHANCES LATE TODAY INTO
FRIDAY WILL BE THE MAIN FORECAST CONCERNS.
WV/IR SATELLITE LOOP SHOWS A PULSING AREA OF CONVECTION FROM
SOUTHEAST SOUTH DAKOTA INTO NORTHWEST NEBRASKA AT 07Z IN ADVANCE
OF A WEAK SURFACE COLD FRONT FROM NORTHWEST MINNESOTA INTO FAR
NORTHWEST NEBRASKA. 00Z MODELS SIMILAR IN PLACING ISOLATED TO
WIDELY SCATTERED CONVECTION IN THE VICINITY OF THE FRONT TODAY AND
ESPECIALLY LATE THIS AFTERNOON AS IT WORKS INTO NORTHERN PORTIONS
OF IOWA AND NEBRASKA WITH RAP FORECAST SOUNDINGS SHOWING LITTLE
CAP IN PLACE. CONVECTION LIKELY TO EXPAND DURING THE EVENING AS
LOW LEVEL JET FEEDS INTO THE COMPLEX. SURFACE FRONT STALLS NEAR
THE SOUTHERN NEBRASKA BORDER BY THURSDAY MORNING THEN BEGINS TO
LIFT BACK NORTH DURING THE DAY WITH A CONTINUED CHANCE OF SHOWERS
AND THUNDERSTORMS NORTH AND EAST OF THE BOUNDARY INTO FRIDAY.
SOME COOLING ON THURSDAY...ESPECIALLY NORTH...ASSOCIATED WITH
CLOUDS AND PRECIP BEFORE THE WARM AIR WORKS BACK INTO THE AREA
ON FRIDAY.
EXTENDED PERIOD STILL HOT AND DRY WITH UPPER LEVEL HIGH PRESSURE
CENTERED OVER THE CENTRAL PART OF THE NATION.
FOBERT
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
AREA FORECAST DISCUSSION...UPDATED
NWS NORTH PLATTE NE
624 AM CDT WED AUG 21 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM CDT WED AUG 21 2013
SATELLITE AND LIGHTNING SUGGEST A DISTURBANCE ACROSS NERN UT/NWRN
COLO THIS MORNING. THIS DISTURBANCE SHOULD FIRE OFF THE LARAMIE
RANGE AROUND 18Z MARKING THE START OF CONVECTION LATER THIS
AFTERNOON ACROSS WRN AND EVENTUALLY NCNTL NEB TONIGHT. THE RAP
MODEL SHOWS A TSTM COMPLEX DEVELOPING OFF THE PINE RIDGE AROUND
19Z AND THE HRRR IS VERY BUSY ACROSS THE NEB PANHANDLE AT 20Z. IT
ALSO INDICATES STORM INTENSIFICATION ACROSS HOLT COUNTY IN THE
DEEP MOISTURE SECTOR.
GIVEN THAT THE MODELS ARE SHOWING PRECIPITABLE WATER INCREASING
TO AROUND 1.75 INCHES EAST OF HIGHWAY 83 TONIGHT AND THAT WEAK
WINDS ALOFT WILL PRODUCE STORM MOTION OF 10 KTS OR LESS...LOCALLY
HEAVY RAIN SHOULD DEVELOP IN THIS AREA OF RICH MOISTURE.
ELSEWHERE STORM ACTIVITY SHOULD BE SCATTERED OR LESS. NOTE THAT A
MIDLEVEL COLD FRONT IS OPERATING THIS MORNING ACROSS NRN NEB
WHICH WOULD ACTIVATE SCATTERED CONVECTION EARLY THIS AFTERNOON IN
RESPONSE TO DAYTIME HEATING. A STATIONARY FRONT...CURRENTLY
ACROSS SRN SD SHOULD DRIFT SOUTH INTO NRN NEB AT THE SAME TIME
WITH LOW LEVEL MOISTURE POOLING ALONG THE FRONT ADDING FOCUS TO
THE RAIN EVENT.
WINDS ALOFT ARE WEAK AT 35 KTS OR LESS WHICH WILL LIMIT SEVERE
WEATHER POTENTIAL TO ISOLATED COVERAGE. SCATTERED LIGHT SHOWERS
SHOULD CONTINUE THIS MORNING ALONG THE MID LEVEL FRONT ACROSS NRN
NEB WHICH WOULD THEN INTENSIFY TO THUNDERSTORMS EARLY THIS
AFTERNOON AND PERHAPS APPROACH SEVERE LIMITS LATE THIS AFTERNOON
AS THE DISTURBANCE APPROACHES.
MOISTURE TRANSPORT VECTORS ARE RELATIVELY WEAK THIS AFTERNOON AND
THIS EVENING WHICH WOULD LIMIT THE OVERALL HEAVY RAIN THREAT.
STILL ALL THE GFS ENSEMBLE MEMBERS SHOW A HEAVY RAIN CENTER
DEVELOPING ACROSS NCNTL NEB TONIGHT...LIKELY A RESULT OF THE LOW
LEVEL JET INCREASING TO AROUND 30 KT. NONE OF THE OTHER MODELS
SHOW THIS. THE GEMREG IS THE CLOSEST BUT HAS THE FRONT AND HEAVY
RAIN ACROSS SERN SD WHILE THE NAM AND ECM ARE VERY MODEST WITH
QPF BUT SHOW NCNTL NEB LIKE THE GFS ENSEMBLE.
HIGHS TODAY RANGE FROM THE LOWER 80S NORTH TO MID 90S SOUTH.
EXTENSIVE MID AND HIGH LEVEL CLOUDINESS WILL LIMIT HIGHS.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 330 AM CDT WED AUG 21 2013
MAIN CONCERNS WITH THE LONG TERM FOCUS WITH THUNDERSTORM CHANCES
EARLY ON...THEN TRANSITION INTO TEMPERATURES BY THE WEEKEND INTO
NEXT WEEK.
UPPER LEVEL RIDGE WILL BUILD EAST FROM THE SOUTHERN/CENTRAL
ROCKIES OVER THE CENTRAL PLAINS BY THE WEEKEND. MEANWHILE A WEAK
COLD FRONT WILL DRIFT SOUTH ACROSS THE STATE...THEN BECOMES
REPLACED BY A HIGH PRESSURE BUILDING OVER THE UPPER MISS RVR
VALLEY AND THE GREAT LAKES. A SFC LEE TROUGH DEVELOPS ALONG THE
FRONT...AND REMAINS QUASI-STATIONARY THROUGH THE WEEKEND.
THUNDERSTORM CHANCES INITIALLY ON THURSDAY...GENERALLY
ALONG/NORTH OF THE FRONT...WHERE STEEPER LAPSE RATE PERSIST. ALSO
GOING TO BE ALONG THE NORTHERN SIDE OF THE DEVELOPING RIDGE...AND
ASSOCIATED WITH A MID LEVEL DISTURBANCE. AS THE SHORT WAVE PUSHES
EAST...CHANCE FOR STORMS DIMINISHES THURSDAY NIGHT. THE NEXT
CHANCE FOR STORMS IS ALONG THE HIGHER TERRAIN AND THE LEE SIDE
TROUGH GENERALLY TO THE WEST OF THE CWA. MODELS BRING ANOTHER
DISTURBANCE ACROSS THE ROCKIES SATURDAY WHICH HAS THE POTENTIAL TO
SUSTAIN ACTIVITY INTO THE WESTERN ZONES...AND WILL HAVE SOME LOW
POPS. OTHERWISE RIDGE WILL BRING DRY CONDITIONS.
TEMPERATURES ON THURSDAY ARE EXPECTED TO BE COOL WITH SOME CLOUDS
AND COOLER AIR FROM THE COLD FRONT. 00Z MODEL GUIDANCE HAS COME
IN SEVERAL DEGREE ABOVE THE 12Z RUN...HOWEVER FORECAST DOES NOT
JUMP AS FAR AS GUIDANCE YET...AS EXPECT THE CLOUDS TO KEEP TEMPS
IN THE LOWER TO MID 80S. BY FRIDAY THE WARM UP BEGINS...AS HIGH
RETURN TO WELL ABOVE NORMAL 90S FOR THE WEEKEND AND TO START NEXT
WEEK.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 620 AM CDT WED AUG 21 2013
THERE IS NO CHANGE TO THE FORECAST THINKING THROUGH 06Z TONIGHT.
SCATTERED TO OCCASIONALLY NUMEROUS TSTMS ARE EXPECTED TO DEVELOP
FROM ROUGHLY 21Z THIS AFTN ONWARD THROUGH 06Z TONIGHT. MOST OF THE
TSTM ACTIVITY SHOULD BE LOCATED EAST OF HIGHWAY 83 WITH COVERAGE
DECREASING WESTWARD. OTHERWISE VFR IS EXPECTED WITH MID AND HIGH
LEVEL CLOUDINESS.
AFTER 06Z...THE LATEST MODEL GUIDANCE SUGGESTS STORM ACTIVITY WILL
BECOME ISOLATED WEST OF HIGHWAY 83 BUT CONTINUE IN ERNEST EAST OF
HIGHWAY 83.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...CDC
LONG TERM...MASEK
AVIATION...CDC
AREA FORECAST DISCUSSION
NWS RALEIGH NC
1027 AM EDT WED AUG 21 2013
.SYNOPSIS...
AN UPPER LEVEL TROUGH WILL APPROACH THE CAROLINAS FROM THE WEST THIS
EVENING...THEN TRACK EAST ACROSS THE REGION ON THURSDAY. SURFACE
HIGH PRESSURE WILL STRENGTHEN ACROSS THE OHIO VALLEY IN THE WAKE OF
THE UPPER LEVEL TROUGH...DRIVING A COLD FRONT SOUTHWARD INTO THE
CAROLINAS DURING THE DAY FRIDAY.
&&
.NEAR TERM /TODAY AND TONIGHT/...
AS OF 1025 AM WEDNESDAY...
THE LATEST SURFACE ANALYSIS SHOWED A DIFFUSE FRONT ALONG THE
CAROLINA COAST WITH WEAK HIGH PRESSURE REMAINING OVER CENTRAL NORTH
CAROLINA WEST OF THE FRONT. IN THE SOUTHWEST FLOW ALOFT...WEAK
DIFFLUENCE ON WATER VAPOR AND A MID-LEVEL SHORTWAVE IN A MOIST FLOW
ALOFT HELPED TO PRODUCE SCATTERED TO NUMEROUS SHOWERS MAINLY ALONG
AND NORTH OF U.S. 64 THIS MORNING. THESE SHOWERS WILL CONTINUE TO
MOVE NORTHEAST LEAVING A PERIOD OF ISOLATED TO SCATTERED SHOWERS AS
THE MID-LEVEL WAVE CONTINUES TO MOVE NORTHEAST. DURING THE
AFTERNOON...PRECIPITABLE WATER VALUES WILL REMAIN NEAR TWO INCHES...
AND MODEST HEATING SHOULD BE SUFFICIENT TO RESULT IN MLCAPE IN THE
LOWEST KM FROM 500J/KG TO 1500J/KG...GREATEST TOWARD THE COASTAL
PLAIN. 1000-500MB LAPSE RATES ARE ONLY FORECAST TO BE 6C/KM OR LESS.
THE RUC ACTUALLY FORECASTS WEAK SUBSIDENCE THIS AFTERNOON IN THE
WAKE OF THE MID-LEVEL SHORTWAVE...AND THE GFS BUFR SOUNDINGS ARE
SOMEWHAT CAPPED TO DEEP CONVECTION. ON THE OTHER HAND...MODIFIED
MORNING SOUNDINGS AND RUC AND NAM BUFR SOUNDINGS SUGGEST ENOUGH
INSTABILITY TO PROVIDE FOR ISOLATED-TO-SCATTERED SHOWERS AND
THUNDERSTORMS THIS AFTERNOON INTO EARLY THIS EVENING. THE HIGHEST
PROBABILITY OF ANY SHOWERS SHOULD BE OVER THE NORTHWEST PIEDMONT
WHERE 850MB THETA-E AND K INDICES ARE HIGHEST...CLOSER TO WHERE THE
BETTER 0-3KM SHEAR WILL BE FOR MOST OF THE AFTERNOON RELATIVE TO THE
REST OF CENTRAL NORTH CAROLINA...AND WHERE THE RUC SHOWS AN SLIGHT
INCREASE IN 850MB WINDS. TEMPERATURES STILL MOSTLY BELOW NORMAL WITH
HIGHS IN THE 80S.
TONIGHT...EXPECT CHANCES FOR SHOWERS TO DIMINISH WITHIN A FEW HOURS
AFTER SUNSET...THOUGH A TOKEN SLIGHT CHANCE WILL PERSIST GIVEN SUCH
DEEP MOISTURE AND MARGINAL HEIGHT FALLS ALOFT AS THE UPPER LEVEL
WAVE TRACKS INTO THE MID-ATLANTIC TO THE NORTH OF CENTRAL NORTH
CAROLINA. LOWS TONIGHT SIMILAR TO PREVIOUS NIGHTS IN THE 68-73F
RANGE.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 300 AM WEDNESDAY...
A PRE-FRONTAL TROUGH WILL SET UP OVER THE EASTERN PIEDMONT/SANDHILLS
THURSDAY AS THE MEAN FLOW BECOMES MORE WESTERLY IN THE REAR OF THE
DEPARTING MID/UPPER TROUGH OFFSHORE. THIS SHOULD LEAD TO A REDUCTION
IN THE CHANCE OF CONVECTION EXCEPT ALONG AND EAST OF THE TROUGH
THURSDAY AFTERNOON INTO THE EVENING. QPF OF AROUND 0.25 WILL BE
FORECAST FROM AROUND KFAY NE TO KRDU AND RWI (AREAL AVERAGE)... WITH
0.01 TO THE WEST OVER THE TRIAD REGION. CHANCE POP ALL ZONES BUT
ONLY LOW CHANCE (25-30 PERCENT) NW... TO 50 IN THE SE. HIGHS SHOULD
REBOUND INTO THE MID TO UPPER 80S EXCEPT AROUND 90 IN THE SE. PW`S
WILL ALSO REDUCE TO LESS THAN 1.25 IN THE NW TO AROUND 1.5 IN THE
EAST. DEW POINTS SHOULD MIX OUT INTO THE LOWER TO MID 60S NW...
ENHANCING CONFIDENCE IN THE LOWER POP FORECAST.
THURSDAY NIGHT AND FRIDAY... THE COLD FRONT SHOULD EVENTUALLY
OVERTAKE THE PRE-FRONTAL TROUGH OVER THE SOUTHERN AND EASTERN ZONES
FRIDAY. UNTIL THEN... ANOTHER DAY OF MOSTLY SCATTERED SHOWERS AND
THUNDERSTORMS IS EXPECTED... MAINLY IN THE SOUTH AND EAST (WHERE
PW`S REMAIN NEARLY 1.5 INCHES)... ALONG AND AHEAD OF THE CONVERGENCE
ZONE. THE CHANCE OF SHOWERS/STORMS WILL DIMINISH OVERNIGHT FRIDAY
NIGHT AS THE FRONT SETTLES NEAR THE SC BORDER 12Z SATURDAY. LOWS
65-70. HIGHS FRIDAY WITH A WIND SHIFT TO THE NE... 86-91.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 300 AM WEDNESDAY...
A LARGE UPPER TROUGH IS FORECAST TO BE ANCHORED IN THE WESTERN
ATLANTIC AS AN UPPER RIDGE BECOMES ESTABLISHED OVER THE PLAINS THIS
PERIOD. AN ANOMALOUS MEAN NORTHERLY FLOW WILL RESULT FROM THE GREAT
LAKES AND NEW ENGLAND SOUTHWARD DEEP INTO SC/GA. THIS WILL BE A DRY
AND COOL FLOW FOR LATE AUGUST. SURFACE CAA WILL BE MOST PRONOUNCED
SATURDAY AND SUNDAY AS STRONG (~1026+ MB) SURFACE HIGH PRESSURE
BUILDS INTO NC FROM NY/PA. SATURDAY WILL BE THE DAY WITH THE
STRONGEST DAA AS THE MAIN COLD FRONT WILL BEGIN THE DAY NEAR THE SC
BORDER... BUT SHIFT DEEP INTO SC/GA BY LATE SATURDAY. SENSIBLE
WEATHER... PARTLY TO MOSTLY SUNNY SATURDAY. MOSTLY SUNNY SUNDAY.
CLEAR SATURDAY NIGHT. HIGHS SATURDAY AND SUNDAY SHOULD BE ONLY 80-85
(A GOOD 5-8 DEGREES BELOW NORMAL). LOWS SUNDAY AND MONDAY SHOULD BE
IN THE 50S NORTH... AND LOWER 60S SOUTH (ALMOST 10 DEGREES BELOW
NORMAL).
FOR MONDAY THROUGH TUESDAY... A GRADUAL WARMING TREND BUT STILL DRY.
SURFACE HIGH PRESSURE SHOULD BECOME ANCHORED OVER THE APPALACHIANS
AS THE UPPER RIDGE OVER THE MID-MISSISSIPPI VALLEY REMAINS STRONG.
SENSIBLE WEATHER... MOSTLY CLEAR/MOSTLY SUNNY. LOWS 58-65. HIGHS IN
THE 80S.
&&
.AVIATION /14 WEDNESDAY THROUGH SUNDAY/...
AS OF 1025 AM WEDNESDAY...
24-HR TAF PERIOD:
AREAS OF IFR CEILINGS WILL CONTINUE TO SLOWLY LIFT AND IMPROVE TO
MVFR BY 16Z...BECOMING VFR IN MANY AREAS THEREAFTER THOUGH MOISTURE
WILL PERSIST TO ALLOW SCATTERED MVFR CEILINGS INTO THE AFTERNOON.
EXPECT AN INCREASING POTENTIAL FOR SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS THIS AFTERNOON...WITH THE BEST CHANCE TOWARD THE TRIAD
AND KINT AND KGSO. SHOWERS SHOULD DIMINISH IN COVERAGE THIS EVENING.
AREAS OF SUB-VFR FOG AND CEILINGS CAN BE EXPECTED AGAIN LATE TONIGHT
INTO THURSDAY MORNING GIVEN A MOIST AIRMASS AND SIMILAR PATTERN.
LOOKING AHEAD:
AN INCREASED POTENTIAL FOR SHOWERS AND THUNDERSTORMS CAN BE EXPECTED
THURSDAY/FRIDAY AS A COLD FRONT SLOWLY APPROACHES FROM THE NORTH.
VFR CONDITIONS AND A NORTHEAST BREEZE ARE EXPECTED TO PREVAIL IN THE
WAKE OF THE FRONT SAT/SUN AS DRY HIGH PRESSURE BUILDS INTO THE
MID-ATLANTIC.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...VINCENT
NEAR TERM...DJF/VINCENT
SHORT TERM...BADGETT
LONG TERM...BADGETT
AVIATION...DJF/VINCENT
AREA FORECAST DISCUSSION
NWS RALEIGH NC
655 AM EDT WED AUG 21 2013
.SYNOPSIS...
AN UPPER LEVEL TROUGH WILL APPROACH THE CAROLINAS FROM THE WEST THIS
EVENING...THEN TRACK EAST ACROSS THE REGION ON THURSDAY. SURFACE
HIGH PRESSURE WILL STRENGTHEN ACROSS THE OHIO VALLEY IN THE WAKE OF
THE UPPER LEVEL TROUGH...DRIVING A COLD FRONT SOUTHWARD INTO THE
CAROLINAS DURING THE DAY FRIDAY.
&&
.NEAR TERM /TODAY AND TONIGHT/...
AS OF 330 AM WEDNESDAY...
OVERVIEW:
AN UPPER LEVEL LOW CENTERED OVER INDIANA AT 06Z WILL TRACK EASTWARD
INTO EASTERN OH/KY BY 00Z THIS EVENING...AND INTO THE MID-ATLANTIC
BY 12Z THU. SW FLOW ALOFT TODAY WILL STRENGTHEN AND VEER TOWARD THE
WEST ACROSS THE REGION TONIGHT AS THE UPPER LEVEL WAVE TRACKS INTO
THE MID-ATLANTIC...WITH 30 METER H5 HEIGHT FALLS PROGGED BETWEEN
00-12Z THU. THE BERMUDA RIDGE EXTENDING WESTWARD INTO THE CAROLINAS
WILL WEAKEN THIS AFTERNOON INTO TONIGHT AS A LOW-LEVEL TROUGH
ATTENDANT THE AFOREMENTIONED UPPER LEVEL WAVE PROGRESSES INTO THE
MID-ATLANTIC.
PRECIPITATION CHANCES:
SHOWER ACTIVITY EXTENDING WSW-ENE FROM VUJ-HBI-RDU-RWI AT 07Z THIS
MORNING APPEARS TO BE ASSOCIATED WITH WEAK DPVA FROM SMALL AMPLITUDE
DISTURBANCES EMBEDDED IN SW FLOW ALOFT IN THE PRESENCE OF A VERY
MOIST (2.00" PWAT) AND MARGINALLY UNSTABLE (500-1000 J/KG MUCAPE)
ENVIRONMENT. LATEST RAP GUIDANCE SUGGESTS THE AFOREMENTIONED
SHORTWAVE ENERGY SHOULD LIFT NORTHWARD TOWARD THE N/NW PIEDMONT THIS
MORNING...AND EXPECT THE BEST CHANCE OF SHOWER ACTIVITY ALONG AND
NORTH OF THE I-85 CORRIDOR THROUGH 15Z. THIS AFT/EVE INTO TONIGHT...
CONFIDENCE IN CONVECTIVE COVERAGE...TIMING AND LOCATION IS LOWER
THAN NORMAL. GIVEN A VERY MOIST AIRMASS...500-1500 J/KG MLCAPE AT
PEAK HEATING AND A GOOD PROBABILITY OF SMALL AMPLITUDE WAVES IN SW
(INCREASINGLY WSW) FLOW ALOFT ACROSS THE NORTHERN AND WESTERN
PIEDMONT...ONE WOULD EXPECT ABOVE AVERAGE CHANCES FOR PRECIP... ESP
IN THE N/NW PIEDMONT. THE LATEST CONVECTION ALLOWING MODELS DIFFER
IN TIMING AND COVERAGE...BUT ALL SEEM TO INDICATE A BETTER POTENTIAL
FOR CONVECTION IN THE N/NW PIEDMONT AND PERHAPS ALSO IN THE SE
COASTAL PLAIN IN ASSOC/W THE SEABREEZE AND LIGHT ONSHORE FLOW...
WITH THE BEST CHANCE BETWEEN 20-03Z. THIS SEEMS PRETTY REASONABLE
GIVEN THE SETUP. EXPECT CHANCES TO DIMINISH WITHIN A FEW HRS AFTER
SUNSET...THOUGH A TOKEN SLIGHT CHANCE WILL PERSIST GIVEN SUCH DEEP
MOISTURE AND MARGINAL HEIGHT FALLS ALOFT AS THE UPPER LEVEL WAVE
TRACKS INTO THE MID-ATLANTIC TO THE NORTH OF CENTRAL NC.
TEMPERATURES:
HIGHS TODAY SOMEWHAT CHALLENGING AS IN PREVIOUS DAYS WITH TEMPS
PRIMARILY DEPENDENT ON CLOUD COVER AND CONVECTION. EXPECT HIGHS
GENERALLY IN THE LOWER/MID 80S...WARMEST IN THE COASTAL PLAIN AND
COOLEST IN THE N/NW PIEDMONT WHERE HIGHS IN THE UPPER 70S (SIMILAR
TO WINSTON-SALEM YESTERDAY) ARE NOT OUT OF THE QUESTION. LOWS
TONIGHT SIMILAR TO PREVIOUS NIGHTS IN THE 68-73F RANGE. -VINCENT
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 300 AM WEDNESDAY...
A PRE-FRONTAL TROUGH WILL SET UP OVER THE EASTERN PIEDMONT/SANDHILLS
THURSDAY AS THE MEAN FLOW BECOMES MORE WESTERLY IN THE REAR OF THE
DEPARTING MID/UPPER TROUGH OFFSHORE. THIS SHOULD LEAD TO A REDUCTION
IN THE CHANCE OF CONVECTION EXCEPT ALONG AND EAST OF THE TROUGH
THURSDAY AFTERNOON INTO THE EVENING. QPF OF AROUND 0.25 WILL BE
FORECAST FROM AROUND KFAY NE TO KRDU AND RWI (AREAL AVERAGE)... WITH
0.01 TO THE WEST OVER THE TRIAD REGION. CHANCE POP ALL ZONES BUT
ONLY LOW CHANCE (25-30 PERCENT) NW... TO 50 IN THE SE. HIGHS SHOULD
REBOUND INTO THE MID TO UPPER 80S EXCEPT AROUND 90 IN THE SE. PW`S
WILL ALSO REDUCE TO LESS THAN 1.25 IN THE NW TO AROUND 1.5 IN THE
EAST. DEW POINTS SHOULD MIX OUT INTO THE LOWER TO MID 60S NW...
ENHANCING CONFIDENCE IN THE LOWER POP FORECAST.
THURSDAY NIGHT AND FRIDAY... THE COLD FRONT SHOULD EVENTUALLY
OVERTAKE THE PRE-FRONTAL TROUGH OVER THE SOUTHERN AND EASTERN ZONES
FRIDAY. UNTIL THEN... ANOTHER DAY OF MOSTLY SCATTERED SHOWERS AND
THUNDERSTORMS IS EXPECTED... MAINLY IN THE SOUTH AND EAST (WHERE
PW`S REMAIN NEARLY 1.5 INCHES)... ALONG AND AHEAD OF THE CONVERGENCE
ZONE. THE CHANCE OF SHOWERS/STORMS WILL DIMINISH OVERNIGHT FRIDAY
NIGHT AS THE FRONT SETTLES NEAR THE SC BORDER 12Z SATURDAY. LOWS
65-70. HIGHS FRIDAY WITH A WIND SHIFT TO THE NE... 86-91.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 300 AM WEDNESDAY...
A LARGE UPPER TROUGH IS FORECAST TO BE ANCHORED IN THE WESTERN
ATLANTIC AS AN UPPER RIDGE BECOMES ESTABLISHED OVER THE PLAINS THIS
PERIOD. AN ANOMALOUS MEAN NORTHERLY FLOW WILL RESULT FROM THE GREAT
LAKES AND NEW ENGLAND SOUTHWARD DEEP INTO SC/GA. THIS WILL BE A DRY
AND COOL FLOW FOR LATE AUGUST. SURFACE CAA WILL BE MOST PRONOUNCED
SATURDAY AND SUNDAY AS STRONG (~1026+ MB) SURFACE HIGH PRESSURE
BUILDS INTO NC FROM NY/PA. SATURDAY WILL BE THE DAY WITH THE
STRONGEST DAA AS THE MAIN COLD FRONT WILL BEGIN THE DAY NEAR THE SC
BORDER... BUT SHIFT DEEP INTO SC/GA BY LATE SATURDAY. SENSIBLE
WEATHER... PARTLY TO MOSTLY SUNNY SATURDAY. MOSTLY SUNNY SUNDAY.
CLEAR SATURDAY NIGHT. HIGHS SATURDAY AND SUNDAY SHOULD BE ONLY 80-85
(A GOOD 5-8 DEGREES BELOW NORMAL). LOWS SUNDAY AND MONDAY SHOULD BE
IN THE 50S NORTH... AND LOWER 60S SOUTH (ALMOST 10 DEGREES BELOW
NORMAL).
FOR MONDAY THROUGH TUESDAY... A GRADUAL WARMING TREND BUT STILL DRY.
SURFACE HIGH PRESSURE SHOULD BECOME ANCHORED OVER THE APPALACHIANS
AS THE UPPER RIDGE OVER THE MID-MISSISSIPPI VALLEY REMAINS STRONG.
SENSIBLE WEATHER... MOSTLY CLEAR/MOSTLY SUNNY. LOWS 58-65. HIGHS IN
THE 80S.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
AS OF 645 AM WEDNESDAY...
24-HR TAF PERIOD:
AS OF 11Z THIS MORNING...CONDITIONS RANGED FROM VFR AT THE INT/GSO
TERMINALS TO IFR (CEILINGS) AT RDU TO VLIFR (FOG) AT FAY/RWI. LOW
CEILINGS AND FOG WILL GRADUALLY LIFT AND IMPROVE TO MVFR BETWEEN
12-14Z...BECOMING VFR IN MOST AREAS BY 14-16Z...THOUGH ISOLD/SCT
SHOWER ACTIVITY MAY ALLOW SUB-VFR CONDITIONS TO PERSIST INTO EARLY
AFTERNOON...PRIMARILY AT THE INT/GSO TERMINALS. EXPECT AN INCREASING
POTENTIAL FOR SHOWERS AND THUNDERSTORMS THIS AFTERNOON (18-21Z)...
WITH THE BEST CHANCE LATE THIS AFT/EVE BETWEEN 21-04Z AS AN UPPER
LEVEL DISTURBANCES TRACKS EAST INTO THE MID-ATLANTIC. AREAS OF
SUB-VFR FOG AND CEILINGS CAN BE EXPECTED AGAIN LATE TONIGHT INTO
THURSDAY MORNING GIVEN A MOIST AIRMASS AND SIMILAR PATTERN.
LOOKING AHEAD:
AN INCREASED POTENTIAL FOR SHOWERS AND THUNDERSTORMS CAN BE EXPECTED
THURSDAY/FRIDAY AS A COLD FRONT SLOWLY APPROACHES FROM THE NORTH.
VFR CONDITIONS AND A NORTHEAST BREEZE ARE EXPECTED TO PREVAIL IN THE
WAKE OF THE FRONT SAT/SUN AS DRY HIGH PRESSURE BUILDS INTO THE
MID-ATLANTIC. -VINCENT
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...VINCENT
NEAR TERM...VINCENT
SHORT TERM...BADGETT
LONG TERM...BADGETT
AVIATION...VINCENT
AREA FORECAST DISCUSSION
NWS SIOUX FALLS SD
633 AM CDT WED AUG 21 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 349 AM CDT WED AUG 21 2013
CONVECTION ACROSS CENTRAL SOUTH DAKOTA RUNNING INTO THE CAP AS IT
WORKS EAST OF THE JAMES RIVER VALLEY. THE DYING CONVECTION HAS
PRODUCED HEAT BURSTS OVER THE PAST FEW HOURS IN BOTH CHAMBERLAIN
AND MITCHELL. HRRR SHOWS CONVECTION DEVELOPING IN THE NEXT FEW
HOURS ALONG WEAK BOUNDARY SLOWLY EAKING SOUTH THROUGH THE NORTHERN
CWA THIS MORNING. HAVE SOME 20 POPS TO COVER THE POTENTIAL OF
THIS...BUT STILL NOT CONVINCED THAT STORMS ARE GOING TO BE ABLE TO
GET AROUND THE CAP. AHEAD OF THE BOUNDARY...WILL BE ANOTHER WARM
AND HUMID DAY WITH HEAT INDEX VALUES A FEW DEGREES SHY OF ADVISORY
CRITERIA. MODELS INDICATE THAT A WEAK SHORTWAVE MOVING OUT OF
WESTERN SOUTH DAKOTA THIS MORNING MAY TRY TO INTERACT WITH THE
BOUNDARY POTENTIALLY PRODUCING THUNDERSTORMS ACROSS MAINLY
NORTHWEST IOWA. STEEP MID LEVEL LAPSE RATES LEAD TO MOST UNSTABLE
CAPE VALUES OF 2000-2500 J/KG....THOUGH STILL FAIRLY STRONG CAP TO
OVERCOME. IF STORMS ARE ABLE TO DEVELOP...VEERING PROFILE MAY AID
IN STORM ORGANIZATION...THOUGH WIND SPEEDS ARE SOMEWHAT WEAK. AS
SUCH...THE SEE TEXT SEVERE WEATHER OUTLOOK SEEMS REASONABLE WITH
CHANCE OF CONVECTION BEING VERY CONDITIONAL.
BOUNDARY IS EXPECTED TO STALL ACROSS THE SOUTHERN EDGE OF THE
FORECAST AREA TONIGHT CREATING ADDITIONAL CHANCES FOR
THUNDERSTORMS. TRIMMED BACK THE NORTHERN EXTENT OF POPS TONIGHT
WITH DRIER AIRMASS BEHIND THE FRONT MAKING IT DIFFICULT FOR
SHOWERS AND THUNDERSTORMS TO DEVELOP. EXPECT QUITE A THERMAL
GRADIENT ACROSS THE AREA FROM THE UPPER 50S ACROSS SOUTHWEST
MINNESOTA TO NEAR 70 ACROSS THE SOUTHERN EDGE OF THE FORECAST AREA
NEAR THE FRONT.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 349 AM CDT WED AUG 21 2013
CONVECTION CHANCES ARE SOMEWHAT TRICKY ON THURSDAY AS
BOUNDARY/THEATE ADVECTION LIFTS BACK TO THE NORTH. FORCING APPEARS
TO OUTRUN THE MOISTURE...AS LOW LEVEL MOISTURE APPEARS TO BE HARD TO COME
BY ACROSS THE NORTHERN CWA. THEREFORE...HAVE LIMITED CONVECTION CHANCES TO
SOUTHERN EDGE OF THE FORECAST AREA WHERE THE SLIGHTLY DEEPER
MOISTURE EXISTS.
HUMID CONDITIONS RETURN ON FRIDAY AS THE GULF OPENS BACK UP WITH
SOUTHERLY FLOW FEEDING INTO THE PLAINS. 850 HPA TEMPS WARM TO NEAR
20C DURING THE DAY LEADING TO HIGHS IN THE 80S TO NEAR 90.
STRONG LOW LEVEL JET OF 40-50 KNOTS IS EXPECTED TO DEVELOP FRIDAY
NIGHT. HAVE RAISED LOWS IN SW MN ALONG THE BUFFALO RIDGE AS
EXPOSED LOCATIONS WILL LIKELY HAVE TROUBLE COOLING OFF.
IN THE EXTENDED...SATURDAY THROUGH TUESDAY OF NEXT WEEK...A BROAD
UPPER LEVEL RIDGE REMAINS PARKED OVER THE CENTRAL PORTION OF THE
U.S. THROUGH THE PERIOD. WITH OUR AREA IN A SOUTHERLY FLOW IN
RESPONSE TO SURFACE RIDGING PARKED OVER THE EASTERN PART OF THE
NATION...MUCH ABOVE NORMAL TEMPERATURES WILL BE THE RULE. WITH
PROGGED 850 MB TEMPERATURES IN THE MID AND UPPER 20S C HIGHS WILL
GENERALLY RUN LOWER TO MID 90S EACH DAY...WITH HUMIDITY RETURNING AS
DEWPOINTS CLIMB INTO THE MID AND UPPER 60S. 925 MB TEMPERATURES
WOULD SUPPORT LOWS IN THE UPPER 60S TO LOWER 70S. IN TERMS OF
PRECIPITATION CHANCES DURING THE EXTENDED...MODELS HAVING USUAL
DIFFERENCES WITH REGARD TO MINOR SHORTWAVES ROUNDING THE UPPER THE
LEVEL RIDGE...THOUGH KEPT IT DRY THROUGH THE PERIOD WITH SUPPORT
FROM BOTH THE 00Z ECMWF AND GEM.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 623 AM CDT WED AUG 21 2013
ISOLATED CONVECTION ACROSS SOUTH CENTRAL SOUTH DAKOTA/LOWER JAMES
RIVER VALLEY EARLY THIS MORNING CONTINUES TO WEAKEN...AND EXPECT
THIS TREND TO CONTINUE OVER THE NEXT COUPLE OF HOURS.
OTHERWISE...LOW LEVEL WIND SHEAR IS POSSIBLE AT KSUX THROUGH 14Z
WITH SOUTHWESTERLY LOW LEVEL JET OVER THE AREA. FOR THE REMAINDER
OF THE DAY...EXPECTING VFR CONDITIONS WITH ONLY ISOLATED
THUNDERSTORMS POSSIBLE WITH THE PASSAGE OF A COLD FRONT. THE FRONT
WILL SETTLE JUST TO THE SOUTH OF THE AREA BY TONIGHT...WITH A
BETTER CHANCE OF THUNDERSTORMS MAINLY ALONG THE LOWER MISSOURI
RIVER CORRIDOR INTO NORTHWESTERN IOWA. BRIEF MVFR VISIBILITIES
WILL BE POSSIBLE IN ANY HEAVIER CONVECTIVE ACTIVITY.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
SHORT TERM...
LONG TERM...JM
AVIATION...JM
AREA FORECAST DISCUSSION
NWS HOUSTON/GALVESTON TX
958 AM CDT WED AUG 21 2013
.UPDATE...
MORNING FORECAST UPDATE.
&&
.DISCUSSION...
LATEST RADAR IMAGERY SHOWS A FEW SHOWERS WAY OUT IN THE GULF BUT
REALLY NOT MUCH ACTIVITY THIS MORNING COMPARED TO YESTERDAY.
MOISTURE LEVELS SEEM TO BE LOWER WITH PRECIP WATER VALUES AROUND
1.8-1.9 INCHES PER GOES SOUNDER IMAGERY. SFC ANALYSIS SHOWS A WEAK
RIDGE AXIS FROM HIGH PRESSURE OVER THE SE U.S. WILL DECREASE POPS
THIS MORNING TO 20 PERCENT AS SHOULD GET A FEW SHOWERS LATER THIS
MORNING WITH DAY TIME HEATING. WILL KEEP 30 POPS FOR THE AFTERNOON
AS HEATING INCREASES MORE. LATEST 12Z HRRR KEEPS MOST OF THE
CONVECTION TO SW OF HOUSTON BUT CONVECTION DOES DISSIPATE AROUND
23Z SIMILAR TO YESTERDAY. THINK THAT WILL BE MORE LIKELY THE CASE.
UPDATED FORECAST HAS BEEN ISSUED.
39/45
&&
.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL) 98 74 96 75 95 / 20 20 40 30 20
HOUSTON (IAH) 95 73 94 75 94 / 30 30 40 20 30
GALVESTON (GLS) 90 79 88 80 88 / 30 20 40 20 30
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&
$$
DISCUSSION...39
AREA FORECAST DISCUSSION...UPDATED
NWS AMARILLO TX
615 AM CDT WED AUG 21 2013
.AVIATION...
FOR THE 12Z TAFS...VFR CONDITIONS SHOULD PREVAIL THROUGH THE TAF
PERIOD...WITH ONLY FEW TO SCT HIGH CLOUDS. ANY TSRA SHOULD STAY IN
THE HIGHER TERRAIN OF NM AND CO...WELL WEST OF THE TAF SITES. EXPECT
WINDS GENERALLY SOUTHERLY WITH A DIURNAL TREND ON SPEEDS.
JOHNSON
&&
.PREV DISCUSSION... /ISSUED 331 AM CDT WED AUG 21 2013/
DISCUSSION...
UPPER HIGH WILL PREVAIL ACROSS THE PANHANDLES AND THE CENTRAL PLAINS
STATES THROUGH THE END OF THE WEEK AND EARLY THIS WEEKEND...THEN THE
UPPER HIGH SHIFTS EASTWARD OVER THE MID MISSISSIPPI RIVER VALLEY AREA
BY LATE IN THE WEEKEND THROUGH THE MIDDLE OF NEXT WEEK. SUBSIDENCE
WILL DOMINATE THE FORECAST AREA THROUGH EARLY AND MID NEXT WEEK
KEEPING THE PANHANDLES DRY WITH ABOVE NORMAL TEMPERATURES. ALTHOUGH A
ROGUE THUNDERSTORM DEVELOPED ACROSS THE SOUTHWEST TEXAS PANHANDLE THE
LAST COUPLE OF DAYS DURING THE LATE AFTERNOON AND EARLY EVENING
HOURS...THE NMM MODEL DID FORECAST THIS SCENARIO ON TUESDAY.
HOWEVER...THE NMM...ARW...THE NAM...GFS...RUC AND ECMWF ALONG WITH
THE TTU-WRF AND THE HRRR ARE ALL CONVECTION-FREE AND WILL CONTINUE
WITH A DRY FORECAST. NO MAJOR CHANGES TO THE PREVIOUS GRIDS AND
FORECAST.
SCHNEIDER
FIRE WEATHER...
NO ELEVATED OR CRITICAL FIRE WEATHER CONDITIONS ARE EXPECTED ACROSS
THE TEXAS AND OKLAHOMA PANHANDLES THROUGH THE MIDDLE OF NEXT WEEK.
EITHER THE MINIMUM AFTERNOON RELATIVE HUMIDITIES WILL REMAIN AT OR
ABOVE 20 PERCENT...OR THE 20 FOOT WIND SPEEDS WILL REMAIN AT OR BELOW
15 TO 20 MPH.
SCHNEIDER
&&
.AMA WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
OK...NONE.
&&
$$
16/11
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
957 AM EDT WED AUG 21 2013
.SYNOPSIS...
AN UPPER LEVEL LOW WILL MOVE FROM THE OHIO VALLEY TO THE MID
ATLANTIC COAST BY LATE THURSDAY. A COLD FRONT WILL MOVE FROM THE
GREAT LAKES ON THURSDAY INTO THE CAROLINAS BY SATURDAY. DRIER AND
COOLER HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT FOR THE
WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 950 AM EDT WEDNESDAY...
THE FORECAST THIS MORNING FOR THE MOST PART HAS BEEN ON TRACK. THE
GREATEST CONCENTRATION OF PRECIPITATION HAS BEEN ALONG AND SOUTH
OF THE NC/VA BORDER. OTHER ISOLATED SHOWERS HAVE BEEN NEAR THE
I-64 CORRIDOR OF WV/VA...HOWEVER...MUCH OF THIS DISSIPATED AROUND
930 AM. CURRENTLY...THE NEAR TERM MODEL OF CHOICE IS THE RNK WFR-
ARW. IS HOURLY DEPICTION OF THE PRECIPITATION IN NC HAS MATCHED
VERY WELL THIS MORNING. HAVE USED ITS OUTPUT AS A ROUGH
EXTRAPOLATION OF WHAT IS TO COME THROUGH THE REMAINDER OF THE
MORNING AND THIS AFTERNOON. ITS OUTPUT IS ALSO COMPARABLE TO THE
ONGOING FORECAST FOR TODAY.
WE ARE ANTICIPATING THE WEAK ACTIVITY NEAR THE NC/VA BORDER TO
DECREASE IN SIGNIFICANCE HEADING INTO THE AFTERNOON...WITH OUR
FOCUS SHIFTING TO THE WESTERN HALF OF THE REGION. HERE SHOWERS AND
THUNDERSTORMS ARE EXPECTED TO DEVELOP AND TO COVER 50 TO 70
PERCENT OF THIS REGION THROUGHOUT THE AFTERNOON...WITH COVERAGE
INCREASING ITS GREATEST BETWEEN ROUGHLY 100 PM AND 200 PM.
ELSEWHERE...COVERAGE IS EXPECTED TO BE ISOLATED TO SCATTERED
THROUGH THE MID-AFTERNOON...AND THEN LOOK FOR A SHIFT EASTWARD OF
THE MAIN AREA OF PRECIPITATION THAT WILL IMPACT AREAS PRIMARILY
ALONG AND NORTH OF THE ROUTE 460 CORRIDOR OF VA.
AS OF 410 AM EDT WEDNESDAY...
WHEN I FIRST JOINED THE NATIONAL WEATHER SERVICE MY ELDERS TOLD ME
A CODE THEY WOULD USE WHEN THERE WAS LOW CONFIDENCE IN THE
FORECAST. THEY WOULD APPEND A NUMBER 9 TO THE END OF THEIR NAME
WHEN ISSUING THE FORECAST. TODAY IS DEFINITELY A 9 DAY.
MODELS SHOWING SIGNIFICANT DIFFERENCES IN THE TIMING AND LOCATION
OF PRECIPITATION FOR TODAY AND TONIGHT. HOWEVER...THE LATEST RAP
AND HRRR GUIDANCE HAVE SOMEWHAT OF A REASONABLE TREND WITH THE
PRECIPITATION MOVING NORTH FROM THE CAROLINAS AND THE 00Z LOCAL
WRF SHOWED DECENT CONTINUITY WITH THE PRECIPITATION IN WEST
VIRGINIA.
EXPECT A MAJORITY OF THE PRECIPITATION FROM THE CAROLINAS TO MOVE
THROUGH THE FORECAST AREA THIS MORNING. BY LATE THIS
AFTERNOON...THE UPPER LOW TRACKING WEST OUT OF THE OHIO VALLEY
SHOULD BE TRIGGERING SHOWERS AND THUNDERSTORMS IN THE MOUNTAINS.
AS THIS FEATURE MOVES EAST THIS EVENING...THE COUNTY WARNING AREA
WILL BE IN A FAVORABLE QUADRANT OF THE ASSOCIATED UPPER JET. NET
RESULT IS NOT MUCH CHANGE IN THE PROBABILITY OF PRECIPITATION FOR
TODAY AND TONIGHT.
BUFKIT SHOWED WINDS THROUGH MID LAYERS OF THE ATMOSPHERE LESS THAN
15 KNOTS...WHICH SUGGESTS INDIVIDUAL STORMS THAT DEVELOP MAY BE
MOVING SLOWLY. FLASH FLOOD GUIDANCE IS LESS THAN 2 INCHES FROM THE
NEW RIVER VALLEY AND SOUTHEAST WEST VIRGINIA INTO NORTHWEST NORTH
CAROLINA. WITH PRECIPITABLE WATER VALUES AROUND 1.5 INCHES TODAY
AND TONIGHT HEAVY RAIN REMAINS A THREAT.
TRENDED TOWARD GRIDDED LAMP GUIDANCE FOR MAXIMUM TEMPERATURES
TODAY...BUT WITH CLOUDS AND PRECIPITATION THIS MORNING...WITH BE
COUNTING ON SOME BREAKS IN THE CLOUDS FOR THIS AFTERNOON.
MILD SURFACE DEW POINTS AND CLOUD COVER WILL LIMIT COOLING
OVERNIGHT. LEANED TOWARD WARMER NUMBERS FOR OVERNIGHT LOWS.
&&
.SHORT TERM /THURSDAY THROUGH SATURDAY/...
AS OF 330 AM EDT WEDNESDAY...
UPPER LOW CENTER AROUND LAFAYETTE INDIANA THIS MORNING WILL TRAVEL
EAST AND REACH THE EAST COAST ON FRIDAY. THIS LOW CENTER MOVES INTO
THE ATLANTIC BY SATURDAY...ALLOWING A SURFACE HIGH TO PUSH INTO THE
REGION JUST IN TIME FOR THE WEEKEND.
SHOWERS AND THUNDERSTORMS WILL DEVELOP AHEAD OF THE COLD FRONT ON
THURSDAY. KEPT THE ISOLATED TO SCATTERED POPS IN FOR THURSDAY. WENT
WITH HIGH TEMPERATURES CLOSER TO THE COOLER ADJMET WITH READINGS
FROM THE MID 70S IN THE MOUNTAINS TO THE MID 80S IN THE SOUTHEAST.
A COLD FRONT WILL CROSS THE REGION THURSDAY NIGHT INTO FRIDAY.
PLACED THE HIGHEST POPS (GOOD CHANCE TO LIKELY) IN THE WEST THURSDAY
NIGHT INTO FRIDAY. LEANED TOWARDS THE WARMER MOS LOW TEMPERATURES
THURSDAY NIGHT WITH READINGS FROM THE LOWER 60S IN THE MOUNTAINS TO
NEAR 70 DEGREES IN THE PIEDMONT. HIGHS ON FRIDAY WILL VARY FROM THE
LOWER 70S IN THE WEST TO THE UPPER 80S IN THE SOUTHEAST. LOWERED
POPS FRIDAY NIGHT FROM NORTH TO SOUTH. USED THE ENSEMBLE LOWS FRIDAY
NIGHT WITH VALUES FROM LOWER 50S IN THE NORTHWEST TO THE LOWER 60S
IN THE SOUTH. UNDER THE UPPER RIDGE...PLEASANT SATURDAY ON TAP WITH
SUNSHINE AND HIGH TEMPERATURES GENERALLY FROM MID 70S TO THE LOWER
80S.
&&
.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
AS OF 115 PM EDT TUESDAY...
DURING SUNDAY...FLOW AROUND THE SURFACE HIGH WILL BRING SOUTHEAST
FLOW INTO THE SOUTHWEST PART OF THE REGION. THIS MAY YIELD SOME
ISOLATED UPSLOPE SHOWERS. A COLD FRONT IS PROGGED TO TRY TO MAKE ITS
WAY INTO THE NORTHERN PART OF THE AREA MONDAY NIGHT INTO TUESDAY.
THERE MAY BE SOME ISOLATED SHOWERS IN ADVANCE OF THIS FRONT THAT
REACH NORTHERN PARTS OF THE AREA LATE IN THE DAY MONDAY. SEVERAL
WEAK SHORTWAVES WILL DROP SOUTH IN THE NORTHWEST FLOW ALOFT ACROSS
NORTHERN PORTIONS OF OUR REGION TUESDAY INTO WEDNESDAY.
&&
.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
AS OF 135 AM EDT WEDNESDAY...
AREAS OF IFR CIG/VIS WILL DISSIPATE THIS MORNING BY 14Z. LEADING
EDGE OF PRECIPITATION COMING OUT OF THE SOUTHWEST WAS JUST
REACHING THE VIRGINIA/NORTH CAROLINA BORDER AT 7AM. EXPECT
EXPANDING COVERAGE OF SHOWERS AND ISOLATED THUNDERSTORMS THROUGH
16Z EAST OF THE BLUE RIDGE. BEST CHANCE OF SHOWERS AND
THUNDERSTORMS IN THE MOUNTAINS WILL BE AFTER 18Z/2PM BUT WILL
CONTINUE THROUGH THE EVENING.
PATTERN WILL TRANSITION TO MORE TYPICAL OF MID AUGUST THURSDAY...WITH
SOUTHWEST FLOW AND DIURNALLY DRIVEN SHOWERS AND THUNDERSTORMS.
SCATTERED LOW CLOUDS WILL LINGER DURING THE MORNING IN AREAS...
RESULTING IN A MIXTURE OF MVFR AND VFR CONDITIONS...BEFORE
IMPROVING TO MOSTLY VFR BY EARLY AFTERNOON. PATCHY DENSE FOG
WILL ALSO BE AN ISSUE EACH NIGHT.
A FRONTAL BOUNDARY SHOULD MOVE THROUGH BY FRIDAY...POSSIBLY
PROVIDING BETTER COVERAGE OF SHOWERS AND THUNDERSTORMS. BEHIND
THIS FRONT DRIER AIR AND VFR CONDITIONS ARE EXPECTED SATURDAY AND
SUNDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...AMS
NEAR TERM...AMS/DS
SHORT TERM...KK
LONG TERM...DS/KK
AVIATION...AMS/KM
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
744 AM EDT WED AUG 21 2013
.SYNOPSIS...
AN UPPER LEVEL LOW WILL MOVE FROM THE OHIO VALLEY TO THE MID
ATLANTIC COAST BY LATE THURSDAY. A COLD FRONT WILL MOVE FROM THE
GREAT LAKES ON THURSDAY INTO THE CAROLINAS BY SATURDAY. DRIER AND
COOLER HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT FOR THE
WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 410 AM EDT WEDNESDAY...
WHEN I FIRST JOINED THE NATIONAL WEATHER SERVICE MY ELDERS TOLD ME
A CODE THEY WOULD USE WHEN THERE WAS LOW CONFIDENCE IN THE
FORECAST. THEY WOULD APPEND A NUMBER 9 TO THE END OF THEIR NAME
WHEN ISSUING THE FORECAST. TODAY IS DEFINITELY A 9 DAY.
MODELS SHOWING SIGNIFICANT DIFFERENCES IN THE TIMING AND LOCATION
OF PRECIPITATION FOR TODAY AND TONIGHT. HOWEVER...THE LATEST RAP
AND HRRR GUIDANCE HAVE SOMEWHAT OF A REASONABLE TREND WITH THE
PRECIPITATION MOVING NORTH FROM THE CAROLINAS AND THE 00Z LOCAL
WRF SHOWED DECENT CONTINUITY WITH THE PRECIPITATION IN WEST
VIRGINIA.
EXPECT A MAJORITY OF THE PRECIPITATION FROM THE CAROLINAS TO MOVE
THROUGH THE FORECAST AREA THIS MORNING. BY LATE THIS
AFTERNOON...THE UPPER LOW TRACKING WEST OUT OF THE OHIO VALLEY
SHOULD BE TRIGGERING SHOWERS AND THUNDERSTORMS IN THE MOUNTAINS.
AS THIS FEATURE MOVES EAST THIS EVENING...THE COUNTY WARNING AREA
WILL BE IN A FAVORABLE QUADRANT OF THE ASSOCIATED UPPER JET. NET
RESULT IS NOT MUCH CHANGE IN THE PROBABILITY OF PRECIPITATION FOR
TODAY AND TONIGHT.
BUFKIT SHOWED WINDS THROUGH MID LAYERS OF THE ATMOSPHERE LESS THAN
15 KNOTS...WHICH SUGGESTS INDIVIDUAL STORMS THAT DEVELOP MAY BE
MOVING SLOWLY. FLASH FLOOD GUIDANCE IS LESS THAN 2 INCHES FROM THE
NEW RIVER VALLEY AND SOUTHEAST WEST VIRGINIA INTO NORTHWEST NORTH
CAROLINA. WITH PRECIPITABLE WATER VALUES AROUND 1.5 INCHES TODAY
AND TONIGHT HEAVY RAIN REMAINS A THREAT.
TRENDED TOWARD GRIDDED LAMP GUIDANCE FOR MAXIMUM TEMPERATURES
TODAY...BUT WITH CLOUDS AND PRECIPITATION THIS MORNING...WITH BE
COUNTING ON SOME BREAKS IN THE CLOUDS FOR THIS AFTERNOON.
MILD SURFACE DEW POINTS AND CLOUD COVER WILL LIMIT COOLING
OVERNIGHT. LEANED TOWARD WARMER NUMBERS FOR OVERNIGHT LOWS.
&&
.SHORT TERM /THURSDAY THROUGH SATURDAY/...
AS OF 330 AM EDT WEDNESDAY...
UPPER LOW CENTER AROUND LAFAYETTE INDIANA THIS MORNING WILL TRAVEL
EAST AND REACH THE EAST COAST ON FRIDAY. THIS LOW CENTER MOVES INTO
THE ATLANTIC BY SATURDAY...ALLOWING A SURFACE HIGH TO PUSH INTO THE
REGION JUST IN TIME FOR THE WEEKEND.
SHOWERS AND THUNDERSTORMS WILL DEVELOP AHEAD OF THE COLD FRONT ON
THURSDAY. KEPT THE ISOLATED TO SCATTERED POPS IN FOR THURSDAY. WENT
WITH HIGH TEMPERATURES CLOSER TO THE COOLER ADJMET WITH READINGS
FROM THE MID 70S IN THE MOUNTAINS TO THE MID 80S IN THE SOUTHEAST.
A COLD FRONT WILL CROSS THE REGION THURSDAY NIGHT INTO FRIDAY.
PLACED THE HIGHEST POPS (GOOD CHANCE TO LIKELY) IN THE WEST THURSDAY
NIGHT INTO FRIDAY. LEANED TOWARDS THE WARMER MOS LOW TEMPERATURES
THURSDAY NIGHT WITH READINGS FROM THE LOWER 60S IN THE MOUNTAINS TO
NEAR 70 DEGREES IN THE PIEDMONT. HIGHS ON FRIDAY WILL VARY FROM THE
LOWER 70S IN THE WEST TO THE UPPER 80S IN THE SOUTHEAST. LOWERED
POPS FRIDAY NIGHT FROM NORTH TO SOUTH. USED THE ENSEMBLE LOWS FRIDAY
NIGHT WITH VALUES FROM LOWER 50S IN THE NORTHWEST TO THE LOWER 60S
IN THE SOUTH. UNDER THE UPPER RIDGE...PLEASANT SATURDAY ON TAP WITH
SUNSHINE AND HIGH TEMPERATURES GENERALLY FROM MID 70S TO THE LOWER
80S.
&&
.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
AS OF 115 PM EDT TUESDAY...
DURING SUNDAY...FLOW AROUND THE SURFACE HIGH WILL BRING SOUTHEAST
FLOW INTO THE SOUTHWEST PART OF THE REGION. THIS MAY YIELD SOME
ISOLATED UPSLOPE SHOWERS. A COLD FRONT IS PROGGED TO TRY TO MAKE ITS
WAY INTO THE NORTHERN PART OF THE AREA MONDAY NIGHT INTO TUESDAY.
THERE MAY BE SOME ISOLATED SHOWERS IN ADVANCE OF THIS FRONT THAT
REACH NORTHERN PARTS OF THE AREA LATE IN THE DAY MONDAY. SEVERAL
WEAK SHORTWAVES WILL DROP SOUTH IN THE NORTHWEST FLOW ALOFT ACROSS
NORTHERN PORTIONS OF OUR REGION TUESDAY INTO WEDNESDAY.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
AS OF 135 AM EDT WEDNESDAY...
AREAS OF IFR CIG/VIS WILL DISSIPATE THIS MORNING BY 14Z. LEADING
EDGE OF PRECIPITATION COMING OUT OF THE SOUTHWEST WAS JUST
REACHING THE VIRGINIA/NORTH CAROLINA BORDER AT 7AM. EXPECT
EXPANDING COVERAGE OF SHOWERS AND ISOLATED THUNDERSTORMS THROUGH
16Z EAST OF THE BLUE RIDGE. BEST CHANCE OF SHOWERS AND
THUNDERSTORMS IN THE MOUNTAINS WILL BE AFTER 18Z/2PM BUT WILL
CONTINUE THROUGH THE EVENING.
PATTERN WILL TRANSITION TO MORE TYPICAL OF MID AUGUST THURSDAY...WITH
SOUTHWEST FLOW AND DIURNALLY DRIVEN SHOWERS AND THUNDERSTORMS.
SCATTERED LOW CLOUDS WILL LINGER DURING THE MORNING IN AREAS...
RESULTING IN A MIXTURE OF MVFR AND VFR CONDITIONS...BEFORE
IMPROVING TO MOSTLY VFR BY EARLY AFTERNOON. PATCHY DENSE FOG
WILL ALSO BE AN ISSUE EACH NIGHT.
A FRONTAL BOUNDARY SHOULD MOVE THROUGH BY FRIDAY...POSSIBLY
PROVIDING BETTER COVERAGE OF SHOWERS AND THUNDERSTORMS. BEHIND
THIS FRONT DRIER AIR AND VFR CONDITIONS ARE EXPECTED SATURDAY AND
SUNDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...AMS
NEAR TERM...AMS
SHORT TERM...KK
LONG TERM...DS/KK
AVIATION...AMS/KM
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
1049 AM CDT WED AUG 21 2013
NEW INFORMATION ADDED TO UPDATE SECTION
.UPDATE...
ISSUED AT 1038 AM CDT WED AUG 21 2013
NO BIG CHANGES TO THE FORECAST FOR THE REST OF TODAY. A STRONG
COLD FRONT EXTENDS FROM WESTERN LAKE SUPERIOR TO CENTRAL
MINNESOTA. THE FRONT HAS BEEN MOSTLY QUIET SO FAR THIS MORNING
OUTSIDE OF A FEW BLIPS ON THE RADAR. SKIES ARE MOSTLY CLEAR TO
PARTLY CLOUDY AHEAD OF THE FRONT...WHICH SHOULD ALLOW FOR GOOD
HEATING. TEMPS ARE LAGGING BEHIND THE PREVIOUS FORECAST SO DROPPED
THEM A DEGREE. LOOKING AT THE MODELS THIS MORNING...THE NAM AND SREF HAVE
SPED UP THE TIMING OF THE FRONT...HAVING IT REACH NORTHEAST
WISCONSIN AND THE FOX VALLEY LATE IN THE AFTERNOON. THE RUC IS NOT
TOO DIFFERENT...SO THIS MAY BE POSSIBLE. REGARDLESS...ML CAPES
WILL REACH 3K J/KG IF A PARCEL CAN REACH 88/68. WITH TEMPS LAGGING
A LITTLE BIT...2K-3K J/KG SEEMS REASONABLE. SUFFICIENT 0-6KM BULK
SHEAR OF 25-30 KTS WILL BE GOOD ENOUGH TO PRODUCE STORMS
CONTAINING LARGE HAIL AND DAMAGING WINDS. TRIED TO FOLLOW THE NSSL
WRF FOR THE CONVECTIVE EVOLUTION FOR THIS FORECAST. CONVECTIVE
INITIATION LOOKS TO OCCUR AROUND THE 19-20Z TIME PERIOD OVER
NORTHWEST WISCONSIN. STORMS ARE THEN PROJECTED TO REACH THE FOX
VALLEY EARLY THIS EVENING.
&&
.SHORT TERM...TODAY...TONIGHT...AND THURSDAY
ISSUED AT 407 AM CDT WED AUG 21 2013
A SMALL AREA OF SHOWERS AND THUNDERSTORMS WILL MOVE
ACROSS PARTS OF THE FOX VALLEY EARLY THIS MORNING IN AN AREA OF
MID LEVEL WARM ADVECTION AND CONVERGENCE. IT SHOULD EXIT THE AREA
BY SUNRISE OR SHORTLY THEREAFTER. VERY WARM AND HUMID WEATHER
EXPECTED TODAY BEFORE THE ARRIVAL OF A COLD FRONT DURING THE LATE
AFTERNOON AND EVENING HOURS. HEAT INDICES WILL RISE INTO THE 90S
WITH TEMPERATURES IN THE MIDDLE 80S TO LOW 90S.
THE POTENTIAL FOR SEVERE THUNDERSTORMS CERTAINLY EXISTS THIS
AFTERNOON AND EVENING. SIGNIFICANT INSTABILITY...UPPER
DIFFLUENCE...LOW LEVEL WARM ADVECTION AND MOISTURE CONVERGENCE
SHOULD COMBINE TO CREATE AN ENVIRONMENT FAVORABLE FOR STRONG TO
SEVERE STORMS. MID LEVEL WINDS ARE NOT TOO IMPRESSIVE AND
TEMPERATURES ALOFT ARE NOT VERY COLD...BUT INSTABILITY WILL BE
SUBSTANTIAL AND SHOULD HELP PRODUCE STORMS WITH STRONG UPDRAFTS.
THE DAY ONE SEVERE THUNDERSTORM OUTLOOK LOOKS VERY REASONABLE AND
FITS WELL WITH CURRENT THINKING AND HISTORICAL ANALOGS FOR SIMILAR
EVENTS.
THE COLD FRONT WILL EXIT TONIGHT AND PRECIPITATION WILL END FROM
WEST TO EAST. THE AIR BEHIND THE FRONT IS MORE DRY THAN COLD SO
EXPECT LOWS TONIGHT TO BE NEAR OR JUST ABOVE NORMAL BUT WITH MUCH
MORE COMFORTABLE DEW POINTS. TOMORROW SHOULD BE SUNNY AND
SEASONABLE TEMPERATURES AND LOW HUMIDITY.
.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
ISSUED AT 407 AM CDT WED AUG 21 2013
SOMEWHAT OF AN AMPLIFIED FLOW TO TAKE SHAPE INTO EARLY NEXT WEEK
WITH UPR TROFS ALONG THE WEST COAST/NE CONUS AND A BROAD UPR RDG
OVER THE CNTRL/E-CNTRL CONUS. THIS RDG TO INTENSIFY BY THE WEEKEND
WITH BOTH TEMPS AND DEW POINTS GOING ABOVE CLIMATOLOGICAL NORMS
FOR LATE AUGUST. MAIN FCST ISSUE REMAINS LOCATION OF CONVECTIVE
COMPLEXES RIDING THE RIM OF THIS UPR RDG AND WHETHER ANY BACKDOOR
CDFNTS MAY REACH NE WI.
HI PRES IS EXPECTED TO STRETCH FROM ERN ONTARIO SWWD THRU THE
GREAT LAKES BY THU NGT SETTING UP MOSTLY CLEAR SKIES...LIGHT WINDS
AND A DRY ATMOSPHERE WITH DEW POINTS IN THE 40S TO LWR 50S. NEAR
IDEAL RADIATIONAL CONDITIONS WL ALLOW FOR TEMPS TO QUICKLY FALL
THU NGT WITH A FEW LOCATIONS OVER THE NORTH FLIRTING WITH THE 40
DEG MARK. MAY NEED TO TWEAK VALUES DOWN A COUPLE OF DEGS FROM THE
PREVIOUS FCST.
PLEASANT CONDITIONS WL CONT INTO FRI AS THE CENTER OF THIS SFC RDG
SLOWLY SLIDES TO THE EAST...BUT REMAINS THE DOMINANT FEATURE FOR
NE WI. EVEN WITH A COOL START TO THE DAY...MAINLY SUNNY SKIES
COUPLED WITH A DRY AIR MASS IN PLACE...WL STILL ALLOW TEMPS TO
MAKE A PRETTY GOOD JUMP DURING THE DAY. LOOK FOR MAX TEMPS TO
APPROACH THE 80 DEG MARK FOR INLAND AREAS...WHILE LAKESHORE AREAS
TO ONLY REACH THE MID 70S AS THE LAKEBREEZE DEVELOPS AND MOVES
INLAND.
AS THE SFC RDG HEADS INTO THE ERN GREAT LAKES FRI NGT...RETURN
FLOW BEGINS OVER WI AS WINDS JUST ABOVE THE SFC TURN S-SW AND
INCREASE TO AROUND 20 KTS. PRIMARY LOW-LEVEL JET AIMED OVER THE
NRN PLAINS/UPR MS VALLEY WHERE ELEVATED CONVECTION IS EXPECTED.
ANOTHER QUIET NGT FOR THE FCST AREA WITH MIN TEMPS NOT AS COLD AND
THE AIR MASS NOT AS DRY AS THU NGT. LOOK FOR MIN TEMPS TO BE IN
THE LWR 50S NORTH/MID 50S ELSEWHERE.
THE SPRAWLING UPR RDG OVER THE CNTRL CONUS IS PROGGED TO EXPAND
NWD TOWARD THE UPR MS VALLEY/GREAT LAKES REGIONS STARTING THIS
WEEKEND. AS THIS OCCURS...AN INCREASE IN BOTH TEMPS AND DEW POINTS
WL TAKE PLACE AS WELL AS THE POTENTIAL FOR A WRMFNT TO LIFT NORTH
TOWARD/INTO WI. IN ADDITION...A PIECE OF ENERGY IS FCST TO RIDE
THE FRINGE OF THIS UPR RDG ON SAT. WHILE BETTER INSTABILITY AND
DEEPER MOISTUREWL BE TO OUR WEST...CANNOT RULE OUT A CONVECTIVE
COMPLEX MOVING INTO PARTS OF NE WI BY SAT AFTERNOON. MAY NEED TO
RAISE POPS A BIT AS A RESULT. ONCE THE WRMFNT LIFTS TO OUR NORTH
AND THE IMPULSE (ENERGY) SHIFTS TO OUR EAST SAT NGT...PCPN CHCS
LOOK MINIMAL HEADED INTO SUNDAY AS THE UPR RDG REMAINS IN PLACE
AND THE ATMOSPHERE BECOMES CAPPED. 8H TEMPS PUSHING +20C COULD
EASILY SEND MAX TEMPS WELL INTO THE 80S WITH DEW POINTS CLIMBING
INTO THE 60S.
STILL HAVE QUESTIONS AS TO HOW FAR NORTH THIS WRMFNT CAN GET
SUNDAY NGT INTO MON AS THIS FEATURE WL BE THE PRIMARY FOCUSING
MECHANISM FOR ADDITIONAL SHWRS/TSTMS. SOME MDLS KEEP THIS FNT TO
OUR NORTH...THUS ADVERTISING A DRY FCST. HOWEVER...OTHER MDLS
APPEAR TO SHOW CONVECTION HELPING TO SHOVE THIS BOUNDARY A BIT
SOUTH AND LEAVE MUCH OF THE FCT AREA VULNERABLE TO MORE PCPN. TOO
MUCH UNCERTAINTY HERE...THUS HAVE FAVORED THE CONSENUS SOLUTION
WHICH KEEPS CHC POPS IN THE FCST ALONG WITH VERY WARM/MUGGY
CONDITIONS. UNCERTAINTY CARRIES OVER INTO TUE AS THE LONG-TERM
MDLS DIFFER ON HOW LONG THE UPR RDG WL BE ABLE TO MAINTAIN ITSELF.
THERE IS POTENTIAL FOR ANOTHER COMPLEX TO DEVELOP ON THE EDGE OF
THIS UPR RDG...THUS A CONTINUED CHC POP WL ALSO BE NEEDED FOR TUE.
&&
.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 639 AM CDT WED AUG 21 2013
MAINLY VFR WEATHER EXPECTED TODAY UNTIL A COLD FRONT
ARRIVES IN CENTRAL WISCONSIN DURING THE AFTERNOON HOURS AND MOVES
ACROSS THE EASTERN PART OF THE STATE BY EARLY EVENING. IT WILL BE
ACCOMPANIED BY SHOWERS AND THUNDERSTORMS WITH GUSTY WINDS AND
BRIEF IFR CEILINGS AND VISIBILITIES. THE FRONT WILL EXIT TONIGHT
WITH CLEARING EXPECTED BY THURSDAY MORNING. GOOD FLYING WEATHER IS
EXPECTED THURSDAY THROUGH FRIDAY.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE.........MPC
SHORT TERM.....RDM
LONG TERM......KALLAS
AVIATION.......RDM
AREA FORECAST DISCUSSION...CORRECTED SYNOPSIS
NWS PHOENIX AZ
249 PM MST WED AUG 21 2013
.SYNOPSIS...
A GRADUAL INCREASE IN PRECIPITATION CHANCES...AS WELL AS A DECREASE
IN TEMPERATURES...IS EXPECTED OVER THE NEXT SEVERAL DAYS AND INTO
THIS WEEKEND. INCREASED PRECIPITATION CHANCES WILL LINGER THROUGH
EARLY NEXT WEEK.
&&
.DISCUSSION...
WELL-DEFINED VORT MAX ACROSS NORTHERN SONORA CONTINUES ITS TREK
WESTWARD THIS AFTERNOON. SEVERAL SMALLER VORTICES ARE ALSO EVIDENT
ON SATELLITE ACROSS AZ...WHICH HAVE CONTRIBUTED TO A CLOUDY DAY
ACROSS SOUTH-CENTRAL AZ. MEANWHILE...TEMPERATURES HAVE STRUGGLED TO
REACH THE ONE HUNDRED DEGREE MARK IN MANY SPOTS INCLUDING THE
PHOENIX AREA. ISOLATED SHOWERS/SPRINKLES ON THE WESTERN FLANK OF THE
VORT HAVE PERSISTED AS WELL...THOUGH LATEST HRRR INDICATES THAT THEY
WILL GRADUALLY DISSIPATE THIS AFTERNOON.
FURTHER EAST WHERE INSOLATION HAS BEEN STRONGER...ISOLATED
CONVECTION HAS INITIATED AND IS LIKELY BEING AIDED BY INCREASING
DIFFERENTIAL VORTICITY ADVECTION IN THE VICINITY OF GILA COUNTY.
SUITE OF CONVECTIVE ALLOWING MODELS SUGGESTS THAT ACTIVITY WILL
MIGRATE WESTWARD INTO THE LOWER DESERTS...WHERE IT WILL BE MET WITH
INHIBITION FROM THE ANTECEDENT CLOUDINESS. NEVERTHELESS...CONDITIONS
REMAIN SUFFICIENTLY MOIST FOR ISOLATED STORMS. MODELS ARE IN GOOD
AGREEMENT THAT THE PLUME OF DEEPER MOISTURE WILL SHIFT WESTWARD
OVERNIGHT TOWARDS THE LOWER CO RIVER VALLEY AND A SLIGHT CHANCE OF
PRECIPITATION WILL PERSIST AFTER MIDNIGHT IN THESE AREAS. ANY STORMS
THAT DEVELOP WILL BE CAPABLE OF PRODUCING STRONG WIND GUSTS AND
AREAS OF BLOWING DUST.
&&
.PREVIOUS DISCUSSION...
A SLIGHT INCREASE IN MOISTURE IS NOTED FROM THE GFS/EUROPEAN MODELS
ACROSS THE DESERTS ON THURSDAY...MEANWHILE A SLIGHT DECREASE IN MID
LEVEL MOISTURE IS ADVERTISED TO MOVE INTO EASTERN ARIZONA THURSDAY
AFTERNOON. MAY END UP SEEING PRECIP DEVELOP ACROSS THE DESERTS WEST
OF PHOENIX TOWARD THE AZ/CA BORDER THURSDAY AFTERNOON...BUT
INSTABILITY REMAINS MEAGER AND AGAIN...NO OBVIOUS TRIGGER ADVERTISED
ASIDE FROM OROGRAPHIC FORCING. EXPECTING A FAIRLY SIMILAR DAY
THURSDAY WITH STORMS EAST OF PHOENIX AND A FEW ISOLATED SHOWERS TO
THE WEST.
CHANGES APPEAR ON THE HORIZON STARTING AS EARLY AS FRIDAY AS SEVERAL
RUNS OF THE EUROPEAN AND THE GFS INDICATE DEEP SOUTHERLY FLOW ACROSS
THE AREA COURTESY OF AN INVERTED TROUGH OVER MEXICO AND A TROPICAL
SYSTEM SOUTH OF BAJA CALIFORNIA. MOISTURE ADVECTION SHOULD BEGIN ON
FRIDAY...WITH THE REAL PUSH OF 2+ INCH PWATS /12-14 G/KG 1000-700MB
MEAN MIXING RATIOS/ ARRIVING DURING THE DAY ON SATURDAY. GFS
INTEGRATED WATER VAPOR TRANSPORT DATA SUGGESTS THE STRONGEST PUSH OF
MOISTURE AS EARLY AS SATURDAY AFTERNOON...HOWEVER THE EUROPEAN MODEL
APPEARS TO BE 12-18 HRS SLOWER. ITS ALWAYS TOUGH TRYING TO FIGURE
OUT WHEN CONVECTION WILL DEVELOP AFTER SUCH A SIGNIFICANT SURGE OF
MOISTURE. TYPICALLY THE BOUNDARY LAYER IS TOO STABLE FOR STORMS
DURING THE SURGE AND NEED ABOUT 12-24HRS TO RECOVER. WITH THE
BIGGEST INCREASE IN MOISTURE NOTED EARLY SATURDAY...THE GREATEST
CHANCE OF STORMS WOULD SEEMINGLY FOLLOW SATURDAY NIGHT INTO SUNDAY.
I WILL CONTINUE WITH THE TREND OF INCREASING POPS STARTING ON FRIDAY
THROUGH THE DAY SUNDAY WITH THE HIGHEST VALUES /ABOVE 40-50 PERCENT
CWA-WIDE/ ON SUNDAY. NONE OF THE OPERATIONAL MODELS ARE EAGER TO GET
RID OF THE MOISTURE EITHER ONCE IT ARRIVES...WITH BOTH EURO/GFS
MODELS KEEPING MIXING RATIOS NORTH OF 10 G/KG WELL INTO THE MIDDLE
OF NEXT WEEK. WITH A COUPLE OF INVERTED TROUGHS ADVERTISED TO MOVE
THROUGH THE AREA NEXT WEEK...COULD EASILY SEE ABOVE NORMAL PRECIP
CHANCES LINGERING THROUGH NEXT WEEK.
HIGHS AND LOWS SHOULD START CREEPING DOWNWARD EACH DAY AS MOISTURE
STEADILY INCREASES. WEEKEND HIGHS /ESPECIALLY ON SUNDAY/ ARE
ANYBODYS GUESS AT THIS POINT. IF EITHER DAY ENDS UP BEING A
RAINY/CLOUDY DAY...HIGHS COULD BE IN THE 80S. WITH BREAKS IN THE
CLOUDS...PROBABLY LOOKING AT MID 90S OR AROUND 100. BELOW NORMAL
TEMPS SEEMS LIKE A SAFE BET FROM SATURDAY ONWARD GIVEN SUCH HIGH
PWATS.
&&
.AVIATION...
SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA AND KSDL...
EXTENSIVE MID-LEVEL CLOUDS AND A FEW LIGHT VIRGA SHOWERS/SPRINKLES
WILL DIMINISH THIS AFTERNOON WHILE SHOWERS AND THUNDERSTORMS DEVELOP
ACROSS THE HIGH TERRAIN EAST OF PHOENIX. AS WITH YESTERDAY...THE
MAIN THREAT TODAY WILL BE MODEST OUTFLOW WINDS AND A SLIGHT
POTENTIAL FOR SOME BLOWING DUST. THE BACKGROUND WIND FLOW WILL
MOSTLY REMAIN EASTERLY TODAY DUE TO THE COOLER AND CLOUDIER
CONDITIONS...BUT WINDS WILL BE VARIABLE OR SWITCH TO A
WESTERLY/NORTHWESTERLY DIRECTION FOR A FEW HOURS LATE THIS
AFTERNOON.
SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH...
MOSTLY CLEAR SKIES TO PREVAIL THROUGH THE TAF PERIOD...WITH ONLY
SOME PATCHY MID-HIGH LEVEL CLOUDS EXPECTED. WINDS WILL MAINLY BE ON
THE LIGHT SIDE...AND FOLLOW THE USUAL DIURNAL TRENDS.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
A SIGNIFICANT UPSWING IN ATMOSPHERIC MOISTURE CONTENT AND
THUNDERSTORM ACTIVITY IS ANTICIPATED THIS WEEKEND AS MOISTURE FROM
LOW LATITUDES MAKES IT WAY INTO ARIZONA AND SOUTHEAST CALIFORNIA.
THUS HUMIDITIES WILL INCREASE SUBSTANTIALLY. TEMPERATURES WILL ALSO
DECREASE...TO BELOW NORMAL BY SUNDAY...BEFORE INCREASING AGAIN
MONDAY AND TUESDAY TO NEAR NORMAL. STRONGER SOUTHERLY WINDS ARE ALSO
EXPECTED ON SATURDAY...MAINLY OVER SOUTHEAST CALIFORNIA AND
SOUTHWEST ARIZONA...WITH LESS BREEZINESS THEREAFTER EXCEPT FOR
THUNDERSTORM DRIVEN WINDS.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&
$$
VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX
DISCUSSION...HIRSCH
PREVIOUS DISCUSSION...LEINS
AVIATION...KUHLMAN
FIRE WEATHER...KUHLMAN
AREA FORECAST DISCUSSION
NWS PHOENIX AZ
220 PM MST WED AUG 21 2013
.SYNOPSIS...
A GRADUAL INCREASE IN PRECIPITATION CHANCES...AS WELL AS A DECREASE
IN TEMPERATURES...IS EXPECTED OVER THE NEXT SEVERAL DAYS AND INTO
THIS WEEKEND. INCREASED PRECIP CHANCES WILL LINGER THROUGH EARLY
NEXT WEEK.
&&
.DISCUSSION...
WELL-DEFINED VORT MAX ACROSS NORTHERN SONORA CONTINUES ITS TREK
WESTWARD THIS AFTERNOON. SEVERAL SMALLER VORTICES ARE ALSO EVIDENT
ON SATELLITE ACROSS AZ...WHICH HAVE CONTRIBUTED TO A CLOUDY DAY
ACROSS SOUTH-CENTRAL AZ. MEANWHILE...TEMPERATURES HAVE STRUGGLED TO
REACH THE ONE HUNDRED DEGREE MARK IN MANY SPOTS INCLUDING THE
PHOENIX AREA. ISOLATED SHOWERS/SPRINKLES ON THE WESTERN FLANK OF THE
VORT HAVE PERSISTED AS WELL...THOUGH LATEST HRRR INDICATES THAT THEY
WILL GRADUALLY DISSIPATE THIS AFTERNOON.
FURTHER EAST WHERE INSOLATION HAS BEEN STRONGER...ISOLATED
CONVECTION HAS INITIATED AND IS LIKELY BEING AIDED BY INCREASING
DIFFERENTIAL VORTICITY ADVECTION IN THE VICINITY OF GILA COUNTY.
SUITE OF CONVECTIVE ALLOWING MODELS SUGGESTS THAT ACTIVITY WILL
MIGRATE WESTWARD INTO THE LOWER DESERTS...WHERE IT WILL BE MET WITH
INHIBITION FROM THE ANTECEDENT CLOUDINESS. NEVERTHELESS...CONDITIONS
REMAIN SUFFICIENTLY MOIST FOR ISOLATED STORMS. MODELS ARE IN GOOD
AGREEMENT THAT THE PLUME OF DEEPER MOISTURE WILL SHIFT WESTWARD
OVERNIGHT TOWARDS THE LOWER CO RIVER VALLEY AND A SLIGHT CHANCE OF
PRECIPITATION WILL PERSIST AFTER MIDNIGHT IN THESE AREAS. ANY STORMS
THAT DEVELOP WILL BE CAPABLE OF PRODUCING STRONG WIND GUSTS AND
AREAS OF BLOWING DUST.
&&
.PREVIOUS DISCUSSION...
A SLIGHT INCREASE IN MOISTURE IS NOTED FROM THE GFS/EUROPEAN MODELS
ACROSS THE DESERTS ON THURSDAY...MEANWHILE A SLIGHT DECREASE IN MID
LEVEL MOISTURE IS ADVERTISED TO MOVE INTO EASTERN ARIZONA THURSDAY
AFTERNOON. MAY END UP SEEING PRECIP DEVELOP ACROSS THE DESERTS WEST
OF PHOENIX TOWARD THE AZ/CA BORDER THURSDAY AFTERNOON...BUT
INSTABILITY REMAINS MEAGER AND AGAIN...NO OBVIOUS TRIGGER ADVERTISED
ASIDE FROM OROGRAPHIC FORCING. EXPECTING A FAIRLY SIMILAR DAY
THURSDAY WITH STORMS EAST OF PHOENIX AND A FEW ISOLATED SHOWERS TO
THE WEST.
CHANGES APPEAR ON THE HORIZON STARTING AS EARLY AS FRIDAY AS SEVERAL
RUNS OF THE EUROPEAN AND THE GFS INDICATE DEEP SOUTHERLY FLOW ACROSS
THE AREA COURTESY OF AN INVERTED TROUGH OVER MEXICO AND A TROPICAL
SYSTEM SOUTH OF BAJA CALIFORNIA. MOISTURE ADVECTION SHOULD BEGIN ON
FRIDAY...WITH THE REAL PUSH OF 2+ INCH PWATS /12-14 G/KG 1000-700MB
MEAN MIXING RATIOS/ ARRIVING DURING THE DAY ON SATURDAY. GFS
INTEGRATED WATER VAPOR TRANSPORT DATA SUGGESTS THE STRONGEST PUSH OF
MOISTURE AS EARLY AS SATURDAY AFTERNOON...HOWEVER THE EUROPEAN MODEL
APPEARS TO BE 12-18 HRS SLOWER. ITS ALWAYS TOUGH TRYING TO FIGURE
OUT WHEN CONVECTION WILL DEVELOP AFTER SUCH A SIGNIFICANT SURGE OF
MOISTURE. TYPICALLY THE BOUNDARY LAYER IS TOO STABLE FOR STORMS
DURING THE SURGE AND NEED ABOUT 12-24HRS TO RECOVER. WITH THE
BIGGEST INCREASE IN MOISTURE NOTED EARLY SATURDAY...THE GREATEST
CHANCE OF STORMS WOULD SEEMINGLY FOLLOW SATURDAY NIGHT INTO SUNDAY.
I WILL CONTINUE WITH THE TREND OF INCREASING POPS STARTING ON FRIDAY
THROUGH THE DAY SUNDAY WITH THE HIGHEST VALUES /ABOVE 40-50 PERCENT
CWA-WIDE/ ON SUNDAY. NONE OF THE OPERATIONAL MODELS ARE EAGER TO GET
RID OF THE MOISTURE EITHER ONCE IT ARRIVES...WITH BOTH EURO/GFS
MODELS KEEPING MIXING RATIOS NORTH OF 10 G/KG WELL INTO THE MIDDLE
OF NEXT WEEK. WITH A COUPLE OF INVERTED TROUGHS ADVERTISED TO MOVE
THROUGH THE AREA NEXT WEEK...COULD EASILY SEE ABOVE NORMAL PRECIP
CHANCES LINGERING THROUGH NEXT WEEK.
HIGHS AND LOWS SHOULD START CREEPING DOWNWARD EACH DAY AS MOISTURE
STEADILY INCREASES. WEEKEND HIGHS /ESPECIALLY ON SUNDAY/ ARE
ANYBODYS GUESS AT THIS POINT. IF EITHER DAY ENDS UP BEING A
RAINY/CLOUDY DAY...HIGHS COULD BE IN THE 80S. WITH BREAKS IN THE
CLOUDS...PROBABLY LOOKING AT MID 90S OR AROUND 100. BELOW NORMAL
TEMPS SEEMS LIKE A SAFE BET FROM SATURDAY ONWARD GIVEN SUCH HIGH
PWATS.
&&
.AVIATION...
SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA AND KSDL...
EXTENSIVE MID-LEVEL CLOUDS AND A FEW LIGHT VIRGA SHOWERS/SPRINKLES
WILL DIMINISH THIS AFTERNOON WHILE SHOWERS AND THUNDERSTORMS DEVELOP
ACROSS THE HIGH TERRAIN EAST OF PHOENIX. AS WITH YESTERDAY...THE
MAIN THREAT TODAY WILL BE MODEST OUTFLOW WINDS AND A SLIGHT
POTENTIAL FOR SOME BLOWING DUST. THE BACKGROUND WIND FLOW WILL
MOSTLY REMAIN EASTERLY TODAY DUE TO THE COOLER AND CLOUDIER
CONDITIONS...BUT WINDS WILL BE VARIABLE OR SWITCH TO A
WESTERLY/NORTHWESTERLY DIRECTION FOR A FEW HOURS LATE THIS
AFTERNOON.
SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH...
MOSTLY CLEAR SKIES TO PREVAIL THROUGH THE TAF PERIOD...WITH ONLY
SOME PATCHY MID-HIGH LEVEL CLOUDS EXPECTED. WINDS WILL MAINLY BE ON
THE LIGHT SIDE...AND FOLLOW THE USUAL DIURNAL TRENDS.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
A SIGNIFICANT UPSWING IN ATMOSPHERIC MOISTURE CONTENT AND
THUNDERSTORM ACTIVITY IS ANTICIPATED THIS WEEKEND AS MOISTURE FROM
LOW LATITUDES MAKES IT WAY INTO ARIZONA AND SOUTHEAST CALIFORNIA.
THUS HUMIDITIES WILL INCREASE SUBSTANTIALLY. TEMPERATURES WILL ALSO
DECREASE...TO BELOW NORMAL BY SUNDAY...BEFORE INCREASING AGAIN
MONDAY AND TUESDAY TO NEAR NORMAL. STRONGER SOUTHERLY WINDS ARE ALSO
EXPECTED ON SATURDAY...MAINLY OVER SOUTHEAST CALIFORNIA AND
SOUTHWEST ARIZONA...WITH LESS BREEZINESS THEREAFTER EXCEPT FOR
THUNDERSTORM DRIVEN WINDS.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&
$$
VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX
DISCUSSION...HIRSCH
PREVIOUS DISCUSSION...LEINS
AVIATION...KUHLMAN
FIRE WEATHER...KUHLMAN
AREA FORECAST DISCUSSION
NWS TUCSON AZ
215 PM MST WED AUG 21 2013
.SYNOPSIS...ISOLATED TO SCATTERED MOSTLY AFTERNOON AND EVENING
THUNDERSTORMS WILL PREVAIL THROUGH FRIDAY. THEREAFTER...INCREASING
MOISTURE FROM THE GULF OF CALIFORNIA WILL PROVIDE MORE COVERAGE OF
THUNDERSTORMS THIS WEEKEND. ABOVE NORMAL DAYTIME TEMPERATURES WILL
CONTINUE THROUGH FRIDAY FOLLOWED BY A COOLING TREND THIS WEEKEND.
&&
.DISCUSSION...ISOLATED SHOWERS/TSTMS LIMITED TO MAINLY THE HIGHER
TERRAIN OF SRN GRAHAM/COCHISE/ERN SANTA CRUZ COUNTIES AT THIS TIME.
CONVECTIVE DEBRIS CLOUDINESS CONTINUES TO SLOWLY ERODE ACROSS PIMA/
SOUTH CENTRAL PINAL COUNTIES. 21/19Z RUC HRRR FAVORS ERN SECTIONS
WITH PRECIP ECHOES THRU EARLY THIS EVENING FOLLOWED BY ADDITIONAL
WEAK ECHOES SPREADING WWD INTO PIMA/PINAL COUNTIES LATER TONIGHT.
THIS WILL TRANSLATE INTO SCATTERED SHOWERS/TSTMS THRU THIS EVENING
THEN ISOLATED SHOWERS/TSTMS LATE TONIGHT. EXPECT EVEN LESS COVERAGE
OF SHOWERS/TSTMS THUR AFTERNOON AND THUR EVENING.
FOCUS OF ATTENTION ON FRI TO THEN TURN TOWARD A TROPICAL SYSTEM THAT
IS EXPECTED TO CONTINUE TO DEVELOP SW OF SRN BAJA CALIFORNIA. DEEPER
MOISTURE WILL THEN ADVECT NORTHWARD INTO THIS FORECAST AREA THIS
WEEKEND. HAVE MADE ONLY VERY MINOR ADJUSTMENTS TO THE INHERITED
GRIDDED DATA POP FIELDS FRI-MON. THUS...SCATTERED SHOWERS/TSTMS FOR
MUCH OF SE AZ FRI AFTERNOON AND FRI EVENING WITH LESSER COVERAGE OF
SHOWERS/TSTMS LATE FRI NIGHT AND SAT MORNING. PRECIP CHANCES TO
INCREASE BY LATE SAT INTO SUN...WITH SCATTERED TO PERHAPS NUMEROUS
SHOWERS/TSTMS TO OCCUR.
A DEEP GENERALLY SELY FLOW IS PROGGED TO CONTINUE MON-WED. THIS
PATTERN SHOULD YIELD SCATTERED MAINLY AFTERNOON AND EVENING SHOWERS/
TSTMS GENERALLY FROM TUCSON EWD/SWD...AND ISOLATED COVERAGE OF
SHOWERS/TSTMS ACROSS WRN SECTIONS.
HIGH TEMPS THUR-FRI TO GENERALLY BE A FEW DEGS ABOVE NORMAL FOLLOWED
BY A COOLING TREND THIS WEEKEND. WARMER MON-TUE THEN NO SIGNIFICANT
CHANGE IN DAYTIME TEMPS FOR NEXT WED.
&&
.AVIATION...SCT TSRA/SHRA THRU THIS EVENING THEN ISOLD -TSRA/-SHRA
LATE TONIGHT. DRY CONDITIONS EXPECTED THURSDAY MORNING FOLLOWED BY
SCT TSRA/SHRA THURSDAY AFTERNOON. THE STRONGER TSRA WILL PRODUCE
MVFR CIGS/VSBYS...AND POTENTIALLY WIND GUSTS TO AROUND 45 KTS.
OTHERWISE...CLOUD DECKS 8-12K FT AGL AND SURFACE WIND GENERALLY LESS
THAN 10 KTS THRU THURSDAY MORNING OR 22/18Z. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.
&&
.FIRE WEATHER...EXPECT ISOLATED TO SCATTERED MAINLY AFTERNOON AND
EVENING THUNDERSTORMS THROUGH FRIDAY. MOISTURE WILL THEN BE ON THE
INCREASE THIS WEEKEND...RESULTING IN MORE WIDESPREAD SHOWER AND
THUNDERSTORM ACTIVITY. ABOVE NORMAL DAYTIME TEMPERATURES WILL
CONTINUE THROUGH FRIDAY...WITH COOLER TEMPERATURES THIS WEEKEND.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
VISIT US ON FACEBOOK...TWITTER...YOUTUBE...AND AT WEATHER.GOV/TUCSON
BF/GZ
AREA FORECAST DISCUSSION
NWS PUEBLO CO
348 PM MDT WED AUG 21 2013
.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 347 PM MDT WED AUG 21 2013
...FLASH FLOODING/LANDSPOUT THREAT INCREASING...ESPECIALLY FOR
TOMORROW...
CURRENTLY...
SHOWERS AND STORMS ARE MORE ABUNDANT THEN THIS TIME YESTERDAY...WITH
HUNDREDS OF CG STRIKES OCCURRING DURING THE LAST HOUR OVER THE STATE.
A SFC BOUNDARY IS SEEN IN THE MOSAIC RADAR DATA EXTENDING ACROSS
EAST CENTRAL CO AND BECOMING DIFFUSE OVER THE WESTERN PALMER DIVIDE
REGION. TEMPS HAVE RISEN WELL INTO THE 90S ACROSS THE PLAINS...WITH
TEMPS APPROACHING 100 OUT NEAR KLAA.
REST OF TODAY AND TONIGHT...
UPPER MOISTURE WILL CONTINUE TO INCREASE AND EXPECT SCTD SHOWERS AND
STORMS OVER THE HIGHER TRRN THROUGHOUT THIS AFTERNOON. HRRR IS A BIT
AGGRESSIVE OVER THE PIKES PEAK REGION THIS AFTERNOON AND WILL HAVE
TO WATCH THIS AREA FOR FLASH FLOOD PROBLEMS. THE HRRR AGRESSIVENESS
MAY BE IN RESPONSE TO THE BOUNDARY MENTIONED ABOVE. DWPTS HAVE BEEN
MIXING OUT A BIT BUT 30S AND 40S WERE STILL NOTED ACROSS THE
MTNS...WITH 40S AND 50S OVER THE PLAINS. WE WILL ALSO SEE A BETTER
CHANCE OF TSRA OVER THE PLAINS LATE THIS
AFTERNOON/EVENING...ESPECIALLY OVER THE PALMER DVD AND RATON MESA
REGION. WITH THE BOUNDARY OVER THE PALMER...MAY HAVE TO WATCH OUT
FOR A LANDSPOUT...ALBEIT THE PROBABILITY OF THIS IS LOW.
LATER TONIGHT I ANTICIPATE IT TO BE MAINLY DRY WITH PARTLY CLOUDY
SKIES.
THURSDAY...
BY TOMORROW AFTERNOON...BOUNDARY SHOULD LIE FROM KTAD TO NEAR KLAA.
NORTH OF THE FRONT...MOIST UPSLOPE FLOW WILL BE IN PLACE AND WE WILL
SEE A BETTER CHANCE OF STORMS OVER THE PLAINS. WITH THE BOUNDARY
OVER FAR SE CO...A BETTER CHANCE OF A LANDSPOUT TORNADO WILL BE
POSSIBLE...ESPECIALLY CONSIDERING THIS BOUNDARY WILL BE "COOKING"
ALL DAY TOMORROW AND CAPES SHOULD BE ABOUT 1000 J/KG AND WINDS
THROUGHOUT THE COLUMN WILL BE LIGHT.
FLASH FLOOD THREAT OVER THE BURN SCARS WILL BE HIGHER TOMORROW AS
MOISTURE WILL BE MORE ABUNDANT THROUGHOUT THE COLUMN...CAPES WILL BE
ABOUT 1500-2000 ACROSS THE PIKES PEAK REGION AND FLOW WILL BE RATHER
WEAK. THE LOCAL WRF HAS OVER AN INCH OF RAIN OVER THE WALDO LATE
TOMORROW AFTERNOON. CONTEMPLATED ON ISSUING A FLASH FLOOD WATCH BUT
THOUGHT IT BEST TO LET THE MID CREW ISSUE AS THEY WILL HAVE A COUPLE
MORE GUIDANCE RUNS TO LOOK AT.
EXPECT MAX TEMPS TO BE COOLER TOMORROW AS WE WILL SEE MORE CLOUDS
AND LOW LVL MOISTURE OVER THE REGION. HIGHS SHOULD ONLY BE IN THE
90-96F RANGE OVER THE PLAINS...WITH U80S OVER THE PALMER/RATON MESA
REGION. /HODANISH
.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 347 PM MDT WED AUG 21 2013
LONGER TERM METEOROLOGICAL ISSUES REMAIN POPS AND TEMPERATURES.
SOME ADJUSTMENTS NEEDED FOR LONGER CYCLE AS UPPER RIDGE IS NOW
PROJECTED TO NOT PUSH AS FAR EAST AS EARLIER INDICATED...MEANING
THAT PRIMARY MOISTURE PLUME SHOULD REMAIN OVER WESTERN PORTIONS OF
THE FORECAST DISTRICT AND POINTS WEST DURING THE LONGER TERM.
THE UPPER RIDGE OF HIGH PRESSURE CENTERED OVER SOUTHERN COLORADO
THIS AFTERNOON IS STILL EXPECTED TO BECOME CENTERED OVER KANSAS
AND OKLAHOMA BY LATER FRIDAY NIGHT BEFORE SHIFTING INTO
MISSOUR(INSTEAD OF OVER ILLINOIS AS SOME PREVIOUS MODEL RUNS HAVE
INDICATED) BY WEDNESDAY.
AS THE UPPER RIDGE PUSHES EAST...FORECAST DISTRICT SHOULD STILL
EXPERIENCE INCREASING ATMOSPHERIC MOISTURE VALUES AT TIMES
...ESPECIALLY OVER WESTERN HIGHER TERRAIN LOCATIONS DURING THE
LONGER TERM.
AT THIS TIME...IT APPEARS THAT THE PRIMARY DEEPER MOISTURE FROM
THE DEEP TROPICS OFF THE WEST COAST OF MEXICO SHOULD REMAIN
FOCUSED OVER THE NEW MEXICO...UTAH AND WESTERN COLORADO REGION FROM
THIS WEEKEND INTO EARLY NEXT WEEK...THEREFORE WESTERN BURN SCARS
SUCH AS THE WEST FORK COMPLEX SHOULD NOTE THE HIGHEST POTENTIAL OF
BURN SCAR FLASH FLOODING DURING THIS TIME-FRAME. WFO PUEBLO WILL
CONTINUE TO MONITOR THIS POTENTIAL TREND CLOSELY.
FINALLY...CONTINUED ABOVE SEASONAL LATE AUGUST TEMPERATURES(ESPECIALLY
EASTERN SECTIONS) AS WELL AS GENERALLY LOW-GRADE GRADIENT WINDS
ARE ANTICIPATED OVER THE FORECAST DISTRICT THROUGH THE LONGER TERM.
&&
.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 347 PM MDT WED AUG 21 2013
VFR CONDITIONS ARE ANTICIPATED AT ALL 3 TAF SITES...KPUB...KALS AND
KCOS NEXT 24H. WINDS WILL BE LIGHT AND DIURNALLY DRIVEN. AN ISOLD
TSRA MAY AFFECT THE EACH OF THE TAF SITES LATE TOMORROW AFTERNOON
BUT PROBABILITY OF THIS HAPPENING IS TOO LOW TO MENTION EXPLICITLY
IN TAF PRODUCT.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PUEBLO CO
331 PM MDT WED AUG 21 2013
.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 330 PM MDT WED AUG 21 2013
...FLASH FLOODING/LANDSPOUT THREAT INCREASING...ESPECIALLY FOR
TOMORROW...
CURRENTLY...
SHOWERS AND STORMS ARE MORE ABUNDANT THEN THIS TIME YESTERDAY...WITH
HUNDREDS OF CG STRIKES OCCURRING DURING THE LAST HOUR OVER THE STATE.
A SFC BOUNDARY IS SEEN IN THE MOSAIC RADAR DATA EXTENDING ACROSS
EAST CENTRAL CO AND BECOMING DIFFUSE OVER THE WESTERN PALMER DIVIDE
REGION. TEMPS HAVE RISEN WELL INTO THE 90S ACROSS THE PLAINS...WITH
TEMPS APPROACHING 100 OUT NEAR KLAA.
REST OF TODAY AND TONIGHT...
UPPER MOISTURE WILL CONTINUE TO INCREASE AND EXPECT SCTD SHOWERS AND
STORMS OVER THE HIGHER TRRN THROUGHOUT THIS AFTERNOON. HRRR IS A BIT
AGGRESSIVE OVER THE PIKES PEAK REGION THIS AFTERNOON AND WILL HAVE
TO WATCH THIS AREA FOR FLASH FLOOD PROBLEMS. THE HRRR AGRESSIVENESS
MAY BE IN RESPONSE TO THE BOUNDARY MENTIONED ABOVE. DWPTS HAVE BEEN
MIXING OUT A BIT BUT 30S AND 40S WERE STILL NOTED ACROSS THE
MTNS...WITH 40S AND 50S OVER THE PLAINS. WE WILL ALSO SEE A BETTER
CHANCE OF TSRA OVER THE PLAINS LATE THIS
AFTERNOON/EVENING...ESPECIALLY OVER THE PALMER DVD AND RATON MESA
REGION. WITH THE BOUNDARY OVER THE PALMER...MAY HAVE TO WATCH OUT
FOR A LANDSPOUT...ALBEIT THE PROBABILITY OF THIS IS LOW.
LATER TONIGHT I ANTICIPATE IT TO BE MAINLY DRY WITH PARTLY CLOUDY
SKIES.
THURSDAY...
BY TOMORROW AFTERNOON...BOUNDARY SHOULD LIE FROM KTAD TO NEAR KLAA.
NORTH OF THE FRONT...MOIST UPSLOPE FLOW WILL BE IN PLACE AND WE WILL
SEE A BETTER CHANCE OF STORMS OVER THE PLAINS. WITH THE BOUNDARY
OVER FAR SE CO...A BETTER CHANCE OF A LANDSPOUT TORNADO WILL BE
POSSIBLE...ESPECIALLY CONSIDERING THIS BOUNDARY WILL BE "COOKING"
ALL DAY TOMORROW AND CAPES SHOULD BE ABOUT 1000 J/KG AND WINDS
THROUGHOUT THE COLUMN WILL BE LIGHT.
FLASH FLOOD THREAT OVER THE BURN SCARS WILL BE HIGHER TOMORROW AS
MOISTURE WILL BE MORE ABUNDANT THROUGHOUT THE COLUMN...CAPES WILL BE
ABOUT 1500-2000 ACROSS THE PIKES PEAK REGION AND FLOW WILL BE RATHER
WEAK. THE LOCAL WRF HAS OVER AN INCH OF RAIN OVER THE WALDO LATE
TOMORROW AFTERNOON. CONTEMPLATED ON ISSUING A FLASH FLOOD WATCH BUT
THOUGHT IT BEST TO LET THE MID CREW ISSUE AS THEY WILL HAVE A COUPLE
MORE GUIDANCE RUNS TO LOOK AT.
EXPECT MAX TEMPS TO BE COOLER TOMORROW AS WE WILL SEE MORE CLOUDS
AND LOW LVL MOISTURE OVER THE REGION. HIGHS SHOULD ONLY BE IN THE
90-96F RANGE OVER THE PLAINS...WITH U80S OVER THE PALMER/RATON MESA
REGION. /HODANISH
.LONG TERM...(THURSDAY NIGHT THROUGH NEXT WEDNESDAY)
ISSUED AT 330 PM MDT WED AUG 21 2013
LONGER TERM METEOROLOGICAL ISSUES REMAIN POPS AND TEMPERATURES.
SOME ADJUSTMENTS NEEDED FOR LONGER CYCLE AS UPPER RIDGE IS NOW
PROJECTED TO NOT PUSH AS FAR EAST AS EARLIER INDICATED...MEANING
THAT PRIMARY MOISTURE PLUME SHOULD REMAIN OVER WESTERN PORTIONS OF
THE FORECAST DISTRICT AND POINTS WEST DURING THE LONGER TERM.
THE UPPER RIDGE OF HIGH PRESSURE CENTERED OVER SOUTHERN COLORADO
THIS AFTERNOON IS STILL EXPECTED TO BECOME CENTERED OVER KANSAS
AND OKLAHOMA BY LATER FRIDAY NIGHT BEFORE SHIFTING INTO
NORTH-CENTRAL KANSAS(INSTEAD OF OVER ILLINOIS AS SOME PREVIOUS
MODEL RUNS HAVE INDICATED) BY WEDNESDAY.
AS THE UPPER RIDGE PUSHES EAST...FORECAST DISTRICT SHOULD STILL
EXPERIENCE INCREASING ATMOSPHERIC MOISTURE VALUES AT TIMES
...ESPECIALLY OVER WESTERN HIGHER TERRAIN LOCATIONS DURING THE
LONGER TERM.
AT THIS TIME...IT APPEARS THAT THE PRIMARY DEEPER MOISTURE FROM
THE DEEP TROPICS OFF THE WEST COAST OF MEXICO SHOULD REMAIN
FOCUSED OVER THE NEW MEXICO...UTAH AND WESTERN COLORADO REGION FROM
THIS WEEKEND INTO EARLY NEXT WEEK...THEREFORE WESTERN BURN SCARS
SUCH AS THE WEST FORK COMPLEX SHOULD NOTE THE HIGHEST POTENTIAL OF
BURN SCAR FLASH FLOODING DURING THIS TIME-FRAME. WFO PUEBLO WILL
CONTINUE TO MONITOR THIS POTENTIAL TREND CLOSELY.
FINALLY...CONTINUED ABOVE SEASONAL LATE AUGUST TEMPERATURES(ESPECIALLY
EASTERN SECTIONS) AS WELL AS GENERALLY LOW-GRADE GRADIENT WINDS
ARE ANTICIPATED OVER THE FORECAST DISTRICT THROUGH THE LONGER TERM.
&&
.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 330 PM MDT WED AUG 21 2013
VFR CONDITIONS ARE ANTICIPATED AT ALL 3 TAF SITES...KPUB...KALS AND
KCOS NEXT 24H. WINDS WILL BE LIGHT AND DIURNALLY DRIVEN. AN ISOLD
TSRA MAY AFFECT THE EACH OF THE TAF SITES LATE TOMORROW AFTERNOON
BUT PROBABILITY OF THIS HAPPENING IS TOO LOW TO MENTION EXPLICITLY
IN TAF PRODUCT.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS POCATELLO ID
216 PM MDT WED AUG 21 2013
.DISCUSSION...SHORTWAVE MOVING THROUGH SOUTHEAST IDAHO THIS
AFTERNOON PER SAT IMAGERY WITH STRONGER SHORTWAVE MOVING NORTH
THROUGH NEVADA. LINE OF CONVECTION FROM EARLY THIS MORNING HAS
WEAKENED CONSIDERABLY AS CLOUD BAND HAS SHIFTED NORTH THROUGH
FORECAST AREA. CLEARING BEHIND THE LINE HAS ALLOWED STRONGER
CONVECTION TO FORM IN VERY MOIST AIR MASS. MODELS CONTINUE TO
STRUGGLE EVEN IN SHORT TERM REGARDING INSTABILITY AND PLACEMENT OF
QPF. BEST CHANCES FOR CONVECTION THROUGH THE EVENING APPEAR TO
REMAIN IN SOUTHEAST CORNER WHERE CURRENT STORMS ARE STRONGEST THUS
KEPT POPS HIGHEST THERE. HRRR DEVELOPS SECONDARY WEAKER LINE THROUGH
CENTRAL MOUNTAINS THIS EVENING INTO AREA ALONG DIVIDE LATE. SECOND
PUSH OF CONVECTION SLIDES NORTHEAST INTO EASTERN IDAHO AFTER
MIDNIGHT THOUGH THIS SOLUTION FAVORED ONLY BY GFS DESPITE PLENTY
OF MOISTURE AND CONTINUED WEAK INSTABILITY OVERNIGHT. WILL KEEP
LOW POPS OVER HIGHER ELEVATIONS THROUGH THE NIGHT. UPPER LOW OFF
CALIFORNIA COAST STARTS TO SHIFT NORTHEAST INTO THE CALIFORNIA
COAST BY THURSDAY AFTERNOON. THIS SHOULD BRING ROUND OF CONVECTION
LASTING LATE THURSDAY THROUGH FRIDAY AFTERNOON. TIMING BETWEEN GFS
AND NAM LOOKS SIMILAR WITH BOTH MODELS BRINGING DRY PUSH INTO
WESTERN IDAHO FRIDAY AFTERNOON. MID LEVEL DRY SLOT SLIDES SOMEWHAT
EAST FOR SATURDAY BUT SHOULD BE ENOUGH LOW LEVEL MOISTURE TO KEEP
THE THREAT FOR THUNDERSTORMS GOING PARTICULARLY WITH ENOUGH
CLEARING FOR AFTERNOON. FOR SUNDAY THROUGH WEDNESDAY...GFS
CONTINUES TO ADVERTISE STRONG WET SOUTHERLY FLOW INTO EASTERN
IDAHO. ECMWF SLIGHTLY FURTHER EAST WITH MOISTURE TRAJECTORY. LEFT
AT LEAST WEAK POPS HIGHER ELEVATIONS EACH DAY. DMH
&&
.AVIATION...EXPECT VICINITY THUNDERSTORMS FOR ALL TAF SITES THIS
AFTERNOON INTO EARLY EVENING TODAY AND TOMORROW WITH AN UPPER LEVEL
LOW BRINGING MOISTURE INTO THE AREA. EXPECT GUSTY OUTFLOW WINDS IN
AND AROUND THUNDERSTORMS. KSUN WILL LIKELY BE IMPACTED AGAIN LATE
TONIGHT INTO EARLY MORNING FOR SMOKE. HOWEVER..VISIBILITIES LOOK TO
BE SLIGHTLY GETTING BETTER EACH MORNING. KSUN WILL LIKELY NOT GO
BELOW MVFR TONIGHT INTO TOMORROW MORNING. WYATT
&&
.FIRE WEATHER...MONSOONAL MOISTURE IS IN THE AREA BRINGING ISOLATED
TO SCATTERED THUNDERSTORMS CURRENTLY OVER OUR SOUTHERN AND SOUTHEAST
AREAS. LOOK FOR ISOLATED TO SCATTERED THUNDERSTORMS LATER TODAY FOR
THE REST OF THE AREA PARTICULARLY THE SOUTHERN CENTRAL MOUNTAINS AND
SOUTHWARD. LOOK FOR GUSTY OUTFLOW WINDS AROUND 40 MPH IN AND AROUND
THUNDERSTORMS. ADDITIONALLY...LOCALIZED HEAVY RAIN IS POSSIBLE
CREATING THE POSSIBILITY OF FLASH FLOODING PARTICULARLY OVER BURN
SCAR AREAS. LOOK FOR A REPEAT OF ISOLATED TO SCATTERED THUNDERSTORMS
WITH GUSTY WINDS AND LOCALIZED HEAVY RAIN THURSDAY PARTICULARLY
ACROSS OUR NORTHERN AREAS. EXPECT WINDS TO START TO INCREASE OVER
THE AREA THURSDAY AND PARTICULARLY FRIDAY AS THE UPPER LEVEL LOW
MOVES OVER EASTERN OREGON AND WESTERN IDAHO BY FRIDAY. MODELS
CONTINUE TO SHOW SOUTHEAST IDAHO IN AN ACTIVE PATTERN WITH THE
POSSIBILITY OF AFTERNOON THUNDERSTORMS AIDED BY MONSOON MOISTURE
OVER PORTIONS OF OUR AREA SATURDAY THROUGH THE END OF THE PERIOD.
WYATT
&&
.AIR STAGNATION...AIR QUALITY REMAINS A CONCERN OVER PORTIONS OF
CENTRAL MOUNTAINS DUE TO WILDFIRE SMOKE. WILL CONTINUE AIR QUALITY
ADVISORY AS REQUESTED BY IDAHO DEQ. DMH
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL MIDNIGHT MDT THURSDAY NIGHT IDZ410.
RED FLAG WARNING UNTIL MIDNIGHT MDT THURSDAY NIGHT IDZ413-427.
RED FLAG WARNING UNTIL MIDNIGHT MDT THURSDAY NIGHT
IDZ422-475-476.
RED FLAG WARNING UNTIL MIDNIGHT MDT THURSDAY NIGHT IDZ425.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
240 PM CDT WED AUG 21 2013
.DISCUSSION...
625 AM CDT
HAVE UPDATED THE FORECAST EARLY THIS MORNING TO ACCOUNT FOR MORE
MORNING AND EARLY AFTERNOON CLOUD COVER. WHAT IS LEFT OF A SHEARED
OUT SHORT WAVE ON WATER VAPOR CENTERED ACROSS WI IS HELPING TO
CAUSE ENOUGH ASCENT AND FOCUS FOR 5000-8000 FT CLOUDS ACROSS
NORTHERN IL AND WI. THE RAP 750-850MB CAPTURES THE RH DEPICTION
PRETTY WELL...AND THE SPC WRF COLUMN CONDENSATE DOES TOO ALTHOUGH
A BIT LATE WITH IT. BOTH SHOW INDICATIONS OF THE CLOUDS STICKING
AROUND INTO THIS AFTERNOON AND WITH THE SLOW MOVEMENT OF THE
SHEARED WAVE THAT SEEMS MORE PLAUSIBLE THAN EARLIER. SO HAVE
BUMPED UP SKY COVER QUITE A BIT AND EASED THE TEMPERATURE CLIMB
ALONG WITH BUMPING DOWN HIGHS 2-4 DEGREES IN THE NORTHERN HALF OF
THE AREA. ITS POSSIBLE MORE MAY NEED TO BE PEELED AWAY IF CLOUDS
ARE THICK ENOUGH. CONFIDENCE IS NOT THAT HIGH ON HOW THICK THE
CLOUDS WILL REMAIN AS RAP DIAGNOSTIC SOUNDINGS INDICATE THE RH TO
BE FAIRLY SHALLOW. EVEN IF SCATTERED AT TIMES THOUGH IT LIKELY
WILL SLOW THE TEMPERATURE JUMP...SO FELT ENOUGH CONFIDENCE TO
LOWER THEM SOME.
MTF
//PREV DISCUSSION...
328 AM CDT
THE FORECAST FOCUS WAS FIRST ON THE CHANCES FOR STORMS TONIGHT AND
MAINLY EARLY THU...WHICH EVEN THOUGH THE COVERAGE IS NOT EXPECTED
TO BE PARTICULARLY HIGH THIS IS THE BEST CHANCE FOR RAIN IN OVER A
WEEK. THEN ATTENTION TURNED TO TEMPERATURES WITH LIKELY 90 TODAY
IN MANY COMMUNITIES...THEN A SHORT TERM COOL DOWN FOLLOWED BY AN
APPRECIABLE WARM UP INTO THE FINAL WEEK OF METEOROLOGICAL SUMMER
/ALREADY???/.
TODAY...WHAT HAS BEEN A STAGNANT BUT VERY PLEASANT PATTERN OVER
THE REGION IS BEGINNING TO SHOW SOME SHIFTING EARLY THIS
MORNING...WITH WATER VAPOR SHOWING A STRONG 110 KT+ JET ACROSS FAR
SOUTHERN CANADA BUCKLING SLIGHTLY INTO THE UPPER MIDWEST. MULTIPLE
SHORT WAVES ARE NOTED ACROSS THE NORTHERN ROCKIES AND UPPER
MIDWEST ON THE LEADING EDGE OF THE IMPINGING UPPER TROUGH. AREA
SOUNDINGS LAST EVENING AND VARIOUS SATELLITE CHANNELS CONTINUE TO
INDICATE A FAIRLY DRY MID LEVEL AIR MASS OVER OUR AREA WHICH WILL
TAKE TIME TO SATURATE...SO NOT EXPECTING BLOWOFF FROM ANY MORNING
CONVECTION TO THE NORTHWEST TO REALLY SPREAD OVER WITH ONLY SOME
CUMULUS THROUGH EARLY AFTERNOON. THE THERMAL RIDGE AT 850-925MB IN
ADVANCE OF THE TROUGH LEANS ESE TODAY OVER THE AREA AND THESE
VALUES DO SUPPORT 90 ABOUT A QUARTER OF THE TIME BASED ON LOCAL
CLIMATOLOGY. GIVEN LOCAL HIGHS YESTERDAY AT 87-88 IN MOST
PLACES...UPSTREAM HIGHS IN CENTRAL IA WERE AT 90...AND WITH OUR
DRYING GROUND OFFERING SENSIBLE HEAT TO BE A BIGGER
FACTOR...BELIEVE 88 TO 92 SHOULD PREVAIL ACROSS MUCH OF THE AREA.
DEW POINTS FAVORED IN THE MID TO UPPER 60S WILL ALLOW FOR HEAT
INDEX READINGS TO INCH INTO THE MID 90S IN A SOME COMMUNITIES.
TONIGHT INTO THU MORNING...AS PRIMARY HEIGHT FALLS DEVELOP EAST
ACROSS ONTARIO...THE DEVELOPING SURFACE LOW WILL TRACK EAST UP
THERE...WITH A WEAK SECONDARY LOW /1011MB OR SO/ FAVORED IN
GUIDANCE TO MOVE ALONG THE FRONT FROM IA TO CENTRAL LAKE MI
TONIGHT. THIS FEATURE ALONG WITH THE UPPER TO MID JET TURNING MORE
NORTHWEST GIVING THE FRONT A GOOD PUSH SOUTHWARD ACROSS THE AREA
ON THU. SOME GUIDANCE INDICATES CONVECTION INTO THE AREA THIS
EVE...BUT THAT JUST SEEMS TO QUICK GIVEN THE DRY RH AND LIMITED
MOISTURE TRANSPORT IN ADVANCE OF THE SYSTEM. THE FOCUS OF THE
BOUNDARY CONVERGENCE WILL BE IN WI LATE AFTERNOON AND EVE WITH
SCATTERED POSSIBLY STRONG CONVECTION EXPECTED THERE. GIVEN HIGH
INSTABILITY AND ASSOCIATED DCAPE VALUES UPSTREAM A FEW CLUSTERS
MAY MAKE QUICK PROGRESS SE BY MID TO LATE EVE INTO
OVERNIGHT...ESPECIALLY IF OVER THE LAKE. BUT AGAIN COVERAGE LOOKS
SCATTERED. THIS SYSTEM HAS THE MAKINGS OF A LATE SUMMER FRONT BY
OVERNIGHT WITH WEAKENING SURFACE PRESSURES ALONG IT IN THE WAKE OF
THE AFOREMENTIONED LOW...WEAKENING WARM AIR ADVECTION/DIFFERENTIAL
TEMPERATURE ADVECTION IN ADVANCE OF IT...AND AGAIN LIMITED
MOISTURE. THE DEEP LAYER SHEAR ALSO IS MARGINAL WITH VECTORS
ORIENTED POORLY FOR ANY MCS TYPE ORGANIZATION. OVERALL THE MODEL
SUITE SUPPORTS LIMITED AREAL COVERAGE OF QPF GREATER THAN 0.25 IN.
SO KEEP MAINLY CHANCE POPS EVERYWHERE TONIGHT WITH ONLY MINOR
TWEAKS TO WHAT WAS IN THERE...AND MAINTAIN THE HIGHEST OVERNIGHT.
REST OF THU AND FRI....DRY AIR AND SUPPRESSION MOVE QUICKLY
SOUTHWARD BEHIND THE SURFACE COOL FRONT...WHICH LOOKS TO MOVE
DOWN THE LAKE AND THROUGH CHICAGO SOMETIME IN THE MID-MORNING.
THIS MAY CONTINUE TO SUPPORT SCATTERED SHOWERS AND SOME STORMS
ALONG IT...SO MAINTAIN POPS ESPECIALLY FOR THE SOUTHERN CWA
THROUGH THE DAY. THE PATTERN SUPPORTS TEMPS LIKELY FALLING ALONG
THE LAKE SHORE BY LATE MORNING INTO EARLY AFTERNOON AND REACHING
THEIR PEAK IN OUTLYING AREAS EARLY IN THE AFTERNOON AND THEN
HOLDING STEADY. DRIER AIR REALLY WORKS ITS WAY IN WITHIN THE LOW-
LEVELS THU NIGHT. WITH MOSTLY SUNNY CONDITIONS FRI THIS SHOULD
SUPPORT GOOD MIXING OUT WITH RELATIVE HUMIDITY EXPECTED TO DROP TO
AROUND 30 PERCENT FRI AFTERNOON...AN EARLY SIGN THAT THE NEXT
SEASON IS INDEED NOT FAR AWAY. WITH 850MB TEMPERATURES IN THE MID
TEENS...TEMPS ON FRI LOOK TO BE IN THE MID 70S TO LOWER 80S. FRI
NIGHT SHOULD BE THE COOLEST WITH HIGH PRESSURE STILL PRIMARILY
INFLUENCING THE AREA AND LITTLE CIRRUS EXPECTED. WHILE DEW POINTS
IN THE 40S ARE LIKELY DURING FRI AFTERNOON...THESE SHOULD COME
BACK INTO THE EVE AND LOWS RIGHT NOW LOOK TO BOTTOM OUT IN THE
LOWER TO MID 50S IN MOST OUTLYING LOCATIONS.
BEYOND...THE UPPER RIDGE LOOKS TO BUILD BACK NORTHEAST AS THE
WEEKEND PROGRESSES AND INTO NEXT WEEK...SUPPORTING WARMING
TEMPS AS WELL AS LIKELY PRECIP-FREE CONDITIONS WITH THE FOCUS OF
SYSTEMS AGAIN SHIFTING NORTHWARD. WHILE 90 DEGREES OR WARMER LOOKS
POSSIBLE ON MULTIPLE DAYS WITH MID TO UPPER 60S DEW POINTS...THE
SIGNAL IS STRONGEST ON MON AND TUE WITH THEN SOME BUCKLING DUE TO
POSSIBLE SHORT WAVES/UPSTREAM STORMS. HAVE BLENDED BIAS-
CORRECTED DATA FROM MODELS INTO THE GOING FORECAST WHICH SUPPORTS
WARMER TEMPS THAN A STRAIGHT MODEL BLEND.
MTF
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* CHANCE OF SHRA/TSRA EARLY THURSDAY MORNING AND WIND SHIFT
ASSOCIATED WITH A COLD FRONT PASSAGE.
* CHANCE OF MVFR CIGS THURSDAY MORNING FOR A SHORT PERIOD BEHIND
COLD FRONT.
KREIN
//DISCUSSION...UPDATED 18Z...
CONDITIONS WILL REMAIN QUIET ACROSS THE REGION UNDER SWLY FLOW
AHEAD OF AN APPROACHING COLD FRONT. THE PRIMARY CONCERN FOR THE
PERIOD CONTINUES TO BE THE CHANCES FOR SHOWERS AND THUNDERSTORMS
EARLY TOMORROW MORNING. THE MAIN CHANGE TO THE GOING FORECAST IS
TO INTRODUCE A VCSH GROUP AS MUCH OF THE SHORT RANGE MODEL
GUIDANCE IS INDICATING A CHANCE FOR PRE-FRONTAL PCPN TO MOVE INTO
NRN IL BY ARND 06Z. THERE ARE STILL SOME CONCERNS AS TO THE
COVERAGE OF THE PRE-FRONTAL PCPN...HENCE THE VCSH RATHER THAN A
PREVAILING GROUP WHICH WOULD IMPLY GREATER CONFIDENCE IN MORE
EXTENSIVE COVERAGE. STILL EXPECTING THE FRONTAL PASSAGE AT RFD BY
ARND 12Z AND THE CHICAGO AREA SHORTLY THEREAFTER AS THE SYSTEM
SHOULD BE FAIRLY PROGRESSIVE. WINDS WILL VEER THROUGH NWLY TO
EVENTUALLY NNELY FOLLOWING THE FROPA. THERE IS STILL A CONCERN FOR
A BRIEF PERIOD OF MVFR CIGS OR VIS FOLLOWING THE FROPA AS SOME OF
THE GUIDANCE IS INDICATED A NEARLY SATURATED LAYER BLW
3KFT...THOUGH WOULD ANTICIPATE THAT RFD/DPA WOULD CLIMATOLOGICALLY
HAVE A GREATER CHANCE FOR REDUCED VISBY THAN ORD/MDW. WITHIN A FEW
HOURS OF THE FROPA...DRY AIR THROUGH A DEEP LAYER SHOULD FILTER IN
BEHIND THE FRONT...AND VFR CONDITIONS WITH NNELY WINDS UNDER 10KT
SHOULD PREVAIL FOR THE REMAINDER OF THE DAY TOMORROW.
KREIN
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH THE EARLY
OVERNIGHT HOURS.
* MEDIUM TO HIGH CONFIDENCE IN AT LEAST WIDELY SCATTERED TSRA
INVOF THE TERMINALS EARLY THURSDAY MORNING.
* MEDIUM CONFIDENCE IN PRE-FRONTAL SHRA.
* MEDIUM TO HIGH CONFIDENCE IN TIMING FRONTAL WIND SHIFT AND WIND
TRENDS FOLLOWING THE FROPA..
* LOW CONFIDENCE IN MVFR CIGS/VIS BEHIND THE FRONT EARLY THURSDAY.
KREIN
//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...
THURSDAY NIGHT THROUGH MONDAY...VFR.
TUESDAY...SLT CHC TSRA.
BMD
&&
.MARINE...
202 PM CDT
A COLD FRONT EXTENDED FROM NORTHERN QUEBEC SW ACROSS E LAKE
SUPERIOR...N WI AND S MN AT MID AFTERNOON. THIS COLD FRONT WILL
CONTINUE TO MOVE SE...REACHING N LAKE MI THIS EVENING AND S LAKE
MI THU MORNING....SHIFTING WINDS TO OUT OF THE NW AND N. AS THE
COLD FRONT MOVES OFF TO THE SE DURING THU HIGH PRESSURE WILL MOVE
ESE TO ONTARIO AND THE UPPER MIDWEST. THE HIGH THEN GRADUALLY
SHIFTS SE AND WILL BE OVER QUEBEC...THE GREAT LAKES AND THE OH
VALLEY BY SAT MORNING AND THE MID ATLANTIC SEABOARD AND S
APPALACHIANS BY MON MORNING.
HEIGHT OUTPUT BY LOCALLY RUN WAVE MODEL WOULD APPEAR TO BE LOW
GIVEN MODERATELY STRONG N WINDS THOUGH LOCAL OUTPUT IN LINE WITH
GLERL PRODUCED WAVE HEIGHTS. HOWEVER...WAVE GROWTH WILL BE
LIMITED AS THE AIR MASS BEHIND THE COLD FRONT IS STILL WARM
ENOUGH FOR A TEMPERATURE INVERSION AT THE LAKE SURFACE WHICH WILL
LIMIT MOMENTUM TRANSFER ALL THE WAY DOWN TO THE AIR/WATER
INTERFACE.
TRS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
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AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
203 PM CDT WED AUG 21 2013
.DISCUSSION...
625 AM CDT
HAVE UPDATED THE FORECAST EARLY THIS MORNING TO ACCOUNT FOR MORE
MORNING AND EARLY AFTERNOON CLOUD COVER. WHAT IS LEFT OF A SHEARED
OUT SHORT WAVE ON WATER VAPOR CENTERED ACROSS WI IS HELPING TO
CAUSE ENOUGH ASCENT AND FOCUS FOR 5000-8000 FT CLOUDS ACROSS
NORTHERN IL AND WI. THE RAP 750-850MB CAPTURES THE RH DEPICTION
PRETTY WELL...AND THE SPC WRF COLUMN CONDENSATE DOES TOO ALTHOUGH
A BIT LATE WITH IT. BOTH SHOW INDICATIONS OF THE CLOUDS STICKING
AROUND INTO THIS AFTERNOON AND WITH THE SLOW MOVEMENT OF THE
SHEARED WAVE THAT SEEMS MORE PLAUSIBLE THAN EARLIER. SO HAVE
BUMPED UP SKY COVER QUITE A BIT AND EASED THE TEMPERATURE CLIMB
ALONG WITH BUMPING DOWN HIGHS 2-4 DEGREES IN THE NORTHERN HALF OF
THE AREA. ITS POSSIBLE MORE MAY NEED TO BE PEELED AWAY IF CLOUDS
ARE THICK ENOUGH. CONFIDENCE IS NOT THAT HIGH ON HOW THICK THE
CLOUDS WILL REMAIN AS RAP DIAGNOSTIC SOUNDINGS INDICATE THE RH TO
BE FAIRLY SHALLOW. EVEN IF SCATTERED AT TIMES THOUGH IT LIKELY
WILL SLOW THE TEMPERATURE JUMP...SO FELT ENOUGH CONFIDENCE TO
LOWER THEM SOME.
MTF
//PREV DISCUSSION...
328 AM CDT
THE FORECAST FOCUS WAS FIRST ON THE CHANCES FOR STORMS TONIGHT AND
MAINLY EARLY THU...WHICH EVEN THOUGH THE COVERAGE IS NOT EXPECTED
TO BE PARTICULARLY HIGH THIS IS THE BEST CHANCE FOR RAIN IN OVER A
WEEK. THEN ATTENTION TURNED TO TEMPERATURES WITH LIKELY 90 TODAY
IN MANY COMMUNITIES...THEN A SHORT TERM COOL DOWN FOLLOWED BY AN
APPRECIABLE WARM UP INTO THE FINAL WEEK OF METEOROLOGICAL SUMMER
/ALREADY???/.
TODAY...WHAT HAS BEEN A STAGNANT BUT VERY PLEASANT PATTERN OVER
THE REGION IS BEGINNING TO SHOW SOME SHIFTING EARLY THIS
MORNING...WITH WATER VAPOR SHOWING A STRONG 110 KT+ JET ACROSS FAR
SOUTHERN CANADA BUCKLING SLIGHTLY INTO THE UPPER MIDWEST. MULTIPLE
SHORT WAVES ARE NOTED ACROSS THE NORTHERN ROCKIES AND UPPER
MIDWEST ON THE LEADING EDGE OF THE IMPINGING UPPER TROUGH. AREA
SOUNDINGS LAST EVENING AND VARIOUS SATELLITE CHANNELS CONTINUE TO
INDICATE A FAIRLY DRY MID LEVEL AIR MASS OVER OUR AREA WHICH WILL
TAKE TIME TO SATURATE...SO NOT EXPECTING BLOWOFF FROM ANY MORNING
CONVECTION TO THE NORTHWEST TO REALLY SPREAD OVER WITH ONLY SOME
CUMULUS THROUGH EARLY AFTERNOON. THE THERMAL RIDGE AT 850-925MB IN
ADVANCE OF THE TROUGH LEANS ESE TODAY OVER THE AREA AND THESE
VALUES DO SUPPORT 90 ABOUT A QUARTER OF THE TIME BASED ON LOCAL
CLIMATOLOGY. GIVEN LOCAL HIGHS YESTERDAY AT 87-88 IN MOST
PLACES...UPSTREAM HIGHS IN CENTRAL IA WERE AT 90...AND WITH OUR
DRYING GROUND OFFERING SENSIBLE HEAT TO BE A BIGGER
FACTOR...BELIEVE 88 TO 92 SHOULD PREVAIL ACROSS MUCH OF THE AREA.
DEW POINTS FAVORED IN THE MID TO UPPER 60S WILL ALLOW FOR HEAT
INDEX READINGS TO INCH INTO THE MID 90S IN A SOME COMMUNITIES.
TONIGHT INTO THU MORNING...AS PRIMARY HEIGHT FALLS DEVELOP EAST
ACROSS ONTARIO...THE DEVELOPING SURFACE LOW WILL TRACK EAST UP
THERE...WITH A WEAK SECONDARY LOW /1011MB OR SO/ FAVORED IN
GUIDANCE TO MOVE ALONG THE FRONT FROM IA TO CENTRAL LAKE MI
TONIGHT. THIS FEATURE ALONG WITH THE UPPER TO MID JET TURNING MORE
NORTHWEST GIVING THE FRONT A GOOD PUSH SOUTHWARD ACROSS THE AREA
ON THU. SOME GUIDANCE INDICATES CONVECTION INTO THE AREA THIS
EVE...BUT THAT JUST SEEMS TO QUICK GIVEN THE DRY RH AND LIMITED
MOISTURE TRANSPORT IN ADVANCE OF THE SYSTEM. THE FOCUS OF THE
BOUNDARY CONVERGENCE WILL BE IN WI LATE AFTERNOON AND EVE WITH
SCATTERED POSSIBLY STRONG CONVECTION EXPECTED THERE. GIVEN HIGH
INSTABILITY AND ASSOCIATED DCAPE VALUES UPSTREAM A FEW CLUSTERS
MAY MAKE QUICK PROGRESS SE BY MID TO LATE EVE INTO
OVERNIGHT...ESPECIALLY IF OVER THE LAKE. BUT AGAIN COVERAGE LOOKS
SCATTERED. THIS SYSTEM HAS THE MAKINGS OF A LATE SUMMER FRONT BY
OVERNIGHT WITH WEAKENING SURFACE PRESSURES ALONG IT IN THE WAKE OF
THE AFOREMENTIONED LOW...WEAKENING WARM AIR ADVECTION/DIFFERENTIAL
TEMPERATURE ADVECTION IN ADVANCE OF IT...AND AGAIN LIMITED
MOISTURE. THE DEEP LAYER SHEAR ALSO IS MARGINAL WITH VECTORS
ORIENTED POORLY FOR ANY MCS TYPE ORGANIZATION. OVERALL THE MODEL
SUITE SUPPORTS LIMITED AREAL COVERAGE OF QPF GREATER THAN 0.25 IN.
SO KEEP MAINLY CHANCE POPS EVERYWHERE TONIGHT WITH ONLY MINOR
TWEAKS TO WHAT WAS IN THERE...AND MAINTAIN THE HIGHEST OVERNIGHT.
REST OF THU AND FRI....DRY AIR AND SUPPRESSION MOVE QUICKLY
SOUTHWARD BEHIND THE SURFACE COOL FRONT...WHICH LOOKS TO MOVE
DOWN THE LAKE AND THROUGH CHICAGO SOMETIME IN THE MID-MORNING.
THIS MAY CONTINUE TO SUPPORT SCATTERED SHOWERS AND SOME STORMS
ALONG IT...SO MAINTAIN POPS ESPECIALLY FOR THE SOUTHERN CWA
THROUGH THE DAY. THE PATTERN SUPPORTS TEMPS LIKELY FALLING ALONG
THE LAKE SHORE BY LATE MORNING INTO EARLY AFTERNOON AND REACHING
THEIR PEAK IN OUTLYING AREAS EARLY IN THE AFTERNOON AND THEN
HOLDING STEADY. DRIER AIR REALLY WORKS ITS WAY IN WITHIN THE LOW-
LEVELS THU NIGHT. WITH MOSTLY SUNNY CONDITIONS FRI THIS SHOULD
SUPPORT GOOD MIXING OUT WITH RELATIVE HUMIDITY EXPECTED TO DROP TO
AROUND 30 PERCENT FRI AFTERNOON...AN EARLY SIGN THAT THE NEXT
SEASON IS INDEED NOT FAR AWAY. WITH 850MB TEMPERATURES IN THE MID
TEENS...TEMPS ON FRI LOOK TO BE IN THE MID 70S TO LOWER 80S. FRI
NIGHT SHOULD BE THE COOLEST WITH HIGH PRESSURE STILL PRIMARILY
INFLUENCING THE AREA AND LITTLE CIRRUS EXPECTED. WHILE DEW POINTS
IN THE 40S ARE LIKELY DURING FRI AFTERNOON...THESE SHOULD COME
BACK INTO THE EVE AND LOWS RIGHT NOW LOOK TO BOTTOM OUT IN THE
LOWER TO MID 50S IN MOST OUTLYING LOCATIONS.
BEYOND...THE UPPER RIDGE LOOKS TO BUILD BACK NORTHEAST AS THE
WEEKEND PROGRESSES AND INTO NEXT WEEK...SUPPORTING WARMING
TEMPS AS WELL AS LIKELY PRECIP-FREE CONDITIONS WITH THE FOCUS OF
SYSTEMS AGAIN SHIFTING NORTHWARD. WHILE 90 DEGREES OR WARMER LOOKS
POSSIBLE ON MULTIPLE DAYS WITH MID TO UPPER 60S DEW POINTS...THE
SIGNAL IS STRONGEST ON MON AND TUE WITH THEN SOME BUCKLING DUE TO
POSSIBLE SHORT WAVES/UPSTREAM STORMS. HAVE BLENDED BIAS-
CORRECTED DATA FROM MODELS INTO THE GOING FORECAST WHICH SUPPORTS
WARMER TEMPS THAN A STRAIGHT MODEL BLEND.
MTF
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* CHANCE OF SHRA/TSRA EARLY THURSDAY MORNING AND WIND SHIFT
ASSOCIATED WITH A COLD FRONT PASSAGE.
* CHANCE OF MVFR CIGS THURSDAY MORNING FOR A SHORT PERIOD BEHIND
COLD FRONT.
KREIN
//DISCUSSION...UPDATED 18Z...
CONDITIONS WILL REMAIN QUIET ACROSS THE REGION UNDER SWLY FLOW
AHEAD OF AN APPROACHING COLD FRONT. THE PRIMARY CONCERN FOR THE
PERIOD CONTINUES TO BE THE CHANCES FOR SHOWERS AND THUNDERSTORMS
EARLY TOMORROW MORNING. THE MAIN CHANGE TO THE GOING FORECAST IS
TO INTRODUCE A VCSH GROUP AS MUCH OF THE SHORT RANGE MODEL
GUIDANCE IS INDICATING A CHANCE FOR PRE-FRONTAL PCPN TO MOVE INTO
NRN IL BY ARND 06Z. THERE ARE STILL SOME CONCERNS AS TO THE
COVERAGE OF THE PRE-FRONTAL PCPN...HENCE THE VCSH RATHER THAN A
PREVAILING GROUP WHICH WOULD IMPLY GREATER CONFIDENCE IN MORE
EXTENSIVE COVERAGE. STILL EXPECTING THE FRONTAL PASSAGE AT RFD BY
ARND 12Z AND THE CHICAGO AREA SHORTLY THEREAFTER AS THE SYSTEM
SHOULD BE FAIRLY PROGRESSIVE. WINDS WILL VEER THROUGH NWLY TO
EVENTUALLY NNELY FOLLOWING THE FROPA. THERE IS STILL A CONCERN FOR
A BRIEF PERIOD OF MVFR CIGS OR VIS FOLLOWING THE FROPA AS SOME OF
THE GUIDANCE IS INDICATED A NEARLY SATURATED LAYER BLW
3KFT...THOUGH WOULD ANTICIPATE THAT RFD/DPA WOULD CLIMATOLOGICALLY
HAVE A GREATER CHANCE FOR REDUCED VISBY THAN ORD/MDW. WITHIN A FEW
HOURS OF THE FROPA...DRY AIR THROUGH A DEEP LAYER SHOULD FILTER IN
BEHIND THE FRONT...AND VFR CONDITIONS WITH NNELY WINDS UNDER 10KT
SHOULD PREVAIL FOR THE REMAINDER OF THE DAY TOMORROW.
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH THE EARLY
OVERNIGHT HOURS.
* MEDIUM TO HIGH CONFIDENCE IN AT LEAST WIDELY SCATTERED TSRA
INVOF THE TERMINALS EARLY THURSDAY MORNING.
* MEDIUM CONFIDENCE IN PRE-FRONTAL SHRA.
* MEDIUM TO HIGH CONFIDENCE IN TIMING FRONTAL WIND SHIFT AND WIND
TRENDS FOLLOWING THE FROPA..
* LOW CONFIDENCE IN MVFR CIGS/VIS BEHIND THE FRONT EARLY THURSDAY.
KREIN
//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...
THURSDAY NIGHT THROUGH MONDAY...VFR.
TUESDAY...SLT CHC TSRA.
BMD
&&
.MARINE...
202 PM CDT
A COLD FRONT EXTENDED FROM NORTHERN QUEBEC SW ACROSS E LAKE
SUPERIOR...N WI AND S MN AT MID AFTERNOON. THIS COLD FRONT WILL
CONTINUE TO MOVE SE...REACHING N LAKE MI THIS EVENING AND S LAKE
MI THU MORNING....SHIFTING WINDS TO OUT OF THE NW AND N. AS THE
COLD FRONT MOVES OFF TO THE SE DURING THU HIGH PRESSURE WILL MOVE
ESE TO ONTARIO AND THE UPPER MIDWEST. THE HIGH THEN GRADUALLY
SHIFTS SE AND WILL BE OVER QUEBEC...THE GREAT LAKES AND THE OH
VALLEY BY SAT MORNING AND THE MID ATLANTIC SEABOARD AND S
APPALACHIANS BY MON MORNING.
HEIGHT OUTPUT BY LOCALLY RUN WAVE MODEL WOULD APPEAR TO BE LOW
GIVEN MODERATELY STRONG N WINDS THOUGH LOCAL OUTPUT IN LINE WITH
GLERL PRODUCED WAVE HEIGHTS. HOWEVER...WAVE GROWTH WILL BE
LIMITED AS THE AIR MASS BEHIND THE COLD FRONT IS STILL WARM
ENOUGH FOR A TEMPERATURE INVERSION AT THE LAKE SURFACE WHICH WILL
LIMIT MOMENTUM TRANSFER ALL THE WAY DOWN TO THE AIR/WATER
INTERFACE.
TRS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1235 PM CDT WED AUG 21 2013
.DISCUSSION...
625 AM CDT
HAVE UPDATED THE FORECAST EARLY THIS MORNING TO ACCOUNT FOR MORE
MORNING AND EARLY AFTERNOON CLOUD COVER. WHAT IS LEFT OF A SHEARED
OUT SHORT WAVE ON WATER VAPOR CENTERED ACROSS WI IS HELPING TO
CAUSE ENOUGH ASCENT AND FOCUS FOR 5000-8000 FT CLOUDS ACROSS
NORTHERN IL AND WI. THE RAP 750-850MB CAPTURES THE RH DEPICTION
PRETTY WELL...AND THE SPC WRF COLUMN CONDENSATE DOES TOO ALTHOUGH
A BIT LATE WITH IT. BOTH SHOW INDICATIONS OF THE CLOUDS STICKING
AROUND INTO THIS AFTERNOON AND WITH THE SLOW MOVEMENT OF THE
SHEARED WAVE THAT SEEMS MORE PLAUSIBLE THAN EARLIER. SO HAVE
BUMPED UP SKY COVER QUITE A BIT AND EASED THE TEMPERATURE CLIMB
ALONG WITH BUMPING DOWN HIGHS 2-4 DEGREES IN THE NORTHERN HALF OF
THE AREA. ITS POSSIBLE MORE MAY NEED TO BE PEELED AWAY IF CLOUDS
ARE THICK ENOUGH. CONFIDENCE IS NOT THAT HIGH ON HOW THICK THE
CLOUDS WILL REMAIN AS RAP DIAGNOSTIC SOUNDINGS INDICATE THE RH TO
BE FAIRLY SHALLOW. EVEN IF SCATTERED AT TIMES THOUGH IT LIKELY
WILL SLOW THE TEMPERATURE JUMP...SO FELT ENOUGH CONFIDENCE TO
LOWER THEM SOME.
MTF
//PREV DISCUSSION...
328 AM CDT
THE FORECAST FOCUS WAS FIRST ON THE CHANCES FOR STORMS TONIGHT AND
MAINLY EARLY THU...WHICH EVEN THOUGH THE COVERAGE IS NOT EXPECTED
TO BE PARTICULARLY HIGH THIS IS THE BEST CHANCE FOR RAIN IN OVER A
WEEK. THEN ATTENTION TURNED TO TEMPERATURES WITH LIKELY 90 TODAY
IN MANY COMMUNITIES...THEN A SHORT TERM COOL DOWN FOLLOWED BY AN
APPRECIABLE WARM UP INTO THE FINAL WEEK OF METEOROLOGICAL SUMMER
/ALREADY???/.
TODAY...WHAT HAS BEEN A STAGNANT BUT VERY PLEASANT PATTERN OVER
THE REGION IS BEGINNING TO SHOW SOME SHIFTING EARLY THIS
MORNING...WITH WATER VAPOR SHOWING A STRONG 110 KT+ JET ACROSS FAR
SOUTHERN CANADA BUCKLING SLIGHTLY INTO THE UPPER MIDWEST. MULTIPLE
SHORT WAVES ARE NOTED ACROSS THE NORTHERN ROCKIES AND UPPER
MIDWEST ON THE LEADING EDGE OF THE IMPINGING UPPER TROUGH. AREA
SOUNDINGS LAST EVENING AND VARIOUS SATELLITE CHANNELS CONTINUE TO
INDICATE A FAIRLY DRY MID LEVEL AIR MASS OVER OUR AREA WHICH WILL
TAKE TIME TO SATURATE...SO NOT EXPECTING BLOWOFF FROM ANY MORNING
CONVECTION TO THE NORTHWEST TO REALLY SPREAD OVER WITH ONLY SOME
CUMULUS THROUGH EARLY AFTERNOON. THE THERMAL RIDGE AT 850-925MB IN
ADVANCE OF THE TROUGH LEANS ESE TODAY OVER THE AREA AND THESE
VALUES DO SUPPORT 90 ABOUT A QUARTER OF THE TIME BASED ON LOCAL
CLIMATOLOGY. GIVEN LOCAL HIGHS YESTERDAY AT 87-88 IN MOST
PLACES...UPSTREAM HIGHS IN CENTRAL IA WERE AT 90...AND WITH OUR
DRYING GROUND OFFERING SENSIBLE HEAT TO BE A BIGGER
FACTOR...BELIEVE 88 TO 92 SHOULD PREVAIL ACROSS MUCH OF THE AREA.
DEW POINTS FAVORED IN THE MID TO UPPER 60S WILL ALLOW FOR HEAT
INDEX READINGS TO INCH INTO THE MID 90S IN A SOME COMMUNITIES.
TONIGHT INTO THU MORNING...AS PRIMARY HEIGHT FALLS DEVELOP EAST
ACROSS ONTARIO...THE DEVELOPING SURFACE LOW WILL TRACK EAST UP
THERE...WITH A WEAK SECONDARY LOW /1011MB OR SO/ FAVORED IN
GUIDANCE TO MOVE ALONG THE FRONT FROM IA TO CENTRAL LAKE MI
TONIGHT. THIS FEATURE ALONG WITH THE UPPER TO MID JET TURNING MORE
NORTHWEST GIVING THE FRONT A GOOD PUSH SOUTHWARD ACROSS THE AREA
ON THU. SOME GUIDANCE INDICATES CONVECTION INTO THE AREA THIS
EVE...BUT THAT JUST SEEMS TO QUICK GIVEN THE DRY RH AND LIMITED
MOISTURE TRANSPORT IN ADVANCE OF THE SYSTEM. THE FOCUS OF THE
BOUNDARY CONVERGENCE WILL BE IN WI LATE AFTERNOON AND EVE WITH
SCATTERED POSSIBLY STRONG CONVECTION EXPECTED THERE. GIVEN HIGH
INSTABILITY AND ASSOCIATED DCAPE VALUES UPSTREAM A FEW CLUSTERS
MAY MAKE QUICK PROGRESS SE BY MID TO LATE EVE INTO
OVERNIGHT...ESPECIALLY IF OVER THE LAKE. BUT AGAIN COVERAGE LOOKS
SCATTERED. THIS SYSTEM HAS THE MAKINGS OF A LATE SUMMER FRONT BY
OVERNIGHT WITH WEAKENING SURFACE PRESSURES ALONG IT IN THE WAKE OF
THE AFOREMENTIONED LOW...WEAKENING WARM AIR ADVECTION/DIFFERENTIAL
TEMPERATURE ADVECTION IN ADVANCE OF IT...AND AGAIN LIMITED
MOISTURE. THE DEEP LAYER SHEAR ALSO IS MARGINAL WITH VECTORS
ORIENTED POORLY FOR ANY MCS TYPE ORGANIZATION. OVERALL THE MODEL
SUITE SUPPORTS LIMITED AREAL COVERAGE OF QPF GREATER THAN 0.25 IN.
SO KEEP MAINLY CHANCE POPS EVERYWHERE TONIGHT WITH ONLY MINOR
TWEAKS TO WHAT WAS IN THERE...AND MAINTAIN THE HIGHEST OVERNIGHT.
REST OF THU AND FRI....DRY AIR AND SUPPRESSION MOVE QUICKLY
SOUTHWARD BEHIND THE SURFACE COOL FRONT...WHICH LOOKS TO MOVE
DOWN THE LAKE AND THROUGH CHICAGO SOMETIME IN THE MID-MORNING.
THIS MAY CONTINUE TO SUPPORT SCATTERED SHOWERS AND SOME STORMS
ALONG IT...SO MAINTAIN POPS ESPECIALLY FOR THE SOUTHERN CWA
THROUGH THE DAY. THE PATTERN SUPPORTS TEMPS LIKELY FALLING ALONG
THE LAKE SHORE BY LATE MORNING INTO EARLY AFTERNOON AND REACHING
THEIR PEAK IN OUTLYING AREAS EARLY IN THE AFTERNOON AND THEN
HOLDING STEADY. DRIER AIR REALLY WORKS ITS WAY IN WITHIN THE LOW-
LEVELS THU NIGHT. WITH MOSTLY SUNNY CONDITIONS FRI THIS SHOULD
SUPPORT GOOD MIXING OUT WITH RELATIVE HUMIDITY EXPECTED TO DROP TO
AROUND 30 PERCENT FRI AFTERNOON...AN EARLY SIGN THAT THE NEXT
SEASON IS INDEED NOT FAR AWAY. WITH 850MB TEMPERATURES IN THE MID
TEENS...TEMPS ON FRI LOOK TO BE IN THE MID 70S TO LOWER 80S. FRI
NIGHT SHOULD BE THE COOLEST WITH HIGH PRESSURE STILL PRIMARILY
INFLUENCING THE AREA AND LITTLE CIRRUS EXPECTED. WHILE DEW POINTS
IN THE 40S ARE LIKELY DURING FRI AFTERNOON...THESE SHOULD COME
BACK INTO THE EVE AND LOWS RIGHT NOW LOOK TO BOTTOM OUT IN THE
LOWER TO MID 50S IN MOST OUTLYING LOCATIONS.
BEYOND...THE UPPER RIDGE LOOKS TO BUILD BACK NORTHEAST AS THE
WEEKEND PROGRESSES AND INTO NEXT WEEK...SUPPORTING WARMING
TEMPS AS WELL AS LIKELY PRECIP-FREE CONDITIONS WITH THE FOCUS OF
SYSTEMS AGAIN SHIFTING NORTHWARD. WHILE 90 DEGREES OR WARMER LOOKS
POSSIBLE ON MULTIPLE DAYS WITH MID TO UPPER 60S DEW POINTS...THE
SIGNAL IS STRONGEST ON MON AND TUE WITH THEN SOME BUCKLING DUE TO
POSSIBLE SHORT WAVES/UPSTREAM STORMS. HAVE BLENDED BIAS-
CORRECTED DATA FROM MODELS INTO THE GOING FORECAST WHICH SUPPORTS
WARMER TEMPS THAN A STRAIGHT MODEL BLEND.
MTF
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* CHANCE OF SHRA/TSRA EARLY THURSDAY MORNING AND WIND SHIFT
ASSOCIATED WITH A COLD FRONT PASSAGE.
* CHANCE OF MVFR CIGS THURSDAY MORNING FOR A SHORT PERIOD BEHIND
COLD FRONT.
KREIN
//DISCUSSION...UPDATED 18Z...
CONDITIONS WILL REMAIN QUIET ACROSS THE REGION UNDER SWLY FLOW
AHEAD OF AN APPROACHING COLD FRONT. THE PRIMARY CONCERN FOR THE
PERIOD CONTINUES TO BE THE CHANCES FOR SHOWERS AND THUNDERSTORMS
EARLY TOMORROW MORNING. THE MAIN CHANGE TO THE GOING FORECAST IS
TO INTRODUCE A VCSH GROUP AS MUCH OF THE SHORT RANGE MODEL
GUIDANCE IS INDICATING A CHANCE FOR PRE-FRONTAL PCPN TO MOVE INTO
NRN IL BY ARND 06Z. THERE ARE STILL SOME CONCERNS AS TO THE
COVERAGE OF THE PRE-FRONTAL PCPN...HENCE THE VCSH RATHER THAN A
PREVAILING GROUP WHICH WOULD IMPLY GREATER CONFIDENCE IN MORE
EXTENSIVE COVERAGE. STILL EXPECTING THE FRONTAL PASSAGE AT RFD BY
ARND 12Z AND THE CHICAGO AREA SHORTLY THEREAFTER AS THE SYSTEM
SHOULD BE FAIRLY PROGRESSIVE. WINDS WILL VEER THROUGH NWLY TO
EVENTUALLY NNELY FOLLOWING THE FROPA. THERE IS STILL A CONCERN FOR
A BRIEF PERIOD OF MVFR CIGS OR VIS FOLLOWING THE FROPA AS SOME OF
THE GUIDANCE IS INDICATED A NEARLY SATURATED LAYER BLW
3KFT...THOUGH WOULD ANTICIPATE THAT RFD/DPA WOULD CLIMATOLOGICALLY
HAVE A GREATER CHANCE FOR REDUCED VISBY THAN ORD/MDW. WITHIN A FEW
HOURS OF THE FROPA...DRY AIR THROUGH A DEEP LAYER SHOULD FILTER IN
BEHIND THE FRONT...AND VFR CONDITIONS WITH NNELY WINDS UNDER 10KT
SHOULD PREVAIL FOR THE REMAINDER OF THE DAY TOMORROW.
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH THE EARLY
OVERNIGHT HOURS.
* MEDIUM TO HIGH CONFIDENCE IN AT LEAST WIDELY SCATTERED TSRA
INVOF THE TERMINALS EARLY THURSDAY MORNING.
* MEDIUM CONFIDENCE IN PRE-FRONTAL SHRA.
* MEDIUM TO HIGH CONFIDENCE IN TIMING FRONTAL WIND SHIFT AND WIND
TRENDS FOLLOWING THE FROPA..
* LOW CONFIDENCE IN MVFR CIGS/VIS BEHIND THE FRONT EARLY THURSDAY.
KREIN
//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...
THURSDAY NIGHT THROUGH MONDAY...VFR.
TUESDAY...SLT CHC TSRA.
BMD
&&
.MARINE...
237 AM CDT
SOUTHWEST WINDS TO AROUND 25 KT WILL CONTINUE THROUGH THE DAY TODAY
ACROSS NORTHERN LAKE MICHIGAN AHEAD OF AN APPROACHING COLD FRONT
WHICH CURRENTLY STRETCHES FROM SOUTHERN MANITOBA INTO THE DAKOTAS.
WINDS WILL BE A LITTLE WEAKER ON THE SOUTH END OF THE LAKE WHERE THE
GRADIENT ISNT QUITE AS TIGHT. STABLE CONDITIONS ARE EXPECTED OVER
THE LAKE WHICH WILL HELP KEEP HIGHER END GUSTS IN CHECK...THOUGH
WOULDNT BE SURPRISED TO SEE SHIPS REPORT OCCASIONAL GUSTS TO 30
KTS. WINDS TURN NORTHERLY LATE TONIGHT AND EARLY THURSDAY...WITH
GUSTS AROUND 25 KT MAINTAINING ACROSS THE SOUTH HALF OF THE LAKE.
WINDS BEGIN TO TAPER THURSDAY EVENING AS HIGH PRESSURE BUILDS
ACROSS THE WESTERN LAKES REGION. WINDS WILL TURN SOUTHERLY AGAIN
SATURDAY AS ANOTHER LOW PRESSURE SYSTEM MOVES ACROSS THE CANADIAN
PRAIRIES...AND FRESHEN UP ESPECIALLY ON SUNDAY WHEN WE MAY ONCE
AGAIN BE LOOKING AT 20 TO 25 KT WINDS.
BMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
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FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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AREA FORECAST DISCUSSION..CORRECTED
NWS QUAD CITIES IA IL
318 PM CDT WED AUG 21 2013
.SYNOPSIS...
ISSUED AT 314 PM CDT WED AUG 21 2013
12Z UA ANALYSIS HAS AN 850MB TROF RUNNING FROM WESTERN LAKE SUPERIOR
INTO WYOMING. AHEAD OF THIS TROF 850MB DEW POINTS WERE IN THE MID
TEENS FROM UPPER MICHIGAN INTO EASTERN NEBRASKA. SATELLITE/RADAR
TRENDS THROUGH MID AFTERNOON SHOW VERY LITTLE IN THE WAY OF DIURNAL
CLOUDS ACROSS THE AREA BUT CONVECTION HAS FIRED ALONG THE COLD FRONT
FROM NEAR KFSD INTO WESTERN WISCONSIN.
18Z SFC ANALYSIS HAS A WEAK LOW NEAR KFSD. THE FRONT RAN NORTHEAST
FROM THE LOW INTO WESTERN UPPER MICHIGAN. AROUND THE FRONTAL
BOUNDARY DEW POINTS WERE IN THE LOW 70S WITH 60S ACROSS THE
REMAINDER OF THE MIDWEST.
&&
.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 314 PM CDT WED AUG 21 2013
THE CONVECTION THAT HAS DEVELOPED THIS AFTERNOON IS IN AN AREA OF
STEEP 850-700MB LAPSE RATES AND IN THE SLIGHTLY BETTER
FORCING/CONVERGENCE ASSOCIATED WITH THE FRONTAL ZONE. THE RAP TRENDS
KEEP MORE STABLE AIR ACROSS THE IMMEDIATE AREA THROUGH LATE
AFTERNOON SO ANY CONVECTION APPROACHING THE AREA WILL DISSIPATE.
THE MCS AND LIFT TOOLS SUGGEST ISOLATED TO POSSIBLY SCATTERED
CONVECTION ENTERING THE HWY 20 CORRIDOR DURING THE EARLY EVENING. BY
MID TO LATE EVENING NEW CONVECTION SHOULD DEVELOP AND BECOME LOOSELY
ORGANIZED FROM HWY 30 ON NORTH. BOUNDARIES FROM THIS CONVECTION
SHOULD ALLOW ISOLATED SHOWERS AND STORMS TO DEVELOP ALONG AND SOUTH
OF I-80 AFTER MIDNIGHT.
ON THURSDAY...LINGERING NOCTURNAL CONVECTION SHOULD BE OVER THE AREA
AS THE FRONT CONTINUES TO SLOWLY MOVE SOUTH THROUGH THE AREA.
DIFFERENTIAL HEATING WILL THEN ALLOW NEW CONVECTION TO DEVELOP
DURING THE LATE MORNING AND AFTERNOON HOURS. AS THE NEXT CANADIAN
HIGH BUILDS INTO THE GREAT LAKES...THE DRIER AIR WILL SLOWLY FORCE
THE CONVECTION SOUTH THURSDAY AFTERNOON WITH IT ONLY OVER THE
SOUTHWEST THIRD OF THE CWFA BY THURSDAY EVENING. ..08..
.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 314 PM CDT WED AUG 21 2013
AN UPPER RIDGE OVER THE WESTERN STATES IS PROGGED TO BUILD EAST AND
STRENGTHEN THROUGH THE MIDDLE OF NEXT WEEK...PROLONGING THE DRY
CONDITIONS AND BRINGING LATE SUMMER HEAT TO THE REGION.
ABOUT THE ONLY CHANCE OF RAIN WILL BE THE POTENTIAL FOR SOME
LINGERING SHRA/TSRA OVER THE SOUTHWEST THURSDAY NIGHT NEAR A
DECAYING FRONT OVER MISSOURI. FORCING WILL NOT BE VERY STRONG GIVEN
THE WEAK FLOW NEAR THE FRONTAL ZONE AND WITH THE UPPER RIDGE
BUILDING INTO THE REGION...POPS WERE KEPT IN THE SLIGHT CHANCE
CATEGORY.
THE UPPER RIDGE CONTINUES TO BUILD INTO THE REGION WITH A
594DM-PLUS H5 HIGH CENTERED OVER MO BY SUNDAY NIGHT AND REMAINING
IN PLACE THROUGH THE MIDDLE OF THE WEEK. THE STRONGER MID LEVEL
FLOW WILL BE DIVERTED AROUND THE RIDGE WHICH WILL KEEP THE BETTER
FORCING WELL NORTH OF THE AREA. THE GFS AND 12Z ECMWF SHOW SOME QPF
OVER THE AREA BY NEXT WEDNESDAY OR WEDNESDAY NIGHT ASSOCIATED WITH
A SHORT WAVE AND FRONT MOVING THE THROUGH THE WESTERN GREAT LAKES
AND MISSISSIPPI VALLEY. HOWEVER KEPT POPS OUT OF THE FORECAST FOR
NOW WITH MID LEVEL TEMPS PROGGED TO BE AROUND 12C SUGGESTING THESE
FEATURES WILL BE FIGHTING A CAP.
SUMMERTIME HEAT WILL BE RETURNING TO THE REGION AS H8 TEMPS WARM
INTO THE LOW 20/S BY SUNDAY AND REMAIN THERE THROUGH MID WEEK. THE
BLENDED GUIDANCE WAS WARMING HIGH TEMPERATURES TO AROUND 90 BUT
MIXING DOWN H8 TEMPS EARLY NEXT WEEK YIELDED HIGHS IN THE LOW TO MID
90S. FORECAST HIGHS WERE SKEWED TOWARD THE TEMPS DERIVED FROM MIXING
WHICH SEEM MORE REASONABLE. WITH THESE WARMER TEMPERATURES...AND
DEWPOINTS EXPECTED TO BE NEAR 70...WE WILL PROBABLY SEE HEAT INDICES
CLOSE TO 100 DURING THE HEAT OF THE DAY. AT THIS TIME IT DOESN/T
APPEAR THAT WE WILL BE CLOSE TO ANY RECORD HIGHS...AT LEAST THROUGH
THE 28TH. RECORDS DURING THIS TIME ARE NEAR OR ABOVE 100 AT THE
CLIMATE SITES.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1246 PM CDT WED AUG 21 2013
VFR WX IS EXPECTED THROUGH 03Z/22. AFT 03Z/22 THE POTENTIAL EXISTS
FOR TSRA TO MOVE INTO EASTERN IOWA/NORTHERN ILLINOIS ASSOCIATED
WITH A COLD FRONT. IF A TSRA AFFECTS A TAF SITE A BRIEF PERIOD OF
MVFR/IFR CONDITIONS WILL BE POSSIBLE. AFT 06Z/22 MVFR VSBYS ARE
EXPECTED TO DEVELOP AND LAST THROUGH SUNRISE. THE MODELS ARE
SUGGESTING THE POSSIBILITY OF AN ORGANIZED TSRA COMPLEX AFFECTING
EASTERN IOWA AND NORTHERN ILLINOIS THROUGH 18Z/22. ..08..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
SYNOPSIS...08
SHORT TERM...08
LONG TERM...DLF
AVIATION...08
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
1259 PM CDT WED AUG 21 2013
.UPDATE...
ISSUED AT 1246 PM CDT WED AUG 21 2013
CONVECTION ACROSS NORTHERN IOWA IS MAINLY CONFINED TO AN AREA OF
STEEP LAPSE RATES IN THE 850-700MB LAYER. RAP TRENDS KEEP THESE
STEEP LAPSE RATES TO THE NORTH/NORTHWEST OF THE CWFA THROUGH LATE
AFTERNOON. THUS CONVECTION APPROACHING THE CWFA WILL DISSIPATE OR
QUICKLY FALL APART OVER THE NORTHWEST QUARTER OF THE CWFA.
RAP TRENDS ON FCST SOUNDINGS SHOW THERMALS SHOULD BEGIN SOON WITH
CONVECTIVE TEMPERATURES ACHIEVED AROUND MID TO LATE AFTERNOON.
TRENDS FROM THE MCS AND LIFT TOOLS WITH THE RAP MODEL SUGGEST THE
POSSIBILITY OF SOME WEAK CONVECTION ENTERING THE HWY 20 CORRIDOR
VERY LATE AFTERNOON/EARLY EVENING. THE MORE ORGANIZED CONVECTION
SHOULD BE NORTH/NORTHEAST OF THE CWFA. BY MID TO LATE EVENING
OUTFLOW BOUNDARIES FROM THIS CONVECTION MAY HELP INITIATE NEW
CONVECTION OVER THE NORTHERN THIRD OF THE CWFA. ..08..
UPDATE ISSUED AT 947 AM CDT WED AUG 21 2013
WEAK ISOLATED SHOWERS CONTINUE TO PERSIST AT MID MORNING. THE
SHOWERS BETWEEN KCID AND KDBQ ARE RAPIDLY DISSIPATING WITH NEW
ISOLATED SHOWERS BETWEEN KMLI AND KOTM.
THE RAP MODEL HAS A SUBTLE VORT MAX MOVING THROUGH EASTERN IOWA
WHICH APPEARS TO BE RESPONSIBLE FOR THE ISOLATED SHOWERS. IF THE
RAP TRENDS ARE CORRECT...THESE NEW SHOWERS WILL DISSIPATE WITHIN
THE NEXT SEVERAL HOURS AS THE VORT MAX EXITS THE CWFA AND DOWNWARD
MOTION TAKES OVER.
THE QUESTION THEN BECOMES WHEN WILL NEW CONVECTION DEVELOP. THE
MCS AND LIFT TOOLS SUGGEST NORTH OF THE CWFA BY LATE AFTERNOON
ALONG THE FRONT. THERE ARE DIFFERENCES BETWEEN THE VARIOUS MODEL
SOLUTIONS AS TO WHEN PRECIPITATION WILL ARRIVE IN THE CWFA. THE
OVERALL FORCING REMAINS WEAK AND FCST SOUNDINGS SUGGEST A CAP
REMAINING IN PLACE THROUGH THE DAY. PRECIPITATION MAY HOLD OFF
UNTIL AFTER SUNSET.
WHAT LLJ IS PRESENT IS EXTREMELY WEAK AND GENERALLY WELL WEST OF
THE CWFA. THE CHANCES FOR PRECIPITATION ARE NOT OVERLY GOOD BUT
WILL MAINTAIN THE CURRENT POPS FOR TONIGHT. ..08..
&&
.SYNOPSIS...
ISSUED AT 331 AM CDT WED AUG 21 2013
WARM AIR IS FINALLY IN TOTAL CONTROL OVER THE ENTIRE CWA EARLY
TODAY...WITH TEMPERATURES HOVERING AROUND 70...WITH DEW POINTS IN THE
MID 60S. A COLD FRONT IS MOVING SLOWLY SOUTHEAST THROUGH THE
DAKOTA...SPARKING A FEW AREAS OF SHOWERS AND THUNDERSTORMS. THE AREA
LOCATED IN SOUTH DAKOTA IS ASSOCIATED WITH A WEAK SHORT WAVE THAT
SHOULD INITIATE STORMS CLOSE TO OUR CWA THIS EVENING.
&&
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 331 AM CDT WED AUG 21 2013
FOR THE FIRST TIME IN WEEKS...THERE IS A REASONABLE CHANCE FOR RAIN
TONIGHT. HOWEVER...WITH WEAK DYNAMICS...AND LESS THAN OPTIMAL
FRONTAL TIMING...THERE REMAINS LOW CONFIDENCE ON A
MATURE...BENEFICIAL RAIN PRODUCING MCS. WHILE THIS IS
POSSIBLE...ESPECIALLY IN THE NORTH 1/2...SIGNALS INDICATING A MATURE
MCS ARE JUST NOT COMING TOGETHER IN A CONFIDENT PICTURE. INFLOW AT
850MB TONIGHT APPEARS WEAK..AND LACKING FOCUSED CONVERGENCE. WHILE
MUCAPE VALUES WILL SUPPORT THUNDER...WE WILL LIKELY NEED A
CONVECTIVE OUTFLOW FROM THE NORTH TO RESULT IN WIDESPREAD
CONVECTION. THIS IS TOO MANY IFS TO RESULT IN A LIKELY COVERAGE
FORECAST ISSUANCE...AND I AM LEFT WITH A RANGE OF CHANCE POPS FROM
20 SOUTH TO 50 NORTH TO BEST DESCRIBE THE EVENT POTENTIAL OVERNIGHT.
RAINFALL WHERE IT OCCURS...COULD BE 0.2 TO 0.5...BUT WIDESPREAD
TOTALS MAY NOT EXCEED 0.1 SHOULD MESOSCALE PROCESSES NOT COME
TOGETHER.
TEMPERATURES AND HUMIDITY WILL BOTH BE QUITE HIGH TODAY...WITH
UPSTREAM TRAJECTORIES AND MIX DOWN IN MODELS SUGGESTING UPPER 80S TO
VERY LOW 90S SHOULD BE WIDESPREAD FOR HIGHS TODAY. TONIGHT...UPPER
60S NORTH TO AROUND 70 SOUTH APPEARS MOST LIKELY FOR LOWS...UNLESS
AN ORGANIZED COLD POOL CAN PUSH RAIN COOLED TEMPERATURES TO THE MID
60S.
ERVIN
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 331 AM CDT WED AUG 21 2013
FOCUS IN THE LONG TERM IS WITH WALKING OUT PCPN CHANCES THU/THU
NIGHT AS FRONT CONTINUES TO MOVE SOUTHWARD THROUGH THE AREA AND
DRIER AIR INTRUDES FROM THE NORTH. LOW CHANCE POPS /26-30/
ARE EXPECTED AS THE FRONT SAGS SOUTHWARD INTO MO AND CENTRAL IL
DURING THE DAY THU. LINGERING SLIGHT CHANCES ARE IN THE SOUTH FOR
THU NIGHT. SURFACE HIGH PRESSURE WILL NUDGE INTO THE AREA FRIDAY
BEFORE QUICKLY MOVING OFF TO THE NE. THEN AN UPPER LEVEL RIDGE OF
HIGH PRESSURE IS EXPECTED TO BUILD INTO THE MID MS RIVER VALLEY
REGION ON ITS HEELS. FRIDAY AND BEYOND...DRY CONDITIONS ARE
ANTICIPATED WITH A WARMING TREND...AS A HEAT WAVE COMMENCES SUN...
LASTING THROUGH TUE. HIGHS THU-SAT WILL BE IN THE 80S /POSSIBLY SOME
UPPER 70S NORTH FRI/...WHILE HIGHS SUN-TUE RISE INTO THE UPPER 80S
AND LOWER 90S...WITH HEAT INDICES IN THE 90S.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1246 PM CDT WED AUG 21 2013
VFR WX IS EXPECTED THROUGH 03Z/22. AFT 03Z/22 THE POTENTIAL EXISTS
FOR TSRA TO MOVE INTO EASTERN IOWA/NORTHERN ILLINOIS ASSOCIATED
WITH A COLD FRONT. IF A TSRA AFFECTS A TAF SITE A BRIEF PERIOD OF
MVFR/IFR CONDITIONS WILL BE POSSIBLE. AFT 06Z/22 MVFR VSBYS ARE
EXPECTED TO DEVELOP AND LAST THROUGH SUNRISE. THE MODELS ARE
SUGGESTING THE POSSIBILITY OF AN ORGANIZED TSRA COMPLEX AFFECTING
EASTERN IOWA AND NORTHERN ILLINOIS THROUGH 18Z/22. ..08..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
UPDATE...08
SYNOPSIS...ERVIN
SHORT TERM...ERVIN
LONG TERM...14
AVIATION...08
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
254 PM EDT WED AUG 21 2013
.SYNOPSIS...
AFTER A FRONT MOVES THROUGH THURSDAY NIGHT...EXPECT SUNNY SKIES
AND DRY WEATHER FROM FRIDAY THROUGH MONDAY.
&&
.NEAR TERM /THROUGH THURSDAY/...
UPPER TROUGH AXIS IS CURRENTLY OVER WESTERN OHIO AND IS MOVING TO
THE EAST. AS A RESULT...SCATTERED SHOWERS AND THUNDERSTORMS HAVE
DEVELOPED ACROSS MUCH OF SOUTHERN OHIO...EASTERN KENTUCKY...AND
CENTRAL WEST VIRGINIA. HIGH RESOLUTION MODELS SHOW THE BULK OF THIS
ACTIVITY REMAINING TO THE SOUTH OF INTERSTATE 70...CONSIDERING THE
16Z RUN OF THE RAP MODEL KEEPS MOST OF THE UPPER LEVEL ENERGY TO THE
SOUTH OF THE MASON-DIXON LINE. HAVE GONE WITH LIKELY SHOWERS AND
CHANCE THUNDERSTORMS ACROSS THE WV/MD RIDGES DURING THE EVENING
HOURS...THEN THINK COVERAGE WILL MARKEDLY DECREASE AFTER
MIDNIGHT...DUE TO BOTH THE LOSS OF CONVECTIVE HEATING AND THE TROUGH
AXIS BEING ALIGNED NEAR THE NORTHERN WEST VIRGINIA PANHANDLE. WITH
THE RETURN OF WIDESPREAD CLOUD COVER...LOWS SHOULD REMAIN WARMER
THAN LAST NIGHT...IN THE 60S IN ALL LOCATIONS.
BIGGEST CHANGE IN THE FORECAST IS THE TIMING OF THE APPROACHING
FRONT. MESOSCALE AND HIGH-RESOLUTION MODELS HAVE ALL QUICKENED THE
TIMING OF THE FRONT...WITH THE BULK OF THE RAINFALL NOW COMING
DURING THE AFTERNOON. THIS WILL ALLOW FOR GREATER HEATING AND
THEREFORE INSTABILITY. NAM AND GFS SHOW MODEST AMOUNTS OF
INSTABILITY...BUT KEEP EFFECTIVE SHEAR UNDER 30 KTS. THINK THAT
THERE COULD BE AN ISOLATED STRONG/SEVERE THUNDERSTORM...BUT THAT
THE LACK OF STRONG SHEAR SHOULD KEEP THE CHANCES FOR WIDESPREAD
SEVERE TO BE LIMITED. WITH CLOUD COVER REMAINING THROUGHOUT THE
REGION...HIGH TEMPERATURES SHOULD BE NEAR NORMAL OR A COUPLE
DEGREES COOLER.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
WITH THE STRONGEST DYNAMICS WITH THE FRONT REMAINING WELL TO THE
NORTH AND EAST...HAVE CONTINUED THE IDEA OF THE PREVIOUS FORECAST
THAT KEPT POPS ONLY AT HIGH CHANCE AS OPPOSED TO LIKELY TO THE
SOUTH OF THE INTERSTATE 70 CORRIDOR. POPS WILL DIMINISH DURING
OVERNIGHT...AND HAVE KEPT A TOKEN SLIGHT CHANCE THUNDERSTORM
MENTION IN AFTER MIDNIGHT. WITH THE FASTER FRONTAL
PASSAGE...KEEPING SLIGHT CHANCE POPS FRIDAY MORNING AS FAR NORTH
AS ZANESVILLE...WHEELING...AND INDIANA IS LIKELY A BIT
OVERDONE...BUT DO NOT WANT TO COMPLETELY THROW OUT THE ECMWF
SOLUTION...WHICH KEEPS POPS THROUGH MUCH OF THE DAY. MUCH DRIER
AIR MOVING IN BEHIND THE FRONT SHOULD KEEP SKIES MOSTLY SUNNY ON
FRIDAY. HARD TO EVEN CALL THE FRONT A COLD FRONT...CONSIDERING
HIGHS WILL ONLY DROP 2-3 DEGREES FROM THE DAY BEFORE. BY FRIDAY
NIGHT HIGH PRESSURE SHOULD ESTABLISH ITSELF ACROSS THE GREAT
LAKES...ALLOWING FOR CLEAR SKIES AND LIGHT NORTHERLY FLOW. THIS
WILL DROP TEMPERATURES ABOUT 10 DEGREES BELOW NORMAL FRIDAY
NIGHT...AND A COUPLE DEGREES BELOW NORMAL SATURDAY.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
A LARGE UPPER LEVEL RIDGE WILL BUILD OVER THE CENTRAL CONUS
THROUGH MUCH OF THE PERIOD. MOST OF THE MODELS SUGGEST THAT WE
WILL REMAIN ON THE EASTERN PERIPHERY OF THIS RIDGE IN NORTHWEST
FLOW WHICH COULD...BY MIDWEEK...BRING THE CHANCE FOR SHOWERS AND
THUNDERSTORMS AS UPPER LEVEL DISTURBANCES DROP SOUTH OVER THE
GREAT LAKES. FOR NOW...WITH MODEL TIMING DIFFERENCES...KEPT POP
CHANCES LOW. TEMPERATURES WERE KEPT NEAR OR JUST ABOVE SEASONAL
AVERAGES.
&&
.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
GENERAL VFR IS EXPECTED THROUGH THIS EVENING. AN APPROACHING
UPPER LEVEL LOW WILL BRING THE CHANCE FOR SOME SHOWERS ACROSS
POINTS SOUTH OF PIT TOWARD EVENING...BUT WITH COVERAGE EXPECTED TO
BE SCATTERED...NO MENTION IN THE TAFS. ONCE AGAIN PATCHY MVFR FOG
CAN BE EXPECTED LATER TONIGHT TOWARD DAYBREAK THURSDAY.
ON THURSDAY UPPER TROUGH WILL MOVE ACROSS REGION WITH A TRAILING
COLD FRONT. CONFIDENCE NOT HIGH ENOUGH TO INCLUDE MORE THAN VCTS
MIDDAY NORTH REACHING KPIT EARLY AFTERNOON.
SOUTHERLY WIND AT TIMES MAINLY UNDER 5 KTS BEFORE WINDS BECOME
LIGHT WEST BEHIND FROPA THURSDAY AFTERNOON.
.OUTLOOK.../THURSDAY NIGHT THROUGH MONDAY/...
RESTRICTIONS POSSIBLE THURSDAY NIGHT SOUTH OF KPIT AS FRONT MAY
FIRE IN THE EVENING. OTHERWISE HIGH PRESSURE WILL BEGIN TO BUILD
IN FRIDAY AND DOMINATE INTO MONDAY WITH GENERAL VFR.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
341 PM EDT WED AUG 21 2013
.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 340 PM EDT WED AUG 21 2013
MAIN FOCUS OF THE FORECAST FOR TODAY IS THE DEVELOPING THUNDERSTORMS
ASSOCIATED WITH A COLD FRONT JUST STARTING TO MOVE INTO WESTERN
UPPER MICHIGAN. THE COLD FRONT HAS BEEN MAKING IT/S WAY
ACROSS WESTERN LAKE SUPERIOR AND NORTHWEST WISCONSIN OVER THE
LAST FEW HOURS AND THERE WAS SOME CONCERN THAT THE STRATUS DECK
THAT DEVELOPED FROM THE FOG NEAR DULUTH WOULD LIMIT COME OF THE
CONVECTION. BUT THE FORCING FROM THE COLD FRONT COMBINED WITH
DIURNAL HEATING HAS BEGAN TO PRODUCE THUNDERSTORMS ALONG THE COLD
FRONT WITH SOME BECOMING FAIRLY STRONG AT THIS WRITTING. WITH A
VERY UNSTABLE ATMOSPHERE (MLCAPE VALUES ANALYZED FROM 2000-3000
J/KG DUE TO SFC DEWPOINTS IN THE UPPER 60S AND LOWER 70S)...THEY
SHOULDN/T HAVE MUCH DIFFICULTY CONTINUING THROUGH THE EARLY EVENING.
AS HAS BEEN MENTIONED OVER THE LAST COUPLE OF DAYS...0-6KM SHEAR
VALUES ARE A LITTLE MARGINAL...BUT LATEST RAP TRENDS SHOW VALUES
APPROACHING 30-35KTS RIGHT ALONG THE COLD FRONT. THIS SHOULD HELP
THE THUNDERSTORMS BECOME A LITTLE MORE TILTED AND BETTER ORGANIZED
OVER THE NEXT FEW HOURS. THINKING THAT THERE IS A DECENT CHANCE OF
THIS CONVECTION BECOMING LINEAR AND MOVING ACROSS MUCH OF UPPER
MICHIGAN LATE THIS AFTERNOON AND INTO THE EVENING. DAMAGING WIND IS
A DECENT THREAT WITH DCAPE VALUES AHEAD OF THE FRONT OF 800-1100
J/KG. WHERE THERE ARE STRONGER STORMS...HAIL IS ALSO A THREAT...BUT
IT WILL LIKELY BE MORE ISOLATED DUE TO THE HIGHER FREEZING LEVELS.
WITH THE BOUNDARIES OVER THE WEST AND LOWER LCL HEIGHTS FROM THE
LEFT OVER STRATUS...THERE COULD BE A ISOLATED TORNADO THREAT...BUT
SHOULD BE CONFINED TO THE LATE AFTERNOON. IN ADDITION...ANOTHER
BOUNDARY (AIDED BY EARLIER CLOUDS/SHOWERS THAT MOVED ACROSS NORTHERN
LAKE SUPERIOR) HAS SETUP FROM WEST TO EAST FROM ONTONAGON THROUGH
MARQUETTE COUNTY. SHOWERS/THUNDERSTORMS HAVE ALSO STARTED TO DEVELOP
ALONG THIS AND ARE SLIDING EAST. SPC HAS JUST ISSUED A SEVERE
THUNDERSTORM WATCH FOR MUCH OF UPPER MICHIGAN THROUGH 4Z. THE COLD
FRONT AND THUNDERSTORMS ARE EXPECTED TO EXIT INTO LAKE MICHIGAN
AROUND 06Z. PREVIOUS FORECAST HAD A GOOD HANDLE ON TIMING...SO ONLY
MADE MINOR ADJUSTMENTS.
THE REST OF THE NIGHT SHOULD BE DRY (DUE TO DRIER AIR SURGING IN
BEHIND THE COLD FRONT)...EVENTHOUGH A FAIRLY POTENT SHORTWAVE WILL
BE SLIDING SOUTHEAST ACROSS THE AREA FROM LAKE WINNIPEG. THIS
SHOULD LEAD TO MOSTLY CLEAR SKIES AND MUCH COOLER TEMPERATURES THAN
LAST NIGHT.
COOLER NORTHERLY FLOW WILL BE IN STORE FOR UPPER MICHIGAN ON
THURSDAY...AS HIGH PRESSURE APPROACHES THE AREA FROM THE UPPER
MISSISSIPPI VALLEY. 850MB TEMPS WILL BE AROUND 10C COOLER THAN
TODAY AND EXPECT A SIMILAR RESPONSE WITH THE HIGHS (IN THE 70S).
COOLEST TEMPERATURES WILL BE NEAR LAKE SUPERIOR...WHERE THE
NORTHERLY WINDS OFF THE LAKE WILL KEEP TEMPS RIGHT AROUND 70. A
SUNNY TO MOSTLY SUNNY SKY IS EXPECTED.
.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 340 PM EDT WED AUG 21 2013
NAM SHOWS A 500 MB RIDGE ACROSS THE ROCKIES AND CENTRAL PLAINS WITH
A TROUGH OVER THE ERN U.S. 00Z FRI. THE 500 MB RIDGE BUILDS INTO THE
CENTRAL PLAINS THIS FORECAST PERIOD WITH THE EDGE OF THE WESTERLIES
OVER THE AREA THIS FORECAST PERIOD. DID PUT IN SLIGHT CHANCE TO
CHANCE POPS IN THE FORECAST FOR THE WEST HALF FOR SAT AFTERNOON AS A
WARM FRONT HEADS TOWARDS THE AREA AND MOISTURE STARTS TO INCREASE.
OTHERWISE...DID NOT MAKE TOO MANY CHANGES TO THE GOING FORECAST FOR
TEMPERATURES. LOOKS TO STAY WARM THROUGH THIS PERIOD.
IN THE EXTENDED...GFS AND ECMWF SHOW A 500 MB RIDGE OVER THE CENTRAL
U.S. SAT NIGHT INTO SUN. THE RIDGE REMAINS STATIONARY THROUGH THE
PERIOD WITH THE U.P. IN THE PERIPHERY OF THE RIDGE IN THE RING OF
FIRE SCENARIO WHERE ANY SHORTWAVE CAN SET OFF A ROUND OF
THUNDERSTORMS. WILL BE HARD TO TIME THESE SHORTWAVES AND EASIEST WAY
TO FORECAST THIS WOULD BE TO BROADBRUSH THIS FORECAST PERIOD WITH
CHANCE POPS EVEN THOUGH IT WILL NOT BE A TOTAL WASHOUT. TEMPERATURES
WILL STAY ABOVE NORMAL FOR THIS FORECAST PERIOD ALONG WITH
INCREASING HUMIDITY. ONLY PERIOD THAT LOOKS DRY IS WED WITH A FRONT
MOVING OUT OF THE AREA.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 146 PM EDT WED AUG 21 2013
VERY TRICKY AVIATION FORECAST FOR KIWD/KSAW THIS AFTERNOON DUE TO
SOME UNCERTAINTY ON TIMING/LOCATION OF THE CONVECTION THIS
AFTERNOON/EVENING. A COLD FRONT CURRENTLY APPROACHING WESTERN UPPER
MICHIGAN AND POTENTIALLY THROUGH KCMX WILL BRING A POTENTIAL FOR
SHOWERS AND THUNDERSTORMS. BUT HAVE SOME CONCERN THAT THE MVFR DECK
NOW MOVING INTO KIWD WILL LIMIT COVERAGE SOME. THE LAST HOUR HAS
SEEN SOME INCREASE IN CU AND SHOWERS WITHIN THE AREA OF
STRATUS...SO OPTED TO LEAVE IN A TS/VCTS MENTION FOR A PERIOD THIS
AFTERNOON AT KIWD. ONCE THE FRONT MOVES THROUGH AROUND
21-22Z...THUNDER POTENTIAL SHOULD END ALONG WITH THE MVFR CEILINGS.
AS THE SHOWERS/THUNDERSTORMS DEVELOP OVER WESTERN UPPER MICHIGAN
THIS AFTERNOON...MAIN QUESTION FOR KSAW IS IF THEY WILL DEVELOP FAR
ENOUGH NORTH TO INFLUENCE THE SITE. THINKING THEY WILL WITH THE CU
FIELD GOING UP FROM THE CITY OF ONTONAGON TO BARAGA AND THE EASTWARD
MOVEMENT WOULD SLIDE IT THROUGH KSAW AFTER 21Z.
BEHIND THE FRONT TONIGHT INTO THURSDAY...VFR CONDITIONS WILL
PREVAIL AS HIGH PRESSURE BUILDS OVER THE AREA. THERE MAY BE A BRIEF
PERIOD OF SCT100 CLOUDS MOVING IN FROM NORTHWEST MN...BUT WILL NOT
EFFECT OPERATIONS.
&&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 340 PM EDT WED AUG 21 2013
A COLD FRONT CURRENTLY MOVING ACROSS CENTRAL LAKE SUPERIOR WILL
CONTINUE SOUTHEAST THIS EVENING AND LEAD TO NORTHERLY FLOW
(GENERALLY BELOW 15KTS) OVER THE LAKE FOR THE REST OF TONIGHT AND
INTO THURSDAY EVENING. HIGH PRESSURE THAT IS PRODUCING THE LIGHTER
WINDS WILL THEN SHIFT SOUTHEAST INTO THE LOWER GREAT LAKES AND
ALLOW WINDS TO SLOWLY INCREASE FROM THE SOUTH-SOUTHWEST FRIDAY INTO
THE WEEKEND. AT THIS POINT...WOULD EXPECT LAKE STABILITY FACTORS TO
KEEP WINDS AT OR BELOW 20KTS.
ONE FINAL ITEM TO MENTION IS IF THE SHOWERS/THUNDERSTORMS AFFECT
ENOUGH OF EASTERN LAKE SUPERIOR TO DEVELOP FOG. LEFT OUT AT THIS
POINT SINCE VISIBLE SATELLITE INDICATED THE FOG OVER NORTHERN LAKE
SUPERIOR HAS DISSIPATED AND THERE IS SOME UNCERTAINTY ON HOW FAR
THE RAIN WILL GET INTO EASTERN LAKE SUPERIOR.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...SRF
LONG TERM...07
AVIATION...SRF
MARINE...SRF
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
339 PM EDT WED AUG 21 2013
.SHORT TERM...TONIGHT
VIS SATELLITE AND RADAR SHOW VERY SMALL AREAS OF SHOWERS ALONG AN
AREA OF MOISTURE CONVERGENCE FROM JYM TO PTK. THIS WAS DEPICTED WELL
WITH THE HRRR AS A DIURNAL CONVECTIVE SHOWER EVENT THAT WILL SWING
EAST AND SOUTH...DYING WITH THE LOSS OF DAYTIME HEATING. 20-30 POP
GRIDS WERE UPDATED EARLIER TO INCLUDE THIS CHANCE...WHICH WILL END
NLT 00Z.
CLOUDS AND PRECIP CHANCES INCREASE FROM NW TO SE TONIGHT AS A COLD
FRONT APPROACHES FROM THE NORTHWEST. THERE WILL BE SOME ELEVATED
INSTABILITY...ESPECIALLY NORTH OF I-69 OVERNIGHT AS LI/S ARE -2 OR
-3 AND ABOUT 1000 J/KG OF CAPE IS PRESENT ABOVE 800 MB. WINDS WILL
ALSO VEER AND INCREASE WITH HEIGHT IN THE ELEVATED LAYER
OVERNIGHT...LEADING TO HIGHER POPS TO INCLUDE THUNDER IN THE
FORECAST. THESE CONDITIONS WILL SWING SOUTHEASTWARD THROUGH THE
STATE...BUT HIGHER PW/S (2.0 INCHES) AND LESS INSTABILITY BRING THE
FORECAST TO LOWER THUNDER CHANCES SOUTH OF M-59.
&&
.LONG TERM...THURSDAY THROUGH TUESDAY
A WELL-DEFINED 110KT JET IS EVIDENT ALONG THE US/CANADA BORDER THIS
AFTERNOON AS THE UPPER GRADIENT TIGHTENS BETWEEN THE EXPANSIVE
WESTERN U.S. RIDGE AND SHORTWAVE ENERGY DIGGING INTO SOUTHEAST
SASKATCHEWAN AND SOUTHWEST MANITOBA. MESOANALYSIS REVEALS AN
ORGANIZING LOW-LEVEL BAROCLINIC ZONE ASSOCIATED WITH THIS JET THAT
IS BEGINNING TO FEEL ITS WAY SOUTHEAST AS THE LARGE SCALE TROUGH
OVER CENTRAL AND EASTERN CANADA BEGINS TO SWEEP ACROSS THE GREAT
LAKES. RELATIVELY LITTLE HAS CHANGED WITH REGARD TO FORECAST
REASONING. INITIALLY, SOME REMNANT SHOWERS WILL BE POSSIBLE IN
ADVANCE OF THE FRONT IN ASSOCIATION WITH ANY UPSTREAM DEVELOPMENT
OVER WISCONSIN THIS EVENING, ALTHOUGH CONFIDENCE IS NOT PARTICULARLY
HIGH IN THE DEGREE OF COVERAGE EARLY IN THE PERIOD GIVEN THE LACK OF
LARGE SCALE SUPPORT. STILL, EITHER WEAKLY ORGANIZED RIGHT ENTRANCE
SUPPORT, A CONVECTIVELY ENHANCED WAVE EMANATING OUT OF UPSTREAM
ACTIVITY, OR A COMBINATION OF BOTH, STILL WARRANT A CONTINUATION OF
LIKELY POPS ACROSS MUCH OF THE AREA DURING THE FIRST HALF OF THE
DAY.
UNCERTAINTY FURTHER INCREASES FOR THURSDAY AFTERNOON AS BOUNDARY
LAYER RECOVERY WILL BE STRONGLY DEPENDENT ON CLOUD COVER AND
DURATION OF MORNING SHOWERS. THE NAM/GFS REPRESENT THE AGGRESSIVE
SIDE OF THE ENVELOPE WITH UP TO 3000 J/KG SBCAPE DEVELOPING BY MID
AFTERNOON WHEREAS THE GENERAL CONSENSUS OF BOTH HIGHER RESOLUTION
GUIDANCE SUCH AS THE NMM/ARW AS WELL AS THE GEM/ECMWF ALLOW HIGH
PRESSURE TO AGGRESSIVELY BUILD IN WITH LITTLE MORE THAN A LOW
COVERAGE OF AFTERNOON SHOWERS TO SHOW FOR THE FROPA. GIVEN THE
DEGREE OF UNCERTAINTY, FELT IT PRUDENT TO TAPER POPS BACK INTO THE
HIGH CHANCE CATEGORY ESSENTIALLY EVERYWHERE ALONG/NORTH OF I-94,
WHICH REFLECTS THE LATEST FORECAST REASONING BUT STILL LEAVES ROOM
FOR ADJUSTMENT IN EITHER DIRECTION AS NEW DATA BECOMES AVAILABLE.
FOR FAR SOUTHERN AREAS, ENOUGH RECOVERY WILL BE POSSIBLE TO SUPPORT
A PULSE SEVERE THREAT IMMEDIATELY AHEAD OF THE FRONT, BUT WITH THE
BETTER SHEAR LAGGING BEHIND, THE THREAT FOR ORGANIZED SEVERE WEATHER
REMAINS LOW. TEMPERATURES WILL FALL BACK TO NEAR 80 FOR THE WEEKEND
AS COOLER AND DRIER AIR FILTERS INTO SOUTHEAST MI IN THE WAKE OF THE
FRONT AND HIGH PRESSURE SETTLES OVER THE NORTHEASTERN UNITED STATES.
THERE WILL BE NUMEROUS CHANCES FOR THUNDERSTORMS NEXT WEEK AS THE
CWA WILL BE POSITIONED ALONG THE NE PERIPHERY OF THE BUILDING 595DM
RIDGE OVER THE CENTRAL U.S. WHILE REMAINING IN CLOSE PROXIMITY TO
PREVAILING WESTERLY FLOW. THIS WILL SET THE STAGE FOR MULTIPLE
CONVECTIVE COMPLEXES TO AFFECT SOME OR ALL OF THE REGION. INITIAL
EXPECTATIONS ARE THEREFORE FOR THUNDERSTORM ACTIVITY IN THE VICINITY
TO HELP KEEP TEMPERATURES IN CHECK, BUT WITH H5 HEIGHTS IN THE
585-588DM RANGE AND H85 TEMPS NEAR 20C, THE POTENTIAL FOR HIGHS TO
REACH INTO THE 90S WILL EXIST ON BASICALLY ANY DAY FROM MONDAY
ONWARD.
&&
.MARINE...
A PRESSURE GRADIENT BETWEEN HIGH PRESSURE IN THE MID-ATLANTIC AND
LOW PRESSURE OVER HUDSON BAY WILL PROVIDE INCREASED SW WINDS
TONIGHT. AIR TEMPERATURES WILL STAY PRETTY WARM UNTIL THE COLD FRONT
SWINGS THROUGH EARLY THURSDAY...SO THERE IS NOT MUCH INSTABILITY
OVER THE LAKES UNTIL THEN. OFFSHORE WINDS WILL BECOME MORE ONSHORE
LATE THURSDAY AND WILL HELP INCREASE WAVE HEIGHTS ALONG THE THUMB`S
SHORE TO 3 FEET. WILL WATCH FOR SMALLCRAFT CONDITIONS NEXT FORECAST
PERIOD...BUT IN THE MEANTIME SIG/MAX WAVES SHOULD STAY MANAGEABLE.
&&
.AVIATION...ISSUED 121 PM EDT WED AUG 21 2013
//DISCUSSION...
DIURNAL CU FIELD HAS ENCOMPASSED THE REGION INTO A BLANKET OF VFR
CLOUDS THIS AFTERNOON. THIS WILL GIVE WAY TO MVFR CONDITIONS AS A
COLD FRONT APPROACHES FROM THE NW OVERNIGHT. CIGS APPEAR TO
GENERALLY BE AROUND 5KFT...BUT VSBYS WILL LIKELY DROP TO MVFR WITHIN
RA AND TSRA THAT DEVELOP NEAR THE PRE-FRONTAL TROUGH AND AHEAD OF
THE COLD FRONT. WINDS SHIFT TO THE NORTH THURS WITH PLENTY OF DRY
AIR RETURNING THINGS TO VFR AFTER THE RAIN.
FOR DTW...BEST THUNDERSTORM CHARACTERISTICS APPEAR TO BE FURTHER
NORTH...SO LEFT TS OUT OF THE TAFS THIS PERIOD. WILL UPDATE WITH AMD
IF NEEDED...BUT DTW WILL LIKELY DROP TO 4SM WITH STRONGEST SHOWERS.
//DTW THRESHOLD THREATS...
* MEDIUM CONFIDENCE OF CEILINGS BELOW 5000 FEET AFTER 12Z TONIGHT.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
SHORT TERM...MM
LONG TERM....JVC
MARINE.......MM
AVIATION.....MM
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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
147 PM EDT WED AUG 21 2013
.UPDATE...
ISSUED AT 1029 AM EDT WED AUG 21 2013
JUST A QUICK UPDATE FOR THE EXPECTATIONS FOR THIS AFTERNOON AND
EARLY EVENING BASED OFF LATEST HIGHER RESOLUTION MODEL RUNS AND
NEWLY ARRIVING 12Z RUNS. OVERALL...FEEL THAT THE EXPECTATIONS OVER
THE LAST COUPLE OF DAYS STILL SEEM VALID. AT THE PRESENT
TIME...COLD FRONT IS STRETCHING SOUTHWEST FROM JUST NORTH OF LAKE
SUPERIOR THROUGH THE MN ARROWHEAD AND INTO WEST CENTRAL MN.
ISOLATED SHOWERS AND THUNDERSTORMS CONTINUE TO DEVELOP ALONG THE
FRONT BUT THEN DECAY AS THEY SLIDE AHEAD OF IT. VERY SHARP CONTRAST
IN DEWPOINTS AHEAD (UPPER 60S AND LOWER 70S) OF THE FRONT AND MID
50S BEHIND. THIS FRONT WILL BE THE FOCUS FOR CONVECTION EARLY-MID
AFTERNOON (18-20Z) AS IT MOVES INTO THE WESTERN U.P. AND THEN STORM
MOTIONS AND FRONT MOVING THE THUNDERSTORMS EAST-SOUTHEAST. SEVERE
WEATHER PARAMETERS LOOK TO BE SIMILAR AS MENTIONED IN THE SHORT TERM
DISCUSSION. AM FAIRLY CONFIDENT ON THUNDERSTORM OCCURRENCE...BUT
SEVERE THREAT IS A LITTLE UNCERTAIN...LARGELY DUE TO THE LIMITED
EFFECTIVE AND 0-6KM BULK SHEAR OF 25-30KT. THIS MAY LIMIT SOME OF THE
TILTING/ORGANIZATION OF THE THUNDERSTORMS. LATEST RAP RUN HAS PUSHED
VALUES UP A LITTLE MORE (TOWARDS 35KTS)...ALONG WITH 09Z SREF
PROBABILITIES...WHICH WITH THE PUSH/FORCING OF THE COLD FRONT LEADS
TO A LITTLE HIGHER CONFIDENCE OF SOME ORGANIZATION AND SEVERE THREAT.
WITH THE SLIGHT INCREASE IN SHEAR...OPTED TO ADD DAMAGING WINDS TO
THE WEATHER GRIDS ALONG WITH SMALL HAIL.
&&
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 250 AM EDT WED AUG 21 2013
CURRENTLY /MIDNIGHT EARLY WED/...THE CWA IS BETWEEN A SFC HIGH OVER
THE ERN SEABOARD AND A SFC TROUGH/COLD FRONT FROM HUDSON BAY TO NW
MN TO SD AND CO. ALOFT...THE CWA IS UNDER THE INFLUENCE OF ZONAL
FLOW OVER CANADA AND THE NRN CONUS...WITH AN UPPER TROUGH NW OF THE
SFC TROUGH.
THE SFC TROUGH/COLD FRONT WILL MOVE ACROSS THE CWA TODAY INTO EARLY
TONIGHT...AND MODELS ARE IN PRETTY GOOD AGREEMENT ON THE TIMING OF
THE FRONT SO TIMING OF POPS WILL BE PRETTY EASY. THE SW/NE ORIENTED
FRONT WILL MOVE TO WRN UPPER MI AROUND 18Z WED...THEN TO ERN LAKE
SUPERIOR AND CENTRAL UPPER MI BY 00Z THU...THEN JUST E OF THE CWA BY
06Z THU. WITH 850MB TEMPS AROUND 20C ALONG AND AHEAD OF THE
FRONT...THOSE AREAS THAT DO NOT EXPERIENCE MUCH CLOUD COVER AND
PRECIP BY PEAK HEATING /MAINLY CENTRAL AND ERN UPPER MI/ WILL SEE
HIGH TEMPS AROUND 90F WED...WITH THE EXCEPTION BEING LOCATIONS N/NE
OF LAKE SUPERIOR DUE TO SW WINDS. OTHERWISE...EXPECT HIGHS IN THE
80S OVER WRN UPPER MI WHERE CLOUDS/PRECIP WILL MOVE IN EARLIER IN
THE DAY WITH THE FRONT. SBCAPES OF 2000-3500 J/KG SHOULD RESULT IN
THE WARM SECTOR...BUT 0-6KM WIND SHEAR IS ONLY 20-30KTS AND ALMOST
COMPLETELY UNIDIRECTIONAL. DCAPE VALUES AROUND 1000 J/KG ARE
POSSIBLE...HIGHEST OVER SCENTRAL UPPER MI. WITH ALL THIS IN
MIND...WIND SHEAR LOOKS TO BE THE LIMITING FACTOR FOR SEVERE
STORMS...BUT WITH THE CAPE AND DCAPE SO HIGH...EXPECT ISOLATED TO
SCATTERED SEVERE STORMS IN PRIMARILY MULTICELL STORM CLUSTER/S WITH
A LIMITED POSSIBILITY OF SUPERCELL THUNDERSTORMS /ESPECIALLY ALONG
LAKE BREEZE BOUNDARIES/. GREATEST THREAT STILL LOOKS LIKE DAMAGING
WINDS...WITH ONLY AN ISOLATED SEVERE HAIL THREAT DUE TO THE FREEZING
LEVEL BEING AROUND 12KFT.
CONVECTION SHOULD EXIT E/SE BY AROUND 06Z-09Z THU...WITH SFC HIGH
PRESSURE QUICKLY FILLING IN BEHIND THE TROUGH. THIS WILL RESULT IN
SOME LOCATIONS OVER WRN UPPER MI BEING ABLE TO FALL TO AROUND 50F
FOR LOWS LATE WED NIGHT.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 250 AM EDT WED AUG 21 2013
MAIN FCST CONCERNS IN THE LONGER TERM ARE TEMPS ON THU/FRI WITH DRY
HI PRES DOMINATING. FOCUS FOR THE WEEKEND INTO EARLY NEXT WEEK ALSO
INCLUDES SHRA/TS CHCS AS A MORE ACTIVE SUMMER-LIKE PATTERN EVOLVES
OVER THE UPR LKS ON THE SRN EDGE OF ZONAL FLOW IN SRN CANADA AND N
OF STRONG RDG IN THE CONUS.
THU...ARRIVAL OF VIGOROUS DNVA/DEEP LYR QVECTOR DVGC UNDER CONFLUENT
UPR FLOW/MUCH DRIER AIR WITH PWAT FCST ARND 0.5 INCH /OR 50 PCT OF
NORMAL/ IN THE WAKE OF SHRTWV PASSAGE EARLY IN THE DAY WL BRING
MOSUNNY WX TO THE CWA ON THU. THE DAY WL ALSO BE MUCH COOLER DESPITE
BRIGHT SUNSHINE WITH H85 TEMPS PROGGED TO BE WITHIN A DEGREE OR 2 OF
10C.
THU NGT...ALTHOUGH SOME OF THE MODELS SHOW ANOTHER SHRTWV DROPPING
SEWD THRU THE GRT LKS IN THE NW FLOW ALF...THIS DISTURBANCE WL HAVE
LTL IMPACT DUE TO THE DRYNESS OF THE AIRMASS AND LARGER SCALE ACYC
FLOW ASSOCIATED WITH SFC HI CENTERED OVER THE AREA. THERE COULD BE
SOME PATCHY CLDS OVER MANLY THE NE HALF OF THE CWA CLOSER TO THE
TRACK OF THIS FEATURE...BUT OVERALL LGT WINDS/PWAT STILL 0.50-0.75
INCH WL ALLOW FOR A HEALTHY DIURNAL TEMP FALL WELL INTO THE 40S AT
THE COOLER INTERIOR LOCATIONS.
FRI...AS THE UPR RDG AXIS SHIFTS E INTO THE WRN GRT LKS AND DEEP LYR
QVECTOR DVGC/DRY AIR DOMINATE...EXPECT MOSUNNY SKIES. THE DAY SHOULD
ALSO TURN A BIT WARMER WITH LARGE SCALE SUBSIDENCE/RETURN SLY FLOW
ON THE WRN FLANK OF SFC HI PRES SHIFTING OVER LOWER MI LIFTING H85
TEMPS UP NEAR 15C OVER THE W BY 00Z SAT. LK BREEZES THAT DVLP NEAR
LK MI AND LK SUP E OF THE KEWEENAW UNDER THE WEAKER PRES GRADIENT
CLOSER TO THE DEPARTING SFC HI PRES WL ALLOW FOR SOME COOLING NEAR
THE LK SHORES IN THOSE AREAS.
FRI NGT...STRENGTHENING SSW WIND ON THE WRN FLANK OF SLOWLY
DEPARTING SFC HI PRES WL LIMIT NOCTURNAL COOLING...ESPECIALLY NEAR
LK SUP OVER THE W HALF WHERE THE STRONGER S WIND UNDER SHARPEST PRES
GRADIENT WL DOWNSLOPE AND SOME HI CLDS SPILLING OVER THE SLOWLY
APRCHG UPR RDG AXIS WL ARRIVE THRU THE NGT. EXPECT THE COOLEST
OVERNGT LO TEMPS ACROSS THE INTERIOR CENTRAL AND E.
THIS WEEKEND...UPR RDG IN THE PLAINS IS PROGGED TO BUILD INTO THE
UPR LKS IN WAD PATTERN/SSW FLOW BTWN HI PRES DRIFTING INTO THE MID
ATLANTIC STATES AND LOWER PRES IN CENTRAL CANADA. A NUMBER OF THE
EXTENDED MODELS SHOW H85 TEMPS NEARING 20C AND PWAT REACHING 1.50 TO
1.75 INCHES BY SUN...SO THE WX WL TURN WARMER AND MORE HUMID.
WHETHER SHRTWVS RIDING THRU THE ZONAL FLOW ON THE TOP OF THIS UPR
RDG WL INTERACT WITH THE INCRSGLY UNSTABLE AIRMASS AND GENERATE
SHRA/TS IS A SGNFT FCST CONCERN. SUSPECT THE BEST SHOT AT SHRA/TS WL
BE SAT NGT/SUN FOLLOWING DEPARTURE OF DRY AIRMASS AND OVER THE NRN
TIER CLOSER TO THE SHRTWVS TRACKING THRU ONTARIO AND LOWER HGTS.
EXTENDED...THE CWA IS FCST TO REMAIN NEAR THE SRN FLANK OF ZONAL
FLOW OVER SRN CANADA AND ON TOP OF UPR RDG DOMINATING THE CONUS.
THIS SUMMER-LIKE PATTERN WITH RECENT ECMWF/GFS RUNS SHOWING H85
TEMPS NEAR 20C IN VCNTY OF A STNRY FNT IS ONE THAT FAVORS EPISODES
OF SHRA WITH HEAVY RA/PERHAPS SVR TSRA ACCOMPANYING THE PASSAGE OF
SHRTWVS THRU THE UPR LKS/ONTARIO NEAR EDGE OF CAPPING INVRN
ASSOCIATED WITH THE STRONG RDG TO THE S. SPECIFYING THE DAY-TO-DAY
DETAILS IN THIS PATTERN IS IMPOSSIBLE ATTM...SO WL STICK TO THE
CONSENSUS FCST. THE CURRENT CPC DAY 3-7 OUTLOOK DOES INDICATE A
THREAT OF HEAVY RA FOR UPR MI OVER THE WEEKEND AND INTO EARLY NEXT
WEEK. TEMPS WL BE ABV NORMAL.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 146 PM EDT WED AUG 21 2013
VERY TRICKY AVIATION FORECAST FOR KIWD/KSAW THIS AFTERNOON DUE TO
SOME UNCERTAINTY ON TIMING/LOCATION OF THE CONVECTION THIS
AFTERNOON/EVENING. A COLD FRONT CURRENTLY APPROACHING WESTERN UPPER
MICHIGAN AND POTENTIALLY THROUGH KCMX WILL BRING A POTENTIAL FOR
SHOWERS AND THUNDERSTORMS. BUT HAVE SOME CONCERN THAT THE MVFR DECK
NOW MOVING INTO KIWD WILL LIMIT COVERAGE SOME. THE LAST HOUR HAS
SEEN SOME INCREASE IN CU AND SHOWERS WITHIN THE AREA OF
STRATUS...SO OPTED TO LEAVE IN A TS/VCTS MENTION FOR A PERIOD THIS
AFTERNOON AT KIWD. ONCE THE FRONT MOVES THROUGH AROUND
21-22Z...THUNDER POTENTIAL SHOULD END ALONG WITH THE MVFR CEILINGS.
AS THE SHOWERS/THUNDERSTORMS DEVELOP OVER WESTERN UPPER MICHIGAN
THIS AFTERNOON...MAIN QUESTION FOR KSAW IS IF THEY WILL DEVELOP FAR
ENOUGH NORTH TO INFLUENCE THE SITE. THINKING THEY WILL WITH THE CU
FIELD GOING UP FROM THE CITY OF ONTONAGON TO BARAGA AND THE EASTWARD
MOVEMENT WOULD SLIDE IT THROUGH KSAW AFTER 21Z.
BEHIND THE FRONT TONIGHT INTO THURSDAY...VFR CONDITIONS WILL
PREVAIL AS HIGH PRESSURE BUILDS OVER THE AREA. THERE MAY BE A BRIEF
PERIOD OF SCT100 CLOUDS MOVING IN FROM NORTHWEST MN...BUT WILL NOT
EFFECT OPERATIONS.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 250 AM EDT WED AUG 21 2013
OVERALL...EXPECT STRONGEST WINDS /TO AROUND 20KTS/ OVER THE NEXT FEW
DAYS TO BE EARLY THIS MORNING INTO TODAY AS THE PRESSURE GRADIENT
TIGHTENS UP AHEAD OF A COLD FRONT THAT WILL MOVE THROUGH LATE THIS
MORNING INTO THIS EVENING...BUT HIGH OVERWATER STABILITY WITH INFLUX
OF A VERY WARM AIRMASS WILL LIMIT THE INCREASE OF WIND SPEED NEAR
THE COOLER LAKE SURFACE. THE ARRIVAL OF MORE HUMID AIR MAY RESULT IN
SOME FOG FORMATION OVER THE COOLER LAKE WATERS...BUT RESTRICTED THE
FOG FORECAST TO AREAS WHERE SOME SHOWERS OR THUNDERSTORMS ARE
EXPECTED. ANY FOG WILL DISSIPATE THIS AFTERNOON AND EVENING
FOLLOWING A COLD FRONTAL PASSAGE AND THE ARRIVAL OF DRIER AIR.
ANOTHER PERIOD OF STRONGER WINDS /FROM THE SW/ MAY OCCUR ON
SATURDAY NIGHT INTO SUNDAY AS LAKE SUPERIOR SITS BETWEEN A HIGH
PRESSURE SYSTEM TO THE SE AND A TROUGH OF LOW PRESSURE TO THE NW...
BUT HIGH OVERWATER STABILITY WILL REMAIN A LIMITING FACTOR ON HOW
STRONG THE NEAR SURFACE WINDS WILL BECOME.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
UPDATE...SRF
SHORT TERM...TITUS
LONG TERM...KC
AVIATION...SRF
MARINE...TITUS
AREA FORECAST DISCUSSION
NWS GAYLORD MI
123 PM EDT WED AUG 21 2013
.SYNOPSIS...
ISSUED AT 407 AM EDT WED AUG 21 2013
ANOTHER WARM AND MORE HUMID AFTERNOON IS EXPECTED ACROSS NORTHERN
MICHIGAN TODAY...WITH HIGH TEMPERATURES EXPECTED TO RANGE FROM 10
TO 15 DEGREES ABOVE MID AUGUST NORMALS. A COLD FRONT DROPPING IN
FROM THE NORTHWEST WILL BRING THE THREAT FOR THUNDERSTORMS TO
NORTHERN MICHIGAN...MAINLY FROM LATE THIS AFTERNOON INTO TONIGHT.
COOLER AND LESS HUMID CONDITIONS ARE EXPECTED THURSDAY...AS
PRECIPITATION EXITS THE REGION DURING THE MORNING HOURS.
&&
.UPDATE...
ISSUED AT 123 PM EDT WED AUG 21 2013
STILL NOT A WHOLE LOT GOING ON ACROSS THE REGION...JUST SOME
PASSING MID CLOUDS WITH A WEAK WAVE UP AROUND 700MB CROSSING THE
AREA...ACTING ON AN AREA OF ENHANCED MID LEVEL LAPSE RATES TO HELP
BUBBLE UP SOME ACCAS. DID SEE A COUPLE OF LIGHT SHOWERS FIRE
ACROSS LAKE MICHIGAN...WITH A FEW SURVIVING THE TRIP INLAND THE
PAST FEW HOURS...BUT ISOLATED AT BEST. THAT MAY CONTINUE AS THAT
WAVE AND CORE OF BETTER LAPSE RATES SLIPS INTO NORTHEAST LOWER
THROUGH THE AFTERNOON...BUT THE BIGGER ISSUE WILL BE WHAT HAPPENS
UPSTREAM INTO WISCONSIN AND EASTERN MINNESOTA THE NEXT FEW HOURS.
AIRMASS OUT THAT WAY IS STEADILY DESTABILIZING...WITH A NICE AXIS
OF NEAR 70F DEW POINTS POOLING AHEAD OF A COLD FRONT SLIDING
THROUGH WESTERN LAKE SUPERIOR. CURRENT SBCAPE VALUES UP AROUND
3500 J/KG ARE IMPRESSIVE...TIED TO AN AXIS OF QUITE STEEP
700-500MB LAPSE RATES IN THE PREFRONTAL ENVIRONMENT. DEEPER SHEAR
HASN`T QUITE CAUGHT UP TO THOSE AREAS...BUT IT`S ON ITS WAY WITH A
STRONGER WAVE DIVING INTO SOUTHERN MANITOBA AND A CORE OF BETTER
50 KNOT MID LEVEL FLOW ON ITS SOUTHERN FRINGE.
SO THE REST OF THE AFTERNOON SHOULD REMAIN QUIET AROUND THESE
PARTS...SAVE FOR MAYBE A FEW MORE SHOWERS. BUT DO EXPECT TO SEE
CONVECTION UNZIP AHEAD OF THE FRONTAL BOUNDARY FROM THE WESTERN
U.P. TO NORTHEAST IOWA (SOME HINTS OF THIS ALREADY). WILL BE
CLOSELY FOLLOWING THE EVOLUTION OF THAT ACTIVITY AS IT OCCURS...AS
IT WILL HAVE A MAJOR IMPACT ON OUR CHANCES TONIGHT. HRRR HAS BEEN
INSISTENT ON THE BEST CHANCES WORKING FROM NORTHERN WISCONSIN DOWN
THROUGH OUR SOUTHWEST CWA...AND FORECAST STORM PROPAGATION VECTORS
DO FAVOR THAT TYPE OF EVOLUTION. STILL NOT SO SURE ABOUT GOING
LIKELY POPS...EVEN AT THIS RANGE...BUT WILL LOOK AT A FEW MORE
THINGS BEFORE MAKING ANY WHOLESALE CHANGES. IN THE MEANTIME...
ENJOY THE WARMTH!
UPDATE ISSUED AT 959 AM EDT WED AUG 21 2013
A LITTLE BIT OF A NEBULOUS FORECAST PROBLEM WITH REGARD TO CLOUDS
AND A FEW SHOWERS THE NEXT FEW HOURS. FIRST VISIBLE PICS OF THE
DAY SHOW A RATHER EXPANSIVE ELEVATED CU/ACCAS DECK SPREADING UP
THE LAKE MICHIGAN SPINE...TIED TO AN ENHANCED LOWER LEVEL MOISTURE
AXIS (OBVIOUSLY) BUT WITHIN A PLUME OF STEEPER 850-600MB LAPSE
RATES CLEARLY EVIDENT ON THE 12Z GRB RAOB. AIRMASS FARTHER EAST IS
MUCH LESS UNSTABLE...WITH LOTS OF SUNSHINE WELL UNDERWAY AT THE
MOMENT. HAVE SEEN FEW SHOWERS BUBBLE UP UNDER THE ACCAS DECK...AND
SUSPECT THIS TREND WILL CONTINUE FOR A FEW MORE HOURS AS LOCALIZED
ACCELERATION OF THE LOW LEVEL JET REMAINS ACROSS LAKE MICHIGAN.
NOT TOO KEEN ON THIS ACTIVITY SPREADING TOO FAR EAST...AND THE
SAME WITH CLOUDS...AS SAID STEEPER LAPSE RATES ONLY SLOWLY MIGRATE
EASTWARD THROUGH 18Z PER SHORT TERM GUIDANCE TRENDS. AS
SUCH...WILL CONFINE A SMALL 20 POP/ISOLATED WORDING CLOSER TO THE
STRAITS AND INTO PARTS OF EASTERN UPPER...BUT WITH THIS ACTIVITY
LIKELY TO WANE WITH TIME AS THE BETTER JET FORCING ALSO DECREASES.
OTHERWISE...WILL BE WATCHING THE EVOLUTION OF CONVECTIVE DEBRIS
CROSSING THE WESTERN U.P. THE NEXT FEW HOURS...BUT PER LATEST
TRENDS...SUSPECT MUCH OF THIS WILL ALSO DIMINISH AS ITS ASSOCIATED
CONVECTION IS ALL BUT GONE AT THE MOMENT. WILL OF COURSE BE
WATCHING THE LIKELY REDEVELOPMENT OF MORE CONVECTION WELL UPSTREAM
LATER THIS AFTERNOON...SOME OF WHICH MAY TRY TO CLIP PARTS OF
EASTERN UPPER/FAR NORTHWEST LOWER BEFORE 00Z...BUT HAVE GENERALLY
SLOWED THINGS DOWN BY A FEW HOURS. OUTSIDE OF THAT...AND SOME
ADDITIONAL CU PROBABLY FIRING ACROSS THE REGION...LOOKING VERY
SUMMER-LIKE...WITH CURRENT HIGHS WELL INTO THE 80S TO AROUND 90
LOOKING JUST FINE. ELEVATED FIRE DANGER FOR SURE WITH VERY DRY
GROUND AND GUSTY WINDS.
UPDATE ISSUED AT 646 AM EDT WED AUG 21 2013
SPOTTY RADAR RETURNS POPPING UP OVER NORTHERN LAKE MICHIGAN AS MID
CLOUD CONTINUES TO EXPAND EASTWARD. MINNESOTA MCS STARTING TO
WEAKEN...HAS LOST MOST OF ITS CLOUD-GROUND LIGHTNING AND CLOUD
TOPS STARTING TO WARM. NO MAJOR CHANGES FROM EARLIER THINKING.
&&
.SHORT TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 407 AM EDT WED AUG 21 2013
PATTERN SYNOPSIS/FORECAST...BROAD BELT OF WEAKLY CYCLONIC STRONG
WESTERLIES LIE JUST NORTH OF THE U.S./CANADA BORDER FROM BRITISH
COLUMBIA INTO NORTHWEST ONTARIO...CONTAINING AN ELONGATED SHORT WAVE
TROUGH RUNNING FROM HUDSON BAY SOUTHWEST INTO SASKATCHEWAN. SMALL
UPPER LOWS WERE SPINNING OFF THE CALIFORNIA COAST AS WELL AS OVER
ILLINOIS/INDIANA EARLY THIS MORNING. UPPER LEVEL FLOW RELATIVELY
WEAK ACROSS THE GREAT LAKES...STUCK BETWEEN THE STRONGER HEIGHT
GRADIENT TO THE NORTH AND THE UPPER LOW SOUTH OF THE STATE (10-15KT
500MB WINDS OFF 00Z APX/GRB/DTX/BUF SOUNDINGS). MIDNIGHT SURFACE
ANALYSIS SHOWS A COLD FRONT ASSOCIATED WITH THE CANADIAN UPPER
JET/SHORT WAVE LYING ACROSS NORTHWEST ONTARIO...SOUTHWEST TO A
1003MB FRONTAL WAVE OVER NORTHWEST MINNESOTA AND EXTENDING BACK INTO
THE DAKOTAS. HIGH PRESSURE WAS LOCATED OVER THE MID ATLANTIC...WITH
SOUTH/SOUTHWEST BOUNDARY LAYER FLOW INTO THE GREAT LAKES/UPPER
MIDWEST BETWEEN THESE FEATURES. INCREASINGLY HUMID AIR MASS AHEAD
OF THE COLD FRONT WITH WIDESPREAD 60+ DEW POINTS ACROSS THE GREAT
LAKES/MIDWEST...WITH A POOL OF 70+ DEW POINTS ACROSS THE EASTERN
DAKOTAS/MINNESOTA CLOSER TO THE COLD FRONT. SEVERAL AREAS OF
CONVECTION HAVE SPROUTED UP ALONG THE FRONT FROM THE DAKOTAS INTO
ONTARIO...SUBTLE 700MB SHORT WAVE TROUGH ALSO KICKED OFF A SMALL
AREAS OF SHOWERS OVER CENTRAL WISCONSIN ALONG 850MB MOISTURE
GRADIENT. CLOSER TO HOME...SKIES WERE MAINLY CLEAR EARLY THIS
MORNING ACROSS NORTHERN MICHIGAN.
DECENT COLD ADVECTION OUT AHEAD OF THE CANADIAN SHORT WAVE TROUGH
SUGGEST A CONTINUED EASTWARD PROGRESSION TODAY...AND SOME DIGGING AS
WELL WHICH SHOULD BRING HEIGHT FALLS INTO MICHIGAN BY TONIGHT. THIS
IN TURN WILL PUSH THE COLD FRONT ACROSS THE UPPER MIDWEST AND INTO
WESTERN UPPER MICHIGAN/WISCONSIN BY LATE AFTERNOON...AND EVENTUALLY
ACROSS NORTHERN/CENTRAL LOWER MICHIGAN BY DAYBREAK THURSDAY. SO
SHORT TERM FORECAST ISSUES WILL PRIMARILY BE FOCUSED ON SOME MUCH
NEEDED PRECIPITATION CHANCES AHEAD OF THE APPROACHING COLD FRONT.
TODAY/TONIGHT...WEATHER: FIRST CONCERN IS WEAK 700MB WAVE MOVING
TOWARD LOWER MICHIGAN EARLY THIS MORNING...ALREADY PUSHING SOME MID
CLOUDS INTO LAKE MICHIGAN. CONCERN IS THAT WITH INCREASING LOW
LEVEL MOISTURE WE MAY SEE ENOUGH ELEVATED INSTABILITY TO POP SOME
SHOWERS THIS MORNING MAINLY ACROSS EASTERN UPPER/PERHAPS FAR
NORTHWEST LOWER. CHANCES APPEAR RATHER SUBTLE...WHICH MAKES IT
DIFFICULT TO DETERMINE IF THREAT IS SUFFICIENT TO ADD POPS TO THE
MORNING FORECAST. BUT STARTING TO SEE SOME CONVECTION OVER EASTERN
LAKE SUPERIOR OVER PAST COUPLE OF HOURS...SO THIS IDEA MAY NOT BE
TOO FAR FETCHED. WILL ALSO KEEP AN EYE ON SMALL MCS OVER NORTHERN
MINNESOTA...WHICH IS MOSTLY TRACKING EAST. THINK THIS WILL TEND TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR IN A FEW HOURS. BUT
MAIN SHOW AS FAR AS PRECIP GOES WILL BE ALONG UPSTREAM COLD FRONT
ACROSS WESTERN UPPER MICHIGAN/WISCONSIN/ SOUTHERN MINNESOTA...MLCAPE
VALUES AHEAD OF THE FRONT FORECAST TO EXCEED 3000J/KG THIS
AFTERNOON...WITH FRONTAL FORCING AUGMENTED BY INCREASING DIFLUENCE
ALOFT. SO THUNDERSTORMS EXPECTED TO DEVELOP UPSTREAM THIS AFTERNOON
AND WORK EAST TOWARD THE FORECAST AREA BY LATE AFTERNOON AND (MORE
LIKELY) EARLY EVENING. REMAINING CONVECTIVE ACTIVITY WILL CROSS THE
FORECAST AREA TONIGHT. MAIN SEVERE THREAT WILL BE UPSTREAM ACROSS
WESTERN UPPER/WISCONSIN WHERE INSTABILITY WILL BE GREATEST...STORMS
WILL ARRIVE IN NORTHERN MICHIGAN ON THE DOWNWARD SIDE OF THE DIURNAL
CYCLE. WILL HAVE TO SEE HOW MUCH INERTIA CONVECTION HAS ONCE IT
ARRIVES.
TEMPERATURES: HIGHS TODAY ONCE AGAIN SHOULD BE WELL INTO THE 80S/
AROUND 90 ACROSS NORTHERN LOWER. LOWS THURSDAY MORNING SHOULD BE
MOSTLY 60S.
WINDS: BREEZY DAY ANTICIPATED ACROSS NORTHERN MICHIGAN AHEAD OF THE
COLD FRONT...ESPECIALLY ACROSS UPPER MICHIGAN WHERE WIND GUSTS OF
30+MPH PROBABLE. NORTHERN LOWER WINDS MORE IN THE 10-20G25MPH
RANGE. WINDS WILL DIMINISH THIS EVENING WITH LOSS OF MIXING...
EVENTUALLY SWINGING AROUND TO THE NORTHWEST WITH FRONTAL PASSAGE
OVERNIGHT.
&&
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 407 AM EDT WED AUG 21 2013
THE SURFACE COLD FRONT WILL CONTINUE ITS TREK ACROSS
THE REGION THURSDAY MORNING TAKING ANY LEFTOVER SHOWERS OR STORMS
ACROSS SOUTHEAST COUNTIES ALONG WITH IT. MEANWHILE...A LARGE AREA OF
SURFACE HIGH PRESSURE FROM CANADA WILL BRING COOLER CONDITIONS INTO
THE REGION LATER THURSDAY THROUGH SATURDAY. IN ADDITION...MUCH DRIER
AIR ALONG WITH GUSTY WINDS...WILL LIKELY LEAD TO ELEVATED FIRE
DANGER ONCE AGAIN THURSDAY AFTERNOON. INCREASING RIDGING ALOFT IS
THEN EXPECTED TO RESULT IN ANOTHER WELCOMED WARMING TREND FOR SUNDAY
INTO THE BEGINNING OF NEXT WEEK (IT IS SUMMER AFTER ALL). WARM
ADVECTION DRIVEN SHOWERS AND THUNDERSTORMS ARE POSSIBLE SUNDAY INTO
MONDAY...THOUGH EXTENDED MODELS CONTINUE TO VARY ON THE TIMING AND
COVERAGE OF POSSIBLE CONVECTION. THE MAIN ISSUE IS THE WHEREABOUTS
OF A SURFACE WARM FRONT NEAR OR ACROSS THE REGION...SO CONFIDENCE
CONTINUES TO REMAIN ON THE LOW SIDE. EXTENDED MODELS ARE ADVERTISING
850 MB TEMPERATURES OF WELL INTO THE TEENS TO NEAR 20 C FOR THE
BEGINNING OF NEXT WEEK. SO DEPENDING UPON THE AMOUNT OF CLOUD
COVER...TEMPERATURES MAY APPROACH 90 OR SLIGHTLY HIGHER ACROSS SOME
AREAS...THOUGH LATEST MODEL GUIDANCE IS ONLY IN THE MIDDLE 80S AT
BEST. THIS IS SOMETHING TO MONITOR FOR SURE. FORECAST HIGH
TEMPERATURES WILL RANGE FROM THE LOWER AND MIDDLE 70S NORTH TO THE
UPPER 70S SOUTHEAST FOR BOTH FRIDAY AND SATURDAY. IN
ADDITION...ANOTHER COUPLE OF COOL NIGHTS WITH LOW LYING AREAS LIKELY
FALLING INTO THE LOWER AND MIDDLE 40S EARLY FRIDAY AND SATURDAY
MORNINGS. HIGHS MONDAY THROUGH TUESDAY GENERALLY RANGING FROM THE
MIDDLE 70S NORTH TO THE MIDDLE 80S SOUTH (WHICH AS MENTIONED ABOVE
HAVE THE POTENTIAL TO BE SEVERAL DEGREES WARMER). LOWS IN THE UPPER
50S AND LOWER 60S SUNDAY MORNING THEN MAINLY IN THE 60S FOR THE
REMAINDER OF THE PERIOD.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 123 PM EDT WED AUG 21 2013
VFR THROUGH LATE EVENING...WITH JUST SOME PASSING MID LEVEL
CLOUDS AND CONTINUED GUSTY SOUTHWEST WINDS AT 15 TO 20 KNOTS. WILL
BE WATCHING TO SEE JUST HOW UPSTREAM CONVECTION UNFOLDS THROUGH
THE EVENING HOURS ACROSS WISCONSIN...BUT WHATEVER IS LEFT OF THIS
ACTIVITY WILL CROSS THE TERMINAL SITES ROUGHLY 02-07Z JUST AHEAD
OF A COLD FRONT. BASED ON THE LATEST INDICATIONS...MBL STANDS THE
BEST SHOT TO SEE SOME THUNDER...SO WILL MAINTAIN A LATE TEMPO
MENTION THERE...BUT JUST A VICINITY MENTION FOR APN/TVC/PLN. AS
THE FRONT PASSES...CAN ENVISION A ROUND OF FOG AND LOW STRATUS
DEVELOPING AS MOISTURE LINGERS JUST BEHIND THE SHALLOW
BOUNDARY...WITH A PERIOD OF IFR CONDITIONS EXPECTED FOR ALL SITES.
THAT WILL IMPROVE RAPIDLY THROUGH THURSDAY MORNING AS MUCH DRIER
AIR ARRIVES...WITH A RETURN TO VFR ALL SITES BY 14Z AT THE LATEST
WITH NORTHERLY WINDS 8-12 KNOTS.
&&
.MARINE...
ISSUED AT 407 AM EDT WED AUG 21 2013
SMALL CRAFT ADVISORIES ALREADY UP FOR LAKE MICHIGAN (THROUGH THIS
EVENING) AND LAKE SUPERIOR (THROUGH THIS AFTERNOON) NEARSHORE ZONES
FOR GUSTY WINDS AND BUILDING WAVES ON LAKE MICHIGAN. WINDS WILL
SWING AROUND TO THE NORTHWEST OVERNIGHT WITH A COLD FRONT
PASSAGE...AT THIS POINT PROBABLY REMAINING BELOW SMALL CRAFT
CRITERIA ON TUESDAY.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY UNTIL 2 AM EDT THURSDAY FOR LHZ345.
LM...SMALL CRAFT ADVISORY UNTIL 2 AM EDT THURSDAY FOR LMZ323-341-342-
344>346.
LS...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LSZ321-322.
&&
$$
UPDATE...LAWRENCE
SYNOPSIS...JPB
SHORT TERM...JPB
LONG TERM...AJS
AVIATION...LAWRENCE
MARINE...JPB
AREA FORECAST DISCUSSION
NWS NORTH PLATTE NE
1248 PM CDT WED AUG 21 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM CDT WED AUG 21 2013
SATELLITE AND LIGHTNING SUGGEST A DISTURBANCE ACROSS NERN UT/NWRN
COLO THIS MORNING. THIS DISTURBANCE SHOULD FIRE OFF THE LARAMIE
RANGE AROUND 18Z MARKING THE START OF CONVECTION LATER THIS
AFTERNOON ACROSS WRN AND EVENTUALLY NCNTL NEB TONIGHT. THE RAP
MODEL SHOWS A TSTM COMPLEX DEVELOPING OFF THE PINE RIDGE AROUND
19Z AND THE HRRR IS VERY BUSY ACROSS THE NEB PANHANDLE AT 20Z. IT
ALSO INDICATES STORM INTENSIFICATION ACROSS HOLT COUNTY IN THE
DEEP MOISTURE SECTOR.
GIVEN THAT THE MODELS ARE SHOWING PRECIPITABLE WATER INCREASING
TO AROUND 1.75 INCHES EAST OF HIGHWAY 83 TONIGHT AND THAT WEAK
WINDS ALOFT WILL PRODUCE STORM MOTION OF 10 KTS OR LESS...LOCALLY
HEAVY RAIN SHOULD DEVELOP IN THIS AREA OF RICH MOISTURE.
ELSEWHERE STORM ACTIVITY SHOULD BE SCATTERED OR LESS. NOTE THAT A
MIDLEVEL COLD FRONT IS OPERATING THIS MORNING ACROSS NRN NEB
WHICH WOULD ACTIVATE SCATTERED CONVECTION EARLY THIS AFTERNOON IN
RESPONSE TO DAYTIME HEATING. A STATIONARY FRONT...CURRENTLY
ACROSS SRN SD SHOULD DRIFT SOUTH INTO NRN NEB AT THE SAME TIME
WITH LOW LEVEL MOISTURE POOLING ALONG THE FRONT ADDING FOCUS TO
THE RAIN EVENT.
WINDS ALOFT ARE WEAK AT 35 KTS OR LESS WHICH WILL LIMIT SEVERE
WEATHER POTENTIAL TO ISOLATED COVERAGE. SCATTERED LIGHT SHOWERS
SHOULD CONTINUE THIS MORNING ALONG THE MID LEVEL FRONT ACROSS NRN
NEB WHICH WOULD THEN INTENSIFY TO THUNDERSTORMS EARLY THIS
AFTERNOON AND PERHAPS APPROACH SEVERE LIMITS LATE THIS AFTERNOON
AS THE DISTURBANCE APPROACHES.
MOISTURE TRANSPORT VECTORS ARE RELATIVELY WEAK THIS AFTERNOON AND
THIS EVENING WHICH WOULD LIMIT THE OVERALL HEAVY RAIN THREAT.
STILL ALL THE GFS ENSEMBLE MEMBERS SHOW A HEAVY RAIN CENTER
DEVELOPING ACROSS NCNTL NEB TONIGHT...LIKELY A RESULT OF THE LOW
LEVEL JET INCREASING TO AROUND 30 KT. NONE OF THE OTHER MODELS
SHOW THIS. THE GEMREG IS THE CLOSEST BUT HAS THE FRONT AND HEAVY
RAIN ACROSS SERN SD WHILE THE NAM AND ECM ARE VERY MODEST WITH
QPF BUT SHOW NCNTL NEB LIKE THE GFS ENSEMBLE.
HIGHS TODAY RANGE FROM THE LOWER 80S NORTH TO MID 90S SOUTH.
EXTENSIVE MID AND HIGH LEVEL CLOUDINESS WILL LIMIT HIGHS.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 330 AM CDT WED AUG 21 2013
MAIN CONCERNS WITH THE LONG TERM FOCUS WITH THUNDERSTORM CHANCES
EARLY ON...THEN TRANSITION INTO TEMPERATURES BY THE WEEKEND INTO
NEXT WEEK.
UPPER LEVEL RIDGE WILL BUILD EAST FROM THE SOUTHERN/CENTRAL
ROCKIES OVER THE CENTRAL PLAINS BY THE WEEKEND. MEANWHILE A WEAK
COLD FRONT WILL DRIFT SOUTH ACROSS THE STATE...THEN BECOMES
REPLACED BY A HIGH PRESSURE BUILDING OVER THE UPPER MISS RVR
VALLEY AND THE GREAT LAKES. A SFC LEE TROUGH DEVELOPS ALONG THE
FRONT...AND REMAINS QUASI-STATIONARY THROUGH THE WEEKEND.
THUNDERSTORM CHANCES INITIALLY ON THURSDAY...GENERALLY
ALONG/NORTH OF THE FRONT...WHERE STEEPER LAPSE RATE PERSIST. ALSO
GOING TO BE ALONG THE NORTHERN SIDE OF THE DEVELOPING RIDGE...AND
ASSOCIATED WITH A MID LEVEL DISTURBANCE. AS THE SHORT WAVE PUSHES
EAST...CHANCE FOR STORMS DIMINISHES THURSDAY NIGHT. THE NEXT
CHANCE FOR STORMS IS ALONG THE HIGHER TERRAIN AND THE LEE SIDE
TROUGH GENERALLY TO THE WEST OF THE CWA. MODELS BRING ANOTHER
DISTURBANCE ACROSS THE ROCKIES SATURDAY WHICH HAS THE POTENTIAL TO
SUSTAIN ACTIVITY INTO THE WESTERN ZONES...AND WILL HAVE SOME LOW
POPS. OTHERWISE RIDGE WILL BRING DRY CONDITIONS.
TEMPERATURES ON THURSDAY ARE EXPECTED TO BE COOL WITH SOME CLOUDS
AND COOLER AIR FROM THE COLD FRONT. 00Z MODEL GUIDANCE HAS COME
IN SEVERAL DEGREE ABOVE THE 12Z RUN...HOWEVER FORECAST DOES NOT
JUMP AS FAR AS GUIDANCE YET...AS EXPECT THE CLOUDS TO KEEP TEMPS
IN THE LOWER TO MID 80S. BY FRIDAY THE WARM UP BEGINS...AS HIGH
RETURN TO WELL ABOVE NORMAL 90S FOR THE WEEKEND AND TO START NEXT
WEEK.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1242 PM CDT WED AUG 21 2013
A COLD FRONT WILL REMAIN NEARLY STATIONARY FROM NEAR KONL TO KOGA
THIS AFTERNOON. SCT TSTMS ARE EXPECTED TO DEVELOP ALONG AND NEAR
THE FRONT BY LATE AFTERNOON. TSTM COVERAGE WILL INCREASE THIS
EVENING AS A 45 KT SOUTHERLY LOW LEVEL JET NOSES INTO THE AREA
FROM WESTERN KS. THE MOST CONCENTRATED AREA FOR STORMS THIS
EVENING WILL EXTEND ALONG A LINE FROM KONL TO KBBW TO KLBF.
OUTSIDE OF ANY TSTM ACTIVITY...VFR CONDITIONS SHOULD RULE. SFC
WINDS WILL BE NORTHEAST AT 5 TO 10 KTS TO THE NORTH OF THE
FRONT...WITH SOUTHEAST WINDS 5 TO 10 KTS AHEAD OF THE FRONT.
VRB AND GUSTY WINDS WILL BE ENCOUNTERED NEAR ANY TSTM ACTIVITY.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...CDC
LONG TERM...MASEK
AVIATION...TAYLOR
AREA FORECAST DISCUSSION
NWS OMAHA/VALLEY NE
1244 PM CDT WED AUG 21 2013
.AVIATION...18Z TAFS FOR KOFK...KLNK AND KOMA.
VFR CONDITIONS ARE EXPECTED INTO THE LATE AFTERNOON AND EVENING
AS SOUTH WINDS AROUND 15KT AND SCT/BKN MID/HIGH LEVEL CLOUDS MOVE
ALONG THE NEBRASKA SOUTH DAKOTA BORDER INTO NORTHWEST IOWA. A
COLD FRONT CONTINUES TO SLOWLY DROP INTO NORTHERN NEBRASKA AND
NORTHWEST IOWA...AND WILL APPROACH KOFK BY 04Z. SCATTERED SHOWERS
AND THUNDERSTORMS ARE POSSIBLE ALONG THE FRONT...AFFECTING KOFK
FROM 04Z THROUGH 08Z...AND THE KLNK AND KOMA AREAS AFTER 06Z.
ISOLATED SEVERE THUNDERSTORMS...PRIMARILY IN THE KOFK
AREA...COULD BE POSSIBLE. ATTENDANT MVFR/IFR CONDITIONS COULD
OCCUR IN ANY THUNDERSTORM. SHOWERS AND STORMS WILL LIKELY REMAIN
IN THE AREA INTO THE 14Z TO 16Z TIME PERIOD.
&&
.PREV DISCUSSION... /ISSUED 300 AM CDT WED AUG 21 2013/
DISCUSSION...
TEMPERATURES THROUGH THE PERIOD AND RAIN CHANCES LATE TODAY INTO
FRIDAY WILL BE THE MAIN FORECAST CONCERNS.
WV/IR SATELLITE LOOP SHOWS A PULSING AREA OF CONVECTION FROM
SOUTHEAST SOUTH DAKOTA INTO NORTHWEST NEBRASKA AT 07Z IN ADVANCE
OF A WEAK SURFACE COLD FRONT FROM NORTHWEST MINNESOTA INTO FAR
NORTHWEST NEBRASKA. 00Z MODELS SIMILAR IN PLACING ISOLATED TO
WIDELY SCATTERED CONVECTION IN THE VICINITY OF THE FRONT TODAY AND
ESPECIALLY LATE THIS AFTERNOON AS IT WORKS INTO NORTHERN PORTIONS
OF IOWA AND NEBRASKA WITH RAP FORECAST SOUNDINGS SHOWING LITTLE
CAP IN PLACE. CONVECTION LIKELY TO EXPAND DURING THE EVENING AS
LOW LEVEL JET FEEDS INTO THE COMPLEX. SURFACE FRONT STALLS NEAR
THE SOUTHERN NEBRASKA BORDER BY THURSDAY MORNING THEN BEGINS TO
LIFT BACK NORTH DURING THE DAY WITH A CONTINUED CHANCE OF SHOWERS
AND THUNDERSTORMS NORTH AND EAST OF THE BOUNDARY INTO FRIDAY.
SOME COOLING ON THURSDAY...ESPECIALLY NORTH...ASSOCIATED WITH
CLOUDS AND PRECIP BEFORE THE WARM AIR WORKS BACK INTO THE AREA
ON FRIDAY.
EXTENDED PERIOD STILL HOT AND DRY WITH UPPER LEVEL HIGH PRESSURE
CENTERED OVER THE CENTRAL PART OF THE NATION.
FOBERT
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
99/99
AREA FORECAST DISCUSSION
NWS RALEIGH NC
150 PM EDT WED AUG 21 2013
.SYNOPSIS...
AN UPPER LEVEL TROUGH WILL APPROACH THE CAROLINAS FROM THE WEST THIS
EVENING...THEN TRACK EAST ACROSS THE REGION ON THURSDAY. SURFACE
HIGH PRESSURE WILL STRENGTHEN ACROSS THE OHIO VALLEY IN THE WAKE OF
THE UPPER LEVEL TROUGH...DRIVING A COLD FRONT SOUTHWARD INTO THE
CAROLINAS DURING THE DAY FRIDAY.
&&
.NEAR TERM /TODAY AND TONIGHT/...
AS OF 1025 AM WEDNESDAY...
THE LATEST SURFACE ANALYSIS SHOWED A DIFFUSE FRONT ALONG THE
CAROLINA COAST WITH WEAK HIGH PRESSURE REMAINING OVER CENTRAL NORTH
CAROLINA WEST OF THE FRONT. IN THE SOUTHWEST FLOW ALOFT...WEAK
DIFFLUENCE ON WATER VAPOR AND A MID-LEVEL SHORTWAVE IN A MOIST FLOW
ALOFT HELPED TO PRODUCE SCATTERED TO NUMEROUS SHOWERS MAINLY ALONG
AND NORTH OF U.S. 64 THIS MORNING. THESE SHOWERS WILL CONTINUE TO
MOVE NORTHEAST LEAVING A PERIOD OF ISOLATED TO SCATTERED SHOWERS AS
THE MID-LEVEL WAVE CONTINUES TO MOVE NORTHEAST. DURING THE
AFTERNOON...PRECIPITABLE WATER VALUES WILL REMAIN NEAR TWO INCHES...
AND MODEST HEATING SHOULD BE SUFFICIENT TO RESULT IN MLCAPE IN THE
LOWEST KM FROM 500J/KG TO 1500J/KG...GREATEST TOWARD THE COASTAL
PLAIN. 1000-500MB LAPSE RATES ARE ONLY FORECAST TO BE 6C/KM OR LESS.
THE RUC ACTUALLY FORECASTS WEAK SUBSIDENCE THIS AFTERNOON IN THE
WAKE OF THE MID-LEVEL SHORTWAVE...AND THE GFS BUFR SOUNDINGS ARE
SOMEWHAT CAPPED TO DEEP CONVECTION. ON THE OTHER HAND...MODIFIED
MORNING SOUNDINGS AND RUC AND NAM BUFR SOUNDINGS SUGGEST ENOUGH
INSTABILITY TO PROVIDE FOR ISOLATED-TO-SCATTERED SHOWERS AND
THUNDERSTORMS THIS AFTERNOON INTO EARLY THIS EVENING. THE HIGHEST
PROBABILITY OF ANY SHOWERS SHOULD BE OVER THE NORTHWEST PIEDMONT
WHERE 850MB THETA-E AND K INDICES ARE HIGHEST...CLOSER TO WHERE THE
BETTER 0-3KM SHEAR WILL BE FOR MOST OF THE AFTERNOON RELATIVE TO THE
REST OF CENTRAL NORTH CAROLINA...AND WHERE THE RUC SHOWS AN SLIGHT
INCREASE IN 850MB WINDS. TEMPERATURES STILL MOSTLY BELOW NORMAL WITH
HIGHS IN THE 80S.
TONIGHT...EXPECT CHANCES FOR SHOWERS TO DIMINISH WITHIN A FEW HOURS
AFTER SUNSET...THOUGH A TOKEN SLIGHT CHANCE WILL PERSIST GIVEN SUCH
DEEP MOISTURE AND MARGINAL HEIGHT FALLS ALOFT AS THE UPPER LEVEL
WAVE TRACKS INTO THE MID-ATLANTIC TO THE NORTH OF CENTRAL NORTH
CAROLINA. LOWS TONIGHT SIMILAR TO PREVIOUS NIGHTS IN THE 68-73F
RANGE.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 300 AM WEDNESDAY...
A PRE-FRONTAL TROUGH WILL SET UP OVER THE EASTERN PIEDMONT/SANDHILLS
THURSDAY AS THE MEAN FLOW BECOMES MORE WESTERLY IN THE REAR OF THE
DEPARTING MID/UPPER TROUGH OFFSHORE. THIS SHOULD LEAD TO A REDUCTION
IN THE CHANCE OF CONVECTION EXCEPT ALONG AND EAST OF THE TROUGH
THURSDAY AFTERNOON INTO THE EVENING. QPF OF AROUND 0.25 WILL BE
FORECAST FROM AROUND KFAY NE TO KRDU AND RWI (AREAL AVERAGE)... WITH
0.01 TO THE WEST OVER THE TRIAD REGION. CHANCE POP ALL ZONES BUT
ONLY LOW CHANCE (25-30 PERCENT) NW... TO 50 IN THE SE. HIGHS SHOULD
REBOUND INTO THE MID TO UPPER 80S EXCEPT AROUND 90 IN THE SE. PW`S
WILL ALSO REDUCE TO LESS THAN 1.25 IN THE NW TO AROUND 1.5 IN THE
EAST. DEW POINTS SHOULD MIX OUT INTO THE LOWER TO MID 60S NW...
ENHANCING CONFIDENCE IN THE LOWER POP FORECAST.
THURSDAY NIGHT AND FRIDAY... THE COLD FRONT SHOULD EVENTUALLY
OVERTAKE THE PRE-FRONTAL TROUGH OVER THE SOUTHERN AND EASTERN ZONES
FRIDAY. UNTIL THEN... ANOTHER DAY OF MOSTLY SCATTERED SHOWERS AND
THUNDERSTORMS IS EXPECTED... MAINLY IN THE SOUTH AND EAST (WHERE
PW`S REMAIN NEARLY 1.5 INCHES)... ALONG AND AHEAD OF THE CONVERGENCE
ZONE. THE CHANCE OF SHOWERS/STORMS WILL DIMINISH OVERNIGHT FRIDAY
NIGHT AS THE FRONT SETTLES NEAR THE SC BORDER 12Z SATURDAY. LOWS
65-70. HIGHS FRIDAY WITH A WIND SHIFT TO THE NE... 86-91.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 300 AM WEDNESDAY...
A LARGE UPPER TROUGH IS FORECAST TO BE ANCHORED IN THE WESTERN
ATLANTIC AS AN UPPER RIDGE BECOMES ESTABLISHED OVER THE PLAINS THIS
PERIOD. AN ANOMALOUS MEAN NORTHERLY FLOW WILL RESULT FROM THE GREAT
LAKES AND NEW ENGLAND SOUTHWARD DEEP INTO SC/GA. THIS WILL BE A DRY
AND COOL FLOW FOR LATE AUGUST. SURFACE CAA WILL BE MOST PRONOUNCED
SATURDAY AND SUNDAY AS STRONG (~1026+ MB) SURFACE HIGH PRESSURE
BUILDS INTO NC FROM NY/PA. SATURDAY WILL BE THE DAY WITH THE
STRONGEST DAA AS THE MAIN COLD FRONT WILL BEGIN THE DAY NEAR THE SC
BORDER... BUT SHIFT DEEP INTO SC/GA BY LATE SATURDAY. SENSIBLE
WEATHER... PARTLY TO MOSTLY SUNNY SATURDAY. MOSTLY SUNNY SUNDAY.
CLEAR SATURDAY NIGHT. HIGHS SATURDAY AND SUNDAY SHOULD BE ONLY 80-85
(A GOOD 5-8 DEGREES BELOW NORMAL). LOWS SUNDAY AND MONDAY SHOULD BE
IN THE 50S NORTH... AND LOWER 60S SOUTH (ALMOST 10 DEGREES BELOW
NORMAL).
FOR MONDAY THROUGH TUESDAY... A GRADUAL WARMING TREND BUT STILL DRY.
SURFACE HIGH PRESSURE SHOULD BECOME ANCHORED OVER THE APPALACHIANS
AS THE UPPER RIDGE OVER THE MID-MISSISSIPPI VALLEY REMAINS STRONG.
SENSIBLE WEATHER... MOSTLY CLEAR/MOSTLY SUNNY. LOWS 58-65. HIGHS IN
THE 80S.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AS OF 150 PM WEDNESDAY...
24-HR TAF PERIOD:
AREAS OF MVFR CEILINGS WILL CONTINUE TO SLOWLY LIFT AND IMPROVE TO
VFR BETWEEN 18 TO 20Z. SCATTERED SHOWERS AND THUNDERSTORMS WILL HAVE
TO POTENTIAL TO IMPACT ALL TERMINALS THIS AFTERNOON AND INTO THE
EVENING WITH THE BEST CHANCE TOWARD THE TRIAD AND KINT AND KGSO.
WHILE SHOWERS SHOULD DIMINISH IN COVERAGE THIS EVENING...THERE WILL
BE A CHANCE OF SHOWERS WELL INTO THE OVERNIGHT HOURS WITH THE
APPROACH OF THE TROUGH INTO THE REGION.
WHILE ONE CANNOT TOTALLY RULE OUT THE POTENTIAL FOR SUB-VFR CEILINGS
TO DEVELOP OVERNIGHT...THE MOISTEN LADEN BOUNDARY LAYER IN PLACE
WILL BEGIN TO DRY IN RESPONSE TO INCREASING LOW-LEVEL WESTERLY FLOW.
LOOKING AHEAD:
ISOLATED TO SCATTERED SHOWERS AND STORMS CAN BE EXPECTED
THURSDAY/FRIDAY AS A COLD FRONT SLOWLY APPROACHES FROM THE NORTH.
VFR CONDITIONS ARE THEN EXPECTED IN THE WAKE OF THE FRONT SAT
THROUGH EARLY NEXT WEEK AS DRY HIGH PRESSURE BUILDS INTO THE
MID-ATLANTIC.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...VINCENT
NEAR TERM...DJF/VINCENT
SHORT TERM...BADGETT
LONG TERM...BADGETT
AVIATION...CBL
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
521 PM EDT WED AUG 21 2013
.SYNOPSIS...
HIGH PRESSURE CENTERED OVER THE MID-ATLANTIC STATES WILL MAINTAIN
CONTROL OF OUR WEATHER INTO THURSDAY. A COLD FRONT WILL CROSS THE
REGION LATE THURSDAY INTO EARLY FRIDAY...FOLLOWED BY CANADIAN HIGH
PRESSURE. A FEW SHOWERS AND THUNDERSTORMS ARE POSSIBLE ALONG AND
AHEAD OF THE FRONT...FOLLOWED BY SUNNY AND DRIER CONDITIONS FRIDAY
INTO THIS WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
REGIONAL RADAR LOOP SHOWING CONVECTION INCREASING IN COVERAGE AND
SPREADING NORTH OF THE MASON DIXON LINE IN RESPONSE TO DIURNAL
HEATING AND INCREASING LG SCALE FORCING AHEAD OF UPPER LOW
APPROACHING FROM OHIO. MDL SIMULATED REFLECTIVITY...WHICH USUALLY
PERFORMS WELL IN STRONGLY FORCED SCENARIOS SUCH AS THIS...SUGGESTS
SHRA AND TSRA WILL OVERSPREAD THE SOUTHERN COUNTIES THIS
EVENING...WITH THE GREATEST COVERAGE BTWN 23Z AND 02Z. HAVE
ADJUSTED POPS ACCORDINGLY WITH POPS INCREASED TO ARND 50 PCT OVR
THE SOUTHERN COUNTIES. SPC MESOANALYSIS INDICATES CAPES ARND 2500
J/KG LATE THIS AFTN...SO WILL HAVE TO WATCH FOR A LOCALLY SVR
PULSE TYPE STORM ACROSS THE SOUTH THIS EVENING. RAP SHOWS WIND
SHEAR IS WEAK...SO ANYTHING MORE THAN ISOLD SVR UNLIKELY.
WILL GRADUALLY TAPER OFF POPS TONIGHT...AS WEAKENING SHORTWAVE
MOVES INTO THE AREA AND BLYR COOLS/STABILIZES. BLYR ACROSS
NORTHERN PA WILL LIKELY REMAIN TOO DRY TO SUPPORT ANY CONVECTION.
HOWEVER...WILL MENTION AT LEAST A SLIGHT CHC ACROSS ALL OF CENTRAL
AND SOUTHERN PA...WHERE SOUTHERLY FLOW AHEAD OF SHORTWAVE WILL
PUSH DWPTS WELL INTO THE 60S.
TONIGHT WILL BE MILDER THAN RECENT NIGHTS...WITH HIGH DEWPOINTS
AND SCT/BKN CLOUD COVER.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
A PERIOD OF WEAK RIDGING SHOULD BRING A PERIOD OF DRY CONDITIONS
TO MOST OF CENTRAL PENN ON THURS BEFORE AN APPROACHING COLD FRONT
FROM THE GLAKES BRINGS ANOTHER THREAT OF CONVECTION.
A RIBBON OF HIGHER PWATS BETWEEN 1.5 AND 1.75 INCHES AND SLIGHTLY
STEEPER MID-LEVEL LAPSE RATES SHOULD SUPPORT SCT SHRA/TSRA
DEVELOPING ACROSS THE NW MTNS THURSDAY AFTN AND SLIDING SE THRU
THE EVENING AND EARLY OVERNIGHT.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
OVERVIEW...THE LATEST MODEL AND ENSEMBLE GUIDANCE REMAINS IN VERY
GOOD AGREEMENT IN THE LARGE SCALE MEAN FLOW PATTERN CONSISTING OF
A BUILDING/STRONG UPPER RIDGE OVER THE PLAINS/MS VLY WITH TROUGHS
JUST OFF THE WEST AND EAST COASTS. HOWEVER...THE PCPN PATTERN OVER
THE LOCAL AREA WILL BE MODULATED BY SHORTWV IMPULSES DIVING ESEWD
DOWN THE NERN/FRONT SIDE OF THE RIDGE WITHIN A NWLY FLOW ALOFT.
THEREFORE DESPITE ABOVE AVG CONFIDENCE IN THE MEAN PATTERN...THE
SMALLER SCALE EMBEDDED SYSTEM TIMING AND LOCAL QPF/SENSIBLE WX
IMPACT IS MORE UNCERTAIN. AS SUCH...THE FINAL DAY 3-7 GRIDS WERE
DERIVED USING A CONSENSUS BLEND IN AN EFFORT TO MITIGATE THE LOWER
CONFIDENCE IN THE SFC DETAILS AND TO BEHOLD REASONABLE CONTINUITY
THE FCST.
HIGHLIGHTS...PUSH OF ABNORMALLY DRY AIR WITH BELOW NORMAL PWS
BEHIND THE THUR NGT FROPA APPEARS DELAYED BY ABOUT 6 HRS ON THE
12Z CYCLE...SUGGESTING A LOW CHC FOR SHOWERS ALONG THE SRN TIER
ZONES EARLY FRI. OTHERWISE...A MODIFIED CANADIAN HIGH PRESSURE
SYSTEM WILL DOMINATE THE PATTERN THROUGH THE WEEKEND..BRINGING
RELATIVELY COOL NIGHTS WITH VALLEY FOG AND COMFORTABLE HUMIDITY
DURING THE DAY. EXPECT A MORE UNSETTLED AND INCREASINGLY HUMID
PATTERN TO EVOLVE THRU THE FIRST PART OF NEXT WEEK..AS THE FOCUS
SHIFTS TO UPPER-LEVEL DISTURBANCES CRESTING THE PLAINS RIDGE AND
DIVING ESEWD THRU THE GREAT LAKES TAKING AIM ON THE NE STATES.
MODELS SUGGEST THIS ENERGY MAY TRIGGER ONE OR MORE ORGANIZED TSTM
COMPLEXES AS THEY ROLL DOWN THE FRONT-SIDE OF THE RIDGE.
&&
.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
WIDELY SCT SHRA/TSRA WILL CONTINUE TO DEVELOP THIS AFTN ACROSS
FAR SRN PA. ADDED VCSH TO ALL SRN TAF SITES THRU THIS EVE.
A FEW SHRA/TSRA REMAIN POSS INTO TONIGHT...PRIMARILY ACROSS SRN
PA. SOME LIGHT FOG/HAZE IS POSSIBLE AS WELL.
SLIGHTLY BETTER CHC FOR SHRA/TSRA STATEWIDE ON THURS AS A COLD
FRONT APPROACHES FROM THE GREAT LAKES. THIS FRONT SHOULD PASS
SOUTH OF THE REGION THURS NIGHT...WITH IMPROVING FLYING CONDS FOR
FRI INTO THIS WEEKEND.
OUTLOOK...
THU-THU NIGHT...MVFR POSSIBLE WITH SCT SHRA/TSRA.
FRI-MON...GENERALLY VFR.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...EVANEGO
NEAR TERM...FITZGERALD/EVANEGO
SHORT TERM...EVANEGO
LONG TERM...STEINBUGL
AVIATION...EVANEGO
AREA FORECAST DISCUSSION
NWS SIOUX FALLS SD
1252 PM CDT WED AUG 21 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 349 AM CDT WED AUG 21 2013
CONVECTION ACROSS CENTRAL SOUTH DAKOTA RUNNING INTO THE CAP AS IT
WORKS EAST OF THE JAMES RIVER VALLEY. THE DYING CONVECTION HAS
PRODUCED HEAT BURSTS OVER THE PAST FEW HOURS IN BOTH CHAMBERLAIN
AND MITCHELL. HRRR SHOWS CONVECTION DEVELOPING IN THE NEXT FEW
HOURS ALONG WEAK BOUNDARY SLOWLY EAKING SOUTH THROUGH THE NORTHERN
CWA THIS MORNING. HAVE SOME 20 POPS TO COVER THE POTENTIAL OF
THIS...BUT STILL NOT CONVINCED THAT STORMS ARE GOING TO BE ABLE TO
GET AROUND THE CAP. AHEAD OF THE BOUNDARY...WILL BE ANOTHER WARM
AND HUMID DAY WITH HEAT INDEX VALUES A FEW DEGREES SHY OF ADVISORY
CRITERIA. MODELS INDICATE THAT A WEAK SHORTWAVE MOVING OUT OF
WESTERN SOUTH DAKOTA THIS MORNING MAY TRY TO INTERACT WITH THE
BOUNDARY POTENTIALLY PRODUCING THUNDERSTORMS ACROSS MAINLY
NORTHWEST IOWA. STEEP MID LEVEL LAPSE RATES LEAD TO MOST UNSTABLE
CAPE VALUES OF 2000-2500 J/KG....THOUGH STILL FAIRLY STRONG CAP TO
OVERCOME. IF STORMS ARE ABLE TO DEVELOP...VEERING PROFILE MAY AID
IN STORM ORGANIZATION...THOUGH WIND SPEEDS ARE SOMEWHAT WEAK. AS
SUCH...THE SEE TEXT SEVERE WEATHER OUTLOOK SEEMS REASONABLE WITH
CHANCE OF CONVECTION BEING VERY CONDITIONAL.
BOUNDARY IS EXPECTED TO STALL ACROSS THE SOUTHERN EDGE OF THE
FORECAST AREA TONIGHT CREATING ADDITIONAL CHANCES FOR
THUNDERSTORMS. TRIMMED BACK THE NORTHERN EXTENT OF POPS TONIGHT
WITH DRIER AIRMASS BEHIND THE FRONT MAKING IT DIFFICULT FOR
SHOWERS AND THUNDERSTORMS TO DEVELOP. EXPECT QUITE A THERMAL
GRADIENT ACROSS THE AREA FROM THE UPPER 50S ACROSS SOUTHWEST
MINNESOTA TO NEAR 70 ACROSS THE SOUTHERN EDGE OF THE FORECAST AREA
NEAR THE FRONT.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 349 AM CDT WED AUG 21 2013
CONVECTION CHANCES ARE SOMEWHAT TRICKY ON THURSDAY AS
BOUNDARY/THEATE ADVECTION LIFTS BACK TO THE NORTH. FORCING APPEARS
TO OUTRUN THE MOISTURE...AS LOW LEVEL MOISTURE APPEARS TO BE HARD TO COME
BY ACROSS THE NORTHERN CWA. THEREFORE...HAVE LIMITED CONVECTION CHANCES TO
SOUTHERN EDGE OF THE FORECAST AREA WHERE THE SLIGHTLY DEEPER
MOISTURE EXISTS.
HUMID CONDITIONS RETURN ON FRIDAY AS THE GULF OPENS BACK UP WITH
SOUTHERLY FLOW FEEDING INTO THE PLAINS. 850 HPA TEMPS WARM TO NEAR
20C DURING THE DAY LEADING TO HIGHS IN THE 80S TO NEAR 90.
STRONG LOW LEVEL JET OF 40-50 KNOTS IS EXPECTED TO DEVELOP FRIDAY
NIGHT. HAVE RAISED LOWS IN SW MN ALONG THE BUFFALO RIDGE AS
EXPOSED LOCATIONS WILL LIKELY HAVE TROUBLE COOLING OFF.
IN THE EXTENDED...SATURDAY THROUGH TUESDAY OF NEXT WEEK...A BROAD
UPPER LEVEL RIDGE REMAINS PARKED OVER THE CENTRAL PORTION OF THE
U.S. THROUGH THE PERIOD. WITH OUR AREA IN A SOUTHERLY FLOW IN
RESPONSE TO SURFACE RIDGING PARKED OVER THE EASTERN PART OF THE
NATION...MUCH ABOVE NORMAL TEMPERATURES WILL BE THE RULE. WITH
PROGGED 850 MB TEMPERATURES IN THE MID AND UPPER 20S C HIGHS WILL
GENERALLY RUN LOWER TO MID 90S EACH DAY...WITH HUMIDITY RETURNING AS
DEWPOINTS CLIMB INTO THE MID AND UPPER 60S. 925 MB TEMPERATURES
WOULD SUPPORT LOWS IN THE UPPER 60S TO LOWER 70S. IN TERMS OF
PRECIPITATION CHANCES DURING THE EXTENDED...MODELS HAVING USUAL
DIFFERENCES WITH REGARD TO MINOR SHORTWAVES ROUNDING THE UPPER THE
LEVEL RIDGE...THOUGH KEPT IT DRY THROUGH THE PERIOD WITH SUPPORT
FROM BOTH THE 00Z ECMWF AND GEM.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1245 PM CDT WED AUG 21 2013
PREDOMINATE VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. SCATTERED
LIGHT HIGH BASED CONVECTION WILL CONTINUE TO PUSH EASTWARD THROUGH
AROUND 21Z. SLOW MOVING WEAK FRONT SINKING SOUTHEAST THROUGH OUR
EASTERN FORECAST AREA WILL BECOME QUITE DIFFUSE AND EXIT THE AREA BY
AROUND 09Z. ADDITIONAL CONVECTION IS EXPECTED TO DEVELOP AFTER 21Z
ALONG THE FRONT AND IS EXPECTED TO TRACK PRIMARILY THROUGH THE
MISSOURI VALLEY AND NORTHWEST IOWA. ACTIVITY WILL BE SCATTERED AND IS
MOST LIKELY TO IMPACT KSUX. LEFT A TEMPO MENTION OF BRIEF MVFR
VISIBILITY IN THE THUNDERSTORM LATE THIS EVENING. SOME STORMS COULD
POTENTIALLY PRODUCE SQUALL WIND CONDITIONS THIS EVENING INTO THE
EARLY MORNING.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
SHORT TERM...
LONG TERM...JM
AVIATION...
AREA FORECAST DISCUSSION
NWS HOUSTON/GALVESTON TX
103 PM CDT WED AUG 21 2013
.AVIATION...
QUIET SO FAR THIS MORNING WITH LIGHT NE TO E FLOW BUT THIS WILL
BECOME MORE SOUTHEAST WITH HEATING TODAY. SHOWERS HAVE BEEN FEW
AND FAR BETWEEN BUT SOME AREAS OF LOCALIZED CONVERGENCE EAST OF
GALVESTON AROUND SMITH POINT AND FROM AROUND LBX TO PSX. EXPECTING
A SLOW INLAND PENETRATION GIVEN THE LL FLOW THROUGH MID AFTERNOON
THEN SHOULD ACCELERATE BUT MAY OUTRUN THE AVAILABLE MOISTURE AND
WEAKEN INLAND DURING THE AFTERNOON. FOR NOW WILL ONLY MENTION
VCSH/VCTS FOR HOU TERMINALS SOUTHWARD EARLY THIS AFTERNOON. SKIES
SHOULD CLEAR OUT TONIGHT BUT MOISTURE INCREASES FURTHER TOMORROW
TO AROUND 2-2.1" AND THE S/W OVER LA AND LA GULF WATERS SHOULD
MOVE WEST AND GIVE THE AREA SOME BROAD LIFT AND COMBINED WITH THE
PW AND SEABREEZE EXPECT GREATER COVERAGE SCATTERED TOMORROW
STARTING NEAR THE COAST AROUND 08-09Z AND SPREADING WEST AND NORTH
THROUGH THE MORNING HOURS. WILL CARRY VCSH/VCTS FOR IAH SOUTHWARD
AND PROB30 FOR HOU SOUTHWARD. THIS MAY BE NEEDED FOR IAH/CXO AFTER
18Z BUT WILL LIKELY WAIT UNTIL THE 00Z PACKAGE TO ADD IT THAT FAR
NORTH.
45
&&
.PREV DISCUSSION... /ISSUED 958 AM CDT WED AUG 21 2013/
UPDATE...
MORNING FORECAST UPDATE.
DISCUSSION...
LATEST RADAR IMAGERY SHOWS A FEW SHOWERS WAY OUT IN THE GULF BUT
REALLY NOT MUCH ACTIVITY THIS MORNING COMPARED TO YESTERDAY.
MOISTURE LEVELS SEEM TO BE LOWER WITH PRECIP WATER VALUES AROUND
1.8-1.9 INCHES PER GOES SOUNDER IMAGERY. SFC ANALYSIS SHOWS A WEAK
RIDGE AXIS FROM HIGH PRESSURE OVER THE SE U.S. WILL DECREASE POPS
THIS MORNING TO 20 PERCENT AS SHOULD GET A FEW SHOWERS LATER THIS
MORNING WITH DAY TIME HEATING. WILL KEEP 30 POPS FOR THE AFTERNOON
AS HEATING INCREASES MORE. LATEST 12Z HRRR KEEPS MOST OF THE
CONVECTION TO SW OF HOUSTON BUT CONVECTION DOES DISSIPATE AROUND
23Z SIMILAR TO YESTERDAY. THINK THAT WILL BE MORE LIKELY THE CASE.
UPDATED FORECAST HAS BEEN ISSUED.
39/45
&&
.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL) 98 74 96 75 95 / 20 10 40 30 20
HOUSTON (IAH) 95 73 94 75 94 / 30 10 40 20 30
GALVESTON (GLS) 90 79 88 80 88 / 30 20 40 20 30
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&
$$
DISCUSSION...33
AVIATION/MARINE...45
AREA FORECAST DISCUSSION
NWS AMARILLO TX
1238 PM CDT WED AUG 21 2013
.AVIATION...
VFR CONDITIONS WILL PREVAIL THROUGH THE NEXT 24 HOURS WITH GENERALLY
SOUTH WINDS CONTINUING.
SIMPSON
&&
.PREV DISCUSSION... /ISSUED 615 AM CDT WED AUG 21 2013/
AVIATION...
FOR THE 12Z TAFS...VFR CONDITIONS SHOULD PREVAIL THROUGH THE TAF
PERIOD...WITH ONLY FEW TO SCT HIGH CLOUDS. ANY TSRA SHOULD STAY IN
THE HIGHER TERRAIN OF NM AND CO...WELL WEST OF THE TAF SITES. EXPECT
WINDS GENERALLY SOUTHERLY WITH A DIURNAL TREND ON SPEEDS.
JOHNSON
PREV DISCUSSION... /ISSUED 331 AM CDT WED AUG 21 2013/
DISCUSSION...
UPPER HIGH WILL PREVAIL ACROSS THE PANHANDLES AND THE CENTRAL PLAINS
STATES THROUGH THE END OF THE WEEK AND EARLY THIS WEEKEND...THEN THE
UPPER HIGH SHIFTS EASTWARD OVER THE MID MISSISSIPPI RIVER VALLEY AREA
BY LATE IN THE WEEKEND THROUGH THE MIDDLE OF NEXT WEEK. SUBSIDENCE
WILL DOMINATE THE FORECAST AREA THROUGH EARLY AND MID NEXT WEEK
KEEPING THE PANHANDLES DRY WITH ABOVE NORMAL TEMPERATURES. ALTHOUGH A
ROGUE THUNDERSTORM DEVELOPED ACROSS THE SOUTHWEST TEXAS PANHANDLE THE
LAST COUPLE OF DAYS DURING THE LATE AFTERNOON AND EARLY EVENING
HOURS...THE NMM MODEL DID FORECAST THIS SCENARIO ON TUESDAY.
HOWEVER...THE NMM...ARW...THE NAM...GFS...RUC AND ECMWF ALONG WITH
THE TTU-WRF AND THE HRRR ARE ALL CONVECTION-FREE AND WILL CONTINUE
WITH A DRY FORECAST. NO MAJOR CHANGES TO THE PREVIOUS GRIDS AND
FORECAST.
SCHNEIDER
FIRE WEATHER...
NO ELEVATED OR CRITICAL FIRE WEATHER CONDITIONS ARE EXPECTED ACROSS
THE TEXAS AND OKLAHOMA PANHANDLES THROUGH THE MIDDLE OF NEXT WEEK.
EITHER THE MINIMUM AFTERNOON RELATIVE HUMIDITIES WILL REMAIN AT OR
ABOVE 20 PERCENT...OR THE 20 FOOT WIND SPEEDS WILL REMAIN AT OR BELOW
15 TO 20 MPH.
SCHNEIDER
&&
.AMA WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
OK...NONE.
&&
$$
09/08
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
156 PM EDT WED AUG 21 2013
.SYNOPSIS...
AN UPPER LEVEL LOW WILL MOVE FROM THE OHIO VALLEY TO THE MID
ATLANTIC COAST BY LATE THURSDAY. A COLD FRONT WILL MOVE FROM THE
GREAT LAKES ON THURSDAY INTO THE CAROLINAS BY SATURDAY. DRIER AND
COOLER HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT FOR THE
WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 1240 PM EDT WEDNESDAY...
NOT A LOT OF CHANGES FOR THE AFTERNOON UPDATE. WE WILL STILL HAVE
THE GENERAL FORECAST IN PLACE FOR A GREATER CONCENTRATION OF
SHOWERS AND STORMS THIS AFTERNOON ACROSS THE MOUNTAINS WITH LESSER
COVERAGE IN THE EAST UNTIL TOWARD EVENING. WHAT HAS BEEN ADJUSTED
IS THE PRECIPITATION CHANCES IN THE VERY NEAR FUTURE. HAVE RAMPED
PRECIPITATION CHANCES TO CATEGORICAL ACROSS THE FAR SOUTHWEST PART
OF THE FORECAST AREA WHERE SHOWERS AND STORMS WERE ONGOING.
CURRENT TRACK AND SPEED WOULD SUGGEST THIS AREA WILL REMAIN A HOT
SPOT FOR AT LEAST THE NEXT TWO TO THREE HOURS.
ANOTHER ADJUSTMENT INCLUDES THE FORECAST HIGH TEMPERATURES.
READINGS IN THE EAST LOOK TO EXCEED THE EARLIER FORECAST SO HAVE
INCREASED VALUES BY A FEW DEGREES IN ANTICIPATION OF HIGHER HIGH
TEMPERATURES. NO OTHER SIGNIFICANT CHANGES.
AS OF 950 AM EDT WEDNESDAY...
THE FORECAST THIS MORNING FOR THE MOST PART HAS BEEN ON TRACK. THE
GREATEST CONCENTRATION OF PRECIPITATION HAS BEEN ALONG AND SOUTH
OF THE NC/VA BORDER. OTHER ISOLATED SHOWERS HAVE BEEN NEAR THE
I-64 CORRIDOR OF WV/VA...HOWEVER...MUCH OF THIS DISSIPATED AROUND
930 AM. CURRENTLY...THE NEAR TERM MODEL OF CHOICE IS THE RNK WFR-
ARW. IS HOURLY DEPICTION OF THE PRECIPITATION IN NC HAS MATCHED
VERY WELL THIS MORNING. HAVE USED ITS OUTPUT AS A ROUGH
EXTRAPOLATION OF WHAT IS TO COME THROUGH THE REMAINDER OF THE
MORNING AND THIS AFTERNOON. ITS OUTPUT IS ALSO COMPARABLE TO THE
ONGOING FORECAST FOR TODAY.
WE ARE ANTICIPATING THE WEAK ACTIVITY NEAR THE NC/VA BORDER TO
DECREASE IN SIGNIFICANCE HEADING INTO THE AFTERNOON...WITH OUR
FOCUS SHIFTING TO THE WESTERN HALF OF THE REGION. HERE SHOWERS AND
THUNDERSTORMS ARE EXPECTED TO DEVELOP AND TO COVER 50 TO 70
PERCENT OF THIS REGION THROUGHOUT THE AFTERNOON...WITH COVERAGE
INCREASING ITS GREATEST BETWEEN ROUGHLY 100 PM AND 200 PM.
ELSEWHERE...COVERAGE IS EXPECTED TO BE ISOLATED TO SCATTERED
THROUGH THE MID-AFTERNOON...AND THEN LOOK FOR A SHIFT EASTWARD OF
THE MAIN AREA OF PRECIPITATION THAT WILL IMPACT AREAS PRIMARILY
ALONG AND NORTH OF THE ROUTE 460 CORRIDOR OF VA.
AS OF 410 AM EDT WEDNESDAY...
WHEN I FIRST JOINED THE NATIONAL WEATHER SERVICE MY ELDERS TOLD ME
A CODE THEY WOULD USE WHEN THERE WAS LOW CONFIDENCE IN THE
FORECAST. THEY WOULD APPEND A NUMBER 9 TO THE END OF THEIR NAME
WHEN ISSUING THE FORECAST. TODAY IS DEFINITELY A 9 DAY.
MODELS SHOWING SIGNIFICANT DIFFERENCES IN THE TIMING AND LOCATION
OF PRECIPITATION FOR TODAY AND TONIGHT. HOWEVER...THE LATEST RAP
AND HRRR GUIDANCE HAVE SOMEWHAT OF A REASONABLE TREND WITH THE
PRECIPITATION MOVING NORTH FROM THE CAROLINAS AND THE 00Z LOCAL
WRF SHOWED DECENT CONTINUITY WITH THE PRECIPITATION IN WEST
VIRGINIA.
EXPECT A MAJORITY OF THE PRECIPITATION FROM THE CAROLINAS TO MOVE
THROUGH THE FORECAST AREA THIS MORNING. BY LATE THIS
AFTERNOON...THE UPPER LOW TRACKING WEST OUT OF THE OHIO VALLEY
SHOULD BE TRIGGERING SHOWERS AND THUNDERSTORMS IN THE MOUNTAINS.
AS THIS FEATURE MOVES EAST THIS EVENING...THE COUNTY WARNING AREA
WILL BE IN A FAVORABLE QUADRANT OF THE ASSOCIATED UPPER JET. NET
RESULT IS NOT MUCH CHANGE IN THE PROBABILITY OF PRECIPITATION FOR
TODAY AND TONIGHT.
BUFKIT SHOWED WINDS THROUGH MID LAYERS OF THE ATMOSPHERE LESS THAN
15 KNOTS...WHICH SUGGESTS INDIVIDUAL STORMS THAT DEVELOP MAY BE
MOVING SLOWLY. FLASH FLOOD GUIDANCE IS LESS THAN 2 INCHES FROM THE
NEW RIVER VALLEY AND SOUTHEAST WEST VIRGINIA INTO NORTHWEST NORTH
CAROLINA. WITH PRECIPITABLE WATER VALUES AROUND 1.5 INCHES TODAY
AND TONIGHT HEAVY RAIN REMAINS A THREAT.
TRENDED TOWARD GRIDDED LAMP GUIDANCE FOR MAXIMUM TEMPERATURES
TODAY...BUT WITH CLOUDS AND PRECIPITATION THIS MORNING...WITH BE
COUNTING ON SOME BREAKS IN THE CLOUDS FOR THIS AFTERNOON.
MILD SURFACE DEW POINTS AND CLOUD COVER WILL LIMIT COOLING
OVERNIGHT. LEANED TOWARD WARMER NUMBERS FOR OVERNIGHT LOWS.
&&
.SHORT TERM /THURSDAY THROUGH SATURDAY/...
AS OF 330 AM EDT WEDNESDAY...
UPPER LOW CENTER AROUND LAFAYETTE INDIANA THIS MORNING WILL TRAVEL
EAST AND REACH THE EAST COAST ON FRIDAY. THIS LOW CENTER MOVES INTO
THE ATLANTIC BY SATURDAY...ALLOWING A SURFACE HIGH TO PUSH INTO THE
REGION JUST IN TIME FOR THE WEEKEND.
SHOWERS AND THUNDERSTORMS WILL DEVELOP AHEAD OF THE COLD FRONT ON
THURSDAY. KEPT THE ISOLATED TO SCATTERED POPS IN FOR THURSDAY. WENT
WITH HIGH TEMPERATURES CLOSER TO THE COOLER ADJMET WITH READINGS
FROM THE MID 70S IN THE MOUNTAINS TO THE MID 80S IN THE SOUTHEAST.
A COLD FRONT WILL CROSS THE REGION THURSDAY NIGHT INTO FRIDAY.
PLACED THE HIGHEST POPS (GOOD CHANCE TO LIKELY) IN THE WEST THURSDAY
NIGHT INTO FRIDAY. LEANED TOWARDS THE WARMER MOS LOW TEMPERATURES
THURSDAY NIGHT WITH READINGS FROM THE LOWER 60S IN THE MOUNTAINS TO
NEAR 70 DEGREES IN THE PIEDMONT. HIGHS ON FRIDAY WILL VARY FROM THE
LOWER 70S IN THE WEST TO THE UPPER 80S IN THE SOUTHEAST. LOWERED
POPS FRIDAY NIGHT FROM NORTH TO SOUTH. USED THE ENSEMBLE LOWS FRIDAY
NIGHT WITH VALUES FROM LOWER 50S IN THE NORTHWEST TO THE LOWER 60S
IN THE SOUTH. UNDER THE UPPER RIDGE...PLEASANT SATURDAY ON TAP WITH
SUNSHINE AND HIGH TEMPERATURES GENERALLY FROM MID 70S TO THE LOWER
80S.
&&
.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
AS OF 115 PM EDT TUESDAY...
DURING SUNDAY...FLOW AROUND THE SURFACE HIGH WILL BRING SOUTHEAST
FLOW INTO THE SOUTHWEST PART OF THE REGION. THIS MAY YIELD SOME
ISOLATED UPSLOPE SHOWERS. A COLD FRONT IS PROGGED TO TRY TO MAKE ITS
WAY INTO THE NORTHERN PART OF THE AREA MONDAY NIGHT INTO TUESDAY.
THERE MAY BE SOME ISOLATED SHOWERS IN ADVANCE OF THIS FRONT THAT
REACH NORTHERN PARTS OF THE AREA LATE IN THE DAY MONDAY. SEVERAL
WEAK SHORTWAVES WILL DROP SOUTH IN THE NORTHWEST FLOW ALOFT ACROSS
NORTHERN PORTIONS OF OUR REGION TUESDAY INTO WEDNESDAY.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AS OF 150 PM EDT WEDNESDAY...
THE ASSOCIATED DYNAMICS WITH THE APPROACH OF A SHORTWAVE TROUGH
IS ENTERING THE REGION CURRENTLY. SURFACE TEMPERATURES CONTINUE TO
WARM AND HELP THE LOW LEVELS BECOME UNSTABLE. THE RESULT IS
DEVELOPMENT OF SHOWERS AND STORMS ACROSS THE AREA. THE GREATEST
CONCENTRATION THROUGH THE AFTERNOON HOURS IS EXPECTED TO BE ACROSS
THE MOUNTAINS. COVERAGE IS EXPECTED TO TRANSLATE EASTWARD HEADING
INTO THE EVENING HOURS. MOST AREAS WILL CONTINUE TO EXPERIENCE VFR
CONDITIONS THE REMAINDER OF THE AFTERNOON AND THROUGH THE EARLY
EVENING. THE EXCEPTION WILL BE THOSE LOCALIZED AREAS WITH MODERATE
TO HEAVE SHRA/TSRA. HERE BRIEF PERIODS OF IFR/MVFR CONDITIONS ARE
LIKELY ALONG WITH VARIABLE AND GUSTY WIND CONDITIONS.
THROUGH THE OVERNIGHT HOURS...CEILINGS WILL TREND TO A MIX OF
MVFR AND LOW END VFR CONDITIONS BY 06Z/2AM WITH A MIX OF IFR/MVFR
CEILINGS BY 12Z/8AM. VISIBILITIES WILL TREND TO IFR IN THOSE
LOCATIONS THAT RECEIVED RAIN TODAY AND EARLY THIS EVENING ALSO
SHELTERED VALLEYS ALSO WILL TREND TOWARD HAVING FOG.
THE TROUGH AXIS PASSES AROUND 12Z/8AM THURSDAY. THIS WILL ALLOW
WINDS TO VEER MORE WESTERLY AND INCREASE IN SPEED. ANY SUB-VFR
CONDITIONS SHOULD IMPROVE FAIRLY RAPIDLY TO VFR.
A BROADER LONGWAVE TROUGH AND ASSOCIATED COLD FRONT WILL PROGRESS
ACROSS THE EASTERN U.S. THURSDAY NIGHT INTO FRIDAY. LOOK FOR A
RETURN OF ORGANIZED SHOWERS AND STORMS IN ADVANCE...DURING...AND
IMMEDIATELY BEHIND ITS PASSAGE. SUB-VFR CONDITIONS WILL ACCOMPANY
THE HEAVIER SHRA/TSRA.
DRIER HIGH PRESSURE BUILDS IN TO THE AREA FOR THE WEEKEND. OTHER
THAN SOME LATE NIGHT AND EARLY MORNING MOUNTAIN AND RIVER VALLEY
FOG...VFR CONDITIONS ARE EXPECTED INTO MONDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...AMS
NEAR TERM...AMS/DS
SHORT TERM...KK
LONG TERM...DS/KK
AVIATION...DS
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
1243 PM EDT WED AUG 21 2013
.SYNOPSIS...
AN UPPER LEVEL LOW WILL MOVE FROM THE OHIO VALLEY TO THE MID
ATLANTIC COAST BY LATE THURSDAY. A COLD FRONT WILL MOVE FROM THE
GREAT LAKES ON THURSDAY INTO THE CAROLINAS BY SATURDAY. DRIER AND
COOLER HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT FOR THE
WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 1240 PM EDT WEDNESDAY...
NOT A LOT OF CHANGES FOR THE AFTERNOON UPDATE. WE WILL STILL HAVE
THE GENERAL FORECAST IN PLACE FOR A GREATER CONCENTRATION OF
SHOWERS AND STORMS THIS AFTERNOON ACROSS THE MOUNTAINS WITH LESSER
COVERAGE IN THE EAST UNTIL TOWARD EVENING. WHAT HAS BEEN ADJUSTED
IS THE PRECIPITATION CHANCES IN THE VERY NEAR FUTURE. HAVE RAMPED
PRECIPITATION CHANCES TO CATEGORICAL ACROSS THE FAR SOUTHWEST PART
OF THE FORECAST AREA WHERE SHOWERS AND STORMS WERE ONGOING.
CURRENT TRACK AND SPEED WOULD SUGGEST THIS AREA WILL REMAIN A HOT
SPOT FOR AT LEAST THE NEXT TWO TO THREE HOURS.
ANOTHER ADJUSTMENT INCLUDES THE FORECAST HIGH TEMPERATURES.
READINGS IN THE EAST LOOK TO EXCEED THE EARLIER FORECAST SO HAVE
INCREASED VALUES BY A FEW DEGREES IN ANTICIPATION OF HIGHER HIGH
TEMPERATURES. NO OTHER SIGNIFICANT CHANGES.
AS OF 950 AM EDT WEDNESDAY...
THE FORECAST THIS MORNING FOR THE MOST PART HAS BEEN ON TRACK. THE
GREATEST CONCENTRATION OF PRECIPITATION HAS BEEN ALONG AND SOUTH
OF THE NC/VA BORDER. OTHER ISOLATED SHOWERS HAVE BEEN NEAR THE
I-64 CORRIDOR OF WV/VA...HOWEVER...MUCH OF THIS DISSIPATED AROUND
930 AM. CURRENTLY...THE NEAR TERM MODEL OF CHOICE IS THE RNK WFR-
ARW. IS HOURLY DEPICTION OF THE PRECIPITATION IN NC HAS MATCHED
VERY WELL THIS MORNING. HAVE USED ITS OUTPUT AS A ROUGH
EXTRAPOLATION OF WHAT IS TO COME THROUGH THE REMAINDER OF THE
MORNING AND THIS AFTERNOON. ITS OUTPUT IS ALSO COMPARABLE TO THE
ONGOING FORECAST FOR TODAY.
WE ARE ANTICIPATING THE WEAK ACTIVITY NEAR THE NC/VA BORDER TO
DECREASE IN SIGNIFICANCE HEADING INTO THE AFTERNOON...WITH OUR
FOCUS SHIFTING TO THE WESTERN HALF OF THE REGION. HERE SHOWERS AND
THUNDERSTORMS ARE EXPECTED TO DEVELOP AND TO COVER 50 TO 70
PERCENT OF THIS REGION THROUGHOUT THE AFTERNOON...WITH COVERAGE
INCREASING ITS GREATEST BETWEEN ROUGHLY 100 PM AND 200 PM.
ELSEWHERE...COVERAGE IS EXPECTED TO BE ISOLATED TO SCATTERED
THROUGH THE MID-AFTERNOON...AND THEN LOOK FOR A SHIFT EASTWARD OF
THE MAIN AREA OF PRECIPITATION THAT WILL IMPACT AREAS PRIMARILY
ALONG AND NORTH OF THE ROUTE 460 CORRIDOR OF VA.
AS OF 410 AM EDT WEDNESDAY...
WHEN I FIRST JOINED THE NATIONAL WEATHER SERVICE MY ELDERS TOLD ME
A CODE THEY WOULD USE WHEN THERE WAS LOW CONFIDENCE IN THE
FORECAST. THEY WOULD APPEND A NUMBER 9 TO THE END OF THEIR NAME
WHEN ISSUING THE FORECAST. TODAY IS DEFINITELY A 9 DAY.
MODELS SHOWING SIGNIFICANT DIFFERENCES IN THE TIMING AND LOCATION
OF PRECIPITATION FOR TODAY AND TONIGHT. HOWEVER...THE LATEST RAP
AND HRRR GUIDANCE HAVE SOMEWHAT OF A REASONABLE TREND WITH THE
PRECIPITATION MOVING NORTH FROM THE CAROLINAS AND THE 00Z LOCAL
WRF SHOWED DECENT CONTINUITY WITH THE PRECIPITATION IN WEST
VIRGINIA.
EXPECT A MAJORITY OF THE PRECIPITATION FROM THE CAROLINAS TO MOVE
THROUGH THE FORECAST AREA THIS MORNING. BY LATE THIS
AFTERNOON...THE UPPER LOW TRACKING WEST OUT OF THE OHIO VALLEY
SHOULD BE TRIGGERING SHOWERS AND THUNDERSTORMS IN THE MOUNTAINS.
AS THIS FEATURE MOVES EAST THIS EVENING...THE COUNTY WARNING AREA
WILL BE IN A FAVORABLE QUADRANT OF THE ASSOCIATED UPPER JET. NET
RESULT IS NOT MUCH CHANGE IN THE PROBABILITY OF PRECIPITATION FOR
TODAY AND TONIGHT.
BUFKIT SHOWED WINDS THROUGH MID LAYERS OF THE ATMOSPHERE LESS THAN
15 KNOTS...WHICH SUGGESTS INDIVIDUAL STORMS THAT DEVELOP MAY BE
MOVING SLOWLY. FLASH FLOOD GUIDANCE IS LESS THAN 2 INCHES FROM THE
NEW RIVER VALLEY AND SOUTHEAST WEST VIRGINIA INTO NORTHWEST NORTH
CAROLINA. WITH PRECIPITABLE WATER VALUES AROUND 1.5 INCHES TODAY
AND TONIGHT HEAVY RAIN REMAINS A THREAT.
TRENDED TOWARD GRIDDED LAMP GUIDANCE FOR MAXIMUM TEMPERATURES
TODAY...BUT WITH CLOUDS AND PRECIPITATION THIS MORNING...WITH BE
COUNTING ON SOME BREAKS IN THE CLOUDS FOR THIS AFTERNOON.
MILD SURFACE DEW POINTS AND CLOUD COVER WILL LIMIT COOLING
OVERNIGHT. LEANED TOWARD WARMER NUMBERS FOR OVERNIGHT LOWS.
&&
.SHORT TERM /THURSDAY THROUGH SATURDAY/...
AS OF 330 AM EDT WEDNESDAY...
UPPER LOW CENTER AROUND LAFAYETTE INDIANA THIS MORNING WILL TRAVEL
EAST AND REACH THE EAST COAST ON FRIDAY. THIS LOW CENTER MOVES INTO
THE ATLANTIC BY SATURDAY...ALLOWING A SURFACE HIGH TO PUSH INTO THE
REGION JUST IN TIME FOR THE WEEKEND.
SHOWERS AND THUNDERSTORMS WILL DEVELOP AHEAD OF THE COLD FRONT ON
THURSDAY. KEPT THE ISOLATED TO SCATTERED POPS IN FOR THURSDAY. WENT
WITH HIGH TEMPERATURES CLOSER TO THE COOLER ADJMET WITH READINGS
FROM THE MID 70S IN THE MOUNTAINS TO THE MID 80S IN THE SOUTHEAST.
A COLD FRONT WILL CROSS THE REGION THURSDAY NIGHT INTO FRIDAY.
PLACED THE HIGHEST POPS (GOOD CHANCE TO LIKELY) IN THE WEST THURSDAY
NIGHT INTO FRIDAY. LEANED TOWARDS THE WARMER MOS LOW TEMPERATURES
THURSDAY NIGHT WITH READINGS FROM THE LOWER 60S IN THE MOUNTAINS TO
NEAR 70 DEGREES IN THE PIEDMONT. HIGHS ON FRIDAY WILL VARY FROM THE
LOWER 70S IN THE WEST TO THE UPPER 80S IN THE SOUTHEAST. LOWERED
POPS FRIDAY NIGHT FROM NORTH TO SOUTH. USED THE ENSEMBLE LOWS FRIDAY
NIGHT WITH VALUES FROM LOWER 50S IN THE NORTHWEST TO THE LOWER 60S
IN THE SOUTH. UNDER THE UPPER RIDGE...PLEASANT SATURDAY ON TAP WITH
SUNSHINE AND HIGH TEMPERATURES GENERALLY FROM MID 70S TO THE LOWER
80S.
&&
.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
AS OF 115 PM EDT TUESDAY...
DURING SUNDAY...FLOW AROUND THE SURFACE HIGH WILL BRING SOUTHEAST
FLOW INTO THE SOUTHWEST PART OF THE REGION. THIS MAY YIELD SOME
ISOLATED UPSLOPE SHOWERS. A COLD FRONT IS PROGGED TO TRY TO MAKE ITS
WAY INTO THE NORTHERN PART OF THE AREA MONDAY NIGHT INTO TUESDAY.
THERE MAY BE SOME ISOLATED SHOWERS IN ADVANCE OF THIS FRONT THAT
REACH NORTHERN PARTS OF THE AREA LATE IN THE DAY MONDAY. SEVERAL
WEAK SHORTWAVES WILL DROP SOUTH IN THE NORTHWEST FLOW ALOFT ACROSS
NORTHERN PORTIONS OF OUR REGION TUESDAY INTO WEDNESDAY.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AS OF 135 AM EDT WEDNESDAY...
AREAS OF IFR CIG/VIS WILL DISSIPATE THIS MORNING BY 14Z. LEADING
EDGE OF PRECIPITATION COMING OUT OF THE SOUTHWEST WAS JUST
REACHING THE VIRGINIA/NORTH CAROLINA BORDER AT 7AM. EXPECT
EXPANDING COVERAGE OF SHOWERS AND ISOLATED THUNDERSTORMS THROUGH
16Z EAST OF THE BLUE RIDGE. BEST CHANCE OF SHOWERS AND
THUNDERSTORMS IN THE MOUNTAINS WILL BE AFTER 18Z/2PM BUT WILL
CONTINUE THROUGH THE EVENING.
PATTERN WILL TRANSITION TO MORE TYPICAL OF MID AUGUST THURSDAY...WITH
SOUTHWEST FLOW AND DIURNALLY DRIVEN SHOWERS AND THUNDERSTORMS.
SCATTERED LOW CLOUDS WILL LINGER DURING THE MORNING IN AREAS...
RESULTING IN A MIXTURE OF MVFR AND VFR CONDITIONS...BEFORE
IMPROVING TO MOSTLY VFR BY EARLY AFTERNOON. PATCHY DENSE FOG
WILL ALSO BE AN ISSUE EACH NIGHT.
A FRONTAL BOUNDARY SHOULD MOVE THROUGH BY FRIDAY...POSSIBLY
PROVIDING BETTER COVERAGE OF SHOWERS AND THUNDERSTORMS. BEHIND
THIS FRONT DRIER AIR AND VFR CONDITIONS ARE EXPECTED SATURDAY AND
SUNDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...AMS
NEAR TERM...AMS/DS
SHORT TERM...KK
LONG TERM...DS/KK
AVIATION...AMS/KM
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
340 PM CDT WED AUG 21 2013
.VERY SHORT TERM...TONIGHT AND THURSDAY.
CONVECTION IS FIRING UP ALONG THE SURFACE COLD FRONT FROM NORTHWEST
WI THROUGH THE TWIN CITIES AREA. THIS LINES UP WELL WITH THE NCEP
4KM WRF-NMM SIMULATED RADAR REFLECTIVITY. THAT MODEL BRINGS A LINE
OF CONVECTION SOUTHEAST INTO THE MKX FORECAST AREA 01Z-02Z...THEN
ALLOWS IT TO WEAKEN. IT SHOWS A SLIGHTLY STRONGER AREA OF CONVECTION
CONTINUING IN SOUTHEAST WI BUT MUCH LESS CONVECTION IN SOUTH CENTRAL
WI. SOME OF THE OTHER MODELS ARE SHOWING THIS SPLIT AS WELL..SO IT
WILL BE SOMETHING TO WATCH OUT FOR. MEANWHILE...THE 18Z HRRR MODEL
RUN SHOWS THAT CONVECTION IN NORTHWEST WI...BRINGS IT EASTWARD AS A
BLOB...AND NEVER EXTENDS ANY CONVECTION DOWN INTO SOUTHERN WI AT
ALL.
MOST CONVECTION WILL LIKELY BE ALONG THE IL BORDER BY 06Z AND ENDING
SHORTLY THEREAFTER. MID LEVEL DRY AIR MOVES IN QUICKLY BEHIND THE
FRONT AND ANY SEVERE THREAT WILL BE GONE BY 06Z.
AS FOR SEVERE POTENTIAL...THE BEST RISK OF SEVERE WEATHER WILL BE
OVER NORTH CENTRAL WI. THIS IS WHERE THE SPC STORM SCALE ENSEMBLE OF
OPPORTUNITY BULLSEYES THE HIGHEST 24-HOUR PROBABILITY OF HIGH
UPDRAFT HELICITY AND HIGH UPDRAFT SPEED. THIS IS ALSO WHERE THERE IS
A SEVERE THUNDERSTORM WATCH IN EFFECT RIGHT NOW.
SPC HAS THE SLIGHT RISK INCLUDING MADISON AND WEST BEND. THIS SEEMS
REASONABLE BASED ON MODEL FORECAST REFLECTIVITIES. ANY STRONGER AND
ORGANIZED STORMS THAT DEVELOP OVER CENTRAL WI COULD SWEEP SOUTH AND
SOUTHEAST WITH A DAMAGING STRAIGHT-LINE WIND THREAT INTO THE
NORTHERN MKX FORECAST AREA. WITH CAPE VALUES EXCEEDING 3000 J/KG AND
MODERATE 0-3 AND 0-6KM SHEAR...LARGE HAIL WILL BE POSSIBLE AS WELL.
AS STORMS MAKE IT FURTHER INTO SOUTH CENTRAL AND SOUTHEAST WI LATER
THIS EVENING...SURFACE BASED CAPE AND BULK SHEAR VALUES DECREASE
GIVEN THE TIME OF DAY AND THE SURFACE TROUGH LOSING DEFINITION. ALSO
THE 850MB LEADING EDGE OF THE LOW LEVEL JET AND WARM AIR ADVECTION
WILL BE SHIFTING EAST OVER LAKE MICHIGAN.
THERE IS ANOTHER SHORTWAVE THAT WILL TRACK ALONG THE 850MB
BAROCLINIC ZONE THROUGH NORTHERN IOWA AND EVENTUALLY INTO NORTHERN
IL LATE TONIGHT/THU MORNING. CONVECTION WITH THIS FEATURE MAY CLIP
SOUTHERN WI SO LEFT A SMALL CHANCE FOR THUNDER THROUGH THU MORNING.
SUNSHINE IS EXPECTED LATER THURSDAY...ALLOWING MAX TEMPS IN THE
UPPER 70S AND LOWER 80S WITH A NORTH TO NORTHEAST BREEZE.
.SHORT TERM...THURSDAY NIGHT THROUGH SATURDAY.
A QUIET PERIOD IS ANTICIPATED AS HIGH PRESSURE AT THE SURFACE AND
ALOFT CONTINUES TO BUILD INTO THE WESTERN GREAT LAKES TO CENTRAL MS
VALLEY. LIGHT WINDS BELOW SHALLOW INVERSION SHOULD ALLOW PATCHY FOG
TO DEVELOP IN THE WI RIVER VLY LATER THU NIGHT. BOUNDARY LAYER
MIXING JUST ABOVE INVERSION SHOULD PREVENT SIGNIFICANT FOG ELSEWHERE
HOWEVER. WARMER AIR STARTS TO RETURN ON SATURDAY AS LOW LEVEL WINDS
TURN MORE SOUTH. ANY CONVECTION ASSOCIATED WITH PUSH OF WARM AIR
AND WEAK SHORT WAVE IS EXPECTED TO REMAIN TO THE NORTH OF CWA ON
SAT.
.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY.
MEDIUM RANGE GUIDANCE IN GOOD AGREEMENT ON EXPANSIVE HIGH PRESSURE
RIDGE OVER SOUTHERN CONUS EXPANDING NORTHWARD AND ENVELOPING
SOUTHERN WI ON SATURDAY AND PERSISTING THROUGH THE FIRST PORTION OF
NEXT WEEK. 500H HEIGHTS INCREASE TO AROUND 591 METERS WHILE 85H
TEMPS INCREASE TO 19 TO 22C. HENCE A VERY WARM PERIOD IS EXPECTED
WITH DAYTIME READINGS MOSTLY IN THE UPPER 80S TO MIDDLE 90S.
DAYTIME HEAT INDICIES MAY REACH 95 TO 100 SEVERAL DAYS.
500H GFS 5 DAY ANOMOLIES SHOW HEIGHTS 50-70 METERS ABOVE NORMAL
THROUGH THE END OF AUGUST...WITH MORE ZONAL FLOW SETTLING OVER
NORTHERN CONUS FOR START OF SEPT.
STILL A POTENTIAL FOR SEVERAL MID-LEVEL SHORT WAVES BREAKING THROUGH
CAPPING INVERSION OVER NORTHERN/CENTRAL WI...WITH CONVECTION
CARRYING SWD INTO PORTIONS OF SRN WI FROM SAT NIGHT INTO TUE. MOST
OF THE PERIOD WILL REMAIN DRY AND WARM HOWEVER.
&&
.AVIATION /00Z TAFS/...THUNDERSTORMS ARE LIKELY ALONG A COLD FRONT
MOVING SOUTHEAST ACROSS CENTRAL AND SOUTHERN WI THIS EVENING. SOME
IFR CONDITIONS IN STORMS. STORMS WILL BE MORE WIDESPREAD EARLY THIS
EVENING AND THEN BECOME MORE SCATTERED LATER IN THE EVENING. SEVERE
THUNDERSTORMS POSSIBLE NORTH OF A LINE FROM PLATTEVILLE TO MADISON
TO WEST BEND. DAMAGING WINDS AND SMALL HAIL ARE THE THREATS. SEVERE
POTENTIAL DIMINISHES AFTER 06Z AND PRECIP CHANCES DIMINISH SHORTLY
THEREAFTER AS WELL.
THERE COULD BE A PERIOD OF MVFR CIGS AND VSBYS JUST BEHIND FRONT
OVERNIGHT. DRIER AIR WITH WINDS OUT OF THE NORTHEAST WILL SETTLE
INTO SOUTHERN WI BY EARLY THU AFTERNOON.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&
.CONFIDENCE...
TONIGHT AND THURSDAY...MEDIUM TO HIGH.
THURSDAY NIGHT THROUGH SATURDAY...HIGH.
SATURDAY NIGHT THROUGH WEDNESDAY...MEDIUM.
$$
VERY SHORT TERM/AVIATION...MRC
SHORT TERM/LONG TERM...MBK
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
323 PM CDT WED AUG 21 2013
.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 323 PM CDT WED AUG 21 2013
MAIN FOCUS WILL BE ON THE FRONTAL PASSAGE TONIGHT AND THE
ASSOCIATED RAIN CHANCES.
COLD FRONT EXTENDS FROM NORTHERN WISCONSIN INTO NORTHEAST NEBRASKA
AT MID AFTERNOON. REGIONAL RADARS SHOW CONVECTIVE ACTIVITY ALONG
THE FRONT FROM NORTHERN WISCONSIN ACROSS MINNESOTA.
WATER VAPOR SATELLITE SHOWS THE MAIN SHORT WAVE TROUGH IS ALONG
THE CANADIAN BORDER MOVING INTO ONTARIO WITH A SECONDARY WAVE OVER
CENTRAL MINNESOTA. THE BEST PV ADVECTION IN THE 500-300 MB LAYER
WILL STAY TO THE NORTH OF THE AREA TONIGHT BUT THE EXPECTATION IS
THAT THE WAVE OVER MINNESOTA WILL PROVIDE JUST ENOUGH FORCING TO
HELP MAINTAIN THE CONVECTION ALONG THE FRONT AS IT COMES THROUGH.
ML CAPES AHEAD OF THE FRONT CURRENTLY ARE AROUND 3000 J/KG AND
WHILE THESE WILL DECREASE THROUGH THE EVENING WITH THE LOSS OF
HEATING...THE 21.18Z NAM INDICATES THESE WILL STAY AT OR ABOVE
1500 J/KG THROUGH THE EVENING AHEAD OF THE FRONT. THE BEST 0-6KM
SHEAR WILL REMAIN NORTH OF THE AREA CLOSER TO THE MAIN SHORT WAVE
TROUGH. HOWEVER...THE 0-3KM SHEAR WILL BE AROUND 30 KNOTS AND WILL
BE MORE THAN SUFFICIENT TO SUPPORT SOME SEVERE STORMS THROUGH THE
EVENING. LARGE HAIL AND DAMAGING WINDS STILL LOOK TO BE THE MAIN
THREATS. WILL BE INTERESTING TO SEE HOW THE CURRENT ACTIVITY
SOUTH OF THE TWIN CITIES EVOLVES THROUGH THE REMAINDER OF THE
AFTERNOON. THE 21.18Z RAP BUFKIT SOUNDINGS SUGGEST THE CAP IN
PLACE BETWEEN 750 AND 800 MB AT KRST WILL HOLD TIGHT UNTIL THE
FRONT MOVES THROUGH. IF THIS HAPPENS...THE ACTIVITY TO THE WEST
SHOULD DIMINISH AS IT MOVES IN AND THIS IS WHAT SEVERAL OF THE
SHORT RANGE MESO MODELS SUGGESTS. BASED ON THIS...HAVE TRIMMED
BACK THE RAIN CHANCES HEADING THROUGH THE EVENING ACROSS THE
WESTERN SECTIONS OF THE FORECAST AREA. FARTHER EAST...THE CAP IS
WEAKER AND IS EXPECTED TO ERODE AS THE FRONT MOVES IN...SO HAVE
MAINTAINED THE 60 TO 80 PERCENT CHANCES EAST OF THE MISSISSIPPI RIVER.
ALL THE MODELS ALSO SUGGEST THE FRONT AND CONVECTION WILL MOVE
THROUGH PRETTY QUICK THIS EVENING TO THE POINT THAT MOST IF NOT
ALL OF THE FORECAST AREA SHOULD BE DRY BY 06Z. THUS SPED UP THE
FORECAST TO REFLECT THIS FASTER TIMING WITH JUST SOME 20 TO 40
PERCENT RAIN CHANCES ACROSS THE SOUTH FOR AFTER MIDNIGHT. HAVE
HELD ON TO SOME SMALL RAIN CHANCES ACROSS THE SOUTH FOR THURSDAY
MORNING. ALL THE MODELS INDICATE A CONVECTIVE COMPLEX WILL DEVELOP
ACROSS NEBRASKA THIS EVENING AND THEN MOVE EAST ALONG THE FRONT
TOWARD THE AREA OVERNIGHT WITH SOME SUGGESTIONS THAT THE NORTHERN
PART OF THE COMPLEX COULD SLIDE ACROSS THE SOUTHERN PARTS OF THE
AREA. OTHERWISE FOR THURSDAY...HIGH PRESSURE WILL MOVE IN FROM THE
NORTH WITH MUCH DRIER AIR SPREADING IN. NAM BUFKIT SOUNDING ACROSS
THE NORTHERN SECTIONS SHOW GOOD SUBSIDENCE OCCURRING AND WITH LOTS
OF DRY ALOFT TO MIX DOWN...DEW POINTS ARE EXPECTED TO DROP INTO
THE 40S FOR THE AFTERNOON. THIS HIGH WILL REMAIN THE DOMINANT
FEATURE FOR THE REMAINDER OF THE SHORT TERM HELPING TO KEEP
TEMPERATURES CLOSER TO NORMAL THROUGH FRIDAY WITH HIGHS IN THE
UPPER 70S TO LOWER 80S.
.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 323 PM CDT WED AUG 21 2013
CONSIDERABLE UNCERTAINTY IN THE EXTENDED IN REGARDS TO THE RAIN
CHANCES. THE UPPER LEVEL RIDGE WILL BE ANCHORED OVER THE CENTRAL
PART OF THE COUNTRY WITH ALL THE MODELS SHOWING SHORT WAVE TROUGHS
EXPECTED TO RIDE UP THE BACK SIDE AND OVER THE TOP OF THE RIDGE.
AT THE SURFACE...THE EXPECTATION IS THAT A WEAK SURFACE BOUNDARY
WILL APPROACH FROM THE WEST SATURDAY BUT STALL OUT AND BECOME
NEARLY STATIONARY BEFORE IT REACHES THE AREA. IT SHOULD THEN
WAFFLE NORTH/SOUTH AS SHORT WAVE TROUGHS MOVE AROUND THE RIDGE AND
CAUSE ROUNDS OF CONVECTION TO FORM. THE UNCERTAINTY COMES IN WHERE
THESE COMPLEXES WILL BE AND WHETHER THEY WILL IMPACT THE NORTHERN
PARTS OF THE FORECAST AREA OR NOT. AFTER THE INITIAL SHORT WAVE
TROUGH GOES BY SATURDAY WILL GENERALLY LIMIT THE RAIN CHANCES TO
THE I94 CORRIDOR FOR THE REMAINDER OF THE EXTENDED PERIOD AS THIS
AREA WILL BE CLOSEST TO THE FRONT.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1150 AM CDT WED AUG 21 2013
A COLD FRONT STRETCHING FROM WESTERN LAKE SUPERIOR THROUGH
KMSP/KFSD LATE THIS MORNING WILL CONTINUE TO TRACK SOUTHEAST
THROUGH THIS AFTERNOON. SHOWERS AND STORMS ARE EXPECTED TO FORM
ALONG THIS FRONT WITH THE HIGHEST LIKELIHOOD EAST OF THE
MISSISSIPPI RIVER. EXPECTING TSRA IN THE VICINITY OF KRST/KLSE
AERODROMES WITH PERHAPS A BRIEF REDUCTION INTO IFR BETWEEN 21-24Z
TIME FRAME. THE FRONT AND ASSOCIATED STORMS ARE THEN EXPECTED TO
SLIP SOUTHEAST OF THE AREA AFTER MIDNIGHT. LINGERING MID-
LEVEL/VFR CLOUDS WILL LIKELY BE SEEN DURING THE OVERNIGHT HOURS
INTO THURSDAY MORNING AS THE FRONT HANGS UP ACROSS NORTHERN IL
THROUGH CENTRAL IA. OTHERWISE...HIGH PRESSURE BUILDING IN ON
THURSDAY SHOULD KEEP RAIN CHANCES SOUTH OF THE AREA.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...04
LONG TERM...04
AVIATION...DAS
FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE
.SHORT TERM...TONIGHT AND THURSDAY
ISSUED AT 206 PM CDT WED AUG 21 2013
LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A STRONG COLD
FRONT MOVING OVER THE FAR WESTERN UPPER PENINSULA AND NORTHWEST
WISCONSIN EARLY THIS AFTERNOON. MOISTURE CONVERGENCE ALONG THE
FRONT LOOKS GOOD...AND ML CAPES ARE BUILDING BETWEEN 2K-3K J/KG
AHEAD OF THE BOUNDARY. RETURNS ON RADAR ARE PICKING UP ALONG THE
FRONT AS INHIBITION ERODES BELOW 50 J/KG. WITH 0-6KM BULK SHEAR
VALUES AROUND 25-30 KTS...CONDITIONS REMAIN CONDUCIVE FOR SEVERE
THUNDERSTORMS TO DEVELOP LATER THIS AFTERNOON. THE NSSL WRF SEEMS
TO BE DOING THE BEST OUT OF THE MESOMODELS...AND SHOWS CONVECTION
RAMPING UP IN A LINEAR FASHION BETWEEN 19-21Z. BY THE END OF THIS
PERIOD...CONVECTION WILL BE MOVING INTO N-C WISCONSIN BEFORE
PROGRESSING INTO CENTRAL AND NORTHEAST WISCONSIN BY 00Z. STILL
LOOKING AT MULTI-CELLS AND SMALL BOWING SEGMENTS AS THE STORM
MODE...WHICH WILL BE CAPABLE OF PRODUCING DAMAGING WIND GUSTS AND
LARGE HAIL. ANOTHER WRINKLE IS THE WEAK LITTLE SHORTWAVE OVER
SOUTHERN MINNESOTA. THE RUC TAKES THIS FEATURE INTO SW WISCONSIN
THIS EVENING...AND NOT SURE HOW MUCH THIS WILL IMPACT THUNDERSTORMS
ALONG THE FRONT. SEVERE WEATHER IS THE OBVIOUS FORECAST CONCERN.
TONIGHT...SHORTWAVE TROUGH MOVING ACROSS ONTARIO WILL PUSH A COLD
FRONT SOUTHEAST ACROSS CENTRAL AND NORTHEAST WISCONSIN THIS
EVENING. SOUTH SOUTHWEST FLOW AHEAD OF THE FRONT WITH PWATS UPWARDS
OF 1.75 INCHES WILL PREVENT TEMPS FROM FALLING TOO FAST THIS
EVENING...WHICH SHOULD PROLONG THE SEVERE THREAT UNTIL THE FRONT
CLEARS THE AREA. BECAUSE INSTABILITY WILL BE DECREASING...THE LARGE
HAIL THREAT WILL DIMINISH AS WELL THROUGH THE EVENING. BUT THINK
THERE IS ENOUGH POTENTIAL FOR LARGE HAIL AND DAMAGING WINDS TO REACH
EAST-CENTRAL AND NORTHEAST WISCONSIN. PRECIP WILL BE EXITING
EAST-CENTRAL EARLY OVERNIGHT AS MUCH DRIER AIR WILL FILTER SOUTH
BEHIND THE FRONT. TEMPS WILL BE A LITTLE SLOWER TO COOL OFF...BUT
LOWS SHOULD STILL FALL INTO THE LOWER OR MIDDLE 50S NORTH...BUT HANG
IN THE MID 60S SOUTH.
THURSDAY...THE COLD FRONT WILL MOVE TO THE SOUTHERN GREAT LAKES BY
THE START OF THE PERIOD WHILE CANADIAN HIGH PRESSURE WILL BE
BUILDING SOUTHEAST FROM THE NORTHERN PLAINS. THIS AIRMASS WILL BE
COOLER AND SIGNIFICANTLY LESS HUMID THAN THE ONE IT REPLACED. UNDER
PLENTY OF SUN...HIGH TEMPS WILL REACH FROM THE MID 70S NORTH TO THE
LOW 80S SOUTH.
.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 206 PM CDT WED AUG 21 2013
PATTERN TO BECOME RATHER AMPLIFIED AS MOVE THROUGH THIS PERIOD AS
UPPER RIDGE BUILDS OVER THE CENTRAL US...INTO WESTERN LAKES.
MODELS HAVE GOOD CONTINUITY IN BIG PICTURE...BUT TEND TO DIFFER IN
CONVECTIVE DETAILS SUN ONWARD. MAIN ISSUE WILL BE HEAT LATER
PERIODS. ILL-DEFINED WARM FRONT EXPECTED TO LIFT NORTH
INTO/THROUGH STATE SUN. 850 MB TEMPS EXPECTED TO WARM SAT ONWARD
HITTING 20C EARLY IN WORK WEEK. IF MODELS SOUNDINGS
CORRECT...WOULD MIX UP TO THAT LEVEL YIELDING TEMPS AROUND 90 NEXT
MON THROUGH WED. QUESTION IS EFFECTS OF CLOUDS AND PCPN. LIKELY
TO BE ON EDGE OF CAP WITH CONVECTION NEAR OR OVER REGION. HAVE
TRENDED HIGHER POPS OVER NORTHERN WI WHERE ECMWF LINGERS FRONT.
HAVE USED BEST PERFORMING BLEND FOR TEMPS...BUMPING THEM UP A
DEGREE TO LESSEN CLIMO BIAS.
EARLY PERIODS/THU NIGHT INTO FRI NIGHT/PLEASANT WITH COOLER HIGH
PRESSURE AT THE SURFACE OVER REGION. CLEAR SKIES AND DRY
CONDITIONS TO LEAD TO COOLER NIGHTS AND MILD DAYS. HAVE SLOWED
APPROACH OF PCPN SAT GIVEN MODEL TRENDS.
&&
.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1210 PM CDT WED AUG 21 2013
MAINLY VFR WEATHER EXPECTED TODAY UNTIL A COLD FRONT
ARRIVES IN NORTH CENTRAL WISCONSIN DURING THE AFTERNOON HOURS AND
MOVES ACROSS THE EASTERN PART OF THE STATE BY EARLY EVENING. IT WILL
BE ACCOMPANIED BY SHOWERS AND THUNDERSTORMS WITH GUSTY WINDS AND
BRIEF IFR CEILINGS AND VISIBILITIES. THE FRONT WILL EXIT TONIGHT
WITH CLEARING EXPECTED BY THURSDAY MORNING. GOOD FLYING WEATHER IS
EXPECTED THURSDAY THROUGH FRIDAY.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......TE
AVIATION.......MPC
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
1210 PM CDT WED AUG 21 2013
UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE
.UPDATE...
ISSUED AT 1038 AM CDT WED AUG 21 2013
NO BIG CHANGES TO THE FORECAST FOR THE REST OF TODAY. A STRONG
COLD FRONT EXTENDS FROM WESTERN LAKE SUPERIOR TO CENTRAL
MINNESOTA. THE FRONT HAS BEEN MOSTLY QUIET SO FAR THIS MORNING
OUTSIDE OF A FEW BLIPS ON THE RADAR. SKIES ARE MOSTLY CLEAR TO
PARTLY CLOUDY AHEAD OF THE FRONT...WHICH SHOULD ALLOW FOR GOOD
HEATING. TEMPS ARE LAGGING BEHIND THE PREVIOUS FORECAST SO DROPPED
THEM A DEGREE. LOOKING AT THE MODELS THIS MORNING...THE NAM AND SREF HAVE
SPED UP THE TIMING OF THE FRONT...HAVING IT REACH NORTHEAST
WISCONSIN AND THE FOX VALLEY LATE IN THE AFTERNOON. THE RUC IS NOT
TOO DIFFERENT...SO THIS MAY BE POSSIBLE. REGARDLESS...ML CAPES
WILL REACH 3K J/KG IF A PARCEL CAN REACH 88/68. WITH TEMPS LAGGING
A LITTLE BIT...2K-3K J/KG SEEMS REASONABLE. SUFFICIENT 0-6KM BULK
SHEAR OF 25-30 KTS WILL BE GOOD ENOUGH TO PRODUCE STORMS
CONTAINING LARGE HAIL AND DAMAGING WINDS. TRIED TO FOLLOW THE NSSL
WRF FOR THE CONVECTIVE EVOLUTION FOR THIS FORECAST. CONVECTIVE
INITIATION LOOKS TO OCCUR AROUND THE 19-20Z TIME PERIOD OVER
NORTHWEST WISCONSIN. STORMS ARE THEN PROJECTED TO REACH THE FOX
VALLEY EARLY THIS EVENING.
&&
.SHORT TERM...TODAY...TONIGHT...AND THURSDAY
ISSUED AT 407 AM CDT WED AUG 21 2013
A SMALL AREA OF SHOWERS AND THUNDERSTORMS WILL MOVE
ACROSS PARTS OF THE FOX VALLEY EARLY THIS MORNING IN AN AREA OF
MID LEVEL WARM ADVECTION AND CONVERGENCE. IT SHOULD EXIT THE AREA
BY SUNRISE OR SHORTLY THEREAFTER. VERY WARM AND HUMID WEATHER
EXPECTED TODAY BEFORE THE ARRIVAL OF A COLD FRONT DURING THE LATE
AFTERNOON AND EVENING HOURS. HEAT INDICES WILL RISE INTO THE 90S
WITH TEMPERATURES IN THE MIDDLE 80S TO LOW 90S.
THE POTENTIAL FOR SEVERE THUNDERSTORMS CERTAINLY EXISTS THIS
AFTERNOON AND EVENING. SIGNIFICANT INSTABILITY...UPPER
DIFFLUENCE...LOW LEVEL WARM ADVECTION AND MOISTURE CONVERGENCE
SHOULD COMBINE TO CREATE AN ENVIRONMENT FAVORABLE FOR STRONG TO
SEVERE STORMS. MID LEVEL WINDS ARE NOT TOO IMPRESSIVE AND
TEMPERATURES ALOFT ARE NOT VERY COLD...BUT INSTABILITY WILL BE
SUBSTANTIAL AND SHOULD HELP PRODUCE STORMS WITH STRONG UPDRAFTS.
THE DAY ONE SEVERE THUNDERSTORM OUTLOOK LOOKS VERY REASONABLE AND
FITS WELL WITH CURRENT THINKING AND HISTORICAL ANALOGS FOR SIMILAR
EVENTS.
THE COLD FRONT WILL EXIT TONIGHT AND PRECIPITATION WILL END FROM
WEST TO EAST. THE AIR BEHIND THE FRONT IS MORE DRY THAN COLD SO
EXPECT LOWS TONIGHT TO BE NEAR OR JUST ABOVE NORMAL BUT WITH MUCH
MORE COMFORTABLE DEW POINTS. TOMORROW SHOULD BE SUNNY AND
SEASONABLE TEMPERATURES AND LOW HUMIDITY.
.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
ISSUED AT 407 AM CDT WED AUG 21 2013
SOMEWHAT OF AN AMPLIFIED FLOW TO TAKE SHAPE INTO EARLY NEXT WEEK
WITH UPR TROFS ALONG THE WEST COAST/NE CONUS AND A BROAD UPR RDG
OVER THE CNTRL/E-CNTRL CONUS. THIS RDG TO INTENSIFY BY THE WEEKEND
WITH BOTH TEMPS AND DEW POINTS GOING ABOVE CLIMATOLOGICAL NORMS
FOR LATE AUGUST. MAIN FCST ISSUE REMAINS LOCATION OF CONVECTIVE
COMPLEXES RIDING THE RIM OF THIS UPR RDG AND WHETHER ANY BACKDOOR
CDFNTS MAY REACH NE WI.
HI PRES IS EXPECTED TO STRETCH FROM ERN ONTARIO SWWD THRU THE
GREAT LAKES BY THU NGT SETTING UP MOSTLY CLEAR SKIES...LIGHT WINDS
AND A DRY ATMOSPHERE WITH DEW POINTS IN THE 40S TO LWR 50S. NEAR
IDEAL RADIATIONAL CONDITIONS WL ALLOW FOR TEMPS TO QUICKLY FALL
THU NGT WITH A FEW LOCATIONS OVER THE NORTH FLIRTING WITH THE 40
DEG MARK. MAY NEED TO TWEAK VALUES DOWN A COUPLE OF DEGS FROM THE
PREVIOUS FCST.
PLEASANT CONDITIONS WL CONT INTO FRI AS THE CENTER OF THIS SFC RDG
SLOWLY SLIDES TO THE EAST...BUT REMAINS THE DOMINANT FEATURE FOR
NE WI. EVEN WITH A COOL START TO THE DAY...MAINLY SUNNY SKIES
COUPLED WITH A DRY AIR MASS IN PLACE...WL STILL ALLOW TEMPS TO
MAKE A PRETTY GOOD JUMP DURING THE DAY. LOOK FOR MAX TEMPS TO
APPROACH THE 80 DEG MARK FOR INLAND AREAS...WHILE LAKESHORE AREAS
TO ONLY REACH THE MID 70S AS THE LAKEBREEZE DEVELOPS AND MOVES
INLAND.
AS THE SFC RDG HEADS INTO THE ERN GREAT LAKES FRI NGT...RETURN
FLOW BEGINS OVER WI AS WINDS JUST ABOVE THE SFC TURN S-SW AND
INCREASE TO AROUND 20 KTS. PRIMARY LOW-LEVEL JET AIMED OVER THE
NRN PLAINS/UPR MS VALLEY WHERE ELEVATED CONVECTION IS EXPECTED.
ANOTHER QUIET NGT FOR THE FCST AREA WITH MIN TEMPS NOT AS COLD AND
THE AIR MASS NOT AS DRY AS THU NGT. LOOK FOR MIN TEMPS TO BE IN
THE LWR 50S NORTH/MID 50S ELSEWHERE.
THE SPRAWLING UPR RDG OVER THE CNTRL CONUS IS PROGGED TO EXPAND
NWD TOWARD THE UPR MS VALLEY/GREAT LAKES REGIONS STARTING THIS
WEEKEND. AS THIS OCCURS...AN INCREASE IN BOTH TEMPS AND DEW POINTS
WL TAKE PLACE AS WELL AS THE POTENTIAL FOR A WRMFNT TO LIFT NORTH
TOWARD/INTO WI. IN ADDITION...A PIECE OF ENERGY IS FCST TO RIDE
THE FRINGE OF THIS UPR RDG ON SAT. WHILE BETTER INSTABILITY AND
DEEPER MOISTUREWL BE TO OUR WEST...CANNOT RULE OUT A CONVECTIVE
COMPLEX MOVING INTO PARTS OF NE WI BY SAT AFTERNOON. MAY NEED TO
RAISE POPS A BIT AS A RESULT. ONCE THE WRMFNT LIFTS TO OUR NORTH
AND THE IMPULSE (ENERGY) SHIFTS TO OUR EAST SAT NGT...PCPN CHCS
LOOK MINIMAL HEADED INTO SUNDAY AS THE UPR RDG REMAINS IN PLACE
AND THE ATMOSPHERE BECOMES CAPPED. 8H TEMPS PUSHING +20C COULD
EASILY SEND MAX TEMPS WELL INTO THE 80S WITH DEW POINTS CLIMBING
INTO THE 60S.
STILL HAVE QUESTIONS AS TO HOW FAR NORTH THIS WRMFNT CAN GET
SUNDAY NGT INTO MON AS THIS FEATURE WL BE THE PRIMARY FOCUSING
MECHANISM FOR ADDITIONAL SHWRS/TSTMS. SOME MDLS KEEP THIS FNT TO
OUR NORTH...THUS ADVERTISING A DRY FCST. HOWEVER...OTHER MDLS
APPEAR TO SHOW CONVECTION HELPING TO SHOVE THIS BOUNDARY A BIT
SOUTH AND LEAVE MUCH OF THE FCT AREA VULNERABLE TO MORE PCPN. TOO
MUCH UNCERTAINTY HERE...THUS HAVE FAVORED THE CONSENUS SOLUTION
WHICH KEEPS CHC POPS IN THE FCST ALONG WITH VERY WARM/MUGGY
CONDITIONS. UNCERTAINTY CARRIES OVER INTO TUE AS THE LONG-TERM
MDLS DIFFER ON HOW LONG THE UPR RDG WL BE ABLE TO MAINTAIN ITSELF.
THERE IS POTENTIAL FOR ANOTHER COMPLEX TO DEVELOP ON THE EDGE OF
THIS UPR RDG...THUS A CONTINUED CHC POP WL ALSO BE NEEDED FOR TUE.
&&
.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1210 PM CDT WED AUG 21 2013
MAINLY VFR WEATHER EXPECTED TODAY UNTIL A COLD FRONT
ARRIVES IN NORTH CENTRAL WISCONSIN DURING THE AFTERNOON HOURS AND
MOVES ACROSS THE EASTERN PART OF THE STATE BY EARLY EVENING. IT WILL
BE ACCOMPANIED BY SHOWERS AND THUNDERSTORMS WITH GUSTY WINDS AND
BRIEF IFR CEILINGS AND VISIBILITIES. THE FRONT WILL EXIT TONIGHT
WITH CLEARING EXPECTED BY THURSDAY MORNING. GOOD FLYING WEATHER IS
EXPECTED THURSDAY THROUGH FRIDAY.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE.........MPC
SHORT TERM.....RDM
LONG TERM......KALLAS
AVIATION.......MPC