Forecast Discussions mentioning any of
"HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 09/05/12
AREA FORECAST DISCUSSION
NWS PHOENIX AZ
300 PM MST MON SEP 3 2012
.SYNOPSIS...
HIGH PRESSURE ALOFT WILL REMAIN CENTERED OVER OR NEAR NEW MEXICO
THROUGH MUCH OF THE UPCOMING WEEK. VERY MOIST AND MODERATELY
UNSTABLE AIR WILL OVERSPREAD THE AREA...WHILE WEAK WEATHER
DISTURBANCES PERIODICALLY MOVE WEST ACROSS NORTHERN MEXICO. AS A
RESULT...EXPECT A RATHER ACTIVE PERIOD OF WEATHER THIS WEEK...WITH
AN ABOVE NORMAL CHANCE FOR MAINLY LATE AFTERNOON AND EVENING
THUNDERSTORMS. LOCALLY HEAVY RAINFALL AND STRONG WINDS ARE LIKELY
WITH THE MORE INTENSE STORMS.
&&
.DISCUSSION...
LATEST RAP ANALYZED A DIFFUSE TROUGH EXTENDING FROM SOUTHERN NM TO
HERMOSILLO MEXICO...THOUGH THIS IS DIFFICULT TO IDENTIFY ON WV
IMAGERY. STRONG STORMS HAVE DEVELOPED IN THE DIFLUENT REGION BETWEEN
THIS TROUGH AND AN ANTICYCLONE CENTERED NEAR THE WHITE MOUNTAINS.
FURTHER NORTH ACROSS THE MOGOLLON RIM...OROGRAPHICALLY-INDUCED
SHOWERS AND THUNDERSTORMS HAVE ALSO FORMED BUT CONTINUE TO DRIFT
NORTHEASTWARD TOWARDS THE CO PLATEAU WITHIN A 10 KT MEAN LAYER FLOW.
EARLIER MOISTURE SURGE ALONG THE GOC AND ACROSS YUMA AND THE
IMPERIAL VALLEY YIELDED HEAT INDICES BETWEEN 110 AND 115
DEGREES...BUT HAVE SINCE LOWERED AS THE ATMOSPHERE MIXES OUT.
LATEST MESOANALYSIS SHOWS MODERATELY STRONG CONVECTIVE INHIBITION
ACROSS MUCH OF THE FORECAST AREA...LARGELY DUE TO A RIDGE AND THE
ASSOCIATED WARM/DRY AIR IN THE 800-700 MB LAYER. MODEL SOUNDINGS
INDICATE THAT THIS LAYER WILL MOISTEN ACROSS WESTERN AZ THIS
AFTERNOON...WHICH WILL HELP TO ERODE THE CIN AND INITIATE ISOLATED
CONVECTION. NMM-B BASED WRF FROM UNIV OF AZ APPEARS TO HAVE THE BEST
HANDLE ON THE SHORT-TERM EVOLUTION AND SUGGESTS STORMS WILL FIRE
ACROSS YUMA AND LA PAZ COUNTIES THIS AFTERNOON. ISOLATED ACTIVITY IN
THE IMPERIAL VALLEY ALSO CANNOT BE RULED OUT...GIVEN THE
SOUTHWESTERLY STEERING FLOW AND PRESENCE OF CB/TCU ON VISIBLE
SATELLITE ALONG THE BAJA SPINE. ACROSS THE PHOENIX METRO AREA...THE
MAIN IMPACT APPEARS TO BE THE POTENTIAL BLOWING DUST FROM
THUNDERSTORMS TO THE SOUTH...THOUGH POPS REMAIN 5 TO 10 PERCENT
ABOVE THE CLIMATOLOGICAL AVERAGE.
&&
.PREVIOUS DISCUSSION...
IN THE SHORT TERM (MONDAY-WEDNESDAY)...EXPECT A DAY TO DAY INCREASE
IN STORM ACTIVITY...ESPECIALLY OVER AZ PORTION OF THE CWA. VERY
MOIST AIR MASS CURRENTLY EXISTS OVER NORTHWEST MEXICO. SYNOPTIC
PATTERN...WITH RATHER STRONG TROUGH OF LOW PRESSURE MOVING EAST
ACROSS SOUTH-CENTRAL CANADA WHILE A TROPICAL DISTURBANCE (NOW TS
JOHN) MOVES WEST JUST OFF THE SOUTHERN END OF BAJA
CALIFORNIA...CERTAINLY SUPPORTS A MOISTURE INCREASE OVER OUR
AREA...AND THE GFS/ECMWF/NAM CERTAINLY AGREE THE ATMOSPHERE WILL
MOISTEN SIGNIFICANTLY DURING THE NEXT 36 HRS.
WITH ATMOSPHERIC MOISTENING CONTINUING ON TUESDAY (ANOMALOUSLY HIGH
PRECIPITABLE WATER NEAR 2" BY THEN) AND MORE DIFLUENT UPPER LEVEL
FLOW OVER SOUTHEAST AZ BY TUESDAY AFTN...PRECIP CHANCE WILL BE A BIT
GREATER TUESDAY EVENING... ESPECIALLY OVER SOUTH-CENTRAL AZ. VERY
MOIST AND MODERATELY UNSTABLE ATMOSPHERE REMAINS IN PLACE ON
WEDNESDAY...AND PRECIP CHANCES WILL BE ENHANCED AS A WEAK WEATHER
DISTURBANCE MOVES WEST ACROSS SONORA. WITH SUCH HIGH ATMOSPHERIC
MOISTURE CONTENT...DECENT CAPE...AND WEAK STEERING FLOW...LOCALLY
HEAVY RAINFALL CAN BE EXPECTED...THOUGH STRONG/DAMAGING WINDS WILL
ALSO BE POSSIBLE.
IN THE EXTENDED PERIOD(THURSDAY-SUNDAY)...NUMERICAL MODELS INDICATE
ATMOSPHERE WILL REMAIN ANOMALOUSLY MOIST AND MODERATELY UNSTABLE
WHILE WEAK WEATHER DISTURBANCE CONTINUE TO AFFECT THE DESERT
SOUTHWEST. WENT WITH SLIGHT CHANCE POPS DURING THE LATE AFTN/EVENING
HOURS FOR SOUTH-CENTRAL AZ EACH DAY...BUT WOULD NOT BE SURPRISED IF
PRECIP CHANCES WILL ACTUALLY BE SOMEWHAT HIGHER THAN CURRENTLY
PORTRAYED.
&&
.AVIATION...
SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...AND KSDL...
THROUGH 06Z TUE...INCREASING CLOUDS BECOMING SCT-BKN AOA 14 THSD MSL
LATE IN THE AFTERNOON AND EVENING...WITH POSSIBLE ISOLATED
SHWRS/TSTMS. WEST WIND 5 TO 15 KNOTS...BUT VARIABLE AND GUSTY WITH
CONVECTIVE OUTFLOW BOUNDARIES IF NEARBY CONVECTION DEVELOPS. FROM
06Z TUE TO 19Z TUE...SCT-BKN CLDS AOA 14 THSD MSL. LIGHT WIND UNDER
10 KNOTS.
SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH...
THROUGH 06Z TUE...INCREASING CLOUDS BECOMING SCT-BKN AOA 14 THSD MSL
LATE IN THE AFTERNOON AND EVENING...WITH ISOLATED SHWRS/TSTMS. SOUTH
WIND 5 TO 15 KNOTS...BUT VARIABLE AND GUSTY WITH CONVECTIVE OUTFLOW
BOUNDARIES IF NEARBY CONVECTION DEVELOPS. FROM 06Z TUE TO 19Z
TUE...SCT-BKN CLDS AOA 16 THSD MSL. SOUTH WIND 5 TO 15 KNOTS.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
THURSDAY THROUGH MONDAY...
SIGNIFICANT MONSOON MOISTURE WILL COVER THE REGION. A SLIGHT CHANCE
OF AFTERNOON AND EVENING THUNDERSTORMS WILL CONTINUE MAINLY OVER
SOUTH CENTRAL ARIZONA...PARTICULARLY MOUNTAINS. MINIMUM RELATIVE
HUMIDITIES WILL RANGE FROM 20 TO 25 PERCENT...EXCEPT 15 TO 20
PERCENT IN IN SOUTHEAST CALIFORNIA. RELATIVELY LIGHT WINDS ARE
EXPECTED.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&
$$
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DISCUSSION...HIRSCH
PREVIOUS DISCUSSION...DG
AVIATION...VASQUEZ
FIRE WEATHER...VASQUEZ
AREA FORECAST DISCUSSION
NWS TUCSON AZ
930 AM MST MON SEP 3 2012
.SYNOPSIS...THERE WILL BE PLENTY OF MOISTURE AROUND FOR SCATTERED
AFTERNOON AND EVENING THUNDERSTORMS AGAIN TODAY...MAINLY SOUTH AND
WEST OF TUCSON. DEEPER MOISTURE WILL MOVE ACROSS THE AREA TUESDAY
AND WEDNESDAY FOR AN UPSWING IN THUNDERSTORM ACTIVITY.
&&
.DISCUSSION...UPPER AIR PLOTS THIS MORNING PLACED MID LEVEL HIGH
OVER W-CNTRL NEW MEXICO WHILE FURTHER UP AROUND 300 MB THE HIGH WAS
OVER NE SONORA MEXICO. THUS WE HAVE WEAK E-SE MID LEVEL FLOW AND A
BIT STRONGER SW FLOW AT 300 MB. PRECIPITABLE WATER VALUES ARE UP A
BIT FROM 24 HOURS AGO...ESPECIALLY OVER THE EASTERN AREAS AND THEY
HAVE INCREASED A LOT OVER SONORA MEXICO AS DEEPER TROPICAL MOISTURE
CONTINUES TO PUSH NORTH ACROSS THE GULF OF CALIFORNIA AND SONORA
MEXICO WHERE OVER 2 INCHES OF PW RESIDES FROM HERMOSILLO S. VALUES
ACROSS SOUTHERN ARIZONA THIS MORNING RANGED FROM 1.30" ALONG AZ/NM
BORDER TO 1.60" IN WESTERN PIMA COUNTY. NO DISCERNIBLE FEATURE ALOFT
CAN BE SEEN ON WATER VAPOR IMAGERY BUT BOTH 12Z NAM/GFS DO SHOW A
WEAK INVERTED TROF OVER CENTRAL SONORA...WHICH THEY BOTH MOVE NORTH
TO THE INTERNATIONAL BORDER THIS AFTERNOON. THE WRF VERSION OF THESE
MODELS ALONG WITH THE LATEST HRRR MODEL RUN ARE INDICATING THAT
SANTA CRUZ AND SOUTHERN COCHISE COUNTY ALONG WITH SOUTHERN PORTIONS
OF THE TOHONO OODHAM NATION WILL BE THE FOCUS FOR STORMS THIS
AFTERNOON INTO THIS EVENING. STILL LOOKING AT WET MICROBURSTS
PRODUCING LOCALLY HEAVY RAIN WHERE RAINFALL AMOUNTS COULD BE IN THE
1-2" RANGE. WITH THIS IN MIND MADE SOME SLIGHT ADJUSTMENTS TO
POP/QPF GRIDS FOR THESE AREAS WITH UPDATE DUE OUT SHORTLY. WILL ALSO
HIGHLIGHT ENHANCED CHANCES FOR FLASH FLOODING FOR THE ABOVE
MENTIONED AREAS IN THE HAZARDOUS WEATHER OUTLOOK. AT THIS TIME DO
NOT BELIEVE AREAL COVERAGE WILL BE WIDESPREAD ENOUGH TO WARRANT FF
WATCH. HIGHS TODAY WILL BE A BIT COOLER VERSUS SUNDAY.
TROPICAL MOISTURE WILL CONTINUE TO PUSH NORTH INTO ARIZONA TUESDAY
AND WEDNESDAY AS TROPICAL STORM JOHN MOVES TO THE WNW INTO COOLER
WATERS WELL OFF BAJA COAST. AS WE HAVE BEEN ADVERTISING FOR A COUPLE
OF DAYS NOW...BOTH TUESDAY AND WEDNESDAY LOOK PRETTY ACTIVE. DUE TO
THE ADDED MOISTURE AND CLOUD COVER...HIGHS TUESDAY AND WEDNESDAY
WILL BE BELOW NORMAL.
&&
.AVIATION...MAIN AREA OF CONCERN FOR SHOWERS AND THUNDERSTORMS THIS
AFTERNOON AND EVENING WILL BE SOUTH AND WEST OF KTUS WHERE THEY WILL
BE MORE NUMEROUS.
SURFACE WIND GENERALLY LESS THAN 10 KTS...EXCEPT FOR GUSTS TO 45 KTS
NEAR SCTD TSRA/SHRA BTWN 03/19Z AND 04/04Z...ESPECIALLY FROM S AND W
OF KTUS. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
&&
.FIRE WEATHER...EXPECT SCATTERED MAINLY AFTERNOON AND EVENING
SHOWERS AND THUNDERSTORMS THROUGH THE WEEK. ERRATIC AND GUSTY WINDS
CAN BE EXPECTED NEAR ANY THUNDERSTORMS THAT DEVELOP.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
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AREA FORECAST DISCUSSION
NWS GRAND JUNCTION CO
948 PM MDT TUE SEP 4 2012
.SHORT TERM...(TODAY THROUGH WEDNESDAY NIGHT)
ISSUED AT 238 PM MDT TUE SEP 4 2012
WATER VAPOR IMAGERY CLEARLY SHOWING MUCH DRIER AIR THAT HAS
FILTERED DOWN FROM THE NORTH OVERNIGHT WITH RH VALUES ACROSS TOP
THIRD OF THE FORECAST AREA IN THE TEENS. PWATS REMAIN NEAR .7 INCH
FOR THE SAN JUANS AND AREAS SOUTH SO SOME LIGHT SHOWERS OR QUICK
POP AND DROP STORM IS NOT OUT OF THE QUESTION THROUGH THE EVENING
HOURS. WATER VAPOR IS ALSO SHOWING SOME SMALL DISTURBANCES MOVING
THROUGH THE MEAN FLOW CAUSING SOME CONVECTION ACROSS ARIZONA AND
CENTRAL UTAH...POSSIBLY REACHING SOUTHEASTERN UTAH IN THE NEXT
HOUR OR TWO. DID INCREASE POPS FOR THAT AREA THROUGH THE EVENING
HOURS AS WELL AS KEEPING CURRENT POPS IN PLACE FOR THE SAN JUANS.
PLENTY OF SUNSHINE TO CONTINUE FOR THE REST OF THE FORECAST AREA
WHICH WILL PERSIST THROUGH REMAINDER OF SHORT TERM.
ANY CONVECTION SHOULD END NEAR SUNSET WITH CLEAR SKIES EXPECTED
OVERNIGHT. TEMPS SHOULD DROP TO PLEASANT CLIMATOLOGICAL NORMS FOR
MOST LOCALES.
NOT MUCH CHANGE WEDNESDAY WITH CHANCES FOR PRECIP CONTINUING TO
DECREASE WITH ONLY VERY ISOLD POPS OVER THE HIGHEST TERRAIN OF THE
SAN JUANS. SUNNY SKIES WILL BE THE RULE WITH TEMPS RUNNING ABOUT 4
TO 6 DEGREES ABOVE NORMAL. OVERNIGHT LOWS WILL STAY NEAR NORMAL.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 238 PM MDT TUE SEP 4 2012
A SHORTWAVE DISTURBANCE IS EXPECTED TO DROP ACROSS ID/MT ON
THURSDAY AND CLIP NE CO BY MIDDAY FRIDAY. AN ASSOCIATED COLD FRONT
SHOULD REACH NE UT/NW CO THU EVENING AND PUSH ACROSS THE REMAINDER
OF THE FORECAST AREA THURSDAY NIGHT. AS THE SHORTWAVE
APPROACHES...MOISTURE IS PULLED IN AHEAD OF IT FROM THE WEST FOR
INCREASING CLOUDS THURSDAY...WITH ISOLATED TO SCATTERED SHOWERS
DEVELOPING BY LATE AFTERNOON INTO EVENING. SOME INITIAL STORMS MAY
BE DRY...BUT MODELS FORECAST PRECIPITABLE WATER VALUES BETWEEN 1/2
TO 3/4 INCH BY THU EVENING...SO EXPECT STORMS TO WET UP.
DRIER AIR WILL BE MOVING IN ON NORTHWEST FLOW BY FRI AFTERNOON AND
CONTINUE THROUGH SATURDAY AS A HIGH PRESSURE RIDGE BUILDS OVER THE
GREAT BASIN. A PACIFIC TROUGH MOVES INLAND LATE THIS WEEKEND PULLING
UP A SLUG OF MOISTURE AHEAD OF IT AND PUSHING THE RIDGE EAST. THIS
SHOULD INCREASE THE CHANCE OF SHOWERS MONDAY AND TUESDAY.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 947 PM MDT TUE SEP 4 2012
VFR CONDITIONS WILL PREVAIL TONIGHT THROUGH NOON WEDNESDAY...AFTER
WHICH ISOLATED MOUNTAIN THUNDERSTORMS WILL PRODUCE BRIEF AND
LOCALIZED MVFR CIGS OVER THE RIDGES. THESE STORMS WILL MOSTLY BE
DRY WITH WIND GUSTS TO 40 MPH POSSIBLE.
&&
.FIRE WEATHER...
ISSUED AT 238 PM MDT TUE SEP 4 2012
WIND GUSTS IN THE 20-25 MPH RANGE ACROSS THE NORTH THIS AFTERNOON
WITH A FEW SITES SHOWING A BIT STRONGER GUSTS. LOCALIZED AREAS
LIKELY TO SEE A BRIEF PERIOD OF CRITICAL RH AND/OR WIND GUSTS BUT
WIDESPREAD CRITICAL CONDITIONS ARE NOT EXPECTED. HIGH-RESOLUTION
HRRR AND RUC13 MODELS SHOW WIND GUSTS DIMINISHING QUICKLY EARLY THIS
EVENING.
NE UT/NW CO SHOULD CONTINUE TO REMAIN ON THE SOUTHERN FRINGE OF THE
STRONGER WINDS THROUGH WEDNESDAY. THURSDAY AFTERNOON MAY SEE A BIT
STRONGER WINDS ACROSS THE NORTH...20-30 MPH GUSTS...AS A SHORTWAVE
AND ASSOCIATED SURFACE COLD FRONT APPROACH FROM THEN NORTH.
HOWEVER...MOISTURE WILL ALSO BE INCREASING WITH AFTERNOON HUMIDITY
EXPECTED TO BOTTOM OUT RIGHT AROUND 15 PERCENT. WITH INCREASING
CLOUDS...WILL CONTINUE TO HOLD OFF ON ANY FIRE WEATHER HIGHLIGHTS
FOR NE UT/NW CO ALTHOUGH ISOLATED AREAS COULD SEE CRITICAL WIND/RH
CONDITIONS DEVELOP FOR A FEW HOURS THURS AFTERNOON. WILL CONTINUE
KEEPING A WATCH ON THIS. ISOLATED TO SCATTERED THUNDERSTORMS MAY BE
DRY INITIALLY THURS AFTERNOON BUT SHOULD WET UP BY THURS EVENING.
THE COLD FRONT SHOULD PUSH THROUGH THURS NIGHT.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.
&&
$$
SHORT TERM...TGR
LONG TERM...JAD
AVIATION...CC
FIRE WEATHER...JAD
AREA FORECAST DISCUSSION
NWS GRAND JUNCTION CO
253 PM MDT MON SEP 3 2012
.SHORT TERM...(TODAY THROUGH TUESDAY NIGHT)
ISSUED AT 252 PM MDT MON SEP 3 2012
JET STREAM REMAINS OVERHEAD WITH STRONGEST JET STREAK HAVING MOVED
WELL EAST OVER SRN MN/NRN IA. CONVECTION CONTINUES TO FAVOR THE
ROAN/TAVAPUTS THIS AFTN IN RESPONSE TO DISTURBANCES MOVING
THROUGH MEAN FLOW AND ALSO FAVORABLE OROGRAPHICS. POT VORT FIELDS
ALSO FAVOR THIS AREA SO EVENTS PLAYING OUT AS EXPECTED. AS HAS
BEEN THE CASE LAST FEW DAYS...BIGGEST CONCERN WILL BE GUSTY
OUTFLOW WINDS REACHING 40 TO 45 MPH AND ALSO SOME SMALL HAIL. DID
EXPECT MORE CONVECTION DOWN SOUTH SINCE AVAILABLE PRECIP TABLE
WATER IS MUCH HIGHER. BELIEVE CONVECTION IS LIMITED FOR TWO
REASONS. FIRST...STEERING FLOW IS ALMOST FROM DUE WEST WHICH IS
NOT THE BEST DIRECTION FOR OROGRAPHICALLY INDUCED CONVECTION.
SECOND...AND MORE IMPORTANTLY...THERE IS NO REAL TRIGGER TO KICK
OFF SOME LIFT LIKE THERE IS UP NORTH.
SO FOR THE REMAINDER OF THE AFTERNOON...SOME MINOR DISCREPANCIES
HAVE CROPPED UP BETWEEN MODELS BUT HRRR IS DOING A REMARKABLE JOB
NAILING DOWN WHERE CONVECTION HAS AND IS OCCURRING. LATEST HRRR
GUIDANCE SUGGESTS SHOWERS AND STORMS WILL DIE DOWN BY 6PM WITH
VERY LITTLE IN THE WAY OF PRECIPITATION AFTER THAT. THIS DOES MAKE
SENSE AS MODELS ALSO CONTINUE TO DRY OUT ATMOSPHERE. FORECAST
FOLLOWS SUIT THOUGH NOT SO DRAMATICALLY WITH CONVECTION ENDING
AROUND SUNSET. CLEAR SKIES WILL BE DOMINANT OVERNIGHT ALLOWING LOW
TEMPS TO BE A BIT COOLER THAN SEEN THE LAST FEW DAYS THOUGH STILL
A DEGREE OR TWO ABOVE NORMAL.
ON TUESDAY ZONAL FLOW SETS UP FROM THE H3 LEVEL TO H7 WHICH
EFFECTIVELY CUTS OFF THE FLOW OF MOISTURE FROM THE SOUTH. THE MUCH
TOUTED DRIER AIR WILL FINALLY ARRIVE IF THE NAM12/GFS40 ARE TO BE
BELIEVED WHICH WILL GREATLY INHIBIT CONVECTION. KEPT POPS AS THEY
WERE WITH SOME VERY ISOLD SHOWERS AND STORMS POSSIBLE OVER SAN
JUANS AND TO SOME EXTENT CENTRAL MOUNTAINS THOUGH TREND IS TO KEEP
LOWERING POP AND QPF AMTS AND COVERAGE. THE REMAINDER OF THE
FORECAST AREA WILL SEE PLENTY OF SUNSHINE WITH SEASONAL
TEMPERATURES EXPECTED. OVERNIGHT...CLEAR SKIES EXPECTED WITH NEAR
NORMAL LOW TEMPERATURES.
.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 252 PM MDT MON SEP 3 2012
SOMEWHAT ACTIVE NORTHERN STREAM THE LAST HALF OF THE WEEK AS
SHORTWAVES ROTATING AROUND A CENTRAL CANADA LOW DROP INTO THE NRN
TIER STATES. FIRST SHORTWAVE MOVES INTO THE UPPER MIDWEST ON
WEDNESDAY... A SECOND DROPS DOWN ACROSS MT WED NIGHT...AND A THIRD
AND STRONGER ONE CLIPS NE CO LATE FRI. A RATHER WEAK WESTERLY UPPER
JET OVERHEAD ON WED STRENGTHENS THU-FRI AS THAT THIRD WAVE
APPROACHES...AND MAY RESULT IN STRONGER SURFACE WINDS ACROSS NE
UT/NW CO. BROAD HIGH PRESSURE DOMINATES THE SOUTHWEST STATES AND
FOUR CORNERS AND WILL BE MAIN INFLUENCE ON SE UT/SW CO. MODELS KEEP
ENOUGH MOISTURE PRESENT FOR ISOLATED TO PERHAPS SCATTERED
THUNDERSTORMS MAINLY OVER THE CENTRAL AND SOUTHERN MTNS THURSDAY.
THE SOUTHWEST UPPER HIGH BUILDS NORTHWEST INTO THE GREAT BASIN FRI
AND SAT AND SHOULD RESULT IN DRIER NW FLOW FOR OUR FORECAST AREA
THIS WEEKEND. MODELS SHOW A PACIFIC TROUGH REACHING THE NORTHWEST
COAST BY MONDAY...SHIFTING THE HIGH EAST AND ALLOWING MONSOONAL
MOISTURE TO RETURN NEXT MONDAY. CONFIDENCE BELOW AVERAGE ON THIS...
HOWEVER...GIVEN MODEL AND RUN-TO-RUN INCONSISTENCIES...SO WILL STAY
CONSERVATIVE WITH POPS FOR MONDAY.
&&
.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 252 PM MDT MON SEP 3 2012
CONVECTION CONTINUES WITH SOME GUSTY WINDS BEING REPORTED ACROSS
THE AREA. KRIL JUST EXPERIENCED A GUST OF 44 MPH FROM A STORM THAT
IS WELL NORTH OF THE AERODROME. THESE GUSTY WINDS CAN BE EXPECTED
OVER THE NEXT FEW HOURS WITH KEGE AND KASE HAVING THE BEST CHANCE
TO SEE THESE WINDS AND A PASSING SHOWER OR THUNDERSTORM. BRIEF
MVFR IS POSSIBLE FOR THOSE TWO SITES THROUGH 9 PM. REMAINING
AERODROMES SHOULD REMAIN VFR FOR THE NEXT 24 HOURS. THE REST OF
THE STORMS AND SHOWERS SHOULD END AROUND SUNSET GIVING WAY TO
CLEAR SKIES THAT WILL PERSIST THROUGH TOMORROW.
&&
.FIRE WEATHER...
ISSUED AT 252 PM MDT MON SEP 3 2012
WIND IN GENERAL LOOKS TO REMAIN JUST BELOW CRITICAL LEVELS ACROSS
DAGGETT COUNTY AND NORTHERN DUCHESNE COUNTY /FWX ZONES 481 AND 485/
IN NE UT AND MOFFAT COUNTY /FWX ZONE 200/ IN NW CO TUESDAY
AFTERNOON. WIND GUSTS 20-25 MPH ARE PROBABLE DURING PEAK HEATING
TUESDAY AFTERNOON. WHILE LOCAL AREAS MAY SEE CRITICAL CONDITIONS
BELOW 8000-9000 FT DUE TO WIND GUSTS AND LOW RH...DO NOT THINK AREAL
COVERAGE OR DURATION IS ENOUGH TO WARRANT A FIRE WEATHER HIGHLIGHT
FOR NE UT/NW CO AT THIS TIME.
SOME CONCERN THAT WIND GUSTS COULD APPROACH/EXCEED CRITICAL LEVELS
ACROSS NE UT/NW CO ON THU AS A DISTURBANCE APPROACHING FROM THE NW
BEGINS TO STRENGTHEN WINDS ALOFT...WHICH COULD THEN MIX DOWN DURING
PEAK HEATING. HOWEVER...IT APPEARS THAT HUMIDITY WILL REMAIN ABOVE
CRITERIA THU AS MODELS CURRENTLY SHOWING SOME INCREASE IN MOISTURE.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.
&&
$$
SHORT TERM...TGR
LONG TERM...JAD
AVIATION...TGR
FIRE WX...JAD
AREA FORECAST DISCUSSION
NWS PUEBLO CO
1129 AM MDT MON SEP 3 2012
.AVIATION...
VFR CONDITIONS EXPECTED NEXT 24H AT ALL 3 TAF SITES...KCOS...KPUB
AND KALS. WINDS WILL BE DIURNALLY DRIVEN AND LIGHT. THERE IS A
VERY SLIGHT CHANCE OF A WEAK -TSRA AT THE 3 TAF SITES THIS
AFTERNOON BUT PROBABILITY OF OCCURRENCE IS TOO LOW TO MENTION IN
TAF PRODUCTS.
&&
.PREV DISCUSSION... /ISSUED 431 AM MDT MON SEP 3 2012/
SHORT TERM...
(TODAY AND TONIGHT)
RADAR IS STILL PICKING UP SOME ECHOES OVR THE FORECAST AREA...BUT
COVERAGE IS SPOTTY. WV SATELLITE IMAGERY SHOWING A PLUME OF
MSTR ACRS THE STATE THIS MORNING. MODELS SHOW DRIER AIR WORKING
INTO THE AREA FROM THE WEST...BUT REMAINING OVR ERN AREAS. AS A
RESULT...THE FORECAST MODELS HAVE LITTLE IN THE WAY OF PCPN OVR THE
CONTDVD TODAY. HOWEVER...THERE MAY STILL BE ENOUGH RESIDUAL MSTR TO
KEEP SOME ISOLD POPS IN THE FORECAST FOR THAT AREA. OVR THE ERN MTS
AND PLAINS...THE 4KM WRF HAS SOME VERY SPOTTY PCPN OCCURRING THIS
AFTERNOON AND EVENING WITH THE BEST CHANCES BEING ALONG THE SRN
BORDER. THE HRRR IS VERY SIMILAR TO THE 4KM WRF. THE NAM ON THE
OTHER HAND HAS SOME LIGHT PCPN BEING POSSIBLE MOST LOCATIONS OF THE
ERN MTS AND PLAINS. WITH THE MST PLUME STILL EXPECTED TO BE IN
PLACE...WL GO WITH GENERALLY ISOLD POPS ACRS MUCH OF THE SERN
PLAINS. MOST AREAS WILL AGAIN SEE HIGH TEMPS THAT ARE 5-10 DEGREES
ABOVE AVERAGE.
TONIGHT THE MSTR PLUME CONTINUE TO MOVE EAST...BUT CONTINUES TO
LINGER OVR THE FAR SERN AREAS. BY MIDNIGHT MOST AREAS SHOULD SEE AN
END TO THE PCPN...BUT THE MODELS DO CONTINUE TO HANG ON TO SOME PCPN
INTO THE LATE NIGHT HOURS OVR THE FAR SERN PLAINS.
LONG TERM...
(TUESDAY THROUGH SUNDAY)
TUESDAY...TROUGH MOVES ACROSS THE NORTHERN ROCKIES WITH COLORADO
BEING ON THE SOUTHERN EDGE OF THE TROUGH. MAIN FORECAST CHALLENGE WILL
BE THE AMOUNT OF LOW LEVEL MOISTURE ON THE PLAINS. LATEST NAM AND
GFS HAVE DEW POINTS IN THE 50S TO LOWER 60S ON THE PLAINS TUESDAY
AFTERNOON. MODELS HAVE BEEN PLAGUED BY OVER-FORECASTING DEW POINTS
DURING THE ENTIRE SUMMER...AND HAVE DEW POINTS IN THE 40S TO LOWER
50S IN THE GRIDS. BELIEVE HIGHEST DEW POINTS WILL CLOSE TO THE NEW
MEXICO BORDER WHERE GRIDS HAVE ISOLATED TO SCATTERED POPS.
OTHERWISE...ONLY HAVE SILENT POPS FOR THE REMAINDER OF THE PLAINS.
IN THE MOUNTAINS...DRIER AIR WILL MOVE INTO THE REGION AND HAVE
POPS OVER THE SOUTHERN MOUNTAINS. A COLD FRONT WILL MOVE SOUTHWARD
ACROSS THE PLAINS TUESDAY NIGHT. WITH SOME LOW LEVEL MOISTURE
REMAINING OVER THE SOUTHEAST PORTION OF THE PLAINS...A STORM OR TWO
COULD DEVELOP ALONG THE FRONT...AND MAINTAINED ISOLATED POPS
OVERNIGHT OVER PORTIONS OF THE PLAINS.
WEDNESDAY...COLD FRONT WILL MOVE SOUTH OF THE STATE BY THE
AFTERNOON...WITH EASTERLY FLOW POOLING LOW LEVEL MOISTURE MOSTLY
OVER NORTHERN NEW MEXICO. SOME OF THE GUIDANCE HAS ENOUGH MOISTURE
REMAINING OVER SOUTHERN COLORADO FOR A FEW AFTERNOON AND EARLY
EVENING STORMS. DECIDED TO MAINTAIN SOME ISOLATED POPS IN THIS
REGION...BUT HEAVIER PRECIPITATION WILL STAY TO THE SOUTH OF THE
STATE. TEMPERATURES ON THE PLAINS WILL COOL TO NEAR NORMAL BEHIND
THE FRONT.
THURSDAY...A WEAK DISTURBANCE WILL MOVE ACROSS THE REGION WITH
LOW LEVEL DRYING OVER THE INTERSTATE 25 CORRIDOR. GFS CONTINUES TO
BE MUCH TOO HIGH WITH SURFACE DEW POINTS NEAR THE KANSAS
BORDER...WITH DEW POINTS IN THE LOWER 60S AND CAPES AROUND 1500
J/KG. GRIDS HAVE DEW POINTS NEAR THE KANSAS BORDER IN THE MID TO
UPPER 40S...AND ONLY HAVE ISOLATED POPS NEAR THE KANSAS BORDER.
THE PASSING DISTURBANCE SHOULD HELP FIRE CONVECTION OVER THE
MOUNTAINS...FOR SOME AFTERNOON AND EARLY EVENING STORMS.
.FRIDAY THROUGH SUNDAY...A TROUGH MOVES SOUTHEAST OUT OF CANADA AND
INTO THE HIGH PLAINS FRIDAY AND FRIDAY NIGHT. A SHARP COLD FRONT
WILL MOVE SOUTHWARD ACROSS THE PLAINS ON FRIDAY. GFS HAS
WIDESPREAD PRECIPITATION OVER THE EASTERN PLAINS AND INTERSTATE 25
CORRIDOR BEHIND THE FRONT AS SYNOPTIC SCALE LIFT AHEAD OF THE
TROUGH PASSES OVER THE MOIST LOW LEVEL AIR MASS. GFS DEW POINTS ON
FRIDAY ARE IN THE UPPER 50S TO LOWER 60S ON THE PLAINS. ONCE
AGAIN...BELIEVE DEW POINTS ARE MUCH TOO HIGH. EC DEW POINTS ARE IN
THE 40S...WHICH IS MORE REASONABLE. HAVE GENERALLY ISOLATED POPS
ON THE PLAINS AND INTERSTATE 25 CORRIDOR ON FRIDAY TO ACCOUNT FOR
SOME SHOWERS. LOW LEVEL AIR MASS BEHIND THE FRONT WILL BE COOL AND
LACK OF LOW LEVEL MOISTURE WILL RESULT IN A GENERALLY STABLE AIR MASS.
COOL LOW LEVEL AIR MASS REMAINS ON THE PLAINS SATURDAY WITH THE
ATMOSPHERE REMAINING CAPPED. BY SUNDAY...THE COOL AIR MASS MOVE TO
THE EAST WITH WARMER TEMPERATURES. MOISTURE LOOKS TO BE LIMITED
WITH ONLY SILENT POPS. --PGW--
AVIATION...
VFR CONDITIONS ARE EXPECTED AT THE TAF SITES FOR THE NEXT 24 HOURS.
SOME SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP TODAY...BUT
MAY BE FAIRLY SPOTTY NR THE TAF SITES. KCOS WL PROBABLY HAVE THE
BEST CHANCE OF SEEING SOME SHOWERS OR THUNDERSTORMS IN THE VCNTY.
HOWEVER...CONFIDENCE IS TOO LOW AT THIS TIME TO INCLUDE ANY MENTION
OF TSRA IN THE TAFS.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
34/34
AREA FORECAST DISCUSSION
NWS PUEBLO CO
431 AM MDT MON SEP 3 2012
.SHORT TERM...
(TODAY AND TONIGHT)
RADAR IS STILL PICKING UP SOME ECHOES OVR THE FORECAST AREA...BUT
COVERAGE IS SPOTTY. WV SATELLITE IMAGERY SHOWING A PLUME OF
MSTR ACRS THE STATE THIS MORNING. MODELS SHOW DRIER AIR WORKING
INTO THE AREA FROM THE WEST...BUT REMAINING OVR ERN AREAS. AS A
RESULT...THE FORECAST MODELS HAVE LITTLE IN THE WAY OF PCPN OVR THE
CONTDVD TODAY. HOWEVER...THERE MAY STILL BE ENOUGH RESIDUAL MSTR TO
KEEP SOME ISOLD POPS IN THE FORECAST FOR THAT AREA. OVR THE ERN MTS
AND PLAINS...THE 4KM WRF HAS SOME VERY SPOTTY PCPN OCCURRING THIS
AFTERNOON AND EVENING WITH THE BEST CHANCES BEING ALONG THE SRN
BORDER. THE HRRR IS VERY SIMILAR TO THE 4KM WRF. THE NAM ON THE
OTHER HAND HAS SOME LIGHT PCPN BEING POSSIBLE MOST LOCATIONS OF THE
ERN MTS AND PLAINS. WITH THE MST PLUME STILL EXPECTED TO BE IN
PLACE...WL GO WITH GENERALLY ISOLD POPS ACRS MUCH OF THE SERN
PLAINS. MOST AREAS WILL AGAIN SEE HIGH TEMPS THAT ARE 5-10 DEGREES
ABOVE AVERAGE.
TONIGHT THE MSTR PLUME CONTINUE TO MOVE EAST...BUT CONTINUES TO
LINGER OVR THE FAR SERN AREAS. BY MIDNIGHT MOST AREAS SHOULD SEE AN
END TO THE PCPN...BUT THE MODELS DO CONTINUE TO HANG ON TO SOME PCPN
INTO THE LATE NIGHT HOURS OVR THE FAR SERN PLAINS.
.LONG TERM...
(TUESDAY THROUGH SUNDAY)
.TUESDAY...TROUGH MOVES ACROSS THE NORTHERN ROCKIES WITH COLORADO
BEING ON THE SOUTHERN EDGE OF THE TROUGH. MAIN FORECAST CHALLENGE WILL
BE THE AMOUNT OF LOW LEVEL MOISTURE ON THE PLAINS. LATEST NAM AND
GFS HAVE DEW POINTS IN THE 50S TO LOWER 60S ON THE PLAINS TUESDAY
AFTERNOON. MODELS HAVE BEEN PLAGUED BY OVER-FORECASTING DEW POINTS
DURING THE ENTIRE SUMMER...AND HAVE DEW POINTS IN THE 40S TO LOWER
50S IN THE GRIDS. BELIEVE HIGHEST DEW POINTS WILL CLOSE TO THE NEW
MEXICO BORDER WHERE GRIDS HAVE ISOLATED TO SCATTERED POPS.
OTHERWISE...ONLY HAVE SILENT POPS FOR THE REMAINDER OF THE PLAINS.
IN THE MOUNTAINS...DRIER AIR WILL MOVE INTO THE REGION AND HAVE
POPS OVER THE SOUTHERN MOUNTAINS. A COLD FRONT WILL MOVE SOUTHWARD
ACROSS THE PLAINS TUESDAY NIGHT. WITH SOME LOW LEVEL MOISTURE
REMAINING OVER THE SOUTHEAST PORTION OF THE PLAINS...A STORM OR TWO
COULD DEVELOP ALONG THE FRONT...AND MAINTAINED ISOLATED POPS
OVERNIGHT OVER PORTIONS OF THE PLAINS.
.WEDNESDAY...COLD FRONT WILL MOVE SOUTH OF THE STATE BY THE
AFTERNOON...WITH EASTERLY FLOW POOLING LOW LEVEL MOISTURE MOSTLY
OVER NORTHERN NEW MEXICO. SOME OF THE GUIDANCE HAS ENOUGH MOISTURE
REMAINING OVER SOUTHERN COLORADO FOR A FEW AFTERNOON AND EARLY
EVENING STORMS. DECIDED TO MAINTAIN SOME ISOLATED POPS IN THIS
REGION...BUT HEAVIER PRECIPITATION WILL STAY TO THE SOUTH OF THE
STATE. TEMPERATURES ON THE PLAINS WILL COOL TO NEAR NORMAL BEHIND
THE FRONT.
.THURSDAY...A WEAK DISTURBANCE WILL MOVE ACROSS THE REGION WITH
LOW LEVEL DRYING OVER THE INTERSTATE 25 CORRIDOR. GFS CONTINUES TO
BE MUCH TOO HIGH WITH SURFACE DEW POINTS NEAR THE KANSAS
BORDER...WITH DEW POINTS IN THE LOWER 60S AND CAPES AROUND 1500
J/KG. GRIDS HAVE DEW POINTS NEAR THE KANSAS BORDER IN THE MID TO
UPPER 40S...AND ONLY HAVE ISOLATED POPS NEAR THE KANSAS BORDER.
THE PASSING DISTURBANCE SHOULD HELP FIRE CONVECTION OVER THE
MOUNTAINS...FOR SOME AFTERNOON AND EARLY EVENING STORMS.
..FRIDAY THROUGH SUNDAY...A TROUGH MOVES SOUTHEAST OUT OF CANADA AND
INTO THE HIGH PLAINS FRIDAY AND FRIDAY NIGHT. A SHARP COLD FRONT
WILL MOVE SOUTHWARD ACROSS THE PLAINS ON FRIDAY. GFS HAS
WIDESPREAD PRECIPITATION OVER THE EASTERN PLAINS AND INTERSTATE 25
CORRIDOR BEHIND THE FRONT AS SYNOPTIC SCALE LIFT AHEAD OF THE
TROUGH PASSES OVER THE MOIST LOW LEVEL AIR MASS. GFS DEW POINTS ON
FRIDAY ARE IN THE UPPER 50S TO LOWER 60S ON THE PLAINS. ONCE
AGAIN...BELIEVE DEW POINTS ARE MUCH TOO HIGH. EC DEW POINTS ARE IN
THE 40S...WHICH IS MORE REASONABLE. HAVE GENERALLY ISOLATED POPS
ON THE PLAINS AND INTERSTATE 25 CORRIDOR ON FRIDAY TO ACCOUNT FOR
SOME SHOWERS. LOW LEVEL AIR MASS BEHIND THE FRONT WILL BE COOL AND
LACK OF LOW LEVEL MOISTURE WILL RESULT IN A GENERALLY STABLE AIR MASS.
COOL LOW LEVEL AIR MASS REMAINS ON THE PLAINS SATURDAY WITH THE
ATMOSPHERE REMAINING CAPPED. BY SUNDAY...THE COOL AIR MASS MOVE TO
THE EAST WITH WARMER TEMPERATURES. MOISTURE LOOKS TO BE LIMITED
WITH ONLY SILENT POPS. --PGW--
&&
.AVIATION...
VFR CONDITIONS ARE EXPECTED AT THE TAF SITES FOR THE NEXT 24 HOURS.
SOME SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP TODAY...BUT
MAY BE FAIRLY SPOTTY NR THE TAF SITES. KCOS WL PROBABLY HAVE THE
BEST CHANCE OF SEEING SOME SHOWERS OR THUNDERSTORMS IN THE VCNTY.
HOWEVER...CONFIDENCE IS TOO LOW AT THIS TIME TO INCLUDE ANY MENTION
OF TSRA IN THE TAFS.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
28/06
AREA FORECAST DISCUSSION
NWS TAUNTON MA
1018 PM EDT TUE SEP 4 2012
.SYNOPSIS...
A WARM FRONT WILL PUSH NORTH OF THE REGION TONIGHT...THEN LOW
PRESSURE WILL MOVE ACROSS NORTHERN NEW ENGLAND WEDNESDAY. ITS
ASSOCIATED COLD FRONT WILL WEAKEN AS IT PUSHES OFFSHORE LATE
WEDNESDAY AND WEDNESDAY NIGHT. WARM AND HUMID CONDITIONS WILL
CONTINUE THROUGH THE END OF THE WEEK INTO THIS WEEKEND. ALL EYES
WILL THEN FOCUS ON THE POSSIBLE TRACK OF TROPICAL STORM LESLIE LATE
THIS WEEKEND AND EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
1030 PM UPDATE...
A STRUGGLING FCST THIS EVNG. WHAT IS WELL KNOWN IS THAT ATMOS
COLUMN IS SATURATED UP TO H5 WITH PWATS AROUND 2 INCHES /SEE THE
0Z ALY-CHH-OKX SOUNDINGS/. TROPICAL AIRMASS WELL IN PLACE WITH SFC
DWPTS IN THE LOW-MID 70S. BOUNDARY LYR HAS DECOUPLED WHICH HAS
ALLOWED FOR THE ENHANCEMENT OF H925-85 S/SWLY FLOW /20-30 KTS/
AHEAD OF THE APPROACHING BAROCLINIC TROUGH PRESENTLY STRETCHED
ACROSS THE ERN GRT LKS WITH ATTENDANT SHRTWV IMPULSES AT VARIOUS
ATMOS LVLS.
WHAT IS DIFFICULT TO PINPOINT ARE THE BETTER RGNS OF LOW-LVL
MOISTURE CONVERGENCE AND ENHANCED ASCENT. WHILE THE BROAD AREA
ACROSS UPSTATE NY IS RESULTANT OF DEEP-LYR LIFT PER ENHANCED
ASCENT AND STRONG DIV ALOFT...ALONG AND AHEAD ACROSS NEW ENGLAND
IT BECOMES TEDIOUS TO ACCURATELY FCST THE AREAS OF BEST FORCING
TOWARDS SCTD HEAVY SHOWERS WITH PSBL EMBEDDED THUNDERSTORMS. CHC
TO LIKELY POPS WILL CONTINUE. HAVE BEEN FOLLOWING CLOSELY TO THE
LATEST HRRR FCSTS.
SCTD ACTIVITY CONTINUES TO MOVE NEWD ACROSS CENTRAL NEW ENGLAND.
RENEWED FOCUS PERTAINS TOWARDS THE SW WHERE A STRONG BAND OF HEAVY
SHOWERS AND EMBEDDED THUNDERSTORMS IS LIFTING NEWD OUT OF THE
NRN DELAWARE RVR VLY...INVIGORATED BY A CONVERGENT RGN OF H925-85
FLOW PER LATEST MESORUC. THERE ARE SOME CONCERNS WITH REGARDS TO
SEVERE WX WITH THIS BAND AS 0-1 KM SHEAR IS FAIRLY STRONG. WILL
HAVE TO WATCH CLOSELY WITH ITS APPROACH. THE ENVIRONMENT ACROSS
NEW ENGLAND EXHIBITS WEAK SHEAR AND INSTABILITY...BUT IT IS THE
ANTICIPATION THAT THE APPROACHING BAROCLINIC TROUGH WILL SHIFT
BETTER CONVECTIVE PARAMETERS INTO PORTIONS OF NEW ENGLAND.
CONTINUING THE DISCUSSION CONCERNING THOUGHTS BEHIND THE EVOLUTION
OF TONIGHTS WX...THE EXPECTATION IS FOR THE AFOREMENTIONED
INITIAL BAND TO LIFT NEWD INTO NEW ENGLAND BY MIDNIGHT. THIS BAND
IS PROGRESSIVE...BUT THAT DOES NOT RULE OUT THE THREAT OF 1-2
IN/HR RAINFALL RATES AND PSBL FLOODING. FROM MIDNIGHT INTO
MORNING...THE INITIAL BAND WILL LIFT NEWD TOWARDS THE BETTER AXIS
OF MOISTURE CONVERGENCE AS EMPHASIZED BY MDL FCSTS ACROSS CENTRAL
VT/NH...AS THE MAIN BAND ACROSS UPSTATE NY SLIDES E/SEWD INTO NEW
ENGLAND. IT IS WITH BETTER CERTAINTY THAT WITH THE BAROCLINIC
TROUGH AND ATTENDANT FORCING DURING THIS TIMEFRAME WILL YIELD A
LINE OF HEAVY RAINS AND PSBL FLOODING. HIGH CATEGORICAL POPS
ACCORDINGLY. HYDROLOGY SECTION OF THE AFD BELOW STILL APPLIES TO
THE CONTINUING SITUATION.
WARM AND HUMID CONDITIONS CONTINUE. TEMPS EXPECTED TO ONLY FALL A
FEW MORE DEGREES IN THE UPR 60S TO LOW 70S.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
WEDNESDAY...
EXPECT REMNANT LOW TO MOVE E THROUGH MAINE DURING THE MORNING...THEN
THE ASSOCIATED FRONT WILL SLOWLY WORK ACROSS THE REGION DURING THE
DAY. HOWEVER...AS THE FRONT BECOMES PARALLEL TO THE H850 UPPER
FLOW...WILL TEND TO SLOW DOWN. BEST MOISTURE CONVERGENCE AND
DYNAMICS MOVE WITH THE LOW...SO APPEARS THE FRONT WILL WEAKEN AS IT
SLIDES ACROSS.
BEST SHOT OF PRECIP IS EXPECTED DURING THE MORNING...AND THERE IS
STILL A CHANCE OF LOCALIZED FLOODING. THE PRECIP WILL THEN TEND TO
WEAKEN AS IT SLIDES SE. HAVE TRENDED POPS DOWNWARD DURING THE
AFTERNOON. THE FRONT WILL FINALLY REACH THE S COAST LATE IN THE DAY.
SHORT RANGE MODELS IN GOOD AGREEMENT IN BRINGING DRIER AIR INTO
NORTHERN AREAS BY EVENING.
EVEN WITH CLOUDS AND PRECIP ACROSS THE REGION...THE TROPICAL AIRMASS
WILL ALLOW TEMPS TO RISE TO THE UPPER 70S TO AROUND 80.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
* WARM/HUMID WITH ISOLATED SHOWERS/TSTMS POSSIBLE THU THROUGH SAT
* LARGE SURF FROM TROPICAL STORM LESLIE LIKELY IMPACTS SOUTHERN
NEW ENGLAND WATERS THIS WEEKEND INTO EARLY NEXT WEEK
OVERVIEW...
04/12Z GUIDANCE HAS COME INTO BETTER AGREEMENT WITH THE TRACK OF
LESLIE. STILL PLENTY OF QUESTIONS ON THE INTERACTION OF TROPICAL
STORM LESLIE AND AN AMPLIFYING MID-LEVEL TROUGH IN THE
APPALACHIANS LATE THIS WEEKEND. CONFIDENCE IS HIGHEST PRIOR TO
SATURDAY...THEN DIMINISHES QUITE A BIT SUNDAY INTO MONDAY. STILL
THINKING LESLIE WILL BE TRACKING EAST OF SOUTHERN NEW ENGLAND AT
THIS TIME. 04/12Z ECMWF IS ALSO NOW KEEPING LESLIE WELL EAST OF
NEW ENGLAND...WHICH IS MORE IN LINE WITH THE GFS AND GEFS MEAN.
WEDNESDAY NIGHT...
A FRONTAL BOUNDARY ACROSS SOUTHERN NEW ENGLAND WILL SLOWLY
APPROACH THE COAST OVERNIGHT. DEEPER MOISTURE PLUME AND LOW LEVEL
JET WILL BE OFFSHORE BY WED EVENING...SO HEAVIER RAINFALL SHOULD
HAVE MOVED OFF TO THE EAST AS WELL. HIGH PRECIPITABLE WATER
AIRMASS AND LOW-LEVEL CONVERGENCE ALONG THIS FRONT WILL CONTINUE
THREAT OF SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS. WILL HAVE
HIGHEST POPS NEAR THE COAST WHERE AXIS OF HIGHER THETA-E AIR WILL
BE LOCATED...WITH POPS DECREASING OVERNIGHT. PATCHY DENSE FOG
EXPECTED TO DEVELOP.
THURSDAY-SATURDAY...
A BROAD MID-LEVEL TROUGH OVER THE CENTRAL USA IS EXPECTED TO
AMPLIFY AND SHIFT ITS AXIS OVER THE GREAT LAKES DURING THIS
PERIOD. 04/12Z CANADIAN IS MUCH MORE PROGRESSIVE THAN THE OTHER
GUIDANCE AND WAS DISCOUNTED. EXPECTING A FRONTAL BOUNDARY TO LINGER
BETWEEN THE SOUTH COAST OF NEW ENGLAND AND THE MID ATLANTIC COAST.
HUMID AIRMASS WILL REMAIN ACROSS THE REGION...WHICH COMBINED WITH
DAYTIME HEATING AND CYCLONIC FLOW WILL LEAD TO A THREAT OF DIURNAL
SHOWERS/TSTMS THROUGH THIS PERIOD. FORECAST CAPES DURING MAX
HEATING EXPECTED TO BE 1000+ J/KG SO WOULD EXPECT ISOLD TO SCT
CONVECTION TO DEVELOP...ESPECIALLY INTERIOR WHERE AXIS OF
INSTABILITY SETS UP. WARM AND HUMID AIRMASS EXPECTED WITH 850 MB
TEMPS 15-16C SUPPORTING MAXES INTO THE LOW TO MID 80S AWAY FROM
THE COAST...BUT LIKELY COOLER SATURDAY DUE TO MORE CLOUD COVER.
SUNDAY-TUESDAY...
TS LESLIE WILL BE THE PRIMARY CONCERN DURING THIS PERIOD AS IT
TRACKS NORTHWARD OVER THE OPEN ATLANTIC. WHILE THERE ARE TIMING
DIFFERENCES AMONGST THE MODELS...THERE IS DECENT AGREEMENT ON A
TRACK WELL EAST OF THE BENCHMARK. COMPLEX PATTERN GIVEN
UNCERTAINTY WITH EVOLUTION OF CUTOFF LOW TO THE SOUTHWEST AND
EXTENT OF DOWNSTREAM RIDGING...AND FORECAST TIME RANGE LEADS TO
A LOW CONFIDENCE FORECAST FROM AN IMPACT PERSPECTIVE. AT THE VERY
LEAST EXPECTING LARGE SURF TO IMPACT THE SOUTHERN NEW ENGLAND OCEAN
BEACHES DURING THIS TIME. DID NOT MAKE MANY CHANGES TO THIS PORTION
OF THE FORECAST.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
FORECASTER CONFIDENCE LEVELS...
LOW...LESS THAN 30 PERCENT
MODERATE...30 PERCENT TO 60 PERCENT
HIGH...GREATER THAN 60 PERCENT
OVERVIEW...LOW TO MODERATE CONFIDENCE.
TONIGHT...MAINLY MVFR-IFR CIGS THROUGH 04Z...THEN IFR-LIFR CIGS
IN AREAS OF RAIN...WHICH MAY BE HEAVY AT TIMES. VFR-MVFR VSBYS
LOWERING TO MAINLY MVFR WITH AREAS OF IFR MAINLY ACROSS S NH/N MA.
ISOLD-SCT TSTMS MAINLY AFTER 03Z.
WEDNESDAY...EXPECT S-SW WINDS TO PICK UP ALONG THE S COAST...GUSTS
TO 20 KT. CIGS REMAIN IFR-LIFR THROUGH MIDDAY...THEN SLOWLY IMPROVE
TO MVFR EXCEPT REMAINING IFR ACROSS SE MA/CAPE COD. VSBYS MAINLY
MVFR WITH POCKETS OF IFR IN RAIN...HEAVY AT TIMES...AND ISOLD TSTMS.
KBOS TAF...MODERATE CONFIDENCE IN TAF.
MVFR-IFR CIGS THROUGH WED. VSBYS START OFF VFR...BUT EXPECT MAINLY
MVFR VSBYS BECOMING IFR TONIGHT. MAY SEE PERIODS OF LIFR CIGS/VSBYS
IN PERIODS OF HEAVY RAIN. LOW CONFIDENCE OF A TSRA HITTING THE
TERMINAL.
KBDL TAF...MODERATE CONFIDENCE IN TAF.
MVFR-IFR CIGS THROUGH MIDDAY WEDNESDAY...THEN MAY SEE SLOW
IMPROVEMENT TO VFR AFTER 18Z. VFR VSBYS INTO THIS EVENING...THEN
LOWERING TO MVFR-IFR THROUGH MIDDAY WED. VSBYS SHOULD IMPROVE AROUND
OR AFTER 18Z WED. LOW CONFIDENCE OF A TSRA HITTING THE TERMINAL.
OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY...
WEDNESDAY NIGHT...MODERATE TO HIGH CONFIDENCE. MVFR/IFR CONDITIONS
IN STRATUS AND FOG AND SCT SHOWERS.
THURSDAY THROUGH SUNDAY...MODERATE CONFIDENCE. AREAS OF LATE
NIGHT AND EARLY MORNING MVFR/IFR IN STRATUS/FOG...IMPROVING DURING
THE DAYTIME. ISOLD TO SCT SHOWERS/TSTMS POSSIBLE...ESPECIALLY
DURING THE AFTERNOON HOURS.
&&
.MARINE...
OVERVIEW...MODERATE TO HIGH CONFIDENCE.
WITH INCREASING S-SE SWELLS WITH LONG PERIODS FROM DISTANT TROPICAL
STORM LESLIE...ON THE ORDER OF 13-15 SECONDS...HAVE DECIDED TO ISSUE
HIGH SURF ADVISORY FOR THE SOUTH FACING BEACHES. HAVE PUT THIS UP
THROUGH THU FOR NOW...BUT WILL LIKELY NEED TO BE EXTENDED DEPENDENT
UPON LESLIE/S TRACK AND STRENGTH.
SMALL CRAFT ADVISORIES ALSO CONTINUE FOR THE OPEN WATERS AS WELL AS
BI AND RI SOUNDS. S-SW WINDS WILL GUST TO 25 KT LATE TONIGHT AND
WEDNESDAY OVER THE OUTER WATERS. EXPECT SEAS TO CONTINUE TO BUILD
THROUGH WEDNESDAY...UP TO 8 FT ON THE FAR OUTER WATERS. MAY SEE VSBY
RESTRICTIONS DUE TO HEAVY DOWNPOURS AND PATCHY FOG.
OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY...
SEAS WILL BE TRICKY ACROSS THE COASTAL WATERS...LEADING TO A
MODERATE CONFIDENCE FORECAST. MOST OF THE AVAILABLE WAVE GUIDANCE
DEPICTS LOWER WAVE HEIGHTS THURSDAY AS WINDS DIMINISH SLIGHTLY.
THE BIG QUESTION IS HOW MUCH SWELL IMPACTS THE WATERS FROM DISTANT
TROPICAL STORM LESLIE. HAVE MOVE CONFIDENCE IN LARGE SWELL
ASSOCIATED WITH LESLIE ARRIVING THIS WEEKEND.
&&
.HYDROLOGY...
AS REMNANTS OF HURRICANE ISAAC APPROACHES...EXPECT LOCALLY HEAVY
RAINFALL TO PUSH ACROSS THE REGION OVERNIGHT. EXPECT A GENERAL 1
TO 2 INCHES OF RAINFALL ACROSS THE REGION. THERE COULD BE SOME
HIGHER AMOUNTS...POSSIBLY UP TO 2.5 TO 3 INCHES ACROSS N MA/S NH.
SHOWERS AND SCATTERED THUNDERSTORMS ARE FORECAST...SOME OF WHICH
MAY PRODUCE RAINFALL RATES OF 1 TO 2 INCHES AN HOUR. FLOODING OF
MAINSTEM RIVERS NOT EXPECTED AT THIS POINT...BUT THERE MAY BE
LOCALIZED FLOODING OF SMALL STREAM AND TRIBUTARIES...AS WELL AS
URBAN AND POOR DRAINAGE AREAS.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...HIGH SURF ADVISORY FROM 6 AM WEDNESDAY TO 6 AM EDT THURSDAY
FOR MAZ020-022>024.
NH...NONE.
RI...HIGH SURF ADVISORY FROM 6 AM WEDNESDAY TO 6 AM EDT THURSDAY
FOR RIZ006>008.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT THURSDAY FOR ANZ235-237-
250-254>256.
&&
$$
SYNOPSIS...BELK/EVT
NEAR TERM...BELK/SIPPRELL/EVT
SHORT TERM...EVT
LONG TERM...BELK
AVIATION...BELK/EVT
MARINE...BELK/EVT
HYDROLOGY...WFO BOX
AREA FORECAST DISCUSSION
NWS TAUNTON MA
746 PM EDT TUE SEP 4 2012
.SYNOPSIS...
A WARM FRONT WILL PUSH NORTH OF THE REGION TONIGHT...THEN LOW
PRESSURE WILL MOVE ACROSS NORTHERN NEW ENGLAND WEDNESDAY. ITS
ASSOCIATED COLD FRONT WILL WEAKEN AS IT PUSHES OFFSHORE LATE
WEDNESDAY AND WEDNESDAY NIGHT. WARM AND HUMID CONDITIONS WILL
CONTINUE THROUGH THE END OF THE WEEK INTO THIS WEEKEND. ALL EYES
WILL THEN FOCUS ON THE POSSIBLE TRACK OF TROPICAL STORM LESLIE LATE
THIS WEEKEND AND EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
730 PM UPDATE...
SCATTERED SHOWERS CONTINUE TO MOVE NORTHEAST ALONG A LOW-LEVEL
AXIS OF HIGHER DEW POINTS. OBSERVED TRENDS HAS BEEN FOR THIS AREA
TO SHIFT FARTHER NORTH THIS EVENING. NOT EXPECTING MUCH IN THE WAY
OF THUNDERSTORMS THIS EVENING...DESPITE THE HIGH DEW POINTS...AS
THE INSTABILITY AND WIND FIELDS ARE RATHER WEAK. TWEAKED POPS
USING THE 21Z RAP AND LAV GUIDANCE TO REFLECT THE LATEST OBSERVED
TRENDS. ALSO TWEAKED TEMPERATURES AND DEW POINTS.
MAIN CONCERN CONTINUES TO BE POTENTIAL FOR LOCALLY HEAVY RAINFALL
OVERNIGHT. ALTHOUGH MOST OF SOUTHERN NEW ENGLAND DID NOT SEE
APPRECIABLE RAINFALL EARLIER TODAY.
PREVIOUS DISCUSSION...
BAND OF SHOWERS AND ISOLD TSTMS OVER E MA HAS WEAKENED AND MOVED
INTO MASS BAY AT 20Z...BUT MORE SCT SHOWERS HAVE DEVELOPED ACROSS
CENTRAL AND WESTERN AREAS. ANOTHER CLUSTER OF SHOWERS/SCT TSTMS HAS
ALSO DEVELOPED ACROSS N NJ/SE NY AHEAD OF APPROACHING WARM FRONT.
DEWPTS HAVE BEEN STEADILY INCREASING ESPECIALLY ACROSS S MA/RI/N CT
DURING THE AFTERNOON. PW/S UP TO 2 TO 2.2 INCHES NOTED IN THIS AREA
FROM SPC MESOANALYSIS...AS WELL AS K INDICES IN THE LOWER-MID 30S.
SYSTEM TO THE SW BEING CARRIED ON H850 FLOW TO THE NE...SO EXPECT
ANOTHER ROUND OF SHOWERS AND A FEW EMBEDDED TSTMS THIS EVENING.
THE CLUSTER OF PRECIP WILL MOVE OFFSHORE AS THE WARM FRONT MOVES N
OF THE REGION TONIGHT. THE UNSTABLE...TROPICAL AIRMASS WILL CAUSE
MORE SHOWERS/SCT TSTMS TO DEVELOP...WHILE LOW PRES /REMNANTS OF
HURRICANE ISAAC/ MOVES TOWARD NORTHERN NEW ENGLAND. STEADY
RAINFALL...WHICH WILL BE HEAVY AT TIMES THANKS TO VERY GOOD LOW AND
MID LEVEL MOISTURE CONVERGENCE AS WELL AS HIGH PW/S...WILL MOVE INTO
WESTERN AREAS AROUND OR AFTER MIDNIGHT. EXPECTING HEAVIEST RAINFALL
ACROSS S NH/N MA...CLOSEST TO THE BEST DYNAMICS. WILL CONTINUE TO
MONITOR FOR POSSIBLE LOCALIZED FLOODING IN ANY HEAVY RAINFALL...
PLEASE SEE FLOODING SECTION BELOW AS WELL AS THE HAZARDOUS WEATHER
OUTLOOK. HAVE CARRIED CATEGORICAL POPS FOR MOST AREAS.
WITH THE TROPICAL AIR SURGING INTO THE REGION BEHIND THE WARM
FRONT...DO NOT EXPECT TEMPS TO FALL BACK VERY FAR TONIGHT. WILL BE
WARM AND HUMID WITH LOWS IN THE MID 60S TO LOWER 70S...WHICH MAY
OCCUR AROUND MIDNIGHT BEFORE HOLDING STEADY OR EVEN SLOWLY RISE
OVERNIGHT.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
WEDNESDAY...
EXPECT REMNANT LOW TO MOVE E THROUGH MAINE DURING THE MORNING...THEN
THE ASSOCIATED FRONT WILL SLOWLY WORK ACROSS THE REGION DURING THE
DAY. HOWEVER...AS THE FRONT BECOMES PARALLEL TO THE H850 UPPER
FLOW...WILL TEND TO SLOW DOWN. BEST MOISTURE CONVERGENCE AND
DYNAMICS MOVE WITH THE LOW...SO APPEARS THE FRONT WILL WEAKEN AS IT
SLIDES ACROSS.
BEST SHOT OF PRECIP IS EXPECTED DURING THE MORNING...AND THERE IS
STILL A CHANCE OF LOCALIZED FLOODING. THE PRECIP WILL THEN TEND TO
WEAKEN AS IT SLIDES SE. HAVE TRENDED POPS DOWNWARD DURING THE
AFTERNOON. THE FRONT WILL FINALLY REACH THE S COAST LATE IN THE DAY.
SHORT RANGE MODELS IN GOOD AGREEMENT IN BRINGING DRIER AIR INTO
NORTHERN AREAS BY EVENING.
EVEN WITH CLOUDS AND PRECIP ACROSS THE REGION...THE TROPICAL AIRMASS
WILL ALLOW TEMPS TO RISE TO THE UPPER 70S TO AROUND 80.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
* WARM/HUMID WITH ISOLATED SHOWERS/TSTMS POSSIBLE THU THROUGH SAT
* LARGE SURF FROM TROPICAL STORM LESLIE LIKELY IMPACTS SOUTHERN
NEW ENGLAND WATERS THIS WEEKEND INTO EARLY NEXT WEEK
OVERVIEW...
04/12Z GUIDANCE HAS COME INTO BETTER AGREEMENT WITH THE TRACK OF
LESLIE. STILL PLENTY OF QUESTIONS ON THE INTERACTION OF TROPICAL
STORM LESLIE AND AN AMPLIFYING MID-LEVEL TROUGH IN THE
APPALACHIANS LATE THIS WEEKEND. CONFIDENCE IS HIGHEST PRIOR TO
SATURDAY...THEN DIMINISHES QUITE A BIT SUNDAY INTO MONDAY. STILL
THINKING LESLIE WILL BE TRACKING EAST OF SOUTHERN NEW ENGLAND AT
THIS TIME. 04/12Z ECMWF IS ALSO NOW KEEPING LESLIE WELL EAST OF
NEW ENGLAND...WHICH IS MORE IN LINE WITH THE GFS AND GEFS MEAN.
WEDNESDAY NIGHT...
A FRONTAL BOUNDARY ACROSS SOUTHERN NEW ENGLAND WILL SLOWLY
APPROACH THE COAST OVERNIGHT. DEEPER MOISTURE PLUME AND LOW LEVEL
JET WILL BE OFFSHORE BY WED EVENING...SO HEAVIER RAINFALL SHOULD
HAVE MOVED OFF TO THE EAST AS WELL. HIGH PRECIPITABLE WATER
AIRMASS AND LOW-LEVEL CONVERGENCE ALONG THIS FRONT WILL CONTINUE
THREAT OF SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS. WILL HAVE
HIGHEST POPS NEAR THE COAST WHERE AXIS OF HIGHER THETA-E AIR WILL
BE LOCATED...WITH POPS DECREASING OVERNIGHT. PATCHY DENSE FOG
EXPECTED TO DEVELOP.
THURSDAY-SATURDAY...
A BROAD MID-LEVEL TROUGH OVER THE CENTRAL USA IS EXPECTED TO
AMPLIFY AND SHIFT ITS AXIS OVER THE GREAT LAKES DURING THIS
PERIOD. 04/12Z CANADIAN IS MUCH MORE PROGRESSIVE THAN THE OTHER
GUIDANCE AND WAS DISCOUNTED. EXPECTING A FRONTAL BOUNDARY TO LINGER
BETWEEN THE SOUTH COAST OF NEW ENGLAND AND THE MID ATLANTIC COAST.
HUMID AIRMASS WILL REMAIN ACROSS THE REGION...WHICH COMBINED WITH
DAYTIME HEATING AND CYCLONIC FLOW WILL LEAD TO A THREAT OF DIURNAL
SHOWERS/TSTMS THROUGH THIS PERIOD. FORECAST CAPES DURING MAX
HEATING EXPECTED TO BE 1000+ J/KG SO WOULD EXPECT ISOLD TO SCT
CONVECTION TO DEVELOP...ESPECIALLY INTERIOR WHERE AXIS OF
INSTABILITY SETS UP. WARM AND HUMID AIRMASS EXPECTED WITH 850 MB
TEMPS 15-16C SUPPORTING MAXES INTO THE LOW TO MID 80S AWAY FROM
THE COAST...BUT LIKELY COOLER SATURDAY DUE TO MORE CLOUD COVER.
SUNDAY-TUESDAY...
TS LESLIE WILL BE THE PRIMARY CONCERN DURING THIS PERIOD AS IT
TRACKS NORTHWARD OVER THE OPEN ATLANTIC. WHILE THERE ARE TIMING
DIFFERENCES AMONGST THE MODELS...THERE IS DECENT AGREEMENT ON A
TRACK WELL EAST OF THE BENCHMARK. COMPLEX PATTERN GIVEN
UNCERTAINTY WITH EVOLUTION OF CUTOFF LOW TO THE SOUTHWEST AND
EXTENT OF DOWNSTREAM RIDGING...AND FORECAST TIME RANGE LEADS TO
A LOW CONFIDENCE FORECAST FROM AN IMPACT PERSPECTIVE. AT THE VERY
LEAST EXPECTING LARGE SURF TO IMPACT THE SOUTHERN NEW ENGLAND OCEAN
BEACHES DURING THIS TIME. DID NOT MAKE MANY CHANGES TO THIS PORTION
OF THE FORECAST.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
FORECASTER CONFIDENCE LEVELS...
LOW...LESS THAN 30 PERCENT
MODERATE...30 PERCENT TO 60 PERCENT
HIGH...GREATER THAN 60 PERCENT
OVERVIEW...LOW TO MODERATE CONFIDENCE.
TONIGHT...MAINLY MVFR-IFR CIGS THROUGH 04Z...THEN IFR-LIFR CIGS
IN AREAS OF RAIN...WHICH MAY BE HEAVY AT TIMES. VFR-MVFR VSBYS
LOWERING TO MAINLY MVFR WITH AREAS OF IFR MAINLY ACROSS S NH/N MA.
ISOLD-SCT TSTMS MAINLY AFTER 03Z.
WEDNESDAY...EXPECT S-SW WINDS TO PICK UP ALONG THE S COAST...GUSTS
TO 20 KT. CIGS REMAIN IFR-LIFR THROUGH MIDDAY...THEN SLOWLY IMPROVE
TO MVFR EXCEPT REMAINING IFR ACROSS SE MA/CAPE COD. VSBYS MAINLY
MVFR WITH POCKETS OF IFR IN RAIN...HEAVY AT TIMES...AND ISOLD TSTMS.
KBOS TAF...MODERATE CONFIDENCE IN TAF.
MVFR-IFR CIGS THROUGH WED. VSBYS START OFF VFR...BUT EXPECT MAINLY
MVFR VSBYS BECOMING IFR TONIGHT. MAY SEE PERIODS OF LIFR CIGS/VSBYS
IN PERIODS OF HEAVY RAIN. LOW CONFIDENCE OF A TSRA HITTING THE
TERMINAL.
KBDL TAF...MODERATE CONFIDENCE IN TAF.
MVFR-IFR CIGS THROUGH MIDDAY WEDNESDAY...THEN MAY SEE SLOW
IMPROVEMENT TO VFR AFTER 18Z. VFR VSBYS INTO THIS EVENING...THEN
LOWERING TO MVFR-IFR THROUGH MIDDAY WED. VSBYS SHOULD IMPROVE AROUND
OR AFTER 18Z WED. LOW CONFIDENCE OF A TSRA HITTING THE TERMINAL.
OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY...
WEDNESDAY NIGHT...MODERATE TO HIGH CONFIDENCE. MVFR/IFR CONDITIONS
IN STRATUS AND FOG AND SCT SHOWERS.
THURSDAY THROUGH SUNDAY...MODERATE CONFIDENCE. AREAS OF LATE
NIGHT AND EARLY MORNING MVFR/IFR IN STRATUS/FOG...IMPROVING DURING
THE DAYTIME. ISOLD TO SCT SHOWERS/TSTMS POSSIBLE...ESPECIALLY
DURING THE AFTERNOON HOURS.
&&
.MARINE...
OVERVIEW...MODERATE TO HIGH CONFIDENCE.
WITH INCREASING S-SE SWELLS WITH LONG PERIODS FROM DISTANT TROPICAL
STORM LESLIE...ON THE ORDER OF 13-15 SECONDS...HAVE DECIDED TO ISSUE
HIGH SURF ADVISORY FOR THE SOUTH FACING BEACHES. HAVE PUT THIS UP
THROUGH THU FOR NOW...BUT WILL LIKELY NEED TO BE EXTENDED DEPENDENT
UPON LESLIE/S TRACK AND STRENGTH.
SMALL CRAFT ADVISORIES ALSO CONTINUE FOR THE OPEN WATERS AS WELL AS
BI AND RI SOUNDS. S-SW WINDS WILL GUST TO 25 KT LATE TONIGHT AND
WEDNESDAY OVER THE OUTER WATERS. EXPECT SEAS TO CONTINUE TO BUILD
THROUGH WEDNESDAY...UP TO 8 FT ON THE FAR OUTER WATERS. MAY SEE VSBY
RESTRICTIONS DUE TO HEAVY DOWNPOURS AND PATCHY FOG.
OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY...
SEAS WILL BE TRICKY ACROSS THE COASTAL WATERS...LEADING TO A
MODERATE CONFIDENCE FORECAST. MOST OF THE AVAILABLE WAVE GUIDANCE
DEPICTS LOWER WAVE HEIGHTS THURSDAY AS WINDS DIMINISH SLIGHTLY.
THE BIG QUESTION IS HOW MUCH SWELL IMPACTS THE WATERS FROM DISTANT
TROPICAL STORM LESLIE. HAVE MOVE CONFIDENCE IN LARGE SWELL
ASSOCIATED WITH LESLIE ARRIVING THIS WEEKEND.
&&
.HYDROLOGY...
AS REMNANTS OF HURRICANE ISAAC APPROACHES...EXPECT LOCALLY HEAVY
RAINFALL TO PUSH ACROSS THE REGION. LOOKS LIKE THE BEST SHOT OF
HEAVY RAINFALL WILL MOVE IN LATE THIS EVENING AND OVERNIGHT. EXPECT
A GENERAL 1 TO 2 INCHES OF RAINFALL ACROSS THE REGION. THERE COULD
BE SOME HIGHER AMOUNTS...POSSIBLY UP TO 2.5 TO 3 INCHES ACROSS N
MA/S NH. SHOWERS AND SCATTERED THUNDERSTORMS ARE FORECAST...SOME OF
WHICH MAY PRODUCE RAINFALL RATES OF 1 TO 2 INCHES AN HOUR. FLOODING
OF MAINSTEM RIVERS NOT EXPECTED AT THIS POINT...BUT THERE MAY BE
LOCALIZED FLOODING OF SMALL STREAM AND TRIBUTARIES...AS WELL AS
URBAN AND POOR DRAINAGE AREAS...WILL BE POSSIBLE.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...HIGH SURF ADVISORY FROM 6 AM WEDNESDAY TO 6 AM EDT THURSDAY
FOR MAZ020-022>024.
NH...NONE.
RI...HIGH SURF ADVISORY FROM 6 AM WEDNESDAY TO 6 AM EDT THURSDAY
FOR RIZ006>008.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT THURSDAY FOR ANZ235-237-
250-254>256.
&&
$$
SYNOPSIS...BELK/EVT
NEAR TERM...BELK/EVT
SHORT TERM...EVT
LONG TERM...BELK
AVIATION...BELK/EVT
MARINE...BELK/EVT
HYDROLOGY...WFO BOX
AREA FORECAST DISCUSSION
NWS ALBANY NY
129 AM EDT MON SEP 3 2012
.SYNOPSIS...
HIGH PRESSURE WILL KEEP OUR REGION MAINLY DRY THROUGH MONDAY. THE
REMNANTS OF ISAAC WILL APPROACH THE AREA ON LABOR DAY...BRINGING
AN INCREASE IN CLOUDINESS AND A THREAT OF RAIN STARTING MONDAY
NIGHT AND CONTINUING THROUGH THE MID WEEK PERIOD. RAIN WILL BE
HEAVY AT TIMES.
&&
.NEAR TERM /THROUGH TODAY/...
AS OF 100 AM EDT...SKIES REMAIN MOSTLY CLEAR ACROSS THE
REGION...WITH THE EXCEPTION OF PATCHY LOW CLOUDS DEVELOPING ACROSS
PORTIONS OF THE LITCHFIELD HILLS AND MID HUDSON VALLEY.
EVENTUALLY...WINDS SHOULD GRADUALLY VEER MORE INTO THE
E/SE...WHICH SHOULD BRING INCREASING LOW LEVEL MOISTURE BACK INTO
THE REGION...ESPECIALLY LATE. THE LATEST NAM 12 AND RUC BOTH
DEPICT LOW CLOUDS DEVELOPING ACROSS WESTERN MA AND NW CT AROUND OR
SHORTLY AFTER MIDNIGHT...THEN EXPANDING WEST INTO THE SE
CATSKILLS...AND POSSIBLY NORTHWARD WITHIN THE HUDSON RIVER VALLEY
FROM ALBANY SOUTH BY DAYBREAK. WILL ONLY MENTION PARTLY CLOUDY
SKIES FOR MOST AREAS AS CLOUDS SHOULD BE RATHER PATCHY. IN
ADDITION...PATCHY FOG MAY FORM WITHIN RIVER VALLEYS...AND ALSO
ACROSS HIGHER ELEVATIONS ACROSS THE GREENS/BERKSHIRES/LITCHFIELD
HILLS EARLY THIS MORNING.
EXPECT OVERNIGHT MINS TO FALL INTO THE 40S AND 50S ACROSS MOST
AREAS FROM THE MOHAWK RIVER VALLEY NORTH INTO THE SOUTHERN
ADIRONDACKS...WITH 50S TO LOWER 60S FURTHER S AND E...WHERE SOME
CLOUDS AND HIGHER LOW LEVEL MOISTURE AMOUNTS SHOULD DEVELOP.
ON LABOR DAY...EXPECT MID AND HIGH CLOUDS TO INCREASE FROM
SOUTHWEST TO NORTHEAST WITH SOME WIDELY SCATTERED SHOWERS
DEVELOPING DURING THE AFTERNOON ACROSS SW PTNS OF THE FA. HIGHS
ARE EXPECTED TO BE IN THE MID 70S TO AROUND 80.
&&
.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
WHILE QPF AMOUNTS VARY SOME AMONGST THE MODELS...ALL THE GUIDANCE
SUGGESTS THAT THE REMNANTS OF ISAAC WILL IMPACT OUR REGION THROUGH
THE MID WEEK PERIOD WITH INCREASING POPS MONDAY NIGHT ESPECIALLY
DURING THE SECOND HALF OF THE NIGHT AND THEN LIKELY TO CATEGORICAL
POPS TUESDAY INTO WEDNESDAY ALTHOUGH ACTIVITY MAY START TO
DIMINISH BY WEDNESDAY AFTERNOON WITH STEADIER PCPN BECOMING MORE
SCATTERED ESPECIALLY ACRS NW PTNS OF THE FA. THE HEAVIEST PCPN AT
THIS TIME APPEARS TO BE DURING THE TUESDAY AFTERNOON THROUGH
WEDNESDAY MORNING TIME FRAME ACRS THE BULK OF THE REGION. THIS IS
THE PERIOD WHEN THE H10-H8 THETA E RIDGE IS THE STRONGEST ACRS THE
FA SLIDING FORM NW TO SE WITH TIME AS WELL AS PWATS 1.5 TO
SLIGHTLY OVER 2 INCHES.
SPECIFICALLY FOR THE PERIOD FROM MONDAY NIGHT THROUGH
WEDNESDAY...EXPECT CHANCES OF RAIN AND ISOLATED THUNDERSTORMS
TO INCREASE FROM SOUTHWEST TO NORTHEAST ACROSS THE REGION MONDAY
NIGHT. RAIN AND ISOLATED THUNDERSTORMS WITH RAINFALL HEAVY AT
TIMES CONTINUE TUESDAY AND TUESDAY NIGHT. ON WEDNESDAY EXPECT THE
HEAVIEST RAIN IN THE MORNING WITH MORE SCATTERED CONVECTION DURING
THE AFTERNOON. ON WEDNESDAY THERE MAY ALSO BE SOME BREAKS IN THE
OVERCAST WHICH COUPLED WITH SURFACE HEATING AND AN UNSTABLE
AIRMASS STILL IN PLACE WILL INCREASE THE CHANCE FOR
THUNDERSTORMS...SO HAVE CHANCE OF THUNDERSTORMS MENTIONED ON
WEDNESDAY. WHILE THE THUNDERSTORMS ARE NOT EXPECTED TO BE SEVERE
MORE HEAVY DOWNPOURS ARE POSSIBLE. EXPECT LOWS MONDAY NIGHT IN THE
MID 70S TO MID 80S.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
A SECONDARY COLD FRONT WILL IMPACT THE FORECAST AREA IN THE WAKE OF
THE MOISTURE ASSOCIATED ISAAC WED NIGHT INTO THU. THE GFS SHOWS
MODEST AMOUNTS OF INSTABILITY WITH SFC DEWPTS IN THE M50S TO L60S.
PWATS REMAIN AROUND AN INCH. THE BEST CHANCE OF SHOWERS AND
THUNDERSTORMS WILL BE WITH THE COLD FRONT THU. MAX TEMPS WILL
GENERALLY BE IN THE M70S TO L80S.
THU NIGHT THRU FRI NIGHT...THE HPC GUIDANCE/GFS/ECMWF SHOW A BREAK
IN THE MID WEEK UNSETTLED WEATHER...WITH HIGH PRESSURE BUILDING IN
FROM THE OHIO VALLEY OVER PA AND THE NORTHEAST. LOWER HUMIDITY
LEVELS AND DRY CONDITIONS WILL PREVAIL BEFORE THE NEXT UPSTREAM
SYSTEM OVER THE CNTRL MS RIVER VALLEY IMPACTS NY AND NEW ENGLAND ON
THE WEEKEND. LOWS WILL BE IN 50S TO L60S THU NIGHT...AND U40S TO
U50S FRI NIGHT. NEAR NORMAL HIGHS ARE EXPECTED ON FRI IN THE M70S
TO NEAR 80F IN THE VALLEYS...AND U60S TO M70S OVER THE HILLS AND
MTNS.
SATURDAY INTO SUNDAY...SOME TIMING DIFFERENCES FOR NEXT WEEKEND WITH
THE EVOLUTION OF THE POSITIVELY TILTED LONGWAVE TROUGH OVER THE ERN
HALF OF THE CONUS AND THE DEVELOPING SW FLOW ALOFT OVER THE ERN
SEABOARD. THE FRONTAL BOUNDARY ON THE LEADING EDGE OF THE UPPER
TROUGH WILL LIKELY HANG TO THE WEST OF THE COASTAL PLAIN WITH
PERHAPS AREAS OF LOW PRESSURE BRINGING SHOWERS/RAINFALL TO THE FCST
AREA BOTH DAYS ON THE WEEKEND. SOME OF THE GUIDANCE WOULD KEEP SAT
DRY...AND SUNDAY MORE UNSETTLED. THIS UPPER TROUGH SHOULD HELP
STEER LESLIE FAR ENOUGH EAST OF NEW ENGLAND FOR NO SIGNIFICANT
IMPACTS. WE TRENDED CLOSER TO THE LATEST HPC GUIDANCE WITH A LOW
CHANCE OF SHOWERS EACH DAY. HIGHS WILL BE SEASONABLE FOR THE 2ND
WEEKEND OF SEPT.
OVERALL...TEMPS WILL TREND SLIGHTLY ABOVE NORMAL...AND PCPN MAY BE
NEAR NORMAL OR SLIGHTLY ABOVE FOR THE EXTENDED.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
HIGH PRESSURE WILL MOVE EAST OF MAINE THROUGH THE EARLY MORNING
HOURS. A WARM FRONT WILL SLOWLY APPROACH FROM THE OHIO VALLEY AND
PENNSYLVANIA LATER TODAY.
LOW LEVEL MOISTURE WILL GRADUALLY INCREASE FROM THE SOUTHEAST
LATER THROUGH THE EARLY MORNING HOURS. THIS SHOULD ALLOW
STRATUS/MIST AND MVFR/IFR CONDITIONS TO DEVELOP...ESPECIALLY AT
KPOU AND KPSF...BUT AT LEAST SCATTERED CLOUDS BETWEEN 1000-3000
FEET ARE EXPECTED AT ALL SITES THROUGH THE EARLY MORNING HOURS.
SOME AREAS OF FOG...ESPECIALLY NEAR KGFL/PSF MAY FORM LATE TONIGHT
AS WELL.
THE LOW STRATUS AND/OR ANY FOG WILL DISSIPATE BTWN 12Z-
15Z/MON...HOWEVER A HIGHER STRATUS DECK WILL INCREASE THROUGHOUT
THE DAY...AS A LOW PRESSURE SYSTEM AND ITS WARM FRONT MOVES INTO
THE AREA.
WINDS THROUGH THE EARLY MORNING HOURS WILL BE LIGHT TO CALM AND
SHIFT TO MORE OF A SOUTHEAST DIRECTION AFTER 12Z AT 5-10 KTS.
WINDS MAY BE A BIT STRONGER AT KALB DUE TO FUNNELING EFFECTS UP
THE HUDSON RIVER VALLEY.
OUTLOOK...
MON NIGHT...VFR BECOMING MVFR/IFR. CHC -SHRA AND ISOL -TSRA LATE.
TUE...MVFR/IFR. SHRA LIKELY.
WED-THU...VFR/MVFR. CHC -SHRA/-TSRA.
FRI...VFR...NO SIG WX.
&&
.FIRE WEATHER...
HIGH PRESSURE WILL KEEP OUR REGION MAINLY DRY THROUGH TONIGHT.
THE REMNANTS OF ISAAC WILL APPROACH THE AREA ON LABOR
DAY...BRINGING AN INCREASE IN CLOUDINESS AND A THREAT OF SHOWERS
STARTING MONDAY NIGHT AND CONTINUING THROUGH THE MID WEEK PERIOD.
RELATIVE HUMIDITIES WILL INCREASE TO 80 TO 100 PERCENT
TONIGHT...DROP TO 50 TO 70 PERCENT ON MONDAY...RECOVER TO 100
PERCENT MONDAY NIGHT...AND ONLY DROP TO 70 TO 90 PERCENT ON TUESDAY.
WINDS WILL BE LIGHT AND VARIABLE TONIGHT...AND SOUTH TO SOUTHEAST
MONDAY THROUGH TUESDAY.
&&
.HYDROLOGY...
MAINLY DRY WEATHER IS EXPECTED THROUGH LABOR DAY. THE REMNANTS OF
ISAAC WILL INTERACT WITH A FRONT AND BRING RAIN TO OUR AREA
BEGINNING MONDAY NIGHT AND CONTINUING THROUGH THE MID WEEK PERIOD.
AT THIS TIME THE LATEST MODEL GUIDANCE SUGGESTS A WIDESPREAD 1 TO
3 INCHES OF RAIN WITH LOCALLY HIGHER AMOUNTS OF AROUND 4 INCHES
ACROSS SOUTHEAST PORTIONS OF THE AREA. NO RIVER FLOODING IS FORECAST
AT THIS TIME.
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...11/JPV
NEAR TERM...KL/11/JPV
SHORT TERM...11
LONG TERM...WASULA
AVIATION...NAS
FIRE WEATHER...11
HYDROLOGY...11
AREA FORECAST DISCUSSION
NWS ALBANY NY
102 AM EDT MON SEP 3 2012
.SYNOPSIS...
HIGH PRESSURE WILL KEEP OUR REGION MAINLY DRY THROUGH MONDAY. THE
REMNANTS OF ISAAC WILL APPROACH THE AREA ON LABOR DAY...BRINGING
AN INCREASE IN CLOUDINESS AND A THREAT OF RAIN STARTING MONDAY
NIGHT AND CONTINUING THROUGH THE MID WEEK PERIOD. RAIN WILL BE
HEAVY AT TIMES.
&&
.NEAR TERM /THROUGH TODAY/...
AS OF 100 AM EDT...SKIES REMAIN MOSTLY CLEAR ACROSS THE
REGION...WITH THE EXCEPTION OF PATCHY LOW CLOUDS DEVELOPING ACROSS
PORTIONS OF THE LITCHFIELD HILLS AND MID HUDSON VALLEY.
EVENTUALLY...WINDS SHOULD GRADUALLY VEER MORE INTO THE
E/SE...WHICH SHOULD BRING INCREASING LOW LEVEL MOISTURE BACK INTO
THE REGION...ESPECIALLY LATE. THE LATEST NAM 12 AND RUC BOTH
DEPICT LOW CLOUDS DEVELOPING ACROSS WESTERN MA AND NW CT AROUND OR
SHORTLY AFTER MIDNIGHT...THEN EXPANDING WEST INTO THE SE
CATSKILLS...AND POSSIBLY NORTHWARD WITHIN THE HUDSON RIVER VALLEY
FROM ALBANY SOUTH BY DAYBREAK. WILL ONLY MENTION PARTLY CLOUDY
SKIES FOR MOST AREAS AS CLOUDS SHOULD BE RATHER PATCHY. IN
ADDITION...PATCHY FOG MAY FORM WITHIN RIVER VALLEYS...AND ALSO
ACROSS HIGHER ELEVATIONS ACROSS THE GREENS/BERKSHIRES/LITCHFIELD
HILLS EARLY THIS MORNING.
EXPECT OVERNIGHT MINS TO FALL INTO THE 40S AND 50S ACROSS MOST
AREAS FROM THE MOHAWK RIVER VALLEY NORTH INTO THE SOUTHERN
ADIRONDACKS...WITH 50S TO LOWER 60S FURTHER S AND E...WHERE SOME
CLOUDS AND HIGHER LOW LEVEL MOISTURE AMOUNTS SHOULD DEVELOP.
ON LABOR DAY...EXPECT MID AND HIGH CLOUDS TO INCREASE FROM
SOUTHWEST TO NORTHEAST WITH SOME WIDELY SCATTERED SHOWERS
DEVELOPING DURING THE AFTERNOON ACROSS SW PTNS OF THE FA. HIGHS
ARE EXPECTED TO BE IN THE MID 70S TO AROUND 80.
&&
.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
WHILE QPF AMOUNTS VARY SOME AMONGST THE MODELS...ALL THE GUIDANCE
SUGGESTS THAT THE REMNANTS OF ISAAC WILL IMPACT OUR REGION THROUGH
THE MID WEEK PERIOD WITH INCREASING POPS MONDAY NIGHT ESPECIALLY
DURING THE SECOND HALF OF THE NIGHT AND THEN LIKELY TO CATEGORICAL
POPS TUESDAY INTO WEDNESDAY ALTHOUGH ACTIVITY MAY START TO
DIMINISH BY WEDNESDAY AFTERNOON WITH STEADIER PCPN BECOMING MORE
SCATTERED ESPECIALLY ACRS NW PTNS OF THE FA. THE HEAVIEST PCPN AT
THIS TIME APPEARS TO BE DURING THE TUESDAY AFTERNOON THROUGH
WEDNESDAY MORNING TIME FRAME ACRS THE BULK OF THE REGION. THIS IS
THE PERIOD WHEN THE H10-H8 THETA E RIDGE IS THE STRONGEST ACRS THE
FA SLIDING FORM NW TO SE WITH TIME AS WELL AS PWATS 1.5 TO
SLIGHTLY OVER 2 INCHES.
SPECIFICALLY FOR THE PERIOD FROM MONDAY NIGHT THROUGH
WEDNESDAY...EXPECT CHANCES OF RAIN AND ISOLATED THUNDERSTORMS
TO INCREASE FROM SOUTHWEST TO NORTHEAST ACROSS THE REGION MONDAY
NIGHT. RAIN AND ISOLATED THUNDERSTORMS WITH RAINFALL HEAVY AT
TIMES CONTINUE TUESDAY AND TUESDAY NIGHT. ON WEDNESDAY EXPECT THE
HEAVIEST RAIN IN THE MORNING WITH MORE SCATTERED CONVECTION DURING
THE AFTERNOON. ON WEDNESDAY THERE MAY ALSO BE SOME BREAKS IN THE
OVERCAST WHICH COUPLED WITH SURFACE HEATING AND AN UNSTABLE
AIRMASS STILL IN PLACE WILL INCREASE THE CHANCE FOR
THUNDERSTORMS...SO HAVE CHANCE OF THUNDERSTORMS MENTIONED ON
WEDNESDAY. WHILE THE THUNDERSTORMS ARE NOT EXPECTED TO BE SEVERE
MORE HEAVY DOWNPOURS ARE POSSIBLE. EXPECT LOWS MONDAY NIGHT IN THE
MID 70S TO MID 80S.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
A SECONDARY COLD FRONT WILL IMPACT THE FORECAST AREA IN THE WAKE OF
THE MOISTURE ASSOCIATED ISAAC WED NIGHT INTO THU. THE GFS SHOWS
MODEST AMOUNTS OF INSTABILITY WITH SFC DEWPTS IN THE M50S TO L60S.
PWATS REMAIN AROUND AN INCH. THE BEST CHANCE OF SHOWERS AND
THUNDERSTORMS WILL BE WITH THE COLD FRONT THU. MAX TEMPS WILL
GENERALLY BE IN THE M70S TO L80S.
THU NIGHT THRU FRI NIGHT...THE HPC GUIDANCE/GFS/ECMWF SHOW A BREAK
IN THE MID WEEK UNSETTLED WEATHER...WITH HIGH PRESSURE BUILDING IN
FROM THE OHIO VALLEY OVER PA AND THE NORTHEAST. LOWER HUMIDITY
LEVELS AND DRY CONDITIONS WILL PREVAIL BEFORE THE NEXT UPSTREAM
SYSTEM OVER THE CNTRL MS RIVER VALLEY IMPACTS NY AND NEW ENGLAND ON
THE WEEKEND. LOWS WILL BE IN 50S TO L60S THU NIGHT...AND U40S TO
U50S FRI NIGHT. NEAR NORMAL HIGHS ARE EXPECTED ON FRI IN THE M70S
TO NEAR 80F IN THE VALLEYS...AND U60S TO M70S OVER THE HILLS AND
MTNS.
SATURDAY INTO SUNDAY...SOME TIMING DIFFERENCES FOR NEXT WEEKEND WITH
THE EVOLUTION OF THE POSITIVELY TILTED LONGWAVE TROUGH OVER THE ERN
HALF OF THE CONUS AND THE DEVELOPING SW FLOW ALOFT OVER THE ERN
SEABOARD. THE FRONTAL BOUNDARY ON THE LEADING EDGE OF THE UPPER
TROUGH WILL LIKELY HANG TO THE WEST OF THE COASTAL PLAIN WITH
PERHAPS AREAS OF LOW PRESSURE BRINGING SHOWERS/RAINFALL TO THE FCST
AREA BOTH DAYS ON THE WEEKEND. SOME OF THE GUIDANCE WOULD KEEP SAT
DRY...AND SUNDAY MORE UNSETTLED. THIS UPPER TROUGH SHOULD HELP
STEER LESLIE FAR ENOUGH EAST OF NEW ENGLAND FOR NO SIGNIFICANT
IMPACTS. WE TRENDED CLOSER TO THE LATEST HPC GUIDANCE WITH A LOW
CHANCE OF SHOWERS EACH DAY. HIGHS WILL BE SEASONABLE FOR THE 2ND
WEEKEND OF SEPT.
OVERALL...TEMPS WILL TREND SLIGHTLY ABOVE NORMAL...AND PCPN MAY BE
NEAR NORMAL OR SLIGHTLY ABOVE FOR THE EXTENDED.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
HIGH PRESSURE WILL MOVE EAST OF MAINE TONIGHT. A WARM FRONT WILL
SLOWLY APPROACH FROM THE OHIO VALLEY AND PENNSYLVANIA TOMORROW.
LOW LEVEL MOISTURE WILL GRADUALLY INCREASE FROM THE SOUTHEAST
LATER THIS EVENING AND OVERNIGHT. THIS SHOULD ALLOW STRATUS/MIST
AND MVFR/IFR CONDITIONS TO DEVELOP THROUGHOUT THE AREA BETWEEN
MIDNIGHT AND DAYBREAK. SOME AREAS OF FOG...ESPECIALLY NEAR
KGFL/PSF MAY FORM LATE TONIGHT AS WELL.
THE LOW STRATUS AND/OR ANY FOG WILL DISSIPATE BTWN 12Z-
15Z/MON...HOWEVER A HIGHER STRATUS DECK WILL INCREASE THROUGHOUT
THE DAY...AS A LOW PRESSURE SYSTEM AND ITS WARM FRONT MOVES INTO
THE AREA.
WINDS THIS AFTERNOON AND TONIGHT WILL BE LIGHT TO CALM AND SHIFT TO
MORE OF A SOUTHEAST DIRECTION AFTER 08Z/MON AT 5-10 KTS. WINDS
MAY BE A BIT STRONGER AT KALB DUE TO FUNNELING EFFECTS UP THE
HUDSON RIVER VALLEY.
OUTLOOK...
MON NIGHT...VFR BECOMING MVFR/IFR. CHC -SHRA AND ISOL -TSRA LATE.
TUE...MVFR/IFR. SHRA LIKELY.
WED-THU...VFR/MVFR. CHC -SHRA/-TSRA.
FRI...VFR...NO SIG WX.
&&
.FIRE WEATHER...
HIGH PRESSURE WILL KEEP OUR REGION MAINLY DRY THROUGH TONIGHT.
THE REMNANTS OF ISAAC WILL APPROACH THE AREA ON LABOR
DAY...BRINGING AN INCREASE IN CLOUDINESS AND A THREAT OF SHOWERS
STARTING MONDAY NIGHT AND CONTINUING THROUGH THE MID WEEK PERIOD.
RELATIVE HUMIDITIES WILL INCREASE TO 80 TO 100 PERCENT
TONIGHT...DROP TO 50 TO 70 PERCENT ON MONDAY...RECOVER TO 100
PERCENT MONDAY NIGHT...AND ONLY DROP TO 70 TO 90 PERCENT ON TUESDAY.
WINDS WILL BE LIGHT AND VARIABLE TONIGHT...AND SOUTH TO SOUTHEAST
MONDAY THROUGH TUESDAY.
&&
.HYDROLOGY...
MAINLY DRY WEATHER IS EXPECTED THROUGH LABOR DAY. THE REMNANTS OF
ISAAC WILL INTERACT WITH A FRONT AND BRING RAIN TO OUR AREA
BEGINNING MONDAY NIGHT AND CONTINUING THROUGH THE MID WEEK PERIOD.
AT THIS TIME THE LATEST MODEL GUIDANCE SUGGESTS A WIDESPREAD 1 TO
3 INCHES OF RAIN WITH LOCALLY HIGHER AMOUNTS OF AROUND 4 INCHES
ACROSS SOUTHEAST PORTIONS OF THE AREA. NO RIVER FLOODING IS FORECAST
AT THIS TIME.
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...11/JPV
NEAR TERM...KL/11/JPV
SHORT TERM...11
LONG TERM...WASULA
AVIATION...KL/WASULA
FIRE WEATHER...11
HYDROLOGY...11
AREA FORECAST DISCUSSION
NWS TALLAHASSEE FL
316 PM EDT Mon Sep 3 2012
.NEAR TERM [Through Tonight]...
With the presence of the upper level trough digging into the
region, areas of convection may linger into the overnight hours
longer than is typical for this time of year. The highest rain
chance during the overnight hours is expected to be in southeast
Alabama and portions of southwest Georgia closest to the influence
of the upper level trough. In fact, the model consensus suggests
likely PoPs in that region for the overnight hours and the
official forecast follows suit. Our local 12z hi-res ARW run (12z
RAP initialized with 12z NAM boundary conditions) is somewhat
concerning and indicates that an area of training convection could
develop during the overnight hours across portions of southeast
Alabama and adjacent sections of southwest Georgia. The large
scale environment could support such an occurrence with
precipitable water values forecast around 2.25 inches and
relatively weak steering flow. This is something that we will need
to keep a close eye on through the evening hours. A mention of
heavy rain was added into the forecast for late tonight across
southeast Alabama and adjacent areas of southwest Georgia.
Hopefully our local 18z hi-res ARW run (18z RAP initialized with
12z GFS boundary conditions) will shed some additional light on
this potential scenario. Min temperatures in the low to mid 70s
are expected areawide.
&&
.SHORT TERM [Tuesday Through Wednesday Night]...
The unsettled weather pattern which begins tonight, will continue
right through Wednesday night. A weak trough (loosely associated
with the remnamts of Isaac) is forecast to slide south across the
region over the next several days, with a weak surface low
possibly developing over the northeastern Gulf by Wednesday. With
copious amounts of moisture available (PWAT 2-2.5 inches) along
with modest upper forcing, expect solid coverage of convection
each day. The guidance is in good agreement in showing the
development of multiple convective complexes over the the next 60
hours. However, the exact timing, intensity, and location of these
episodes remains highly uncertain. Given the generally weak flow
aloft, severe weather is not the primary threat. However, there
may be a risk for localized flooding given the tropical nature of
the airmass. Some of the CAMS guidance is showing isolated rainfall
totals of 5-10 inches over the next 48 to 60 hours. Will continue
to monitor the evolution of this system, and a Flash Flood Watch
may need to be considered later if the convective trends
indicated by the hi-res guidance bear out.
Have bumped up PoPs through Wednesday night from previous
forecast, with likely PoPs for much of the area Tuesday and
Wednesday afternoons. Kept southeastern Big Bend a bit drier since
it will be closer to the subsident region on the west side of a
TUTT low over central/south Florida.
&&
.LONG TERM [Thursday through next Monday]...
Rain chances will continue each day with possibly the best chance
late next weekend as models show a very deep trough over the
eastern CONUS with an upper low closing off over the Ohio Valley.
This will send a strong cold front into the southeastern U.S. over
the weekend with a frontal passage possibly by the end of the
forecast period. Would like to see more run to run consistency
before increasing PoPs higher than chance and dropping temps and
dew points too low for the start of next week.
&&
.AVIATION [Beginning 18Z Monday]...
As an upper level trough affects the region, areas of convection
may linger into the overnight hours with the highest chance around
KDHN and KABY. Some MVFR to IFR cigs may also affect the terminals
towards dawn on Tuesday.
&&
.MARINE...
Relatively light southwesterly flow will continue through Tuesday
morning. However, by Tuesday afternoon and evening, the gradient
is forecast to tighten as weak low pressure drops south towards
the Gulf Coast. Exercise caution conditions are possible by
Wednesday morning over the western waters, speading eastward by
Wednesday afternoon. A period of advisory conditions is not out of
the question at some point on Wednesday or Thursday. Winds and
seas should diminish by late in the week as the trough of low
pressure moves east into the Atlantic.
&&
.FIRE WEATHER...
Relative humidity values will remain safely away from critical
levels for the next several days. Thus, no fire weather hazards
are currently anticipated.
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AL...None.
GM...None.
&&
$$
NEAR TERM...Van Dyke
SHORT TERM...Camp
LONG TERM...Barry
AVIATION...Van Dyke
MARINE...Camp
FIRE WEATHER...Van Dyke
AREA FORECAST DISCUSSION
NWS COLUMBIA SC
1032 AM EDT MON SEP 3 2012
.SYNOPSIS...
HIGH PRESSURE OVER THE REGION WILL GIVE WAY TO THE REMNANTS OF
ISAAC AS THE CIRCULATION PUSHES EAST INTO THE TENNESSEE VALLEY.
ATMOSPHERIC MOISTURE WILL BE INCREASING AND SO WILL THE CHANCES OF
RAIN ACROSS THE AREA THROUGH MID WEEK. A FRONT WILL PUSH THROUGH
BY THURSDAY...BEFORE YET ANOTHER UPPER DISTURBANCE APPROACHES FOR
THE WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
THIS MORNING...UPPER LOW CONTAINING REMNANTS OF ISAAC STILL TO
THE WEST. BOTH NAM20 AND RUC13 SHOW UPPER RIDGING WITH NVA OVER
REGION AHEAD OF UPPER SYSTEM. A FEW SHOWERS HAVE DEVELOPED IN
SOUTHEAST GEORGIA AS UPPER RIDGE CONTINUES TO WEAKEN BUT PRECIP
SHOULD BE SLOW TO MOVE INTO AREA DURING THE LATE MORNING AND EARLY
AFTERNOON HOURS. HAVE A 20 POP CENTRAL AND WEST PORTION OF CAE CWA
LATE THIS MORNING INTO EARLY AFTERNOON. JUST 10 PERCENT EAST PART
BUT INCREASE TO 30 PERCENT CHANCE BY EARLY AFTERNOON.
THIS AFTERNOON...THE REMNANTS OF ISAAC WILL DRIFT SOUTHEASTWARD
TOWARDS THE AREA TODAY BUT BECOME LESS DEFINED AS THE UPPER LOW
SHEARS OUT AND BECOMES A WEAK OPEN WAVE BY TONIGHT. ATMOSPHERIC
MOISTURE IS ALREADY QUITE HIGH WITH PWATS CLOSE TO 2 INCHES AS
NOTED ON THE 06Z LAPS SOUNDING AND THESE VALUES WILL INCREASE
FURTHER BY THIS AFTERNOON. MODEL GUIDANCE SUGGESTS SOME UPPER
ENERGY ROTATING AROUND THE CIRCULATION WILL MOVE THROUGH THE
UPSTATE DURING PEAK HEATING AND IS LIKELY TO ORGANIZE SOME
CONVECTION WHICH WILL IMPACT THE WESTERN PORTIONS OF THE FORECAST
AREA.
HI-RES WRF IS IN LINE WITH OPERATIONAL MODELS IN SHOWING A LINE OF
CONVECTION DEVELOPING JUST WEST OF THE FORECAST AREA AND PUSHING
SLOWLY EASTWARD INTO THE WESTERN MIDLANDS AND CSRA LATE AFTERNOON
AND EVENING. DESPITE THE MOS GUIDANCE SHOWING LOW CHANCE POPS TODAY
AND TONIGHT HAVE OPTED TO MAINTAIN PERSISTENCE WITH THE POP FORECAST
AND HOLD LIKELY POPS WESTERN MIDLANDS WITH A GRADIENT TO CHANCE
EASTWARD ACROSS THE FORECAST AREA.
SPC HAS CAE FORECAST AREA IN A SEE TEXT. MODERATE TO STRONG
AFTERNOON INSTABILITY. LIS -4. CAPES AROUND 2000 J/KG BUT WILL
HAVE TO OVERCOME A MID LEVEL CAP. HOWEVER...PULSE STORMS MAY
BECOME STRONG AND APPROACH SEVERE LIMITS IF THERE IS A HIGH
REFLECTIVITY ELEVATED CORE PRESENT IN ANY OF THE STORMS. THE
VIL OF THE DAY IS 69.
TONIGHT...PRECIPITATION IS LIKELY TO LINGER INTO THE OVERNIGHT
HOURS. SEVERE THREAT LOOKS MINIMAL GIVEN A NEARLY MOIST ADIABATIC
SOUNDING PROFILE WITH A WARM CLOUD LAYER DEPTH OVER 10000 FT...AND
THINK HEAVY RAIN FROM TRAINING STORMS COULD BE MORE OF AN ISSUE
THROUGH TONIGHT. TEMPERATURES TODAY WILL AGAIN BE WARM IN THE
LOWER 90S TO AROUND 90 AND BE DEPENDENT ON CLOUD COVER. LOWS
TONIGHT WILL BE LIMITED BY CONVECTIVE DEBRIS CLOUDS AND SHOULD BE
IN THE 70S.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
THE REMNANTS OF ISAAC FURTHER SHEAR AND THE PLUME OF TROPICAL
MOISTURE BECOMES ELONGATED FROM THE GULF COAST NORTHEASTWARD ALONG
THE APPALACHIANS INTO NEW ENGLAND BY TUESDAY NIGHT. THETA-E
MOISTURE TRANSPORT WILL INCREASE OVER THE UPSTATE AND WESTERN
MIDLANDS AND THE INTERACTION WITH DAYTIME HEATING SHOULD YIELD
ANOTHER ROUND OF DIURNAL DEEP MOIST CONVECTION WITHIN A MOIST
ADIABATIC ENVIRONMENT WITH PWATS EXCEEDING 2 INCHES...CLOSE TO 150
PERCENT OF NORMAL. WILL CONTINUE WITH A GRADIENT IN POPS FROM WEST
TO EAST RANGING FROM HIGH CHANCE WESTERN MIDLANDS AND CSRA TO LOW
CHANCE EASTERN MIDLANDS. CHANCES DECREASE DURING THE OVERNIGHT
PERIOD TUESDAY NIGHT...ESPECIALLY IN THE EASTERN PART OF THE
FORECAST AREA WITH THE LOSS OF DAYTIME HEATING. TEMPERATURES SHOULD
BE COOLER ON TUESDAY IN THE MID TO UPPER 80S DUE TO EXTENSIVE CLOUD
COVER IN THE TROPICAL AIRMASS.
ON WEDNESDAY...A WEAK FRONTAL BOUNDARY WILL PUSH TOWARDS THE
FORECAST AREA AND THE AXIS OF DEEP LAYER MOISTURE...LEFTOVER FROM
THE REMNANTS OF ISAAC ALSO SHIFTS TO THE EAST. OPERATIONAL MODELS
DIFFER IN THE TIMING OF THE FRONT PUSHING THROUGH THE AREA...WRF
BEING FASTER AND GFS SLOWER. NEVERTHELESS...WILL AGAIN NEED TO
CARRY MID CHANCE POPS WITH ABUNDANT DEEP LAYER MOISTURE
PRESENT...PWATS CONTINUING OVER 2 INCHES AND MODERATE INSTABILITY.
THE HEAVY RAIN THREAT WILL ALSO CONTINUE THROUGH MID WEEK RESULTING
FROM THE TRAINING OF STORMS WITH HIGH LIQUID WATER CONTENT.
TEMPERATURES WILL REMAIN WARM IN THE MID TO UPPER 80S FOR HIGHS AND
LOWS IN THE 70S.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
LITTLE CHANGE IN THINKING DURING THIS PERIOD. MEDIUM RANGE GUIDANCE
IN REASONABLE AGREEMENT WITH PUSHING A WEAK BOUNDARY THROUGH THE
AREA OR HAVING THE FRONT BECOME DIFFUSE OVER THE AREA THURSDAY WITH
A BREAK IN THE ACTIVE WEATHER FRIDAY. TEMPERATURES WILL REBOUND
BACK TO HIGHS AROUND 90 FOR FRIDAY WITH LOWS FALLING INTO THE UPPER
60S ACROSS MOST OF THE FORECAST AREA AS SOME DRIER AIR WORKS IN FROM
THE NORTHWEST.
BOTH OPERATIONAL RUNS OF THE GFS/ECMWF SHOWING A DYNAMIC UPPER
TROUGH DIGGING ACROSS THE GREAT LAKES AND MIDWESTERN STATES ON
SATURDAY AND CLOSING OFF AN UPPER LOW OVER THE WESTERN OHIO VALLEY
BY SUNDAY. STRONG JET ENERGY ROTATING THROUGH THE BASE OF THE UPPER
TROUGH SHOULD BRING INCREASED DYNAMICS TOWARDS THE FORECAST AREA BY
SUNDAY AND RESULT IN INCREASED CHANCES FOR PRECIPITATION.
&&
.AVIATION /14Z MONDAY THROUGH FRIDAY/...
SCATTERED MID LEVEL CLOUDS STILL LINGERING INTO THE LATE MORNING
HOURS AS LEFTOVER CONVECTIVE DEBRIS CLOUDS WERE OVER AREA THIS
MORNING. OTHERWISE...MOISTURE WILL ADVECT INTO THE FORECAST AREA
AHEAD OF THE TROUGH SLOWLY MOVING INTO THE AREA FROM THE WEST.
EXPECT HEATING AND MIXING WILL HELP CAUSE MAINLY VFR CEILINGS
TODAY INTO THE EVENING. THIS IS SUPPORTED BY MOST OF THE GFS AND
NAM MOS. HOWEVER...RESTRICTIONS WILL OCCUR IN SCATTERED SHOWERS
AND THUNDERSTORMS BUT THIS WAS NOT INCLUDED IN THE TERMINAL
FORECASTS BECAUSE OF TIMING UNCERTAINTY AT THIS TIME. INCREASING
LOW-LEVEL MOISTURE AND DIURNAL COOLING WILL LIKELY RESULT IN MVFR
OR IFR CEILINGS AND VISIBILITIES DEVELOPING LATE TONIGHT.
EXTENDED AVIATION OUTLOOK...EXPECT MAINLY LATE NIGHT AND EARLY
MORNING FOG AND STRATUS...AND SCATTERED AFTERNOON THUNDERSTORMS.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&
$$
07
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
728 PM CDT TUE SEP 4 2012
.MESOSCALE DISCUSSION...
728 PM CDT
CLOSELY MONITORING CONVECTION OVER WESTERN WISCONSIN EARLY THIS
EVENING FOR ANY POTENTIAL IMPACTS ON OUR CWA TONIGHT. CLUSTER OF
STRONG TO SEVERE THUNDERSTORMS OVER SOUTHWEST WISCONSIN APPEARS TO
BE CONGEALING IN A LARGE MASS OF STORMS WHICH COULD RESULT IN
FORMATION OF COLD POOL AND A MORE ACCELERATED MOTION. FORWARD
PROPAGATING CORFIDI VECTORS FROM WRF-NAM AND RUC BOTH SUGGEST
CONVECTION WOULD RACE QUICKLY EAST-SOUTHEAST TOWARD CHGO
METRO...HOWEVER SPC OBJECTIVE MESOANALYSIS DATA SHOWS A REGION OR
MUCH LESSER INSTABILITY AND GREATER INHIBITION OVER SOUTHERN
WISCONSIN. VISIBLE SATELLITE IMAGERY TUES AFTERNOON SHOWED A
DISTINCT ABSENCE OF CUMULUS IN A SWATH FROM NE IL (AHEAD OF LAKE
BREEZE) NNW INTO CENTRAL WISCONSIN...WHICH WOULD LEND SOME CREDENCE
TO THE WEAKER INSTABILITY/STRONGER CAPPING SHOWN IN THE SPC
OBJECTIVE ANALYSIS DATA.
RELATIVELY WEAK LOW LEVEL FLOW SUGGESTS ANY RAPID NORTHEASTWARD
TRANSPORT OF MOISTURE OR INSTABILITY IS UNLIKELY THIS EVENING...SO
WOULD ANTICIPATE CONVECTION TO WEAKEN AS IT PROGRESSES EASTWARD INTO
THE LESS UNSTABLE ENVIRONMENT OVER SOUTHERN WISCONSIN. LOOKING LIKE
A MORE PLAUSIBLE SCENARIO WOULD BE FOR MOST INTENSE VIGOROUS
CONVECTION TO FAVOR THE WESTERN PORTIONS OF THIS DEVELOPING MCS AND
FOR THE STRONGER CELLS TO TEND TO PROPAGATE MORE SOUTHWARD INTO THE
AXIS OF GREATER MOISTURE/INSTABILITY WHICH WAS NICELY DEPICTED BY
THE CUMULUS FIELD THIS AFTERNOON. MODELS REALLY NOT SHOWING ANY
SIGNIFICANT LOW LEVEL JET OR LOW LEVEL WARM AIR ADVECTION OVERNIGHT
SO ITS QUESTIONABLE HOW WELL SUSTAINED THIS CONVECTION WILL BE INTO
THE MID TO LATE EVENING...BUT REGARDLESS GIVEN ITS ALREADY RATHER
CLOSE PROXIMITY FEEL SOME UPWARD ADJUSTMENTS TO POP GRIDS FOR
TONIGHT ARE WARRANTED...ESPECIALLY WESTERN CWA.
IZZI
&&
.DISCUSSION...
307 PM CDT
MAIN FORECAST CONCERN FOR THE NEXT FEW DAYS WILL FOCUS ON THE
INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS TONIGHT AND
TOMORROW ASSOCIATED WITH A COLD FRONT DROPPING SEWD OUT OF THE UPPER
MISSISSIPPI VALLEY.
FOR THE REMAINDER OF THE AFTERNOON AND THIS EVENING...CONDITIONS
WILL REMAIN GENERALLY QUIET...HOWEVER...WITH AMPLE LOW LEVEL
MOISTURE LINGERING OVER THE REGION FOLLOWING THE PASSAGE OF TROPICAL
CYCLONE ISAAC...DAYTIME WARMING COMBINED WITH A LAKE BREEZE BOUNDARY
PUSHING INLAND FROM LAKE MICHIGAN WILL ALLOW FOR AT LEAST A SMALL
CHANCE OF SHOWERS OR THUNDERSTORMS OVER THE AREA THROUGH EARLY THIS
EVENING.
FOR THE LARGER SCALE...A PERSISTENT POLAR LOW CONTINUES TO SIT AND
SPIN OVER NRN MANITOBA WHILE A SERIES OF WEAK IMPULSES TRACK ALONG
THE SRN PERIPHERY. INITIALLY...THE SFC PRESSURE PATTERN REMAINS
VERY DIFFUSE WITH LITTLE SFC FORCING. HOWEVER...BY LATE
TONIGHT...THE SHORT RANGE GUIDANCE IS IN GOOD AGREEMENT ON
INCREASING THE PCPN THREAT AS A STRONG SHORTWAVE DROPS OUT OF THE
NORTHERN ROCKIES AND PUSHES INTO THE NORTHERN PLAINS TONIGHT AND
ACROSS THE UPPER MISSISSIPPI VALLEY TOMORROW. THIS SHORT WAVE WILL
REINFORCE A WEAK SFC COLD FRONT...WHICH WILL PROVIDE THE SFC FORCING
TO IGNITE THUNDERSTORMS. THE MAIN FORECAST CONCERN WITH THIS SYSTEM
WILL BE HOW FAR SOUTH TO EXTEND THE HIGHER POPS THROUGH THE MIDWEST
AND INTO THE MIDDLE MISSISSIPPI VALLEY. WHILE THE STRONGEST FORCING
SHOULD REMAIN TO THE NORTH OF THE LOCAL AREA IN WISCONSIN WITH THE
TRACK OF THE MAIN VORT MAX...THERE SHOULD BE ENOUGH UPPER LEVEL
FORCING EXTENDING SWD...COINCIDENT WITH THE SFC COLD FRONT TO
WARRANT KEEPING LIKELY POPS ACROSS THE CWA BEGINNING EARLY TOMORROW
MORNING OVER THE ROCKFORD AREA AND THEN SPREADING EWD THROUGH THE
DAY AS THE COLD FRONT PUSHES EWD. THE WARM SECTOR ENVIRONMENT
SHOULD BE PRIMED FOR THUNDERSTORMS BY LATE MORNING/EARLY AFTERNOON
AS TEMPERATURES SHOULD REACH INTO THE UPPER 80S TO CLOSE TO 90
DEGREES WITH SFC DEW POINTS IN THE UPPER 60S TO LOWER 70S. DEEP
LAYER INSTABILITY WILL ALSO BE MORE THAN ADEQUATE FOR THUNDERSTORM
DEVELOPMENT AS IS EVIDENCED BY BUFKIT SOUNDS FROM THE NAM12
ADVERTISING CAPE VALUES EXCEEDING 1500 J/KG BY THE LATE MORNING
HOURS AND INCREASING TO ARND 2500 J/KG DURING THE AFTERNOON. THE
GIVEN THE ELEMENTS EXPECTED TO BE IN PLACE TOMORROW...THE ;LATEST
SPC DAY 2 OUTLOOK KEEPS THE CWA IN A SLIGHT RISK AREA FOR SEVERE
THUNDERSTORMS. THE GREATEST THREAT SHOULD BE DURING THE LATE
AFTERNOON HOURS AS THE COLD FRONT CROSSES THE AREA DURING THE TIME
OF PEAK HEATING. THE MAIN SEVERE THREAT SHOULD BE STRONG...DAMAGING
STRAIGHT LINE WINDS GIVEN A RELATIVELY DRY LAYER EXPECTED BETWEEN
850MB-700MB...THOUGH THERE MAY ALSO BE A LARGE HAIL THREAT AS COOLER
AIR MOVES IN ALOFT WITH FREEZING LEVELS DROPPING TO ARND 12KFT.
LOCALLY HEAVY RAINFALL WILL BE LESS OF A CONCERN AS THE COLD FRONT
WILL BE PROGRESSIVE THROUGH THE DAY AND PWATS ARE EXPECTED TO BE 1.5
INCHES OR LESS.
THURSDAY IS SHAPING UP TO BE DRY AND THE NEXT CHANCE FOR PCPN WILL
COME BY EARLY FRIDAY MORNING AS A LONG WAVE TROUGH DROPS INTO THE
UPPER MISSISSIPPI VALLEY. A WEAK FRONT ASSOCIATED WITH THE UPPER
TROUGH IS EXPECTED TO MOVE INTO NWRN IL EARLY FRIDAY...BUT THE MAIN
CONCERN WILL BE SFC WAVE DEVELOPMENT ALONG THE COLD FRONT. THE
LONGER RANGE GUIDANCE IS IN GOOD AGREEMENT ON THE FORMATION OF A
DECENT SFC WAVE ON THE FRONT...BUT THERE IS LESSER AGREEMENT ON THE
STRENGTH AND LOCATION OF THE SFC WAVE DEVELOPMENT. HOWEVER...THERE
IS ENOUGH CONFIDENCE TO CARRY LIKELY POPS FOR THE SRN PORTIONS OF
THE CWA...WITH A CHANCE OF THUNDERSTORMS...BUT LESSER CONFIDENCE TO
THE NORTH...SO WILL ONLY CARRY CHANCE POPS FOR THE NORTHERN PORTIONS
OF THE CWA.
FOR TEMPERATURES...FOLLOWING THE PASSAGE OF THE COLD FRONT
TOMORROW...HIGHS WILL DROP BACK INTO UPPER 70S TO LOWER 80S FOR
THURSDAY. FOR FRIDAY AND SATURDAY...AS THE LONG WAVE UPPER TROUGH
MOVES ACROSS THE REGION...HIGHS SHOULD ONLY BE IN THE MIDDLE 70S FOR
FRIDAY/ THE COOLEST AIR WILL MOVE OVER THE AREA FOR THE WEEKEND
WITH TEMPS ONLY REACHING INTO THE UPPER 60S TO AROUND 70F ON
SATURDAY AND THE LOWER 70S FOR SUNDAY. WEAK UPPER RIDGING SHOULD
RETURN TO THE AREA BY EARLY NEXT WEEK...BRINGING SLIGHTLY WARMER
WEATHER WITH HIGHS IN THE MIDDLE 70S.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 00Z...
* TSRA WEDNESDAY AFTERNOON.
* GUSTY SOUTHWEST WINDS WEDNESDAY. CMS
//DISCUSSION...UPDATED 00Z...
SEVERAL FORECAST CONCERNS THIS PERIOD WITH THE MAIN CONCERN BEING
TSRA TIMING/DURATION WEDNESDAY AFTERNOON.
IN THE SHORT TERM...ISOLATED CONVECTION DEVELOPED OVER PARTS OF
NORTH CENTRAL IL EARLIER THIS AFTERNOON AND HAS SINCE DISSIPATED.
NOT EXPECTING ANY FURTHER DEVELOPMENT BUT IF ANYTHING DOES DEVELOP
IS SHOULD REMAIN ISOLATED AND BRIEF. LINE OF TSRA OVER SOUTHWEST
WI IS EXPECTED TO MOVE EAST AND BEGIN TO WEAKEN LATER THIS
EVENING BUT WILL NEED TO BE MONITORED TO SEE IF IT BEGINS TO TURN
SOUTHEAST AND MOVE INTO NORTHERN IL AND EVEN IF THE CONVECTION
DOESN/T MAKE IT...COULD POSSIBLY BE AND OUTFLOW BOUNDARY PUSHING
INTO NORTHERN IL.
ATTENTION THEN SHIFTS TO THE WEST WITH SOME ELEVATED ACTIVITY
POSSIBLY DEVELOPING OVER IA OVERNIGHT. CONFIDENCE IS FAIRLY LOW
THAT THIS WILL HAPPEN BUT IF ANYTHING DEVELOPS...IT WILL MOVE
GENERALLY EAST AND INTO NORTHWEST IL TOWARD DAYBREAK. EVEN
THEN...IT WOULD LIKELY BE WEAKENING AND THUS HAVE MAINTAINED A DRY
FORECAST INTO MID MORNING.
A COLD FRONT WILL MOVE ACROSS THE AREA WEDNESDAY AFTERNOON AND IT
APPEARS THE BEST CHANCE FOR TSRA WILL BE ALONG/AHEAD OF THIS
FRONT. CONFIDENCE FOR A LINE OF STORMS TO MOVE ACROSS THE
TERMINALS IS GROWING AS IS CONFIDENCE FOR TIMING IN THE MID
AFTERNOON HRS...BUT THIS TIMING AS WELL AS DURATION WILL LIKELY
NEED TO BE TWEAKED WITH LATER FORECASTS. INSTABILITY COMBINED WITH
FAIRLY STRONG WINDS ALOFT WILL LIKELY LEAD TO STRONG/GUSTY WINDS
AT THE TERMINALS WITH THESE STORMS.
LAKE BREEZE NOW WEST OF DPA WILL WASHOUT THIS EVENING WITH
EASTERLY WINDS TURNING SOUTHEAST THIS EVENING THEN SOUTHERLY
OVERNIGHT WITH SPEEDS ALSO DIMINISHING TO 5 KTS OR LESS. WINDS
REMAIN SOUTH/SOUTHWEST INTO WEDNESDAY MORNING AND AS NOTED ABOVE
SOUNDINGS SUGGEST FAIRLY STRONG WINDS ALOFT. HAVE BUMPED WIND
GUSTS UP TO 20KTS MIDDAY BUT SOUNDINGS WOULD SUGGEST GUSTS COULD
BE AS HIGH AS 25KTS. SPEEDS/GUSTS WILL BE DEPENDENT ON CLOUD COVER
AND LOW LEVEL MIXING...THUS CONFIDENCE ISN/T ALL THAT HIGH AS TO
HOW HIGH PREVAILING SPEEDS/GUSTS WILL BECOME.
WHILE THE LOW LEVELS REMAIN QUITE MOIST...MOSTLY SUNNY SKIES TODAY
COMBINED WITH SOME MODEST DRYING...SHOULD PREVENT ANY WIDESPREAD
FOG PROBLEMS TONIGHT...BUT WITH LIGHTER WINDS EXPECTED TOWARD
MORNING COULD SEE SOME LIGHT/SHALLOW GROUND FOG...ESPECIALLY IN
THE USUAL AREAS. CMS
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
* HIGH CONFIDENCE TSRA WILL IMPACT ORD/MDW WEDNESDAY AFTERNOON...
MEDIUM CONFIDENCE ON TIMING...LOW CONFIDENCE ON DURATION.
* MEDIUM CONFIDENCE REGARDING WIND SPEEDS/DIRECTIONS THROUGH THE
PERIOD...LOW CONFIDENCE REGARDING GUSTS WEDNESDAY. CMS
//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...
* THURSDAY...VFR.
* FRIDAY THROUGH SATURDAY...CHANCE OF SHRA. MVFR POSSIBLE.
* SUNDAY...SLIGHT CHANCE OF SHRA.
* MONDAY...VFR.
&&
.MARINE...
323 PM CDT
LIGHT VARIABLE WINDS WILL BEGIN TO FAVOR A SOUTHERLY DIRECTION
TONIGHT AND GRADUALLY FRESHEN AS A COLD FRONT ADVANCES EASTWARD
INTO THE UPPER MIDWEST OVERNIGHT. THE COLD FRONT WILL MOVE ACROSS
NORTHERN LAKE MI BY MID AFTERNOON WED AND ACROSS SOUTHERN LAKE MI
BY MID EVENING...WITH WINDS VEERING TO SOUTHWEST THEN WEST AND
NORTHWEST WITH THE PASSAGE OF THE COLD FRONT. A SECOND COLD FRONT
WILL MOVE ACROSS LAKE MI LATE THU NIGHT AND FRI. WINDS WILL BECOME
SOUTHWESTERLY AS THE FRONT NEARS...THEN VEER TO OUT OF THE WEST
AND NORTHWEST AGAIN WITH THE COLD FRONT PASSAGE. HIGH PRESSURE OF
OVER SASKATCHEWAN AND MANITOBA WILL EXPAND OVER THE PLAINS AND
NORTHERN GREAT LAKES FRIDAY NIGHT. WINDS WILL INCREASE TO STRONG
NORTH TO NORTHEAST BREEZES FOR SAT AND SUN...WITH SOME GUSTS NEAR
GALE FORCE ON SOUTHERN LAKE MI AS THE PRESSURE GRADIENT ACROSS
THE REGION INCREASES BETWEEN THE HIGH PRESSURE RIDGE TO THE N AND
W...AND A LOW MOVING FROM THE MID MS VALLEY UP THE OH VALLEY.
TRS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS LINCOLN IL
1249 PM CDT MON SEP 3 2012
.DISCUSSION...
ISSUED 1039 AM CDT MON SEP 3 2012
15Z/10 AM SURFACE CHART SHOWS 1009MB LOW CENTERED NEAR KEVV...WITH
CLOUD SHIELD EXTENDING ACROSS MUCH OF CENTRAL AND SOUTHEAST ILLINOIS.
FURTHER WEST...ENOUGH SUBSIDENCE IS OCCURRING ON THE BACK SIDE OF
THE SYSTEM TO ALLOW SKIES TO BECOME PARTLY TO MOSTLY SUNNY ALONG
AND WEST OF I-55. WITH ONLY VERY SLOW EASTWARD MOVEMENT...THINK
CLOUDS WILL PERSIST ACROSS THE E/SE KILX CWA THROUGH THE AFTERNOON.
12Z HRRR SUGGESTS A FEW SHOWERS MAY DEVELOP ACROSS THIS AREA AS
WELL...HOWEVER AREAL COVERAGE WILL BE MINIMAL. HAVE UPDATED
FORECAST TO REMOVE MENTION OF THUNDER...OPTING INSTEAD TO GO WITH
ISOLATED TO SCATTERED LIGHT SHOWERS ALONG AND EAST OF I-57. HIGH
TEMP FORECAST APPEARS TO BE ON TRACK...WITH COOLEST READINGS IN
THE LOWER TO MIDDLE 80S ACROSS THE CLOUD-COVERED EAST/SOUTHEAST
AND UPPER 80S FURTHER WEST. ZONE UPDATE HAS ALREADY BEEN ISSUED.
BARNES
&&
.AVIATION...
ISSUED 1249 PM CDT MON SEP 3 2012
CLOUD SHIELD ASSOCIATED WITH DEPARTING LOW PRESSURE HAS NOW SHIFTED
SOUTHEAST OF THE TERMINALS...HOWEVER ENOUGH LOW-LEVEL MOISTURE
REMAINS TO SUPPORT SCT-BKN MVFR CEILINGS THROUGH 20/21Z. AFTER
THAT...MOSTLY CLEAR SKIES WILL BE NOTED THIS EVENING BEFORE A WEAK
UPPER-LEVEL DISTURBANCE BEGINS TO SPREAD MID/HIGH CLOUDS BACK INTO
THE AREA OVERNIGHT INTO TUESDAY MORNING. 12Z NAM/GFS BOTH SUGGEST
SCT SHOWERS WITH THIS SYSTEM...HOWEVER CONFIDENCE CONCERNING EXACT
AREAL COVERAGE AND TIMING IS LOW...SO WILL ONLY FEATURE A PERIOD
OF VCSH AT ALL SITES AFTER 08/09Z. FORECAST SOUNDINGS ALSO INDICATE
THE POTENTIAL FOR AREAS OF FOG TONIGHT...HOWEVER INCREASING HIGH
CLOUDS MAY MITIGATE THIS THREAT. AT THIS POINT...HAVE INCLUDED
3-4SM VISBYS ACROSS THE BOARD...BUT THESE MAY NEED TO BE LOWERED
FURTHER IF CLOUD COVER DOES NOT MATERIALIZE AS CURRENTLY FORECAST.
BARNES
&&
.PREV DISCUSSION...
ISSUED 330 AM CDT MON SEP 3 2012
SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT
1008 MB LOW PRESSURE (REMNANTS OF ISAAC) WAS OVER FAR SE IL
BETWEEN LAWRENCEVILLE AND EVANSVILLE AND CONTINUED TO BRING
LOW CLOUDS TO AREAS FROM I-55 SE EARLY THIS MORNING WHILE NEARLY
CLEAR SKIES OVER THE IL RIVER VALLEY WITH A LIGHT FOG SO FAR.
GALESBURG VSBY WAS DOWN TO 2 MILES. HUMID AIRMASS LINGERS OVER
CENTRAL/SE IL WITH DEWPOINTS STILL IN THE LOWER 70S...EXCEPT 65F
AT GALESBURG. RADAR MOSAIC SHOWS MOST LIGHT SHOWERS HAVE
TEMPORARILY ENDED OVER CENTRAL/SE IL EARLY THIS MORNING...THOUGH
COULD BE A FEW SPRINKLES/DRIZZLE AROUND IN THE LOW CLOUDS FROM I-55
SE.
MODELS CONTINUE SLOW DRIFT OF LOW PRESSURE FROM FAR SE IL INTO
WESTERN KY TODAY AND STILL CLOSE ENOUGH TO BRING A CHANCE OF
SHOWERS OVER EASTERN IL LATER THIS MORNING AND AFTERNOON AND
PERHAPS AN ISOLATED THUNDERSTORMS IN SE IL THIS AFTERNOON. MORE
LOW CLOUDS LINGER OVER EASTERN IL AS WELL AND KEEP TEMPS A BIT
COOLER THERE. HIGHS IN THE MID 80S TO UPPER 80S WITH WARMER
READINGS WEST WHERE MORE SUNSHINE EXPECTED. WILL MENTION PATCHY
FOG FROM I-55 WEST UNTIL MID MORNING.
SOME FOG WILL LIKELY DEVELOP AGAIN OVERNIGHT AS LOW CLOUDS
DECREASE AND LINGER LONGER ALONG THE INDIANA BORDER. A WEAK
DISTURBANCE AND WEAKENING FRONT MOVE INTO NORTHERN/CENTRAL IL TUE
AND TO BRING ISOLATED SHOWERS AND THUNDERSTORMS BACK INTO AREA.
SPC HAS MUCH OF CENTRAL/SE IL IN A SLIGHT RISK OF SEVERE STORMS
WED AFTERNOON/EARLY WED EVENING UNTIL SUNSET. THIS DUE TO A STRONG
UPPER LEVEL SHORT WAVE AND COLD FRONT MOVING SE THROUGH IL. VERY
WARM AND HUMID AHEAD OF THIS FRONT THROUGH WED AND THEN TURNING
COOLER AND LESS HUMID THEREAFTER.
LONG TERM...THURSDAY THROUGH SUNDAY
EXTENDED MODELS CONTINUE TO BE PROGRESSIVE WITH YET ANOTHER FAIRLY
STRONG UPPER LEVEL DISTURBANCE TRACKING ESE INTO THE REGION LATE
THIS WEEK AND RETURNING A GOOD CHANCE OF SHOWERS AND ISOLATED
THUNDERSTORMS OVERNIGHT THU NIGHT INTO SAT. MODELS ALSO CONTINUE
TO SHOW A STRONG UPPER LEVEL TROF AND POSSIBLE CUTOFF LOW TAKING
SHAPE OVER THE GREAT LAKES/OHIO VALLEY REGION THIS WEEKEND...BRINGING
BELOW NORMAL TEMPERATURES ALONG WITH DIURNALLY ENHANCED CHANCES OF
SHOWERS AND CLOUDS DURING THE AFTERNOON HOURS.
KH
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS LINCOLN IL
1039 AM CDT MON SEP 3 2012
.DISCUSSION...
ISSUED 1039 AM CDT MON SEP 3 2012
15Z/10 AM SURFACE CHART SHOWS 1009MB LOW CENTERED NEAR KEVV...WITH
CLOUD SHIELD EXTENDING ACROSS MUCH OF CENTRAL AND SOUTHEAST ILLINOIS.
FURTHER WEST...ENOUGH SUBSIDENCE IS OCCURRING ON THE BACK SIDE OF
THE SYSTEM TO ALLOW SKIES TO BECOME PARTLY TO MOSTLY SUNNY ALONG
AND WEST OF I-55. WITH ONLY VERY SLOW EASTWARD MOVEMENT...THINK
CLOUDS WILL PERSIST ACROSS THE E/SE KILX CWA THROUGH THE AFTERNOON.
12Z HRRR SUGGESTS A FEW SHOWERS MAY DEVELOP ACROSS THIS AREA AS
WELL...HOWEVER AREAL COVERAGE WILL BE MINIMAL. HAVE UPDATED
FORECAST TO REMOVE MENTION OF THUNDER...OPTING INSTEAD TO GO WITH
ISOLATED TO SCATTERED LIGHT SHOWERS ALONG AND EAST OF I-57. HIGH
TEMP FORECAST APPEARS TO BE ON TRACK...WITH COOLEST READINGS IN
THE LOWER TO MIDDLE 80S ACROSS THE CLOUD-COVERED EAST/SOUTHEAST
AND UPPER 80S FURTHER WEST. ZONE UPDATE HAS ALREADY BEEN ISSUED.
BARNES
&&
.AVIATION...
ISSUED 630 AM CDT MON SEP 3 2012
COVERAGE OF IFR/MVFR CIGS AND FOG THIS MORNING THE MAIN FORECAST
CHALLENGE. WEAK LOW PRESSURE TO OUR SOUTHEAST WILL CONTINUE TO
SLOWLY MOVE AWAY FROM THE MIDWEST TODAY. OUR AREA WILL STILL BE
UNDER THE INFLUENCE OF SOME WEAK CYCLONIC FLOW AND ABUNDANT LOW
LEVEL MOISTURE LEFT OVER FROM THE SYSTEM RESULTING IN THE LOWER
CLOUDS AND FOG THIS MORNING...AND THEN AT LEAST SOME BKN MVFR CIGS
THIS AFTN. ISOLATED SHOWERS WILL BE POSSIBLE AT DEC AND CMI MAINLY
THIS AFTN SO WILL COVER THAT WITH A VCSH IN BOTH LOCATIONS.
SETUP APPEARS TO BE MORE FAVORABLE FOR FOG LATE TONIGHT AS WEAK
HIGH PRESSURE SETTLES INTO THE AREA BRINGING LIGHT WINDS AND CLEAR
SKIES...AT LEAST TO START THE EVENING OUT. HOWEVER...WITH THE
ABUNDANT LOW LEVEL MOISTURE AND LIGHT WIND FLOW...IT SEEMS THAT
FOG IS A DISTINCT POSSIBILITY OVERNIGHT. WILL BRING IN THE LOWER
VSBYS/CIGS AFTR 05Z MOST AREAS. SFC WINDS WILL BE OUT OF THE NE
TODAY AT AROUND 10 KTS WITH A FEW GUSTS UP TO 20 KTS POSSIBLE BY
LATE MORNING INTO THE AFTN HOURS. LIGHT NNE WINDS ARE EXPECTED
TONIGHT.
SMITH
&&
.PREV DISCUSSION...
ISSUED 330 AM CDT MON SEP 3 2012
SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT
1008 MB LOW PRESSURE (REMNANTS OF ISAAC) WAS OVER FAR SE IL
BETWEEN LAWRENCEVILLE AND EVANSVILLE AND CONTINUED TO BRING
LOW CLOUDS TO AREAS FROM I-55 SE EARLY THIS MORNING WHILE NEARLY
CLEAR SKIES OVER THE IL RIVER VALLEY WITH A LIGHT FOG SO FAR.
GALESBURG VSBY WAS DOWN TO 2 MILES. HUMID AIRMASS LINGERS OVER
CENTRAL/SE IL WITH DEWPOINTS STILL IN THE LOWER 70S...EXCEPT 65F
AT GALESBURG. RADAR MOSAIC SHOWS MOST LIGHT SHOWERS HAVE
TEMPORARILY ENDED OVER CENTRAL/SE IL EARLY THIS MORNING...THOUGH
COULD BE A FEW SPRINKLES/DRIZZLE AROUND IN THE LOW CLOUDS FROM I-55
SE.
MODELS CONTINUE SLOW DRIFT OF LOW PRESSURE FROM FAR SE IL INTO
WESTERN KY TODAY AND STILL CLOSE ENOUGH TO BRING A CHANCE OF
SHOWERS OVER EASTERN IL LATER THIS MORNING AND AFTERNOON AND
PERHAPS AN ISOLATED THUNDERSTORMS IN SE IL THIS AFTERNOON. MORE
LOW CLOUDS LINGER OVER EASTERN IL AS WELL AND KEEP TEMPS A BIT
COOLER THERE. HIGHS IN THE MID 80S TO UPPER 80S WITH WARMER
READINGS WEST WHERE MORE SUNSHINE EXPECTED. WILL MENTION PATCHY
FOG FROM I-55 WEST UNTIL MID MORNING.
SOME FOG WILL LIKELY DEVELOP AGAIN OVERNIGHT AS LOW CLOUDS
DECREASE AND LINGER LONGER ALONG THE INDIANA BORDER. A WEAK
DISTURBANCE AND WEAKENING FRONT MOVE INTO NORTHERN/CENTRAL IL TUE
AND TO BRING ISOLATED SHOWERS AND THUNDERSTORMS BACK INTO AREA.
SPC HAS MUCH OF CENTRAL/SE IL IN A SLIGHT RISK OF SEVERE STORMS
WED AFTERNOON/EARLY WED EVENING UNTIL SUNSET. THIS DUE TO A STRONG
UPPER LEVEL SHORT WAVE AND COLD FRONT MOVING SE THROUGH IL. VERY
WARM AND HUMID AHEAD OF THIS FRONT THROUGH WED AND THEN TURNING
COOLER AND LESS HUMID THEREAFTER.
LONG TERM...THURSDAY THROUGH SUNDAY
EXTENDED MODELS CONTINUE TO BE PROGRESSIVE WITH YET ANOTHER FAIRLY
STRONG UPPER LEVEL DISTURBANCE TRACKING ESE INTO THE REGION LATE
THIS WEEK AND RETURNING A GOOD CHANCE OF SHOWERS AND ISOLATED
THUNDERSTORMS OVERNIGHT THU NIGHT INTO SAT. MODELS ALSO CONTINUE
TO SHOW A STRONG UPPER LEVEL TROF AND POSSIBLE CUTOFF LOW TAKING
SHAPE OVER THE GREAT LAKES/OHIO VALLEY REGION THIS WEEKEND...BRINGING
BELOW NORMAL TEMPERATURES ALONG WITH DIURNALLY ENHANCED CHANCES OF
SHOWERS AND CLOUDS DURING THE AFTERNOON HOURS.
KH
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
752 PM EDT TUE SEP 4 2012
.AVIATION...00Z TAFS
TONIGHTS CONDITIONS ARE QUITE SIMILAR TO LAST NIGHT AND EXPECT
SIMILAR CONDITIONS POSSIBLE AT BOTH TERMINALS. KFWA SAW
VISIBILITIES VERY NEAR ZERO BETWEEN 12Z AND 13Z THIS MORNING AND
CANNOT RULE OUT SIMILAR CONDITIONS TOMORROW MORNING. RISK FOR
IFR/LIFR FOG AT KSBN IS MUCH LESS CONSIDERING LOWER CROSSOVER
TEMPS AND WARMER LOW TEMPERATURES EXPECTED. ALSO...UPSTREAM
CONVECTION ACROSS WESTERN WISCONSIN COULD BRING CIRRUS DECK OVER
THE TERMINAL AFTER 06Z. REMOVED IFR TEMPO GROUP AT KSBN DUE TO
THIS DECREASED LIKELIHOOD OF DENSE FOG AND REPLACED WITH MVFR VIS
AFTER 07Z.
&&
.PREV DISCUSSION... /ISSUED 339 PM EDT TUE SEP 4 2012/
SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT.
SEVERAL CONCERNS TO DEAL WITH OVER THE NEXT 36 HOURS FROM
CONVECTION/SVR WX TO FOG.
WEAK FRONTAL BOUNDARY WAS ROUGHLY LOCATED FROM MONTICELLO TO FORT
WAYNE TO DEFIANCE WITH ISOL TO SCT SHOWERS STRUGGLING TO TAKE SHAPE
ALONG WITH GIVEN WEAK CONVERGENCE AND LIMITED INSTABILITY. WILL KEEP
A PRE 1ST PERIOD TO ADDRESS THIS ACTIVITY WHICH SHOULD EXIT BY 00Z.
WITH MOIST BOUNDARY LAYER AND LITTLE CHANCE FOR MIXING ACROSS THE
AREA TODAY...FOG/STRATUS POTENTIAL WILL REMAIN HIGH ACROSS MOST IF
NOT ALL OF THE FORECAST AREA. COULD SEE WIDESPREAD DENSE FOG LATER
TONIGHT IN MANY SPOTS WITH TEMPS FALLING PASS CROSSOVER TEMPS IN THE
UPPER 60S TO AROUND 70 AND CALM WINDS/CLEAR SKIES. POTENTIAL ISSUES
ARISE FROM ANTICIPATED UPSTREAM CONVECTION ACROSS MINN/WI/IOWA.
SEVERAL RUNS OF THE HRRR HAVE SHOWN DEVELOPMENT ACROSS THIS AREA
DROPPING TOWARDS POSSIBLE WESTERN PARTS OF THE FORECAST AREA LATER
TONIGHT/WEDS MORNING...POSSIBLY CAUSING ISSUES WITH FOG DEVELOPMENT.
FOR NOW...HAVE BUMPED UP WORDING IN ZONES TO PATCHY DENSE FOG AND
WILL DEFER TO EVENING/OVERNIGHT SHIFTS TO ADJUST BASED ON UPSTREAM
TRENDS.
STRONGER UPPER LEVEL TROUGH AND SFC COLD FRONT STILL POISED TO MOVE
INTO THE REGION WEDS/WEDS NGT. STRONG DYNAMICS WILL ACCOMPANY THE
SYSTEM WITH A FAVORABLE TIMING OF LIFT AND MSTR CONVERGENCE IN THE
LATE AFTERNOON/EARLY EVENING. GIVEN 0-6 KM SHEAR IN THE 30 TO 40 KT
RANGE SVR THREAT IS STILL POSSIBLE...IF SUFFICIENT HEATING CAN OCCUR
AHEAD OF THE ACTUAL FRONT. THE FLY IN THE OINTMENT FOR THIS MAY BE
ANY LATE NIGHT/MORNING CONVECTION NOTED ABOVE THAT COULD STABILIZE
THE AREA THROUGH OPTIMAL PEAK HEATING...THEREBY REDUCING CHANCES FOR
SVR WX. DO STILL FEEL THAT CONVECTION WILL FIRE TO THE WEST ALONG
THE FRONT IN ILLINOIS DURING THE AFTERNOON AND MOVE EAST TOWARDS THE
AREA. HAVE THEREFORE CAUTIOUSLY HELD WITH LIKELY POPS IN NW AREAS
WEDS AFTERNOON BUT FOR NOW BACKED OFF ON POP TIMING EARLIER IN THE
DAY ASSUMING THAT MODEL INDICATIONS OF IA/WI/MN COMPLEX DYING AS IT
APPROACHES OCCUR. THIS SAME REASONING WARRANTS A SLIGHT INCREASE IN
POPS WEDS NGT WITH POTENTIAL FOR SOMEWHAT SLOWER DEPARTURE OF
PRECIP...BUT NOT A RAMP UP TO LIKELY IN EASTERN AREAS GIVEN LESS
FAVORABLE TIME FRAME FOR CONVECTION TO MAINTAIN ITSELF UNLESS
ALREADY WELL ESTABLISHED.
LONG TERM...
THURSDAY THROUGH TUESDAY...THE MAIN CHALLENGES THIS PERIOD CONCERN
THE CHANCES FOR THE DEVELOPMENT OF A CUT OFF LOW OVER THE OHIO
VALLEY REGION THIS WEEKEND. ADDITIONAL CHALLENGES INCLUDE THE TIMING
AND EXTENT OF PRECIPITATION AND THE EFFECT ON TEMPERATURES IF THE
LOW DEVELOPS AND LINGERS OVER OR NEAR THE REGION. FOR THIS
PACKAGE...FAVOR THE ECMWF...ALTHOUGH THE 12Z RUN WAS AN OUTLIER
COMPARED TO THE PAST SEVERAL RUNS. THE 12Z ECMWF RUN WAS NOT USED
FOR THIS PACKAGE. THE PAST SEVERAL ECMWF RUNS HAVE HAD REASONABLE
RUN TO RUN CONSISTENCY. AS A WHOLE THE NEW 12Z GFS SOLUTION HAS
TRENDED TOWARD THE SLOWER...FARTHER WEST 00Z ECMWF SOLUTION.
ALSO...THE 00Z ECMWF HAS HAD BETTER SUPPORT WITH THE SURFACE
LOW/SURFACE REFLECTION CLOSER TO THE UPPER LOW THAN THE GFS. HAVE
RAISED RAIN CHANCES FRIDAY NIGHT GIVEN REASONABLE CONFIDENCE IN THE
TIMING OF THE SHORT WAVE TROF AND ASSOCIATED COLD FRONT. FOR THE
REST OF THE PERIOD...WENT WITH PERSISTENCE AND ATTEMPTED TO HOLD TO
THE PREVIOUS FORECAST WITH DRY CONDITIONS STARTING SUNDAY NIGHT.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
SHORT TERM...FISHER
LONG TERM...SKIPPER
AVIATION...BENTLEY
AREA FORECAST DISCUSSION
NWS DES MOINES IA
622 PM CDT TUE SEP 4 2012
...UPDATED AVIATION DISCUSSION...
.SHORT TERM /TONIGHT/...
PRIMARY CONCERN TONIGHT WILL BE CONVECTIVE TRENDS BUT CONFIDENCE IN
THAT EVOLUTION IS DECREASING AS MOST MODELS...HIGH RES EXPLICIT AND
PARAMETERIZED...ARE CURRENTLY OVERZEALOUS IN THEIR DEPICTION OF
PRECIP. PRESENT SITUATION HAS 80KT JET FROM ROCKIES INTO IA
ENHANCING DEEP/EFFECTIVE SHEAR. LITTLE IN THE WAY OF LARGE SCALE
FORCING NOTED IMMEDIATELY UPSTREAM HOWEVER WITH RAP ANALYSIS AND
WATER VAPOR IMAGERY FAIRLY BENIGN. ONLY SIGN OF LARGER SCALE UPWARD
VERTICAL MOTION /UVM/ SEEMS TO BE ACROSS CENTRAL NE NEAR H85/H7
SHORT WAVE PER VISIBLE IMAGERY. OUR FORECAST AREA SEEMS PRIMED FOR
DEVELOPMENT THERMODYNAMICALLY WITH UNCAPPED 2000-4000 J/KG MLCAPES.
HOWEVER SPOTTY CONVERGENCE AND LITTLE TO NO UVM OVERHEAD HAVE
RESULTED IN NO DEVELOPMENT AS OF YET. SMALL CELL ALONG HIGHWAY 20
DISSIPATED WHICH IS A SIGNAL THAT WE ARE NOT READY TO GO SURFACE
BASED AND/OR HAVE INSUFFICIENT UPPER LEVEL SUPPORT.
AT THE MOMENT FEEL THAT CONVECTIVE INITIATION IS GOING TO WAIT FOR
AFOREMENTIONED NE UVM ALONG WITH INCREASED SYNOPTIC SCALE FORCING
AHEAD OF MT/DAKOTAS SHORT WAVE AS IT MOVES EAST THIS EVENING.
ECMWF/GFS QG FORCING INCREASES AS IT REACHES MN BY 06Z. 18Z RAP
SUGGESTS WEAKLY CAPPED ELEVATED CAPES 2000 J/KG OR MORE WILL BE IN
PLACE AND CERTAINLY CAPABLE OF SUPPORTING SEVERE WEATHER CONSIDERING
OUR PROXIMITY TO THE JET. DCAPES SHOULD REMAIN QUITE HIGH
OVERNIGHT WITH SOUNDINGS SHOWING PLENTY OF DRY AIR BELOW 3KM. THUS
EXPECT NE CONVECTION TO SLOWLY DEVELOP AND MATURE AS IT REACHES IA
MUCAPE AXIS WITH DAMAGING WINDS AND HAIL QUITE POSSIBLE.
.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
FORECAST CONCERNS FOR WEDNESDAY WILL DEAL WITH A STRONG COLD FRONT
PUSHING ACROSS THE FORECAST AREA DURING THE MORNING AIDED BY A
POTENT SHORT WAVE SWEEPING ACROSS THE NORTHERN PLAINS INTO IA. MOST
OF THE CAPE AND SHEAR ARE AHEAD OF THE BOUNDARY SO ONGOING
CONVECTION FROM THE OVERNIGHT WILL AFFECT THE EASTERN HALF OR SO OF
THE FORECAST AREA. BEHIND THE FRONT MUCH COOLER AND DRIER AIR WILL
PUSH INTO CENTRAL IOWA DURING THE AFTERNOON SO ANY THUNDERSTORM
THREAT IN THE AFTERNOON WILL BE CONFINED TO THE FAR SOUTHEAST
PORTION OF CENTRAL IOWA ON EAST. BEYOND WEDNESDAY WE BEGIN OUR
SLIDE IN TEMPS AS HIGH PRESSURE BUILDS IN WEDNESDAY NIGHT THROUGH
LATE THURSDAY. WARM ADVECTION OCCURS THURSDAY NIGHT AHEAD OF THE
NEXT SYSTEM TO AFFECT THE AREA. ON FRIDAY THETA ADVECTION INCREASES
AND A SECOND SHORT WAVE ROTATES THROUGH THE NORTHERN AND CENTRAL
PLAINS BRINGING AND ANOTHER FRONT WILL PUSH ACROSS IOWA BRINGING A
REINFORCING SHOT OF COLD AIR. SHOWERS AND ISOLATED THUNDERSTORMS
WILL OCCUR WITH THIS FOLLOWED BY SOME VERY COOL AIR. TEMPERATURES
OVER THE WEEKEND WILL ACTUALLY BE BELOW NORMAL BUT IT WILL BE DRY.
&&
.AVIATION...05/00Z
AFTERNOON CONVECTIVE DEVELOPMENT OCCURRED NE AND WEST OF
SITES...THEREFORE HAVE DELAYED ONSET OF PRECIPITATION UNTIL
LATER...WHEN DEVELOPMENT IN NEBRASKA PUSHES EAST INTO AREA. HAVE
ONLY INCLUDED TS MENTION AT KFOD AND KDSM WITH DELAY IN TIMING...BUT
COULD SEE AT ALL SITES. CEILINGS WILL REMAIN PRIMARILY VFR WITH HIGH
BASED STORMS...BUT COULD SEE PERIODS OF MVFR OR LOWER CEILINGS IF
STORMS AFFECT SITES. NOT ENOUGH CONFIDENCE TO INCLUDE MENTION ATTM.
AS SYSTEM PUSHES EAST...CONDITIONS WILL BE DRY WITH VFR CEILINGS
WEDNESDAY AFTERNOON. HOWEVER...WINDS WILL BE GUSTY.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...SMALL
LONG TERM...FAB
AVIATION...AWB
AREA FORECAST DISCUSSION
NWS GOODLAND KS
205 PM MDT MON SEP 3 2012
.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 200 PM MDT MON SEP 3 2012
LATEST WV IMAGERY SHOWS A NARROW BAND OF SUBSIDENCE OVER EASTERN
COLORADO MOVING INTO THE TRI-STATE AREA BEHIND THE UPPER LEVEL
TROUGH THAT BROUGHT LIGHT RAINFALL TODAY. RUC ANALYSIS HAS A SECOND
SHORT WAVE TROUGH FOLLOWING THE SUBSIDENCE BEHIND THE INITIAL SHORT
WAVE. AT THE SURFACE THE COLD FRONT FROM YESTERDAY EXTENDS FROM
SOUTHWEST KANSAS NORTHEAST TO IOWA. ANY STORM ACTIVITY THAT DEVELOPS
ALONG THE FRONT SHOULD BE WELL SOUTH OF THE AREA. OTHERWISE A
SUBTLE SURFACE TROUGH WAS LOCATED BETWEEN WRAY AND SAINT
FRANCIS...WHICH MAY SERVE TO HELP FOCUS CONVECTION OVER THE
NORTHWEST LATE THIS AFTERNOON AND THIS EVENING.
EARLY THIS EVENING SURFACE CONVERGENCE WILL DEVELOP OVER THE
NORTHWEST PART OF THE AREA BELOW A 700-500MB SHORT WAVE TROUGH.
THE DEEP LIFTING WILL GIVE THE BEST SHOT FOR RAINFALL TO REACH THE
GROUND. MEANWHILE THERE MAY BE SOME LINGERING STORMS IN THE HILL
CITY TO MCCOOK AREA...AS THE 700-500MB SHORT WAVE TROUGH THAT
BROUGHT RAIN EARLIER TODAY DEPARTS THE AREA. AS THE NIGHT
PROGRESSES PRECIP. CHANCES SHIFT FROM THE NORTHWEST TO THE SOUTH
AS A ANOTHER SHORT WAVE TROUGH MOVES ACROSS THE AREA. WITH A DEEP
DRY LAYER IN PLACE...AM NOT TOO CONFIDENT ANYTHING WILL REACH THE
GROUND.
TUESDAY ANOTHER SHORT WAVE TROUGH WILL MOVE THROUGH THE AREA.
DURING THE LATE MORNING THROUGH THE AFTERNOON A PRE-FRONTAL TROUGH
WILL DEVELOP AT THE SURFACE BELOW THE SHORT WAVE TROUGH. LIFT ALONG
THE SURFACE AND MID LEVEL TROUGH INCREASE THROUGH THE DAY. WITH
STRONGER LIFT OCCURRING DURING THE AFTERNOON HAVE INCREASED PRECIP.
CHANCES ALONG AND EAST OF THE SURFACE TROUGH. THESE AREAS WILL BE MORE
LIKELY TO HAVE STRONG TO SEVERE THUNDERSTORMS DUE TO THE BETTER
INSTABILITY.
THE 0-6KM SHEAR WILL BE AROUND 30 TO 35 KTS FOR THE PERIOD...WHICH
WILL SUPPORT ORGANIZED STORM STRUCTURE WITH PROLONGED UPDRAFTS. AM
THINKING THE MAIN THREAT WITH THESE STORMS WILL BE STRONG TO SEVERE
WIND GUSTS DUE TO THE HIGH CLOUD BASES.
TEMPERATURES WILL BE SIMILAR TO LAST NIGHT AND TODAY...WITH LOWS IN
UPPER 50S TO LOW 60S AND HIGHS IN THE 90S.
.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 131 PM MDT MON SEP 3 2012
TUESDAY NIGHT-THURSDAY...WILL KEEP A SMALL CHANCE OF PRECIPITATION
IN THE FORECAST EARLY TUESDAY NIGHT BEFORE DRIER AIR WORKS INTO
THE AREA UNDER NORTHWEST FLOW ALOFT THROUGH EARLY THURSDAY
MORNING. NOT TERRIBLY EXCITED ABOUT PRECIPITATION CHANCES THURSDAY
AFTERNOON DESPITE MOISTURE AVAILABILITY AS DYNAMICS RATHER WEAK.
TRIMMED POPS DOWN JUST A BIT. HIGH TEMPERATURES WEDNESDAY IN THE
LOW TO MID 80S...WARMING INTO THE UPPER 80S TO LOW 90S THURSDAY.
LOWS IN THE 50S TO LOW 60S.
THURSDAY NIGHT-FRIDAY NIGHT...PRECIPITATION CHANCES WILL SLOWLY
INCREASE THROUGH FRIDAY AS AN UPPER TROUGH AND COLD FRONT
APPROACH THEN MOVE THROUGH THE AREA. PRECIP CHANCES DECREASE FROM
NORTH TO SOUTH FRIDAY NIGHT AS THE SYSTEM MOVES OUT OF THE AREA
AND STABLE HIGH PRESSURE MOVES IN. HIGH TEMPERATURES FRIDAY 75-80.
LOWS THURSDAY NIGHT IN THE LOW 60S COOLING INTO THE LOW TO MID
50S FRIDAY NIGHT BEHIND THE FRONT.
SATURDAY-MONDAY...DRY. HIGH TEMPERATURES SATURDAY IN THE MID TO
UPPER 70S...WARMING INTO THE MID 80S TO AROUND 90 BY MONDAY.
OVERNIGHT LOWS NEAR TO SLIGHTLY ABOVE NORMAL.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1108 AM MDT MON SEP 3 2012
VFR CONDITIONS FORECAST FOR THE 18Z TAFS. AREAS OF SHOWERS AND
THUNDERSTORMS SOUTHWEST OF KGLD ARE EXPECTED TO DIMINISH BY MID
AFTERNOON. WILL MONITOR AND AMEND KGLD IF NEEDED. KMCK SHOULD BE
ON THE WEST SIDE OF ANY PRECIPITATION. OTHERWISE WINDS WILL BE
LIGHT THROUGH THE AFTERNOON...WITH MAYBE A FEW GUSTS UP TO 15KTS.
TONIGHT STORMS SHOULD REMAIN WEST OF THE TAF SITES OR DIMINISH
BEFORE MOVING OVER THEM. LATE TUESDAY MORNING STORM COVERAGE IS
TOO ISOLATED FOR THE SITES TO MENTION IN THE TAF AT THIS TIME.
&&
.FIRE WEATHER...
ISSUED AT 200 PM MDT MON SEP 3 2012
TUESDAY AFTERNOON AREAS NORTH OF A KIT CARSON TO MCCOOK LINE WILL
HAVE RELATIVE HUMIDITIES DROP TO AROUND 15 PERCENT DURING THE
AFTERNOON. IN ADDITION WIND GUSTS AROUND 20 MPH CAN BE EXPECTED.
WHILE THIS IS BELOW ISSUANCE CRITERIA...CARE SHOULD BE TAKEN FOR
ANY OUTDOOR BURNING.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...JTL
LONG TERM...99
AVIATION...JTL
FIRE WEATHER...JTL
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
346 PM EDT MON SEP 3 2012
.SYNOPSIS...
THE REMNANT LOW OF ISAAC WILL SLOWLY MOVE ACROSS THE UPPER OHIO
VALLEY THROUGH TUESDAY NIGHT, BRINGING THUNDERSTORMS AND HEAVY RAIN
TO THE AREA. THE SYSTEM WILL MOVE EAST OF THE AREA TUESDAY NIGHT
INTO EARLY WEDNESDAY, WITH A BREAK FROM SHOWERS AS HIGH PRESSURE
BUILDS IN FOR WEDNESDAY. A COLD FRONT WILL CROSS THE AREA ON
THURSDAY, RETURNING THE CHANCE FOR SHOWERS AND THUNDERSTORMS.
&&
.NEAR TERM /THROUGH TONIGHT/...
THE LATEST RAP MID-LEVEL ANALYSIS INDICATES THE REMNANT 500MB
CLOSED LOW OF TC ISAAC CENTERED IN SOUTHWESTERN OHIO. THE UPPER
OHIO VALLEY IS IN A MOIST LOW-LEVEL ENVIRONMENT, WITH DEW POINTS
IN THE LOW 70S ACROSS MOST OF THE AREA. WITH THE FORCING PROVIDED
FROM ISAAC AND MODERATE INSTABILITY, CONVECTION IS BEGINNING TO
INITIATE ACROSS CENTRAL WV AND SLIDE NORTHEASTWARD TOWARD THE
AREA.
THIS EVENING...THE REMNANT LOW OF ISAAC WILL SLOWLY CROSS OHIO,
WITH A SOUTHERLY FLOW AHEAD OF THIS FEATURE CONTINUING TO ADVECT DEEP
LAYER TROPICAL MOISTURE INTO EASTERN OHIO. THIS WILL ALLOW FOR
ANOTHER DAY OF SHOWERS AND THUNDERSTORMS, WITH PRECIP INCREASING
IN COVERAGE BY LATE AFTERNOON AND MOST LIKELY FOR LOCATIONS SOUTH
AND WEST OF PITTSBURGH. THIS IS SUPPORTED BY THE HRRR, WHICH
INDICATES CONVECTION IN CENTRAL WV STRENGTHENING AND BRINGING
HEAVY RAIN WITH THUNDERSTORMS TO NORTH-CENTRAL WV, EASTERN OHIO,
AND EXTREME SOUTHWEST PA.
RAINFALL, REGARDLESS OF ITS CONVECTIVE/TROPICAL NATURE, WILL BE
QUITE EFFICIENT TODAY, WITH THE RAP INDICATING PRECIPITABLE WATER
INCREASING TO 2 INCHES IN MOST AREAS SOUTH OF THE I-80 AND EVEN TO
2.2 INCHES IN PORTIONS OF EASTERN OHIO. WITH VERY WEAK LOW-LEVEL
WINDS TODAY, SHOWERS AND STORMS WILL BE SLOW MOVING. IN ADDITION,
WITH PREVIOUS RAINFALL SATURATING THE GROUND IN NORTH-CENTRAL WV
AND SOUTH OF I-70 IN EASTERN OHIO, 1-HR FFG IS 1 TO 1.5 INCHES IN
SOME BASINS. WITH THIS IN MIND, FLASH FLOODING IS NOT OUT OF THE
QUESTION AND REMAINS IN THE HWO. GENERALLY ANTICIPATE AROUND A
HALF INCH OF PRECIP TODAY, ALTHOUGH LOCALIZED AREAS COULD SEE TO 2
TO 3 INCHES.
TONIGHT...CONVECTION WILL BE ONGOING EARLY WITH THE MAJORITY OF THE
FORECAST AREA TRANSITIONING TO MORE TROPICAL BY DAWN TUESDAY. THE
CHANCE OF RAIN CANNOT BE RULED OUT OVERNIGHT AS THE REMNANTS OF
ISAAC CONTINUE TO MOVE ACROSS THE AREA. QPF AMOUNTS ARE AROUND A
QUARTER OF AN INCH, ALTHOUGH LOCALIZED HIGHER AMOUNTS WILL BE
POSSIBLE. A WARM AND MUGGY NIGHT CAN BE EXPECTED WITH LOWS A FEW
DEGREES ABOVE MAV/MET GUIDANCE, NEAR 70 ACROSS MOST OF THE AREA.
&&
.SHORT TERM /TUESDAY THROUGH THURSDAY/...
THERE IS REASONABLE ECWMF/GFS/NAM AGREEMENT THAT THE BROAD REMNANT
SURFACE LOW OF ISAAC WILL FINALLY MAKE ITS WAY INTO THE FORECAST
AREA ON TUESDAY. THE LOW IS PROGGED TO BE INTO WESTERN PA BY 00Z
ON WEDNESDAY. SYNOPTIC FORCING AND ABUNDANT TROPICAL MOISTURE WITH
THIS FEATURE WILL ALLOW FOR ANOTHER DAY OF SHOWERS WITH HEAVY
RAIN. THERE IS SOME UNCERTAINTY WITH THUNDERSTORM COVERAGE IN A
TROPICAL AIR MASS, AS CLOUDS WILL BE A LIMITING FACTOR FOR
INSTABILITY. THUS, JUST WENT LIKELY POPS AND CHC THUNDER. QPF IS
ONLY AROUND A HALF OF AN INCH ACROSS THE AREA. HOWEVER, WITH PWAT
VALUES ABOVE 2 INCHES AND WEAK WINDS ALOFT, SLOW- MOVING
THUNDERSTORMS WILL AGAIN ALLOW FOR A LOCALIZED FLASH FLOODING
THREAT WHICH IS MENTIONED IN THE HWO.
ISAAC WILL FINALLY PULL EAST OF THE AREA TUESDAY NIGHT, WITH A DRY
FORECAST ON WEDNESDAY EVERYWHERE EXCEPT THE EASTERN RIDGES. THERE,
MOISTURE MAY LINGER ON THE BACK EDGE OF THIS SYSTEM LONG ENOUGH TO
WARRANT CHC POPS. THE DRY FORECAST CONTINUES UNTIL EARLY LATE
WEDNESDAY NIGHT WHEN A COLD FRONT BEGINS TO APPROACH FROM THE
NORTHWEST. THE FRONT WILL CROSS THE AREA ON THURSDAY, RETURNING
THE CHANCE OF SHOWERS AND THUNDERSTORMS. AT THIS TIME, A SEVERE
THREAT ON THURSDAY APPEARS TO BE LIMITED DUE WITH WEAK SHEAR WITH
THE SYSTEM.
FOR TEMPERATURES, THE LOWEST CONFIDENCE IS ON TUESDAY WITH CLOUD
COVERAGE AND SHOWERS. FORECAST TAKES THE NAM INTO
CONSIDERATION, WITH COOLER TEMPS CLOSER TO THE LOW CENTERED ACROSS
THE SOUTH. TEMP ADVECTION WILL BE LACKING BEHIND ISAAC, WITH HIGH TEMPS
CONTINUING TO BE AROUND 5 DEGREES ABOVE NORMAL ON WEDNESDAY AND
THURSDAY (AHEAD OF THE FRONT). WITH TDS REMAINING IN THE MID TO
UPPER 60S THROUGH THE MID-WEEK, TEMPS EACH NIGHT WILL BE AROUND 10
DEGREES ABOVE NORMAL FOR LOWS.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
HIGH PRESSURE THURSDAY NIGHT IN THE WAKE OF A COLD FRONT IS
FORECAST TO BRING DRY WEATHER INTO FRIDAY. A COLD FRONT PUSHING INTO
THE OHIO VALLEY SATURDAY WILL BRING AN INCREASING RISK OF SHOWERS
FOR SATURDAY INTO SUNDAY. THE FRONT WILL MOVE EAST OF THE DISTRICT
MONDAY BRINGING AN END TO THE SHOWERS.
&&
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
RECENT RADAR DATA SHOWS BAND OF MVFR SHOWERS WILL MOVE SLOWLY
NORTHWARD ACROSS THE UPPER OHIO VALLEY THROUGH THIS EVENING.
SOME ISOLATED THUNDERSTORMS ARE POSSIBLE...ESPECIALLY IN THE
SOUTH BUT THE RISK OF SHOWERS IS TOO SLIGHT TO INCLUDE AS TEMPOS
IN THE TAFS. SURFACE WINDS WILL BE MAINLY SOUTHEAST AT 5 TO 10 KNOTS.
EXPECT MVFR RESTRICTIONS AFTER 08Z DUE TO FOG DEVELOPMENT. FOG COULD
DEVELOP EARLIER IF RAINFALL COVERAGE IS GREATER THAN CURRENTLY
PROJECTED.
.OUTLOOK /TUESDAY THROUGH FRIDAY/...
RESTRICTIONS ARE LIKELY TUESDAY DUE TO MORE NUMEROUS SHOWERS
ASSOCIATED WITH A COLD FRONTAL PASSAGE. RESTRICTIONS WILL STILL
BE POSSIBLE TUESDAY NIGHT INTO THURSDAY DUE TO SCATTERED SHOWERS AND
LATE NIGHT FOG UNTIL A SECOND COLD FRONTAL PASSAGE THURSDAY.
ENSUING DRY CONDITIONS WILL PROMOTE PREVALENT VFR FRIDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
210 PM EDT MON SEP 3 2012
.SYNOPSIS...
THE REMNANT LOW OF ISAAC WILL SLOWLY MOVE ACROSS THE UPPER OHIO
VALLEY THROUGH TUESDAY NIGHT, BRINGING THUNDERSTORMS AND HEAVY RAIN
TO THE AREA. THE SYSTEM WILL MOVE EAST OF THE AREA TUESDAY NIGHT
INTO EARLY WEDNESDAY, WITH A BREAK FROM SHOWERS AS HIGH PRESSURE
BUILDS IN FOR WEDNESDAY. A COLD FRONT WILL CROSS THE AREA ON
THURSDAY, RETURNING THE CHANCE FOR SHOWERS AND THUNDERSTORMS.
&&
.NEAR TERM /THROUGH TONIGHT/...
18Z ENHANCED SHORT TERM FORECAST UPDATE HAS BEEN ISSUED TO REDUCE
POPS EARLY THIS AFTERNOON. TEMPS HAVE ALSO BEEN INCREASED IN
LOCATIONS WHERE THERE HAVE BEEN BREAKS IN THE CLOUDS.
THE LATEST RAP MID-LEVEL ANALYSIS INDICATES THE REMNANT 500MB CLOSED
LOW OF TC ISAAC CENTERED IN SOUTHWESTERN OHIO. THE UPPER OHIO
VALLEY IS IN A MOIST LOW-LEVEL ENVIRONMENT, WITH DEW POINTS IN THE
LOW 70S ACROSS MOST OF THE AREA. WITH THE FORCING PROVIDED FROM
ISAAC AND MODERATE INSTABILITY, CONVECTION IS BEGINNING TO
INITIATE ACROSS CENTRAL WV AND SLIDE NORTHEASTWARD TOWARD THE
AREA.
THIS AFTERNOON...THE REMNANT LOW OF ISAAC WILL SLOWLY CROSS OHIO,
WITH A SOUTHERLY FLOW AHEAD OF THIS FEATURE CONTINUING TO ADVECT DEEP
LAYER TROPICAL MOISTURE INTO EASTERN OHIO. THIS WILL ALLOW FOR
ANOTHER DAY OF SHOWERS AND THUNDERSTORMS, WITH PRECIP INCREASING
IN COVERAGE BY LATE AFTERNOON AND MOST LIKELY FOR LOCATIONS SOUTH
AND WEST OF PITTSBURGH. THIS IS SUPPORTED BY THE HRRR, WHICH
INDICATES CONVECTION IN CENTRAL WV STRENGTHENING AND BRINGING
HEAVY RAIN WITH THUNDERSTORMS TO NORTH-CENTRAL WV, EASTERN OHIO,
AND EXTREME SOUTHWEST PA. FOR TEMPS, DESPITE 850MB TEMPS WARMING
TO THE 17-18C RANGE WITH WARM AND MOIST AIR MASS, CLOUD COVERAGE
WILL BE A LIMITING FACTOR WITH HIGHS TODAY. TEMPS ARE CLOSE TO THE
GFS LAMP, WITH HIGHS RANGING IN THE LOW TO MID 80S ACROSS MUCH OF
THE AREA.
RAINFALL, REGARDLESS OF ITS CONVECTIVE/TROPICAL NATURE, WILL BE
QUITE EFFICIENT TODAY, WITH THE RAP INDICATING PRECIPITABLE WATER
INCREASING TO 2 INCHES IN MOST AREAS SOUTH OF THE I-80 AND EVEN TO
2.2 INCHES IN PORTIONS OF EASTERN OHIO. WITH VERY WEAK LOW-LEVEL
WINDS TODAY, SHOWERS AND STORMS WILL BE SLOW MOVING. IN ADDITION,
WITH PREVIOUS RAINFALL SATURATING THE GROUND IN NORTH-CENTRAL WV
AND SOUTH OF I-70 IN EASTERN OHIO, 1-HR FFG IS 1 TO 1.5 INCHES IN
SOME BASINS. WITH THIS IN MIND, FLASH FLOODING IS NOT OUT OF THE
QUESTION AND REMAINS IN THE HWO. WILL HAVE TO CONTINUE TO WATCH
RADAR AND MESOSCALE MODEL TRENDS, AS A FLASH FLOOD WATCH MAY BE
NEEDED. GENERALLY ANTICIPATE AROUND A HALF INCH OF PRECIP TODAY,
ALTHOUGH LOCALIZED AREAS COULD SEE TO 2 TO 3 INCHES.
TONIGHT...CONVECTION WILL BE ONGOING EARLY WITH THE MAJORITY OF THE
FORECAST AREA TRANSITIONING TO MORE TROPICAL BY DAWN TUESDAY. THE
CHANCE OF RAIN CANNOT BE RULED OUT OVERNIGHT AS THE REMNANTS OF
ISAAC CONTINUE TO MOVE ACROSS THE AREA. QPF AMOUNTS ARE AROUND A
QUARTER OF AN INCH, ALTHOUGH LOCALIZED HIGHER AMOUNTS WILL BE
POSSIBLE. A WARM AND MUGGY NIGHT CAN BE EXPECTED WITH LOWS A FEW
DEGREES ABOVE MAV/MET GUIDANCE, NEAR 70 ACROSS MOST OF THE AREA.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
SHOWER/STORM CHANCES WILL QUICKLY INCREASE TUESDAY MORNING, AS
THE ENTIRE SYSTEM BEGINS TO PICK UP SPEED AND MOVE TO THE EAST.
THE PUSH WILL COME FROM A SHORTWAVE TROUGH, WHICH WILL CROSS THE
GREAT LAKES TUESDAY MORNING AND MOVE INTO W PA DURING THE
AFTERNOON. THE ENERGY FROM THE NORTHERN TROUGH WILL WORK IN
CONJUNCTION WITH THE ENERGY AND MOISTURE FROM ISAAC`S REMNANTS TO
PROVIDE A WET TUESDAY FOR MUCH OF THE AREA. THE ATMOSPHERE WILL
REMAIN JUICY, SO HEAVY DOWNPOURS ARE A THREAT ON TUESDAY,
ESPECIALLY WITH STORMS THAT MAY DEVELOP.
THE SFC WAVE WILL MOVE THROUGH TUESDAY NIGHT DRAGGING BEHIND THE
SFC COLD FRONT. FRONT WILL STALL ACROSS THE SOUTH AND EAST LATE
TUESDAY NIGHT, WAITING FOR A PUSH FROM THE NEXT UL WAVE. WILL SHOW
A DECREASE IN POPS TUESDAY NIGHT, WHILE LEAVING RAIN CHANCES INTO
WED MORNING ACROSS THE SOUTH AND RIDGES.
WEDNESDAY`S SW TROUGH WILL FINALLY KICK THE ENTIRE SYSTEM OUT OF
THE UPPER OHIO VALLEY, WHICH WILL END THE RISK FOR PRECIPITATION AND
ALSO BRING A SLOW DECREASE IN CLOUD COVER.
SUNSHINE SHOULD MAKE A RETURN BE WED AFTERNOON.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
A SECONDARY...AND DECISIVE COLD FRONT IS PROJECTED ACROSS THE AREA BY
THURSDAY. BUILDING HIGH PRESSURE IN THE WAKE OF THE FRONT IS FORECAST
TO BRING DRY WEATHER TO CLOSE THE WEEK. ANOTHER FRONT...CURRENTLY
TIMED FOR AN EARLY SUNDAY APPROACH MAY BRING THE NEXT CHANCE FOR
SHOWERS.
&&
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
RECENT RADAR DATA SHOWS BAND OF MVFR SHOWERS WILL MOVE SLOWLY
NORTHWARD ACROSS THE UPPER OHIO VALLEY THROUGH THIS EVENING.
SOME ISOLATED THUNDERSTORMS ARE POSSIBLE...ESPECIALLY IN THE
SOUTH BUT THE RISK OF SHOWERS IS TOO SLIGHT TO INCLUDE AS TEMPOS
IN THE TAFS. SURFACE WINDS WILL BE MAINLY SOUTHEAST AT 5 TO 10 KNOTS.
EXPECT MVFR RESTRICTIONS AFTER 08Z DUE TO FOG DEVELOPMENT. FOG COULD
DEVELOP EARLIER IF RAINFALL COVERAGE IS GREATER THAN CURRENTLY
PROJECTED.
.OUTLOOK /TUESDAY THROUGH FRIDAY/...
RESTRICTIONS ARE LIKELY TUESDAY DUE TO MORE NUMEROUS SHOWERS
ASSOCIATED WITH A COLD FRONTAL PASSAGE. RESTRICTIONS WILL STILL
BE POSSIBLE TUESDAY NIGHT INTO THURSDAY DUE TO SCATTERED SHOWERS AND
LATE NIGHT FOG UNTIL A SECOND COLD FRONTAL PASSAGE THURSDAY.
ENSUING DRY CONDITIONS WILL PROMOTE PREVALENT VFR FRIDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
1030 AM EDT MON SEP 3 2012
.SYNOPSIS...
THE REMNANT LOW OF ISAAC WILL SLOWLY MOVE ACROSS THE UPPER OHIO
VALLEY THROUGH TUESDAY NIGHT, BRINGING THUNDERSTORMS AND HEAVY RAIN
TO THE AREA. A FRONT WILL MOVE THROUGH TUESDAY NIGHT INTO EARLY
WEDNESDAY, BRINGING DRIER WEATHER AS HIGH PRESSURE BUILDS IN FOR
WEDNESDAY. A COLD FRONT WILL CROSS THE AREA ON THURSDAY, RETURNING
THE CHANCE FOR SHOWERS AND THUNDERSTORMS.
&&
.NEAR TERM /THROUGH TONIGHT/...
15Z ENHANCED SHORT TERM FORECAST UPDATE HAS BEEN ISSUED IN ORDER TO
ACCOUNT FOR RECENT RADAR TRENDS WITH MORE PERSISTENT RAIN WEST OF
I-77 IN OHIO AND CONVECTION DEVELOPING AND MOVING NORTH OF THE
MASON-DIXON LINE.
THE LATEST RAP MID-LEVEL ANALYSIS INDICATES THE REMNANT 500MB CLOSED
LOW OF TC ISAAC CENTERED IN SOUTHWESTERN OHIO. ABUNDANT MOISTURE IS
PRESENT IN THE 800-300MB LAYER FOR AREAS WEST OF THE I-77 CORRIDOR
IN EASTERN OHIO. THE 12Z KILN SOUNDING AND STRATIFORM PRECIP
INDICATED BY RADAR RETURNS ARE MORE REPRESENTATIVE OF THE TROPICAL
ENVIRONMENT THERE. MEANWHILE, EASTWARD, THE 12Z KPIT SOUNDING IS
REPRESENTATIVE OF A CONVECTIVE ENVIRONMENT WITH 2000 J/KG SBCAPE AND
DRIER MID-LEVELS. IN THIS AIR MASS, ISOLATED SHOWERS AND
THUNDERSTORMS HAVE BEGUN DEVELOP AND MOVE NORTH OF THE MASON-
DIXON LINE.
THIS AFTERNOON...THE REMNANT LOW OF ISAAC WILL SLOWLY CROSS OHIO,
WITH A SOUTHERLY FLOW AHEAD OF THIS FEATURE ADVECTING DEEP LAYER
TROPICAL MOISTURE INTO EASTERN OHIO. THIS WILL ALLOW FOR ANOTHER DAY
OF SHOWERS AND THUNDERSTORMS, WITH PRECIP INCREASING IN COVERAGE
THIS AFTERNOON AND MOSTLY LIKELY FOR LOCATIONS SOUTH AND WEST OF
PITTSBURGH. DESPITE 850MB TEMPS WARMING TO THE 17-18C RANGE WITH
WARM AND MOIST AIR MASS, CLOUD COVERAGE WILL BE A LIMITING FACTOR
WITH HIGHS TODAY. TEMPS ARE CLOSE TO THE GFS LAMP, WITH HIGHS
RANGING IN THE LOW TO MID 80S ACROSS MUCH OF THE AREA.
THE RAP INDICATES SBCAPE INCREASING TO AROUND 2500 IN CONVECTIVE
ENVIRONMENT IN NORTHERN WV AND WESTERN PA. MEANWHILE, EASTERN OHIO
WILL REMAIN INSTABILITY STARVED WITH ONGOING PRECIP. RAINFALL,
REGARDLESS OF ITS CONVECTIVE/TROPICAL NATURE, WILL BE QUITE
EFFICIENT TODAY, WITH THE RAP INDICATING PRECIPITABLE WATER
INCREASING TO 2 INCHES IN MOST AREAS SOUTH OF THE I-80 AND EVEN TO
2.2 INCHES IN PORTIONS OF EASTERN OHIO. WITH VERY WEAK LOW-LEVEL
WINDS TODAY, SHOWERS AND STORMS WILL BE SLOW MOVING. IN ADDITION,
WITH PREVIOUS RAINFALL SATURATING THE GROUND IN NORTH-CENTRAL WV
AND SOUTH OF I-70 IN EASTERN OHIO, 1-HR FFG IS 1 TO 1.5 INCHES.
WITH THIS IN MIND, FLASH FLOODING IS NOT OUT OF THE QUESTION AND
REMAINS IN THE HWO. WILL HAVE TO CONTINUE TO WATCH RADAR AND
MESOSCALE MODEL TRENDS, AS A FLASH FLOOD WATCH MAY BE NEEDED.
GENERALLY ANTICIPATE AROUND A HALF INCH OF PRECIP TODAY, ALTHOUGH
LOCALIZED AREAS COULD SEE TO 2 TO 3 INCHES.
TONIGHT...CONVECTION WILL BE ONGOING EARLY WITH THE MAJORITY OF THE
FORECAST AREA TRANSITIONING TO MORE TROPICAL BY DAWN TUESDAY. THE
CHANCE OF RAIN CANNOT BE RULED OUT OVERNIGHT AS THE REMNANTS OF
ISAAC CONTINUE TO MOVE ACROSS THE AREA. QPF AMOUNTS ARE AROUND A
QUARTER OF AN INCH, ALTHOUGH LOCALIZED HIGHER AMOUNTS WILL BE
POSSIBLE. A WARM AND MUGGY NIGHT CAN BE EXPECTED WITH LOWS A FEW
DEGREES ABOVE MAV/MET GUIDANCE, NEAR 70 ACROSS MOST OF THE AREA.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
SHOWER/STORM CHANCES WILL QUICKLY INCREASE TUESDAY MORNING, AS
THE ENTIRE SYSTEM BEGINS TO PICK UP SPEED AND MOVE TO THE EAST.
THE PUSH WILL COME FROM A SHORTWAVE TROUGH, WHICH WILL CROSS THE
GREAT LAKES TUESDAY MORNING AND MOVE INTO W PA DURING THE
AFTERNOON. THE ENERGY FROM THE NORTHERN TROUGH WILL WORK IN
CONJUNCTION WITH THE ENERGY AND MOISTURE FROM ISAAC`S REMNANTS TO
PROVIDE A WET TUESDAY FOR MUCH OF THE AREA. THE ATMOSPHERE WILL
REMAIN JUICY, SO HEAVY DOWNPOURS ARE A THREAT ON TUESDAY,
ESPECIALLY WITH STORMS THAT MAY DEVELOP.
THE SFC WAVE WILL MOVE THROUGH TUESDAY NIGHT DRAGGING BEHIND THE
SFC COLD FRONT. FRONT WILL STALL ACROSS THE SOUTH AND EAST LATE
TUESDAY NIGHT, WAITING FOR A PUSH FROM THE NEXT UL WAVE. WILL SHOW
A DECREASE IN POPS TUESDAY NIGHT, WHILE LEAVING RAIN CHANCES INTO
WED MORNING ACROSS THE SOUTH AND RIDGES.
WEDNESDAY`S SW TROUGH WILL FINALLY KICK THE ENTIRE SYSTEM OUT OF
THE UPPER OHIO VALLEY, WHICH WILL END THE RISK FOR PRECIPITATION AND
ALSO BRING A SLOW DECREASE IN CLOUD COVER.
SUNSHINE SHOULD MAKE A RETURN BE WED AFTERNOON.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
A SECONDARY...AND DECISIVE COLD FRONT IS PROJECTED ACROSS THE AREA BY
THURSDAY. BUILDING HIGH PRESSURE IN THE WAKE OF THE FRONT IS FORECAST
TO BRING DRY WEATHER TO CLOSE THE WEEK. ANOTHER FRONT...CURRENTLY
TIMED FOR AN EARLY SUNDAY APPROACH MAY BRING THE NEXT CHANCE FOR
SHOWERS.
&&
.AVIATION /14Z MONDAY THROUGH FRIDAY/...
MVFR STRATUS CAN LINGER NEAR THE MOUNTAINS UNTIL MIDDAY AND AFFECT
KDUJ OR KFKL.
RECENT RADAR DATA SHOWS BAND OF MVFR SHOWERS WILL MOVE SLOWLY
NORTHWARD ACROSS THE UPPER OHIO VALLEY THROUGH AFTERNOON, BUT MAY
NOT REACH KFKL AND KDUJ. AS SURFACE TEMPERATURES HEAT PAST 77,
ISOLATED THUNDERSTORMS WITH HEAVY RAIN CAN DEVELOP.
SURFACE WINDS WILL BECOME MAINLY SOUTHEAST NEAR 10 KTS AFTER 14Z,
THEN DECREASE TO 5 KTS THIS EVENING.
EXPECT MVFR RESTRICTIONS AFTER 08Z DUE TO FOG DEVELOPMENT. FOG COULD
DEVELOP EARLIER IF RAINFALL COVERAGE IS GREATER THAN CURRENTLY
PROJECTED.
.OUTLOOK /TUESDAY THROUGH FRIDAY/...
RESTRICTIONS ARE LIKELY TUESDAY DUE TO MORE NUMEROUS SHOWERS
ASSOCIATED WITH A COLD FRONTAL PASSAGE. RESTRICTIONS WILL STILL
BE POSSIBLE TUESDAY NIGHT INTO THURSDAY DUE TO SCATTERED SHOWERS AND
LATE NIGHT FOG UNTIL A SECOND COLD FRONTAL PASSAGE THURSDAY.
ENSUING DRY CONDITIONS WILL PROMOTE PREVALENT VFR FRIDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
700 AM EDT MON SEP 3 2012
.SYNOPSIS...
THE SYSTEM THAT WAS ONCE TROPICAL CYCLONE ISAAC, WILL TAKE UNTIL
MIDWEEK TO FINALLY CLEAR THE AREA. A COLD FRONT WILL PICK UP THE
REMNANTS AS THE FRONT MOVES THROUGH LATE TUESDAY. THE RISK FOR
SHOWERS OR STORMS WILL CONTINUE INTO EARLY WEDNESDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
BLEND OF RECENT RADAR DATA AND HRRR MODEL OUTPUT SHOW BANDS OF
SCATTERED SHOWERS WILL BEGIN TO MOVE NORTHWARD THROUGH THE UPPER
OHIO VALLEY TODAY. THESE SHOWER BANDS ARE PART OF THE OUTER
FRINGE OF THE POST-TROPICAL SYSTEM THAT WAS ONCE NAMED ISAAC.
AS DAYTIME HEATING RAISES SURFACE TEMPERATURES INTO THE UPPER 70S,
SCATTERED THUNDERSTORMS WILL DEVELOP, SOME OF WHICH CAN PRODUCE
HEAVY RAINS.
THE I-80 CORRIDOR HAS THE LEAST POTENTIAL OF GETTING ANY BOUTS OF
HEAVY RAIN.
FORECASTED TEMPERATURES TO BE NEAR NORMAL BASED ON RECENT GFS AND
NAM MOS. CONDITIONS WILL REMAIN HUMID WITH SURFACE DEW POINTS 65
TO 70.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
EXPECT A BREAK IN WIDESPREAD ACTIVITY TONIGHT WITH THE LOSS OF
SUNSHINE AND A WEAKENING OF THE UL WAVE. AS RAIN EVAPORATES INTO
THE HUMID NOCTURNALLY-COOLING SURFACE LAYER, AREAS OF FOG CAN
DEVELOP LATE TONIGHT, PARTICULARLY IN THE RIVER VALLEYS.
SHOWER/STORM CHANCES WILL QUICKLY INCREASE TUESDAY MORNING, AS
THE ENTIRE SYSTEM BEGINS TO PICK UP SPEED AND MOVE TO THE EAST.
THE PUSH WILL COME FROM A SHORTWAVE TROUGH, WHICH WILL CROSS THE
GREAT LAKES TUESDAY MORNING AND MOVE INTO W PA DURING THE
AFTERNOON. THE ENERGY FROM THE NORTHERN TROUGH WILL WORK IN
CONJUNCTION WITH THE ENERGY AND MOISTURE FROM ISAAC`S REMNANTS TO
PROVIDE A WET TUESDAY FOR MUCH OF THE AREA. THE ATMOSPHERE WILL
REMAIN JUICY, SO HEAVY DOWNPOURS ARE A THREAT ON TUESDAY,
ESPECIALLY WITH STORMS THAT MAY DEVELOP.
THE SFC WAVE WILL MOVE THROUGH TUESDAY NIGHT DRAGGING BEHIND THE
SFC COLD FRONT. FRONT WILL STALL ACROSS THE SOUTH AND EAST LATE
TUESDAY NIGHT, WAITING FOR A PUSH FROM THE NEXT UL WAVE. WILL SHOW
A DECREASE IN POPS TUESDAY NIGHT, WHILE LEAVING RAIN CHANCES INTO
WED MORNING ACROSS THE SOUTH AND RIDGES.
WEDNESDAY`S SW TROUGH WILL FINALLY KICK THE ENTIRE SYSTEM OUT OF
THE UPPER OHIO VALLEY, WHICH WILL END THE RISK FOR PRECIPITATION AND
ALSO BRING A SLOW DECREASE IN CLOUD COVER.
SUNSHINE SHOULD MAKE A RETURN BE WED AFTERNOON.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
A SECONDARY...AND DECISIVE COLD FRONT IS PROJECTED ACROSS THE AREA BY
THURSDAY. BUILDING HIGH PRESSURE IN THE WAKE OF THE FRONT IS FORECAST
TO BRING DRY WEATHER TO CLOSE THE WEEK. ANOTHER FRONT...CURRENTLY
TIMED FOR AN EARLY SUNDAY APPROACH MAY BRING THE NEXT CHANCE FOR
SHOWERS.
&&
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
EXPECT ANY REMAINING MVFR CONDITIONS FROM FOG TO END BY 14Z. MVFR
STRATUS CAN LINGER NEAR THE MOUNTAINS UNTIL MIDDAY AND AFFECT
KDUJ, KLBE, AND KMGW.
RECENT RADAR DATA SHOWS BAND OF MVFR SHOWERS WILL MOVE SLOWLY
NORTHWARD ACROSS THE UPPER OHIO VALLEY THROUGH AFTERNOON, BUT MAY
NOT REACH KFKL AND KDUJ. AS SURFACE TEMPERATURES HEAT PAST 77,
ISOLATED THUNDERSTORMS WITH HEAVY RAIN CAN DEVELOP.
SURFACE WINDS WILL BECOME MAINLY SOUTHEAST NEAR 10 KTS AFTER 14Z,
THEN DECREASE TO 5 KTS THIS EVENING.
EXPECT MVFR RESTRICTIONS AFTER 08Z DUE TO FOG DEVELOPMENT. FOG COULD
DEVELOP EARLIER IF RAINFALL COVERAGE IS GREATER THAN CURRENTLY
PROJECTED.
.OUTLOOK /TUESDAY THROUGH FRIDAY/...
RESTRICTIONS ARE LIKELY TUESDAY DUE TO MORE NUMEROUS SHOWERS
ASSOCIATED WITH A COLD FRONTAL PASSAGE. RESTRICTIONS WILL STILL
BE POSSIBLE TUESDAY NIGHT INTO THURSDAY DUE TO SCATTERED SHOWERS AND
LATE NIGHT FOG UNTIL A SECOND COLD FRONTAL PASSAGE THURSDAY.
ENSUING DRY CONDITIONS WILL PROMOTE PREVALENT VFR FRIDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
530 PM EDT MON SEP 3 2012
.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 517 PM EDT MON SEP 3 2012
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW WSW FLOW OVER THE UPPER
GREAT LAKES BTWN UPPER RIDGE EXTENDING FROM THE PLAINS TO THE LWR
LAKES AND A DEEP...OCCLUDED LOW OVER NRN MANITOBA. NARROW MOISTURE
RIBBON HAS SHIFTED INTO THE UPPER LAKES IN ASSOCIATION WITH
DISSIPATING SFC TROF ORIGINALLY ASSOCIATED WITH DEEP SYSTEM IN NRN
MANITOBA. LEFT EXIT OF UPPER JET STREAK AIDED EARLY MORNING
CONVECTION OVER NW UPPER MI/LAKE SUPERIOR. BASED ON LATEST RUC
ANALYSIS...IT APPEARS CONVECTION THAT HAS BEEN DEVELOPING MAY BE
GETTING SOME SUPPORT FROM THE RIGHT ENTRANCE OF JET STREAK NOW.
ONGOING CONVECTION OVER ROUGHLY THE SE HALF OF THE FCST AREA WILL
CONTINUE SETTLE SE INTO THE EVENING HRS. WITH MUCAPE ON THE ORDER
OF 1000-2000J/KG AND DEEP LAYER SHEAR AROUND 40KT...ORGANIZED STORMS
WILL CONTINUE ALONG WITH THE POTENTIAL OF SVR FOR THE NEXT SEVERAL
HRS. SHRA/TSRA SHOULD BE OUT OF THE SE/SCNTRL FCST AREA MID TO LATE
EVENING. HEALTHY DRYING ALOFT (NOTE UPSTREAM 12Z KINL SOUNDING) WILL
THEN OCCUR THRU THE NIGHT...ENDING ANY THREAT OF ADDITIONAL PCPN.
CONSIDERING DRYNESS OF INCOMING AIR MASS AND LIGHT/CALM WIND
UNDER BUBBLE SFC HI PRES BUILDING INTO THE AREA...FAVORED
THE LOWER SIDE OF AVBL GUIDANCE FOR MIN TEMPS. VIGOROUS DRYING
ALOFT/LIGHT WINDS FAVOR FOG DEVELOPMENT...ESPECIALLY SINCE THERE HAS
BEEN RAINFALL TODAY. THUS...MAINTAINED MENTION OF AREAS OF FOG OVER
MUCH OF THE INTERIOR.
ON TUE...ATTENTION TURNS TO A COUPLE OF SHORTWAVES EXTENDING FROM
ND INTO MT. ONE OR BOTH OF THESE WAVES WILL REACH THE UPPER LAKES
TUE AND WILL LIKELY PROVIDE SUFFICIENT FORCING FOR ISOLD/SCT
CONVECTION. GIVEN THAT CONVECTION IS CURRENTLY BEING OBSERVED OVER
THE ERN DAKOTAS AHEAD OF THE FIRST WAVE...BUMPED POPS UP INTO THE
CHC CATEGORY OVER ROUGHLY THE W HALF OF THE FCST AREA TUE. ALTHOUGH
NAM/GFS MLCAPES ARE IN THE 1500-2500J/KG RANGE...DEEP LAYER SHEAR IS
UNDER 30KT WHICH WILL WORK TO LIMIT MORE WIDESPREAD SVR POTENTIAL.
NONETHELESS...IF STORMS DO DEVELOP...MAY SEE SOME ISOLD/PULSE TYPE
SVR STORMS TUE AFTN.
.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 517 PM EDT MON SEP 3 2012
BASIC OUTLOOK OF THE LONG TERM NOT TOO DIFFERENT FROM YESTERDAY. WV
LOOP AND 12Z RAOBS INDICATE PAIR OF UPPER LOWS IN CANADA FROM
NORTHERN MANITOBA INTO NORTHERN BRITISH COLUMBIA. MANITOBA LOW STAYS
FAIRLY STATIONARY THROUGH WEDNESDAY WHILE THE BRITISH COLUMBIA LOW
DIGS TO ITS SOUTH AND EVENTUALLY SOUTHEAST INTO NORTHERN ONTARIO. AS
THIS OCCURS...STRONG SFC-H85 COLD FRONT MARCHES ACROSS UPPER GREAT
LAKES WEDNESDAY AFTERNOON AND EVENING. DYNAMICS PROVIDED BY 12-HR
H5 HEIGHT FALLS TO 60M AND A COUPLED JET STRUCTURE COMBINE WITH
SFC-H85 FRONT AND SURGE OF H85 MOISTURE TRANSPORT TO GENERATE SHRA
ALONG AND AHEAD OF THE FRONT. DEPENDING ON TIMING OF FRONT AND
HEATING AHEAD OF FRONT...TSRA COULD BE STRONG GIVEN 0-6KM CAPES UP
TO 1500 J/KG AND AS H85 JET INCREASES OVER CWA AND BECOMES PARALLEL
TO THE H5 FLOW. SETUP IS FAVORABLE FOR DYNAMICALLY DRIVEN BOW-ECHO
SOMEWHERE OVER THE AREA AS THERE IS A DRY H7-H5 LAYER PUNCHING INTO
THE AREA FROM THE WEST WITH DWPNT DEPRESSIONS OVR 20C BY LATER AFTN.
BEST CHANCE FOR SEVERE PROBABLY ENDS UP SOUTH AND EAST OF CWA WHERE
GREATEST MLCAPES ARE FORECAST IN THE AFTN. AT THE LEAST...LIKELY
POPS ARE CERTAINLY WARRANTED AS THE SFC-H85 FRONT WORKS ACROSS THE
CWA.
ONCE FRONT PLOWS THROUGH MAY SEE HIGHER WIND GUSTS WEDNESDAY NIGHT
INTO THURSDAY AS SFC LOW WRAPS UP BTWN LAKE SUPERIOR AND HUDSON BAY.
GFS/ECMWF H85 WINDS NOT THAT STRONG...MAYBE UP TO 30 KTS...SO DOES
NOT APPEAR THAT WINDS WILL BECOME TOO STRONG. IF THE SFC LOW ENDS UP
DEEPENING CLOSER TO LK SUPERIOR...COULD SEE NORTHWESTERLY WIND GUSTS
ALONG LK SUPERIOR 40-45 MPH. AT THIS POINT...WX ON THURSDAY SHOULD
END UP QUIET AS UPR MICHIGAN IS BTWN THE STRONG SHORTWAVE TROUGH
THAT MOVES THROUGH MID WEEK AND RE-INFORCING TROUGH THAT IS FORECAST
TO ROTATE THROUGH ON FRIDAY. FORECAST SOUNDINGS FROM GFS AND OUTPUT
FROM GEM-NHEM INDICATE SOME POTENTIAL FOR LIGHT SHRA OVER THE
EASTERN CWA IN WEAK AREA OF LOW-LEVEL CONVERGENCE. SEEMS GREATER
CHANCE OF SHRA ARRIVES ON FRIDAY WITH THE INCOMING TROUGH AND
INDICATION OF SHORTWAVE RIDING THROUGH IN WEST/NORTHWEST FLOW
ALOFT. THIS FORCING ALONG WITH INCREASING OVER-WATER INSTABILITY
WITH LAKE EFFECT CAPES PUSHING AOA 500J/KG SUGGESTS HYBRID LATE
SUMMER AND EARLY FALL TYPE SHRA AND MAYBE EVEN MENTION OF TSRA
GIVEN LAKE INDUCED EQL OVER 20KFT WHICH PUSHES CONVECTIVE DEPTH
BLO 0C.
GIVEN LAKE-H85 DELTA T AOA 15C...DEEP LAKE INDUCED CLOUD DEPTH...AND
WINDS WITHIN THE MIXED LAYER STAYING BLO 25 KTS...PARAMETERS STILL
LINE UP FOR WATERSPOUT POTENTIAL ON FRIDAY...ESPECIALLY IF SUBTLE
LOW-LEVEL TROUGH THAT IS SHOWING UP IN MODELS OVER EASTERN LK
SUPERIOR/EASTERN CWA DOES INDEED VERIFY. TOUGH TO INCLUDE MENTION OF
WATERSPOUTS THIS FAR OUT IN THE FORECAST BUT WILL BE INTERESTING TO
SEE OUTPUT IN THE NEXT COUPLE DAYS FROM THE NEW EXPERIMENTAL GREAT
LAKES WATERSPOUT FORECAST BASED ON THE SZILAGYI WATERSPOUT INDEX
/SWI/ THAT COMES OUT OF THE INTERNATIONAL CENTRE FOR WATERSPOUT
RESEARCH /ICWR/. IN ADDITION TO WATERSPOUTS...WILL ALSO LIKELY HAVE
INCREASED RISK OF RIP CURRENTS ALONG LK SUPERIOR BEACHES...MAINLY IN
ALGER COUNTY WITH THE EXPECTED NORTHWEST WINDS.
UPPER TROUGH SLOWLY MOVES EAST THROUGH NEXT WEEKEND. THIS PLACES
UPPER LAKES WITHIN ZONE OF SHARP CONFLUENCE AND ASSOCIATED SFC
RIDGING. ECMWF HAS DEFINITELY TRENDED FARTHER EAST WITH TROUGH AND
KEEPS QPF OUT OF UPR MICHIGAN FOR THE WEEKEND. GFS IS SLIGHTLY
FARTHER WEST WITH THE TROUGH AND WOULD KEEP THREAT OF SHRA OVER
EASTERN CWA ON SATURDAY. BASED ON AMPLIFIED PATTERN CANNOT RULE THIS
IDEA OUT AND WILL AT THE LEAST KEEP CONSENSUS SLIGHT CHANCE POPS AND
BUMP UP SKY COVER. SUNDAY INTO MONDAY IS TOUGH TO FIGURE OUT AS
ECMWF CONTINUES TO INDICATE STRONGER SHORTWAVE WITHIN BASE OF TROUGH
LIFTING NORTH AND AFFECTING THE EASTERN PORTIONS OF CWA WITH SOME
SHRA WHILE THE GFS KEEPS ALL THIS TOO FAR TO THE EAST TO AFFECT THE
AREA. NO REAL CONSISTENT SIGNAL FOR EITHER SOLUTION SO HAVE TO KEEP
CONSENSUS POPS AT THIS TIME.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 139 PM EDT MON SEP 3 2012
WITH WEAK SFC TROF MOVING ACROSS UPPER MI...KSAW MAY BE IMPACTED BY
BRIEF SHRA/TSRA AND MVFR CONDITIONS OVER THE NEXT COUPLE OF HRS.
TROF IS ALREADY PAST KIWD/KCMX...SO THE AFTN WILL HAVE VFR CONDITIONS
AND NO PCPN AT THOSE 2 SITES. WITH SFC WINDS DIMINISHING TO
LIGHT/CALM UNDER UPPER LEVEL DRYING...FOG IS LIKELY TO FORM TONIGHT
WITH IFR...POSSIBLE LIFR...CONDITIONS. FOG WILL DISSIPATE WITHIN A
COUPLE OF HRS AFTER SUNRISE TUE. NEXT DISTURBANCE APPROACHING THE AREA
MAY TRIGGER ISOLD/SCT CONVECTION TUE...BUT MOST LIKELY NOT UNTIL BEYOND
THIS FCST PERIOD.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 429 AM EDT MON SEP 3 2012
EXPECT S WINDS UP TO 20 KTS IN ADVANCE OF AN APPROACHING COLD FRONT
TO DIMINISH THIS EVENING AS THE FRONT TENDS TO WEAKEN. LIGHT WINDS WILL
THEN PREVAIL THRU TONIGHT AS A WEAK HI PRES SYSTEM MOVES INTO THE
UPPER GREAT LAKES. A SERIES OF LOW PRESSURE SYSTEMS AND COLD FRONTS
WILL MOVE NEAR LAKE SUPERIOR TUESDAY THROUGH SUNDAY...LEADING TO
PERIODS OF INCREASED WINDS. HOWEVER...AT THIS TIME WINDS ARE EXPECTED
TO REMAIN BELOW 25KTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...ROLFSON
LONG TERM...JLA
AVIATION...ROLFSON
MARINE...KC/TITUS
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
140 PM EDT MON SEP 3 2012
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 429 AM EDT MON SEP 3 2012
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW WSW FLOW ALF OVER
THE UPR GRT LKS BTWN UPR RDG EXTENDING FM THE PLAINS INTO LWR MI AND
DEEP...OCCLUDED LO OVER NRN SASKATCHEWAN THAT IS DRIFTING ONLY
SLOWLY EWD. THE REMNANTS OF HURRICANE ISAAC CONTINUE TO DRIFT EWD
THRU THE OH VALLEY S OF THE UPR RDG AXIS. WARM CONVEYOR BELT MSTR
RIBBON...IN ADVANCE OF COLD FNT MOVING THRU MN THAT IS ATTENDANT TO
SASKATCHEWAN OCCLUSION...HAS PUSHED INTO ERN MN/WRN UPR MI.
HOWEVER...CIRCULATION ARND ISAAC HAS LIMITED MSTR INFLOW INTO THIS
SYSTEM AS EVIDENCED BY VERY DRY AIRMASS SHOWN ON THE 00Z MPX RAOB
AND H85 DEWPT DEPRESSIONS NEAR 20C STRETCHING FM THAT SITE SWWD INTO
THE CENTRAL PLAINS. SINCE THIS DRY AIR IS FEEDING NEWD TOWARD NE
MN/UPR MI IN THE SSW SFC-H85 FLOW AHEAD OF COLD FNT...AT 06Z THERE
WAS NO PCPN FALLING S OF THE CNDN BORDER FM THIS CLD DESPITE STEEP
MID LVL LAPSE RATES AND MUCAPE 500-1000 J/KG AS SHOWN BY SPC
MESOANALYSIS. ISOLD -SHRA/A FEW LTG STRIKES WERE EVIDENT IN ONTARIO
WHERE MSTR IS DEEPER PER 00Z YPL RAOB CLOSER TO SHARPER DEEP LYR
QVECTOR CNVGC ASSOCIATED WITH OCCLUSION TO THE W. HOWEVER...APRCH OF
70KT H3 JET MAX IN THE NRN PLAINS/SOME UPR DVGC HAS CAUSED MORE
SHRA/TS TO DVLP OVER WRN LK SUP CLOSER TO FCST ISSUANCE. BEHIND THE
COLD FNT IN THE NRN PLAINS...00Z ABERDEEN SDAKOTA AND BISMARCK RAOBS
SHOW A VERY DRY AIRMASS. LATEST WV IMAGERY SHOWS THIS DRIER AIR ALF
SPREADING EWD.
MAIN FCST CONCERNS IN THE SHORT TERM ARE SHRA/TS CHCS TODAY AS COLD
FNT/MSTR RIBBON PRESS TO THE E.
TODAY...COLD FNT IN MN IS PROGGED TO DRIFT INTO UPR MI AND DISSIPATE
AS THIS BNDRY OUTRUNS THE CLOSED LO IN SASKATCHEWAN THAT IS PROGGED
TO DRIFT ONLY SLOWLY INTO MANITOBA. PCPN CHCS WL BE HINDERED BY DRY
ADVECTION NOTED ABOVE AND EXIT OF DEEP LYR QVECTOR CNVGC TO THE N.
HOWEVER...BULK OF MODELS SHOWED THE INCRSG H4-2 UPR DVGC EARLY THIS
MRNG IN ADVANCE OF JET MAX MOVING ENEWD THRU THE NRN PLAINS...SO
WENT WITH SCT -SHRA/TSRA TO START OFF FCST PERIOD OVER THE W WITH
THE SOMEWHAT HIER POPS FARTHER TO THE N CLOSER TO DEEPER MSTR/
LINGERING DEEP LYR QVECTOR CNVGC. THIS UPR DVGC IS PROGGED TO EXIT
TO THE NE BY MID MRNG...SO EXPECT POPS TO DIMINISH FOR A TIME.
QUESTION THEN BECOMES WHETHER DAYTIME HEATING CAN INVIGORATE DIURNAL
CONVECTION IN ABSENCE OF APPRECIABLE DYNAMIC SUPPORT AND AGAINST
ONSLAUGHT OF INCOMING DRY AIR THAT IS PROGGED TO DROP KINX BLO 10
OVER THE W HALF BY 18Z FOLLOWING THE DISSIPATING COLD FROPA PER
FAVORED GFS THAT BEST MATCHES WV IMAGERY TRENDS OF VIGOROUS DRYING
ALF MOVING E FM THE NRN PLAINS. BEST SHOT FOR THIS CONVECTION
APPEARS TO BE OVER THE E AND SCNTRL...WHERE KINX IS PROGGED TO
REMAIN NEAR 30 THRU 18Z AND WHERE DVLPG LK BREEZES MIGHT ENHANCE
LLVL CNVGC. BUT EVEN IN THIS AREA...KINX IS FCST TO FALL BLO 20 BY
00Z EXCEPT FOR AREAS NEAR LK MI. AS FOR SVR THREAT...MODELS DEPICT
DEEP LYR SHEAR AS HI AS 30-35 KTS OVER THE SCNTRL AT 18Z. MODIFIED
GFS FCST SDNG FOR ESC AT 18Z FOR SFC T/TD 83/66 YIELDS SBCAPE NEAR
1400 J/KG DESPITE LESS IMPRESSIVE MID LVL LAPSE RATES FCST IN THAT
AREA. WITH VIGOROUS DRYING ALF...SFC-10K DELTA THETA-E IS PROGGED TO
INCRS TO A SGNFT 25-30C BY LATE IN THE DAY...INCRSG THE DCAPE IN THE
PRESENCE OF UNIDIRECTIONAL WLY FLOW ALF/THREAT FOR DAMAGING WINDS.
DESPITE MID LVL DRYING...FCST HI WBZ NEAR 13K FT WOULD PROBABLY
MINIMIZE THE POTENTIAL FOR LARGE HAIL. BUT MAIN CONCERN IS HOW
VIGOROUS MID LVL DRYING WL IMPACT SHRA/TS CHCS. IN FACT...THE
GREATER SHEAR MIGHT ACT TO ENTRAIN SO MUCH DRIER AIR INTO THE STORM
TOWERS AND LIMIT THE INTENSITY OF THE CONVECTION. WL CONTINUE TO
MENTION THE THREAT OF SOME STRONGER STORMS IN THE HWO. AS FOR HI
TEMPS...MIXING TO H85 ON GFS FCST SDNGS YIELDS HI TEMPS REACHING THE
MID/UPR 80S AWAY FM LK MODERATION...IN GOOD AGREEMENT WITH MAX TEMPS
OBSVD UPSTREAM ON SUN.
TNGT...WITH VIGOROUS UPR DRYING PER THE GFS THAT CAUSES H85-5 MEAN
RH TO FALL AS LO AS 20 PCT BY 06Z...ANY LINGERING SHRA/TS OVER THE
SE CWA IN THE EARLY EVNG WL END WITH LOSS OF DAYTIME HEATING IN THE
ABSENCE OF ANY DYNAMIC SUPPORT. CONSIDERING DRYNESS OF INCOMING
AIRMASS AND LGT WINDS UNDER BUBBLE HI PRES BLDG INTO THE AREA...
TENDED TOWARD THE LOWER GFS GUIDANCE FOR MIN TEMPS. VIGOROUS DRYING
ALF/LGT WINDS FAVOR FOG DEVELOPMENT...SO WENT WITH AREAS OF FOG OVER
MUCH OF THE INTERIOR.
.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 429 AM EDT MON SEP 3 2012
THE PERIOD STARTS 12Z TUE WITH A CLOSED UPPER LOW OVER NRN
MANITOBA...AND A SFC TROUGH/WEAK COLD FRONT W OF THE CWA. SHORTWAVE
ENERGY IS THEN COMBINED INTO THE SRN SIDE OF THE UPPER LOW THROUGH
WED...CAUSING THE SYSTEM TO MOVE FARTHER W TO FAR NW ONTARIO BY 00Z
THU. EXACTLY WHEN AND WHERE THE SHORTWAVE ENERGY MOVES WILL GREATLY
IMPACT THE FORECAST FOR TUE AND TUE NIGHT...SO CONFIDENCE IS LOWER
FOR THIS TIME PERIOD. WE COULD STAY DRY ACROSS MOST OF THE CWA ON
TUE...AS THE 12Z/02 ECMWF SHOWS DUE TO THE SHORTWAVE STAYING FATHER
TO THE N THAN IN OTHER MODELS. ALSO...MODEL FORECAST SOUNDING SHOW
DIFFERENCES BETWEEN LOW LEVEL MOISTURE WHICH WILL RESULT IN
INCREASED TO DECREASED CIN. WILL NOT CHANGE THE PREVIOUS POP
FORECAST WITH SLIGHT CHANCE TO LOW CHANCE POPS MAINLY IN THE
AFTERNOON. IF SHOWERS AND THUNDERSTORMS DO DEVELOP...THERE MAY BE
SOME STRONG TUE AFTERNOON AS CAPE INCREASES TO AOA 1500 J/KG BUT
0-6 KM SHEAR REMAINS BELOW 25 KTS.
A STRONGER COLD FRONT/SFC TROUGH SHOULD MOVE THROUGH ON WED...BUT
TIMING AND INTENSITY REMAINS IN QUESTION AS MODELS DO NOT HANDLE THE
SITUATION WELL. THIS IS AGAIN RELATED TO THE PATH THE SHORTWAVE
TAKES. THE DIFFERENCES BETWEEN TIMING PLAY OUT THE MOST WITH
THUNDERSTORM INTENSITY ON WED...WITH THE SLOWER GUIDANCE BRING THE
FRONT THROUGH AROUND PEAK HEATING WHICH WOULD RESULT IN MORE
INSTABILITY. THE FASTER MODELS MOVE THINGS THROUGH EARLIER AND
THEREFORE...INSTABILITY RESULTING FROM DAYTIME HEATING IS MAXIMIZED
AOA 1500 J/KG. 0-6KM SHEAR SHOULD BE ON THE ORDER OF 40-50
KTS...WITH 0-1KM SHEAR OF AROUND 15 KTS. FLOW WILL BE MOSTLY
UNIDIRECTIONAL...SO THE SHEAR IS MOSTLY SPEED SHEAR. MORE ALONG THE
LINES OF WORST CASE SCENARIO REGARDING TIMING/INSTABILITY...SOME
STORMS COULD BE SEVERE IN THE AFTERNOON WITH WIND GUSTS BEING THE
PRIMARY HAZARD /DUE PARTY TO DRY MID LEVELS/. THERE WOULD BE A LARGE
HAIL THREAT...BUT THAT IS MORE CONDITIONAL. REGARDLESS OF TIMING OF
THE FRONT...PRECIP DOES LOOK MORE CERTAIN THAN ANY OTHER DAY IN THE
EXTENDED...BUT THAT SHORTWAVE WILL MAKE THINGS TRICKY. INCREASED
POPS TO LIKELY...ESPECIALLY CENTRAL AND E...AND HIGH CHANCE POPS
OVER THE FAR W.
THE UPPER LOW WILL CONTINUE TO MOVE EVERY SO SLOWLY ESE...AND WILL
BE CLOSEST TO THE CWA THU NIGHT. EXPECT 850MB TEMPS AROUND 4-6C THU
INTO FRI..WHICH MAY LEAD TO SOME LAKE EFFECT RAIN DOWNWIND OF N/NW
WINDS. MODEL AGREEMENT AND CONTINUITY DEGRADE SIGNIFICANTLY FRIDAY
THROUGH SUNDAY...SO CONFIDENCE IS SIGNIFICANTLY LOWER FOR NEXT
WEEKEND. IT DOES APPEAR...HOWEVER...THAT A RETURN TO OR EVEN BELOW
NEAR NORMAL TEMPERATURES IS IN STORE FOR THU THROUGH SUN. USED
CONSENSUS OF MODEL GUIDANCE GIVEN UNCERTAINTY.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 139 PM EDT MON SEP 3 2012
WITH WEAK SFC TROF MOVING ACROSS UPPER MI...KSAW MAY BE IMPACTED BY
BRIEF SHRA/TSRA AND MVFR CONDITIONS OVER THE NEXT COUPLE OF HRS.
TROF IS ALREADY PAST KIWD/KCMX...SO THE AFTN WILL HAVE VFR CONDITIONS
AND NO PCPN AT THOSE 2 SITES. WITH SFC WINDS DIMINISHING TO
LIGHT/CALM UNDER UPPER LEVEL DRYING...FOG IS LIKELY TO FORM TONIGHT
WITH IFR...POSSIBLE LIFR...CONDITIONS. FOG WILL DISSIPATE WITHIN A
COUPLE OF HRS AFTER SUNRISE TUE. NEXT DISTURBANCE APPROACHING THE AREA
MAY TRIGGER ISOLD/SCT CONVECTION TUE...BUT MOST LIKELY NOT UNTIL BEYOND
THIS FCST PERIOD.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 429 AM EDT MON SEP 3 2012
EXPECT S WINDS UP TO 20 KTS IN ADVANCE OF AN APPROACHING COLD FRONT
TO DIMINISH TODAY AS THE FRONT TENDS TO WEAKEN. LIGHT WINDS WILL
THEN PREVAIL THRU TONIGHT AS A WEAK HI PRES SYSTEM MOVES INTO THE
UPPER GREAT LAKES. A SERIES OF LOW PRESSURE SYSTEMS AND COLD FRONTS
WILL MOVE NEAR LAKE SUPERIOR TUESDAY THROUGH SUNDAY...LEADING TO
PERIODS OF INCREASED WINDS. HOWEVER...AT THIS TIME WINDS ARE EXPECTED
TO REMAIN BELOW 25KTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...KC
LONG TERM...TITUS
AVIATION...ROLFSON
MARINE...KC/TITUS
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
731 AM EDT MON SEP 3 2012
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 429 AM EDT MON SEP 3 2012
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW WSW FLOW ALF OVER
THE UPR GRT LKS BTWN UPR RDG EXTENDING FM THE PLAINS INTO LWR MI AND
DEEP...OCCLUDED LO OVER NRN SASKATCHEWAN THAT IS DRIFTING ONLY
SLOWLY EWD. THE REMNANTS OF HURRICANE ISAAC CONTINUE TO DRIFT EWD
THRU THE OH VALLEY S OF THE UPR RDG AXIS. WARM CONVEYOR BELT MSTR
RIBBON...IN ADVANCE OF COLD FNT MOVING THRU MN THAT IS ATTENDANT TO
SASKATCHEWAN OCCLUSION...HAS PUSHED INTO ERN MN/WRN UPR MI.
HOWEVER...CIRCULATION ARND ISAAC HAS LIMITED MSTR INFLOW INTO THIS
SYSTEM AS EVIDENCED BY VERY DRY AIRMASS SHOWN ON THE 00Z MPX RAOB
AND H85 DEWPT DEPRESSIONS NEAR 20C STRETCHING FM THAT SITE SWWD INTO
THE CENTRAL PLAINS. SINCE THIS DRY AIR IS FEEDING NEWD TOWARD NE
MN/UPR MI IN THE SSW SFC-H85 FLOW AHEAD OF COLD FNT...AT 06Z THERE
WAS NO PCPN FALLING S OF THE CNDN BORDER FM THIS CLD DESPITE STEEP
MID LVL LAPSE RATES AND MUCAPE 500-1000 J/KG AS SHOWN BY SPC
MESOANALYSIS. ISOLD -SHRA/A FEW LTG STRIKES WERE EVIDENT IN ONTARIO
WHERE MSTR IS DEEPER PER 00Z YPL RAOB CLOSER TO SHARPER DEEP LYR
QVECTOR CNVGC ASSOCIATED WITH OCCLUSION TO THE W. HOWEVER...APRCH OF
70KT H3 JET MAX IN THE NRN PLAINS/SOME UPR DVGC HAS CAUSED MORE
SHRA/TS TO DVLP OVER WRN LK SUP CLOSER TO FCST ISSUANCE. BEHIND THE
COLD FNT IN THE NRN PLAINS...00Z ABERDEEN SDAKOTA AND BISMARCK RAOBS
SHOW A VERY DRY AIRMASS. LATEST WV IMAGERY SHOWS THIS DRIER AIR ALF
SPREADING EWD.
MAIN FCST CONCERNS IN THE SHORT TERM ARE SHRA/TS CHCS TODAY AS COLD
FNT/MSTR RIBBON PRESS TO THE E.
TODAY...COLD FNT IN MN IS PROGGED TO DRIFT INTO UPR MI AND DISSIPATE
AS THIS BNDRY OUTRUNS THE CLOSED LO IN SASKATCHEWAN THAT IS PROGGED
TO DRIFT ONLY SLOWLY INTO MANITOBA. PCPN CHCS WL BE HINDERED BY DRY
ADVECTION NOTED ABOVE AND EXIT OF DEEP LYR QVECTOR CNVGC TO THE N.
HOWEVER...BULK OF MODELS SHOWED THE INCRSG H4-2 UPR DVGC EARLY THIS
MRNG IN ADVANCE OF JET MAX MOVING ENEWD THRU THE NRN PLAINS...SO
WENT WITH SCT -SHRA/TSRA TO START OFF FCST PERIOD OVER THE W WITH
THE SOMEWHAT HIER POPS FARTHER TO THE N CLOSER TO DEEPER MSTR/
LINGERING DEEP LYR QVECTOR CNVGC. THIS UPR DVGC IS PROGGED TO EXIT
TO THE NE BY MID MRNG...SO EXPECT POPS TO DIMINISH FOR A TIME.
QUESTION THEN BECOMES WHETHER DAYTIME HEATING CAN INVIGORATE DIURNAL
CONVECTION IN ABSENCE OF APPRECIABLE DYNAMIC SUPPORT AND AGAINST
ONSLAUGHT OF INCOMING DRY AIR THAT IS PROGGED TO DROP KINX BLO 10
OVER THE W HALF BY 18Z FOLLOWING THE DISSIPATING COLD FROPA PER
FAVORED GFS THAT BEST MATCHES WV IMAGERY TRENDS OF VIGOROUS DRYING
ALF MOVING E FM THE NRN PLAINS. BEST SHOT FOR THIS CONVECTION
APPEARS TO BE OVER THE E AND SCNTRL...WHERE KINX IS PROGGED TO
REMAIN NEAR 30 THRU 18Z AND WHERE DVLPG LK BREEZES MIGHT ENHANCE
LLVL CNVGC. BUT EVEN IN THIS AREA...KINX IS FCST TO FALL BLO 20 BY
00Z EXCEPT FOR AREAS NEAR LK MI. AS FOR SVR THREAT...MODELS DEPICT
DEEP LYR SHEAR AS HI AS 30-35 KTS OVER THE SCNTRL AT 18Z. MODIFIED
GFS FCST SDNG FOR ESC AT 18Z FOR SFC T/TD 83/66 YIELDS SBCAPE NEAR
1400 J/KG DESPITE LESS IMPRESSIVE MID LVL LAPSE RATES FCST IN THAT
AREA. WITH VIGOROUS DRYING ALF...SFC-10K DELTA THETA-E IS PROGGED TO
INCRS TO A SGNFT 25-30C BY LATE IN THE DAY...INCRSG THE DCAPE IN THE
PRESENCE OF UNIDIRECTIONAL WLY FLOW ALF/THREAT FOR DAMAGING WINDS.
DESPITE MID LVL DRYING...FCST HI WBZ NEAR 13K FT WOULD PROBABLY
MINIMIZE THE POTENTIAL FOR LARGE HAIL. BUT MAIN CONCERN IS HOW
VIGOROUS MID LVL DRYING WL IMPACT SHRA/TS CHCS. IN FACT...THE
GREATER SHEAR MIGHT ACT TO ENTRAIN SO MUCH DRIER AIR INTO THE STORM
TOWERS AND LIMIT THE INTENSITY OF THE CONVECTION. WL CONTINUE TO
MENTION THE THREAT OF SOME STRONGER STORMS IN THE HWO. AS FOR HI
TEMPS...MIXING TO H85 ON GFS FCST SDNGS YIELDS HI TEMPS REACHING THE
MID/UPR 80S AWAY FM LK MODERATION...IN GOOD AGREEMENT WITH MAX TEMPS
OBSVD UPSTREAM ON SUN.
TNGT...WITH VIGOROUS UPR DRYING PER THE GFS THAT CAUSES H85-5 MEAN
RH TO FALL AS LO AS 20 PCT BY 06Z...ANY LINGERING SHRA/TS OVER THE
SE CWA IN THE EARLY EVNG WL END WITH LOSS OF DAYTIME HEATING IN THE
ABSENCE OF ANY DYNAMIC SUPPORT. CONSIDERING DRYNESS OF INCOMING
AIRMASS AND LGT WINDS UNDER BUBBLE HI PRES BLDG INTO THE AREA...
TENDED TOWARD THE LOWER GFS GUIDANCE FOR MIN TEMPS. VIGOROUS DRYING
ALF/LGT WINDS FAVOR FOG DEVELOPMENT...SO WENT WITH AREAS OF FOG OVER
MUCH OF THE INTERIOR.
.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 429 AM EDT MON SEP 3 2012
THE PERIOD STARTS 12Z TUE WITH A CLOSED UPPER LOW OVER NRN
MANITOBA...AND A SFC TROUGH/WEAK COLD FRONT W OF THE CWA. SHORTWAVE
ENERGY IS THEN COMBINED INTO THE SRN SIDE OF THE UPPER LOW THROUGH
WED...CAUSING THE SYSTEM TO MOVE FARTHER W TO FAR NW ONTARIO BY 00Z
THU. EXACTLY WHEN AND WHERE THE SHORTWAVE ENERGY MOVES WILL GREATLY
IMPACT THE FORECAST FOR TUE AND TUE NIGHT...SO CONFIDENCE IS LOWER
FOR THIS TIME PERIOD. WE COULD STAY DRY ACROSS MOST OF THE CWA ON
TUE...AS THE 12Z/02 ECMWF SHOWS DUE TO THE SHORTWAVE STAYING FATHER
TO THE N THAN IN OTHER MODELS. ALSO...MODEL FORECAST SOUNDING SHOW
DIFFERENCES BETWEEN LOW LEVEL MOISTURE WHICH WILL RESULT IN
INCREASED TO DECREASED CIN. WILL NOT CHANGE THE PREVIOUS POP
FORECAST WITH SLIGHT CHANCE TO LOW CHANCE POPS MAINLY IN THE
AFTERNOON. IF SHOWERS AND THUNDERSTORMS DO DEVELOP...THERE MAY BE
SOME STRONG TUE AFTERNOON AS CAPE INCREASES TO AOA 1500 J/KG BUT
0-6 KM SHEAR REMAINS BELOW 25 KTS.
A STRONGER COLD FRONT/SFC TROUGH SHOULD MOVE THROUGH ON WED...BUT
TIMING AND INTENSITY REMAINS IN QUESTION AS MODELS DO NOT HANDLE THE
SITUATION WELL. THIS IS AGAIN RELATED TO THE PATH THE SHORTWAVE
TAKES. THE DIFFERENCES BETWEEN TIMING PLAY OUT THE MOST WITH
THUNDERSTORM INTENSITY ON WED...WITH THE SLOWER GUIDANCE BRING THE
FRONT THROUGH AROUND PEAK HEATING WHICH WOULD RESULT IN MORE
INSTABILITY. THE FASTER MODELS MOVE THINGS THROUGH EARLIER AND
THEREFORE...INSTABILITY RESULTING FROM DAYTIME HEATING IS MAXIMIZED
AOA 1500 J/KG. 0-6KM SHEAR SHOULD BE ON THE ORDER OF 40-50
KTS...WITH 0-1KM SHEAR OF AROUND 15 KTS. FLOW WILL BE MOSTLY
UNIDIRECTIONAL...SO THE SHEAR IS MOSTLY SPEED SHEAR. MORE ALONG THE
LINES OF WORST CASE SCENARIO REGARDING TIMING/INSTABILITY...SOME
STORMS COULD BE SEVERE IN THE AFTERNOON WITH WIND GUSTS BEING THE
PRIMARY HAZARD /DUE PARTY TO DRY MID LEVELS/. THERE WOULD BE A LARGE
HAIL THREAT...BUT THAT IS MORE CONDITIONAL. REGARDLESS OF TIMING OF
THE FRONT...PRECIP DOES LOOK MORE CERTAIN THAN ANY OTHER DAY IN THE
EXTENDED...BUT THAT SHORTWAVE WILL MAKE THINGS TRICKY. INCREASED
POPS TO LIKELY...ESPECIALLY CENTRAL AND E...AND HIGH CHANCE POPS
OVER THE FAR W.
THE UPPER LOW WILL CONTINUE TO MOVE EVERY SO SLOWLY ESE...AND WILL
BE CLOSEST TO THE CWA THU NIGHT. EXPECT 850MB TEMPS AROUND 4-6C THU
INTO FRI..WHICH MAY LEAD TO SOME LAKE EFFECT RAIN DOWNWIND OF N/NW
WINDS. MODEL AGREEMENT AND CONTINUITY DEGRADE SIGNIFICANTLY FRIDAY
THROUGH SUNDAY...SO CONFIDENCE IS SIGNIFICANTLY LOWER FOR NEXT
WEEKEND. IT DOES APPEAR...HOWEVER...THAT A RETURN TO OR EVEN BELOW
NEAR NORMAL TEMPERATURES IS IN STORE FOR THU THROUGH SUN. USED
CONSENSUS OF MODEL GUIDANCE GIVEN UNCERTAINTY.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 730 AM EDT MON SEP 3 2012
EXPECT TS THAT IMPACTED CMX TO BE OVER BY 12Z..WITH DRY AIR
FOLLOWING IN THE WAKE OF A WEAK COLD FRONTAL PASSAGE ENDING THE PCPN
THREAT THERE AND AT IWD BY MID MRNG AS THE BETTER DYNAMIC SUPPORT
LIFTS TO THE N. SOME SHRA/TS MAY IMPACT SAW LATE THIS MRNG INTO
EARLY AFTN AS WELL WITH DAYTIME HEATING COINCIDING WITH THE ARRIVAL
OF THE FNT. BUT THE ARRIVAL OF DRIER AIR ALF SHOULD END THE SHRA
THREAT THERE AS WELL. ALTHOUGH CIGS/VSBY MAY BE LOWER UNDER ANY
HEAVIER SHRA...VFR CONDITIONS SHOULD BE THE RULE AT ALL SITES INTO
THIS EVNG. WITH LGT NEAR SFC WINDS UNDER THE UPR LVL DRYING...FOG IS
LIKELY TO FORM AT SAW/IWD OVERNGT...WITH IFR CONDITIONS POSSIBLE.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 429 AM EDT MON SEP 3 2012
EXPECT S WINDS UP TO 20 KTS IN ADVANCE OF AN APPROACHING COLD FRONT
TO DIMINISH TODAY AS THE FRONT TENDS TO WEAKEN. LIGHT WINDS WILL
THEN PREVAIL THRU TONIGHT AS A WEAK HI PRES SYSTEM MOVES INTO THE
UPPER GREAT LAKES. A SERIES OF LOW PRESSURE SYSTEMS AND COLD FRONTS
WILL MOVE NEAR LAKE SUPERIOR TUESDAY THROUGH SUNDAY...LEADING TO
PERIODS OF INCREASED WINDS. HOWEVER...AT THIS TIME WINDS ARE EXPECTED
TO REMAIN BELOW 25KTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...KC
LONG TERM...TITUS
AVIATION...KC
MARINE...KC/TITUS
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
430 AM EDT MON SEP 3 2012
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 429 AM EDT MON SEP 3 2012
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW WSW FLOW ALF OVER
THE UPR GRT LKS BTWN UPR RDG EXTENDING FM THE PLAINS INTO LWR MI AND
DEEP...OCCLUDED LO OVER NRN SASKATCHEWAN THAT IS DRIFTING ONLY
SLOWLY EWD. THE REMNANTS OF HURRICANE ISAAC CONTINUE TO DRIFT EWD
THRU THE OH VALLEY S OF THE UPR RDG AXIS. WARM CONVEYOR BELT MSTR
RIBBON...IN ADVANCE OF COLD FNT MOVING THRU MN THAT IS ATTENDANT TO
SASKATCHEWAN OCCLUSION...HAS PUSHED INTO ERN MN/WRN UPR MI.
HOWEVER...CIRCULATION ARND ISAAC HAS LIMITED MSTR INFLOW INTO THIS
SYSTEM AS EVIDENCED BY VERY DRY AIRMASS SHOWN ON THE 00Z MPX RAOB
AND H85 DEWPT DEPRESSIONS NEAR 20C STRETCHING FM THAT SITE SWWD INTO
THE CENTRAL PLAINS. SINCE THIS DRY AIR IS FEEDING NEWD TOWARD NE
MN/UPR MI IN THE SSW SFC-H85 FLOW AHEAD OF COLD FNT...AT 06Z THERE
WAS NO PCPN FALLING S OF THE CNDN BORDER FM THIS CLD DESPITE STEEP
MID LVL LAPSE RATES AND MUCAPE 500-1000 J/KG AS SHOWN BY SPC
MESOANALYSIS. ISOLD -SHRA/A FEW LTG STRIKES WERE EVIDENT IN ONTARIO
WHERE MSTR IS DEEPER PER 00Z YPL RAOB CLOSER TO SHARPER DEEP LYR
QVECTOR CNVGC ASSOCIATED WITH OCCLUSION TO THE W. HOWEVER...APRCH OF
70KT H3 JET MAX IN THE NRN PLAINS/SOME UPR DVGC HAS CAUSED MORE
SHRA/TS TO DVLP OVER WRN LK SUP CLOSER TO FCST ISSUANCE. BEHIND THE
COLD FNT IN THE NRN PLAINS...00Z ABERDEEN SDAKOTA AND BISMARCK RAOBS
SHOW A VERY DRY AIRMASS. LATEST WV IMAGERY SHOWS THIS DRIER AIR ALF
SPREADING EWD.
MAIN FCST CONCERNS IN THE SHORT TERM ARE SHRA/TS CHCS TODAY AS COLD
FNT/MSTR RIBBON PRESS TO THE E.
TODAY...COLD FNT IN MN IS PROGGED TO DRIFT INTO UPR MI AND DISSIPATE
AS THIS BNDRY OUTRUNS THE CLOSED LO IN SASKATCHEWAN THAT IS PROGGED
TO DRIFT ONLY SLOWLY INTO MANITOBA. PCPN CHCS WL BE HINDERED BY DRY
ADVECTION NOTED ABOVE AND EXIT OF DEEP LYR QVECTOR CNVGC TO THE N.
HOWEVER...BULK OF MODELS SHOWED THE INCRSG H4-2 UPR DVGC EARLY THIS
MRNG IN ADVANCE OF JET MAX MOVING ENEWD THRU THE NRN PLAINS...SO
WENT WITH SCT -SHRA/TSRA TO START OFF FCST PERIOD OVER THE W WITH
THE SOMEWHAT HIER POPS FARTHER TO THE N CLOSER TO DEEPER MSTR/
LINGERING DEEP LYR QVECTOR CNVGC. THIS UPR DVGC IS PROGGED TO EXIT
TO THE NE BY MID MRNG...SO EXPECT POPS TO DIMINISH FOR A TIME.
QUESTION THEN BECOMES WHETHER DAYTIME HEATING CAN INVIGORATE DIURNAL
CONVECTION IN ABSENCE OF APPRECIABLE DYNAMIC SUPPORT AND AGAINST
ONSLAUGHT OF INCOMING DRY AIR THAT IS PROGGED TO DROP KINX BLO 10
OVER THE W HALF BY 18Z FOLLOWING THE DISSIPATING COLD FROPA PER
FAVORED GFS THAT BEST MATCHES WV IMAGERY TRENDS OF VIGOROUS DRYING
ALF MOVING E FM THE NRN PLAINS. BEST SHOT FOR THIS CONVECTION
APPEARS TO BE OVER THE E AND SCNTRL...WHERE KINX IS PROGGED TO
REMAIN NEAR 30 THRU 18Z AND WHERE DVLPG LK BREEZES MIGHT ENHANCE
LLVL CNVGC. BUT EVEN IN THIS AREA...KINX IS FCST TO FALL BLO 20 BY
00Z EXCEPT FOR AREAS NEAR LK MI. AS FOR SVR THREAT...MODELS DEPICT
DEEP LYR SHEAR AS HI AS 30-35 KTS OVER THE SCNTRL AT 18Z. MODIFIED
GFS FCST SDNG FOR ESC AT 18Z FOR SFC T/TD 83/66 YIELDS SBCAPE NEAR
1400 J/KG DESPITE LESS IMPRESSIVE MID LVL LAPSE RATES FCST IN THAT
AREA. WITH VIGOROUS DRYING ALF...SFC-10K DELTA THETA-E IS PROGGED TO
INCRS TO A SGNFT 25-30C BY LATE IN THE DAY...INCRSG THE DCAPE IN THE
PRESENCE OF UNIDIRECTIONAL WLY FLOW ALF/THREAT FOR DAMAGING WINDS.
DESPITE MID LVL DRYING...FCST HI WBZ NEAR 13K FT WOULD PROBABLY
MINIMIZE THE POTENTIAL FOR LARGE HAIL. BUT MAIN CONCERN IS HOW
VIGOROUS MID LVL DRYING WL IMPACT SHRA/TS CHCS. IN FACT...THE
GREATER SHEAR MIGHT ACT TO ENTRAIN SO MUCH DRIER AIR INTO THE STORM
TOWERS AND LIMIT THE INTENSITY OF THE CONVECTION. WL CONTINUE TO
MENTION THE THREAT OF SOME STRONGER STORMS IN THE HWO. AS FOR HI
TEMPS...MIXING TO H85 ON GFS FCST SDNGS YIELDS HI TEMPS REACHING THE
MID/UPR 80S AWAY FM LK MODERATION...IN GOOD AGREEMENT WITH MAX TEMPS
OBSVD UPSTREAM ON SUN.
TNGT...WITH VIGOROUS UPR DRYING PER THE GFS THAT CAUSES H85-5 MEAN
RH TO FALL AS LO AS 20 PCT BY 06Z...ANY LINGERING SHRA/TS OVER THE
SE CWA IN THE EARLY EVNG WL END WITH LOSS OF DAYTIME HEATING IN THE
ABSENCE OF ANY DYNAMIC SUPPORT. CONSIDERING DRYNESS OF INCOMING
AIRMASS AND LGT WINDS UNDER BUBBLE HI PRES BLDG INTO THE AREA...
TENDED TOWARD THE LOWER GFS GUIDANCE FOR MIN TEMPS. VIGOROUS DRYING
ALF/LGT WINDS FAVOR FOG DEVELOPMENT...SO WENT WITH AREAS OF FOG OVER
MUCH OF THE INTERIOR.
.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 429 AM EDT MON SEP 3 2012
THE PERIOD STARTS 12Z TUE WITH A CLOSED UPPER LOW OVER NRN
MANITOBA...AND A SFC TROUGH/WEAK COLD FRONT W OF THE CWA. SHORTWAVE
ENERGY IS THEN COMBINED INTO THE SRN SIDE OF THE UPPER LOW THROUGH
WED...CAUSING THE SYSTEM TO MOVE FARTHER W TO FAR NW ONTARIO BY 00Z
THU. EXACTLY WHEN AND WHERE THE SHORTWAVE ENERGY MOVES WILL GREATLY
IMPACT THE FORECAST FOR TUE AND TUE NIGHT...SO CONFIDENCE IS LOWER
FOR THIS TIME PERIOD. WE COULD STAY DRY ACROSS MOST OF THE CWA ON
TUE...AS THE 12Z/02 ECMWF SHOWS DUE TO THE SHORTWAVE STAYING FATHER
TO THE N THAN IN OTHER MODELS. ALSO...MODEL FORECAST SOUNDING SHOW
DIFFERENCES BETWEEN LOW LEVEL MOISTURE WHICH WILL RESULT IN
INCREASED TO DECREASED CIN. WILL NOT CHANGE THE PREVIOUS POP
FORECAST WITH SLIGHT CHANCE TO LOW CHANCE POPS MAINLY IN THE
AFTERNOON. IF SHOWERS AND THUNDERSTORMS DO DEVELOP...THERE MAY BE
SOME STRONG TUE AFTERNOON AS CAPE INCREASES TO AOA 1500 J/KG BUT
0-6 KM SHEAR REMAINS BELOW 25 KTS.
A STRONGER COLD FRONT/SFC TROUGH SHOULD MOVE THROUGH ON WED...BUT
TIMING AND INTENSITY REMAINS IN QUESTION AS MODELS DO NOT HANDLE THE
SITUATION WELL. THIS IS AGAIN RELATED TO THE PATH THE SHORTWAVE
TAKES. THE DIFFERENCES BETWEEN TIMING PLAY OUT THE MOST WITH
THUNDERSTORM INTENSITY ON WED...WITH THE SLOWER GUIDANCE BRING THE
FRONT THROUGH AROUND PEAK HEATING WHICH WOULD RESULT IN MORE
INSTABILITY. THE FASTER MODELS MOVE THINGS THROUGH EARLIER AND
THEREFORE...INSTABILITY RESULTING FROM DAYTIME HEATING IS MAXIMIZED
AOA 1500 J/KG. 0-6KM SHEAR SHOULD BE ON THE ORDER OF 40-50
KTS...WITH 0-1KM SHEAR OF AROUND 15 KTS. FLOW WILL BE MOSTLY
UNIDIRECTIONAL...SO THE SHEAR IS MOSTLY SPEED SHEAR. MORE ALONG THE
LINES OF WORST CASE SCENARIO REGARDING TIMING/INSTABILITY...SOME
STORMS COULD BE SEVERE IN THE AFTERNOON WITH WIND GUSTS BEING THE
PRIMARY HAZARD /DUE PARTY TO DRY MID LEVELS/. THERE WOULD BE A LARGE
HAIL THREAT...BUT THAT IS MORE CONDITIONAL. REGARDLESS OF TIMING OF
THE FRONT...PRECIP DOES LOOK MORE CERTAIN THAN ANY OTHER DAY IN THE
EXTENDED...BUT THAT SHORTWAVE WILL MAKE THINGS TRICKY. INCREASED
POPS TO LIKELY...ESPECIALLY CENTRAL AND E...AND HIGH CHANCE POPS
OVER THE FAR W.
THE UPPER LOW WILL CONTINUE TO MOVE EVERY SO SLOWLY ESE...AND WILL
BE CLOSEST TO THE CWA THU NIGHT. EXPECT 850MB TEMPS AROUND 4-6C THU
INTO FRI..WHICH MAY LEAD TO SOME LAKE EFFECT RAIN DOWNWIND OF N/NW
WINDS. MODEL AGREEMENT AND CONTINUITY DEGRADE SIGNIFICANTLY FRIDAY
THROUGH SUNDAY...SO CONFIDENCE IS SIGNIFICANTLY LOWER FOR NEXT
WEEKEND. IT DOES APPEAR...HOWEVER...THAT A RETURN TO OR EVEN BELOW
NEAR NORMAL TEMPERATURES IS IN STORE FOR THU THROUGH SUN. USED
CONSENSUS OF MODEL GUIDANCE GIVEN UNCERTAINTY.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 121 AM EDT MON SEP 3 2012
ALTHOUGH A FEW -SHRA MAY ARRIVE AT KIWD/KCMX LATE TONIGHT AND AT
KSAW LATE MON MORNING AHEAD OF AN APPROACHING COLD FRONT...EXPECT
VFR CONDITIONS AS THE FRONTAL BOUNDARY MOVES THRU THE AREA TODAY AS
LOW-LEVEL DRY AIR HOLDS. THERE IS POTENTIAL FOR STRATUS/FOG TO
DEVELOP AT KSAW LATE MONDAY NIGHT AS MOIST SFC DEWPOINTS REMAIN AND
HIGH PRESSURE SETTLES OVER THE AREA. MODEST LOW-LEVEL JET AHEAD OF
COLD FRONT MAY RESULT IN LLWS AT KIWD/KCMX TONIGHT.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 429 AM EDT MON SEP 3 2012
EXPECT S WINDS UP TO 20 KTS IN ADVANCE OF AN APPROACHING COLD FRONT
TO DIMINISH TODAY AS THE FRONT TENDS TO WEAKEN. LIGHT WINDS WILL
THEN PREVAIL THRU TONIGHT AS A WEAK HI PRES SYSTEM MOVES INTO THE
UPPER GREAT LAKES. A SERIES OF LOW PRESSURE SYSTEMS AND COLD FRONTS
WILL MOVE NEAR LAKE SUPERIOR TUESDAY THROUGH SUNDAY...LEADING TO
PERIODS OF INCREASED WINDS. HOWEVER...AT THIS TIME WINDS ARE EXPECTED
TO REMAIN BELOW 25KTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...KC
LONG TERM...TITUS
AVIATION...VOSS
MARINE...KC/TITUS
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
122 AM EDT MON SEP 3 2012
.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 347 PM EDT SUN SEP 2 2012
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A STRONG SHORTWAVE/MID
LEVEL LOW MOVING NE THRU CNTRL SASKATCHEWAN. DOWNSTREAM RIDGE
EXTENDS FROM THE SW PLAINS THRU THE UPPER LAKES WHILE REMNANT OF
ISAAC DRIFTS THRU THE LWR OHIO VALLEY. DUE TO ISAAC...MOISTURE
RETURN THRU THE PLAINS HAS BEEN VERY LIMITED AS 12Z RAOBS SHOW 850MB
DWPT DEPRESSIONS BTWN 15-25C. NONETHELESS...SCT HIGH BASED
-SHRA/TSRA HAVE BEEN OCCURRING ACROSS THE DAKOTAS INTO NW MN TODAY
IN THE VCNTY OF COLD FRONT ASSOCIATED WITH THE PARENT SHORTWAVE OVER
SASKATCHEWAN. A COUPLE OF MINOR SHORTWAVES APPEAR TO BE AIDING THE
CONVECTION. IN THE SHORT TERM...MAIN FOCUS WILL BE ON PCPN CHANCES
LATE TONIGHT THRU MON AS WEAKENING COLD FRONT ARRIVES.
WITH ONLY A NARROW RIBBON OF MOISTURE SUPPORTING PCPN TO THE W...THE
EVENING HRS TONIGHT WILL REMAIN DRY WHILE AWAITING COLD
FRONT/MOISTURE RIBBON TO MOVE CLOSER. IN CONJUNCTION WITH THE COLD
FRONT...A SHORTWAVE NOW OVER THE DAKOTAS WILL LIFT NE TONIGHT. ALONG TAIL
OF WAVE AND LEFT EXIT OF SUPPORTING JET STREAK...SHOULD SEE A BAND
OF SCT CONVECTION TONIGHT. THAT CONVECTION MAY SHIFT OUT OVER LAKE
SUPERIOR AND NW UPPER MI LATE TONIGHT. AS FOR TEMPS...THE HIGHEST
MIN TEMPS TONIGHT WILL BE IN THE DOWNSLOPE AREAS NEAR LAKE
SUPERIOR...PARTICULARLY THE W WHERE MOISTENING WILL BE MORE
PRONOUNCED. TEMPS SHOULDN`T FALL LWR THAN THE MID/UPPER 60S IN THOSE
AREAS. 50S WILL BE THE RULE OVER THE SCNTRL/E.
SHORTWAVE/MID LEVEL LOW CURRENTLY OVER SASKATCHEWAN DRIFTS INTO NRN
MANITOBA MON. WITH MAIN SYSTEM WELL TO THE NW OF HERE...SFC COLD
FRONT WILL BE WEAKENING AS IT REACHES UPPER MI. LACK OF DYNAMICS AND
DIMINISHING LOW-LEVEL CONVERGENCE ALONG FRONT WILL WORK TO LIMIT
COVERAGE OF CONVECTION MON...ESPECIALLY SINCE THERE WILL BE SOME DRY
AIR TO OVERCOME. HOWEVER...NARROW RIBBON OF BOUNDARY LAYER MOISTURE
SHOULD BE SUFFICIENT FOR ISOLD/SCT CONVECTION. AS AFORMENTIONED JET
STREAK AIDING PCPN LATE TONIGHT SHIFTS NE...THE RIGHT ENTRANCE OF
THE JET WILL PROBABLY PROVIDE BEST SUPPORT FOR NEW CONVECTION IN THE
AFTN HRS OVER SCNTRL UPPER MI INTO NE WI. PROVIDED MLCAPE INCREASES
TO UPWARDS OF 1500-2000J/KG PER GFS AND ESPECIALLY NAM...DEEP LAYER
SHEAR OF 30-40KT WILL SUPPORT ORGANIZED STORMS AND SVR POTENTIAL IF
ANY STORMS DO DEVELOP. COVERAGE OF SVR STORMS WOULD LIKELY BE ISOLD.
.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 347 PM EDT SUN SEP 2 2012
LONG TERM PERIOD STARTS OUT WITH UPPER LOW OVER MANITOBA WHILE
ADDITIONAL SHORTWAVE TROUGH CURRENTLY DIGGING INTO FAR NORTHERN
BRITISH COLUMBIA MERGES WITH THE LOW ON WEDNESDAY. INITIAL FRONT
THAT MOVES THROUGH UPR MICHIGAN ON LABOR DAY LIKELY STALLS OUT
MONDAY NIGHT INTO TUESDAY AS IT PARALLELS UPPER FLOW.
MAJORITY OF SHRA/TSRA...ALBEIT ONLY ISOLD/SCT COVERAGE...SHOULD BE
DIMINISHING BY LATER MONDAY NIGHT. KEPT SMALL POPS IN ONLY FOR THE
SOUTH AND EAST CWA AS THOSE AREAS STAY IN AT LEAST A WEAK AREA OF
RIGHT ENTRANCE JET FORCING. LINGERED SLIGHT CHANCES FOR THE SAME
AREAS THROUGH MOST OF THE NIGHT AS THE SURFACE FRONT REMAINS IN THE
VICINITY AND LOW-LEVEL MOISTURE POOLS ALONG THE BOUNDARY. VERY SMALL
CHANCES BUT CAN NOT COMPLETELY PULL THE POPS JUST YET.
FRONT COULD SERVE AS FOCUS FOR MORE SHRA/TSRA ON TUESDAY AS NAM/00Z
ECMWF INDICATE H85 TROUGH AND THETA-E ADVECTION ARRIVES DURING PEAK
HEATING OF THE AFTERNOON. H85 DWPNTS ON THE LOW SIDE TO START THE
DAY...SO SHOULD SEE BETTER CHANCES OF SHRA/TSRA AFTERNOON AND
EVENING...SPREADING FROM WEST TO EAST AS H85 TROUGH CROSSES AREA.
THOUGH 0-6KM SHEAR 20-25 KTS NOT TOO IMPRESSIVE FOR ORGANIZED SEVERE
STORMS...MLCAPES AOA 1000 J/KG AND HIGH DEWPOINT DEPRESSIONS AT
H7-H5 WITH MOIST LOW-LEVELS POINT TO POSSIBLE GUSTY WINDS WITH ANY
TSRA. ANY SHRA/TSRA WOULD WANE BY LATER EVENING WITH LOSS OF
HEATING/WEAKENING SFC-H85 CONVERGENCE. GFS AND LATEST GEM-NHEM AND
12Z ECMWF FOCUS H85 TROUGH MORE LATER TUESDAY NIGHT AND MORE SO ON
WEDNESDAY WITH ARRIVAL OF PRIMARY COLD FRONT. BASED ON TREND FROM
LATEST ECMWF...DECIDED TO NOT GO TOO HIGH FOR POPS ON TUESDAY.
AS LARGER FORMED UPPER LOW COMPLEX OVER MANITOBA RUMBLES EAST INTO
ONTARIO...EXPECT SHARP COLD FRONT TO SWEEP ACROSS GREAT LAKES REGION
WEDNESDAY AND THURSDAY. WOULD THINK THERE WOULD BE DECENT CHANCE FOR
RAIN WITH THE FROPA. BY TIME FRONT ARRIVES GFS AND GEM-NHEM SHOWS
SHARP H85 WIND SHIFT AND MOISTURE ADVECTION INTO THE AREA. OTHER
MODELS ALREADY SHOVE THE H85 TROUGH THROUGH SHUNTING MORE ABUNDANT
MOISTURE SOUTHEAST OF CWA...BUT AS MENTIONED BEFORE LATEST ECMWF HAS
TRENDED THIS WAY AS WELL. CONSISTENCY ON THESE SOLUTIONS NOT THE
GREATEST. THERE ARE ALSO HINTS THAT YET ANOTHER WEAKER WAVE/H7
MOISTURE MAY BE SLIDING THROUGH AREA WHILE FRONT SLIDES THROUGH.
DETAILS CERTAINLY STILL NEED TO BE SORTED OUT AS TO LOCATION AND
COVERAGE OF BEST RAIN CHANCES ON WEDNESDAY. CHANCE POPS FOR SCT
SHRA/TSRA COVER IT FINE FOR NOW. PRESSURE GRADIENT TIGHTENS
WEDNESDAY NIGHT AND THURSDAY IN WAKE OF THE COLD FRONT BUT OTHER
THAN FOR A BRIEF PERIOD WEDNESDAY EVENING WHERE GFS SHOWS 950-925MB
WINDS 30-35 KTS...H925-H85 WINDS INTO THURSDAY ARE ONLY AROUND 20
KTS. SO EVEN THOUGH STEADY COOLING ALOFT OCCURS INTO THURSDAY...THIS
SYSTEM DOES NOT LOOK TO PRODUCE VERY STRONG WINDS AS EARLY FALL
SYSTEMS SOMETIMES CAN DO. TWO ISSUES THAT WILL NEED TO BE MONITORED
THOUGH IN WAKE OF THE COLD FROPA WILL BE AN INCREASED RISK OF RIP
CURRENTS AND POSSIBLE UPPER LOW TYPE WATERSPOUTS LATER THURSDAY INTO
FRIDAY.
ALTHOUGH HIGH PRESSURE TRIES TO BUILD IN LATE THIS WEEK IT REMAINS
PRETTY WEAK AND DIFFUSE AS UPPER FLOW IS NOT CONFLUENT. BY FAR THE
STRONGER SURFACE FEATURE WILL BE WRAPPED UP SURFACE LOW VICINITY OF
HUDSON BAY AND JAMES BAY. BY LATER THURSDAY INTO FRIDAY CANNOT RULE
OUT AT LEAST LIGHT LK EFFECT SHRA SINCE H85 TEMPS DROP TO 4-6C
/WATER TEMPS STILL RUNNING 18-20C/ AND SINCE THERE COULD BE ANOTHER
WEAKER SHORTWAVE/ADDITIONAL MOISTURE PUSHING INTO WESTERN GREAT
LAKES PER GFS/ECMWF. NOT A BIG CHANCE AS LOW-LEVEL FLOW IS NOT
THAT FAVORABLE GIVEN NEUTRAL TO ANTICYCLONIC LOOK...BUT SOME LIGHT
PRECIP SEEMS POSSIBLE.
MODEL DIFFERENCES EMERGE BY NEXT WEEKEND WITH THE MAIN ISSUE ON HOW
QUICK THE 00Z GFS BRINGS ANOTHER LARGER SCALE TROUGH EAST ACROSS THE
NORTHERN PLAINS. 00Z ECMWF INDICATES RIDGING BUILDS IN ALOFT WITH A
SHARPER SURFACE RIDGE FROM THE PLAINS INTO FAR NORTHERN PORTION OF
UPPER GREAT LAKES. 06Z-12Z RUNS OF GFS HAVE TRENDED ECMWF WAY.
LATEST COUPLE RUNS OF ECMWF POINT TO UPPER LAKES BEING ON THE DRY
FRINGE OF SET OF DISTURBANCES WHICH WOULD BRING RAIN TO PORTIONS OF
GREAT LAKES TO START NEXT WEEKEND. HPC PREFERS TO SIDE WITH ECMWF
IDEA AND THIS FORECAST WILL TILT THAT WAY AS WELL WITH A GENERAL DRY
FCST NEXT WEEKEND. AFTER SLIGHTLY THAN NORMAL HIGH TEMPERATURES
FRIDAY AND SATURDAY...EXPECT SOME MODERATION IN TEMPERATURES BY NEXT
SUNDAY.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 121 AM EDT MON SEP 3 2012
ALTHOUGH A FEW -SHRA MAY ARRIVE AT KIWD/KCMX LATE TONIGHT AND AT
KSAW LATE MON MORNING AHEAD OF AN APPROACHING COLD FRONT...EXPECT
VFR CONDITIONS AS THE FRONTAL BOUNDARY MOVES THRU THE AREA TODAY AS
LOW-LEVEL DRY AIR HOLDS. THERE IS POTENTIAL FOR STRATUS/FOG TO
DEVELOP AT KSAW LATE MONDAY NIGHT AS MOIST SFC DEWPOINTS REMAIN AND
HIGH PRESSURE SETTLES OVER THE AREA. MODEST LOW-LEVEL JET AHEAD OF
COLD FRONT MAY RESULT IN LLWS AT KIWD/KCMX TONIGHT.
&&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 347 PM EDT SUN SEP 2 2012
TIGHTENING PRES GRADIENT BTWN HIGH PRES TO THE E AND AN APPROACHING
COLD FRONT TO THE W WILL RESULT IN SE TO S WINDS INCREASING TO
AROUND 20KT TONIGHT. SOUTHERLY WINDS MAY GUST TO AROUND 25KT AT
HIGHER OBS PLATFORMS...ESPECIALLY OVER CNTRL AND ERN PORTIONS OF THE
LAKE. PRES GRADIENT THEN SLACKENS WITH PASSING/WEAKENING COLD FRONT
MON...RESULTING IN WINDS DIMINISHING BACK TO UNDER 15KT MON INTO
TUE. NEXT COLD FRONT PASSING TUE NIGHT/WED WILL BRING AN INCREASE IN
W TO NW WINDS TO AROUND 20KT...MAYBE HIGHER...LATER WED INTO THU.
WINDS WILL DIMINISH SLIGHTLY FRI AS NEXT TROF PASSES EARLY IN THE
DAY.
&&
.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 HASTINGS NE
1231 PM CDT MON SEP 3 2012
.UPDATE...SENT AN UPDATE TO THE FORECAST TO INCREASE CLOUD COVER
THROUGH THE REMAINDER OF THE AFTERNOON HOURS AS LATEST SATELLITE
IMAGERY INDICATES A NICE BAND OF MID/UPPER LEVEL CLOUD
COVER...ASSOCIATED WITH WEAK FRONTAL BOUNDARY ACROSS THE AREA...
EXTENDS SOUTHWESTWARD ACROSS NORTHWESTERN KANSAS AND INTO
COLORADO. WITH THE INCREASED CLOUD COVER...A FEW LIGHT
SHOWERS/SPRINKLES AND AN ISOLATED EMBEDDED THUNDERSTORM...ALSO
TRENDED DOWN AFTERNOON FORECAST TEMPS A FEW DEGREES. NO OTHER
CHANGES NECESSARY TO INHERITED FORECAST AT THIS TIME.
.AVIATION...18Z KGRI TAF...PREVAILING VFR CONDITIONS WITH
GENERALLY LIGHT WINDS ARE EXPECTED TO PERSIST AT KGRI FOR THE
MAJORITY OF THE NEXT 24 HOURS...WITH AN ISOLATED SHOWER OR
THUNDERSTORM POSSIBLE...BUT NOT EXPECTED...THROUGH THE AFTERNOON
HOURS TODAY. AS A RESULT...KEPT BKN MID LEVEL CLOUD DECK WITH A
VCSH POSSIBLE NEAR THE TERMINAL THROUGH 04/00Z...WITH CLOUDS
SLOWLY SCATTERING THEREAFTER. SOME INDICATION THAT WITH LIGHT
WINDS...CLEARING SKIES AND ELEVATED DEW POINTS OVERNIGHT THAT WE
COULD SEE SOME PATCHY FOG DEVELOPMENT...BUT BELIEVE CLOUD COVER
OVERNIGHT WILL BE SUFFICIENT TO PREVENT MAXIMUM RADIATIVE COOLING
AND KEPT MENTION OF BR OUT 18Z TAF FOR THE TIME BEING.
&&
.PREV DISCUSSION... /ISSUED 345 AM CDT MON SEP 3 2012/
SHORT TERM...THROUGH 12Z THURSDAY. OVERNIGHT UPPER AIR ANALYSIS
INDICATES A LONG WAVE RIDGE OVER THE EASTERN CONUS AND A TROUGH
OVER THE WEST. SOUTHWESTERLY TO ZONAL MID AND UPPER LEVEL FLOW
EXISTS OVER THE MUCH OF THE CENTRAL CONUS AS A RESULT. MID AND
UPPER LEVEL JET ENERGY EXTENDS FROM SOUTHERN
CALIFORNIA...NORTHEAST INTO THE NORTHERN PLAINS AND PORTIONS OF
THE CENTRAL PLAINS...AS WELL AS SOUTHERN CANADA...AND THEN
SOUTHEAST INTO THE NORTHEASTERN CONUS. A ~90KT UPPER LEVEL JET
STREAK IS ALSO EVIDENT OVER THE CENTRAL AND NORTHERN ROCKY
MOUNTAIN RANGE. WATER VAPOR IMAGERY INDICATES INCREASED LEVELS OF
MID LEVEL MOISTURE EXTENDING NORTHWARD FROM MEXICO INTO THE
SOUTHWESTERN CONUS...AND THEN NORTHEAST INTO THE CENTRAL PLAINS.
AT THE SURFACE A WEAK COLD FRONT EXTENDS FROM NORTHEAST NEBRASKA
TO SOUTHWEST KANSAS. THE LOW LEVEL WIND FIELD REMAINS FROM THE
SOUTHEAST ACROSS SOUTHEASTERN PORTIONS OF THE OUR CWA...WITH MORE
OF A NORTHERLY LOW LEVEL WIND FIELD NOTED FARTHER NORTHWEST ACROSS
THE AREA BEHIND THE FRONT.
GUIDANCE FROM THE NAM AND OPERATIONAL GFS CONTINUE TO SUGGEST THE
UPPER LEVEL JET STREAK...CURRENTLY OVER THE CENTRAL AND NORTHERN
ROCKY MOUNTAIN RANGE...WILL CONTINUE MOVING EAST/NORTHEAST
TODAY...WITH THE RIGHT-REAR QUADRANT OF THIS JET STREAK SETTING UP
SHOP OVER NORTHERN PORTIONS OF OUR CWA. QPF FIELDS FROM THE
NAM...OPERATIONAL GFS AND SREF-MEAN...AS WELL AS SIMULATED
REFLECTIVITY FROM THE 4KM WRF-NMM AND HRRR ALL SUGGEST ENOUGH OF A
DIRECT THERMAL CIRCULATION AND RESULTANT FRONTOGENESIS WILL BE
PRESENT FOR ISOLATED TO SCATTERED PRECIPITATION PRODUCTION OVER
NORTHERN PORTIONS OF OUR AREA THROUGH 18Z. THESE MODEL SOLUTIONS
HAVE BEEN FAIRLY CONSISTENCE SETS OF GUIDANCE THROUGH THE PAST
THREE DAYS AND AS A RESULT WILL GO AHEAD AND MAINTAIN 20%-30% POPS
MAINLY ACROSS NORTHERN PORTIONS OF OUR CWA THROUGH 18Z. GUIDANCE
SUGGESTS THE UPPER LEVEL JET STREAK WILL WEAKEN AND PUSH
EAST/NORTHEAST OF OUR AREA BY THIS AFTERNOON...WHICH WOULD
OTHERWISE BRING AND END TO THE PRECIPITATION CHANCES ACROSS OUR
AREA. THAT BEING SAID...THERE REMAIN INDICATIONS FROM THE NAM AND
OPERATIONAL GFS OF MULTIPLE SMALL SCALE MID LEVEL PERTURBATIONS
PUSHING NEAR OR OVER THE AREA THROUGH THIS AFTERNOON AND EVENING.
GIVEN THE WEAK FORCING AND DIFFICULTY IN ASSIGNING PRECIPITATION
CHANCES TO AN AREA GIVEN THE SUBTLE NATURE OF THESE SMALL SCALE
PERTURBATIONS...QPF FIELDS FROM THE NAM...OPERATIONAL
GFS...EC...AND SREF-MEAN ARE ALL OVER THE PLACE AND OFFER LITTLE
IN THE WAY OF HELP IN TRYING TO DETERMINE WHERE AFTERNOON
CONVECTION WILL MOST LIKELY BE REALIZED. YESTERDAY AT THIS TIME IT
WAS BELIEVED THE WEAK LOW LEVEL BAROCLINIC ZONE...CURRENTLY OVER
OUR AREA...WOULD SLOWLY DRIFT TO THE SOUTHEAST AND WOULD PROVIDE
ADDITIONAL LOW LEVEL CONVERGENCE FOR SURFACE-BASED CONVECTION
DURING THE AFTERNOON AND EARLY EVENING HOURS. HOWEVER NOW IT
APPEARS THIS BAROCLINIC ZONE WILL QUICKLY EXIT OUR AREA TO THE
SOUTHEAST BY EARLY AFTERNOON AND WILL OFFER LITTLE IN THE WAY OF
ADDITIONAL FORCING FOR CONVECTIVE INITIATION. LONG STORY
SHORT...CONFIDENCE IS VERY LOW REGARDING MEASURABLE PRECIPITATION
BEING REALIZED AT ANY ONE LOCATION ACROSS THE CWA THIS AFTERNOON
AND EVENING. BUT BECAUSE MOST ALL MODELS SUGGEST AT LEAST SOME
ISOLATED CONVECTIVE ACTIVITY WILL BE OBSERVED...AGAIN NO TELLING
WHERE FOR SURE...WILL GO AHEAD AND CARRY 20% POPS ACROSS THE
ENTIRE CWA 18Z MONDAY THROUGH 06Z TUESDAY. AS FOR SEVERE WEATHER
CHANCES THIS AFTERNOON AND EVENING...WILL CONTINUE TO DISREGARD
THE OPERATIONAL GFS WHICH SUGGESTS SURFACE DEW POINTS IN THE MID
70S WILL BE REALIZED ACROSS PORTIONS OF THE CWA THIS AFTERNOON.
BOIVERIFY SUGGESTS BCCONSALL CONTINUES TO BE A GOOD PERFORMER WITH
RESPECT TO SURFACE DEW POINTS ACROSS OUR AREA AND THIS SET OF
GUIDANCE SUGGESTS AFTERNOON DEW POINTS WILL REMAIN GENERALLY IN
THE LOW TO MID 60S ACROSS OUR AREA...WITH PERHAPS A FEW UPPER 60
READINGS ACROSS OUR EAST...WHICH IS ALSO WHAT THE NAM CONTINUES TO
SUGGEST. FOLLOWING CLOSER TO THE NAM WOULD ALSO SUGGEST 0-1KM
MLCAPE VALUES OF ~1000J/KG WILL BE IN PLACE ACROSS THE AREA THIS
AFTERNOON AND EVENING. NOT THAT THESE POTENTIAL INSTABILITY VALUES
ARE SOMETHING TO GET OVERLY EXCITED ABOUT BUT WITH THE UPPER LEVEL
JET AXIS OVER THE AREA...DEEP LAYER BULK SHEAR VALUES ON THE ORDER
OF 40KTS WILL ALSO LIKELY BE PRESENT. ALTHOUGH INITIAL UPDRAFT
STRENGTH WILL LIKELY BE MARGINAL AT BEST FOR LARGE HAIL
PRODUCTION...THE ROTATIONAL POTENTIAL OF SAID UPDRAFT MAY ENHANCE
IT ENOUGH FOR A BETTER HAIL THREAT. GIVEN ALL THIS...IT STILL
SEEMS POSSIBLE THAT UPDRAFT STRENGTH COULD BE STRONG ENOUGH TO
SUPPORT LARGE HAIL AND AS A RESULT...WILL GO AHEAD AND CONTINUE TO
OUTLOOK THE AREA FOR POSSIBLE SEVERE WEATHER THIS AFTERNOON AND
EVENING. LOSS OF DIABATIC HEATING POST-SUNSET SHOULD KILL ANY
CONVECTION BEYOND 03Z THIS EVENING...WITH AN OVERALL LACK IN
KINEMATIC FORCING LIKELY PROVIDING DRY CONDITIONS TO THE AREA 03Z-
18Z TUESDAY.
GUIDANCE FROM THE NAM...OPERATIONAL GFS...AND EC ALL SUGGEST A
MORE SIGNIFICANT MID LEVEL SHORT WAVE WILL PUSH INTO SOUTH CENTRAL
CANADA AND PORTIONS OF THE NORTH CENTRAL CONUS TUESDAY INTO
TUESDAY NIGHT. A RESULTANT AREA OF SURFACE LOW PRESSURE IS
EXPECTED TO PUSH ACROSS THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY DURING THE SAME TIME PERIOD...WITH AN ASSOCIATED SURFACE
COLD FRONT EXPECTED TO SWEEP ACROSS NEBRASKA. AT THIS TIME THE LOW
LEVEL BAROCLINIC ZONE IS EXPECTED TO NEAR NORTH/NORTHWESTERN
PORTIONS OF OUR CWA BY 00Z WEDNESDAY...LIKELY CLEARING THE ENTIRE
CWA BY 12Z WEDNESDAY. SURFACE-BASED CONVECTION WILL BE POSSIBLE IN
THE VICINITY OF THIS LOW LEVEL BAROCLINIC ZONE ACROSS OUR
NORTH/NORTHWEST BY LATE AFTERNOON TUESDAY...WITH ADDITIONAL
CONVECTIVE ACTIVITY PERHAPS SPREADING SOUTHEAST ACROSS THE CWA
HEADING INTO THE EVENING AND OVERNIGHT HOURS TUESDAY. GIVEN ALL
THIS...WILL GO AHEAD WITH 20%-30% POPS ACROSS THE CWA 21Z TUESDAY
THROUGH 12Z WEDNESDAY. POOLING OF LOW LEVEL MOISTURE AHEAD OF THE
LOW LEVEL BAROCLINIC ZONE...AS SUGGESTED BY THE NAM...MAY ACTUALLY
HELP TO INCREASE POTENTIAL INSTABILITY ACROSS OUR AREA WHEN
COMPARED TO MONDAY...WITH THE NAM SUGGESTING 0-1KM MLCAPE VALUES
ON THE ORDER OF 1500J/KG POSSIBLE TUESDAY AFTERNOON INTO THE
EVENING HOURS. IN ADDITION...DEEP LAYER BULK SHEAR VALUES OF
AROUND 35KTS WILL ALSO BE IN EXISTENCE. GIVEN ALL THIS...WILL
CONTINUE THE SEVERE WEATHER MENTION IN THE HWO FOR TUESDAY.
A COOLER AND DRIER AIRMASS WILL SETTLE IN ACROSS THE AREA BEHIND
THE LOW LEVEL BAROCLINIC ZONE WEDNESDAY AND WEDNESDAY NIGHT...AND
AN OVERALL LACK IN KINEMATIC FORCING SHOULD PRESENT DRY CONDITIONS
TO OUR AREA 12Z WEDNESDAY THROUGH 12Z THURSDAY.
AN EASTERLY COMPONENT TO THE LOW LEVEL WIND FIELD AND A SLIGHTLY
COOLER AIRMASS WILL PRESENT COOLER CONDITIONS TO THE AREA TODAY
WHEN COMPARED TO SUNDAY...WITH AFTERNOON HIGHS IN THE LOW TO MID
90S EXPECTED THROUGH MOST LOCATIONS. WARMER WEATHER AHEAD OF THE
APPROACHING LOW LEVEL BAROCLINIC ZONE WILL LIKELY PRESENT
AFTERNOON HIGHS IN THE MID TO UPPER 90S ON TUESDAY. THE COOLER
AIRMASS ON WEDNESDAY WILL LIKELY KEEP AFTERNOON HIGHS IN THE 80S
TO FINISH OUT THE SHORT TERM FORECAST PERIOD. OVERNIGHT LOWS IN
THE 60S WILL REMAIN THE NORM MONDAY NIGHT AND TUESDAY NIGHT...WITH
THE COOLER AIRMASS LIKELY PROMOTING TEMPERATURES IN THE 50S
WEDNESDAY NIGHT INTO THURSDAY MORNING.
LONG TERM...THURSDAY THROUGH SUNDAY. PRIMARY FORECAST CONCERNS
LIE WITH END OF THE WEEK PRECIPITATION CHANCES...AND TEMPERATURES.
THE START OF THE LONG TERM PERIOD SHOWS MODELS NOT IN TOO BAD OF
AGREEMENT WITH THE PATTERN ACROSS THE CONUS...WHICH REMAINS
ZONAL...SET UP BETWEEN BROAD HIGH PRESSURE EXTENDING ACROSS THE
DESERT SW AND SRN PLAINS...WHILE A LARGE LOW PRESSURE SYSTEM SPINS
OVER CENTRAL CANADA. THROUGH THE END OF THE WORK
WEEK...PRECIPITATION CHANCES CONTINUE ACROSS THE CWA...DRIVEN BY A
COUPLE OF DISTURBANCES ASSOCIATED WITH THAT CANADIAN LOW PRESSURE
SYSTEM. THE FIRST ONE LOOKS TO AFFECT THE AREA MAINLY ON
THURSDAY/THURSDAY NIGHT...ALSO PUSHING A SURFACE BOUNDARY INTO
ROUGHLY THE NORTHERN HALF OF THE CWA DURING THE AFTERNOON HOURS.
THE SECOND DISTURBANCE...DIVING BASICALLY STRAIGHT SOUTH OUT OF
CANADA...AFFECTS THE AREA MAINLY FRIDAY/FRIDAY EVENING. KEPT POPS
CWA-WIDE THURS/THURS NIGHT/FRI...WITH ONLY A FEW LINGERING POPS
INTO FRIDAY NIGHT ACROSS NC KS...AND IF CURRENT MODEL TRENDS
CONTINUES...THOSE FRIDAY EVENING/NIGHT POPS COULD BE REMOVED. AS
MENTIONED...THURSDAY SEE THE INITIAL FRONT MOVE INTO THE CWA...BUT
THAT SECOND DISTURBANCE WILL USHER IN A REINFORCING COLD
FRONT...ACCOMPANIED BY THE COOLER/DRIER AIR FOR FRIDAY. FORECAST
HIGHS FOR THURSDAY SIT IN THE 80S...WHILE FRIDAY IS IN THE MID
70S/LOWER 80S. WILL KEEP THE MENTION OF SOME STRONG/SEVERE
THUNDERSTORMS GOING FOR THIS PERIOD WITH MODELS CONTINUING TO SHOW
THE POTENTIAL FOR DECENT INSTABILITY/SHEAR IN THE AREA.
PLEASANT CONDITIONS ON TAP FOR THE UPCOMING WEEKEND...WITH MODELS
DEPICT DRIER NORTHWESTERLY FLOW SETTING UP IN THE UPPER LEVELS
ACROSS THE CENTRAL PLAINS...SITTING BETWEEN THE TROUGH/LOW OVER
THE GREAT LAKES AND MIDWEST...WHILE RIDGING BUILDS INTO THE
ROCKIES. HIGH PRESSURE LOOKS TO BE THE PRIMARY PLAYER AT THE
SURFACE...BUILDING IN FROM THE NORTHWEST BEHIND THE END OF THE
WORK WEEK FRONTAL PASSAGE. EXPECTING TO SEE PLENTY OF
SUNSHINE...WITH FAIRLY LIGHT WINDS /ESP ON SAT/. THE AREA OF SFC
HIGH PRESSURE LOOKS TO BE CENTERED RIGHT OVER THE CWA ON
SATURDAY...BEFORE SLIDING OFF SLIGHTLY TO THE EAST ON SUNDAY...AND
EXPECTING SATURDAY TO BE A TOUCH COOLER THAN SUNDAY. CURRENT
FORECAST HIGHS ON SATURDAY SIT IN THE MID 70S...WITH SUNDAY
CREEPING UP INTO THE UPPER 70S TO LOWER 80S...BOTH DAYS FEELING
PRETTY NICE WITH DEWPOINTS LOOKING TO BE IN THE 40S FOR MOST
LOCATIONS.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
AVIATION/UPDATE...ROSSI
SHORT TERM...BRYANT
LONG TERM...ADO
AREA FORECAST DISCUSSION
NWS HASTINGS NE
622 AM CDT MON SEP 3 2012
.AVIATION...12Z TAF. VFR CONDITIONS FORECAST FOR THIS TAF
PERIOD...THOUGH THE TERMINAL COULD SEE A FEW SHOWERS PASS THROUGH
THIS MORNING. OUTSIDE OF THIS MORNING...THERE ARE OTHER CHANCES
FOR PRECIPITATION IN THE AREA...BUT NOT CONFIDENT ENOUGH IN
ANYTHING AFFECTING THE TERMINAL TO PUT IN ANY MENTION. VARIABLE
WINDS LOOK TO CONTINUE THIS MORNING...BEFORE TURNING MORE TO THE
SOUTHEAST THIS AFTERNOON. SPEEDS EXPECTED TO BE ON THE LIGHT SIDE.
&&
.PREV DISCUSSION... /ISSUED 345 AM CDT MON SEP 3 2012/
SHORT TERM...THROUGH 12Z THURSDAY. OVERNIGHT UPPER AIR ANALYSIS
INDICATES A LONG WAVE RIDGE OVER THE EASTERN CONUS AND A TROUGH
OVER THE WEST. SOUTHWESTERLY TO ZONAL MID AND UPPER LEVEL FLOW
EXISTS OVER THE MUCH OF THE CENTRAL CONUS AS A RESULT. MID AND
UPPER LEVEL JET ENERGY EXTENDS FROM SOUTHERN
CALIFORNIA...NORTHEAST INTO THE NORTHERN PLAINS AND PORTIONS OF
THE CENTRAL PLAINS...AS WELL AS SOUTHERN CANADA...AND THEN
SOUTHEAST INTO THE NORTHEASTERN CONUS. A ~90KT UPPER LEVEL JET
STREAK IS ALSO EVIDENT OVER THE CENTRAL AND NORTHERN ROCKY
MOUNTAIN RANGE. WATER VAPOR IMAGERY INDICATES INCREASED LEVELS OF
MID LEVEL MOISTURE EXTENDING NORTHWARD FROM MEXICO INTO THE
SOUTHWESTERN CONUS...AND THEN NORTHEAST INTO THE CENTRAL PLAINS.
AT THE SURFACE A WEAK COLD FRONT EXTENDS FROM NORTHEAST NEBRASKA
TO SOUTHWEST KANSAS. THE LOW LEVEL WIND FIELD REMAINS FROM THE
SOUTHEAST ACROSS SOUTHEASTERN PORTIONS OF THE OUR CWA...WITH MORE
OF A NORTHERLY LOW LEVEL WIND FIELD NOTED FARTHER NORTHWEST ACROSS
THE AREA BEHIND THE FRONT.
GUIDANCE FROM THE NAM AND OPERATIONAL GFS CONTINUE TO SUGGEST THE
UPPER LEVEL JET STREAK...CURRENTLY OVER THE CENTRAL AND NORTHERN
ROCKY MOUNTAIN RANGE...WILL CONTINUE MOVING EAST/NORTHEAST
TODAY...WITH THE RIGHT-REAR QUADRANT OF THIS JET STREAK SETTING UP
SHOP OVER NORTHERN PORTIONS OF OUR CWA. QPF FIELDS FROM THE
NAM...OPERATIONAL GFS AND SREF-MEAN...AS WELL AS SIMULATED
REFLECTIVITY FROM THE 4KM WRF-NMM AND HRRR ALL SUGGEST ENOUGH OF A
DIRECT THERMAL CIRCULATION AND RESULTANT FRONTOGENESIS WILL BE
PRESENT FOR ISOLATED TO SCATTERED PRECIPITATION PRODUCTION OVER
NORTHERN PORTIONS OF OUR AREA THROUGH 18Z. THESE MODEL SOLUTIONS
HAVE BEEN FAIRLY CONSISTENCE SETS OF GUIDANCE THROUGH THE PAST
THREE DAYS AND AS A RESULT WILL GO AHEAD AND MAINTAIN 20%-30% POPS
MAINLY ACROSS NORTHERN PORTIONS OF OUR CWA THROUGH 18Z. GUIDANCE
SUGGESTS THE UPPER LEVEL JET STREAK WILL WEAKEN AND PUSH
EAST/NORTHEAST OF OUR AREA BY THIS AFTERNOON...WHICH WOULD
OTHERWISE BRING AND END TO THE PRECIPITATION CHANCES ACROSS OUR
AREA. THAT BEING SAID...THERE REMAIN INDICATIONS FROM THE NAM AND
OPERATIONAL GFS OF MULTIPLE SMALL SCALE MID LEVEL PERTURBATIONS
PUSHING NEAR OR OVER THE AREA THROUGH THIS AFTERNOON AND EVENING.
GIVEN THE WEAK FORCING AND DIFFICULTY IN ASSIGNING PRECIPITATION
CHANCES TO AN AREA GIVEN THE SUBTLE NATURE OF THESE SMALL SCALE
PERTURBATIONS...QPF FIELDS FROM THE NAM...OPERATIONAL
GFS...EC...AND SREF-MEAN ARE ALL OVER THE PLACE AND OFFER LITTLE
IN THE WAY OF HELP IN TRYING TO DETERMINE WHERE AFTERNOON
CONVECTION WILL MOST LIKELY BE REALIZED. YESTERDAY AT THIS TIME IT
WAS BELIEVED THE WEAK LOW LEVEL BAROCLINIC ZONE...CURRENTLY OVER
OUR AREA...WOULD SLOWLY DRIFT TO THE SOUTHEAST AND WOULD PROVIDE
ADDITIONAL LOW LEVEL CONVERGENCE FOR SURFACE-BASED CONVECTION
DURING THE AFTERNOON AND EARLY EVENING HOURS. HOWEVER NOW IT
APPEARS THIS BAROCLINIC ZONE WILL QUICKLY EXIT OUR AREA TO THE
SOUTHEAST BY EARLY AFTERNOON AND WILL OFFER LITTLE IN THE WAY OF
ADDITIONAL FORCING FOR CONVECTIVE INITIATION. LONG STORY
SHORT...CONFIDENCE IS VERY LOW REGARDING MEASURABLE PRECIPITATION
BEING REALIZED AT ANY ONE LOCATION ACROSS THE CWA THIS AFTERNOON
AND EVENING. BUT BECAUSE MOST ALL MODELS SUGGEST AT LEAST SOME
ISOLATED CONVECTIVE ACTIVITY WILL BE OBSERVED...AGAIN NO TELLING
WHERE FOR SURE...WILL GO AHEAD AND CARRY 20% POPS ACROSS THE
ENTIRE CWA 18Z MONDAY THROUGH 06Z TUESDAY. AS FOR SEVERE WEATHER
CHANCES THIS AFTERNOON AND EVENING...WILL CONTINUE TO DISREGARD
THE OPERATIONAL GFS WHICH SUGGESTS SURFACE DEW POINTS IN THE MID
70S WILL BE REALIZED ACROSS PORTIONS OF THE CWA THIS AFTERNOON.
BOIVERIFY SUGGESTS BCCONSALL CONTINUES TO BE A GOOD PERFORMER WITH
RESPECT TO SURFACE DEW POINTS ACROSS OUR AREA AND THIS SET OF
GUIDANCE SUGGESTS AFTERNOON DEW POINTS WILL REMAIN GENERALLY IN
THE LOW TO MID 60S ACROSS OUR AREA...WITH PERHAPS A FEW UPPER 60
READINGS ACROSS OUR EAST...WHICH IS ALSO WHAT THE NAM CONTINUES TO
SUGGEST. FOLLOWING CLOSER TO THE NAM WOULD ALSO SUGGEST 0-1KM
MLCAPE VALUES OF ~1000J/KG WILL BE IN PLACE ACROSS THE AREA THIS
AFTERNOON AND EVENING. NOT THAT THESE POTENTIAL INSTABILITY VALUES
ARE SOMETHING TO GET OVERLY EXCITED ABOUT BUT WITH THE UPPER LEVEL
JET AXIS OVER THE AREA...DEEP LAYER BULK SHEAR VALUES ON THE ORDER
OF 40KTS WILL ALSO LIKELY BE PRESENT. ALTHOUGH INITIAL UPDRAFT
STRENGTH WILL LIKELY BE MARGINAL AT BEST FOR LARGE HAIL
PRODUCTION...THE ROTATIONAL POTENTIAL OF SAID UPDRAFT MAY ENHANCE
IT ENOUGH FOR A BETTER HAIL THREAT. GIVEN ALL THIS...IT STILL
SEEMS POSSIBLE THAT UPDRAFT STRENGTH COULD BE STRONG ENOUGH TO
SUPPORT LARGE HAIL AND AS A RESULT...WILL GO AHEAD AND CONTINUE TO
OUTLOOK THE AREA FOR POSSIBLE SEVERE WEATHER THIS AFTERNOON AND
EVENING. LOSS OF DIABATIC HEATING POST-SUNSET SHOULD KILL ANY
CONVECTION BEYOND 03Z THIS EVENING...WITH AN OVERALL LACK IN
KINEMATIC FORCING LIKELY PROVIDING DRY CONDITIONS TO THE AREA 03Z-
18Z TUESDAY.
GUIDANCE FROM THE NAM...OPERATIONAL GFS...AND EC ALL SUGGEST A
MORE SIGNIFICANT MID LEVEL SHORT WAVE WILL PUSH INTO SOUTH CENTRAL
CANADA AND PORTIONS OF THE NORTH CENTRAL CONUS TUESDAY INTO
TUESDAY NIGHT. A RESULTANT AREA OF SURFACE LOW PRESSURE IS
EXPECTED TO PUSH ACROSS THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY DURING THE SAME TIME PERIOD...WITH AN ASSOCIATED SURFACE
COLD FRONT EXPECTED TO SWEEP ACROSS NEBRASKA. AT THIS TIME THE LOW
LEVEL BAROCLINIC ZONE IS EXPECTED TO NEAR NORTH/NORTHWESTERN
PORTIONS OF OUR CWA BY 00Z WEDNESDAY...LIKELY CLEARING THE ENTIRE
CWA BY 12Z WEDNESDAY. SURFACE-BASED CONVECTION WILL BE POSSIBLE IN
THE VICINITY OF THIS LOW LEVEL BAROCLINIC ZONE ACROSS OUR
NORTH/NORTHWEST BY LATE AFTERNOON TUESDAY...WITH ADDITIONAL
CONVECTIVE ACTIVITY PERHAPS SPREADING SOUTHEAST ACROSS THE CWA
HEADING INTO THE EVENING AND OVERNIGHT HOURS TUESDAY. GIVEN ALL
THIS...WILL GO AHEAD WITH 20%-30% POPS ACROSS THE CWA 21Z TUESDAY
THROUGH 12Z WEDNESDAY. POOLING OF LOW LEVEL MOISTURE AHEAD OF THE
LOW LEVEL BAROCLINIC ZONE...AS SUGGESTED BY THE NAM...MAY ACTUALLY
HELP TO INCREASE POTENTIAL INSTABILITY ACROSS OUR AREA WHEN
COMPARED TO MONDAY...WITH THE NAM SUGGESTING 0-1KM MLCAPE VALUES
ON THE ORDER OF 1500J/KG POSSIBLE TUESDAY AFTERNOON INTO THE
EVENING HOURS. IN ADDITION...DEEP LAYER BULK SHEAR VALUES OF
AROUND 35KTS WILL ALSO BE IN EXISTENCE. GIVEN ALL THIS...WILL
CONTINUE THE SEVERE WEATHER MENTION IN THE HWO FOR TUESDAY.
A COOLER AND DRIER AIRMASS WILL SETTLE IN ACROSS THE AREA BEHIND
THE LOW LEVEL BAROCLINIC ZONE WEDNESDAY AND WEDNESDAY NIGHT...AND
AN OVERALL LACK IN KINEMATIC FORCING SHOULD PRESENT DRY CONDITIONS
TO OUR AREA 12Z WEDNESDAY THROUGH 12Z THURSDAY.
AN EASTERLY COMPONENT TO THE LOW LEVEL WIND FIELD AND A SLIGHTLY
COOLER AIRMASS WILL PRESENT COOLER CONDITIONS TO THE AREA TODAY
WHEN COMPARED TO SUNDAY...WITH AFTERNOON HIGHS IN THE LOW TO MID
90S EXPECTED THROUGH MOST LOCATIONS. WARMER WEATHER AHEAD OF THE
APPROACHING LOW LEVEL BAROCLINIC ZONE WILL LIKELY PRESENT
AFTERNOON HIGHS IN THE MID TO UPPER 90S ON TUESDAY. THE COOLER
AIRMASS ON WEDNESDAY WILL LIKELY KEEP AFTERNOON HIGHS IN THE 80S
TO FINISH OUT THE SHORT TERM FORECAST PERIOD. OVERNIGHT LOWS IN
THE 60S WILL REMAIN THE NORM MONDAY NIGHT AND TUESDAY NIGHT...WITH
THE COOLER AIRMASS LIKELY PROMOTING TEMPERATURES IN THE 50S
WEDNESDAY NIGHT INTO THURSDAY MORNING.
LONG TERM...THURSDAY THROUGH SUNDAY. PRIMARY FORECAST CONCERNS
LIE WITH END OF THE WEEK PRECIPITATION CHANCES...AND TEMPERATURES.
THE START OF THE LONG TERM PERIOD SHOWS MODELS NOT IN TOO BAD OF
AGREEMENT WITH THE PATTERN ACROSS THE CONUS...WHICH REMAINS
ZONAL...SET UP BETWEEN BROAD HIGH PRESSURE EXTENDING ACROSS THE
DESERT SW AND SRN PLAINS...WHILE A LARGE LOW PRESSURE SYSTEM SPINS
OVER CENTRAL CANADA. THROUGH THE END OF THE WORK
WEEK...PRECIPITATION CHANCES CONTINUE ACROSS THE CWA...DRIVEN BY A
COUPLE OF DISTURBANCES ASSOCIATED WITH THAT CANADIAN LOW PRESSURE
SYSTEM. THE FIRST ONE LOOKS TO AFFECT THE AREA MAINLY ON
THURSDAY/THURSDAY NIGHT...ALSO PUSHING A SURFACE BOUNDARY INTO
ROUGHLY THE NORTHERN HALF OF THE CWA DURING THE AFTERNOON HOURS.
THE SECOND DISTURBANCE...DIVING BASICALLY STRAIGHT SOUTH OUT OF
CANADA...AFFECTS THE AREA MAINLY FRIDAY/FRIDAY EVENING. KEPT POPS
CWA-WIDE THURS/THURS NIGHT/FRI...WITH ONLY A FEW LINGERING POPS
INTO FRIDAY NIGHT ACROSS NC KS...AND IF CURRENT MODEL TRENDS
CONTINUES...THOSE FRIDAY EVENING/NIGHT POPS COULD BE REMOVED. AS
MENTIONED...THURSDAY SEE THE INITIAL FRONT MOVE INTO THE CWA...BUT
THAT SECOND DISTURBANCE WILL USHER IN A REINFORCING COLD
FRONT...ACCOMPANIED BY THE COOLER/DRIER AIR FOR FRIDAY. FORECAST
HIGHS FOR THURSDAY SIT IN THE 80S...WHILE FRIDAY IS IN THE MID
70S/LOWER 80S. WILL KEEP THE MENTION OF SOME STRONG/SEVERE
THUNDERSTORMS GOING FOR THIS PERIOD WITH MODELS CONTINUING TO SHOW
THE POTENTIAL FOR DECENT INSTABILITY/SHEAR IN THE AREA.
PLEASANT CONDITIONS ON TAP FOR THE UPCOMING WEEKEND...WITH MODELS
DEPICT DRIER NORTHWESTERLY FLOW SETTING UP IN THE UPPER LEVELS
ACROSS THE CENTRAL PLAINS...SITTING BETWEEN THE TROUGH/LOW OVER
THE GREAT LAKES AND MIDWEST...WHILE RIDGING BUILDS INTO THE
ROCKIES. HIGH PRESSURE LOOKS TO BE THE PRIMARY PLAYER AT THE
SURFACE...BUILDING IN FROM THE NORTHWEST BEHIND THE END OF THE
WORK WEEK FRONTAL PASSAGE. EXPECTING TO SEE PLENTY OF
SUNSHINE...WITH FAIRLY LIGHT WINDS /ESP ON SAT/. THE AREA OF SFC
HIGH PRESSURE LOOKS TO BE CENTERED RIGHT OVER THE CWA ON
SATURDAY...BEFORE SLIDING OFF SLIGHTLY TO THE EAST ON SUNDAY...AND
EXPECTING SATURDAY TO BE A TOUCH COOLER THAN SUNDAY. CURRENT
FORECAST HIGHS ON SATURDAY SIT IN THE MID 70S...WITH SUNDAY
CREEPING UP INTO THE UPPER 70S TO LOWER 80S...BOTH DAYS FEELING
PRETTY NICE WITH DEWPOINTS LOOKING TO BE IN THE 40S FOR MOST
LOCATIONS.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS HASTINGS NE
345 AM CDT MON SEP 3 2012
.SHORT TERM...THROUGH 12Z THURSDAY. OVERNIGHT UPPER AIR ANALYSIS
INDICATES A LONG WAVE RIDGE OVER THE EASTERN CONUS AND A TROUGH
OVER THE WEST. SOUTHWESTERLY TO ZONAL MID AND UPPER LEVEL FLOW
EXISTS OVER THE MUCH OF THE CENTRAL CONUS AS A RESULT. MID AND
UPPER LEVEL JET ENERGY EXTENDS FROM SOUTHERN
CALIFORNIA...NORTHEAST INTO THE NORTHERN PLAINS AND PORTIONS OF
THE CENTRAL PLAINS...AS WELL AS SOUTHERN CANADA...AND THEN
SOUTHEAST INTO THE NORTHEASTERN CONUS. A ~90KT UPPER LEVEL JET
STREAK IS ALSO EVIDENT OVER THE CENTRAL AND NORTHERN ROCKY
MOUNTAIN RANGE. WATER VAPOR IMAGERY INDICATES INCREASED LEVELS OF
MID LEVEL MOISTURE EXTENDING NORTHWARD FROM MEXICO INTO THE
SOUTHWESTERN CONUS...AND THEN NORTHEAST INTO THE CENTRAL PLAINS.
AT THE SURFACE A WEAK COLD FRONT EXTENDS FROM NORTHEAST NEBRASKA
TO SOUTHWEST KANSAS. THE LOW LEVEL WIND FIELD REMAINS FROM THE
SOUTHEAST ACROSS SOUTHEASTERN PORTIONS OF THE OUR CWA...WITH MORE
OF A NORTHERLY LOW LEVEL WIND FIELD NOTED FARTHER NORTHWEST ACROSS
THE AREA BEHIND THE FRONT.
GUIDANCE FROM THE NAM AND OPERATIONAL GFS CONTINUE TO SUGGEST THE
UPPER LEVEL JET STREAK...CURRENTLY OVER THE CENTRAL AND NORTHERN
ROCKY MOUNTAIN RANGE...WILL CONTINUE MOVING EAST/NORTHEAST
TODAY...WITH THE RIGHT-REAR QUADRANT OF THIS JET STREAK SETTING UP
SHOP OVER NORTHERN PORTIONS OF OUR CWA. QPF FIELDS FROM THE
NAM...OPERATIONAL GFS AND SREF-MEAN...AS WELL AS SIMULATED
REFLECTIVITY FROM THE 4KM WRF-NMM AND HRRR ALL SUGGEST ENOUGH OF A
DIRECT THERMAL CIRCULATION AND RESULTANT FRONTOGENESIS WILL BE
PRESENT FOR ISOLATED TO SCATTERED PRECIPITATION PRODUCTION OVER
NORTHERN PORTIONS OF OUR AREA THROUGH 18Z. THESE MODEL SOLUTIONS
HAVE BEEN FAIRLY CONSISTENCE SETS OF GUIDANCE THROUGH THE PAST
THREE DAYS AND AS A RESULT WILL GO AHEAD AND MAINTAIN 20%-30% POPS
MAINLY ACROSS NORTHERN PORTIONS OF OUR CWA THROUGH 18Z. GUIDANCE
SUGGESTS THE UPPER LEVEL JET STREAK WILL WEAKEN AND PUSH
EAST/NORTHEAST OF OUR AREA BY THIS AFTERNOON...WHICH WOULD
OTHERWISE BRING AND END TO THE PRECIPITATION CHANCES ACROSS OUR
AREA. THAT BEING SAID...THERE REMAIN INDICATIONS FROM THE NAM AND
OPERATIONAL GFS OF MULTIPLE SMALL SCALE MID LEVEL PERTURBATIONS
PUSHING NEAR OR OVER THE AREA THROUGH THIS AFTERNOON AND EVENING.
GIVEN THE WEAK FORCING AND DIFFICULTY IN ASSIGNING PRECIPITATION
CHANCES TO AN AREA GIVEN THE SUBTLE NATURE OF THESE SMALL SCALE
PERTURBATIONS...QPF FIELDS FROM THE NAM...OPERATIONAL
GFS...EC...AND SREF-MEAN ARE ALL OVER THE PLACE AND OFFER LITTLE
IN THE WAY OF HELP IN TRYING TO DETERMINE WHERE AFTERNOON
CONVECTION WILL MOST LIKELY BE REALIZED. YESTERDAY AT THIS TIME IT
WAS BELIEVED THE WEAK LOW LEVEL BAROCLINIC ZONE...CURRENTLY OVER
OUR AREA...WOULD SLOWLY DRIFT TO THE SOUTHEAST AND WOULD PROVIDE
ADDITIONAL LOW LEVEL CONVERGENCE FOR SURFACE-BASED CONVECTION
DURING THE AFTERNOON AND EARLY EVENING HOURS. HOWEVER NOW IT
APPEARS THIS BAROCLINIC ZONE WILL QUICKLY EXIT OUR AREA TO THE
SOUTHEAST BY EARLY AFTERNOON AND WILL OFFER LITTLE IN THE WAY OF
ADDITIONAL FORCING FOR CONVECTIVE INITIATION. LONG STORY
SHORT...CONFIDENCE IS VERY LOW REGARDING MEASURABLE PRECIPITATION
BEING REALIZED AT ANY ONE LOCATION ACROSS THE CWA THIS AFTERNOON
AND EVENING. BUT BECAUSE MOST ALL MODELS SUGGEST AT LEAST SOME
ISOLATED CONVECTIVE ACTIVITY WILL BE OBSERVED...AGAIN NO TELLING
WHERE FOR SURE...WILL GO AHEAD AND CARRY 20% POPS ACROSS THE
ENTIRE CWA 18Z MONDAY THROUGH 06Z TUESDAY. AS FOR SEVERE WEATHER
CHANCES THIS AFTERNOON AND EVENING...WILL CONTINUE TO DISREGARD
THE OPERATIONAL GFS WHICH SUGGESTS SURFACE DEW POINTS IN THE MID
70S WILL BE REALIZED ACROSS PORTIONS OF THE CWA THIS AFTERNOON.
BOIVERIFY SUGGESTS BCCONSALL CONTINUES TO BE A GOOD PERFORMER WITH
RESPECT TO SURFACE DEW POINTS ACROSS OUR AREA AND THIS SET OF
GUIDANCE SUGGESTS AFTERNOON DEW POINTS WILL REMAIN GENERALLY IN
THE LOW TO MID 60S ACROSS OUR AREA...WITH PERHAPS A FEW UPPER 60
READINGS ACROSS OUR EAST...WHICH IS ALSO WHAT THE NAM CONTINUES TO
SUGGEST. FOLLOWING CLOSER TO THE NAM WOULD ALSO SUGGEST 0-1KM
MLCAPE VALUES OF ~1000J/KG WILL BE IN PLACE ACROSS THE AREA THIS
AFTERNOON AND EVENING. NOT THAT THESE POTENTIAL INSTABILITY VALUES
ARE SOMETHING TO GET OVERLY EXCITED ABOUT BUT WITH THE UPPER LEVEL
JET AXIS OVER THE AREA...DEEP LAYER BULK SHEAR VALUES ON THE ORDER
OF 40KTS WILL ALSO LIKELY BE PRESENT. ALTHOUGH INITIAL UPDRAFT
STRENGTH WILL LIKELY BE MARGINAL AT BEST FOR LARGE HAIL
PRODUCTION...THE ROTATIONAL POTENTIAL OF SAID UPDRAFT MAY ENHANCE
IT ENOUGH FOR A BETTER HAIL THREAT. GIVEN ALL THIS...IT STILL
SEEMS POSSIBLE THAT UPDRAFT STRENGTH COULD BE STRONG ENOUGH TO
SUPPORT LARGE HAIL AND AS A RESULT...WILL GO AHEAD AND CONTINUE TO
OUTLOOK THE AREA FOR POSSIBLE SEVERE WEATHER THIS AFTERNOON AND
EVENING. LOSS OF DIABATIC HEATING POST-SUNSET SHOULD KILL ANY
CONVECTION BEYOND 03Z THIS EVENING...WITH AN OVERALL LACK IN
KINEMATIC FORCING LIKELY PROVIDING DRY CONDITIONS TO THE AREA 03Z-
18Z TUESDAY.
GUIDANCE FROM THE NAM...OPERATIONAL GFS...AND EC ALL SUGGEST A
MORE SIGNIFICANT MID LEVEL SHORT WAVE WILL PUSH INTO SOUTH CENTRAL
CANADA AND PORTIONS OF THE NORTH CENTRAL CONUS TUESDAY INTO
TUESDAY NIGHT. A RESULTANT AREA OF SURFACE LOW PRESSURE IS
EXPECTED TO PUSH ACROSS THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY DURING THE SAME TIME PERIOD...WITH AN ASSOCIATED SURFACE
COLD FRONT EXPECTED TO SWEEP ACROSS NEBRASKA. AT THIS TIME THE LOW
LEVEL BAROCLINIC ZONE IS EXPECTED TO NEAR NORTH/NORTHWESTERN
PORTIONS OF OUR CWA BY 00Z WEDNESDAY...LIKELY CLEARING THE ENTIRE
CWA BY 12Z WEDNESDAY. SURFACE-BASED CONVECTION WILL BE POSSIBLE IN
THE VICINITY OF THIS LOW LEVEL BAROCLINIC ZONE ACROSS OUR
NORTH/NORTHWEST BY LATE AFTERNOON TUESDAY...WITH ADDITIONAL
CONVECTIVE ACTIVITY PERHAPS SPREADING SOUTHEAST ACROSS THE CWA
HEADING INTO THE EVENING AND OVERNIGHT HOURS TUESDAY. GIVEN ALL
THIS...WILL GO AHEAD WITH 20%-30% POPS ACROSS THE CWA 21Z TUESDAY
THROUGH 12Z WEDNESDAY. POOLING OF LOW LEVEL MOISTURE AHEAD OF THE
LOW LEVEL BAROCLINIC ZONE...AS SUGGESTED BY THE NAM...MAY ACTUALLY
HELP TO INCREASE POTENTIAL INSTABILITY ACROSS OUR AREA WHEN
COMPARED TO MONDAY...WITH THE NAM SUGGESTING 0-1KM MLCAPE VALUES
ON THE ORDER OF 1500J/KG POSSIBLE TUESDAY AFTERNOON INTO THE
EVENING HOURS. IN ADDITION...DEEP LAYER BULK SHEAR VALUES OF
AROUND 35KTS WILL ALSO BE IN EXISTENCE. GIVEN ALL THIS...WILL
CONTINUE THE SEVERE WEATHER MENTION IN THE HWO FOR TUESDAY.
A COOLER AND DRIER AIRMASS WILL SETTLE IN ACROSS THE AREA BEHIND
THE LOW LEVEL BAROCLINIC ZONE WEDNESDAY AND WEDNESDAY NIGHT...AND
AN OVERALL LACK IN KINEMATIC FORCING SHOULD PRESENT DRY CONDITIONS
TO OUR AREA 12Z WEDNESDAY THROUGH 12Z THURSDAY.
AN EASTERLY COMPONENT TO THE LOW LEVEL WIND FIELD AND A SLIGHTLY
COOLER AIRMASS WILL PRESENT COOLER CONDITIONS TO THE AREA TODAY
WHEN COMPARED TO SUNDAY...WITH AFTERNOON HIGHS IN THE LOW TO MID
90S EXPECTED THROUGH MOST LOCATIONS. WARMER WEATHER AHEAD OF THE
APPROACHING LOW LEVEL BAROCLINIC ZONE WILL LIKELY PRESENT
AFTERNOON HIGHS IN THE MID TO UPPER 90S ON TUESDAY. THE COOLER
AIRMASS ON WEDNESDAY WILL LIKELY KEEP AFTERNOON HIGHS IN THE 80S
TO FINISH OUT THE SHORT TERM FORECAST PERIOD. OVERNIGHT LOWS IN
THE 60S WILL REMAIN THE NORM MONDAY NIGHT AND TUESDAY NIGHT...WITH
THE COOLER AIRMASS LIKELY PROMOTING TEMPERATURES IN THE 50S
WEDNESDAY NIGHT INTO THURSDAY MORNING.
.LONG TERM...THURSDAY THROUGH SUNDAY. PRIMARY FORECAST CONCERNS
LIE WITH END OF THE WEEK PRECIPITATION CHANCES...AND TEMPERATURES.
THE START OF THE LONG TERM PERIOD SHOWS MODELS NOT IN TOO BAD OF
AGREEMENT WITH THE PATTERN ACROSS THE CONUS...WHICH REMAINS
ZONAL...SET UP BETWEEN BROAD HIGH PRESSURE EXTENDING ACROSS THE
DESERT SW AND SRN PLAINS...WHILE A LARGE LOW PRESSURE SYSTEM SPINS
OVER CENTRAL CANADA. THROUGH THE END OF THE WORK
WEEK...PRECIPITATION CHANCES CONTINUE ACROSS THE CWA...DRIVEN BY A
COUPLE OF DISTURBANCES ASSOCIATED WITH THAT CANADIAN LOW PRESSURE
SYSTEM. THE FIRST ONE LOOKS TO AFFECT THE AREA MAINLY ON
THURSDAY/THURSDAY NIGHT...ALSO PUSHING A SURFACE BOUNDARY INTO
ROUGHLY THE NORTHERN HALF OF THE CWA DURING THE AFTERNOON HOURS.
THE SECOND DISTURBANCE...DIVING BASICALLY STRAIGHT SOUTH OUT OF
CANADA...AFFECTS THE AREA MAINLY FRIDAY/FRIDAY EVENING. KEPT POPS
CWA-WIDE THURS/THURS NIGHT/FRI...WITH ONLY A FEW LINGERING POPS
INTO FRIDAY NIGHT ACROSS NC KS...AND IF CURRENT MODEL TRENDS
CONTINUES...THOSE FRIDAY EVENING/NIGHT POPS COULD BE REMOVED. AS
MENTIONED...THURSDAY SEE THE INITIAL FRONT MOVE INTO THE CWA...BUT
THAT SECOND DISTURBANCE WILL USHER IN A REINFORCING COLD
FRONT...ACCOMPANIED BY THE COOLER/DRIER AIR FOR FRIDAY. FORECAST
HIGHS FOR THURSDAY SIT IN THE 80S...WHILE FRIDAY IS IN THE MID
70S/LOWER 80S. WILL KEEP THE MENTION OF SOME STRONG/SEVERE
THUNDERSTORMS GOING FOR THIS PERIOD WITH MODELS CONTINUING TO SHOW
THE POTENTIAL FOR DECENT INSTABILITY/SHEAR IN THE AREA.
PLEASANT CONDITIONS ON TAP FOR THE UPCOMING WEEKEND...WITH MODELS
DEPICT DRIER NORTHWESTERLY FLOW SETTING UP IN THE UPPER LEVELS
ACROSS THE CENTRAL PLAINS...SITTING BETWEEN THE TROUGH/LOW OVER
THE GREAT LAKES AND MIDWEST...WHILE RIDGING BUILDS INTO THE
ROCKIES. HIGH PRESSURE LOOKS TO BE THE PRIMARY PLAYER AT THE
SURFACE...BUILDING IN FROM THE NORTHWEST BEHIND THE END OF THE
WORK WEEK FRONTAL PASSAGE. EXPECTING TO SEE PLENTY OF
SUNSHINE...WITH FAIRLY LIGHT WINDS /ESP ON SAT/. THE AREA OF SFC
HIGH PRESSURE LOOKS TO BE CENTERED RIGHT OVER THE CWA ON
SATURDAY...BEFORE SLIDING OFF SLIGHTLY TO THE EAST ON SUNDAY...AND
EXPECTING SATURDAY TO BE A TOUCH COOLER THAN SUNDAY. CURRENT
FORECAST HIGHS ON SATURDAY SIT IN THE MID 70S...WITH SUNDAY
CREEPING UP INTO THE UPPER 70S TO LOWER 80S...BOTH DAYS FEELING
PRETTY NICE WITH DEWPOINTS LOOKING TO BE IN THE 40S FOR MOST
LOCATIONS.
&&
.PREV DISCUSSION... /ISSUED 1222 AM CDT MON SEP 3 2012/
AVIATION...06Z KGRI TAF. VFR CONDITIONS TO CONTINUE THROUGH THE
NEXT 24 HOURS. INCREASING MID TO HIGH LEVEL CLOUDS WILL BE
OBSERVED AT THE TERMINAL DURING THE DAY MONDAY...BUT NOTHING BELOW
10000FT AGL CURRENTLY FORECAST. SURFACE WINDS WILL REMAIN LIGHT
AND VARIABLE THROUGH 14Z...THEN BECOMING MORE ESTABLISHED FROM THE
EAST AT AROUND 12KTS BEFORE ONCE AGAIN BECOMING LIGHT AND VARIABLE
AROUND 02Z. ISOLATED SHOWERS OR THUNDERSTORMS WILL BE POSSIBLE AT
THE TERMINAL THROUGH THE NEXT 24 HOURS...BUT CHANCES OF MEASURABLE
PRECIPITATION ACTUALLY BEING REALIZED AT KGRI ARE TOO LOW FOR
INSERTION INTO THE TAF AT THIS TIME. VISIBILITY RESTRICTIONS ARE
NOT EXPECTED THROUGH THE NEXT 24 HOURS.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
SHORT TERM/AVIATION...BRYANT
LONG TERM...ADO
AREA FORECAST DISCUSSION...RETRANSMITTED
NWS RALEIGH NC
805 PM EDT TUE SEP 4 2012
.SYNOPSIS...
A WARM AND MOIST AIRMASS WILL PERSIST OVER THE AREA THROUGH
THURSDAY... AS A LINGERING TROUGH OF LOW PRESSURE HOLDS OVERHEAD. A
DRIER AIR MASS WILL MOVE IN LATE IN THE WEEK...BUT A STRONG LOW
PRESSURE AREA WILL APPROACH FROM THE WEST OVER THE WEEKEND...
BRINGING A RETURN TO UNSETTLED WEATHER.
&&
.NEAR TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
AS OF 805 PM TUESDAY...
THE LATEST SURFACE ANALYSIS SHOWED A WEAK SURFACE TROUGH OVER THE
FAR WESTERN PIEDMONT...ALSO SHOWING UP ON MSAS AS AN AREA OF WEAK
SURFACE CONVERGENCE. HOWEVER...PARTIALLY DUE TO LIMITED
INSTABILITY...A RELATIVE MINIMUM OF THAT IN VICINITY OF THE TROUGH
ON THE LATEST MSAS...STORMS WERE HAVING A HARD TIME BECOMING ROBUST.
WHERE THE GREATER INSTABILITY WAS OVER THE COASTAL PLAIN...WITH MSAS
LIFTED INDEX VALUES NEARLY TO -5C...SLIGHTLY DRIER AIR AND MORE
OVERALL CIN AS NOTED ON NEAR-TERM NAM AND GFS BUFR SOUNDINGS WERE
LIKELY CONTRIBUTING TO SCANT DEVELOPMENT AS OF THIS WRITING.
OVERNIGHT...BOTH THE 18Z AND THE LATEST RAP DIMINISH LIFT BY 06Z...
AND EVEN THE GFS...WITH QPF LINGERING LONGER THROUGH THE OVERNIGHT
DESPITE STABILIZING BUFR SOUNDINGS IN CENTRAL NORTH CAROLINA...HAS
850MB LIFT DIMINISHING AS CONVERGENCE ALOFT INCREASES. THE LATEST
RADAR TRENDS SUPPORT THE LATEST HRRR WRF...WITH MUCH OF THE DEEP
CONVECTION HAVING DIMINISHED BY 05Z.
HIGHER PRECIPITABLE WATER AIR SPREADS EAST OVERNIGHT...SO THAT BY
12Z BASICALLY ALL OF CENTRAL NORTH CAROLINA IS IN A SIMILAR AIR MASS
WITH PRECIPITABLE WATER VALUES AROUND TWO INCHES AND K INDICES AT OR
APPROACHING THE MID 30S. SURFACE-BASED AND DCAPE VALUES FALL...AND
THE NAM ACTUALLY SEEMS TO FORECAST A SLIGHT INCREASE IN SURFACE
RIDGING THAT MAY HELP TO LIMIT DEVELOPMENT OVERNIGHT. IN THE MOIST
AIR MASS...AND WITH A SHEAR AXIS ALOFT OR JUST OFF TO OUR WEST...
WILL CONTINUE THE ISOLATED SHOWERS OVERNIGHT IN THE FORECAST...BUT
CURRENTLY IT IS EXPECTED MOST LOCATIONS LATE TONIGHT SHOULD REMAIN
DRY.
SREF PROBABILITIES OF VISIBILITIES BELOW 3 MILES ARE LIMITED
OVERNIGHT...IN CONCERT WITH THE LATEST MOS GUIDANCE...WHILE SREF
PROBABILITIES OF LOW CLOUDS ARE MOSTLY ABOVE 50 PERCENT BY 12Z
WEDNESDAY. THIS IS CONSISTENT WITH THE LATEST GFS AND NAM BUFR
SOUNDINGS. SHOULD BE PATCHY FOG AT BEST TOWARD THE COASTAL PLAIN
WHERE THE INCREASING CLOUDS SHOULD BE NOTED LATER...WITH FOG LIMITED
BY SOME WIND...ALBEIT LIGHT...CONTINUING OVERNIGHT. OVERNIGHT LOWS
NEAR PERSISTENCE...MAINLY 70 TO 73. -DJF
WEDNESDAY AND WEDNESDAY NIGHT:
STRONG DAYTIME HEATING WILL SERVE TO RENEW CONVECTIVE INITIATION
ACROSS CENTRAL NC WEDNESDAY AFTERNOON...FOCUSED ALONG THE LINGERING
SUBTROPICAL MOISTURE PLUME CONFINED WITHIN THE LOWER-MID LEVEL
TROUGH AXIS RESIDING OVER THE AREA. VERY SIMILAR TO THE PAST FEW
DAYS...THE MAIN CONCERN WILL BE FROM TRAINING...HEAVY RAIN PRODUCING
THUNDERSTORMS...WITH A SECONDARY/ISOLATED SEVERE THREAT DUE TO WEAK
WINDS ALOFT AND WEAK FORCING.
HIGHS WILL DEPEND ON HOW SOON WE GET CONVECTION TO POP...BUT WESTERN
PIEDMONT PORTIONS OF THE AREA SHOULD BE A GOOD 2 TO 3 DEGREES COOLER
THAN CENTRAL AND EASTERN AREAS WITH DELAYED HEATING FROM SLOWER
BREAKUP/BURN OFF OF MORNING STRATUS/FOG. HIGHS IN THE MID 80S NW TO
NEAR 90 JUST ABOUT EVERYWHERE ELSE. LOWS WEDNESDAY NIGHT THE LOWER
70S WITH AREAS OF STRATUS AND FOG. -CBL
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 230 PM TUESDAY...
UNSETTLED WEATHER WILL LIKELY PERSIST ACROSS CENTRAL NC THROUGH THE
SHORT TERM PERIOD AS WEAK TROUGHING...BOTH ALOFT AND AT THE
SURFACE...REMAINS OVER THE AREA. THIS COMBINED WITH AMPLE MOISTURE
(PWAT VALUES EXCEEDING 2 INCHES) AND A MODERATELY UNSTABLE AIR MASS
WILL RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS...MAINLY DURING
THE AFTERNOON AND EVENING HOURS. AT THIS TIME...AM EXPECTING GOOD
CHANCES AREAWIDE ON THURSDAY...WITH THE BEST COVERAGE THEN SHIFTING
TO THE EAST FOR THURSDAY AS SLIGHTLY DRIER AIR MOVES IN BEHIND THE
AFOREMENTIONED SURFACE TROUGH. THE MAIN THREAT IS EXPECTED TO BE
HEAVY RAIN THAT COULD LEAD TO SOME FLOODING...ESPECIALLY IN URBAN
AREAS...HOWEVER AN ISOLATED SEVERE STORM (WITH THE MAIN THREAT BEING
DAMAGING WIND) CANNOT BE COMPLETELY RULED OUT. HIGH TEMPS WILL BE
NEAR NORMAL TO SLIGHTLY ABOVE NORMAL...GENERALLY IN THE MID/UPPER
80S TO NEAR 90 DEGREES...WITH OVERNIGHT LOWS RUNNING SLIGHTLY ABOVE
NORMAL...GENERALLY IN THE UPPER 60S TO LOWER 70S.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 230 PM TUESDAY...
AN UNSETTLED WEATHER PATTERN IS EXPECTED TO CONTINUE THROUGH MUCH OF
THE LONG TERM PERIOD. A SHORT WAVE COMING OUT OF CENTRAL CANADA WILL
QUICKLY AMPLIFY AS IT MOVES ACROSS THE MIDWEST ON SATURDAY AND
EVENTUALLY BECOME CUTOFF OVER THE TN/OH VALLEY LATE IN THE
WEEKEND/EARLY NEXT WEEK. THIS WILL LEAVE CENTRAL NC IN DEEP
SOUTHWESTERLY/MOIST FLOW AND COMBINED WITH INCREASINGLY DIVERGENT
FLOW ALOFT...WE SHOULD SEE A PROLONGED PERIOD OF GOOD PRECIP CHANCES
THROUGH AT LEAST THE END OF THE WEEKEND. AS CAN BE EXPECTED THIS FAR
OUT...THERE ARE LOCATION...TIMING AND STRENGTH DIFFERENCES
(ESPECIALLY WITH HOW TO HANDLE THE EASTWARD PROGRESSION OF THE CUT
OFF UPPER LOW EARLY NEXT WEEK)...BUT WILL BEGIN TO TAPER POPS
DOWNWARD LATE SUNDAY AND INTO EARLY NEXT WEEK. THERE ARE STILL
FAIRLY STRONG INDICATIONS THAT COOLER AND DRIER AIR SHOULD ARRIVE
SOMETIME EARLY NEXT WEEK AS THE RATHER DEEP TROUGH/CUT OFF LOW
DEVELOPS AND EVENTUALLY MOVES EAST OF THE AREA...RESULTING IN DEEP
NORTHWESTERLY FLOW ACROSS THE REGION. OVERALL...TEMPS WILL BE NEAR
NORMAL EARLY ON IN THE PERIOD BEFORE TRENDING BELOW NORMAL AS
INCREASED PRECIP CHANCES AND THE DEEP TROUGH/ASSOCIATED SURFACE
FRONT APPROACH AND MOVE THROUGH THE REGION.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AS OF 745 PM TUESDAY...
CONFIDENCE IS HIGH THAT AVIATION CONDITIONS WILL DETERIORATE AFTER
NIGHTFALL... AND PARTICULARLY AFTER MIDNIGHT... AT ALL CENTRAL NC
TERMINAL FORECAST SITES. THE RISK OF A SHOWER OR ISOLATED STORM WILL
PERSIST NEAR INT/GSO THROUGH 04Z BUT THE CHANCE WILL QUICKLY
DIMINISH AFTER 02Z. ELSEWHERE AT RDU/FAY/RWI... THE CHANCE OF A
SHOWER OR STORM FOR THE REMAINDER OF THE NIGHT IS VERY SMALL. AFTER
04Z... THE RECENT RAINS AND RESULTANT WET GROUND COMBINED WITH VERY
LIGHT WIND FROM THE SE OR SOUTH WILL FAVOR DEVELOPMENT OF LOW
STRATUS AFTER MIDNIGHT. SREF AVIATION PROBABILITIES SHOW A VERY GOOD
CHANCE OF CIGS UNDER 1 KFT OVERNIGHT... ESPECIALLY AT INT/GSO... AND
FORECAST SOUNDINGS SUGGEST THAT CIGS COULD BE LOWER THAN 600 FT AGL.
EXPECT AROUND A 200-500 FT CIG AT ALL SITES AFTER 07Z OR 08Z
TONIGHT... HOLDING THROUGH AROUND 13Z WHEN THE CLOUDS WILL BEGIN TO
LIFT AND MIX OUT TO SCATTERED. VSBYS WILL BE GENERALLY MVFR BETWEEN
07Z AND 13Z... ALTHOUGH VSBYS COULD GET LOWER AT TOWERS... AS CIGS
LOWER. VFR CONDITIONS ARE EXPECTED TO RETURN AFTER 13Z OR 14Z
WEDNESDAY MORNING. THE CHANCE FOR STORMS WEDNESDAY AFTERNOON DOES
NOT APPEAR TO BE HIGH ENOUGH TO INCLUDE AS A PREVAILING CONDITION AT
THIS TIME... BUT THE MOST LIKELY LOCATION OF ANY STORMS WEDNESDAY
AFTERNOON WILL BE AT INT/GSO/RDU.
LOOKING BEYOND 00Z THURSDAY (WEDNESDAY EVENING)... ANOTHER ROUND OF
LOW CIGS AND VSBYS IS EXPECTED LATE WEDNESDAY NIGHT INTO THURSDAY
MORNING AREAWIDE. WE MAY SEE A BRIEF RESPITE FROM THE DAILY
SLOW-MOVING HEAVY-RAIN-PRODUCING STORMS FROM FRIDAY INTO SATURDAY...
HOWEVER MORE RAIN AND STORMS ARE EXPECTED SUNDAY. -GIH
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...HARTFIELD
NEAR TERM....DJF/CBL
SHORT TERM...KRR
LONG TERM...KRR
AVIATION...HARTFIELD
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
147 PM EDT MON SEP 3 2012
.SYNOPSIS...
THE REMNANTS OF ISAAC WILL EFFECT THE REGION THROUGH TUESDAY
NIGHT. BRIEF DRY AIR CAN BE EXPECTED FOR WEDNESDAY. A WEAK COLD
FRONT ARRIVES THURSDAY...FOLLOWED BY LOW PRESSURE FOR NEXT WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
1030 AM UPDATE. CONFIDENCE LOW TO MEDIUM. HAVE INCREASED POPS IN THE
EAST THIS AFTERNOON AND MAINTAINED FF WATCH IN THE NORTH. WILL TWEAK
TEMPS DOWN JUST A BIT IN THE WEST WITH THE CLOUDS.
VERY TROPICAL AND MOIST ADIABATIC ATMOSPHERE WITH PW`S ABOVE 2
INCHES SUGGESTS THAT IT WILL NOT TAKE MUCH TO INITIATE CONVECTION DUE
TO HEATING AND ANY VORT MAX ROTATING AROUND THE REMAINS OF ISAAC
CENTERED OVER CENTRAL KENTUCKY AT TIME. PROBLEM IS THE LARGE SHIELD
OF CLOUDS REMAINING OVER THE CWA FROM RAPIDLY DYING ELEVATED INDUCED
SHOWERS FROM THE WEST...AND IN TRYING TO DETERMINE THE MODEL
INDICATED VORT MAXES THAT WILL BE ENOUGH TO FORCE CONVECTION IN
SPITE OF THE CLOUDS. CURRENT INDICATIONS BY SATELLITE AND RADAR ARE
THAT SUNSHINE WILL BE LIMITED THIS AFTERNOON SINCE ANY DECREASE IN
MID LEVEL CLOUDS WILL QUICKLY BE REPLACED BY A CU SHIELD...WITH BEST
BREAKS IN THE EAST. BOTTOM LINE IS THAT POPS IN THE WEST WILL NOT BE
REDUCED GIVEN UNCERTAINTY AND RAISED IN THE EAST WITH MORE CLOUD
BREAKS. ANY STORM COULD PRODUCE LOCALLY HEAVY RAIN.
630AM UPDATE...
TWEAKED POPS TO ACCOUNT FOR ONGOING PCPN BAND ACROSS SE OH. STILL
LOOKING FOR AFTN DEVELOPMENT AFTER SOME OF THE CLDS BURN OFF SOME.
LATEST HRRR SHOWS THIS DEVELOPMENT ARND 18Z ACROSS W AND S...AND
ROTATING THRU LATER IN AFTN.
PREVIOUS DISCUSSION BELOW...
CIRCULATION WITH ISAAC TO SLOWLY CONT TO MOVE SE THRU C KY AND TN
IN THE NEAR TERM. AS IT DOES SO IT WILL ALSO CONT TO
WEAKEN...OPENING UP INTO A BROAD TROF TONIGHT. STILL ROLLING WITH
CONSENSUS PLACEMENT OF H5 VORT/MID LVL DEFORMATION AXIS FOR
PLACEMENT AND TIMING OF POPS FROM BANDS SPIRALING INTO AREA. ONE
SUCH BAND CONT TO WEAKEN ACROSS EASTERN KY...STRUGGLING TO MAKE
MUCH E PROGRESS. THINK SOME ADDITIONAL DEVELOPMENT MAY FORM JUST
AHEAD OF WHAT IS LEFT OF THIS BAND WITH LINGERING INSTABILITY
NOTED ACROSS THE CWA. WILL FINESSE DETERMINISTIC POPS FOR THIS
EARLY MORNING WITH THIS THINKING IN MIND...HOLDING CAT AND LKLY
POPS ACROSS W AND S ZONES. TRACK THIS N THRU CWA AFTER SUNRISE
WITH YET ANOTHER BAND POISED TO ROTATE THRU LATER IN THE DAY. AS
SUCH DONT EXPECT WASHOUT OF A DAY...WITH SOME LULLS IN BETWEEN.
QPF TDY DEPENDENT ON HOW CONVECTIVE THE ACTION IS. WITH PWATS
STILL RUNNING ABV 2 INCHES...POTENTIAL EXISTS FOR SOME LCL 1 TO 2
INCHES OF RAIN...WITH A GENERAL HALF INCH TO INCH EXPECTED MOST
PLACES. FFG CONT TO RUN ON HIGH SIDE ACROSS NE KY DOWN THRU SW WV
AND SW VA WITH LWR VALUES ACROSS SE OH INTO C AND N WV. IT IS THIS
AREA THAT IS OF CONCERN...AS 1.5 TO 2.5 INCHES OF RAIN FELL THERE
YESTERDAY. GIVEN THAT...AND ENOUGH CONFIDENCE ON PLACEMENT OF VORT
THIS AFTN AND EVE ACROSS ESPECIALLY SE OH...WILL HOIST A FLASH
FLOOD WATCH THRU THIS EVENING FOR NORTHERN TIER OF CO FROM PERRY
TO HARRISON.
EXPECT ACTION TO WANE AFTER SUNSET WITH LOSS OF HEATING. HOWEVER
WITH A COUPLE MORE SPOKES PROGGED ON MDLS TO MOVE THRU OVERNIGHT
TONIGHT...KEPT SOME CHC POPS IN. THINK SOME LOW STRATUS WILL BE IN
THE CARDS TONIGHT AS WELL...LESS SO PERHAPS OVER C WV DUE TO WEAK DOWNSLOPING.
GUIDANCE TIGHTLY CLUSTERED FOR TEMPS...SO ROLLED WITH A BLEND.
&&
.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
MOISTURE FROM ISAAC REMAINS OVER THE AREA ON TUESDAY. MODEL
SOUNDINGS CONTINUE TO LOOK VERY UNSTABLE. THEREFORE WILL GO WITH
LIKELY POPS DURING THE AFTERNOON HOURS. THE MOISTURE FINALLY PUSHES
EAST OF THE AREA TUESDAY NIGHT AND EARLY WEDNESDAY. THEREFORE...WILL
REMOVE POPS ON WEDNESDAY AFTERNOON. A WEAK MOISTURE STARVED COLD
FRONT PUSHES INTO THE AREA ON THURSDAY. PRECIPITATION LOOKS VERY
IFFY...SO WILL KEEP ONLY VERY SMALL POPS WITH THE FRONT.
&&
.LONG TERM /FRIDAY THROUGH SUNDAY/...
SOME RESIDUAL MOISTURE REMAINS IN PLACES AS WEAK SURFACE HIGH
PRESSURE BUILDS OVER THE FORECAST AREA. BY DAY 7 MODELS SHOW SHOW
SOME MODEST SPREAD WITH TROUGH DIGGING INTO THE UPPER MIDWEST WITH
BAROCLINIC APPROACHING FROM THE WEST. BOTH GFS AND EURO MODEL
GENERALLY CLOSE WITH TIMING THE NEXT FEATURE ACROSS. FOLLOWED HPC
POP AND TEMP TRENDS WITH MINOR ADJUSTMENTS.
&&
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
18Z MONDAY THRU 18Z TUESDAY...
THROUGH THIS AFTERNOON...VFR CEILINGS OUTSIDE CONVECTION.
CONVECTION INCREASES WITH SFC HEATING...ESPECIALLY IN THE MOUNTAINS.
THUS INSERTED TEMPO GROUPS FOR THUNDER...ESPECIALLY MOUNTAINS.
TONIGHT...ACTIVITY WANES WITH SUNSET BUT STILL SCATTERED CONVECTION
OVERNIGHT...ESPECIALLY MOUNTAINS. GRADUALLY BRING CIGS DOWN INTO MVFR
RANGE AS LLVL MOISTURE SHIELD ENCROACHES UPON THE AREA. COULD ALSO
SEE SOME IFR CIGS ON THE EASTERN SLOPES ON SE UPSLOPE FLOW AND IN
PROTECTED VALLEYS THAT RECEIVE RAIN.
AFTER 12Z TUESDAY...BECOMING VFR CEILINGS BY 15Z. WIDELY SCATTERED
TO SCATTERED CONVECTION CONTINUES...INCREASING AFTER 18Z.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z TUESDAY...
FORECAST CONFIDENCE: LOW TO MEDIUM.
ALTERNATE SCENARIOS: TIMING OF SHOWERS AND THUNDERSTORMS COULD VARY.
STRATUS AND FOG TONIGHT COULD VARY.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
UTC 1HRLY 18 19 20 21 22 23 00 01 02 03 04 05
EDT 1HRLY 14 15 16 17 18 19 20 21 22 23 00 01
CRW CONSISTENCY H H H H H H H H H H H H
HTS CONSISTENCY H H H H H H H H H H H H
BKW CONSISTENCY H H H H H H H H H H M M
EKN CONSISTENCY H H H H H H H H H H H H
PKB CONSISTENCY H H H H H H H H H H H H
CKB CONSISTENCY H H H H H H H H H H H M
AFTER 18Z TUESDAY...
IFR IN HEAVY SHOWERS AND THUNDERSTORMS POSSIBLE WITH THE REMNANTS OF
TROPICAL STORM ISAAC AT TIMES THROUGH TUESDAY NIGHT.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...FLASH FLOOD WATCH UNTIL 11 PM EDT THIS EVENING FOR WVZ010-011-
020-031.
OH...FLASH FLOOD WATCH UNTIL 11 PM EDT THIS EVENING FOR OHZ066-067-
076.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...RPY/30
NEAR TERM...JMV/30
SHORT TERM...RPY
LONG TERM...KMC
AVIATION...JMV
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
629 AM EDT MON SEP 3 2012
.SYNOPSIS...
THE REMNANTS OF ISAAC WILL EFFECT THE REGION THROUGH TUESDAY
NIGHT. BRIEF DRY AIR CAN BE EXPECTED FOR WEDNESDAY. A WEAK COLD
FRONT ARRIVES THURSDAY...FOLLOWED BY LOW PRESSURE FOR NEXT WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
630AM UPDATE...
TWEAKED POPS TO ACCOUNT FOR ONGOING PCPN BAND ACROSS SE OH. STILL
LOOKING FOR AFTN DEVELOPMENT AFTER SOME OF THE CLDS BURN OFF SOME.
LATEST HRRR SHOWS THIS DEVELOPMENT ARND 18Z ACROSS W AND S...AND
ROTATING THRU LATER IN AFTN.
PREVIOUS DISCUSSION BELOW...
CIRCULATION WITH ISAAC TO SLOWLY CONT TO MOVE SE THRU C KY AND TN
IN THE NEAR TERM. AS IT DOES SO IT WILL ALSO CONT TO
WEAKEN...OPENING UP INTO A BROAD TROF TONIGHT. STILL ROLLING WITH
CONSENSUS PLACEMENT OF H5 VORT/MID LVL DEFORMATION AXIS FOR
PLACEMENT AND TIMING OF POPS FROM BANDS SPIRALING INTO AREA. ONE
SUCH BAND CONT TO WEAKEN ACROSS EASTERN KY...STRUGGLING TO MAKE
MUCH E PROGRESS. THINK SOME ADDITIONAL DEVELOPMENT MAY FORM JUST
AHEAD OF WHAT IS LEFT OF THIS BAND WITH LINGERING INSTABILITY
NOTED ACROSS THE CWA. WILL FINESSE DETERMINISTIC POPS FOR THIS
EARLY MORNING WITH THIS THINKING IN MIND...HOLDING CAT AND LKLY
POPS ACROSS W AND S ZONES. TRACK THIS N THRU CWA AFTER SUNRISE
WITH YET ANOTHER BAND POISED TO ROTATE THRU LATER IN THE DAY. AS
SUCH DONT EXPECT WASHOUT OF A DAY...WITH SOME LULLS IN BETWEEN.
QPF TDY DEPENDENT ON HOW CONVECTIVE THE ACTION IS. WITH PWATS
STILL RUNNING ABV 2 INCHES...POTENTIAL EXISTS FOR SOME LCL 1 TO 2
INCHES OF RAIN...WITH A GENERAL HALF INCH TO INCH EXPECTED MOST
PLACES. FFG CONT TO RUN ON HIGH SIDE ACROSS NE KY DOWN THRU SW WV
AND SW VA WITH LWR VALUES ACROSS SE OH INTO C AND N WV. IT IS THIS
AREA THAT IS OF CONCERN...AS 1.5 TO 2.5 INCHES OF RAIN FELL THERE
YESTERDAY. GIVEN THAT...AND ENOUGH CONFIDENCE ON PLACEMENT OF VORT
THIS AFTN AND EVE ACROSS ESPECIALLY SE OH...WILL HOIST A FLASH
FLOOD WATCH THRU THIS EVENING FOR NORTHERN TIER OF CO FROM PERRY
TO HARRISON.
EXPECT ACTION TO WANE AFTER SUNSET WITH LOSS OF HEATING. HOWEVER
WITH A COUPLE MORE SPOKES PROGGED ON MDLS TO MOVE THRU OVERNIGHT
TONIGHT...KEPT SOME CHC POPS IN. THINK SOME LOW STRATUS WILL BE IN
THE CARDS TONIGHT AS WELL...LESS SO PERHAPS OVER C WV DUE TO WEAK DOWNSLOPING.
GUIDANCE TIGHTLY CLUSTERED FOR TEMPS...SO ROLLED WITH A BLEND.
&&
.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
MOISTURE FROM ISAAC REMAINS OVER THE AREA ON TUESDAY. MODEL
SOUNDINGS CONTINUE TO LOOK VERY UNSTABLE. THEREFORE WILL GO WITH
LIKELY POPS DURING THE AFTERNOON HOURS. THE MOISTURE FINALLY PUSHES
EAST OF THE AREA TUESDAY NIGHT AND EARLY WEDNESDAY. THEREFORE...WILL
REMOVE POPS ON WEDNESDAY AFTERNOON. A WEAK MOISTURE STARVED COLD
FRONT PUSHES INTO THE AREA ON THURSDAY. PRECIPITATION LOOKS VERY
IFFY...SO WILL KEEP ONLY VERY SMALL POPS WITH THE FRONT.
&&
.LONG TERM /FRIDAY THROUGH SUNDAY/...
SOME RESIDUAL MOISTURE REMAINS IN PLACES AS WEAK SURFACE HIGH
PRESSURE BUILDS OVER THE FORECAST AREA. BY DAY 7 MODELS SHOW SHOW
SOME MODEST SPREAD WITH TROUGH DIGGING INTO THE UPPER MIDWEST WITH
BAROCLINIC APPROACHING FROM THE WEST. BOTH GFS AND EURO MODEL
GENERALLY CLOSE WITH TIMING THE NEXT FEATURE ACROSS. FOLLOWED HPC
POP AND TEMP TRENDS WITH MINOR ADJUSTMENTS.
&&
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
GENERALLY PREDOMINATE VFR CONDITIONS EXPECTED THROUGH THIS AFTN.
FG AT KEKN SHOULD BURN OFF BY 13Z. WIDESPREAD SHRA ASSOCIATED WITH
CIRCULATION WILL STRUGGLE TO MAKE INROADS E INTO THE AREA THIS
MORNING. EVEN SO...STILL THINK SCT SHRA A GOOD BET THIS
MORNING...ESPECIALLY ALONG AND W OF OH RVR. HAVE SOME VCSH IN
MOST TAF SITES. AS DAY PROGRESSES...EXPECT COVERAGE TO INCREASE
ONCE AGAIN AIDED ON SFC HEATING. KEPT VFR SHRA VCTS AT THIS
DISTANCE THOUGH AS CONFIDENCE ON TIMING OF ANY TERMINAL GETTING
HIT IS LOW.
ACTIVITY WANES WITH SUNSET BUT STILL ISO TO SCT SHRA EXPECTED
TONIGHT. GRADUALLY BRING CIGS DOWN INTO MVFR RANGE AS LLVL
MOISTURE SHIELD ENCROACHES UPON THE AREA. ENOUGH DOWNSLOPING MAY
EXIST THOUGH TO KEEP KCRW/KCKB IN LOW VFR. COULD ALSO SEE SOME IFR
CIGS ON THE EASTERN SLOPES ON SE UPSLOPE FLOW.
THE FLOW ALOFT WILL BECOME MODERATE TDY...WHEN SOME GUSTS ARE
POSSIBLE AT BKW.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z TUESDAY...
FORECAST CONFIDENCE: MEDIUM TO HIGH.
ALTERNATE SCENARIOS: TIMING OF SHOWERS AND THUNDERSTORMS COULD
VARY. STRATUS TONIGHT COULD VARY.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
UTC 1HRLY 11 12 13 14 15 16 17 18 19 20 21 22
EDT 1HRLY 07 08 09 10 11 12 13 14 15 16 17 18
CRW CONSISTENCY H H H H H H H H H H H H
HTS CONSISTENCY H H H H M H H H H H H H
BKW CONSISTENCY H H H H H H H H H H H H
EKN CONSISTENCY M M L H H H H H H H H H
PKB CONSISTENCY L L H H H H H M H H H H
CKB CONSISTENCY H H H H H H H M H H H H
AFTER 12Z TUESDAY...
IFR IN HEAVY SHOWERS AND THUNDERSTORMS POSSIBLE WITH THE REMNANTS OF
TROPICAL STORM ISAAC AT TIMES THROUGH TUESDAY NIGHT.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...FLASH FLOOD WATCH THROUGH THIS EVENING FOR WVZ010-011-020-031.
OH...FLASH FLOOD WATCH THROUGH THIS EVENING FOR OHZ066-067-076.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...RPY/30
NEAR TERM...30
SHORT TERM...RPY
LONG TERM...KMC
AVIATION...30
AREA FORECAST DISCUSSION
NWS WILMINGTON OH
222 AM EDT MON SEP 3 2012
.SYNOPSIS...
LOW PRESSURE WILL MOVE SLOWLY EASTWARD THROUGH THE OHIO VALLEY ON
MONDAY AND TUESDAY. A WEAK COLD FRONT WILL CROSS THE AREA ON
WEDNESDAY...WITH HIGH PRESSURE BUILDING IN FOR THE END OF THE
WEEK.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
BROKEN BAND OF SHOWERS ARC FROM NEAR RICHMOND INDIANA...DOWN TO
EAST OF CINCINNATI TO NR JACKSON KY IS FORECAST TO CONTINUE TO
PIVOT N TO NE OVERNIGHT. LATEST RUNS OF THE RAP AND NAM MODELS ARE
SUGGESTING THAT IT WILL WEAKEN/BREAK UP AS THE NIGHT
PROGRESSES...SO TRENDED THE FORECAST THAT WAY. KEPT SOME HIGHER
CHC POPS IN THE S BY 12Z...WITH MAINLY SLIGHT CHC POPS IN THE N.
DIDNT ADJUST LOWS FOR TONIGHT AS THEY LOOK ON TRACK. KEPT THEM IN
THE UPPER 60S TO LOWER 70S.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
THE EXPECTED EASTWARD MOVEMENT OF THE WEAKENING SURFACE LOW
APPEARS SLOWER ON THE MODEL RUNS TODAY...NECESSITATING LIKELY POPS
AT ALL LOCATIONS ON MONDAY AFTERNOON. THE ATMOSPHERIC MOISTURE
SITUATION WILL NOT CHANGE MUCH...SO HEAVY RAIN WILL AGAIN BE A
POSSIBILITY.
AS POST-ISAAC DISSOLVES AND BECOMES ABSORBED IN THE MEAN
FLOW...THERE ARE SOME SLIGHT TIMING DISAGREEMENTS IN HOW QUICKLY
THE MOISTURE AND FORCING WILL DEPART THE AREA ON TUESDAY. TAKING A
BLENDED APPROACH TO THE TIMING...IT DOES APPEAR THAT LIKELY POPS
WILL BE WARRANTED IN THE EASTERN CWA AS THE DIURNAL CYCLE TAKES
EFFECT.
TEMP FORECAST CHANGES WERE MINIMAL FOR MONDAY AND MONDAY NIGHT. WITH
GREATER EXPECTED CLEARING IN THE WEST ON TUESDAY...MAX TEMPS HAVE
BEEN INCREASED...ESPECIALLY WEST OF I-75.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
A BLEND OF HPC AND THE 00Z ECMWF WAS USED FOR THE LONG TERM
FORECAST.
THE REMNANTS OF ISAAC SHOULD EVENTUALLY MOVE EAST OF THE REGION
TUESDAY NIGHT WITH DECREASING CHANCES OF PCPN.
FOR WEDNESDAY...REGION WILL BE IN A RELATIVE A LULL. MODELS INDICATE
THAT A S/WV MAY PUSH ACRS THE REGION WEDNESDAY AFTN AND EVENING
AHEAD OF A COLD FRONT. THIS WILL WARRANT LOW CHANCE POPS ATTM.
TEMPERATURES WILL WARM INTO THE MID 80S TO NEAR 90.
A STRONGER S/WV IS FORECAST TO MOVE ACRS THE NRN GREAT LAKES
WEDNESDAY NIGHT AND THURSDAY. THIS WILL PUSH A WEAK COLD FRONT
ACROSS THE AREA. THERE WILL REMAIN A LOW CHANCE OF SHOWERS AND
THUNDERSTORMS UNTIL THIS PASSES.
HIGH PRESSURE WILL BRIEFLY BUILD IN THURSDAY NIGHT INTO THE FIRST
PART OF FRIDAY. WHILE THERE IS SOME DISCREPANCY IN MODEL SOLUTIONS
BY THE END OF THE WEEK...THERE ARE INDICATIONS THAT ANOTHER MORE
VIGOROUS SHORT WAVE WILL AFFECT THE REGION FRIDAY NIGHT AND
SATURDAY. THIS SYSTEM AND ITS ASSOCIATED LOW PRESSURE AND COLD FRONT
WILL HAVE TEMPERATURE IMPLICATIONS DEPENDING ON HOW IT DEVELOPS AND
MOVES ACRS THE OHIO VALLEY.
MODELS INDICATE THAT AFOREMENTIONED UPR LVL ENERGY MAY EVOLVE INTO A
CLOSED LOW OVER THE REGION FOR THE FIRST PART OF NEXT WEEK. THIS MAY
ALLOW A FEW SHOWERS TO LINGER.
TEMPERATURES WILL SHOW A GRADUAL COOLING TREND THROUGH THE PERIOD.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
LOW CIGS WERE DEVELOPING AND MOVING INTO THE KCVG AND KLUK TAF
SITES FOR THE BEGINNING OF THE TAF PERIOD. EXPECT CIGS TO LOWER
THROUGH THE OVERNIGHT TIME FRAME. SOME LIGHT SHOWERS WILL MOVE
ACROSS THE TAF SITES DURING THE OVERNIGHT HOURS. SOME HEAVIER RAIN
WILL MOVE ACROSS THE KCMH AND KLCK TAF SITES. ALTHOUGH THUNDER
CANNOT BE RULED OUT AT KCMH AND KLCK...THE THUNDER CHANCES ARE
MINIMAL AND THEREFORE HAVE LEFT OUT OF THE TAFS AT THIS TIME.
CIGS WILL BEGIN TO IMPROVE THROUGH THE MORNING HOURS WITH SOME OF
THE AREA TAF SITES EXPERIENCING VFR CONDITIONS FOR A TIME DURING
THE AFTERNOON AND EVENING HOURS ON MONDAY. ADDITIONAL SHOWER
ACTIVITY WILL DEVELOP DURING THE DAY. SOME LOCATIONS MAY SEE MVFR
VSBYS WITH SOME OF THE HEAVIER SHOWER ACTIVITY. SOME ISOLATED
THUNDER WILL BE POSSIBLE DURING THE AFTERNOON HOURS ON MONDAY
HOWEVER DUE TO THE ISOLATED NATURE OF THIS THUNDERSTORM ACTIVITY
HAVE AGAIN LEFT THE THUNDER MENTION OUT OF THE TAFS AT THIS TIME.
PRECIPITATION WILL TAPER OFF DURING THE LATE AFTERNOON AND INTO
THE EVENING HOURS ACROSS THE TAF SITES. EXPECT LOW CIGS AND
REDUCED VSBYS TO DEVELOP ONCE AGAIN MONDAY NIGHT ACROSS THE AREA
TAF SITES.
.OUTLOOK...MVFR TO IFR CEILINGS AND VISIBILITIES POSSIBLE MONDAY
NIGHT AND TUESDAY. THUNDERSTORMS ARE POSSIBLE WEDNESDAY.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.
&&
$$
SYNOPSIS...HATZOS
NEAR TERM...SITES
SHORT TERM...HATZOS
LONG TERM...HICKMAN
AVIATION...NOVAK
AREA FORECAST DISCUSSION
NWS CLEVELAND OH
1238 AM EDT MON SEP 3 2012
.SYNOPSIS...
THE REMNANTS OF ISAAC WILL MOVE EAST ACROSS THE OHIO VALLEY THROUGH
TUESDAY WITH A HUMID AIRMASS AND PERIODS OF HEAVY RAIN. A WEAK FRONT
WILL HELP TO DRY US OUT ON TUESDAY NIGHT WITH A STRONGER COLD
FRONT WITH AN AIRMASS CHANGE PUSHING SOUTH ACROSS THE AREA ON
THURSDAY.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
UPDATED TO SLOW DOWN THE TIMING OF SHOWERS OVER THE EXTREME
SOUTHERN COUNTIES AND ADJUSTED THE LOWS A LITTLE. WATCHING SOME
SHOWERS TO THE SOUTH OF COLUMBUS.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY NIGHT/...
LOW SPINNING ACROSS ILLINOIS WILL CONTINUE TO FILL AND DRIFT EAST-
SOUTHEAST OVER THE NEXT TWO DAYS. COVERAGE OF SHOWERS/TS COULD BE
ON THE UPTICK FOR MONDAY. HAVE MAINTAINED SOME OF THE LIKELY POPS
ESPECIALLY ACROSS THE SOUTH AND SOUTHEAST. STUCK WITH SIMILAR
HIGHS FOR TOMORROW. UPPER TROUGH BEGINS TO OPEN UP AND WITH SOME
DIURNAL HEATING TS SHOULD POP UP. WILL HAVE TO CONTINUE THE PRECIP
CHANCES INTO MONDAY NIGHT. AT THIS POINT WE WILL BE GETTING SOME
EXTRA UPPER SUPPORT IN THE FORM OF A SHORTWAVE/JET COMING ACROSS
THE GREAT LAKES. THE COLD FRONT WILL MOVE ACROSS TUESDAY. WE WILL
STILL HAVE TO BE ON THE LOOKOUT FOR HEAVIER RAINFALL ESPECIALLY
LATER MONDAY NIGHT AND TUESDAY WITH BETTER FOCUSING MECHANISMS
LOCALLY. LOCALIZED FLOODING WILL STILL BE A CONCERN THROUGH
TUESDAY.
WEDNESDAY LOOKS LIKE THE FIRST GOOD DRY/IN BETWEEN SYSTEMS DAY.
WEAK HIGH PRESSURE OVER THE AREA AND SOME SUN SHOULD BE ABLE TO
BRING TEMPS UP INTO THE MID 80S...OR MAYBE EVEN SOME UPPER 80S. WE
WILL NOT GET A GOOD AIRMASS CHANGE UNTIL AFTER WEDNESDAY NIGHT
WITH THE NEXT SYSTEM IN THE EXTENDED.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
A COLD FRONT WILL MOVE ACROSS THE REGION THURSDAY WITH SOME
SCATTERED SHOWERS AND THUNDERSTORMS ANTICIPATED. THE FRONT SHOULD
CLEAR THE ENTIRE REGION BY THURSDAY EVENING. THIS WILL ALLOW HIGH
PRESSURE TO RETURN FOR FRIDAY. THIS LOOKS TO BE SHORT LIVED AS THE
NEXT TROUGH MOVES INTO THE WESTERN GREAT LAKES ON FRIDAY.
TEMPERATURES WILL BE NEAR TO SLIGHTLY ABOVE SEASONAL AVERAGES ON
THURSDAY. COOLER IN THE WAKE OF THE FRONT FOR FRIDAY INTO SATURDAY
WITH HIGHS GENERALLY IN THE MIDDLE TO UPPER 70S.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
SATELLITE LOOP SHOWS THE CENTER OF THE REMNANTS OF ISAAC OVER SERN
IL AT 23Z WITH RADAR SHOWING CONVECTION FROM CENTRAL INDIANA
THROUGH THE KDAY VICINITY INTO SERN OHIO. MORE CONVECTION IS
MOVING NORTH OUT OF KY. ACROSS NWRN OHIO AND NWRN PA CONDITIONS
RANGE FROM MOSTLY VFR FAR EAST TO VFR/MVFR WEST AND SOUTH.
DEWPOINTS 65 TO 70 ACROSS MUCH OF THE AREA WITH LOWER 70S IN KFDY
AND UPPER 50S KERI. FOLLOWING THE HRRR HIGH RESOLUTION MODEL HAVE
KEPT PRECIP OUT OF THE AREA OVERNIGHT. BEST CHANCES HOWEVER WOULD
BE FROM KFDY TO KMFD IF THE BAND DID MANAGE TO REACH THE AREA.
MAIN CONCERN OF THE OVERNIGHT WOULD BE LOWERING CIGS AND
VISIBILITIES IN FOG AND STRATUS WITH DEEP MOISTURE ACROSS THE
AREA. DID BRING TAFS DOWN THROUGH MVFR AFTER MIDNIGHT TO MVFR/IFR
AROUND SUNRISE. AT KERI...WINDS EXPECTED TO TURN SE OVERNIGHT
WHICH WOULD BRING MORE MOISTURE INTO THE AREA SO DID BRING MVFR
CONDITIONS THERE OVERNIGHT AS WELL. ON MONDAY MODELS SHOW
CIRCULATION MOVING SE IN KY. BEST CHANCE FOR CONVECTION GETTING
INTO THE AREA WOULD BE THE SOUTH CENTRAL COUNTIES OF THE CWA. FOR
NOW BROUGHT VCTS TO THE AREA AT KMFD AND KCAK FOR THE AFTERNOON.
.OUTLOOK...NON VFR POSSIBLE MONDAY NIGHT AND TUESDAY WITH
OVERNIGHT AND EARLY MORNING FOG AS WELL AS SCATTERED TO NUMEROUS
SHOWERS/THUNDERSTORMS.
&&
.MARINE...
WINDS HAVE INCREASED TO AROUND 15 KNOTS FOR THE OPEN WATERS AND A
PORTION OF THE NEARSHORE WATERS FROM CONNEAUT TO RIPLEY. THIS HAS
CAUSED SOME LOCALLY HIGHER WAVES FOR THE ERIE AREA WITH 2 TO 4 FOOT
WAVES A DECENT BET INTO THE EVENING. WINDS SHOULD DECREASE THIS
EVENING WITH WAVES DECREASING.
OTHERWISE WE CONTINUE TO WATCH LOW PRESSURE THAT WILL TRACK ALONG
THE OHIO RIVER VALLEY INTO MONDAY NIGHT. THIS WILL KEEP AN EASTERLY
FLOW ON THE LAKE UNTIL A WEAKENING COLD FRONT PASSES ON TUESDAY.
WINDS WILL SHIFT AROUND TO THE NW AND NORTH WITH THE FRONTAL
PASSAGE. WINDS AT THIS POINT DO NOT LOOK STRONG ENOUGH TO NEED A
SMALL CRAFT ADVISORY.
HIGH PRESSURE WILL TAKE CONTROL OF LAKE ERIE TUESDAY NIGHT INTO
WEDNESDAY. A STRONGER COLD FRONT LOOKS TO ARRIVE ON THURSDAY WITH
SOME GUSTY NW WINDS POSSIBLE. THE STRONGER WINDS MAY NOT ARRIVE
UNTIL THURSDAY NIGHT AS HIGH PRESSURE BUILDS ONTO THE WESTERN END OF
THE LAKE.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
PA...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...OUDEMAN
NEAR TERM...KIELTYKA
SHORT TERM...OUDEMAN
LONG TERM...MULLEN
AVIATION...TK
MARINE...MULLEN
AREA FORECAST DISCUSSION
NWS GREENVILLE-SPARTANBURG SC
325 AM EDT MON SEP 3 2012
.SYNOPSIS...
THE CENTER OF THE REMNANTS OF ISAAC WILL CONTINUE TO MOVE SLOWLY
EASTWARD ACROSS THE OHIO VALLEY TODAY. MOISTURE OUT AHEAD OF THIS
SYSTEM WILL CONTINUE TO INCREASE ATOP THE WESTERN CAROLINAS AND
NORTHEAST GEORGIA INTO WEDNESDAY BEFORE A WEAK COLD FRONT ARRIVES
FROM THE NORTHWEST FOR THE WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 300 AM EDT...THE REMNANT CIRCULATION FROM ISAAC WAS MOVING
SLOWLY E OVER THE OH VALLEY. AS THE ASSOCIATED UPPER LOW CENTER
CONTINUES TO GRADUALLY FILL AND DRIFT EWD INTO THE APPALACHIANS...
LOBES OF VORTICITY WILL CROSS THE REGION TODAY THROUGH TONIGHT. THE
UPPER LEVEL FORCING WILL NOT BE ESPECIALLY STRONG...BUT IT SHOULD BE
PERSISTENT. MEANWHILE...LOW LEVEL FLOW WILL STRENGTHEN AND BACK
THROUGH THE MORNING HOURS. THE LATEST RUC HAS BACKED OFF ON LOW
LEVEL BULK SHEAR VALUES APPROACHING 30 KT IN THE SW MTNS THIS
MORNING...BUT THE BEST COMBINATION OF FORCING AND SHEAR SHOULD STILL
IMPACT SW SECTIONS TODAY. FORTUNATELY...SFC BASED INSTABILITY SHOULD
BE MORE LIMITED IN THIS AREA. FARTHER EAST...AN INSTABILITY GRADIENT
WILL ONCE AGAIN SET UP THROUGH THE AFTN WITH HIGHER VALUES MAINLY
EAST OF INTERSTATE 77. OVERALL INSTABILITY SHOULD BE A BIT LESS
TODAY THAN YESTERDAY GIVEN THE GREATER CLOUD COVER...BUT IT SHOULD
STILL BE SUFFICIENT FOR NUMEROUS THUNDERSTORM DEVELOPMENT WITH AN
ISOLD SEVERE WIND THREAT. A WEAK TORNADO CANNOT BE COMPLETELY RULED
OUT IN SW SECTIONS TODAY.
THE PERSISTENT SRLY UPSLOPE FLOW INTO THE SRN APPALACHIANS MAY POSE
THE GREATEST HYDRO THREAT TODAY THROUGH TONIGHT. HOWEVER...ISOLD
FLOODING WILL BE POSSIBLE JUST ABOUT ANYWHERE TRAINING CONVECTION
DEVELOPS IN THE MOIST SRLY FLOW. WILL CONTINUE TO MONITOR FOR A
POSSIBLE FLASH FLOOD WATCH AS PRECIPITABLE WATER VALUES SURGE
TO...OR REMAIN ABOVE...2 INCHES IN THE DEEPENING SRLY FLOW AND
EXPANDING WARM CLOUD DEPTH. HOWEVER...1 AND 3 HR FFG VALUES ARE
FAIRLY HIGH MOST AREAS (2 TO 3 INCHES FOR 1 HR...3 TO 4 INCHES FOR 3
HOURS). WILL HOLD OFF ON AN FFA FOR NOW UNTIL WE SEE WHICH AREAS GET
THE MOST WORKED OVER TODAY.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 215 AM EDT MONDAY...THE EXTRATROPICAL CYCLONE ASSOCIATED WITH
THE REMNANTS OF T.C. ISAAC WILL CONTINUE TO FILL DURING THE SHORT
TERM...EVENTUALLY EVOLVING INTO AN ELONGATED SHEAR AXIS. THE SHEAR
AXIS WILL CONTINUE TO WEAKEN AS IT PROGRESS SLOWLY ACROSS THE
EASTERN CONUS...BEFORE FINALLY BEING KICKED OUT BY A STRONG NORTHERN
CONUS/SOUTHERN CANADIAN SHORT WAVE TROUGH LATE IN THE WEEK. THE
UPSHOT OF THIS WILL BE THE CONTINUED PRESENCE OF A PLUME OF
EXTREMELY MOIST TROPICAL AIR OVER THE REGION. PRECIPITABLE WATERS OF
AT LEAST 2 INCHES ARE EXPECTED...WHICH IS AROUND 2 STANDARD
DEVIATIONS ABOVE THE NORM ACCORDING TO A PWAT CLIMATOLOGY FROM NWS/
WFO RAPID CITY. IN ADDITION...FORECAST SOUNDINGS DEPICT EXTREMELY
DEEP WARM CLOUD DEPTHS...UP TO IF NOT EXCEEDING 4 KM (DIFF BETWEEN
THE LCL AND THE FZL). DIURNAL HEATING OF THIS TROPICAL AIR MASS WILL
RESULT IN DEVELOPMENT OF NUMEROUS SHOWERS AND SOME THUNDERSTORMS ON
TUE AND WED. ANY CONVECTIVE CELLS THAT DEVELOP WILL BE EXTREMELY
EFFICIENT RAINFALL PRODUCERS.
OUR SAVING GRACE IS THAT MEAN WINDS IN THE CLOUD-BEARING LAYER ARE
EXPECTED TO BE IN THE 10-15 KT RANGE...SO CELLS SHOULD MOVE ALONG
RELATIVELY QUICKLY. HOWEVER...TRAINING CELLS...AND LOCALIZED FLASH
FLOODING WILL CERTAINLY BE POSSIBLE JUST ABOUT ANYWHERE. ON
TUESDAY...IT APPEARS THAT THE BEST CHANCE FOR EXCESSIVE RAINFALL AND
FLASH FLOODING WILL BE NEAR THE SOUTHERN ESCARPMENT OF THE BLUE
RIDGE...AS MODEL SOLUTIONS DEPICT A MODERATELY STRONG (FOR LATE
SUMMER) SOUTHERLY LOW LEVEL FLOW. ON WEDNESDAY...THE SHEAR AXIS WILL
PUSH INTO THE AREA...AND THE LOW LEVEL REFLECTION OF THIS FEATURE
MAY PROVIDE A FOCUS FOR TRAINING CELLS...OWING TO THE BOUNDARY-
PARALLEL NATURE OF THE MEAN WIND PROFILE. IN ADDITION...ANTECEDENT
CONDITIONS AFTER A COUPLE OF DAYS OF HEAVY RAIN WILL PROBABLY BECOME
CRITICAL IN SOME AREAS BY WEDNESDAY. IT/S JUST IMPOSSIBLE TO SAY
WHERE THESE AREAS WILL BE AT THIS POINT. REGARDLESS...IT IS LIKELY
THAT A FLASH FLOOD WATCH WILL BE ISSUED FOR A PORTION OF THE AREA BY
WEDNESDAY.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 100 AM EDT MONDAY...VERY WEAK SFC RIDGING LOOKS TO BUILD INTO
THE MTNS ON THURSDAY WHILE WEAK SFC BNDRY LINGERS ACRS THE CENTRAL
CAROLINAS. MODEL CONSENSUS IS STILL DISPLACING THE DEEPEST RH EAST
OF THE CWFA AS THE DAY WEARS ON...BUT DEVELOPING INSTABILITY WITHIN
THE UPPER DIFFLUENT FLOW SHOULD BE ENUF TO SUPPORT GOING CHANCE POP
CWFAWIDE. THE CONTINUED INFLUX OF LOWER PWAT VALUES SHOULD BE ABLE
TO LOWER PRECIP CHANCES TO LESS THAN SLIGHT AT SOME POINT THURSDAY
NIGHT.
IT STILL LOOKS LIKE A MOSTLY DRY DAY IS ON TAP FOR FRIDAY WITHIN
THE DEVELOPING WEAK S/WV RIDGING ALOFT BUT THE VERY LOW END DEEP
CONVECTIVE CHANCE WILL BE MAINTAINED ACROSS THE NC MTNS IN THE
AFTERNOON.
WITHIN THE EXPECTED AMPLIFYING PATTERN THIS WEEKEND...ANOTHER
FRONTAL SYSTEM SHOULD AFFECT THE CWFA BUT FOR NOW WILL KEEP THE
INHERITED CLIMO/HPC POPS SATURDAY WITH A LITTLE HIGHER CHANCES
FOR SUNDAY.
&&
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
AT KCLT...THE TERMINAL AREA REMAINS IN A LULL EARLY THIS MORNING AS
OVERNIGHT PIEDMONT CONVECTION IS WELL EAST OF KCLT...AND THE DEEPER
MOISTURE STILL REMAINS WEST OF THE AREA. EXPECT FLOW TO BACK SRLY
THROUGH A DEEP LAYER TODAY AND STRENGTHEN TO BRING MOISTURE BACK
RAPIDLY. THE THICKENING MID AND HIGH CLOUDS SHOULD PERMIT NO WORSE
THAN MVFR FOG AROUND DAYBREAK. PIEDMONT TSTMS ARE EXPECTED AGAIN
THIS AFTERNOON AS WARM ADVECTION FLOW INCREASES. WILL TARGET 20Z TO
00Z AS THE MOST FAVORED PERIOD FOR TSTMS...WITH SHOWERS LIKELY
OUTSIDE OF THAT PERIOD. CIG RESTRICTIONS WILL BE POSSIBLE UNDER ANY
CONVECTION...BUT EXPECT MAINLY VFR CIGS OTHERWISE. THERE WERE SOME
LOW END GUSTS YESTERDAY AND BOUNDARY LAYER WINDS WILL BE A BIT
STRONGER TODAY...SO WILL ADVERTISE G16 KT AFTER 19Z. RESTRICTIONS
WILL LIKELY BECOME MORE PERSISTENT JUST PAST THE CURRENT TAF PERIOD.
ELSEWHERE...IMPROVING SRLY UPSLOPE FLOW AND MOISTURE WILL ALLOW
SHOWERS TO BREAK OUT FIRST AROUND KAVL EARLY THIS MORNING AND SPREAD
EASTWARD THROUGH THE DAY AS THE MOISTURE DEEPENS. ANY IFR CIGS
AROUND DAYBREAK SHOULD BE CONFINED TO KAVL AND POSSIBLY KHKY. VCTS
SHOULD IMPACT KAVL SOONEST THIS MORNING...BUT WILL RESERVE TEMPO
THUNDER FOR MAINLY AFTER 18Z AT THE FOOTHILL TAF SITES. OUTSIDE OF
ANY CONVECTION...EXPECT VFR CIGS TO STEADILY LOWER...WITH MVFR CIGS
LIKELY TOWARD EVENING THROUGHOUT. EXPECT S WINDS AT 10 KT OR LESS.
THERE COULD BE A FEW LOW END GUSTS AT THE SC TAF SITES THIS AFTN.
OUTLOOK...DEEP MOISTURE WILL PERSIST ACROSS THE REGION THROUGH AT
LEAST WEDNESDAY. LOW CLOUD/FOG RESTRICTIONS WILL BECOME INCREASINGLY
WIDESPREAD AND PERSISTENT AS SHOWER COVERAGE REMAINS HIGH TUE INTO
WED. GRADUAL DRYING FROM THE WEST IS POSSIBLE THU...BUT MORE LIKELY
ON FRI.
AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE
PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE
CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)...
WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.
&&
$$
SYNOPSIS...CSH
NEAR TERM...HG
SHORT TERM...JDL
LONG TERM...CSH
AVIATION...HG
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
1000 PM CDT TUE SEP 4 2012
.DISCUSSION.../ISSUED AT 1005 PM CDT/
THUNDERSTORMS WITH SEVERE WEATHER HAVE BEEN MOVING EAST OVER AREA
THIS EVENING INCLUDING CURRENT DAMAGING WIND EVENT IN NORTHWEST IOWA
AND SOUTHWEST MINNESOTA. IF TRENDS CONTINUE AND NOTHING DEVELOPS
BEHIND THESE STORMS WE MAY BE ABLE TO CUT THEM BACK SOONER BUT FOR
NOW WILL HOLD IN.
&&
.AVIATION.../FOR THE 00Z TAF ISSUANCE/
THUNDERSTORMS WILL MOVE EAST OVER THE AREA THROUGH THIS EVENING
THOUGH THEY SHOULD BE GONE FROM TAF AREAS BY SOON AFTER 06Z. LOCAL
VISIBILITIES 3-5SM AND SURFACE WIND GUSTS OVER 25 KNOTS IN STORMS.
VFR OUTSIDE OF STORMS AS COLD FRONT MOVES EAST OF AREA...AND VFR
OVER ALL OF AREA AFTER 09Z THROUGH 06/00Z.
&&
.PREV DISCUSSION.../ISSUED AT 325 PM CDT/
DIFFUSE BOUNDARY IN NORTHWEST IOWA BEGINNING TO LIFT NORTHWARD AS A
WARM FRONT THIS AFTERNOON AS SURFACE LOW PRESSURE STRENGTHENS OVER
THE BLACK HILLS. MIXING HAS ALLOWED DEWPOINTS TO DRAMATICALLY FALL
THIS AFTERNOON ACROSS THE NORTHWESTERN TWO THIRDS OF THE CWA...WHILE
DEEPER MOISTURE HAS ALLOWED DEWPOINTS TO REMAIN IN THE 60S ACROSS
NORTHWEST IOWA. INSTABILITY CONTINUES TO INCREASE THIS
AFTERNOON...ESPECIALLY ACROSS OUR SOUTHEASTERN HALF OF THE FORECAST
AREA WHERE CAPE VALUES ARE GREATER THAN 1500 J/KG...WITH INCREASING
LAPSE RATES AND STRENGTHENING WESTERLIES BRINGING SHEAR UP AROUND 40
KT.
SO FAR...CAPPING IS PREVENTING CONVECTION FROM DEVELOPING...HOWEVER
WITH KSUX ALREADY 95/65 EXPECT THE CAPPING TO BE SURPASSED SOON.
THE HRRR AND NAM CONTINUE TO DEPICT CONVECTION MOVING NORTHEASTWARD
INTO THE MISSOURI VALLEY...EXTREME SOUTHEAST SOUTH DAKOTA AND
NORTHWEST IOWA LATE THIS AFTERNOON THROUGH THE EVENING. IF
CONVECTION DOES MANAGE TO FIRE IN THIS AREA...STORMS COULD
POTENTIALLY BECOME SEVERE WITH LARGE HAIL TO AROUND WALNUT SIZE AND
WIND GUSTS TO 70 MPH.
FURTHER WEST...HIGH BASED CUMULUS FIELD NOW MOVING INTO OUR WESTERN
BORDER. ISOLATED HIGH BASED CONVECTION WILL BE POSSIBLE IN OUR
WESTERN HALF THIS AFTERNOON AND EVENING...BUT EXPECT LITTLE TO NO
SEVERE WEATHER IN THIS AREA WITH SUCH DRY LOW AND MID LEVELS. AS THE
LOW BEGINS TRACKING EAST NORTHEAST ACROSS THE FORECAST AREA THIS
EVENING AND OVERNIGHT...THE TRAILING COLD FRONT WILL SHIFT THE
CONVECTION INTO CENTRAL AND EASTERN PORTIONS OF THE FORECAST AREA
WHERE CONDITIONS ARE MORE FAVORABLE FOR PRECIPITATION. WINDS WILL
LIKELY BECOME FAIRLY BREEZY FROM THE WEST NORTHWEST LATE TONIGHT.
LOWS TONIGHT WILL RANGE FROM THE MID 50S FAR NORTHWEST TO THE MID
60S FAR SOUTHEAST.
RELATIVELY QUIET WEATHER WITH MILDER TEMPERATURES EXPECTED FOR
WEDNESDAY AS SURFACE HIGH PRESSURE SETTLES IN BEHIND THE EXITING
SYSTEM. NORTH NORTHWEST WINDS WILL REMAIN A LITTLE BREEZY THROUGH
THE DAY...BUT SKIES WILL BE SUNNY AND HIGHS ARE EXPECTED IN THE 70S.
/
HIGH PRESSURE WILL BUILD IN OVER THE AREA FOR WEDNESDAY NIGHT. THUS
TRENDED LOWS TOWARDS THE COOLER SIDE OF GUIDANCE...GENERALLY UPPER
40S TO LOWER 50S. A MID LEVEL WAVE AND SOME CLOUD COVER MAY BEGIN
ENTERING OUR WEST BY LATE NIGHT...THUS DID NOT GO QUITE AS COOL AS I
WOULD HAVE IF COMPLETELY CLEAR SKIES WERE MORE LIKELY. MID LEVEL
FORCING OVERHEAD ON THURSDAY OUT AHEAD OF OUR NEXT WAVE...ALSO
SHOULD SEE DECENT ISENTROPIC LIFT. ATMOSPHERE WILL BE ON THE DRY
SIDE THOUGH...THUS FOLLOWED THE NAM AND GFS IDEA OF A DRY DAY.
HOWEVER SHOULD SEE AT LEAST SOME MID LEVEL CLOUD COVER...AND WITH
DECENT MID LEVEL LAPSE RATES...WOULD NOT BE SURPRISED TO SEE A FEW
ELEVATED SHOWERS AND THUNDERSTORMS. THINK THE ECMWF IS PROBABLY
OVERDOING CONVECTION THURSDAY...BUT LOW POPS MAY NEED TO BE ADDED ON
FUTURE SHIFTS IF MODELS TREND A LITTLE MOISTER IN THE MID LEVELS.
WITH UNCERTAINTY ON CLOUD COVER...FOLLOWED A BLEND OF THE COOLER MOS
AND THE WARMER BIAS CORRECTED NAM FOR HIGHS...GENERALLY MID 70S
SOUTHWEST MINNESOTA TO LOW TO MID 80S ELSEWHERE. SURFACE LOW TO OUR
WEST ON THURSDAY WILL PRODUCE BLUSTERY SOUTH SOUTHEAST WINDS WEST OF
THE JAMES RIVER...WITH GUSTS AROUND 25 TO 30 MPH POSSIBLE.
THE BETTER MOISTURE AND DEEP LAYER FORCING MOVES ACROSS THE CWA
THURSDAY NIGHT. THUS LOOKS LIKE A GOOD CHANCE OF SEEING SOME SHOWERS
IN MOST AREAS. INSTABILITY IS ON THE LOW SIDE...BUT SHOULD SEE AT
LEAST A COUPLE HUNDRED J/KG OF ELEVATED CAPE. SO THINKING WE SEE AT
LEAST SOME EMBEDDED THUNDER. WITH THE CLOUDS AND SHOWERS
AROUND...LOWS WILL STAY A BIT WARMER THAN WEDNESDAY
NIGHT...MAINLY IN THE 50S. COULD SEE SOME LINGERING SHOWERS
ACROSS NORTHWEST IOWA FRIDAY MORNING...BUT THESE SHOULD EXIT THE
AREA BY AFTERNOON AS THE TROUGH AXIS AND DEEPER MOISTURE PUSHES
EAST. EXPECT TO SEE GRADUAL CLEARING FROM NORTH TO SOUTH DURING THE
DAY. MUCH COOLER AIR WILL BE ADVECTED IN BEHIND THE FRONT FOR
FRIDAY...AND THIS COMBINED WITH THE LINGERING CLOUD COVER...SHOULD
HOLD HIGHS IN THE MID 60S TO LOWER 70S.
AS WE HEAD INTO THE WEEKEND...OUR UPPER LEVEL LOW WILL PUSH EAST AND
DIG A DEEP TROUGH INTO THE EASTERN PART OF THE COUNTRY. MEANWHILE A
STRONG RIDGE WILL BUILD INTO THE ROCKIES. OUR AREA WILL REMAIN IN
BETWEEN THE TWO MAKING TEMPERATURES A BIT TRICKY. WE WILL TEND TO
SEE A WARMING TREND INTO EARLY NEXT WEEK...BUT HOW WARM DEPENDS ON
THE STRENGTH AND POSITION OF THE ABOVE MENTIONED FEATURES. TRENDED
HIGHS A BIT ABOVE CONSENSUS SUNDAY THROUGH TUESDAY CLOSER TO THE 0Z
ECMWF AND HPC GUIDANCE. THIS GIVES 70S ON SATURDAY...AND UPPER 70S
TO MID 80S SUNDAY THROUGH TUESDAY. THE NEW 12Z ECMWF HAS TRENDED
STRONGER WITH THE RIDGE AND THUS WARMER WITH TEMPERATURES...SO WILL
HAVE TO MONITOR MODEL TRENDS THIS PERIOD. LOWS FRIDAY AND SATURDAY
NIGHT LOOK TO BE ON THE COOL SIDE...WITH LIGHT WINDS AND CLEAR SKIES
EXPECTED. LOWERED THEM A LITTLE BELOW CONSENSUS...WITH MAINLY MID
AND UPPER 40S EXPECTED. AS THE RIDGE BUILDS CLOSER...LOWS SHOULD
WARM INTO THE 50S BY SUNDAY NIGHT. LOOKS DRY SATURDAY THROUGH
TUESDAY. PROBABLY WILL SEE OUR NEXT COLD FRONT APPROACH SOMETIME
AROUND TUESDAY...HOWEVER AT THIS TIME DOES NOT UPPER TO BE MUCH
MOISTURE WITH IT. /CHENARD
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
$$
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
315 PM CDT MON SEP 3 2012
.DISCUSSION.../ISSUED AT 315 PM CDT/
LIGHT SHOWERS MAINLY CONFINED TO NORTHWEST IOWA SO FAR THIS
AFTERNOON. MID LEVEL CLOUDS ALSO DISSIPATING IN OUR WEST ALLOWING
FOR DECENT HEATING. DEWPOINTS HAVE FALLEN RAPIDLY ONCE MIXING
COMMENCED...WITH DRY AIR ALOFT. THIS WAS SHOWN WELL BY THE HRRR AND
NAM. BOTH OF THESE MODELS SHOW SOME DEWPOINT RECOVERY BY LATER THIS
AFTERNOON RIGHT AHEAD OF THE APPROACHING FRONTAL BOUNDARY. THE
QUESTION IS WHETHER THEY RECOVER ENOUGH TO HELP BREAK THE CAP. HRRR
HAS BACKED OFF SOME OF ITS EARLIER IDEA OF SCATTERED TO NUMEROUS
STORMS FORMING AS THE BOUNDARY ENTERED OUR CWA. STILL THINKING WE
POSSIBLY GET SOME ISOLATED DEVELOPMENT AFTER 4 OR 5 PM WEST OF THE
JAMES RIVER. FULL SUN COMBINED WITH CONVERGENCE ALONG THE FRONT AND
AN APPROACHING SHORTWAVE...MAY BE ENOUGH TO AT LEAST GET ISOLATED
DEVELOPMENT. CAPE COULD BE AROUND 1500 J/KG NEAR THE BOUNDARY...AND
A VEERING WIND PROFILE WITH DECENT WINDS ALOFT SHOULD RESULT IN
AROUND 40 KTS EFFECTIVE SHEAR. SO ANY STORM THAT IS ABLE TO FORM
COULD BE SEVERE...WITH STRONG WINDS AND LARGE HAIL. STORMS WOULD
MOVE EAST OR EAST SOUTHEAST...BUT THINKING MOST ACTIVITY WILL BE
DIURNALLY DRIVEN AND THUS DIE AS THE EVENING PROGRESSES. KEPT CHANCE
POPS MAINLY ALONG AND WEST OF THE JAMES RIVER....WITH SLIGHT CHANCE
THROUGH THE REST OF THE CWA...JUST IN CASE STORMS PERSIST ALONG
THERE OUTFLOW LONGER THAN EXPECTED. SKIES SHOULD CLEAR LATER
TONIGHT...WITH LOWS IN THE 50S AND 60S. COULD SEE SOME FOG
DEVELOPMENT IN THE SOUTH...ESPECIALLY WHERE RAIN HAS FALLEN TODAY IN
NORTHWEST IOWA.
TUESDAY SHOULD START MOSTLY SUNNY WITH HIGHS IN THE 80S AND 90S.
TRICKY PART OF TUESDAYS FORECAST WILL BE HOW FAR SOUTH THE BOUNDARY
MAKES IT LATE TONIGHT...AND HOW QUICKLY IT PUSHES BACK NORTH AS A
WARM FRONT TOMORROW BEFORE THE COLD FRONT PUSHES THROUGH. WITH
STABLE DRIER AIR NORTH OF THIS BOUNDARY...CONVECTION CHANCES WILL BE
CONFINED TO ALONG AND SOUTH OF IT DURING THE DAY...AS ANOTHER
SHORTWAVE PUSHES ACROSS. NAM IS THE FURTHEST SOUTH WITH THE
BOUNDARY...ONLY PUSHING AS FAR NORTH AS SPENCER TO YANKTON BY
AFTERNOON. THE GFS IS FURTHEST NORTH...WITH THE ECMWF IN BETWEEN.
NAM HAS BEEN A LITTLE TOO AGGRESSIVE WITH FRONTS...BUT GENERALLY HAS
BEEN THE BEST. THUS TEND TO THINK A SOLUTION SOMEWHERE BETWEEN THE
ECMWF AND NAM WILL BE CLOSEST. THIS WOULD GENERALLY KEEP THE
THUNDERSTORM THREAT SOUTH OF INTERSTATE 90 THROUGH 7 PM TUESDAY.
STORMS THAT DO FORM IN THE AFTERNOON WILL HAVE THE POTENTIAL OF
BEING SEVERE...WITH AROUND 2000 J/KG OF CAPE AND DEEP LAYER SHEAR OF
40 KTS. LARGE HAIL AND STRONG WINDS WILL BE POSSIBLE IN ANY STORM
THAT DOES FORM. CAP SHOULD HOLD STRONG FOR MUCH OF THE
AFTERNOON...HOWEVER CONTINUED HEATING AND THE APPROACHING WAVE
SHOULD BREAK IT AT SOME POINT EITHER LATE AFTERNOON OR EVENING.
/CHENARD
THAT APPROACHING WAVE AND FRONT SHOULD BRING MORE NUMEROUS SHOWERS
AND THUNDERSTORMS TUESDAY EVENING...MAINLY TO THE EASTERN PART OF
THE AREA WHERE MOISTURE POOLING AND INFLOW WILL BE GOOD. SYSTEM
MOVING FAST ENOUGH AND MID TO UPPER FLOW IS STRONG ENOUGH SO THAT
RAINFALL AMOUNTS SHOULD NOT BE TOO HIGH. FRONT WILL BE MOVING ACROSS
AREA WITH COOLER AIR SPREADING IN BEHIND IT...AND PRECIPITATION
DECREASING STEADILY AFTER MIDNIGHT. GUIDANCE SEEMS OK AT THIS POINT
ON COOLING FOR LOW TEMPERATURES. MOVEMENT LOOKS FAST ENOUGH TO KEEP
OUT ANY MENTION OF LINGERING SHOWERS FOR WEDNESDAY AND DRYING
CERTAINLY LOOKS STRONG...SO WE SHOULD BE HEADING TO A SUNNY/MOSTLY
SUNNY DAY WEDNESDAY AFTER MORNING CLOUDS SOUTHEAST DECREASE. LATE
THURSDAY INTO FRIDAY LOOKS LIKE ANOTHER THREAT OF SHOWERS AND STORMS
AS NEXT WAVE AND COLD FRONT IS PRECEDED BY FAVORABLY THERMAL
ADVECTION PATTERN. WILL GO WITH LOW POPS AS PER GUIDANCE FOR NOW BUT
OVERALL THREAT SEEMS A LITTLE HIGHER AND WHEN WE CAN NARROW DOWN THE
TIMING BETTER...THE POPS FOR AT LEAST PART OF THAT TIME...PERHAPS
THURSDAY NIGHT...MAY GO UP. THIS SYSTEM WILL BRING IN EVEN COOLER
AIR FOR FRIDAY AND SATURDAY. SOLIDLY DRY PATTERN WILL ALSO DEVELOP
BEHIND THIS SYSTEM...AND THE DRY PATTERN WILL REMAIN IN PLACE AS
SLOW BUT STEADY WARMING SETS IN SUNDAY AFTERNOON THROUGH MONDAY.
&&
.AVIATION.../FOR THE 18Z TAF ISSUANCE/
GENERALLY VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. THE
POTENTIAL EXISTS FOR THUNDERSTORM DEVELOPMENT THIS AFTERNOON WEST OF
THE JAMES RIVER AFTER 4 PM. ANY STORMS THAT FORM COULD PRODUCE
MVFR/IFR CONDITIONS AND ERRATIC WINDS. LOW CONFIDENCE ON WHETHER
STORMS FORM...THUS LEFT OUT OF THE TAFS FOR NOW. BEST CHANCE WOULD
BE BETWEEN 5 PM AND 7 PM AT KHON...WITH AN EVEN LOWER CHANCE IN THE
INTERSTATE 29 CORRIDOR CLOSER TO 10 PM. WITH LOW LEVEL MOISTURE
POOLING...COULD ALSO SEE SOME POCKETS OF MVFR FOG
TONIGHT...ESPECIALLY IN ANY AREAS THAT GET SOME RAIN TODAY...BUT
WILL LET FUTURE SHIFTS ADD IN IF CONFIDENCE INCREASES. /CHENARD
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
$$
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
1217 PM CDT MON SEP 3 2012
.DISCUSSION.../ISSUED AT 1120 AM CDT/
DECENT AREA OF MID LEVEL CLOUDS CURRENTLY OVER THE AREA. SEEING A
FEW LIGHT SHOWERS ACROSS THE FAR SOUTH AND WEST AT THIS TIME...AND
EVEN SOME LIGHTNING TOWARDS THE JAMES RIVER. THINKING THAT THESE MID
LEVEL CLOUDS CONTINUE TO PUSH EAST AND THIN SOME THROUGH THE
DAY...WITH MOST OF THE SHOWER ACTIVITY ENDING. THUS KEPT HIGH
TEMPERATURES AS ARE FOR NOW...BUT IF CLOUDS STICK AROUND SOME AREAS
MAY STRUGGLE TO REACH FORECASTED HIGHS. OTHER CONCERN TODAY IS
AFTERNOON CONVECTION POTENTIAL. MODEL SHOW ACTIVITY DEVELOPING ALONG
A BOUNDARY ACROSS EASTERN NEBRASKA INTO PORTIONS OF IOWA THIS
AFTERNOON. THINKING MOST OF THIS SHOULD STAY SOUTH AND EAST OF OUR
CWA...AND WITH CLOUD COVER LIMITING INSTABILITY...NOT SURE HOW
ROBUST THAT ACTIVITY WOULD BE EVEN IF IT CLIPPED OUR FAR SOUTHEAST.
OTHER AREA TO WATCH WILL BE ALONG AN APPROACHING COLD FRONT FROM THE
WEST THIS AFTERNOON. HRRR AND HIGH RES NAM HAVE CONTINUED TO SHOW
THE CAP BREAKING ALONG THIS BOUNDARY THIS AFTERNOON IN OUR
WEST...GENERALLY AFTER 4 PM. IT APPEARS LIKE DAYTIME
HEATING...COMBINED WITH LIFT ALONG THE FRONT AND SOME WEAK UPPER
LEVEL SUPPORT ARE ENOUGH FOR THE MODELS TO BREAK THE CAP. MAIN
UNCERTAINTY WILL BE HOW MUCH HEATING DOES OCCUR ALONG AND WEST OF
THE JAMES RIVER THIS AFTERNOON. HRRR BREAKS THE CAP WITH LOW TO MID
90S TEMPERATURES AND MID 50S TO AROUND 60 DEWPOINTS. LATEST VISIBLE
IMAGE DOES SHOW CLOUDS CLEARING IN THAT AREA...SO REACHING THE ABOVE
VALUES DOES SEEM POSSIBLE. STEEP LAPSE RATES SHOULD RESULT IN CAPE
AROUND 1500 J/KG JUST AHEAD OF THE AFTERNOON BOUNDARY...WITH A
DECENT VEERING WIND PROFILE RESULTING IN UP TO 40 KTS OF EFFECTIVE
SHEAR. THUS IT SEEMS REASONABLE THAT ANY STORMS THAT FORM COULD BE
SEVERE...WITH STRONG WINDS THE MAIN THREAT. ALTHOUGH GIVEN THE LAPSE
RATES AND SHEAR...SOME LARGE HAIL IS ALSO POSSIBLE. STORMS SHOULD
TEND TO WEAKEN BY THE TIME THEY REACH INTERSTATE 29...ALTHOUGH IF
STORMS ARE ABLE TO ORGANIZE ALONG THERE OUTFLOW...CAN NOT RULE OUT
THEM MAKING IT THAT FAR EAST. AGAIN...STORM INITIATION IS LOW
CONFIDENCE...BUT GIVEN HRRR AND OTHER HIGH RES MODEL
CONSISTENCY...WILL HAVE TO WATCH CLOSELY AS WE HEAD INTO THIS
AFTERNOON. /CHENARD
&&
.AVIATION.../FOR THE 18Z TAF ISSUANCE/
GENERALLY VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. THE
POTENTIAL EXISTS FOR THUNDERSTORM DEVELOPMENT THIS AFTERNOON WEST OF
THE JAMES RIVER AFTER 4 PM. ANY STORMS THAT FORM COULD PRODUCE
MVFR/IFR CONDITIONS AND ERRATIC WINDS. LOW CONFIDENCE ON WHETHER
STORMS FORM...THUS LEFT OUT OF THE TAFS FOR NOW. BEST CHANCE WOULD
BE BETWEEN 5 PM AND 7 PM AT KHON...WITH AN EVEN LOWER CHANCE IN THE
INTERSTATE 29 CORRIDOR CLOSER TO 10 PM. WITH LOW LEVEL MOISTURE
POOLING...COULD ALSO SEE SOME POCKETS OF MVFR FOG
TONIGHT...ESPECIALLY IN ANY AREAS THAT GET SOME RAIN TODAY...BUT
WILL LET FUTURE SHIFTS ADD IN IF CONFIDENCE INCREASES. /CHENARD
&&
.PREVIOUS DISCUSSION.../ISSUED AT 340 AM CDT/
WEAK SURFACE FRONT HAS STALLED ACROSS EASTERN CWA. UPPER LEVEL SHORT
WAVE ACROSS CENTRAL NEBRASKA AND MAY SPUR SOME ISOLATED SHOWER AND
THUNDERSTORM ACTIVITY AS WAVE ENCOUNTERS DEEPER MOISTURE AS IT WORKS
EAST. STILL FAR FROM A GREAT PRECIPITATION SET UP...AND BULK OF
FORCING ONLY SCRAPES THE SOUTHEASTERN CORNER OF THE FORECAST AREA.
AS SUCH...HAVE ONLY LEFT SLIGHT CHANCE POPS IN THE SOUTHEAST THROUGH
THE MORNING HOURS. MILD TEMPERATURES EXPECTED ACROSS THE AREA AGAIN
TODAY WITH 850 HPA TEMPS NEAR 20 C. FORECAST SOUNDINGS INDICATE THAT
ATMOSPHERE MAY HEAT OUT TO NEAR THE CONVECTIVE TEMP BY EARLY
AFTERNOON ACROSS CENTRAL SOUTH DAKOTA. THINK MODELS ARE OVERMIXING
SOME...BUT MAY BE CAPABLE OF A STORM OR TWO ACROSS THE WESTERN CWA
BY LATE AFTERNOON AS A WEAK BOUNDARY APPROACHES FROM THE WEST.
EXPECT CONVECTION TO DIE AWAY THROUGH THE EVENING HOURS AS
CONVECTION LOSES ITS HEATING SOURCE.
TUESDAY APPEARS TO BE THE LAST WARM DAY IN A WHILE WITH MUCH
STRONGER COLD FRONT EXPECTED TO WORK THROUGH THE AREA LATE TUESDAY
AFTERNOON INTO TUESDAY NIGHT. MUCH OF THE MIDLEVEL FORCING IS
FOCUSED ACROSS THE NORTHERN CWA...AND WITH THE LACK OF MOISTURE AM
CONCERNED PREVIOUS FORECAST WAS OVERDOING PRECIP POTENTIAL. LEFT
LIKELY MENTION IN THE NORTHEAST...BUT OTHERWISE SCALED EVERYTHING
BACK INTO THE CHANCE CATEGORY.
MUCH COOLER PATTERN SETTING UP FOR THE REMAINDER OF THE WEEK.
BREEZY NORTHWEST WINDS ARE EXPECTED ON WEDNESDAY WITH STRONG MIXING
AND DEEP NORTHWEST FLOW. A SERIES OF UPPER WAVES ARE EXPECTED TO
MOVE THROUGH THE AREA ON THURSDAY THROUGH SATURDAY...BUT WITH LACK
OF AVAILABLE MOISTURE SCALED BACK INHERITED POPS.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
$$
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
1122 AM CDT MON SEP 3 2012
.DISCUSSION.../ISSUED AT 1120 AM CDT/
DECENT AREA OF MID LEVEL CLOUDS CURRENTLY OVER THE AREA. SEEING A
FEW LIGHT SHOWERS ACROSS THE FAR SOUTH AND WEST AT THIS TIME...AND
EVEN SOME LIGHTNING TOWARDS THE JAMES RIVER. THINKING THAT THESE MID
LEVEL CLOUDS CONTINUE TO PUSH EAST AND THIN SOME THROUGH THE
DAY...WITH MOST OF THE SHOWER ACTIVITY ENDING. THUS KEPT HIGH
TEMPERATURES AS ARE FOR NOW...BUT IF CLOUDS STICK AROUND SOME AREAS
MAY STRUGGLE TO REACH FORECASTED HIGHS. OTHER CONCERN TODAY IS
AFTERNOON CONVECTION POTENTIAL. MODEL SHOW ACTIVITY DEVELOPING ALONG
A BOUNDARY ACROSS EASTERN NEBRASKA INTO PORTIONS OF IOWA THIS
AFTERNOON. THINKING MOST OF THIS SHOULD STAY SOUTH AND EAST OF OUR
CWA...AND WITH CLOUD COVER LIMITING INSTABILITY...NOT SURE HOW
ROBUST THAT ACTIVITY WOULD BE EVEN IF IT CLIPPED OUR FAR SOUTHEAST.
OTHER AREA TO WATCH WILL BE ALONG AN APPROACHING COLD FRONT FROM THE
WEST THIS AFTERNOON. HRRR AND HIGH RES NAM HAVE CONTINUED TO SHOW
THE CAP BREAKING ALONG THIS BOUNDARY THIS AFTERNOON IN OUR
WEST...GENERALLY AFTER 4 PM. IT APPEARS LIKE DAYTIME
HEATING...COMBINED WITH LIFT ALONG THE FRONT AND SOME WEAK UPPER
LEVEL SUPPORT ARE ENOUGH FOR THE MODELS TO BREAK THE CAP. MAIN
UNCERTAINTY WILL BE HOW MUCH HEATING DOES OCCUR ALONG AND WEST OF
THE JAMES RIVER THIS AFTERNOON. HRRR BREAKS THE CAP WITH LOW TO MID
90S TEMPERATURES AND MID 50S TO AROUND 60 DEWPOINTS. LATEST VISIBLE
IMAGE DOES SHOW CLOUDS CLEARING IN THAT AREA...SO REACHING THE ABOVE
VALUES DOES SEEM POSSIBLE. STEEP LAPSE RATES SHOULD RESULT IN CAPE
AROUND 1500 J/KG JUST AHEAD OF THE AFTERNOON BOUNDARY...WITH A
DECENT VEERING WIND PROFILE RESULTING IN UP TO 40 KTS OF EFFECTIVE
SHEAR. THUS IT SEEMS REASONABLE THAT ANY STORMS THAT FORM COULD BE
SEVERE...WITH STRONG WINDS THE MAIN THREAT. ALTHOUGH GIVEN THE LAPSE
RATES AND SHEAR...SOME LARGE HAIL IS ALSO POSSIBLE. STORMS SHOULD
TEND TO WEAKEN BY THE TIME THEY REACH INTERSTATE 29...ALTHOUGH IF
STORMS ARE ABLE TO ORGANIZE ALONG THERE OUTFLOW...CAN NOT RULE OUT
THEM MAKING IT THAT FAR EAST. AGAIN...STORM INITIATION IS LOW
CONFIDENCE...BUT GIVEN HRRR AND OTHER HIGH RES MODEL
CONSISTENCY...WILL HAVE TO WATCH CLOSELY AS WE HEAD INTO THIS
AFTERNOON. /CHENARD
.PREVIOUS DISCUSSION.../ISSUED AT 340 AM CDT/
WEAK SURFACE FRONT HAS STALLED ACROSS EASTERN CWA. UPPER LEVEL SHORT
WAVE ACROSS CENTRAL NEBRASKA AND MAY SPUR SOME ISOLATED SHOWER AND
THUNDERSTORM ACTIVITY AS WAVE ENCOUNTERS DEEPER MOISTURE AS IT WORKS
EAST. STILL FAR FROM A GREAT PRECIPITATION SET UP...AND BULK OF
FORCING ONLY SCRAPES THE SOUTHEASTERN CORNER OF THE FORECAST AREA.
AS SUCH...HAVE ONLY LEFT SLIGHT CHANCE POPS IN THE SOUTHEAST THROUGH
THE MORNING HOURS. MILD TEMPERATURES EXPECTED ACROSS THE AREA AGAIN
TODAY WITH 850 HPA TEMPS NEAR 20 C. FORECAST SOUNDINGS INDICATE THAT
ATMOSPHERE MAY HEAT OUT TO NEAR THE CONVECTIVE TEMP BY EARLY
AFTERNOON ACROSS CENTRAL SOUTH DAKOTA. THINK MODELS ARE OVERMIXING
SOME...BUT MAY BE CAPABLE OF A STORM OR TWO ACROSS THE WESTERN CWA
BY LATE AFTERNOON AS A WEAK BOUNDARY APPROACHES FROM THE WEST.
EXPECT CONVECTION TO DIE AWAY THROUGH THE EVENING HOURS AS
CONVECTION LOSES ITS HEATING SOURCE.
TUESDAY APPEARS TO BE THE LAST WARM DAY IN A WHILE WITH MUCH
STRONGER COLD FRONT EXPECTED TO WORK THROUGH THE AREA LATE TUESDAY
AFTERNOON INTO TUESDAY NIGHT. MUCH OF THE MIDLEVEL FORCING IS
FOCUSED ACROSS THE NORTHERN CWA...AND WITH THE LACK OF MOISTURE AM
CONCERNED PREVIOUS FORECAST WAS OVERDOING PRECIP POTENTIAL. LEFT
LIKELY MENTION IN THE NORTHEAST...BUT OTHERWISE SCALED EVERYTHING
BACK INTO THE CHANCE CATEGORY.
MUCH COOLER PATTERN SETTING UP FOR THE REMAINDER OF THE WEEK.
BREEZY NORTHWEST WINDS ARE EXPECTED ON WEDNESDAY WITH STRONG MIXING
AND DEEP NORTHWEST FLOW. A SERIES OF UPPER WAVES ARE EXPECTED TO
MOVE THROUGH THE AREA ON THURSDAY THROUGH SATURDAY...BUT WITH LACK
OF AVAILABLE MOISTURE SCALED BACK INHERITED POPS.
&&
.AVIATION.../FOR THE 12Z TAF ISSUANCE/
VFR CONDITIONS WILL PREVAIL THROUGH 12Z TUESDAY. ISOLATED
THUNDERSTORMS MAY DEVELOP WEST OF I29 AND ALSO SOUTH OF INTERSTATE
90 THROUGH THE EVENING HOURS.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
$$
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
1207 PM EDT MON SEP 3 2012
.SYNOPSIS...
THE REMNANTS OF ISAAC WILL CONTINUE TO IMPACT THE REGION TODAY
THROUGH WEDNESDAY WITH DEEP TROPICAL MOISTURE AND DAILY WIDESPREAD
SHOWERS AND THUNDERSTORMS WITH LOCALLY HEAVY RAIN. DRIER AIR WILL
FINALLY PUSH INTO THE AREA BY FRIDAY AS A SERIES OF COLD FRONTS
DROP SOUTHEAST INTO THE REGION.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 1200 PM EDT MONDAY...
HAVE ISSUED A FLASH FLOOD WATCH FOR THE AREA ROUGHLY ALONG THE
FOOTHILLS OF NC...NORTHEAST ALONG THE LEE OF THE BLUE RIDGE TO THE
ROANOKE...AND THEN EASTWARD INTO AREAS ALONG AND NEAR VA ROUTE
460. POCKETS OF THIS REGION HAVE BEEN HARDEST HIT OVER THE WEEKEND
WITH LOCALLY HEAVY RAIN FROM THUNDERSTROMS. AS SUCH...FLASH FLOOD
GUIDANCE VALUES ARE THE LOWER HERE. STORMS WITH VERY HEAVY
RAINFALL RATES ARE EXPECTED AGAIN THIS AFTERNOON AND EVENING.
LOCALIZED FLASH FLOODING MAY OCCUR WITH THESE STORMS.
AS OF 1002 AM EDT MONDAY...
EARLY MORNING PATCHY FOG HAS DISSIPATED IN MOST AREA. JUST A FEW
SMALL POCKETS REMAIN...HOWEVER THESE TOO WILL ERODE BY NOON.
PRECIPITATION ACROSS THE AREA IS MINIMAL. KFCX 88D SHOWING SOME
ISOLATED SHOWERS NEAR AND EAST OF LYNCHBURG VA...AND ALSO A FEW
MAKING THEIR WAY INTO THE NORTHERN MOUNTAINS OF NORTH CAROLINA
FROM NORTHEAST TENNESSEE. THE EXPECTATION IS FOR THIS TO BE THE
NORM THROUGH AROUND NOON. STARTING IN THE EARLY
AFTERNOON...DAYTIME HEATING WILL YIELD ANOTHER RAPID DEVELOPMENT
AND GENEROUS COVERAGE OF SHOWERS AND STORMS ACROSS THE REGION.
HAVE TWEAKED POP AND WEATHER GRIDS TO REFLECT THIS LATEST
EXPECTATION. ALSO HAVE TWEAKED HOURLY TEMPERATURE...DEW
POINT...SKY COVER AND WINDS TO REFLECT THE LATEST OBSERVATIONS AND
EXPECTED TRENDS INTO THE EARLY AFTERNOON.
AS OF 450 AM EDT MONDAY...
WATER VAPOR LOOP SHOWED UPPER LOW OVER EXTREME SOUTHWEST OHIO. AT
THE SURFACE...THE 08Z MSAS ANALYSIS HAD THE LOW OVER THE
KENTUCKY/ILLINOIS/INDIANA BORDER. ALL MODELS OPEN UP THE UPPER LOW
DURING THE NEXT 24 HOURS. SUSPECT EVEN THE SHORT RANGE GUIDANCE
MAY BE A LITTLE ON THE SLOW SIDE WITH THE EVOLUTION OF THE UPPER
SYSTEM...SINCE AN MCS OVER MISSISSIPPI AND ALABAMA MAY HAVE
ALREADY BROKEN OFF A PIECE OF VORTICITY FROM THE MAIN UPPER LOW.
THE MAIN NORTHERN PART OF THE UPPER SYSTEM IS FORECAST TO TRACK
TOWARD PENNSYLVANIA AND THE NORTHERN JET STREAM.
REGIONAL RADARS INDICATED WIDESPREAD SHOWERS AROUND THE UPPER LOW.
MODELS HAVE THIS PRECIPITATION EDGING SLOWLY EAST THIS MORNING. SO
THROUGH NOON HAVE THE HIGHER PROBABILITY OF PRECIPITATION IN THE
FAR WESTERN COUNTY WARNING AREA. EXPECT COVERAGE TO JUST BE
ISOLATED THROUGH MID MORNING FOR THE REST OF THE FORECAST AREA.
WIDESPREAD PRECIPITATION IS EXPECTED THIS AFTERNOON AND EVENING.
SREF AND LOCAL WRF ALONG WITH OTHER GUIDANCE WAS FOCUSING BEST
THREAT OF HEAVY RAIN ALONG THE SOUTHERN BLUE RIDGE...ESPECIALLY IN
THE NORTHWEST NORTH CAROLINA MOUNTAINS. GIVEN THE AIR MAS IS STILL
VERY TROPICAL WITH PRECIPITABLE WATER VALUES IN THE 1.5 TO 2.2
INCH RANGE HAVE LOCALLY HEAVY RAIN MENTIONED FOR ALL PARTS OF THE
FORECAST AREA THIS AFTERNOON AND EVENING.
FFG IS LOWEST IN THE NEW RIVER VALLEY AND ALONG THE FOOTHILLS OF
THE BLUE RIDGE FROM PATRICK AND HENRY COUNTIES DOWN TO WILKES AND
YADKIN COUNTIES. WILL CONTINUE TO ASSESS ANY FLASH FLOOD THREAT
DURING THE MORNING.
ANTICIPATE MINIMAL CHANGE IN TEMPERATURES FROM PAST FEW DAYS.
STAYED CLOSE TO PERSISTENCE FOR MAXIMUM TEMPERATURES TODAY AND
LOWS TONIGHT...WHICH ENDS UP BEING ON THE WARM SIDE OF GUIDANCE.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 254 AM EDT MONDAY...
REMNANTS OF ISAAC UPPER LEVEL TROUGH OPENS ON TUESDAY AND SLOWLY
MOVES OVER THE REGION TUESDAY AND WEDNESDAY. THE TROUGH WILL KEEP
BULK OF THE RAIN OVER THE MOUNTAINS TUESDAY AFTERNOON THEN ALONG THE
BLUE RIDGE AND FOOTHILL COUNTIES TUESDAY EVENING. TUESDAY LOOKS TO
BE THE BETTER DAY FOR SEVERE WEATHER WITH A LOW LEVEL JET CROSSING
THE REGION. CAN NOT RULE OUT STRONG TO SEVERE STORMS WITH A FEW
SUPERCELLS TRACKING ACROSS THE AREA. MOVEMENT OF THESE STORMS WILL
BE RELATIVELY SLOW AND AROUND 20-30 MPH. STRONG TO SEVERE STORMS
WILL BE HIGHLY DEPENDENT ON HEATING THROUGH THE DAY.
THE UPPER LEVEL TROUGH WILL MOVE TO THE BLUE RIDGE WEDNESDAY WITH A
LINE OF SHOWERS STARTING NEAR THE BLUE RIDGE IN THE
AFTERNOON...MOVING EAST INTO THE PIEDMONT IN THE EVENING. STRONG TO
SEVERE STORMS ARE POSSIBLE BUT THE BIGGER THREAT WILL BE EAST OF THE
AREA AND ACROSS THE COASTAL PIEDMONT OF THE MID ATLANTIC REGION.
WEAK HIGH PRESSURE BUILDS IN WEDNESDAY...PUSHING THE TROPICAL AIR MASS
OFF TO THE EAST.
AFTERNOON TEMPERATURES WILL BE NEAR NORMAL TUESDAY AND WEDNESDAY
WHILE OVERNIGHTS CONTINUE TO BE MUGGY AND ABOVE NORMAL.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 1230 PM EDT SUNDAY...
DEEP TROPICAL MOISTURE ASSOCIATED WITH THE REMNANT OF ISAAC WILL
FINALLY GET BOOTED SE DURING THURSDAY AHEAD OF AN INITIAL WEAK COLD
FRONT THAT WILL DROPPING SE IN ADVANCE OF A DEVELOPING ERN 5H TROF.
HOWEVER STILL ENOUGH LIFT WITH THE RESIDUAL SHEAR AXIS AND WEAK
SURFACE TROF TO PROMPT ADDITIONAL SHRA WED NIGHT WITH PERHAPS YET
ANOTHER ORGANIZED BAND ESPCLY EAST ON THURSDAY. THUS KEPT IN HIGH
CHANCE POPS INTO THURSDAY WHICH MAY NEED TO GO HIGHER IN LATER
UPDATES. BOUNDARY MAY TEND TO EDGE SOUTH OF THE AREA DURING FRIDAY
BEFORE THE FLOW STARTS TO BACK AGAIN AHEAD OF A MORE POTENT WAVE
ROUNDING THRU THE GREAT LAKES COLD POOL SAT.
THIS FEATURE SHOULD PUSH A STRONGER SECONDARY COLD FRONT TOWARD
THE APPALACHIANS SAT NIGHT INTO SUNDAY WITH A ANOTHER ROUND OF
SHRA/TSRA AS DEEPER MOISTURE MAKES A QUICK RETURN. JUST HOW FAST
THE FRONT MOVES EAST IFFY GIVEN HINT OF A 5H CUTOFF DEVELOPING
OVER THE OHIO VALLEY BY SUNDAY SO FOLLOWING A BIT OF A BLEND GIVEN
UNCERTAINTY NEXT WEEKEND.
OTRW APPEARS ENOUGH DRYING TO BASICALLY CUT POPS LATER THU NIGHT
THRU FRIDAY NIGHT...THEN RETURNING TO CHANCE COVERAGE FROM WEST TO
EAST LATER SATURDAY THRU SUNDAY. TEMPS TO REMAIN WARM/MUGGY THU
WITH HIGHS MOSTLY IN THE 80S INTO FRIDAY ALTHOUGH A BIT LESS
HUMID. MAY SEE THINGS COOL OFF SOME WITH SHRA SAT BUT MORE SO
SUNDAY PENDING THE FRONTAL TIMING WITH HIGHS LOW/MID 70S WEST AND
LOW 80S EAST.
&&
.AVIATION /16Z MONDAY THROUGH FRIDAY/...
AS OF 740 AM EDT MONDAY...
MID LEVEL CLOUDS WILL LIMIT THE EXTENT OF FOG THIS MORNING...BUT
STRATUS WITH IFR CEILINGS DEVELOPED OVERNIGHT ACROSS THE REGION.
EXPECT CEILINGS TO LIFT TO MVFR BY 15Z/11AM THEN VFR BY 17Z/1PM.
HAVE USED THE LOCAL WRF AND HRRR FOR TIMING OF WHEN THUNDERSTORMS
WILL DEVELOP THIS AFTERNOON. THESE MODELS HAVE STORMS INITIALLY DEVELOPING
BETWEEN 19Z/3PM AND 21Z/5PM. NUMEROUS THUNDERSTORMS WILL CONTINUE
INTO THE EVENING...THEN COVERAGE WILL DIMINISH AFTER 00Z/8PM. VERY
HEAVY RAIN IS LIKELY WITH ANY OF THE STRONGER STORMS WHICH WILL
RESULT IN MVFR TO IFR VISIBILITIES.
TROPICAL PATTERN WILL CONTINUE THROUGH THURSDAY WITH THE REMNANTS
OF ISAAC SLOWLY APPROACHING THE AREA. ANTICIPATE PRIMARILY VFR
CONDITIONS WITH BRIEF IFR/MVFR CONDITIONS UNDER ANY STRONGER
SHOWERS OR STORMS. LATE NIGHT AND EARLY MORNING IFR/MVFR MOUNTAIN
AND RIVER VALLEY FOG IS ALSO EXPECTED.
BY THURSDAY NIGHT INTO EARLY FRIDAY...A COLD FRONT WILL SWEEP
THROUGH THE AREA WITH A SURGE OF DRIER AIR BEHIND IT BY FRIDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...FLASH FLOOD WATCH UNTIL MIDNIGHT EDT TONIGHT FOR VAZ013-014-
016-017-022-032>035-043-045>047.
NC...FLASH FLOOD WATCH UNTIL MIDNIGHT EDT TONIGHT FOR NCZ003>005-
019-020.
WV...NONE.
&&
$$
SYNOPSIS...AMS
NEAR TERM...AMS/DS
SHORT TERM...RCS
LONG TERM...JH
AVIATION...AMS/KM
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
1007 AM EDT MON SEP 3 2012
.SYNOPSIS...
THE REMNANTS OF ISAAC WILL CONTINUE TO IMPACT THE REGION TODAY
THROUGH WEDNESDAY WITH DEEP TROPICAL MOISTURE AND DAILY WIDESPREAD
SHOWERS AND THUNDERSTORMS WITH LOCALLY HEAVY RAIN. DRIER AIR WILL
FINALLY PUSH INTO THE AREA BY FRIDAY AS A SERIES OF COLD FRONTS
DROP SOUTHEAST INTO THE REGION.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 1002 AM EDT MONDAY...
EARLY MORNING PATCHY FOG HAS DISSIPATED IN MOST AREA. JUST A FEW
SMALL POCKETS REMAIN...HOWEVER THESE TOO WILL ERODE BY NOON.
PRECIPITATION ACROSS THE AREA IS MINIMAL. KFCX 88D SHOWING SOME
ISOLATED SHOWERS NEAR AND EAST OF LYNCHBURG VA...AND ALSO A FEW
MAKING THEIR WAY INTO THE NORTHERN MOUNTAINS OF NORTH CAROLINA
FROM NORTHEAST TENNESSEE. THE EXPECTATION IS FOR THIS TO BE THE
NORM THROUGH AROUND NOON. STARTING IN THE EARLY
AFTERNOON...DAYTIME HEATING WILL YIELD ANOTHER RAPID DEVELOPMENT
AND GENEROUS COVERAGE OF SHOWERS AND STORMS ACROSS THE REGION.
HAVE TWEAKED POP AND WEATHER GRIDS TO REFLECT THIS LATEST
EXPECTATION. ALSO HAVE TWEAKED HOURLY TEMPERATURE...DEW
POINT...SKY COVER AND WINDS TO REFLECT THE LATEST OBSERVATIONS AND
EXPECTED TRENDS INTO THE EARLY AFTERNOON.
AS OF 450 AM EDT MONDAY...
WATER VAPOR LOOP SHOWED UPPER LOW OVER EXTREME SOUTHWEST OHIO. AT
THE SURFACE...THE 08Z MSAS ANALYSIS HAD THE LOW OVER THE
KENTUCKY/ILLINOIS/INDIANA BORDER. ALL MODELS OPEN UP THE UPPER LOW
DURING THE NEXT 24 HOURS. SUSPECT EVEN THE SHORT RANGE GUIDANCE
MAY BE A LITTLE ON THE SLOW SIDE WITH THE EVOLUTION OF THE UPPER
SYSTEM...SINCE AN MCS OVER MISSISSIPPI AND ALABAMA MAY HAVE
ALREADY BROKEN OFF A PIECE OF VORTICITY FROM THE MAIN UPPER LOW.
THE MAIN NORTHERN PART OF THE UPPER SYSTEM IS FORECAST TO TRACK
TOWARD PENNSYLVANIA AND THE NORTHERN JET STREAM.
REGIONAL RADARS INDICATED WIDESPREAD SHOWERS AROUND THE UPPER LOW.
MODELS HAVE THIS PRECIPITATION EDGING SLOWLY EAST THIS MORNING. SO
THROUGH NOON HAVE THE HIGHER PROBABILITY OF PRECIPITATION IN THE
FAR WESTERN COUNTY WARNING AREA. EXPECT COVERAGE TO JUST BE
ISOLATED THROUGH MID MORNING FOR THE REST OF THE FORECAST AREA.
WIDESPREAD PRECIPITATION IS EXPECTED THIS AFTERNOON AND EVENING.
SREF AND LOCAL WRF ALONG WITH OTHER GUIDANCE WAS FOCUSING BEST
THREAT OF HEAVY RAIN ALONG THE SOUTHERN BLUE RIDGE...ESPECIALLY IN
THE NORTHWEST NORTH CAROLINA MOUNTAINS. GIVEN THE AIR MAS IS STILL
VERY TROPICAL WITH PRECIPITABLE WATER VALUES IN THE 1.5 TO 2.2
INCH RANGE HAVE LOCALLY HEAVY RAIN MENTIONED FOR ALL PARTS OF THE
FORECAST AREA THIS AFTERNOON AND EVENING.
FFG IS LOWEST IN THE NEW RIVER VALLEY AND ALONG THE FOOTHILLS OF
THE BLUE RIDGE FROM PATRICK AND HENRY COUNTIES DOWN TO WILKES AND
YADKIN COUNTIES. WILL CONTINUE TO ASSESS ANY FLASH FLOOD THREAT
DURING THE MORNING.
ANTICIPATE MINIMAL CHANGE IN TEMPERATURES FROM PAST FEW DAYS.
STAYED CLOSE TO PERSISTENCE FOR MAXIMUM TEMPERATURES TODAY AND
LOWS TONIGHT...WHICH ENDS UP BEING ON THE WARM SIDE OF GUIDANCE.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 254 AM EDT MONDAY...
REMNANTS OF ISAAC UPPER LEVEL TROUGH OPENS ON TUESDAY AND SLOWLY
MOVES OVER THE REGION TUESDAY AND WEDNESDAY. THE TROUGH WILL KEEP
BULK OF THE RAIN OVER THE MOUNTAINS TUESDAY AFTERNOON THEN ALONG THE
BLUE RIDGE AND FOOTHILL COUNTIES TUESDAY EVENING. TUESDAY LOOKS TO
BE THE BETTER DAY FOR SEVERE WEATHER WITH A LOW LEVEL JET CROSSING
THE REGION. CAN NOT RULE OUT STRONG TO SEVERE STORMS WITH A FEW
SUPERCELLS TRACKING ACROSS THE AREA. MOVEMENT OF THESE STORMS WILL
BE RELATIVELY SLOW AND AROUND 20-30 MPH. STRONG TO SEVERE STORMS
WILL BE HIGHLY DEPENDENT ON HEATING THROUGH THE DAY.
THE UPPER LEVEL TROUGH WILL MOVE TO THE BLUE RIDGE WEDNESDAY WITH A
LINE OF SHOWERS STARTING NEAR THE BLUE RIDGE IN THE
AFTERNOON...MOVING EAST INTO THE PIEDMONT IN THE EVENING. STRONG TO
SEVERE STORMS ARE POSSIBLE BUT THE BIGGER THREAT WILL BE EAST OF THE
AREA AND ACROSS THE COASTAL PIEDMONT OF THE MID ATLANTIC REGION.
WEAK HIGH PRESSURE BUILDS IN WEDNESDAY...PUSHING THE TROPICAL AIR MASS
OFF TO THE EAST.
AFTERNOON TEMPERATURES WILL BE NEAR NORMAL TUESDAY AND WEDNESDAY
WHILE OVERNIGHTS CONTINUE TO BE MUGGY AND ABOVE NORMAL.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 1230 PM EDT SUNDAY...
DEEP TROPICAL MOISTURE ASSOCIATED WITH THE REMNANT OF ISAAC WILL
FINALLY GET BOOTED SE DURING THURSDAY AHEAD OF AN INITIAL WEAK COLD
FRONT THAT WILL DROPPING SE IN ADVANCE OF A DEVELOPING ERN 5H TROF.
HOWEVER STILL ENOUGH LIFT WITH THE RESIDUAL SHEAR AXIS AND WEAK
SURFACE TROF TO PROMPT ADDITIONAL SHRA WED NIGHT WITH PERHAPS YET
ANOTHER ORGANIZED BAND ESPCLY EAST ON THURSDAY. THUS KEPT IN HIGH
CHANCE POPS INTO THURSDAY WHICH MAY NEED TO GO HIGHER IN LATER
UPDATES. BOUNDARY MAY TEND TO EDGE SOUTH OF THE AREA DURING FRIDAY
BEFORE THE FLOW STARTS TO BACK AGAIN AHEAD OF A MORE POTENT WAVE
ROUNDING THRU THE GREAT LAKES COLD POOL SAT.
THIS FEATURE SHOULD PUSH A STRONGER SECONDARY COLD FRONT TOWARD
THE APPALACHIANS SAT NIGHT INTO SUNDAY WITH A ANOTHER ROUND OF
SHRA/TSRA AS DEEPER MOISTURE MAKES A QUICK RETURN. JUST HOW FAST
THE FRONT MOVES EAST IFFY GIVEN HINT OF A 5H CUTOFF DEVELOPING
OVER THE OHIO VALLEY BY SUNDAY SO FOLLOWING A BIT OF A BLEND GIVEN
UNCERTAINTY NEXT WEEKEND.
OTRW APPEARS ENOUGH DRYING TO BASICALLY CUT POPS LATER THU NIGHT
THRU FRIDAY NIGHT...THEN RETURNING TO CHANCE COVERAGE FROM WEST TO
EAST LATER SATURDAY THRU SUNDAY. TEMPS TO REMAIN WARM/MUGGY THU
WITH HIGHS MOSTLY IN THE 80S INTO FRIDAY ALTHOUGH A BIT LESS
HUMID. MAY SEE THINGS COOL OFF SOME WITH SHRA SAT BUT MORE SO
SUNDAY PENDING THE FRONTAL TIMING WITH HIGHS LOW/MID 70S WEST AND
LOW 80S EAST.
&&
.AVIATION /14Z MONDAY THROUGH FRIDAY/...
AS OF 740 AM EDT MONDAY...
MID LEVEL CLOUDS WILL LIMIT THE EXTENT OF FOG THIS MORNING...BUT
STRATUS WITH IFR CEILINGS DEVELOPED OVERNIGHT ACROSS THE REGION.
EXPECT CEILINGS TO LIFT TO MVFR BY 15Z/11AM THEN VFR BY 17Z/1PM.
HAVE USED THE LOCAL WRF AND HRRR FOR TIMING OF WHEN THUNDERSTORMS
WILL DEVELOP THIS AFTERNOON. THESE MODELS HAVE STORMS INITIALLY DEVELOPING
BETWEEN 19Z/3PM AND 21Z/5PM. NUMEROUS THUNDERSTORMS WILL CONTINUE
INTO THE EVENING...THEN COVERAGE WILL DIMINISH AFTER 00Z/8PM. VERY
HEAVY RAIN IS LIKELY WITH ANY OF THE STRONGER STORMS WHICH WILL
RESULT IN MVFR TO IFR VISIBILITIES.
TROPICAL PATTERN WILL CONTINUE THROUGH THURSDAY WITH THE REMNANTS
OF ISAAC SLOWLY APPROACHING THE AREA. ANTICIPATE PRIMARILY VFR
CONDITIONS WITH BRIEF IFR/MVFR CONDITIONS UNDER ANY STRONGER
SHOWERS OR STORMS. LATE NIGHT AND EARLY MORNING IFR/MVFR MOUNTAIN
AND RIVER VALLEY FOG IS ALSO EXPECTED.
BY THURSDAY NIGHT INTO EARLY FRIDAY...A COLD FRONT WILL SWEEP
THROUGH THE AREA WITH A SURGE OF DRIER AIR BEHIND IT BY FRIDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...AMS
NEAR TERM...AMS/DS
SHORT TERM...RCS
LONG TERM...JH
AVIATION...AMS/KM
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
748 AM EDT MON SEP 3 2012
.SYNOPSIS...
THE REMNANTS OF ISAAC WILL CONTINUE TO IMPACT THE REGION TODAY
THROUGH WEDNESDAY WITH DEEP TROPICAL MOISTURE AND DAILY WIDESPREAD
SHOWERS AND THUNDERSTORMS WITH LOCALLY HEAVY RAIN. DRIER AIR WILL
FINALLY PUSH INTO THE AREA BY FRIDAY AS A SERIES OF COLD FRONTS
DROP SOUTHEAST INTO THE REGION.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 450 AM EDT MONDAY...
WATER VAPOR LOOP SHOWED UPPER LOW OVER EXTREME SOUTHWEST OHIO. AT
THE SURFACE...THE 08Z MSAS ANALYSIS HAD THE LOW OVER THE
KENTUCKY/ILLINOIS/INDIANA BORDER. ALL MODELS OPEN UP THE UPPER LOW
DURING THE NEXT 24 HOURS. SUSPECT EVEN THE SHORT RANGE GUIDANCE
MAY BE A LITTLE ON THE SLOW SIDE WITH THE EVOLUTION OF THE UPPER
SYSTEM...SINCE AN MCS OVER MISSISSIPPI AND ALABAMA MAY HAVE
ALREADY BROKEN OFF A PIECE OF VORTICITY FROM THE MAIN UPPER LOW.
THE MAIN NORTHERN PART OF THE UPPER SYSTEM IS FORECAST TO TRACK
TOWARD PENNSYLVANIA AND THE NORTHERN JET STREAM.
REGIONAL RADARS INDICATED WIDESPREAD SHOWERS AROUND THE UPPER LOW.
MODELS HAVE THIS PRECIPITATION EDGING SLOWLY EAST THIS MORNING. SO
THROUGH NOON HAVE THE HIGHER PROBABILITY OF PRECIPITATION IN THE
FAR WESTERN COUNTY WARNING AREA. EXPECT COVERAGE TO JUST BE
ISOLATED THROUGH MID MORNING FOR THE REST OF THE FORECAST AREA.
WIDESPREAD PRECIPITATION IS EXPECTED THIS AFTERNOON AND EVENING.
SREF AND LOCAL WRF ALONG WITH OTHER GUIDANCE WAS FOCUSING BEST
THREAT OF HEAVY RAIN ALONG THE SOUTHERN BLUE RIDGE...ESPECIALLY IN
THE NORTHWEST NORTH CAROLINA MOUNTAINS. GIVEN THE AIR MAS IS STILL
VERY TROPICAL WITH PRECIPITABLE WATER VALUES IN THE 1.5 TO 2.2
INCH RANGE HAVE LOCALLY HEAVY RAIN MENTIONED FOR ALL PARTS OF THE
FORECAST AREA THIS AFTERNOON AND EVENING.
FFG IS LOWEST IN THE NEW RIVER VALLEY AND ALONG THE FOOTHILLS OF
THE BLUE RIDGE FROM PATRICK AND HENRY COUNTIES DOWN TO WILKES AND
YADKIN COUNTIES. WILL CONTINUE TO ASSESS ANY FLASH FLOOD THREAT
DURING THE MORNING.
ANTICIPATE MINIMAL CHANGE IN TEMPERATURES FROM PAST FEW DAYS.
STAYED CLOSE TO PERSISTENCE FOR MAXIMUM TEMPERATURES TODAY AND
LOWS TONIGHT...WHICH ENDS UP BEING ON THE WARM SIDE OF GUIDANCE.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 254 AM EDT MONDAY...
REMNANTS OF ISAAC UPPER LEVEL TROUGH OPENS ON TUESDAY AND SLOWLY
MOVES OVER THE REGION TUESDAY AND WEDNESDAY. THE TROUGH WILL KEEP
BULK OF THE RAIN OVER THE MOUNTAINS TUESDAY AFTERNOON THEN ALONG THE
BLUE RIDGE AND FOOTHILL COUNTIES TUESDAY EVENING. TUESDAY LOOKS TO
BE THE BETTER DAY FOR SEVERE WEATHER WITH A LOW LEVEL JET CROSSING
THE REGION. CAN NOT RULE OUT STRONG TO SEVERE STORMS WITH A FEW
SUPERCELLS TRACKING ACROSS THE AREA. MOVEMENT OF THESE STORMS WILL
BE RELATIVELY SLOW AND AROUND 20-30 MPH. STRONG TO SEVERE STORMS
WILL BE HIGHLY DEPENDENT ON HEATING THROUGH THE DAY.
THE UPPER LEVEL TROUGH WILL MOVE TO THE BLUE RIDGE WEDNESDAY WITH A
LINE OF SHOWERS STARTING NEAR THE BLUE RIDGE IN THE
AFTERNOON...MOVING EAST INTO THE PIEDMONT IN THE EVENING. STRONG TO
SEVERE STORMS ARE POSSIBLE BUT THE BIGGER THREAT WILL BE EAST OF THE
AREA AND ACROSS THE COASTAL PIEDMONT OF THE MID ATLANTIC REGION.
WEAK HIGH PRESSURE BUILDS IN WEDNESDAY...PUSHING THE TROPICAL AIR MASS
OFF TO THE EAST.
AFTERNOON TEMPERATURES WILL BE NEAR NORMAL TUESDAY AND WEDNESDAY
WHILE OVERNIGHTS CONTINUE TO BE MUGGY AND ABOVE NORMAL.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 1230 PM EDT SUNDAY...
DEEP TROPICAL MOISTURE ASSOCIATED WITH THE REMNANT OF ISAAC WILL
FINALLY GET BOOTED SE DURING THURSDAY AHEAD OF AN INITIAL WEAK COLD
FRONT THAT WILL DROPPING SE IN ADVANCE OF A DEVELOPING ERN 5H TROF.
HOWEVER STILL ENOUGH LIFT WITH THE RESIDUAL SHEAR AXIS AND WEAK
SURFACE TROF TO PROMPT ADDITIONAL SHRA WED NIGHT WITH PERHAPS YET
ANOTHER ORGANIZED BAND ESPCLY EAST ON THURSDAY. THUS KEPT IN HIGH
CHANCE POPS INTO THURSDAY WHICH MAY NEED TO GO HIGHER IN LATER
UPDATES. BOUNDARY MAY TEND TO EDGE SOUTH OF THE AREA DURING FRIDAY
BEFORE THE FLOW STARTS TO BACK AGAIN AHEAD OF A MORE POTENT WAVE
ROUNDING THRU THE GREAT LAKES COLD POOL SAT.
THIS FEATURE SHOULD PUSH A STRONGER SECONDARY COLD FRONT TOWARD
THE APPALACHIANS SAT NIGHT INTO SUNDAY WITH A ANOTHER ROUND OF
SHRA/TSRA AS DEEPER MOISTURE MAKES A QUICK RETURN. JUST HOW FAST
THE FRONT MOVES EAST IFFY GIVEN HINT OF A 5H CUTOFF DEVELOPING
OVER THE OHIO VALLEY BY SUNDAY SO FOLLOWING A BIT OF A BLEND GIVEN
UNCERTAINTY NEXT WEEKEND.
OTRW APPEARS ENOUGH DRYING TO BASICALLY CUT POPS LATER THU NIGHT
THRU FRIDAY NIGHT...THEN RETURNING TO CHANCE COVERAGE FROM WEST TO
EAST LATER SATURDAY THRU SUNDAY. TEMPS TO REMAIN WARM/MUGGY THU
WITH HIGHS MOSTLY IN THE 80S INTO FRIDAY ALTHOUGH A BIT LESS
HUMID. MAY SEE THINGS COOL OFF SOME WITH SHRA SAT BUT MORE SO
SUNDAY PENDING THE FRONTAL TIMING WITH HIGHS LOW/MID 70S WEST AND
LOW 80S EAST.
&&
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
AS OF 740 AM EDT MONDAY...
MID LEVEL CLOUDS WILL LIMIT THE EXTENT OF FOG THIS MORNING...BUT
STRATUS WITH IFR CEILINGS DEVELOPED OVERNIGHT ACROSS THE REGION.
EXPECT CEILINGS TO LIFT TO MVFR BY 15Z/11AM THEN VFR BY 17Z/1PM.
HAVE USED THE LOCAL WRF AND HRRR FOR TIMING OF WHEN THUNDERSTORMS
WILL DEVELOP THIS AFTERNOON. THESE MODELS HAVE STORMS INITIALLY DEVELOPING
BETWEEN 19Z/3PM AND 21Z/5PM. NUMEROUS THUNDERSTORMS WILL CONTINUE
INTO THE EVENING...THEN COVERAGE WILL DIMINISH AFTER 00Z/8PM. VERY
HEAVY RAIN IS LIKELY WITH ANY OF THE STRONGER STORMS WHICH WILL
RESULT IN MVFR TO IFR VISIBILITIES.
TROPICAL PATTERN WILL CONTINUE THROUGH THURSDAY WITH THE REMNANTS
OF ISAAC SLOWLY APPROACHING THE AREA. ANTICIPATE PRIMARILY VFR
CONDITIONS WITH BRIEF IFR/MVFR CONDITIONS UNDER ANY STRONGER
SHOWERS OR STORMS. LATE NIGHT AND EARLY MORNING IFR/MVFR MOUNTAIN
AND RIVER VALLEY FOG IS ALSO EXPECTED.
BY THURSDAY NIGHT INTO EARLY FRIDAY...A COLD FRONT WILL SWEEP
THROUGH THE AREA WITH A SURGE OF DRIER AIR BEHIND IT BY FRIDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...AMS
NEAR TERM...AMS
SHORT TERM...RCS
LONG TERM...JH
AVIATION...AMS/KM
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
637 PM CDT TUE SEP 4 2012
.SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT
256 PM CDT TUE SEP 4 2012
MAIN FORECAST CONCERNS ARE ON CONVECTION THROUGH WEDNESDAY MORNING
AND ASSOCIATED SEVERE WEATHER POTENTIAL.
CURRENTLY AS OF 20Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED A POTENT SHORTWAVE TROUGH OVER SOUTHERN SASKATCHEWAN INTO
EASTERN MONTANA...THEN NEAR ZONAL TO SLIGHT SOUTHWEST FLOW STREAMING
EAST INTO NEW ENGLAND. WITHIN THIS FLOW...A SHORTWAVE WAS PRESENT
OVER FAR WESTERN WISCONSIN...WITH SOME WEAK RIDGING RIGHT BEHIND IT
OVER MINNESOTA. MOSTLY SUNNY SKIES AFTER THE FOG BURNED OFF THIS
MORNING HAS ALLOWED FOR STRONG HEATING ACROSS THE AREA. WITH 12Z
RAOBS HAVING 850MB TEMPS AROUND 18C...TEMPERATURES HAVE CLIMBED INTO
THE MID TO UPPER 80S. DEWPOINTS REMAIN MUGGY FOR THIS TIME OF
YEAR...IN THE MID 60S TO AROUND 70. THE COMBINATION OF THE
TEMPERATURES AND DEWPOINTS HAS RESULTED IN MLCAPE VALUES OF
2000-3000 J/KG WITH LITTLE CIN. AT THE SURFACE...LOW PRESSURE WAS
NEAR AITKIN MN WITH A DRY-LINE ARCING THROUGH NORTHWEST WI INTO
SOUTHEAST MN. PLENTY OF CUMULUS GOING UP AHEAD OF THIS DRY LINE.
STORMS ARE EXPECTED TO DEVELOP IN THE NEXT HOUR OR TWO OUT OF THIS
CUMULUS FIELD. BIG CONCERN FOR SEVERE WEATHER IS WIND GIVEN
MID-LEVEL DRY AIR PRESENT...SEEN ON BOTH WATER VAPOR AND THE 12Z MPX
SOUNDING. TO THE WEST...FAIRLY QUIET ACROSS THE DAKOTAS AHEAD OF
THE POTENT TROUGH. HOWEVER...ANOTHER SURFACE LOW HAS DEVELOPED AHEAD
OF IT NEAR PIERRE. IN ADDITION... GOES PRECIPITABLE WATER IMAGERY
SHOWS MOISTURE BEGINNING TO SURGE TO THE NORTHWEST THROUGH EASTERN
NEBRASKA AHEAD OF THE SURFACE LOW/UPPER TROUGH.
REST OF THE AFTERNOON...ASSUMING CONVECTION FIRES IN THE CUMULUS
FIELD...WHICH IS INDICATED BY MANY MESO-MODELS...EXPECTING IT TO
PROPAGATE EAST-SOUTHEAST QUICKLY DURING THE NEXT FEW HOURS. THIS IS
DUE TO THE DRY MID LEVEL AIR ALLOWING FOR RAPID MOVING OUTFLOW AS
WELL AS THE MAIN SHORTWAVE ACCOMPANYING IT SHIFTING INTO EASTERN
WISCONSIN BY 00Z. THEREFORE...THINKING THE SEVERE THREAT AND
PROBABLY MUCH OF THE PRECIPITATION WILL END BY 00Z. ONLY CAVEAT
COULD BE IN FAR SOUTHWEST WI AND FAR NORTHEAST IA WHERE THERE ARE
HINTS THE TAIL END OF CONVECTION COULD STALL OUT. KEPT SOME HIGHER
CHANCES OF PRECIPITATION DOWN THERE JUST IN CASE.
TONIGHT AND WEDNESDAY...THE POTENT SHORTWAVE OVER EASTERN MONTANA IS
FORECAST TO MOVE INTO WESTERN MINNESOTA BY 12Z WEDNESDAY. AS THIS
OCCURS...THE MOISTURE SEEN LIFTING UP THROUGH EASTERN NEBRASKA RIGHT
NOW IS GOING TO GET ISENTROPICALLY LIFTED UP TOWARDS US. SO AFTER
SOME BRIEF SHORTWAVE RIDGING AND SUBSIDENCE THIS EVENING...ANOTHER
ROUND OF SHOWERS AND THUNDERSTORMS LOOKS LIKELY. DEVELOPMENT MAY
OCCUR SOUTH OF I-90 AS EARLY AS 03Z AS SUGGESTED BY THE 04.12Z
NAM/GFS. BETTER POTENTIAL FOR PRECIPITATION FOR THE ENTIRE AREA IS
AFTER MIDNIGHT AS THE SHORTWAVE APPROACHES AND 850MB MOISTURE
TRANSPORT REALLY INCREASES. MID-LEVEL FLOW IS NICELY DIFFLUENT TOO
AHEAD OF THE WAVE...AIDING IN FORCING. MCS DEVELOPMENT IS CERTAINLY
POSSIBLE...AS NOTED BY THE 04.12Z ECMWF/UKMET/CANADIAN/NAM.
REGARDING SEVERE CONCERN...1-6KM SHEAR VALUES VARY FROM MODEL TO
MODEL. NAM IS ON THE ORDER OF 30-40 KT WHILE THE GFS IS 20-30KT. THE
NAM WOULD DEFINITELY GIVE A SEVERE WEATHER CONCERN...WITH BOTH HAIL
AND DAMAGING WINDS POSSIBLE. THE GFS NOT AS MUCH SO. THEREFORE...
THINK THE SPCS DAY 1 OUTLOOK SLIGHT RISK IDEA IS APPROPRIATE. A BIG
NOTE...THERE IS A POSSIBILITY MCS DEVELOPMENT COULD OCCUR FARTHER
SOUTH SAY MORE OVER IOWA. IF IT DOES...CORFIDI VECTORS WOULD TAKE IT
SOUTHEAST...LIMITING SOME OF THE CONVECTIVE ACTIVITY OVER THE
FORECAST AREA. SHORTWAVE TROUGH IS PROGGED TO HEAD EAST TO CENTRAL
UPPER MICHIGAN AND LAKE MICHIGAN BY 18Z...ALLOWING STRONG ISENTROPIC
DESCENT TO FILTER INTO THE AREA AND CLEAR OUT THE
PRECIPITATION/CLOUDS. COLD FRONTAL BOUNDARY TOO LOOKS TO BE THROUGH
THE AREA AROUND 18Z. 850MB TEMPS FALL QUITE A BIT WITH THE PASSAGE
OF THE TROUGH. THROUGH 12Z WEDNESDAY...THEY HOVER BETWEEN 18-20C. BY
00Z THURSDAY...THOUGH... THEY FALL TO 12-14C. THUS...ANTICIPATE A
COOLER DAY TOMORROW...MORE AROUND SEASONABLE NORMALS.
WEDNESDAY NIGHT AND THURSDAY...TROUGHING OVER THE FORECAST AREA AS A
RESULT OF THAT POTENT SHORTWAVE MOVING THROUGH WEDNESDAY LOOKS TO BE
SHORT-LIVED. THAT IS BECAUSE ANOTHER POTENT TROUGH IS PROGGED TO
DROP SOUTH INTO MONTANA BY 12Z THURSDAY. THERE WILL BE ENOUGH
SUBSIDENCE AND DRY AIR PERSISTING IN THE WAKE OF WEDNESDAYS
SHORTWAVE SUCH THAT WEDNESDAY NIGHT STAYS DRY. AT THE SURFACE...A
HIGH PRESSURE RIDGE IS PROGGED TO BUILD INTO WESTERN PORTIONS OF THE
FORECAST AREA BY 12Z THURSDAY. GIVEN THE RIDGE POSITION...ENOUGH OF
A NORTHWESTERLY BREEZE SHOULD OCCUR TO PREVENT ANY FOG AT LEAST IN
THE MISSISSIPPI RIVER VALLEY. OTHER SMALLER VALLEYS LIKE THE
WISCONSIN MAY STILL BE SUSCEPTIBLE...THOUGH. COOLER NIGHT LIKELY
WITH WINDS LIGHTENING UP THROUGH THE NIGHT AS WELL AS CLEAR SKIES.
SOME OF THE TYPICAL COLD SPOTS COULD FALL INTO THE MID 40S. ON
THURSDAY...THAT POTENT TROUGH DIGS DOWN A LITTLE MORE THROUGH
MONTANA...SETTING UP WEST-SOUTHWEST MID LEVEL FLOW OVER THE AREA.
WITHIN THIS FLOW...THERE COULD BE A SHORTWAVE SKIMMING ACROSS
NORTHERN WISCONSIN IN THE AFTERNOON...BUT OTHERWISE MODELS DO NOT
SHOW ANY OTHER SHORTWAVES OF SIGNIFICANCE. HOWEVER..WITH THAT POTENT
TROUGH DIGGING A LITTLE MORE...IT SETS UP A 310-315K ISENTROPIC
LIFT/MID-LEVEL FRONTOGENESIS ZONE DOWNSTREAM ACROSS THE NORTHERN
PLAINS INTO OUR REGION. LOOKS LIKE ANY PRECIPITATION RESULTING FROM
THIS FORCING WILL STAY WEST OF OUR AREA...BUT AN INCREASE IN
MID/HIGH CLOUDS IS LIKELY...ESPECIALLY IN THE AFTERNOON. 850MB TEMPS
OF 12-14C COMBINED WITH A DECENT AMOUNT OF SUN AND THE DRY AIR
SHOULD ALLOW FOR TEMPERATURES TO CLIMB INTO THE MID TO UPPER 70S.
THURSDAY NIGHT AND FRIDAY...THE POTENT TROUGH OVER MONTANA IS
FORECAST TO DIG SOUTHEAST DURING THIS PERIOD...BEING PUSHED BY
RIDGING DROPPING DOWN INTO SOUTH CENTRAL CANADA. BY 00Z SATURDAY...A
LONG WAVE TROUGH SHOULD EXTEND FROM NORTHEAST ONTARIO...INTO THE
FORECAST AREA AND INTO NEBRASKA. THE MAIN ISSUE WITH THIS POTENT
TROUGH COMING TOWARDS THE AREA IS WHERE DOES THE FRONTOGENESIS ZONE
AHEAD OF IT LAY UP...AND THUS THE ASSOCIATED PRECIPITATION. THE
04.00Z ECMWF KEPT THE BULK OF IT ACROSS IOWA THURSDAY NIGHT AND INTO
ILLINOIS AND MISSOURI ON FRIDAY...THUS FOR THE MOST PART OUR
FORECAST AREA ENDS UP DRY. THE 04.12Z NAM IS FARTHER NORTH...HAVING
PRECIPITATION FALL SOUTH OF INTERSTATE 94 AFTER MIDNIGHT THURSDAY
NIGHT AND FRIDAY. 04.12Z GFS IS A LITTLE MORE INTERESTING. THE MODEL
SUGGESTS SOME HIGHER LEVEL FRONTOGENESIS PRODUCING A BAND OF MOSTLY
LIGHT RAIN...WHICH SLOWLY DROPS SOUTH THROUGH THE AREA AFTER
MIDNIGHT THURSDAY NIGHT THROUGH FRIDAY. THESE BANDS SOMETIMES VERIFY
AND OTHER TIMES NOT. OVERALL...THE BULK OF THE PRECIPITATION IN THE
GFS FALLS TO THE SOUTH. IN ANY EVENT...ALL MODELS SUGGEST A NEED TO
INCREASE PRECIPITATION CHANCES UP TO 40 FOR NOW...MAINLY SOUTH OF
I-90. FURTHER REFINEMENTS WILL BE NEEDED AS WE GET CLOSER TO THIS
PERIOD. WITH MORE CLOUDS AS WELL AS COOLER AIR COMING IN WITH THE
UPPER TROUGH...ANTICIPATE THIS PERIOD TO BE MUCH COOLER THAN AS OF
LATE. THIS WILL BE ESPECIALLY TRUE ON FRIDAY AS 850MB TEMPS FALL TO
6-9C. HIGHS ON FRIDAY MAY GET STUCK IN THE 60S...ESPECIALLY IF IT
RAINS ALL DAY LIKE THE NAM.
.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY
256 PM CDT TUE SEP 4 2012
04.12Z ECMWF/GFS/CANADIAN AND GFS ENSEMBLES ARE A LITTLE DIFFERENT
AMONGST EACH OTHER TODAY COMPARED TO YESTERDAY...MOSTLY WITH REGARDS
TO HANDLING WHETHER THE UPPER TROUGH COMING THROUGH THE FORECAST
AREA FRIDAY ENDS UP CLOSING OFF IN THE OHIO RIVER VALLEY.
INTERESTINGLY...THE 04.12Z ECMWF/CANADIAN AND GFS HAVE NOW
FLIP-FLOPPED WITH EACH OTHER...WITH THE ECMWF/CANADIAN NOW MORE
PROGRESSIVE AND THE GFS CLOSING OFF. FOR OUR AREA...THOUGH...WHICH
EVER SOLUTION PANS OUT REALLY DOESNT MATTER...AS BOTH SCENARIOS
BUILD HIGH PRESSURE INTO THE FORECAST AREA FOR THE WEEKEND. SO MAYBE
AFTER A FEW LINGERING SHOWERS IN NORTHEAST IA/SOUTHWEST WI FRIDAY
NIGHT...EXPECT DECREASING CLOUDS AND DRY WEATHER FOR THE WEEKEND.
CERTAINLY LOOKS COOL COMPARED TO WHAT HAS BEEN SEEN RECENTLY...
THANKS TO 850MB TEMPS OF 6-8C ON SATURDAY AND 10-12C ON SUNDAY.
WOULD NOT BE SURPRISED IF SOME OF THE TYPICAL COLD SPOTS END UP
SEEING SOME UPPER 30S.
FOR EARLY NEXT WEEK...UPPER RIDGING OVER THE WESTERN U.S. IS
FORECAST TO BUILD UP INTO THE FORECAST AREA...BUT FLATTEN PRETTY
QUICKLY BY TUESDAY AS A SHORTWAVE TROUGH CROSSING SOUTHERN CANADA.
WILL SEE A WARM UP WITH THE RIDGING COMING IN...AT LEAST BACK TO
NORMAL. DRY CONDITIONS SHOULD CONTINUE AS WELL WITH THE HIGH
PRESSURE OVER THE WEEKEND BLOCKING GULF OF MEXICO MOISTURE RETURN.
&&
.AVIATION...TONIGHT AND WEDNESDAY
637 PM CDT TUE SEP 4 2012
CURRENT CONVECTION SHOULD PUSH EAST OF THE KLSE BETWEEN 00 AND
01Z...GIVING WAY TO CLEAR SKIES AND GENERALLY WESTERLY WINDS. NEXT
FOCUS IS ON OVERNIGHT CONVECTION EXPECTED TO FIRE UP ACROSS
SOUTHERN MINNESOTA AT THE NOSE OF THE 850 MB MOISTURE TRANSPORT
AND AHEAD OF SURFACE COLD FRONT. STORMS SHOULD DEVELOP AROUND
06Z...AND THEN PUSH EAST ACROSS THE TAF SITES THROUGH AROUND 12Z.
ONE CONCERN FOR THE OVERNIGHT GIVEN THIS EVENING/S RAINFALL IS
DENSE FOG AT KLSE. IF SKIES REMAIN CLEAR EARLY ON AND WITH LIGHT
WINDS...COULD SEE SOME PATCHY RIVER VALLEY FOG AT KLSE. THIS WILL
NEED TO BE CLOSELY MONITORED.
CONTINUED PREVIOUS FORECAST FOR THE MOST PART...EXCEPT ADDED A
VICINITY SHOWER BETWEEN 13-15Z. WINDS WILL SHIFT TO THE NORTH
BEHIND COLD FRONTAL PASSAGE AN SKIES WILL BECOME CLEAR WITH SOME
GUSTY WINDS POSSIBLY UP TO 20 KTS AT KRST.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
256 PM CDT TUE SEP 4 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM...AJ
AVIATION...ZT
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
256 PM CDT MON SEP 3 2012
.SHORT TERM...TONIGHT THROUGH THURSDAY
256 PM CDT MON SEP 3 2012
MAIN FORECAST CONCERNS ARE ON PRECIPITATION CHANCES THROUGH
WEDNESDAY.
CURRENTLY AS OF 20Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED BROAD TROUGHING OVER SOUTHWEST AND SOUTH CENTRAL CANADA...
WITH NEARLY ZONAL FLOW ON ITS SOUTH SIDE ACROSS MUCH OF THE NORTHERN
U.S.. WITHIN THE BROAD UPPER TROUGHING...A PORTENT SHORTWAVE IS
EVIDENT OVER CENTRAL ALBERTA. IN THE ZONAL FLOW...THERE ARE NUMEROUS
WEAK SHORTWAVES...WHICH DURING THIS MORNING PRETTY MUCH ALL HAD AT
LEAST ACCAS OR CONVECTION WITH THEM: ONE IN NORTH DAKOTA...ANOTHER
IN WESTERN MINNESOTA...ONE IN WESTERN NEBRASKA AND LASTLY ONE IN
CENTRAL IOWA. DPVA AHEAD OF THE SHORTWAVE IN CENTRAL IOWA COMBINED
WITH A WEAKENING SURFACE COLD FRONT EXTENDING FROM CENTRAL UPPER
MICHIGAN TO NEAR DES MOINES...AS WELL AS MLCAPE VALUES THAT HAVE
CLIMBED TO 1500-2000 J/KG WITH LITTLE CIN PER RAP ANALYSIS...HAS
ALLOWED FOR SHOWER AND THUNDERSTORM DEVELOPMENT. MOST OF THE
ACTIVITY HAS BEEN DISORGANIZED...DUE TO 0-6KM SHEAR BELOW 30 KT
WHERE STORMS ARE IN THE FORECAST AREA. ALSO...A SURGE OF MONSOONAL
MID-CLOUDS THROUGH THE UPPER FLOW IS HELPING TO PUT A LID ON THE
AMOUNT OF INSTABILITY. THERE ARE EVEN SOME SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS COMING OUT OF THESE MID CLOUDS. WITH THE
VARYING CLOUD COVER AND PRECIPITATION...TEMPERATURES TODAY ARE ALL
OVER THE PLACE IN THE FORECAST AREA. MOST LOCATIONS REACHED
80...WHILE BOSCOBEL GOT CLOSE TO 90. ABNORMALLY HIGH DEWPOINTS
PERSIST TOO...WITH MOST OF THE AREA SEEING READINGS AROUND 70F.
TONIGHT AND TUESDAY...VERY TRICKY FORECAST TO SAY THE LEAST. THE
NEAR ZONAL FLOW WILL PERSIST THROUGH THIS PERIOD AS THE POTENT
ALBERT SHORTWAVE DIGS DOWN INTO THE NORTHERN PLAINS. MODELS CONTINUE
TO INDICATE WEAK SHORTWAVES MOVING THROUGH THIS FLOW...LIKE THOSE
AROUND THE DAKOTAS TODAY. WITH MUCAPE VALUES PROGGED TO NOT DROP
MUCH BELOW 1000 J/KG...HIGHLY CONCERNED THERE COULD BE OFF AND ON
SHOWERS AND THUNDERSTORMS THROUGHOUT THIS PERIOD. THIS HAS BEEN
SUGGESTED THE PAST FEW DAYS...ESPECIALLY BY THE ECMWF...THOUGH THE
LATEST 03.12Z ECMWF IS NOT AS ACTIVE. NOW SOME HI RESOLUTION MODEL
RUNS HAVE SUGGESTED THAT THE CURRENT AFTERNOON CONVECTION DROPS
SOUTHEAST THIS EVENING...WHILE OTHER CONVECTION DEVELOPS IN IOWA AND
DROPS SOUTHEAST. THIS ALLOWS THE FORECAST AREA TO END UP DRY AFTER
MIDNIGHT. FOR NOW HOLDING ON TO SOME LOW CHANCES OF PRECIPITATION
BECAUSE OF TOO MUCH UNCERTAINTY TO GO DRY BASED ON THE ENVIRONMENT.
IF SKIES CLEAR OUT TONIGHT...THE HIGH AMOUNT OF SURFACE MOISTURE
AROUND AND WEAK WIND FIELD WOULD LIKELY RESULT IN WIDESPREAD
RADIATION FOG. NOT ENTIRELY CONFIDENT WE WILL HAVE A LONG PERIOD OF
CLEAR SKIES...THOUGH. SO IN SUMMARY...THERE APPEARS TO BE TWO
SCENARIOS FOR TONIGHT:
1. SKIES CLEAR AND WE END UP WITH DENSE FOG
2. PERIODS OF ACCAS AND ISOLATED SHOWERS/STORMS
RIGHT NOW...BANKING ON NUMBER 2 AND ACKNOWLEDGING THE FOG BY ADDING
AT LEAST A PATCHY MENTION AFTER MIDNIGHT INTO TUESDAY MORNING. WITH
THE HIGH AMOUNT OF SURFACE MOISTURE...ANTICIPATING TEMPERATURES
OUTSIDE OF THE TYPICAL COLD SPOTS TO NOT DROP BELOW THE MID 60S.
DEPENDING ON AMOUNT OF SUN ON TUESDAY...WITH 850MB TEMPS BETWEEN
18-20C...HIGHS COULD GET CLOSE TO 90.
TUESDAY NIGHT AND WEDNESDAY...THE POTENT SHORTWAVE TROUGH COMING
INTO THE NORTHERN PLAINS AT 00Z WEDNESDAY IS FORECAST TO DIG INTO
MINNESOTA BY 12Z...THEN RAPIDLY SHOOT EAST OVER MUCH OF MICHIGAN BY
00Z THURSDAY. THIS RAPID MOVEMENT MEANS AN OVERALL SHORT TIME WINDOW
FOR PRECIPITATION FORCED BY THE TROUGH. NOTE THAT THE BEST 500-300MB
PV ADVECTION IS STILL SUGGESTED TO STAY TO THE NORTH OF THE FORECAST
AREA. HOWEVER...THE COMBINATION OF WEAK 500MB HEIGHT FALLS...A SURGE
OF LOW TO MID LEVEL MOISTURE TRANSPORT...AS WELL AS AT LEAST
1000-1500 J/KG OF MUCAPE ACCOMPANYING THE MOISTURE TRANSPORT SHOULD
PRODUCE SHOWERS AND THUNDERSTORMS ACROSS MUCH OF THE AREA. SOME OF
THESE COULD GET GOING AS EARLY AS THE EVENING...BUT BETTER CHANCES
ARE EXPECTED AFTER MIDNIGHT THROUGH ABOUT 15Z WEDNESDAY...WHEN THE
TROUGH IS HAVING ITS BIGGEST FORCING INFLUENCE. 1-6KM SHEAR IS
GENERALLY 15-25KT...WHICH SHOULD KEEP CONVECTION SUB-SEVERE. AFTER
15Z...STRONG SUBSIDENCE WILL WORK IN WEST TO EAST...CLEARING SKIES
OUT. WINDS SHOULD PICK UP TOO AS THE PRESSURE GRADIENT TIGHTENS...
COLD ADVECTION AND DEEP MIXING OCCUR. NOTING ABOUT THE COLD
ADVECTION...850MB TEMPS WHICH LOOK TO HOVER BETWEEN 16-20C TUESDAY
NIGHT END UP FALLING TO 12-14C OR SLIGHTLY COOLER BY 00Z WEDNESDAY.
THUS...EXPECT COOLER HIGHS FOR WEDNESDAY ON THE ORDER OF MID 70S TO
LOWER 80S. TUESDAY NIGHT WILL STILL BE WARM WITH LOWS IN THE
60S...THANKS TO SOUTH FLOW AHEAD OF THE SHORTWAVE/ASSOCIATED COLD
FRONT AND HIGHER DEWPOINTS.
WEDNESDAY NIGHT AND THURSDAY...IN THE WAKE OF WEDNESDAYS POTENT
SHORTWAVE...UPPER FLOW TURNS ZONAL OVER THE AREA. BUT THIS IS
BRIEF...WITH ATTENTION TURNING BACK TO ALBERTA WHERE YET ANOTHER
POTENT SHORTWAVE IS PROGGED TO DROP SOUTH INTO MONTANA BY 00Z
FRIDAY. WEDNESDAY NIGHT STILL LOOKS DRY THANKS TO LINGERING DRY AIR
AND SUBSIDENCE IN THE WAKE OF WEDNESDAYS TROUGH. THURSDAY IS A
LITTLE MORE PROBLEMATIC. TO THE NORTH...MODELS ARE INDICATING A
COUPLE OF SHORTWAVES CROSSING NORTHERN MINNESOTA AND WISCONSIN...
WHICH BRING DOWN A COLD FRONT INTO NORTHWEST WI BY 00Z. BOTH THE
03.12Z NAM AND 03.06Z GFS DEPICT SOME LIGHT QPF ACROSS TAYLOR COUNTY
WITH THIS FEATURE IN THE AFTERNOON. SOUNDINGS SUGGEST VERY LITTLE
MUCAPE WITH THIS FRONT AND A FAIRLY DRY BOUNDARY LAYER BELOW 750MB.
NEW 03.12Z GFS HAS CAME IN DRY. THEREFORE...HAVE HELD OFF ON MENTION
ANY PRECIPITATION CHANCES UP AROUND TAYLOR COUNTY. FOR THE REST OF
THE AREA...300-305K ISENTROPIC LIFT GRADUALLY INCREASES DURING THE
AFTERNOON...ALL KIND OF DOWNSTREAM OF THAT SHORTWAVE DROPPING INTO
MONTANA. SHOULD SEE SOME MID/HIGH CLOUDS DEVELOP AS A RESULT OF THIS
LIFT...BUT THINKING THE MAJORITY OF THESE CLOUDS ANY PRECIPITATION
POTENTIAL WITH THEM WILL STAY WEST/SOUTHWEST OF THE AREA. THIS
AGREES WELL WITH THE 03.12Z GFS/ECMWF. COOLER PERIOD ANTICIPATED.
MAY HAVE TO WATCH FOR VALLEY FOG POTENTIAL IF THE SURFACE RIDGE OF
HIGH PRESSURE COMING IN WEDNESDAY NIGHT BUILDS IN FASTER.
.LONG TERM...THURSDAY NIGHT THROUGH MONDAY
256 PM CDT MON SEP 3 2012
THROUGH SATURDAY...MODELS REMAIN IN GOOD AGREEMENT WITH THE HANDLING
OF THE POTENT SHORTWAVE OVER MONTANA...HOW IT ENDS UP FORMING A
FAIRLY DEEP TROUGH OVER THE UPPER AND MID MISSISSIPPI RIVER VALLEYS
BY 12Z SATURDAY. AS THIS TROUGH FORMS...FRONTOGENESIS DOWNSTREAM
WILL LIKELY SPREAD MID/HIGH CLOUDS ACROSS THE AREA THURSDAY NIGHT
AND FRIDAY...SOME OF WHICH COULD PRODUCE A FEW SHOWERS. OVERALL...
BULK OF PRECIPITATION IS ANTICIPATED TO STAY TO THE SOUTH...CLOSER
TO A DEVELOPING LOW PRESSURE SYSTEM LIFTING OUT OF THE CENTRAL
PLAINS. BY FRIDAY NIGHT...AS THE TROUGHING MOVES IN...THE CLOUDS AND
POTENTIAL FOR SHOWERS GET PUSHED EAST. HIGH PRESSURE THEN BUILDS IN
FOR SATURDAY. MUCH OF THIS PERIOD THROUGH SATURDAY WILL BE BELOW
NORMAL...DUE TO FIRST CLOUDS ON FRIDAY AND THEN 850MB TEMPS FALLING
TO 6-8C FOR SATURDAY. HIGHS MAY STRUGGLE TO CLIMB TO OR MUCH ABOVE
70.
BEYOND SATURDAY...MODELS HANDLE THE TROUGHING DIFFERENTLY...WITH THE
03.12Z ECMWF AND CANADIAN CLOSING IT OFF AND PERHAPS MOVING IT
SOUTHEAST...WHEREAS THE 03.12Z GFS AND ITS ENSEMBLES REMAIN MORE
PROGRESSIVE. FOR THE FORECAST AREA...EITHER SCENARIO DOESNT MATTER
MUCH...AS ALL MODELS END UP HAVING UPPER RIDGING BUILDING UP OVER
THE PLAINS AND INTO THE FORECAST AREA LATE MONDAY. THIS WILL KEEP
CONDITIONS DRY WITH A GRADUAL WARMING TREND. BY MONDAY...850MB TEMPS
ARE BACK UP TO 12-14C...YIELDING HIGHS AT LEAST AROUND NORMAL.
&&
.AVIATION...THIS AFTERNOON INTO TUESDAY
1215 PM CDT MON SEP 3 2012
BKN LINE OF CONVECTION WAS MOVING STEADILY EAST/NORTHEAST ACROSS THE
FCST AREA AT MID-DAY. LINE HAD ALREADY CLEARED KRST WHILE DISTANCE
SPEED-TOOL PUTS IT THRU THE KLSE AREA IN THE 1830-1930Z TIME FRAME.
ADDED A TEMPO MVFR TSRA PERIOD TO KLSE FOR THE EARLY AFTERNOON.
CONDITIONS GO BACK TO VFR AFTER THE LINE OF SHRA/TSRA PASSES FOR
THE LATE AFTERNOON/EVENING HOURS. HOWEVER...THE MOIST AIRMASS WITH
SOME MIXED LAYER OR ELEVATED CAPE REMAINS OVER THE AREA TONIGHT INTO
TUE. WITH WEAK SHORTWAVES RIPPLING ACROSS THE AREA TONIGHT INTO
TUE...ISOLATED TO SCT SHRA/TSRA REMAIN POSSIBLE. GIVEN POOR
CONFIDENCE IN THE TIMING/COVERAGE DETAILS OF ANY CONVECTION TONIGHT
INTO TUE...LEFT THIS MENTION OUT OF THE TAFS FOR NOW VS. HAVING A
RATHER LONG PERIOD OF VCSH AT BOTH SITES. LATER TAF ISSUANCES CAN
ADD ANY SHRA/TSRA TO TAFS FOR SHORTER PERIODS OF TIME IF NEEDED AS
DETAILS BECOME CLEARER.
THE OTHER CONCERN IS THE MOIST LOW LEVEL/BOUNDARY LAYER AIRMASS THAT
WILL REMAIN OVER THE AREA TONIGHT. TEMP-DEWPOINT SPREADS ARE LIKELY
TO BE LOW GOING INTO SUNSET...ALONG WITH LIGHT/VARIABLE SFC WINDS.
IF SKIES TREND TOWARD MORE CLEAR/MOSTLY CLEAR TONIGHT VS. BKN MID/
HIGH CLOUD DECKS...MVFR/IFR BR/FG WILL BE MORE OF A PROBLEM AFTER
MIDNIGHT INTO THE MID MORNING HOURS OF TUE. WITH THE POTENTIAL FOR
SCT -SHRA TONIGHT AND BKN MID/HIGH CLOUDS LOOKING MORE FAVORED...
ONLY ADDED 4SM BR IN THE 08-14Z TIME TO BOTH KRST/KLSE FOR NOW.
LATER SHIFTS WILL HAVE TO WATCH THIS FOR IFR FG POTENTIAL AS WELL.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
256 PM CDT MON SEP 3 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM...AJ
AVIATION.....RRS
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1215 PM CDT MON SEP 3 2012
.SHORT TERM...TODAY THROUGH WEDNESDAY
327 AM CDT MON SEP 3 2012
CONCERNS CENTER AROUND RAIN CHANCES THROUGH THE PERIOD/SEVERE
CHANCES TODAY.
BUSY WATER VAPOR LOOP THIS MORNING WITH A MID LEVEL TROUGH MOVING
THROUGH MN AND THEN A MORE VIGOROUS CLOSED LOW/TROUGH MOVING THROUGH
ALBERTA CANADA/MONTANA. AT THE SURFACE...A COLD FRONT EXTENDED FROM
NEAR INTERNATIONAL FALLS TO SAINT CLOUD MN...AND THEN SOUTHWESTWARD
TO SIOUX FALLS SD. RADAR MOSAIC SHOWING BAND OF SCATTERED
SHOWERS/THUNDERSTORMS AHEAD OF THE FRONT FROM NEAR THE ARROWHEAD OF MN
INTO NORTHWEST WI AND EAST CENTRAL MN. RAP SHOWS THIS ACTIVITY WAS
ON THE EASTERN PERIPHERY OF FAIRLY DECENT AXIS OF 850MB MOISTURE
TRANSPORT. OTHERWISE...TEMPERATURES ACROSS THE FORECAST AREA AT 3 AM
WERE HOLDING IN THE UPPER 60S/LOWER 70S WITH DEWPOINTS IN THE MIDDLE
60S.
SUNDAY EVENING MODEL RUNS SHOWING FAIRLY DECENT AGREEMENT THROUGH
THE SHORT TERM PERIOD.
LOOK FOR THE MID-LEVEL SHORTWAVE AND ASSOCIATED SURFACE COLD FRONT
OVER MN TO SINK SLOWLY SOUTHEAST INTO THE AREA TODAY...WHILE
UNDERGOING SOME WEAKENING. RAP/NAM MODELS SHOWING BEST 850MB
MOISTURE TRANSPORT AHEAD OF THE TROUGH/FRONT PUSHING EAST OF THE
AREA BY LATER THIS MORNING. HOWEVER...MODELS FAIRLY PERSISTENT IN
PRODUCING SCATTERED SHOWERS AND THUNDERSTORM TODAY ACROSS THE
AREA...WITH BETTER CHANCES HEADED INTO THE AFTERNOON GIVEN PEAK
HEATING/HIGHER DEW POINT POOLING AND 0-3KM MUCAPE PEAKING IN THE
3000-5000J/KG RANGE WITH DOWNDRAFT CAPE IN THE 1500-2000J/KG RANGE.
UPPER LEVEL DYNAMICS HELP ALSO GIVEN RIGHT ENTRANCE REGION OF 300MB
JET PER THE NAM BY THIS AFTERNOON. MODEL SOUNDINGS SHOW INVERTED-V
AND ALTHOUGH 0-3KM BULK SHEAR FAIRLY LIMITED...DOWNDRAFT CAPE HAS ME
A BIT CONCERNED FOR DAMAGING WIND POTENTIAL. WILL HAVE TO KEEP A
VERY CLOSE EYE ON THINGS TODAY. OTHERWISE...ANOTHER UNSEASONABLY
WARM DAY ON TAP WITH HIGHS PUSHING INTO THE 80S ONCE AGAIN.
LOOKING FOR THE BULK OF THE SHOWERS/THUNDERSTORMS TO MOVE SOUTHEAST
OF THE AREA THIS EVENING...BUT THEN MODELS SHOWING ANOTHER MID-LEVEL
TROUGH PUSHING ACROSS THE PLAINS TOWARD THE AREA AFTER MIDNIGHT WITH
WEAK ISENTROPIC LIFT AND MOISTURE TRANSPORT. KEPT SMALLER 20-30 POP
SHRA/T CHANCE TO COVER THIS WEAKER SIGNAL.
GFS AND NAM HINTING AT SOME SORT OF WEAK TROUGH RIPPLING THROUGH
FAIRLY HIGH-ZONAL FLOW ALOFT ON TUESDAY WITH SOME MINOR TIMING
DIFFERENCES NOTED. GIVEN THIS RATHER NONDESCRIPT SIGNAL...WILL STICK
WITH SLIGHT CHANCE OF SHRA/TS.
A MORE VIGOROUS MID-LEVEL CLOSED LOW SWINGS EAST ACROSS SOUTHERN
CANADA TUESDAY NIGHT/WEDNESDAY WITH TROUGH AXIS AND ASSOCIATED
STRONG SURFACE COLD FRONT SWINGING EAST ACROSS THE AREA. THIS HAS BEEN A
RATHER CONSISTENT SIGNAL THE LAST FEW DAYS NOW...SO FEEL COMFORTABLE
WITH HIGHER-END CHANCE TO LIKELY SHRA/TS. GIVEN TIMING OF THE
FRONTAL PASSAGE THROUGH THE AREA WEDNESDAY MORNING...SEVERE THREAT
LOOKS TO BE SOUTHEAST OF THE AREA DURING THE AFTERNOON.
OTHERWISE...MODEL SOUNDINGS SHOWING GOOD MIXING/DRYING BEHIND THE
FRONT WEDNESDAY AFTERNOON ON BREEZY NORTHWEST WINDS IN THE 15 TO 30
MPH RANGE. TEMPERATURES WILL ALSO RETURN TO NEAR SEASONAL NORMALS IN
THE MID 70S TO LOWER 80S.
.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY
327 AM CDT MON SEP 3 2012
FAIRLY GOOD AGREEMENT BETWEEN THE GFS AND ECMWF IN THE WEDNESDAY
NIGHT THROUGH SATURDAY TIME FRAME. WEDNESDAY NIGHT/THURSDAY LOOK
COOLER AND DRY AS MID/UPPER LEVEL TROUGH SETTLES INTO THE AREA. LOWS
WEDNESDAY NIGHT EXPECTED TO FALL INTO THE UPPER 40S TO LOWER 50S WITH
HIGHS ON THURSDAY IN THE 70S. SHRA/TS CHANCES RETURN TO THE AREA
THURSDAY NIGHT THROUGH FRIDAY NIGHT AS AS ANOTHER MID-LEVEL TROUGH
DROPS THROUGH THE REGION WITH A REINFORCING SHOT OF COOLER AND MORE
AUTUMN-LIKE AIR. EXPECTING HIGHS ON FRIDAY IN THE UPPER 60S TO
MIDDLE 70S WITH LOWS IN THE UPPER 40S TO MIDDLE 50S. SATURDAY
CONTINUES TO BE COOL BUT DRY WITH HIGHS IN THE UPPER 60S AND LOWER
70S AFTER OVERNIGHT LOWS IN THE UPPER 40S TO LOWER 50S. APPEARS
SUNDAY WILL SEE SOME WARMING AS MID-LEVEL HEIGHTS BUILD IN RESPONSE
TO RIDGE BUILDING IN FROM THE PLAINS. LOOK FOR HIGHS IN THE LOWER TO
MIDDLE 70S.
&&
.AVIATION...THIS AFTERNOON INTO TUESDAY
1215 PM CDT MON SEP 3 2012
BKN LINE OF CONVECTION WAS MOVING STEADILY EAST/NORTHEAST ACROSS THE
FCST AREA AT MID-DAY. LINE HAD ALREADY CLEARED KRST WHILE DISTANCE
SPEED-TOOL PUTS IT THRU THE KLSE AREA IN THE 1830-1930Z TIME FRAME.
ADDED A TEMPO MVFR TSRA PERIOD TO KLSE FOR THE EARLY AFTERNOON.
CONDITIONS GO BACK TO VFR AFTER THE LINE OF SHRA/TSRA PASSES FOR
THE LATE AFTERNOON/EVENING HOURS. HOWEVER...THE MOIST AIRMASS WITH
SOME MIXED LAYER OR ELEVATED CAPE REMAINS OVER THE AREA TONIGHT INTO
TUE. WITH WEAK SHORTWAVES RIPPLING ACROSS THE AREA TONIGHT INTO
TUE...ISOLATED TO SCT SHRA/TSRA REMAIN POSSIBLE. GIVEN POOR
CONFIDENCE IN THE TIMING/COVERAGE DETAILS OF ANY CONVECTION TONIGHT
INTO TUE...LEFT THIS MENTION OUT OF THE TAFS FOR NOW VS. HAVING A
RATHER LONG PERIOD OF VCSH AT BOTH SITES. LATER TAF ISSUANCES CAN
ADD ANY SHRA/TSRA TO TAFS FOR SHORTER PERIODS OF TIME IF NEEDED AS
DETAILS BECOME CLEARER.
THE OTHER CONCERN IS THE MOIST LOW LEVEL/BOUNDARY LAYER AIRMASS THAT
WILL REMAIN OVER THE AREA TONIGHT. TEMP-DEWPOINT SPREADS ARE LIKELY
TO BE LOW GOING INTO SUNSET...ALONG WITH LIGHT/VARIABLE SFC WINDS.
IF SKIES TREND TOWARD MORE CLEAR/MOSTLY CLEAR TONIGHT VS. BKN MID/
HIGH CLOUD DECKS...MVFR/IFR BR/FG WILL BE MORE OF A PROBLEM AFTER
MIDNIGHT INTO THE MID MORNING HOURS OF TUE. WITH THE POTENTIAL FOR
SCT -SHRA TONIGHT AND BKN MID/HIGH CLOUDS LOOKING MORE FAVORED...
ONLY ADDED 4SM BR IN THE 08-14Z TIME TO BOTH KRST/KLSE FOR NOW.
LATER SHIFTS WILL HAVE TO WATCH THIS FOR IFR FG POTENTIAL AS WELL.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
327 AM CDT MON SEP 3 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...DAS
LONG TERM....DAS
AVIATION.....RRS
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
649 AM CDT MON SEP 3 2012
.SHORT TERM...TODAY THROUGH WEDNESDAY
327 AM CDT MON SEP 3 2012
CONCERNS CENTER AROUND RAIN CHANCES THROUGH THE PERIOD/SEVERE
CHANCES TODAY.
BUSY WATER VAPOR LOOP THIS MORNING WITH A MID LEVEL TROUGH MOVING
THROUGH MN AND THEN A MORE VIGOROUS CLOSED LOW/TROUGH MOVING THROUGH
ALBERTA CANADA/MONTANA. AT THE SURFACE...A COLD FRONT EXTENDED FROM
NEAR INTERNATIONAL FALLS TO SAINT CLOUD MN...AND THEN SOUTHWESTWARD
TO SIOUX FALLS SD. RADAR MOSAIC SHOWING BAND OF SCATTERED
SHOWERS/THUNDERSTORMS AHEAD OF THE FRONT FROM NEAR THE ARROWHEAD OF MN
INTO NORTHWEST WI AND EAST CENTRAL MN. RAP SHOWS THIS ACTIVITY WAS
ON THE EASTERN PERIPHERY OF FAIRLY DECENT AXIS OF 850MB MOISTURE
TRANSPORT. OTHERWISE...TEMPERATURES ACROSS THE FORECAST AREA AT 3 AM
WERE HOLDING IN THE UPPER 60S/LOWER 70S WITH DEWPOINTS IN THE MIDDLE
60S.
SUNDAY EVENING MODEL RUNS SHOWING FAIRLY DECENT AGREEMENT THROUGH
THE SHORT TERM PERIOD.
LOOK FOR THE MID-LEVEL SHORTWAVE AND ASSOCIATED SURFACE COLD FRONT
OVER MN TO SINK SLOWLY SOUTHEAST INTO THE AREA TODAY...WHILE
UNDERGOING SOME WEAKENING. RAP/NAM MODELS SHOWING BEST 850MB
MOISTURE TRANSPORT AHEAD OF THE TROUGH/FRONT PUSHING EAST OF THE
AREA BY LATER THIS MORNING. HOWEVER...MODELS FAIRLY PERSISTENT IN
PRODUCING SCATTERED SHOWERS AND THUNDERSTORM TODAY ACROSS THE
AREA...WITH BETTER CHANCES HEADED INTO THE AFTERNOON GIVEN PEAK
HEATING/HIGHER DEW POINT POOLING AND 0-3KM MUCAPE PEAKING IN THE
3000-5000J/KG RANGE WITH DOWNDRAFT CAPE IN THE 1500-2000J/KG RANGE.
UPPER LEVEL DYNAMICS HELP ALSO GIVEN RIGHT ENTRANCE REGION OF 300MB
JET PER THE NAM BY THIS AFTERNOON. MODEL SOUNDINGS SHOW INVERTED-V
AND ALTHOUGH 0-3KM BULK SHEAR FAIRLY LIMITED...DOWNDRAFT CAPE HAS ME
A BIT CONCERNED FOR DAMAGING WIND POTENTIAL. WILL HAVE TO KEEP A
VERY CLOSE EYE ON THINGS TODAY. OTHERWISE...ANOTHER UNSEASONABLY
WARM DAY ON TAP WITH HIGHS PUSHING INTO THE 80S ONCE AGAIN.
LOOKING FOR THE BULK OF THE SHOWERS/THUNDERSTORMS TO MOVE SOUTHEAST
OF THE AREA THIS EVENING...BUT THEN MODELS SHOWING ANOTHER MID-LEVEL
TROUGH PUSHING ACROSS THE PLAINS TOWARD THE AREA AFTER MIDNIGHT WITH
WEAK ISENTROPIC LIFT AND MOISTURE TRANSPORT. KEPT SMALLER 20-30 POP
SHRA/T CHANCE TO COVER THIS WEAKER SIGNAL.
GFS AND NAM HINTING AT SOME SORT OF WEAK TROUGH RIPPLING THROUGH
FAIRLY HIGH-ZONAL FLOW ALOFT ON TUESDAY WITH SOME MINOR TIMING
DIFFERENCES NOTED. GIVEN THIS RATHER NONDESCRIPT SIGNAL...WILL STICK
WITH SLIGHT CHANCE OF SHRA/TS.
A MORE VIGOROUS MID-LEVEL CLOSED LOW SWINGS EAST ACROSS SOUTHERN
CANADA TUESDAY NIGHT/WEDNESDAY WITH TROUGH AXIS AND ASSOCIATED
STRONG SURFACE COLD FRONT SWINGING EAST ACROSS THE AREA. THIS HAS BEEN A
RATHER CONSISTENT SIGNAL THE LAST FEW DAYS NOW...SO FEEL COMFORTABLE
WITH HIGHER-END CHANCE TO LIKELY SHRA/TS. GIVEN TIMING OF THE
FRONTAL PASSAGE THROUGH THE AREA WEDNESDAY MORNING...SEVERE THREAT
LOOKS TO BE SOUTHEAST OF THE AREA DURING THE AFTERNOON.
OTHERWISE...MODEL SOUNDINGS SHOWING GOOD MIXING/DRYING BEHIND THE
FRONT WEDNESDAY AFTERNOON ON BREEZY NORTHWEST WINDS IN THE 15 TO 30
MPH RANGE. TEMPERATURES WILL ALSO RETURN TO NEAR SEASONAL NORMALS IN
THE MID 70S TO LOWER 80S.
.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY
327 AM CDT MON SEP 3 2012
FAIRLY GOOD AGREEMENT BETWEEN THE GFS AND ECMWF IN THE WEDNESDAY
NIGHT THROUGH SATURDAY TIME FRAME. WEDNESDAY NIGHT/THURSDAY LOOK
COOLER AND DRY AS MID/UPPER LEVEL TROUGH SETTLES INTO THE AREA. LOWS
WEDNESDAY NIGHT EXPECTED TO FALL INTO THE UPPER 40S TO LOWER 50S WITH
HIGHS ON THURSDAY IN THE 70S. SHRA/TS CHANCES RETURN TO THE AREA
THURSDAY NIGHT THROUGH FRIDAY NIGHT AS AS ANOTHER MID-LEVEL TROUGH
DROPS THROUGH THE REGION WITH A REINFORCING SHOT OF COOLER AND MORE
AUTUMN-LIKE AIR. EXPECTING HIGHS ON FRIDAY IN THE UPPER 60S TO
MIDDLE 70S WITH LOWS IN THE UPPER 40S TO MIDDLE 50S. SATURDAY
CONTINUES TO BE COOL BUT DRY WITH HIGHS IN THE UPPER 60S AND LOWER
70S AFTER OVERNIGHT LOWS IN THE UPPER 40S TO LOWER 50S. APPEARS
SUNDAY WILL SEE SOME WARMING AS MID-LEVEL HEIGHTS BUILD IN RESPONSE
TO RIDGE BUILDING IN FROM THE PLAINS. LOOK FOR HIGHS IN THE LOWER TO
MIDDLE 70S.
&&
.AVIATION...TODAY AND TONIGHT
649 AM CDT MON SEP 3 2012
THE MAIN FORECAST CONCERNS AT THE TAF SITES ARE WITH THE
THUNDERSTORM CHANCES TODAY INTO TONIGHT AS A COLD FRONT MOVES
THROUGH THE REGION. ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS HAVE DEVELOPED THIS MORNING FROM NORTHWEST WISCONSIN
DOWN INTO SOUTH CENTRAL MINNESOTA AND WILL MOVE EAST TOWARD
RST/LSE THIS MORNING. CONDITIONS ARE MAINLY VFR AT THE MOMENT WITH
CEILINGS UP AROUND 8-12KFT...BUT IF ANY OF THESE SHOWERS/STORMS
HAPPEN TO HIT RST OR LSE THERE COULD BE SOME VERY BRIEF VISIBILITY
DROPS TO MVFR OR IFR. VISIBILITY AT RST HAS ALREADY DROPPED DOWN
TO 5SM DUE TO SOME HAZE THAT FORMED THIS MORNING DUE TO THE HIGH
MOISTURE CONTENT AT THE SURFACE. THE SHOWERS/STORMS THIS MORNING
WILL COME TO AN END THIS AFTERNOON AS THE COLD FRONT MOVES THROUGH
AND WINDS COME AROUND TO THE WEST-NORTHWEST. THERE ARE SOME HINTS
THAT MORE STORMS COULD DEVELOP OVERNIGHT...BUT CONFIDENCE IS NOT
HIGH ENOUGH AT THIS POINT TO PUT ANY MENTION IN THE TAFS.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
327 AM CDT MON SEP 3 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...DAS
LONG TERM...DAS
AVIATION...HALBACH
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
327 AM CDT MON SEP 3 2012
.SHORT TERM...TODAY THROUGH WEDNESDAY
327 AM CDT MON SEP 3 2012
CONCERNS CENTER AROUND RAIN CHANCES THROUGH THE PERIOD/SEVERE
CHANCES TODAY.
BUSY WATER VAPOR LOOP THIS MORNING WITH A MID LEVEL TROUGH MOVING
THROUGH MN AND THEN A MORE VIGOROUS CLOSED LOW/TROUGH MOVING THROUGH
ALBERTA CANADA/MONTANA. AT THE SURFACE...A COLD FRONT EXTENDED FROM
NEAR INTERNATIONAL FALLS TO SAINT CLOUD MN...AND THEN SOUTHWESTWARD
TO SIOUX FALLS SD. RADAR MOSAIC SHOWING BAND OF SCATTERED
SHOWERS/THUNDERSTORMS AHEAD OF THE FRONT FROM NEAR THE ARROWHEAD OF MN
INTO NORTHWEST WI AND EAST CENTRAL MN. RAP SHOWS THIS ACTIVITY WAS
ON THE EASTERN PERIPHERY OF FAIRLY DECENT AXIS OF 850MB MOISTURE
TRANSPORT. OTHERWISE...TEMPERATURES ACROSS THE FORECAST AREA AT 3 AM
WERE HOLDING IN THE UPPER 60S/LOWER 70S WITH DEWPOINTS IN THE MIDDLE
60S.
SUNDAY EVENING MODEL RUNS SHOWING FAIRLY DECENT AGREEMENT THROUGH
THE SHORT TERM PERIOD.
LOOK FOR THE MID-LEVEL SHORTWAVE AND ASSOCIATED SURFACE COLD FRONT
OVER MN TO SINK SLOWLY SOUTHEAST INTO THE AREA TODAY...WHILE
UNDERGOING SOME WEAKENING. RAP/NAM MODELS SHOWING BEST 850MB
MOISTURE TRANSPORT AHEAD OF THE TROUGH/FRONT PUSHING EAST OF THE
AREA BY LATER THIS MORNING. HOWEVER...MODELS FAIRLY PERSISTENT IN
PRODUCING SCATTERED SHOWERS AND THUNDERSTORM TODAY ACROSS THE
AREA...WITH BETTER CHANCES HEADED INTO THE AFTERNOON GIVEN PEAK
HEATING/HIGHER DEW POINT POOLING AND 0-3KM MUCAPE PEAKING IN THE
3000-5000J/KG RANGE WITH DOWNDRAFT CAPE IN THE 1500-2000J/KG RANGE.
UPPER LEVEL DYNAMICS HELP ALSO GIVEN RIGHT ENTRANCE REGION OF 300MB
JET PER THE NAM BY THIS AFTERNOON. MODEL SOUNDINGS SHOW INVERTED-V
AND ALTHOUGH 0-3KM BULK SHEAR FAIRLY LIMITED...DOWNDRAFT CAPE HAS ME
A BIT CONCERNED FOR DAMAGING WIND POTENTIAL. WILL HAVE TO KEEP A
VERY CLOSE EYE ON THINGS TODAY. OTHERWISE...ANOTHER UNSEASONABLY
WARM DAY ON TAP WITH HIGHS PUSHING INTO THE 80S ONCE AGAIN.
LOOKING FOR THE BULK OF THE SHOWERS/THUNDERSTORMS TO MOVE SOUTHEAST
OF THE AREA THIS EVENING...BUT THEN MODELS SHOWING ANOTHER MID-LEVEL
TROUGH PUSHING ACROSS THE PLAINS TOWARD THE AREA AFTER MIDNIGHT WITH
WEAK ISENTROPIC LIFT AND MOISTURE TRANSPORT. KEPT SMALLER 20-30 POP
SHRA/T CHANCE TO COVER THIS WEAKER SIGNAL.
GFS AND NAM HINTING AT SOME SORT OF WEAK TROUGH RIPPLING THROUGH
FAIRLY HIGH-ZONAL FLOW ALOFT ON TUESDAY WITH SOME MINOR TIMING
DIFFERENCES NOTED. GIVEN THIS RATHER NONDESCRIPT SIGNAL...WILL STICK
WITH SLIGHT CHANCE OF SHRA/TS.
A MORE VIGOROUS MID-LEVEL CLOSED LOW SWINGS EAST ACROSS SOUTHERN
CANADA TUESDAY NIGHT/WEDNESDAY WITH TROUGH AXIS AND ASSOCIATED
STRONG SURFACE COLD FRONT SWINGING EAST ACROSS THE AREA. THIS HAS BEEN A
RATHER CONSISTENT SIGNAL THE LAST FEW DAYS NOW...SO FEEL COMFORTABLE
WITH HIGHER-END CHANCE TO LIKELY SHRA/TS. GIVEN TIMING OF THE
FRONTAL PASSAGE THROUGH THE AREA WEDNESDAY MORNING...SEVERE THREAT
LOOKS TO BE SOUTHEAST OF THE AREA DURING THE AFTERNOON.
OTHERWISE...MODEL SOUNDINGS SHOWING GOOD MIXING/DRYING BEHIND THE
FRONT WEDNESDAY AFTERNOON ON BREEZY NORTHWEST WINDS IN THE 15 TO 30
MPH RANGE. TEMPERATURES WILL ALSO RETURN TO NEAR SEASONAL NORMALS IN
THE MID 70S TO LOWER 80S.
.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY
327 AM CDT MON SEP 3 2012
FAIRLY GOOD AGREEMENT BETWEEN THE GFS AND ECMWF IN THE WEDNESDAY
NIGHT THROUGH SATURDAY TIME FRAME. WEDNESDAY NIGHT/THURSDAY LOOK
COOLER AND DRY AS MID/UPPER LEVEL TROUGH SETTLES INTO THE AREA. LOWS
WEDNESDAY NIGHT EXPECTED TO FALL INTO THE UPPER 40S TO LOWER 50S WITH
HIGHS ON THURSDAY IN THE 70S. SHRA/TS CHANCES RETURN TO THE AREA
THURSDAY NIGHT THROUGH FRIDAY NIGHT AS AS ANOTHER MID-LEVEL TROUGH
DROPS THROUGH THE REGION WITH A REINFORCING SHOT OF COOLER AND MORE
AUTUMN-LIKE AIR. EXPECTING HIGHS ON FRIDAY IN THE UPPER 60S TO
MIDDLE 70S WITH LOWS IN THE UPPER 40S TO MIDDLE 50S. SATURDAY
CONTINUES TO BE COOL BUT DRY WITH HIGHS IN THE UPPER 60S AND LOWER
70S AFTER OVERNIGHT LOWS IN THE UPPER 40S TO LOWER 50S. APPEARS
SUNDAY WILL SEE SOME WARMING AS MID-LEVEL HEIGHTS BUILD IN RESPONSE
TO RIDGE BUILDING IN FROM THE PLAINS. LOOK FOR HIGHS IN THE LOWER TO
MIDDLE 70S.
&&
.AVIATION...THROUGH 06Z TUESDAY
1154 PM CDT SUN SEP 2 2012
00Z MPX SOUNDING SHOWS CAPPING INVERSION AROUND 800MB AND THUS
CONVECTION HASNT DEVELOPED AHEAD OF THE COLD FRONT. 03.00Z
ARXLAPS AND 03.01Z HRRR DOES SHOW SOME DEVELOPMENT LATE TONIGHT
AFTER 09Z...BUT KEEPS IT WEST OF THE TAF SITES AND THUS ONLY
EXPECTING SOME MID AND HIGH LEVEL CLOUDS AOA 12K FEET. SOUNDINGS
ALSO SHOWING GRADIENT REMAINING UP...ESPECIALLY JUST ABOVE THE
BOUNDARY LAYER. WINDS HAVE DECOUPLED AT KLSE...BUT BLUFF TOP WINDS
BLOWING AT AROUND 5 TO 10 KNOTS. DID KEEP SOME MVFR VISIBILITIES
IN LATE TONIGHT AS DEW POINT SPREADS ARE AROUND 7 DEGREES CELSIUS
AT 03Z. COLD FRONT PUSHES ACROSS THE AREA MONDAY AFTERNOON. 03.00Z
NAM DOES SHOW CONVECTION DEVELOPING OVER THE AREA...BUT BASED ON
FRONTAL POSITION MAY ONLY AFFECT KLSE. DID CONTINUE THE MENTION OF
THE VCSH AND LATER SHIFTS CAN REFINE. CEILINGS LOOK TO REMAIN IN
THE VFR CATEGORY...BUT CANNOT RULE OUT SOME IFR OR MVFR CEILINGS
IF STORMS IMPACT EITHER OF THE TAF SITES.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
327 AM CDT MON SEP 3 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...DAS
LONG TERM...DAS
AVIATION...RABERDING
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1154 PM CDT SUN SEP 2 2012
.SHORT TERM...TONIGHT THROUGH WEDNESDAY
239 PM CDT SUN SEP 2 2012
MAIN FORECAST CONCERNS ARE ON PRECIPITATION CHANCES THROUGHOUT AND
ANY SEVERE WEATHER POTENTIAL FOR MONDAY/LABOR DAY.
CURRENTLY AS OF 20Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED A DEEP UPPER LOW OVER SASKATCHEWAN....RIDGING OVER THE
WESTERN GREAT LAKES REGION...AND THE REMNANTS OF ISAAC IN SOUTHWEST
INDIANA. WITHIN THE SOUTHWEST FLOW BETWEEN THE UPPER LOW AND THE
RIDGING...A SHORTWAVE WAS PRESENT FROM LAKE WINNIPEG TO CENTRAL
SOUTH DAKOTA. THE COMBINATION OF DPVA AHEAD OF THIS SHORTWAVE AND
LOW TO MID LEVEL MOISTURE TRANSPORT SURGING NORTH HAS KEPT SOME
SHOWERS AND THUNDERSTORMS GOING OVER NORTHWEST MINNESOTA. THIS
MOISTURE TRANSPORT CAN BE SEEN IN SOME OF THE GOES DERIVED
PRECIPITABLE WATER IMAGERY...WHERE VALUES ARE IN THE 1-1.3 INCH
RANGE FROM EASTERN NEBRASKA INTO WESTERN MINNESOTA. ASSOCIATED WITH
THIS SHORTWAVE AT THE SURFACE IS A COLD FRONT THAT STRETCHES FROM
NORTH CENTRAL MINNESOTA BACK INTO SOUTHEAST SOUTH DAKOTA. OVER OUR
AREA...PLENTY OF SUNSHINE CONTINUES...THANKS TO DRY AIR PRESENT AS
SEEN ON THE 12Z MPX SOUNDING. MIXING FROM THE SUN COMBINED WITH
850MB TEMPS AROUND 18C PER 12Z SOUNDINGS ALLOWING TEMPERATURES TO
CLIMB INTO THE LOW TO MID 80S. SOME CUMULUS HAS FORMED OVER THE
SOUTHEAST HALF OF THE AREA...THOUGH...REFLECTIVE OF ISAAC MOISTURE
BEGINNING TO GET PULLED NORTHWEST AHEAD OF THE SHORTWAVE/FRONT. THAT
MOISTURE CAN BE SEEN TOO ON GOES PRECIPITABLE WATER IMAGERY.
TONIGHT AND MONDAY...THE SHORTWAVE SEEN OVER THE DAKOTAS IS PROGGED
TO PUSH EAST-NORTHEAST IN RESPONSE TO THE DEEP UPPER LOW IN CANADA
HEADING EAST. AS THE SHORTWAVE HEADS INTO THE RIDGE OVER THE
FORECAST AREA...IT LOOKS LIKE IT WILL WEAKEN...BUT COME THROUGH
NORTHERN SECTIONS OF THE FORECAST AREA AT A GOOD TIME FOR CONVECTIVE
INITIATION...I.E. MONDAY AFTERNOON. WITH THE SHORTWAVE WEAKENING...
SO DOES THE FRONT ASSOCIATED WITH IT. HOWEVER...ALSO OF INTEREST IS
MOST MODELS SHOWING A SHORTWAVE COMING OUT OF UTAH/COLORADO RIGHT
NOW. THIS SHORTWAVE GETS PICKED UP BY THE SOUTHWEST FLOW AND ENTERS
THE SOUTHERN PORTION OF THE FORECAST AREA DURING THE AFTERNOON. SO
ALTHOUGH THE SURFACE FRONTAL FEATURE IS WEAKENING...THERE ARE A
COUPLE OF AIDES ALOFT FOR CONVECTION. BEFORE DISCUSSING MONDAY
FURTHER...BACK TO TONIGHT. ANTICIPATING CONVECTIVE DEVELOPMENT ALONG
THE FRONT LATE THIS AFTERNOON OR DURING THE EVENING IN WESTERN
MINNESOTA. THIS ACTIVITY SHOULD WEAKEN OVERNIGHT WITH LOSS OF
HEATING...BUT SOME COULD LINGER AND SCRAPE THE NORTHWEST SECTION OF
THE FORECAST AREA VERY LATE IN THE NIGHT. CERTAINLY THE MOISTURE
TRANSPORT THROUGHOUT THE 925-700MB LAYER STAYING FOCUSED UP WELL TO
THE NORTH DOESNT HELP TO MAINTAIN CONVECTION. IT IS ENTIRELY
POSSIBLE MONDAY MORNING THAT NO PRECIPITATION IS AROUND...A BREAK
BETWEEN THE TONIGHT ACTIVITY DIMINISHING AND AFTERNOON ACTIVITY
STARTING UP. FOR THE AFTERNOON...BUILDING INSTABILITY WITH MLCAPES
OF 1000-2000 J/KG COMBINED WITH THE TWO SHORTWAVES SHOULD INITIATE
CONVECTION. IN FACT...THE ONE SHORTWAVE COMING FROM THE SOUTHWEST
MAY END UP HAVING MOST OF THE CONVECTION...AS NOTED BY THE 02.12Z
SPCWRF-NMM...HIRESW-ARW AND NAM. AS SUCH...HAVE INCREASED
PRECIPITATION CHANCES TO 50 PERCENT SOUTH OF I-90. REGARDING SEVERE
RISK...ONLY AREA OF CONCERN IS AHEAD OF THAT SHORTWAVE...WHERE
LOCALIZED 0-6KM SHEAR VALUES JUMP UP TO 25-30KT. OUTSIDE OF
THAT...0-3KM AND 0-6KM SHEAR VALUES ARE GENERALLY BELOW 20 KTS.
THEREFORE...THINKING MOST CONVECTION NORTH OF I-90 SHOULD STAY
SUB-SEVERE WHILE THERE COULD BE A RISK SOUTH OF I-90. FOR
TEMPERATURES...INCREASING SOUTHERLY FLOW AND CLOUDS WILL RESULT IN A
WARMER NIGHT TONIGHT. SOME CLOUDS AROUND ON MONDAY MAKE HIGHS A
LITTLE DIFFICULT...BUT WITH 850MB TEMPS STILL NEAR 18C AND SOME
SUN...HIGHS SHOULD AT LEAST GET BACK UP INTO THE LOW TO EVEN MID 80S.
MONDAY NIGHT AND TUESDAY...A WEST-SOUTHWEST 500MB FLOW CONTINUES...
AHEAD OF WHAT IS FORECAST TO BE A POTENT SHORTWAVE DROPPING DOWN
INTO SOUTH CENTRAL CANADA AND THE NORTHWEST DAKOTAS BY 00Z
WEDNESDAY. THERE ARE NO REAL DISCERNIBLE SHORTWAVES COMING
THROUGH THE FLOW AND IMPACTING THE FORECAST AREA ACCORDING TO THE
MODELS. LOOKING AT MOISTURE TRANSPORT AND ISENTROPIC LIFT
FIELDS...THERE IS NOTHING REALLY TO NOTE EITHER THAT SUGGEST
PRECIPITATION...AT LEAST FROM THE 02.12Z NAM/GFS. THEREFORE...ONCE
WHATEVER CONVECTION OCCURS MONDAY AFTERNOON PUSHES OFF TO THE
EAST...LIKELY EARLY IN THE EVENING...DRY CONDITIONS COULD OCCUR
RIGHT THROUGH TUESDAY. THIS IS A DEFINITE CHANGE FROM PREVIOUS
MODEL RUNS...EVEN THE 02.00Z ECMWF...WHICH HAD SOME BETTER
MOISTURE TRANSPORT AHEAD OF THAT POTENT SHORTWAVE COMING DOWN TO
INITIATE CONVECTION. FOR NOW WILL LOWER PRECIPITATION CHANCES INTO
THE 15-25 PERCENT RANGE...BUT FUTURE FORECASTS MAY BE ABLE TO PULL
THESE CHANCES ENTIRELY IF TRENDS CONTINUE. ANOTHER ITEM TO WATCH
IS FOG TUESDAY MORNING. IF SKIES CAN CLEAR OUT...DECOUPLING OF
WINDS AND ANY RAIN FROM MONDAY WOULD LEAD TO FOG DEVELOPMENT. DUE
TO UNCERTAINTY ON CLOUDS...HAVE LEFT OUT FOG. DESPITE THE
SHORTWAVE PASSAGE MONDAY EVENING...850MB TEMPS STAY WARM IN THE
18-20C RANGE THROUGH TUESDAY. IN ADDITION... DEWPOINTS DO NOT LOOK
TO DROP MUCH IF AT ALL. THEREFORE... ANTICIPATING SIMILAR LOW AND
HIGH TEMPERATURES TO TONIGHT AND MONDAY.
TUESDAY NIGHT AND WEDNESDAY...THAT POTENT SHORTWAVE TROUGH COMING
INTO THE NORTHWEST DAKOTAS LATE TUESDAY IS WELL AGREED UPON BY
MODELS TO MOVE OVER MINNESOTA BY 12Z WEDNESDAY...THEN CONTINUE ITS
FAST MOTION EAST AND REACH WESTERN LOWER MICHIGAN BY 00Z THURSDAY.
PRETTY STRONG FORCING THIS TROUGH...NOTED IN 500-300MB PV
FIELDS...THOUGH MOST OF IT STAYS NORTH OF THE FORECAST AREA. THERE
IS SOME MOISTURE TRANSPORT AND ISENTROPIC LIFT ACCOMPANYING THE
TROUGH...SO WITH THE WEAK HEIGHT FALLS IN OUR AREA WE SHOULD SEE
SOME PRECIPITATION MOVE THROUGH. MOST LIKELY TIME PERIOD APPEARS TO
OCCUR BETWEEN 06Z-18Z WEDNESDAY. PREVIOUS FORECAST PRECIPITATION
CHANCES REFLECT THIS WELL. STRONG ISENTROPIC DESCENT AND SUBSIDENCE
BEHIND THE TROUGH WILL ALLOW FOR DRYING AND CLEARING CONDITIONS
AFTER 18Z WEDNESDAY. THEREFORE...HAVE DRIED OUT THE FORECAST AREA
FOR THE AFTERNOON. NOTE...IT COULD ALSO BE PRETTY BREEZY IN THE
AFTERNOON AS PRESSURE GRADIENT BRIEFLY TIGHTENS...DEEP MIXING AND
COLD ADVECTION OCCUR. REGARDING TEMPERATURES...850MB TEMPS HOLD
BETWEEN 18-20C TUESDAY NIGHT...BUT ONCE THE FRONT MOVES THROUGH WITH
THE SHORTWAVE WEDNESDAY MORNING...THESE TEMPS FALL TO 10-12C BY 00Z
THURSDAY. STILL...HIGHS ON WEDNESDAY SHOULD BE ABLE TO TOP OUT IN
THE MID 70S TO LOW 80S WITH THE SUN IN THE AFTERNOON. WARM NIGHT
LIKELY TUESDAY NIGHT AHEAD OF THE FRONT AND RELATIVELY HIGH
DEWPOINTS.
.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY
239 PM CDT SUN SEP 2 2012
SURPRISINGLY...THE 02.12Z ECMWF/GFS/CANADIAN AND GFS ENSEMBLES ARE
ALL IN REALLY GOOD AGREEMENT WITH THE UPPER AIR AND SURFACE PATTERNS
THROUGH SATURDAY. SOME DIFFERENCES START TO SHOW UP ON SUNDAY...BUT
GIVEN THE AMPLIFICATION FORECAST TO OCCUR...IT IS SURPRISING TO SEE
THE GOOD AGREEMENT. THE LONG TERM PERIOD STARTS OFF WITH UPPER
TROUGHING OVER MUCH OF CENTRAL CANADA WITH A POTENT SHORTWAVE
DROPPING DOWN THROUGH ALBERTA. THIS SHORTWAVE ENDS UP CARVING OUT A
FAIRLY DEEP TROUGH AS IT DIGS SOUTHEAST...REACHING THE OHIO VALLEY
SATURDAY MORNING. AS THIS SHORTWAVE DIGS...A FRONTOGENESIS ZONE
LOOKS TO FORM ACROSS THE FORECAST AREA. THIS APPEARS TO OCCUR
THURSDAY NIGHT AND LASTS THROUGH FRIDAY NIGHT. OVERALL...THE BEST
MOISTURE AND FRONTOGENESIS FORCING STAYS SOUTH...THEREFORE
PRECIPITATION CHANCES ARE ONLY IN THE 20-30 RANGE. ON SATURDAY...
BOTH THE 02.00Z AND 02.12Z ECMWF END UP DEVELOPING A RELATIVELY
STRONG SURFACE LOW IN INDIANA...PARTIALLY CAUSED BY THE UPPER TROUGH
BEGINNING TO CLOSE OFF. THE 02.00Z ECMWF HAD DEFORMATION SHOWERS
INTO THE SOUTHEASTERN HALF OF THE FORECAST AREA FOR SATURDAY.
HOWEVER...THE NEW 02.12Z ECMWF HAS SHOVED THEM OFF TO THE EAST. FOR
NOW...JUST PLACED A 20 PERCENT CHANCE IN THE AREA AROUND GRANT
COUNTY. THE GFS AND CANADIAN ARE MOSTLY DRY. THE REST OF THE WEEKEND
AND GOING INTO EARLY NEXT WEEK WILL ALL HINGE ON WHAT HAPPENS WITH
THE UPPER TROUGH/LOW. THE NEW 02.12Z ECMWF KEEPS IT OVER
INDIANA...LIKE SOME OF THE 02.12Z GFS ENSEMBLES. THE 02.12Z GFS HAS
IT MORE PROGRESSIVE. EITHER SOLUTION LOOKS DRY FOR THE FORECAST
AREA...BUT CLOUDS AND TEMPERATURES WOULD BE GREATLY AFFECTED...WITH
THE FARTHER WEST SOLUTION HOLDING MORE CLOUDS AND COOLER AIR IN THE
FORECAST AREA. SOME OF THE MOVEMENT OF THE UPPER TROUGH/LOW WILL
DEPEND ON TROPICAL STORM LESLIE WHICH IS FORECAST TO MOVE THROUGH
THE WESTERN ATLANTIC AND STRENGTHEN...LIKELY BLOCKING UP THE FLOW.
REGARDING TEMPERATURES...THEY WILL BE ON THE COOL DOWN AS THE UPPER
TROUGH FORMS. 850MB TEMPS FALL FROM THE 10-12C ON THURSDAY TO 6-8C
ON SATURDAY. AS SUCH...HIGHS ARE ONLY FORECAST TO PERHAPS REACH 70
ON SATURDAY. SATURDAY NIGHT COULD BE QUITE COOL...DEPENDING ON
CLOUDS...WITH HIGH PRESSURE POSSIBLY MOVING IN AT THE SURFACE FROM
THE NORTHWEST. SOME SLIGHT REBOUND IN TEMPERATURES ARE ANTICIPATED
ON SUNDAY.
&&
.AVIATION...THROUGH 06Z TUESDAY
1154 PM CDT SUN SEP 2 2012
00Z MPX SOUNDING SHOWS CAPPING INVERSION AROUND 800MB AND THUS
CONVECTION HASNT DEVELOPED AHEAD OF THE COLD FRONT. 03.00Z
ARXLAPS AND 03.01Z HRRR DOES SHOW SOME DEVELOPMENT LATE TONIGHT
AFTER 09Z...BUT KEEPS IT WEST OF THE TAF SITES AND THUS ONLY
EXPECTING SOME MID AND HIGH LEVEL CLOUDS AOA 12K FEET. SOUNDINGS
ALSO SHOWING GRADIENT REMAINING UP...ESPECIALLY JUST ABOVE THE
BOUNDARY LAYER. WINDS HAVE DECOUPLED AT KLSE...BUT BLUFF TOP WINDS
BLOWING AT AROUND 5 TO 10 KNOTS. DID KEEP SOME MVFR VISIBILITIES
IN LATE TONIGHT AS DEW POINT SPREADS ARE AROUND 7 DEGREES CELSIUS
AT 03Z. COLD FRONT PUSHES ACROSS THE AREA MONDAY AFTERNOON. 03.00Z
NAM DOES SHOW CONVECTION DEVELOPING OVER THE AREA...BUT BASED ON
FRONTAL POSITION MAY ONLY AFFECT KLSE. DID CONTINUE THE MENTION OF
THE VCSH AND LATER SHIFTS CAN REFINE. CEILINGS LOOK TO REMAIN IN
THE VFR CATEGORY...BUT CANNOT RULE OUT SOME IFR OR MVFR CEILINGS
IF STORMS IMPACT EITHER OF THE TAF SITES.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
239 PM CDT SUN SEP 2 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM...AJ
AVIATION...RABERDING
AREA FORECAST DISCUSSION
NWS SAN JOAQUIN VALLEY - HANFORD CA
120 AM PDT WED SEP 5 2012
.SYNOPSIS...
MOISTURE FROM THE TROPICS WILL STREAM INTO THE REGION THROUGH
THURSDAY PRODUCING ISOLATED SHOWERS AND THUNDERSTORMS TO PARTS OF
THE AREA. BY FRIDAY, DRIER AIR WILL MOVE IN FROM THE WEST,
BRINGING AN END TO THE THUNDERSTORM THREAT.
&&
.DISCUSSION...I VERY COMPLICATED PATTERN THIS MORNING TO SAY THE
LEAST. SATELLITE IMAGERY SHOWS ONE OF THE MORE PRONOUNCED INFLUXES
OF TROPICAL MOISTURE INTO SOUTHERN CALIFORNIA IN QUITE A WHILE. OF
NOTE IS THE WIND SHEAR DEPICTED BY LOWER LEVEL CLOUDS MOVING
NORTHWEST ON SOUTHEAST WINDS WHILE THE MAIN CLOUD AND MOISTURE
LAYER MOVES NORTHEAST ON SOUTHWEST WINDS. IF THIS ISN`T ENOUGH
DIRECTIONS TO MAKE YOU DIZZY I DON`T KNOW WHAT WILL! ANYWAY, THE
MAIN MOISTURE FEED IS COMING FROM THE REMNANTS OF TROPICAL SYSTEM
JOHN AND PER THE SAN DIEGO SOUNDING THE LAYER IS RATHER DEEP,
EXTENDING FROM AROUND 9000 FEET AT THE BOTTOM TO AROUND 16000
FEET AT THE TOP. THE MAIN FORECAST PROBLEM IS JUST HOW FAR NORTH
THIS MOISTURE RICH BAND WILL MIGRATE AND THE ASSOCIATED THREAT OF
ELEVATED CONVECTION AS WELL AS THE THREAT OF RAIN SHOWERS OVER THE
ENTIRE CENTRAL CALIFORNIA INTERIOR.
IN THE VERY SHORT TERM, THE RUC13 MATCHES UP WELL WITH THE SAN
DIEGO SOUNDING IN SHOWING THE MOISTURE SITTING JUST ABOVE 700 MB.
THE RUC TRANSPORT WINDS AT 700 MB ARE PRONOUNCED SOUTHEAST AND IF
MOISTURE WAS ABUNDANT AT THIS LEVEL THE ADVECTION INTO CENTRAL
CALIFORNIA WOULD BE SIMPLE. GIVEN THAT THE DEEPER MOISTURE LIES
ABOVE 700 MB FOR TODAY THE PROBLEM IS GETTING THIS DEEPER MOISTURE
NORTHWARD INTO THE FORECAST AREA FOR ANY CONVECTIVE THREAT.
WATER VAPOR IMAGERY SHOWS SOME INTERESTING THINGS OCCURRING OFF OF
THE CENTRAL COAST. IT APPEARS A BAROCLINIC LEAF IS DEVELOPING AND
A BACKING OF THE FLOW FROM THE WEST TO THE SOUTH IS OCCURRING.
THIS WILL HELP TO PULL THE MID LEVEL MOISTURE FROM SOUTH OF POINT
CONCEPTION NORTHWARD AND LIFT THE SOUTHWEST FLOW "MOISTURE FETCH"
(REMEMBER ALL SOUTHWEST FLOW IS NOT DRY) WELL INTO CENTRAL
CALIFORNIA BY TONIGHT. FOR THURSDAY FORECAST MODELS ARE NOW
BRINGING MUCH MORE MOISTURE INTO CENTRAL CALIFORNIA WITH THE BRUNT
MOVING UP THE COASTAL RANGE AND WEST SIDE OF THE FORECAST AREA.
WILL OPT TO INTRODUCE THE CHANCE OF THUNDERSTORMS TO EVEN THE SAN
JOAQUIN VALLEY TONIGHT AND CONTINUE THROUGH THURSDAY. GIVEN THE
TREND OF MODELS TO HOLD ON TO THE MOISTURE INTO FRIDAY.
TEMPERATURES WILL BE HIGHLY DEPENDENT ON CLOUD COVER SO WILL
LIKELY HAVE ISSUES PINNING DOWN MAX TEMPS FOR THE NEXT COUPLE OF
DAYS. WILL GIVE IT MY BEST SHOT AND SEE HOW IT GOES.
WITH THIS FRONT LOADED FORECAST, A QUICK GLIMPSE INTO NEXT WEEK
SHOWS A RIDGE THAT JUST DOESN`T WANT TO GIVE UP. MAYBE SOME
COOLING BY MID WEEK BUT I AM NOT THAT CONFIDENT.
&&
.AVIATION...
ISOLATED THUNDERSTORMS ARE POSSIBLE IN THE MOUNTAINS THIS AFTERNOON
AND TONIGHT IN ADDITION TO THE FOOTHILLS WEST OF INTERSTATE 5 AND
THE KERN COUNTY DESERT. OTHERWISE...VFR CONDITIONS WILL PREVAIL
ACROSS THE CENTRAL CALIFORNIA INTERIOR UNTIL 12Z THURSDAY.&&
.AIR QUALITY ISSUES...
ON WEDNESDAY SEPTEMBER 5 2012... UNHEALTHY FOR SENSITIVE GROUPS IN
FRESNO AND KERN COUNTIES AND SEQUOIA NATIONAL PARK AND FOREST.
FURTHER INFORMATION IS AVAILABLE AT VALLEYAIR.ORG
&&
.CERTAINTY...
THE LEVEL OF CERTAINTY FOR DAYS 1 AND 2 IS LOW.
THE LEVEL OF CERTAINTY FOR DAYS 3 THROUGH 7 IS MEDIUM.
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.
&&
.HNX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
PUBLIC...DUDLEY
AVN/FW...DURFEE
SYNOPSIS...WP
WEATHER.GOV/HANFORD
AREA FORECAST DISCUSSION
NWS SAN JOAQUIN VALLEY - HANFORD CA
931 PM PDT TUE SEP 4 2012
.SYNOPSIS...
MOISTURE FROM THE TROPICS WILL STREAM INTO THE REGION THROUGH
THURSDAY PRODUCING ISOLATED SHOWERS AND THUNDERSTORMS TO PARTS OF
THE AREA. BY FRIDAY, DRIER AIR WILL MOVE IN FROM THE WEST,
BRINGING AN END TO THE THUNDERSTORM THREAT.
&&
.DISCUSSION...
NO UPDATE THIS EVE. MID LEVEL MOISTURE...PARTIALLY FROM THE
REMNANTS OF FORMER TS/S ILEANA AND JOHN...ARE VERY SLOWLY WORKING
N-NE. ISOLD CONVECTION IN THE SRN SIERRA THIS AFTN SHOULD REPEAT
WED. SEVERAL SITES IN THE SJV AND HIGH DESERT RECORDED AFTN HIGHS
OF 100(+) TODAY. LITTLE CHANGE EXPECTED WED...THO THERE COULD BE
A FEW MORE CLOUDS TO HOLD TEMPS UNDER 100. THATS A BIG IFFF.
NOT A CONFIDENCE BUILDING UPPER LEVEL PATTERN ACROSS CENTRAL
CA...AS REGION IS LOCKED BETWEEN THE LARGE DOMINANT E-W RIDGE
STRADDLING THE U.S./MEX BRDR FROM TX TO SOCAL...AND A SEEMINGLY
PERMANENT LOW OFF THE NORCAL COAST. THE FCST PROBLEM IS WHERE WILL
THE DRY/MOIST INTERFACE BE WITH TIME...AND PRECIP/NO PRECIP LINE.
&&
.PREV DISCUSSION... /ISSUED 324 PM PDT TUE SEP 4 2012/
SCT TO BKN CLOUDS ACROSS THE CENTRAL SJV AND INTO THE TULARE
COUNTY MOUNTAINS TODAY. TEMPERATURES ACROSS THE SJV ARE
APPROACHING THE CENTURY MARK IN A FEW LOCATIONS. NO PRECIP HAS
BEEN REPORTED WITH THE CLOUD COVER THIS AFTERNOON IN THE VALLEY
AND ONLY A FEW HUNDREDTHS IN THE TULARE COUNTY FOOTHILLS AND
MOUNTAINS.
THE FORECAST CALLS FOR PARTLY CLOUDY SKIES TONIGHT OVER THE
CENTRAL CA INTERIOR. VISIBLE SATELLITE IMAGERY INDICATES A LINE OF
SHOWERS OFF THE NRN BAJA COAST THAT IS MOVING NORTH. SOME SHOWERS
HAVE DEVELOPED IN THE SOUTH LAND THIS AFTERNOON. THE KERN DESERT
AND MOUNTAINS REMAIN RAIN FREE THIS AFTERNOON AS RUC SHOWS STABLE
ATMS. A FEW LIGHTNING STRIKES ARE OCCURRING IN THE FRESNO COUNTY
MOUNTAINS ATTM AS A CLUSTER OF STORMS QUICKLY MOVES EAST.
SW FLOW ALOFT IS FORECAST TO CONTINUE THIS WEEK WITH RISING
HEIGHTS AND TEMPERATURES CONTINUING ABOVE NORMAL THROUGH THE
WEEKEND. THE UPPER RIDGE WILL MOVE INTO SRN CA BY SAT AND REMAIN
THERE UNTIL MONDAY BEFORE IT DRIFTS BACK TO THE EAST AS ANOTHER
SURGE OF MOISTURE APPROACHES THE AREA BY NEXT TUESDAY. THE ECMWF
IS MORE AGGRESSIVE WITH THE MOISTURE ON NEXT TUESDAY THAN THE GFS.
&&
.AVIATION...
VFR CONDITIONS WILL PREVAIL ACROSS THE CENTRAL CALIFORNIA INTERIOR
THROUGH 18Z WED. AFTER 18Z WED...A SLIGHT CHANCE OF THUNDERSTORMS
WILL BEGIN DEVELOPING OVER THE COAST RANGE...SOUTHERN SIERRA
NEVADA...TEHACHAPI RANGE AND KERN COUNTY DESERTS AND CONTINUE THRU
06Z THU.
&&
.AIR QUALITY ISSUES...
ON WEDNESDAY SEPTEMBER 5 2012... UNHEALTHY FOR SENSITIVE GROUPS IN
FRESNO AND KERN COUNTIES AND 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 LOW.
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.
&&
.HNX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
PUBLIC...BINGHAM
AVN/FW...DS
SYNOPSIS...WP
WEATHER.GOV/HANFORD
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
218 AM CDT WED SEP 5 2012
.MESOSCALE DISCUSSION...
728 PM CDT
CLOSELY MONITORING CONVECTION OVER WESTERN WISCONSIN EARLY THIS
EVENING FOR ANY POTENTIAL IMPACTS ON OUR CWA TONIGHT. CLUSTER OF
STRONG TO SEVERE THUNDERSTORMS OVER SOUTHWEST WISCONSIN APPEARS TO
BE CONGEALING IN A LARGE MASS OF STORMS WHICH COULD RESULT IN
FORMATION OF COLD POOL AND A MORE ACCELERATED MOTION. FORWARD
PROPAGATING CORFIDI VECTORS FROM WRF-NAM AND RUC BOTH SUGGEST
CONVECTION WOULD RACE QUICKLY EAST-SOUTHEAST TOWARD CHGO
METRO...HOWEVER SPC OBJECTIVE MESOANALYSIS DATA SHOWS A REGION OR
MUCH LESSER INSTABILITY AND GREATER INHIBITION OVER SOUTHERN
WISCONSIN. VISIBLE SATELLITE IMAGERY TUES AFTERNOON SHOWED A
DISTINCT ABSENCE OF CUMULUS IN A SWATH FROM NE IL (AHEAD OF LAKE
BREEZE) NNW INTO CENTRAL WISCONSIN...WHICH WOULD LEND SOME CREDENCE
TO THE WEAKER INSTABILITY/STRONGER CAPPING SHOWN IN THE SPC
OBJECTIVE ANALYSIS DATA.
RELATIVELY WEAK LOW LEVEL FLOW SUGGESTS ANY RAPID NORTHEASTWARD
TRANSPORT OF MOISTURE OR INSTABILITY IS UNLIKELY THIS EVENING...SO
WOULD ANTICIPATE CONVECTION TO WEAKEN AS IT PROGRESSES EASTWARD INTO
THE LESS UNSTABLE ENVIRONMENT OVER SOUTHERN WISCONSIN. LOOKING LIKE
A MORE PLAUSIBLE SCENARIO WOULD BE FOR MOST INTENSE VIGOROUS
CONVECTION TO FAVOR THE WESTERN PORTIONS OF THIS DEVELOPING MCS AND
FOR THE STRONGER CELLS TO TEND TO PROPAGATE MORE SOUTHWARD INTO THE
AXIS OF GREATER MOISTURE/INSTABILITY WHICH WAS NICELY DEPICTED BY
THE CUMULUS FIELD THIS AFTERNOON. MODELS REALLY NOT SHOWING ANY
SIGNIFICANT LOW LEVEL JET OR LOW LEVEL WARM AIR ADVECTION OVERNIGHT
SO ITS QUESTIONABLE HOW WELL SUSTAINED THIS CONVECTION WILL BE INTO
THE MID TO LATE EVENING...BUT REGARDLESS GIVEN ITS ALREADY RATHER
CLOSE PROXIMITY FEEL SOME UPWARD ADJUSTMENTS TO POP GRIDS FOR
TONIGHT ARE WARRANTED...ESPECIALLY WESTERN CWA.
IZZI
&&
.DISCUSSION...
307 PM CDT
MAIN FORECAST CONCERN FOR THE NEXT FEW DAYS WILL FOCUS ON THE
INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS TONIGHT AND
TOMORROW ASSOCIATED WITH A COLD FRONT DROPPING SEWD OUT OF THE UPPER
MISSISSIPPI VALLEY.
FOR THE REMAINDER OF THE AFTERNOON AND THIS EVENING...CONDITIONS
WILL REMAIN GENERALLY QUIET...HOWEVER...WITH AMPLE LOW LEVEL
MOISTURE LINGERING OVER THE REGION FOLLOWING THE PASSAGE OF TROPICAL
CYCLONE ISAAC...DAYTIME WARMING COMBINED WITH A LAKE BREEZE BOUNDARY
PUSHING INLAND FROM LAKE MICHIGAN WILL ALLOW FOR AT LEAST A SMALL
CHANCE OF SHOWERS OR THUNDERSTORMS OVER THE AREA THROUGH EARLY THIS
EVENING.
FOR THE LARGER SCALE...A PERSISTENT POLAR LOW CONTINUES TO SIT AND
SPIN OVER NRN MANITOBA WHILE A SERIES OF WEAK IMPULSES TRACK ALONG
THE SRN PERIPHERY. INITIALLY...THE SFC PRESSURE PATTERN REMAINS
VERY DIFFUSE WITH LITTLE SFC FORCING. HOWEVER...BY LATE
TONIGHT...THE SHORT RANGE GUIDANCE IS IN GOOD AGREEMENT ON
INCREASING THE PCPN THREAT AS A STRONG SHORTWAVE DROPS OUT OF THE
NORTHERN ROCKIES AND PUSHES INTO THE NORTHERN PLAINS TONIGHT AND
ACROSS THE UPPER MISSISSIPPI VALLEY TOMORROW. THIS SHORT WAVE WILL
REINFORCE A WEAK SFC COLD FRONT...WHICH WILL PROVIDE THE SFC FORCING
TO IGNITE THUNDERSTORMS. THE MAIN FORECAST CONCERN WITH THIS SYSTEM
WILL BE HOW FAR SOUTH TO EXTEND THE HIGHER POPS THROUGH THE MIDWEST
AND INTO THE MIDDLE MISSISSIPPI VALLEY. WHILE THE STRONGEST FORCING
SHOULD REMAIN TO THE NORTH OF THE LOCAL AREA IN WISCONSIN WITH THE
TRACK OF THE MAIN VORT MAX...THERE SHOULD BE ENOUGH UPPER LEVEL
FORCING EXTENDING SWD...COINCIDENT WITH THE SFC COLD FRONT TO
WARRANT KEEPING LIKELY POPS ACROSS THE CWA BEGINNING EARLY TOMORROW
MORNING OVER THE ROCKFORD AREA AND THEN SPREADING EWD THROUGH THE
DAY AS THE COLD FRONT PUSHES EWD. THE WARM SECTOR ENVIRONMENT
SHOULD BE PRIMED FOR THUNDERSTORMS BY LATE MORNING/EARLY AFTERNOON
AS TEMPERATURES SHOULD REACH INTO THE UPPER 80S TO CLOSE TO 90
DEGREES WITH SFC DEW POINTS IN THE UPPER 60S TO LOWER 70S. DEEP
LAYER INSTABILITY WILL ALSO BE MORE THAN ADEQUATE FOR THUNDERSTORM
DEVELOPMENT AS IS EVIDENCED BY BUFKIT SOUNDS FROM THE NAM12
ADVERTISING CAPE VALUES EXCEEDING 1500 J/KG BY THE LATE MORNING
HOURS AND INCREASING TO ARND 2500 J/KG DURING THE AFTERNOON. THE
GIVEN THE ELEMENTS EXPECTED TO BE IN PLACE TOMORROW...THE ;LATEST
SPC DAY 2 OUTLOOK KEEPS THE CWA IN A SLIGHT RISK AREA FOR SEVERE
THUNDERSTORMS. THE GREATEST THREAT SHOULD BE DURING THE LATE
AFTERNOON HOURS AS THE COLD FRONT CROSSES THE AREA DURING THE TIME
OF PEAK HEATING. THE MAIN SEVERE THREAT SHOULD BE STRONG...DAMAGING
STRAIGHT LINE WINDS GIVEN A RELATIVELY DRY LAYER EXPECTED BETWEEN
850MB-700MB...THOUGH THERE MAY ALSO BE A LARGE HAIL THREAT AS COOLER
AIR MOVES IN ALOFT WITH FREEZING LEVELS DROPPING TO ARND 12KFT.
LOCALLY HEAVY RAINFALL WILL BE LESS OF A CONCERN AS THE COLD FRONT
WILL BE PROGRESSIVE THROUGH THE DAY AND PWATS ARE EXPECTED TO BE 1.5
INCHES OR LESS.
THURSDAY IS SHAPING UP TO BE DRY AND THE NEXT CHANCE FOR PCPN WILL
COME BY EARLY FRIDAY MORNING AS A LONG WAVE TROUGH DROPS INTO THE
UPPER MISSISSIPPI VALLEY. A WEAK FRONT ASSOCIATED WITH THE UPPER
TROUGH IS EXPECTED TO MOVE INTO NWRN IL EARLY FRIDAY...BUT THE MAIN
CONCERN WILL BE SFC WAVE DEVELOPMENT ALONG THE COLD FRONT. THE
LONGER RANGE GUIDANCE IS IN GOOD AGREEMENT ON THE FORMATION OF A
DECENT SFC WAVE ON THE FRONT...BUT THERE IS LESSER AGREEMENT ON THE
STRENGTH AND LOCATION OF THE SFC WAVE DEVELOPMENT. HOWEVER...THERE
IS ENOUGH CONFIDENCE TO CARRY LIKELY POPS FOR THE SRN PORTIONS OF
THE CWA...WITH A CHANCE OF THUNDERSTORMS...BUT LESSER CONFIDENCE TO
THE NORTH...SO WILL ONLY CARRY CHANCE POPS FOR THE NORTHERN PORTIONS
OF THE CWA.
FOR TEMPERATURES...FOLLOWING THE PASSAGE OF THE COLD FRONT
TOMORROW...HIGHS WILL DROP BACK INTO UPPER 70S TO LOWER 80S FOR
THURSDAY. FOR FRIDAY AND SATURDAY...AS THE LONG WAVE UPPER TROUGH
MOVES ACROSS THE REGION...HIGHS SHOULD ONLY BE IN THE MIDDLE 70S FOR
FRIDAY/ THE COOLEST AIR WILL MOVE OVER THE AREA FOR THE WEEKEND
WITH TEMPS ONLY REACHING INTO THE UPPER 60S TO AROUND 70F ON
SATURDAY AND THE LOWER 70S FOR SUNDAY. WEAK UPPER RIDGING SHOULD
RETURN TO THE AREA BY EARLY NEXT WEEK...BRINGING SLIGHTLY WARMER
WEATHER WITH HIGHS IN THE MIDDLE 70S.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* CHANCE FOR SHRA/TSRA AFTER SUNRISE.
* CHANCE FOR TSRA THIS AFTERNOON.
* POTENTIAL FOR GUSTY SOUTH/SOUTHWEST WINDS. CMS
//DISCUSSION...UPDATED 06Z...
LINE OF TSRA CONTINUES TO WEAKEN AS IT MOVES SOUTHEAST OF THE
TERMINALS WITH SHOWERS EXPECTED TO END OVER THE CHICAGO AREA
TERMINALS IN THE NEXT 1-2 HRS. A SMALL SCALE HIGH PRESSURE HAS
FORMED ON THE BACK SIDE OF THE PRECIPITATION. AS A RESULT...
WINDS WILL TURN NORTHEAST...EAST...SOUTHEAST THEN BACK LIGHT
SOUTHERLY OVER THE NEXT FEW HOURS AS THIS HIGH MOVES SOUTHEAST.
SPEEDS LIKELY TO BE IN THE 10-15 KT RANGE WITH HIGHER GUSTS
POSSIBLE BUT THE OVERALL TREND WILL BE FOR SPEEDS TO SLOWLY
DIMINISH.
FOCUS THEN SHIFTS TO A LINE OF TSRA NOW MOVING ACROSS NORTH
CENTRAL IA AND SOUTHERN MN. SHORT TERM GUIDANCE WOULD SUGGEST THIS
LINE WILL CONTINUE MOVING EAST AND SHOULD BEGIN TO WEAKEN AFTER
SUNRISE. WHILE THE BULK OF THIS ACTIVITY MAY MOVE ACROSS SOUTHERN
WI...HAVE OPTED TO INCLUDE A TEMPO FOR TSRA AT RFD AND SHRA AT DPA
AND TRENDS WILL NEED TO BE MONITORED EARLY THIS MORNING WITH TSRA
POSSIBLY NEEDED TO BE ADDED FOR THE CHICAGO TERMINALS AFTER
SUNRISE. THIS ACTIVITY MAY THEN AFFECT ANY ADDITIONAL TSRA
DEVELOPMENT LATER THIS AFTERNOON WITH A POSSIBLE OUTFLOW PUSHING
SOUTH ACROSS THE TERMINALS DURING THE MORNING AND BECOMING THE
FOCUS FOR NEW DEVELOPMENT...WELL AHEAD OF THE COLD FRONT WITH
PERHAPS WEAKER CONVECTION DEVELOPING WITH THE FRONT. AT THIS
POINT...CONFIDENCE IS TOO LOW TO MAKE ANY SIGNIFICANT CHANGES AND
HAVE MAINTAINED PREVIOUS TSRA TIMING FOR THIS AFTERNOON. IF
CONVECTION DOES MATERIALIZE...STRONG/GUSTY WINDS WILL BE
POSSIBLE.
UNCERTAINTY ALSO REMAINS REGARDING HOW STRONG SOUTH/SOUTHWEST
WINDS WILL BECOME LATER THIS MORNING INTO THIS AFTERNOON AS WELL.
NEWEST FORECAST SOUNDINGS WOULD SUGGEST LOW LEVEL WINDS WILL NOT
BE QUITE AS STRONG AS PREVIOUSLY THOUGHT...BUT GUSTS TO 20 KTS
STILL POSSIBLE IN THE AFTERNOON. CMS
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* LOW CONFIDENCE REGARDING POTENTIAL SHRA/TSRA AFTER SUNRISE.
* MEDIUM CONFIDENCE REGARDING TSRA THIS AFTERNOON...LOW CONFIDENCE
REGARDING TIMING/DURATION.
* MEDIUM CONFIDENCE REGARDING WIND SPEEDS/DIRECTIONS THROUGH THE
PERIOD...LOW CONFIDENCE REGARDING GUSTS. CMS
//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...
* THURSDAY...VFR.
* FRIDAY THROUGH SATURDAY...CHANCE OF SHRA. MVFR POSSIBLE.
* SUNDAY...SLIGHT CHANCE OF SHRA.
* MONDAY...VFR.
&&
.MARINE...
217 AM CDT
THE WINDS EARLY THIS MORNING ACROSS THE SOUTHERN HALF OF THE LAKE
HAVE BEEN AFFECTED BY THE OVERNIGHT CONVECTION. THIS HAS LEAD TO THE
DEVELOPMENT OF A SMALLER SCALE AREA OF SURFACE HIGH PRESSURE ACROSS
THE SOUTHERN TIP OF THE LAKE. THE RESULT OF THIS HAS BEEN VARYING
WIND DIRECTIONS...WITH PRIMARILY A NORTHWESTERN WIND UP TO 30 KT
ACROSS THE NEAR SHORES OF INDIANA AND THE OPEN WATERS.
HOWEVER...ACROSS THE ILLINOIS NEAR SHORES THE WINDS HAVE BECOME
EASTERLY ON THE BACK SIDE OF THE HIGH. I EXPECT THE WIND SPEED TO
SUBSIDE THROUGH THE EARLY MORNING HOURS AND THE PRIMARILY DIRECTION
SHOULD BECOME SOUTHERLY DURING THE MORNING.
THE MAIN CONCERN FOR TODAY WILL BE THE THREAT FOR ADDITIONAL
THUNDERSTORMS...WITH A VERY GOOD CHANCE OF SEVERE WEATHER WITH WINDS
OVER 50 KT. THIS WILL OCCUR AHEAD OF A COLD FRONT THAT SHOULD PASS
ACROSS THE LAKE BY EARLY THIS EVENING. THIS WILL SWITCH THE WINDS
OUT OF THE NORTH NORTHWEST AROUND 20 KT OVERNIGHT TONIGHT. THE WINDS
SHOULD GRADUALLY ABATE DURING THE DAY ON THURSDAY AS SURFACE HIGH
PRESSURE BUILDS ACROSS THE LAKE.
THE NEXT SYSTEM OF CONCERN LOOKS TO OCCUR LATER FRIDAY AND INTO THE
WEEKEND. THERE REMAINS UNCERTAINTY ON HOW STRONG THIS SYSTEM WILL
GET...AND THUS THE WIND FORECAST REMAINS A BIT UNCERTAIN DURING THIS
TIME. HOWEVER...IT DOES APPEARS THAT A PERIOD OF STRONGER NORTHERLY
WINDS UP TO 30 KT ARE POSSIBLE LATE FRIDAY NIGHT INTO SATURDAY AS
SURFACE LOW PRESSURE TAKES SHAPE ACROSS THE OHIO VALLEY.
KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1253 AM CDT WED SEP 5 2012
.MESOSCALE DISCUSSION...
728 PM CDT
CLOSELY MONITORING CONVECTION OVER WESTERN WISCONSIN EARLY THIS
EVENING FOR ANY POTENTIAL IMPACTS ON OUR CWA TONIGHT. CLUSTER OF
STRONG TO SEVERE THUNDERSTORMS OVER SOUTHWEST WISCONSIN APPEARS TO
BE CONGEALING IN A LARGE MASS OF STORMS WHICH COULD RESULT IN
FORMATION OF COLD POOL AND A MORE ACCELERATED MOTION. FORWARD
PROPAGATING CORFIDI VECTORS FROM WRF-NAM AND RUC BOTH SUGGEST
CONVECTION WOULD RACE QUICKLY EAST-SOUTHEAST TOWARD CHGO
METRO...HOWEVER SPC OBJECTIVE MESOANALYSIS DATA SHOWS A REGION OR
MUCH LESSER INSTABILITY AND GREATER INHIBITION OVER SOUTHERN
WISCONSIN. VISIBLE SATELLITE IMAGERY TUES AFTERNOON SHOWED A
DISTINCT ABSENCE OF CUMULUS IN A SWATH FROM NE IL (AHEAD OF LAKE
BREEZE) NNW INTO CENTRAL WISCONSIN...WHICH WOULD LEND SOME CREDENCE
TO THE WEAKER INSTABILITY/STRONGER CAPPING SHOWN IN THE SPC
OBJECTIVE ANALYSIS DATA.
RELATIVELY WEAK LOW LEVEL FLOW SUGGESTS ANY RAPID NORTHEASTWARD
TRANSPORT OF MOISTURE OR INSTABILITY IS UNLIKELY THIS EVENING...SO
WOULD ANTICIPATE CONVECTION TO WEAKEN AS IT PROGRESSES EASTWARD INTO
THE LESS UNSTABLE ENVIRONMENT OVER SOUTHERN WISCONSIN. LOOKING LIKE
A MORE PLAUSIBLE SCENARIO WOULD BE FOR MOST INTENSE VIGOROUS
CONVECTION TO FAVOR THE WESTERN PORTIONS OF THIS DEVELOPING MCS AND
FOR THE STRONGER CELLS TO TEND TO PROPAGATE MORE SOUTHWARD INTO THE
AXIS OF GREATER MOISTURE/INSTABILITY WHICH WAS NICELY DEPICTED BY
THE CUMULUS FIELD THIS AFTERNOON. MODELS REALLY NOT SHOWING ANY
SIGNIFICANT LOW LEVEL JET OR LOW LEVEL WARM AIR ADVECTION OVERNIGHT
SO ITS QUESTIONABLE HOW WELL SUSTAINED THIS CONVECTION WILL BE INTO
THE MID TO LATE EVENING...BUT REGARDLESS GIVEN ITS ALREADY RATHER
CLOSE PROXIMITY FEEL SOME UPWARD ADJUSTMENTS TO POP GRIDS FOR
TONIGHT ARE WARRANTED...ESPECIALLY WESTERN CWA.
IZZI
&&
.DISCUSSION...
307 PM CDT
MAIN FORECAST CONCERN FOR THE NEXT FEW DAYS WILL FOCUS ON THE
INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS TONIGHT AND
TOMORROW ASSOCIATED WITH A COLD FRONT DROPPING SEWD OUT OF THE UPPER
MISSISSIPPI VALLEY.
FOR THE REMAINDER OF THE AFTERNOON AND THIS EVENING...CONDITIONS
WILL REMAIN GENERALLY QUIET...HOWEVER...WITH AMPLE LOW LEVEL
MOISTURE LINGERING OVER THE REGION FOLLOWING THE PASSAGE OF TROPICAL
CYCLONE ISAAC...DAYTIME WARMING COMBINED WITH A LAKE BREEZE BOUNDARY
PUSHING INLAND FROM LAKE MICHIGAN WILL ALLOW FOR AT LEAST A SMALL
CHANCE OF SHOWERS OR THUNDERSTORMS OVER THE AREA THROUGH EARLY THIS
EVENING.
FOR THE LARGER SCALE...A PERSISTENT POLAR LOW CONTINUES TO SIT AND
SPIN OVER NRN MANITOBA WHILE A SERIES OF WEAK IMPULSES TRACK ALONG
THE SRN PERIPHERY. INITIALLY...THE SFC PRESSURE PATTERN REMAINS
VERY DIFFUSE WITH LITTLE SFC FORCING. HOWEVER...BY LATE
TONIGHT...THE SHORT RANGE GUIDANCE IS IN GOOD AGREEMENT ON
INCREASING THE PCPN THREAT AS A STRONG SHORTWAVE DROPS OUT OF THE
NORTHERN ROCKIES AND PUSHES INTO THE NORTHERN PLAINS TONIGHT AND
ACROSS THE UPPER MISSISSIPPI VALLEY TOMORROW. THIS SHORT WAVE WILL
REINFORCE A WEAK SFC COLD FRONT...WHICH WILL PROVIDE THE SFC FORCING
TO IGNITE THUNDERSTORMS. THE MAIN FORECAST CONCERN WITH THIS SYSTEM
WILL BE HOW FAR SOUTH TO EXTEND THE HIGHER POPS THROUGH THE MIDWEST
AND INTO THE MIDDLE MISSISSIPPI VALLEY. WHILE THE STRONGEST FORCING
SHOULD REMAIN TO THE NORTH OF THE LOCAL AREA IN WISCONSIN WITH THE
TRACK OF THE MAIN VORT MAX...THERE SHOULD BE ENOUGH UPPER LEVEL
FORCING EXTENDING SWD...COINCIDENT WITH THE SFC COLD FRONT TO
WARRANT KEEPING LIKELY POPS ACROSS THE CWA BEGINNING EARLY TOMORROW
MORNING OVER THE ROCKFORD AREA AND THEN SPREADING EWD THROUGH THE
DAY AS THE COLD FRONT PUSHES EWD. THE WARM SECTOR ENVIRONMENT
SHOULD BE PRIMED FOR THUNDERSTORMS BY LATE MORNING/EARLY AFTERNOON
AS TEMPERATURES SHOULD REACH INTO THE UPPER 80S TO CLOSE TO 90
DEGREES WITH SFC DEW POINTS IN THE UPPER 60S TO LOWER 70S. DEEP
LAYER INSTABILITY WILL ALSO BE MORE THAN ADEQUATE FOR THUNDERSTORM
DEVELOPMENT AS IS EVIDENCED BY BUFKIT SOUNDS FROM THE NAM12
ADVERTISING CAPE VALUES EXCEEDING 1500 J/KG BY THE LATE MORNING
HOURS AND INCREASING TO ARND 2500 J/KG DURING THE AFTERNOON. THE
GIVEN THE ELEMENTS EXPECTED TO BE IN PLACE TOMORROW...THE ;LATEST
SPC DAY 2 OUTLOOK KEEPS THE CWA IN A SLIGHT RISK AREA FOR SEVERE
THUNDERSTORMS. THE GREATEST THREAT SHOULD BE DURING THE LATE
AFTERNOON HOURS AS THE COLD FRONT CROSSES THE AREA DURING THE TIME
OF PEAK HEATING. THE MAIN SEVERE THREAT SHOULD BE STRONG...DAMAGING
STRAIGHT LINE WINDS GIVEN A RELATIVELY DRY LAYER EXPECTED BETWEEN
850MB-700MB...THOUGH THERE MAY ALSO BE A LARGE HAIL THREAT AS COOLER
AIR MOVES IN ALOFT WITH FREEZING LEVELS DROPPING TO ARND 12KFT.
LOCALLY HEAVY RAINFALL WILL BE LESS OF A CONCERN AS THE COLD FRONT
WILL BE PROGRESSIVE THROUGH THE DAY AND PWATS ARE EXPECTED TO BE 1.5
INCHES OR LESS.
THURSDAY IS SHAPING UP TO BE DRY AND THE NEXT CHANCE FOR PCPN WILL
COME BY EARLY FRIDAY MORNING AS A LONG WAVE TROUGH DROPS INTO THE
UPPER MISSISSIPPI VALLEY. A WEAK FRONT ASSOCIATED WITH THE UPPER
TROUGH IS EXPECTED TO MOVE INTO NWRN IL EARLY FRIDAY...BUT THE MAIN
CONCERN WILL BE SFC WAVE DEVELOPMENT ALONG THE COLD FRONT. THE
LONGER RANGE GUIDANCE IS IN GOOD AGREEMENT ON THE FORMATION OF A
DECENT SFC WAVE ON THE FRONT...BUT THERE IS LESSER AGREEMENT ON THE
STRENGTH AND LOCATION OF THE SFC WAVE DEVELOPMENT. HOWEVER...THERE
IS ENOUGH CONFIDENCE TO CARRY LIKELY POPS FOR THE SRN PORTIONS OF
THE CWA...WITH A CHANCE OF THUNDERSTORMS...BUT LESSER CONFIDENCE TO
THE NORTH...SO WILL ONLY CARRY CHANCE POPS FOR THE NORTHERN PORTIONS
OF THE CWA.
FOR TEMPERATURES...FOLLOWING THE PASSAGE OF THE COLD FRONT
TOMORROW...HIGHS WILL DROP BACK INTO UPPER 70S TO LOWER 80S FOR
THURSDAY. FOR FRIDAY AND SATURDAY...AS THE LONG WAVE UPPER TROUGH
MOVES ACROSS THE REGION...HIGHS SHOULD ONLY BE IN THE MIDDLE 70S FOR
FRIDAY/ THE COOLEST AIR WILL MOVE OVER THE AREA FOR THE WEEKEND
WITH TEMPS ONLY REACHING INTO THE UPPER 60S TO AROUND 70F ON
SATURDAY AND THE LOWER 70S FOR SUNDAY. WEAK UPPER RIDGING SHOULD
RETURN TO THE AREA BY EARLY NEXT WEEK...BRINGING SLIGHTLY WARMER
WEATHER WITH HIGHS IN THE MIDDLE 70S.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* CHANCE FOR SHRA/TSRA AFTER SUNRISE.
* CHANCE FOR TSRA THIS AFTERNOON.
* POTENTIAL FOR GUSTY SOUTH/SOUTHWEST WINDS. CMS
//DISCUSSION...UPDATED 06Z...
LINE OF TSRA CONTINUES TO WEAKEN AS IT MOVES SOUTHEAST OF THE
TERMINALS WITH SHOWERS EXPECTED TO END OVER THE CHICAGO AREA
TERMINALS IN THE NEXT 1-2 HRS. A SMALL SCALE HIGH PRESSURE HAS
FORMED ON THE BACK SIDE OF THE PRECIPITATION. AS A RESULT...
WINDS WILL TURN NORTHEAST...EAST...SOUTHEAST THEN BACK LIGHT
SOUTHERLY OVER THE NEXT FEW HOURS AS THIS HIGH MOVES SOUTHEAST.
SPEEDS LIKELY TO BE IN THE 10-15 KT RANGE WITH HIGHER GUSTS
POSSIBLE BUT THE OVERALL TREND WILL BE FOR SPEEDS TO SLOWLY
DIMINISH.
FOCUS THEN SHIFTS TO A LINE OF TSRA NOW MOVING ACROSS NORTH
CENTRAL IA AND SOUTHERN MN. SHORT TERM GUIDANCE WOULD SUGGEST THIS
LINE WILL CONTINUE MOVING EAST AND SHOULD BEGIN TO WEAKEN AFTER
SUNRISE. WHILE THE BULK OF THIS ACTIVITY MAY MOVE ACROSS SOUTHERN
WI...HAVE OPTED TO INCLUDE A TEMPO FOR TSRA AT RFD AND SHRA AT DPA
AND TRENDS WILL NEED TO BE MONITORED EARLY THIS MORNING WITH TSRA
POSSIBLY NEEDED TO BE ADDED FOR THE CHICAGO TERMINALS AFTER
SUNRISE. THIS ACTIVITY MAY THEN AFFECT ANY ADDITIONAL TSRA
DEVELOPMENT LATER THIS AFTERNOON WITH A POSSIBLE OUTFLOW PUSHING
SOUTH ACROSS THE TERMINALS DURING THE MORNING AND BECOMING THE
FOCUS FOR NEW DEVELOPMENT...WELL AHEAD OF THE COLD FRONT WITH
PERHAPS WEAKER CONVECTION DEVELOPING WITH THE FRONT. AT THIS
POINT...CONFIDENCE IS TOO LOW TO MAKE ANY SIGNIFICANT CHANGES AND
HAVE MAINTAINED PREVIOUS TSRA TIMING FOR THIS AFTERNOON. IF
CONVECTION DOES MATERIALIZE...STRONG/GUSTY WINDS WILL BE
POSSIBLE.
UNCERTAINTY ALSO REMAINS REGARDING HOW STRONG SOUTH/SOUTHWEST
WINDS WILL BECOME LATER THIS MORNING INTO THIS AFTERNOON AS WELL.
NEWEST FORECAST SOUNDINGS WOULD SUGGEST LOW LEVEL WINDS WILL NOT
BE QUITE AS STRONG AS PREVIOUSLY THOUGHT...BUT GUSTS TO 20 KTS
STILL POSSIBLE IN THE AFTERNOON. CMS
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* LOW CONFIDENCE REGARDING POTENTIAL SHRA/TSRA AFTER SUNRISE.
* MEDIUM CONFIDENCE REGARDING TSRA THIS AFTERNOON...LOW CONFIDENCE
REGARDING TIMING/DURATION.
* MEDIUM CONFIDENCE REGARDING WIND SPEEDS/DIRECTIONS THROUGH THE
PERIOD...LOW CONFIDENCE REGARDING GUSTS. CMS
//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...
* THURSDAY...VFR.
* FRIDAY THROUGH SATURDAY...CHANCE OF SHRA. MVFR POSSIBLE.
* SUNDAY...SLIGHT CHANCE OF SHRA.
* MONDAY...VFR.
&&
.MARINE...
323 PM CDT
LIGHT VARIABLE WINDS WILL BEGIN TO FAVOR A SOUTHERLY DIRECTION
TONIGHT AND GRADUALLY FRESHEN AS A COLD FRONT ADVANCES EASTWARD
INTO THE UPPER MIDWEST OVERNIGHT. THE COLD FRONT WILL MOVE ACROSS
NORTHERN LAKE MI BY MID AFTERNOON WED AND ACROSS SOUTHERN LAKE MI
BY MID EVENING...WITH WINDS VEERING TO SOUTHWEST THEN WEST AND
NORTHWEST WITH THE PASSAGE OF THE COLD FRONT. A SECOND COLD FRONT
WILL MOVE ACROSS LAKE MI LATE THU NIGHT AND FRI. WINDS WILL BECOME
SOUTHWESTERLY AS THE FRONT NEARS...THEN VEER TO OUT OF THE WEST
AND NORTHWEST AGAIN WITH THE COLD FRONT PASSAGE. HIGH PRESSURE OF
OVER SASKATCHEWAN AND MANITOBA WILL EXPAND OVER THE PLAINS AND
NORTHERN GREAT LAKES FRIDAY NIGHT. WINDS WILL INCREASE TO STRONG
NORTH TO NORTHEAST BREEZES FOR SAT AND SUN...WITH SOME GUSTS NEAR
GALE FORCE ON SOUTHERN LAKE MI AS THE PRESSURE GRADIENT ACROSS
THE REGION INCREASES BETWEEN THE HIGH PRESSURE RIDGE TO THE N AND
W...AND A LOW MOVING FROM THE MID MS VALLEY UP THE OH VALLEY.
TRS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1009 PM CDT TUE SEP 4 2012
.MESOSCALE DISCUSSION...
728 PM CDT
CLOSELY MONITORING CONVECTION OVER WESTERN WISCONSIN EARLY THIS
EVENING FOR ANY POTENTIAL IMPACTS ON OUR CWA TONIGHT. CLUSTER OF
STRONG TO SEVERE THUNDERSTORMS OVER SOUTHWEST WISCONSIN APPEARS TO
BE CONGEALING IN A LARGE MASS OF STORMS WHICH COULD RESULT IN
FORMATION OF COLD POOL AND A MORE ACCELERATED MOTION. FORWARD
PROPAGATING CORFIDI VECTORS FROM WRF-NAM AND RUC BOTH SUGGEST
CONVECTION WOULD RACE QUICKLY EAST-SOUTHEAST TOWARD CHGO
METRO...HOWEVER SPC OBJECTIVE MESOANALYSIS DATA SHOWS A REGION OR
MUCH LESSER INSTABILITY AND GREATER INHIBITION OVER SOUTHERN
WISCONSIN. VISIBLE SATELLITE IMAGERY TUES AFTERNOON SHOWED A
DISTINCT ABSENCE OF CUMULUS IN A SWATH FROM NE IL (AHEAD OF LAKE
BREEZE) NNW INTO CENTRAL WISCONSIN...WHICH WOULD LEND SOME CREDENCE
TO THE WEAKER INSTABILITY/STRONGER CAPPING SHOWN IN THE SPC
OBJECTIVE ANALYSIS DATA.
RELATIVELY WEAK LOW LEVEL FLOW SUGGESTS ANY RAPID NORTHEASTWARD
TRANSPORT OF MOISTURE OR INSTABILITY IS UNLIKELY THIS EVENING...SO
WOULD ANTICIPATE CONVECTION TO WEAKEN AS IT PROGRESSES EASTWARD INTO
THE LESS UNSTABLE ENVIRONMENT OVER SOUTHERN WISCONSIN. LOOKING LIKE
A MORE PLAUSIBLE SCENARIO WOULD BE FOR MOST INTENSE VIGOROUS
CONVECTION TO FAVOR THE WESTERN PORTIONS OF THIS DEVELOPING MCS AND
FOR THE STRONGER CELLS TO TEND TO PROPAGATE MORE SOUTHWARD INTO THE
AXIS OF GREATER MOISTURE/INSTABILITY WHICH WAS NICELY DEPICTED BY
THE CUMULUS FIELD THIS AFTERNOON. MODELS REALLY NOT SHOWING ANY
SIGNIFICANT LOW LEVEL JET OR LOW LEVEL WARM AIR ADVECTION OVERNIGHT
SO ITS QUESTIONABLE HOW WELL SUSTAINED THIS CONVECTION WILL BE INTO
THE MID TO LATE EVENING...BUT REGARDLESS GIVEN ITS ALREADY RATHER
CLOSE PROXIMITY FEEL SOME UPWARD ADJUSTMENTS TO POP GRIDS FOR
TONIGHT ARE WARRANTED...ESPECIALLY WESTERN CWA.
IZZI
&&
.DISCUSSION...
307 PM CDT
MAIN FORECAST CONCERN FOR THE NEXT FEW DAYS WILL FOCUS ON THE
INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS TONIGHT AND
TOMORROW ASSOCIATED WITH A COLD FRONT DROPPING SEWD OUT OF THE UPPER
MISSISSIPPI VALLEY.
FOR THE REMAINDER OF THE AFTERNOON AND THIS EVENING...CONDITIONS
WILL REMAIN GENERALLY QUIET...HOWEVER...WITH AMPLE LOW LEVEL
MOISTURE LINGERING OVER THE REGION FOLLOWING THE PASSAGE OF TROPICAL
CYCLONE ISAAC...DAYTIME WARMING COMBINED WITH A LAKE BREEZE BOUNDARY
PUSHING INLAND FROM LAKE MICHIGAN WILL ALLOW FOR AT LEAST A SMALL
CHANCE OF SHOWERS OR THUNDERSTORMS OVER THE AREA THROUGH EARLY THIS
EVENING.
FOR THE LARGER SCALE...A PERSISTENT POLAR LOW CONTINUES TO SIT AND
SPIN OVER NRN MANITOBA WHILE A SERIES OF WEAK IMPULSES TRACK ALONG
THE SRN PERIPHERY. INITIALLY...THE SFC PRESSURE PATTERN REMAINS
VERY DIFFUSE WITH LITTLE SFC FORCING. HOWEVER...BY LATE
TONIGHT...THE SHORT RANGE GUIDANCE IS IN GOOD AGREEMENT ON
INCREASING THE PCPN THREAT AS A STRONG SHORTWAVE DROPS OUT OF THE
NORTHERN ROCKIES AND PUSHES INTO THE NORTHERN PLAINS TONIGHT AND
ACROSS THE UPPER MISSISSIPPI VALLEY TOMORROW. THIS SHORT WAVE WILL
REINFORCE A WEAK SFC COLD FRONT...WHICH WILL PROVIDE THE SFC FORCING
TO IGNITE THUNDERSTORMS. THE MAIN FORECAST CONCERN WITH THIS SYSTEM
WILL BE HOW FAR SOUTH TO EXTEND THE HIGHER POPS THROUGH THE MIDWEST
AND INTO THE MIDDLE MISSISSIPPI VALLEY. WHILE THE STRONGEST FORCING
SHOULD REMAIN TO THE NORTH OF THE LOCAL AREA IN WISCONSIN WITH THE
TRACK OF THE MAIN VORT MAX...THERE SHOULD BE ENOUGH UPPER LEVEL
FORCING EXTENDING SWD...COINCIDENT WITH THE SFC COLD FRONT TO
WARRANT KEEPING LIKELY POPS ACROSS THE CWA BEGINNING EARLY TOMORROW
MORNING OVER THE ROCKFORD AREA AND THEN SPREADING EWD THROUGH THE
DAY AS THE COLD FRONT PUSHES EWD. THE WARM SECTOR ENVIRONMENT
SHOULD BE PRIMED FOR THUNDERSTORMS BY LATE MORNING/EARLY AFTERNOON
AS TEMPERATURES SHOULD REACH INTO THE UPPER 80S TO CLOSE TO 90
DEGREES WITH SFC DEW POINTS IN THE UPPER 60S TO LOWER 70S. DEEP
LAYER INSTABILITY WILL ALSO BE MORE THAN ADEQUATE FOR THUNDERSTORM
DEVELOPMENT AS IS EVIDENCED BY BUFKIT SOUNDS FROM THE NAM12
ADVERTISING CAPE VALUES EXCEEDING 1500 J/KG BY THE LATE MORNING
HOURS AND INCREASING TO ARND 2500 J/KG DURING THE AFTERNOON. THE
GIVEN THE ELEMENTS EXPECTED TO BE IN PLACE TOMORROW...THE ;LATEST
SPC DAY 2 OUTLOOK KEEPS THE CWA IN A SLIGHT RISK AREA FOR SEVERE
THUNDERSTORMS. THE GREATEST THREAT SHOULD BE DURING THE LATE
AFTERNOON HOURS AS THE COLD FRONT CROSSES THE AREA DURING THE TIME
OF PEAK HEATING. THE MAIN SEVERE THREAT SHOULD BE STRONG...DAMAGING
STRAIGHT LINE WINDS GIVEN A RELATIVELY DRY LAYER EXPECTED BETWEEN
850MB-700MB...THOUGH THERE MAY ALSO BE A LARGE HAIL THREAT AS COOLER
AIR MOVES IN ALOFT WITH FREEZING LEVELS DROPPING TO ARND 12KFT.
LOCALLY HEAVY RAINFALL WILL BE LESS OF A CONCERN AS THE COLD FRONT
WILL BE PROGRESSIVE THROUGH THE DAY AND PWATS ARE EXPECTED TO BE 1.5
INCHES OR LESS.
THURSDAY IS SHAPING UP TO BE DRY AND THE NEXT CHANCE FOR PCPN WILL
COME BY EARLY FRIDAY MORNING AS A LONG WAVE TROUGH DROPS INTO THE
UPPER MISSISSIPPI VALLEY. A WEAK FRONT ASSOCIATED WITH THE UPPER
TROUGH IS EXPECTED TO MOVE INTO NWRN IL EARLY FRIDAY...BUT THE MAIN
CONCERN WILL BE SFC WAVE DEVELOPMENT ALONG THE COLD FRONT. THE
LONGER RANGE GUIDANCE IS IN GOOD AGREEMENT ON THE FORMATION OF A
DECENT SFC WAVE ON THE FRONT...BUT THERE IS LESSER AGREEMENT ON THE
STRENGTH AND LOCATION OF THE SFC WAVE DEVELOPMENT. HOWEVER...THERE
IS ENOUGH CONFIDENCE TO CARRY LIKELY POPS FOR THE SRN PORTIONS OF
THE CWA...WITH A CHANCE OF THUNDERSTORMS...BUT LESSER CONFIDENCE TO
THE NORTH...SO WILL ONLY CARRY CHANCE POPS FOR THE NORTHERN PORTIONS
OF THE CWA.
FOR TEMPERATURES...FOLLOWING THE PASSAGE OF THE COLD FRONT
TOMORROW...HIGHS WILL DROP BACK INTO UPPER 70S TO LOWER 80S FOR
THURSDAY. FOR FRIDAY AND SATURDAY...AS THE LONG WAVE UPPER TROUGH
MOVES ACROSS THE REGION...HIGHS SHOULD ONLY BE IN THE MIDDLE 70S FOR
FRIDAY/ THE COOLEST AIR WILL MOVE OVER THE AREA FOR THE WEEKEND
WITH TEMPS ONLY REACHING INTO THE UPPER 60S TO AROUND 70F ON
SATURDAY AND THE LOWER 70S FOR SUNDAY. WEAK UPPER RIDGING SHOULD
RETURN TO THE AREA BY EARLY NEXT WEEK...BRINGING SLIGHTLY WARMER
WEATHER WITH HIGHS IN THE MIDDLE 70S.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 03Z...
* LINE OF STRONG TO SEVERE THUNDERSTORMS LATE THIS EVENING.
* TSRA WEDNESDAY AFTERNOON.
* GUSTY SOUTHWEST WINDS WEDNESDAY. CMS
//DISCUSSION...UPDATED 03Z...
LINE OF TSRA OVER SOUTHWEST WI EARLIER THIS EVENING DID INDEED
ORGANIZE INTO A BOW AND IS NOW PUSHING INTO NORTHERN IL. OUTFLOW
BOUNDARY OUT AHEAD OF THE MAIN LINE OF STORMS HAS BEEN GUSTING
BETWEEN 40 AND 50 KNOTS. HAVE TRIED TO INCLUDE SOME TIMING IN THE
03Z UPDATES WITH THE INITIAL OUTFLOW/GUSTS AND THEN THE LINE OF
TSRA...THOUGH OUTFLOW TIME MAY END UP BEING A BIT EARLY. WINDS
STILL QUITE GUSTY BEHIND THE OUTFLOW. IFR VIS AND POSSIBLY IFR
CIGS LIKELY WITH THE HEAVIEST STORMS. CMS
PREVIOUS 00Z DISCUSSION...
SEVERAL FORECAST CONCERNS THIS PERIOD WITH THE MAIN CONCERN BEING
TSRA TIMING/DURATION WEDNESDAY AFTERNOON.
IN THE SHORT TERM...ISOLATED CONVECTION DEVELOPED OVER PARTS OF
NORTH CENTRAL IL EARLIER THIS AFTERNOON AND HAS SINCE DISSIPATED.
NOT EXPECTING ANY FURTHER DEVELOPMENT BUT IF ANYTHING DOES DEVELOP
IS SHOULD REMAIN ISOLATED AND BRIEF. LINE OF TSRA OVER SOUTHWEST
WI IS EXPECTED TO MOVE EAST AND BEGIN TO WEAKEN LATER THIS
EVENING BUT WILL NEED TO BE MONITORED TO SEE IF IT BEGINS TO TURN
SOUTHEAST AND MOVE INTO NORTHERN IL AND EVEN IF THE CONVECTION
DOESN/T MAKE IT...COULD POSSIBLY BE AND OUTFLOW BOUNDARY PUSHING
INTO NORTHERN IL.
ATTENTION THEN SHIFTS TO THE WEST WITH SOME ELEVATED ACTIVITY
POSSIBLY DEVELOPING OVER IA OVERNIGHT. CONFIDENCE IS FAIRLY LOW
THAT THIS WILL HAPPEN BUT IF ANYTHING DEVELOPS...IT WILL MOVE
GENERALLY EAST AND INTO NORTHWEST IL TOWARD DAYBREAK. EVEN
THEN...IT WOULD LIKELY BE WEAKENING AND THUS HAVE MAINTAINED A DRY
FORECAST INTO MID MORNING.
A COLD FRONT WILL MOVE ACROSS THE AREA WEDNESDAY AFTERNOON AND IT
APPEARS THE BEST CHANCE FOR TSRA WILL BE ALONG/AHEAD OF THIS
FRONT. CONFIDENCE FOR A LINE OF STORMS TO MOVE ACROSS THE
TERMINALS IS GROWING AS IS CONFIDENCE FOR TIMING IN THE MID
AFTERNOON HRS...BUT THIS TIMING AS WELL AS DURATION WILL LIKELY
NEED TO BE TWEAKED WITH LATER FORECASTS. INSTABILITY COMBINED WITH
FAIRLY STRONG WINDS ALOFT WILL LIKELY LEAD TO STRONG/GUSTY WINDS
AT THE TERMINALS WITH THESE STORMS.
LAKE BREEZE NOW WEST OF DPA WILL WASHOUT THIS EVENING WITH
EASTERLY WINDS TURNING SOUTHEAST THIS EVENING THEN SOUTHERLY
OVERNIGHT WITH SPEEDS ALSO DIMINISHING TO 5 KTS OR LESS. WINDS
REMAIN SOUTH/SOUTHWEST INTO WEDNESDAY MORNING AND AS NOTED ABOVE
SOUNDINGS SUGGEST FAIRLY STRONG WINDS ALOFT. HAVE BUMPED WIND
GUSTS UP TO 20KTS MIDDAY BUT SOUNDINGS WOULD SUGGEST GUSTS COULD
BE AS HIGH AS 25KTS. SPEEDS/GUSTS WILL BE DEPENDENT ON CLOUD COVER
AND LOW LEVEL MIXING...THUS CONFIDENCE ISN/T ALL THAT HIGH AS TO
HOW HIGH PREVAILING SPEEDS/GUSTS WILL BECOME.
WHILE THE LOW LEVELS REMAIN QUITE MOIST...MOSTLY SUNNY SKIES TODAY
COMBINED WITH SOME MODEST DRYING...SHOULD PREVENT ANY WIDESPREAD
FOG PROBLEMS TONIGHT...BUT WITH LIGHTER WINDS EXPECTED TOWARD
MORNING COULD SEE SOME LIGHT/SHALLOW GROUND FOG...ESPECIALLY IN
THE USUAL AREAS. CMS
//ORD AND MDW CONFIDENCE...UPDATED 03Z...
* HIGH CONFIDENCE REGARDING TSRA AND WIND GUSTS LATE THIS EVENING.
* HIGH CONFIDENCE TSRA WILL IMPACT ORD/MDW WEDNESDAY AFTERNOON...
MEDIUM CONFIDENCE ON TIMING...LOW CONFIDENCE ON DURATION.
* MEDIUM CONFIDENCE REGARDING WIND SPEEDS/DIRECTIONS THROUGH THE
PERIOD...LOW CONFIDENCE REGARDING GUSTS WEDNESDAY. CMS
//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...
* THURSDAY...VFR.
* FRIDAY THROUGH SATURDAY...CHANCE OF SHRA. MVFR POSSIBLE.
* SUNDAY...SLIGHT CHANCE OF SHRA.
* MONDAY...VFR.
&&
.MARINE...
323 PM CDT
LIGHT VARIABLE WINDS WILL BEGIN TO FAVOR A SOUTHERLY DIRECTION
TONIGHT AND GRADUALLY FRESHEN AS A COLD FRONT ADVANCES EASTWARD
INTO THE UPPER MIDWEST OVERNIGHT. THE COLD FRONT WILL MOVE ACROSS
NORTHERN LAKE MI BY MID AFTERNOON WED AND ACROSS SOUTHERN LAKE MI
BY MID EVENING...WITH WINDS VEERING TO SOUTHWEST THEN WEST AND
NORTHWEST WITH THE PASSAGE OF THE COLD FRONT. A SECOND COLD FRONT
WILL MOVE ACROSS LAKE MI LATE THU NIGHT AND FRI. WINDS WILL BECOME
SOUTHWESTERLY AS THE FRONT NEARS...THEN VEER TO OUT OF THE WEST
AND NORTHWEST AGAIN WITH THE COLD FRONT PASSAGE. HIGH PRESSURE OF
OVER SASKATCHEWAN AND MANITOBA WILL EXPAND OVER THE PLAINS AND
NORTHERN GREAT LAKES FRIDAY NIGHT. WINDS WILL INCREASE TO STRONG
NORTH TO NORTHEAST BREEZES FOR SAT AND SUN...WITH SOME GUSTS NEAR
GALE FORCE ON SOUTHERN LAKE MI AS THE PRESSURE GRADIENT ACROSS
THE REGION INCREASES BETWEEN THE HIGH PRESSURE RIDGE TO THE N AND
W...AND A LOW MOVING FROM THE MID MS VALLEY UP THE OH VALLEY.
TRS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
200 AM EDT WED SEP 5 2012
.AVIATION...
06Z TAFS...AVIATION CONCERNS CENTER ON EVOLUTION OF MCS ACROSS
NORTHEAST ILLINOIS/FAR NORTHWEST INDIANA...FOG POTENTIAL THROUGH
EARLY WEDNESDAY MORNING...AND THUNDERSTORM CHANCES WEDNESDAY
AFTERNOON AND EVENING. IR SATELLITE/RADAR TRENDS CONTINUE TO
INDICATE WEAKENING TREND TO CONVECTIVE SYSTEM ACROSS FAR NORTHWEST
INDIANA/NORTHEAST ILLINOIS AND EXPECT THIS TREND TO CONTINUE AS
CONDITIONS DOWNSTREAM ARE NOT AS UNSTABLE. NONETHELESS...A MATURE
OUTFLOW BOUNDARY RACING WELL AHEAD WILL CONTINUE TO ALLOW ISOLATED
TO SCATTERED SHOWERS TO DEVELOP...AND PERHAPS A THUNDERSTORMS OVER
THE NEXT SEVERAL HOURS. HAVE INCLUDED A WIND GUST GROUP AT KSBN TO
AROUND 20 KNOTS TO ACCOUNT FOR THIS OUTFLOW BOUNDARY THROUGH
08Z...BUT WILL CONFINE PRECIP MENTION TO VCSH AT THIS TIME.
OTHERWISE FOR THE OVERNIGHT HOURS...FOG POTENTIAL WILL BE THE
BIGGEST CONCERN AND HAVE MADE NO CHANGES TO PREVIOUS TAFS WHICH
FOCUS THE LIFR CONDITIONS AT KFWA WHERE CROSSOVER TEMPS ARE HIGHER
AND LESS INFLUENCE FROM CONVECTIVE DEBRIS CLOUDINESS IS EXPECTED.
FOR WEDNESDAY...NEXT UPSTREAM SHORT WAVE ACROSS THE DAKOTAS WILL
APPROACH THE WESTERN GREAT LAKES BY EVENING...WITH A POTENTIAL FOR
SMALLER SCALE CONVECTIVE VORTS TO REACH NORTHWEST INDIANA DURING
THE AFTERNOON. MODERATELY TO STRONGLY UNSTABLE CONDITIONS ARE ALSO
EXPECTED TO DEVELOP ESPECIALLY FOR KSBN AND HAVE INCLUDED VCTS
MENTION IN THE 20Z-04Z TIMEFRAME.
&&
PREV DISCUSSION... /ISSUED 339 PM EDT TUE SEP 4 2012/
SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT.
SEVERAL CONCERNS TO DEAL WITH OVER THE NEXT 36 HOURS FROM
CONVECTION/SVR WX TO FOG.
WEAK FRONTAL BOUNDARY WAS ROUGHLY LOCATED FROM MONTICELLO TO FORT
WAYNE TO DEFIANCE WITH ISOL TO SCT SHOWERS STRUGGLING TO TAKE SHAPE
ALONG WITH GIVEN WEAK CONVERGENCE AND LIMITED INSTABILITY. WILL KEEP
A PRE 1ST PERIOD TO ADDRESS THIS ACTIVITY WHICH SHOULD EXIT BY 00Z.
WITH MOIST BOUNDARY LAYER AND LITTLE CHANCE FOR MIXING ACROSS THE
AREA TODAY...FOG/STRATUS POTENTIAL WILL REMAIN HIGH ACROSS MOST IF
NOT ALL OF THE FORECAST AREA. COULD SEE WIDESPREAD DENSE FOG LATER
TONIGHT IN MANY SPOTS WITH TEMPS FALLING PASS CROSSOVER TEMPS IN THE
UPPER 60S TO AROUND 70 AND CALM WINDS/CLEAR SKIES. POTENTIAL ISSUES
ARISE FROM ANTICIPATED UPSTREAM CONVECTION ACROSS MINN/WI/IOWA.
SEVERAL RUNS OF THE HRRR HAVE SHOWN DEVELOPMENT ACROSS THIS AREA
DROPPING TOWARDS POSSIBLE WESTERN PARTS OF THE FORECAST AREA LATER
TONIGHT/WEDS MORNING...POSSIBLY CAUSING ISSUES WITH FOG DEVELOPMENT.
FOR NOW...HAVE BUMPED UP WORDING IN ZONES TO PATCHY DENSE FOG AND
WILL DEFER TO EVENING/OVERNIGHT SHIFTS TO ADJUST BASED ON UPSTREAM
TRENDS.
STRONGER UPPER LEVEL TROUGH AND SFC COLD FRONT STILL POISED TO MOVE
INTO THE REGION WEDS/WEDS NGT. STRONG DYNAMICS WILL ACCOMPANY THE
SYSTEM WITH A FAVORABLE TIMING OF LIFT AND MSTR CONVERGENCE IN THE
LATE AFTERNOON/EARLY EVENING. GIVEN 0-6 KM SHEAR IN THE 30 TO 40 KT
RANGE SVR THREAT IS STILL POSSIBLE...IF SUFFICIENT HEATING CAN OCCUR
AHEAD OF THE ACTUAL FRONT. THE FLY IN THE OINTMENT FOR THIS MAY BE
ANY LATE NIGHT/MORNING CONVECTION NOTED ABOVE THAT COULD STABILIZE
THE AREA THROUGH OPTIMAL PEAK HEATING...THEREBY REDUCING CHANCES FOR
SVR WX. DO STILL FEEL THAT CONVECTION WILL FIRE TO THE WEST ALONG
THE FRONT IN ILLINOIS DURING THE AFTERNOON AND MOVE EAST TOWARDS THE
AREA. HAVE THEREFORE CAUTIOUSLY HELD WITH LIKELY POPS IN NW AREAS
WEDS AFTERNOON BUT FOR NOW BACKED OFF ON POP TIMING EARLIER IN THE
DAY ASSUMING THAT MODEL INDICATIONS OF IA/WI/MN COMPLEX DYING AS IT
APPROACHES OCCUR. THIS SAME REASONING WARRANTS A SLIGHT INCREASE IN
POPS WEDS NGT WITH POTENTIAL FOR SOMEWHAT SLOWER DEPARTURE OF
PRECIP...BUT NOT A RAMP UP TO LIKELY IN EASTERN AREAS GIVEN LESS
FAVORABLE TIME FRAME FOR CONVECTION TO MAINTAIN ITSELF UNLESS
ALREADY WELL ESTABLISHED.
LONG TERM...
THURSDAY THROUGH TUESDAY...THE MAIN CHALLENGES THIS PERIOD CONCERN
THE CHANCES FOR THE DEVELOPMENT OF A CUT OFF LOW OVER THE OHIO
VALLEY REGION THIS WEEKEND. ADDITIONAL CHALLENGES INCLUDE THE TIMING
AND EXTENT OF PRECIPITATION AND THE EFFECT ON TEMPERATURES IF THE
LOW DEVELOPS AND LINGERS OVER OR NEAR THE REGION. FOR THIS
PACKAGE...FAVOR THE ECMWF...ALTHOUGH THE 12Z RUN WAS AN OUTLIER
COMPARED TO THE PAST SEVERAL RUNS. THE 12Z ECMWF RUN WAS NOT USED
FOR THIS PACKAGE. THE PAST SEVERAL ECMWF RUNS HAVE HAD REASONABLE
RUN TO RUN CONSISTENCY. AS A WHOLE THE NEW 12Z GFS SOLUTION HAS
TRENDED TOWARD THE SLOWER...FARTHER WEST 00Z ECMWF SOLUTION.
ALSO...THE 00Z ECMWF HAS HAD BETTER SUPPORT WITH THE SURFACE
LOW/SURFACE REFLECTION CLOSER TO THE UPPER LOW THAN THE GFS. HAVE
RAISED RAIN CHANCES FRIDAY NIGHT GIVEN REASONABLE CONFIDENCE IN THE
TIMING OF THE SHORT WAVE TROF AND ASSOCIATED COLD FRONT. FOR THE
REST OF THE PERIOD...WENT WITH PERSISTENCE AND ATTEMPTED TO HOLD TO
THE PREVIOUS FORECAST WITH DRY CONDITIONS STARTING SUNDAY NIGHT.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR INZ006>009-
017-018-024>027-032>034.
MI...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR MIZ080-081.
OH...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR OHZ001-002-
004-005-015-016-024-025.
LM...NONE.
&&
$$
SHORT TERM...FISHER
LONG TERM...SKIPPER
AVIATION...MARSILI
AREA FORECAST DISCUSSION
NWS DES MOINES IA
1225 AM CDT WED SEP 5 2012
...UPDATED AVIATION DISCUSSION...
.SHORT TERM /TONIGHT/...
PRIMARY CONCERN TONIGHT WILL BE CONVECTIVE TRENDS BUT CONFIDENCE IN
THAT EVOLUTION IS DECREASING AS MOST MODELS...HIGH RES EXPLICIT AND
PARAMETERIZED...ARE CURRENTLY OVERZEALOUS IN THEIR DEPICTION OF
PRECIP. PRESENT SITUATION HAS 80KT JET FROM ROCKIES INTO IA
ENHANCING DEEP/EFFECTIVE SHEAR. LITTLE IN THE WAY OF LARGE SCALE
FORCING NOTED IMMEDIATELY UPSTREAM HOWEVER WITH RAP ANALYSIS AND
WATER VAPOR IMAGERY FAIRLY BENIGN. ONLY SIGN OF LARGER SCALE UPWARD
VERTICAL MOTION /UVM/ SEEMS TO BE ACROSS CENTRAL NE NEAR H85/H7
SHORT WAVE PER VISIBLE IMAGERY. OUR FORECAST AREA SEEMS PRIMED FOR
DEVELOPMENT THERMODYNAMICALLY WITH UNCAPPED 2000-4000 J/KG MLCAPES.
HOWEVER SPOTTY CONVERGENCE AND LITTLE TO NO UVM OVERHEAD HAVE
RESULTED IN NO DEVELOPMENT AS OF YET. SMALL CELL ALONG HIGHWAY 20
DISSIPATED WHICH IS A SIGNAL THAT WE ARE NOT READY TO GO SURFACE
BASED AND/OR HAVE INSUFFICIENT UPPER LEVEL SUPPORT.
AT THE MOMENT FEEL THAT CONVECTIVE INITIATION IS GOING TO WAIT FOR
AFOREMENTIONED NE UVM ALONG WITH INCREASED SYNOPTIC SCALE FORCING
AHEAD OF MT/DAKOTAS SHORT WAVE AS IT MOVES EAST THIS EVENING.
ECMWF/GFS QG FORCING INCREASES AS IT REACHES MN BY 06Z. 18Z RAP
SUGGESTS WEAKLY CAPPED ELEVATED CAPES 2000 J/KG OR MORE WILL BE IN
PLACE AND CERTAINLY CAPABLE OF SUPPORTING SEVERE WEATHER CONSIDERING
OUR PROXIMITY TO THE JET. DCAPES SHOULD REMAIN QUITE HIGH
OVERNIGHT WITH SOUNDINGS SHOWING PLENTY OF DRY AIR BELOW 3KM. THUS
EXPECT NE CONVECTION TO SLOWLY DEVELOP AND MATURE AS IT REACHES IA
MUCAPE AXIS WITH DAMAGING WINDS AND HAIL QUITE POSSIBLE.
.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
FORECAST CONCERNS FOR WEDNESDAY WILL DEAL WITH A STRONG COLD FRONT
PUSHING ACROSS THE FORECAST AREA DURING THE MORNING AIDED BY A
POTENT SHORT WAVE SWEEPING ACROSS THE NORTHERN PLAINS INTO IA. MOST
OF THE CAPE AND SHEAR ARE AHEAD OF THE BOUNDARY SO ONGOING
CONVECTION FROM THE OVERNIGHT WILL AFFECT THE EASTERN HALF OR SO OF
THE FORECAST AREA. BEHIND THE FRONT MUCH COOLER AND DRIER AIR WILL
PUSH INTO CENTRAL IOWA DURING THE AFTERNOON SO ANY THUNDERSTORM
THREAT IN THE AFTERNOON WILL BE CONFINED TO THE FAR SOUTHEAST
PORTION OF CENTRAL IOWA ON EAST. BEYOND WEDNESDAY WE BEGIN OUR
SLIDE IN TEMPS AS HIGH PRESSURE BUILDS IN WEDNESDAY NIGHT THROUGH
LATE THURSDAY. WARM ADVECTION OCCURS THURSDAY NIGHT AHEAD OF THE
NEXT SYSTEM TO AFFECT THE AREA. ON FRIDAY THETA ADVECTION INCREASES
AND A SECOND SHORT WAVE ROTATES THROUGH THE NORTHERN AND CENTRAL
PLAINS BRINGING AND ANOTHER FRONT WILL PUSH ACROSS IOWA BRINGING A
REINFORCING SHOT OF COLD AIR. SHOWERS AND ISOLATED THUNDERSTORMS
WILL OCCUR WITH THIS FOLLOWED BY SOME VERY COOL AIR. TEMPERATURES
OVER THE WEEKEND WILL ACTUALLY BE BELOW NORMAL BUT IT WILL BE DRY.
&&
.AVIATION...05/06Z
ONGOING CONVECTION ACROSS NORTHERN IOWA WILL AFFECT NORTHERN
SITES...KFOD/KMCW/KALO THROUGH 12Z. WITH STRONGER THUNDERSTORMS
WINDS COULD GUST UP TO 40KTS OR HIGHER...AND WITH HEAVY RAIN COULD
SEE VISIBILITIES DROP TO MVFR OR IFR. HOWEVER...CEILINGS WILL
PRIMARILY REMAIN VFR WITH HIGH BASED STORMS. COULD SEE PRECIPITATION
SPREADING FURTHER SOUTH TO KDSM...AND HAVE VCTS MENTIONED.
PRECIPITATION WILL QUICKLY PUSH OUT OF SITES...BUT COULD SEE SOME BR
OR HZ DEVELOPMENT NEAR 12Z AT SITES. HOWEVER...BELIEVE WINDS WILL
REMAIN STRONG AND HAVE NOT INCLUDED MENTION ATTM. WINDS WILL SHIFT
TO THE N/NE AND WILL BE STRONG AND GUSTY THROUGHOUT THE DAY
WEDNESDAY. OTHERWISE...CEILINGS WILL BE VFR.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...SMALL
LONG TERM...FAB
AVIATION...AWB
AREA FORECAST DISCUSSION
NWS CARIBOU ME
1213 AM EDT WED SEP 5 2012
.SYNOPSIS...
LOW PRESSURE WILL APPROACH FROM THE WEST TONIGHT THEN TRACK ACROSS
COASTAL MAINE WEDNESDAY. WEAK HIGH PRESSURE WILL RETURN THURSDAY
INTO FRIDAY.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
MIDNIGHT UPDATE...NUDGED LIKELY POPS FURTHER NORTH JUST A BIT AS
RAIN IS MOVING INTO WESTERN AROOSTOOK COUNTY AND NORTHERN SOMERSET
AND PISCATAQUIS COUNTY AND MESOSCALE MODELS LIKE THE HRRR INDICATE
RAIN SHOULD EXTEND NORTH INTO CENTRAL AROOSTOOK COUNTY. OTHERWISE
FORECAST REMAINS ON TRACK.
PREV DISC: PRIMARY LOW PRESSURE WILL MOVE INTO THE EASTERN GREAT
LAKES THIS EVENING. LATER TONIGHT A SECONDARY LOW PRESSURE SYSTEM
WILL DEVELOP ON A BOUNDARY RUNNING ALONG THE MAINE COAST. THIS
SYSTEM WHICH IS ACCOMPANIED BY TROPICAL MOISTURE WILL PRODUCE
HEAVY AMOUNTS OF RAIN. ADDITIONAL RAIN IS EXPECTED WEDNESDAY AS
THE PRIMARY LOW MOVES ACROSS THE STATE. FOR POPS HAVE USED A BLEND
OF THE NAM12...GFS40...SREF AND ECMWF. WILL USE SAME BLEND FOR QPF
EXCEPT EXCHANGE NAM80 FOR NAM12. FOR WINDS HAVE BLENDED NAM12 AND
GMOS. USED THE GMOS FOR THE TEMPERATURE AND DEW POINTS.&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
RAIN WILL BE WINDING DOWN WEDNESDAY NIGHT AS ISAAC`S REMNANT LOW
CONTINUES TO MOVE AWAY FROM NEW ENGLAND AND INTO THE CANADIAN
MARITIMES. HIGH PRESSURE WILL BRIEFLY BUILD OVER THE REGION ON
THURSDAY, BRINGING PARTLY SUNNY SKIES AND FAIR WEATHER TO THE AREA.
THIS WILL BE SHORT-LIVED HOWEVER AS A COLD FRONT WILL APPROACH FROM
OUR WEST LATE THURSDAY AND CROSS THE STATE ON FRIDAY. EXPECT SHOWERS
TO DEVELOP AHEAD/ALONG OF THIS BOUNDARY AS IT MOVES THROUGH FROM
NORTHWEST TO SOUTHEAST. MODEL GUIDANCE DOES INDICATE THERE SHOULD BE
ENOUGH INSTABILITY FOR THUNDERSTORMS FRIDAY AFTERNOON WITH CAPES
PROGGED TO BE 500-1200 J/KG. TEMPERATURES WILL BE SEASONABLE BOTH
THURSDAY AND FRIDAY; HIGHS WILL BE IN THE MID 70S AND LOWS IN THE
LOWER TO MID 50S.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
THE BIG CONCERN FOR THE LONG TERM PERIOD IS AN UPPER TROUGH THAT IS
PROGGED TO DEVELOP OVER THE UPPER MIDWEST AND ITS EFFECT ON WHAT
WILL THEN BE HURRICANE LESLIE. CURRENT INDICATIONS ARE THAT THE
TROUGH WILL CUTOFF INTO A LOW OVER THE OHIO RIVER VALLEY SOMETIME ON
SUNDAY WHICH WILL THEN SLOWLY SHIFT EASTWARD THROUGH THE MIDDLE OF
NEXT WEEK. AS IT DOES SO, LESLIE WILL BE PULLED NORTHWARD THROUGH
THE WESTERN ATLANTIC ALONG THE LOW`S EASTERN PERIPHERY. MODEL
GUIDANCE KEEPS THE TROPICAL SYSTEM WELL OFF THE US EAST COAST AND
SOUTH OF NOVA SCOTIA, THOUGH THE 04/00Z RUN OF THE ECMWF BRINGS IT
CLOSE ENOUGH TO BRUSH OUR FAR SOUTHEASTERN ZONES WITH SOME RAIN.
EVEN IF LESLIE STAYS FAR OUT TO SEA AS IS CURRENTLY EXPECTED, IT
WILL STILL IMPACT OUR FORECAST AREA IN TWO WAYS. FIRST, TROPICAL
MOISTURE WILL FEED INTO THE SOUTHWEST FLOW AHEAD OF THE PRIMARY
UPPER LOW. THIS MOISTURE WILL OVERSPREAD NEW ENGLAND, BRINGING
WIDESPREAD SHOWERS TO THE REGION FOR LATE SATURDAY THROUGH MONDAY.
SECOND, LARGE SWELLS AND HEAVY SURF WILL IMPACT THE MAINE COASTLINE
AND COASTAL WATERS SUNDAY AND MONDAY. THIS WILL POSE A RISK FOR
PERSONS LIVING ALONG THE IMMEDIATE COAST AND TO ANY MARITIME
PROPERTY. PERSONS WITH COASTAL OR MARITIME INTERESTS SHOULD STAY
TUNED FOR LATER UPDATES ON THIS SITUATION.
&&
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
NEAR TERM: EXPECT IFR CONDITIONS ALL AREAS TONIGHT DUE TO LOW
CEILING ...FOG AND RAIN.
SHORT TERM: MVFR/IFR CONDITIONS ARE EXPECTED AT ALL TERMINALS
THROUGH WEDNESDAY NIGHT AS RAIN ENDS AND FOG DEVELOPS. CONDITIONS
WILL IMPROVE TO VFR THURSDAY MORNING AND SHOULD REMAIN SO THROUGH
THURSDAY NIGHT. THEN MVFR RETURNS IN SHOWERS AND THUNDERSTORMS
FRIDAY AND ESPECIALLY FRIDAY AFTERNOON ASSOCIATED WITH COLD FRONT
PASSAGE. BRIEF LOCALIZED IFR CONDITIONS ARE POSSIBLE IN ANY
THUNDERSTORMS. VFR IS THEN EXPECTED SATURDAY WITH MORE SHOWERS AND
MVFR ON SUNDAY.
&&
.MARINE...
NEAR TERM: FOR WINDS HAVE USED A BLEND OF THE NAM12 AND GFS40.
WILL ADJUST WINDS INTO EARLY EVENING A LITTLE HIGHER. FOR WAVES:
PRIMARY WAVE GROUPS SPLIT BETWEEN INCREASING LONG PERIOD WAVES FROM
TROPICAL STORM LESLIE ...FROM 155 DEGREES/13-14 SECONDS... AND
DEVELOPING SOUTHEAST FETCH IN GULF OF MAINE ..FROM 190 DEGREES/5
SECONDS... HAVE INITIALIZED GRIDS WITH NAM/SWAN. WILL LOWER WAVE
HEIGHTS 1 FOOT BELOW MODEL NUMBER AS GULF OF MAINE FETCH LOOKS A
LITTLE TOO HIGH. WILL ADJUST SCA TO START AT 0300Z FOR SAME
REASON.
SHORT TERM: SMALL CRAFT ADVISORIES FOR HAZARDOUS SEAS HAVE BEEN
EXTENDED INTO THURSDAY MORNING AS WAVES WILL REMAIN ABOVE 5 FT IN
RESPONSE TO LOW PRESSURE MOVING THROUGH THE CANADIAN MARITIMES.
THOUGH THERE MAY BE A BRIEF BREAK FOR A FEW HOURS ON THURSDAY WHEN
WAVES WILL SUBSIDE TO BELOW 5 FT, SCA FOR SEAS WILL MOST LIKELY BE
NEEDED RIGHT THROUGH THE WEEKEND AS SWELLS FROM TROPICAL STORM
LESLIE AFFECT THE GULF OF MAINE WATERS.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 AM EDT
THURSDAY FOR ANZ050>052.
&&
$$
NEAR TERM...KHW/MCB
SHORT TERM...HASTINGS
LONG TERM...HASTINGS
AVIATION...KHW
MARINE...KHW/HASTINGS
AREA FORECAST DISCUSSION
NWS RALEIGH NC
331 AM EDT WED SEP 5 2012
.SYNOPSIS...
A MOIST AIRMASS WILL PERSIST OVER THE AREA THROUGH THURSDAY IN
ASSOCIATION WITH A STALLED SURFACE TROUGH OVER THE CAROLINAS. A
BRIEF DRY PERIOD IS EXPECTED ON FRIDAY...FOLLOWED BY A RETURN TO
UNSETTLED WEATHER OVER THE WEEKEND AS AN UNSEASONABLY DEEP UPPER
LEVEL TROUGH APPROACHES FROM THE WEST.
&&
.NEAR TERM /TODAY AND TONIGHT/...
AS OF 245 AM WEDNESDAY...
PRECIPITATION CHANCES:
AN H5 DISTURBANCE WAS NOTED IN WV IMAGERY AND RAP/MESOANALYSIS DATA
OVER THE WESTERN PIEDMONT AT 06Z THIS MORNING. THE DISTURBANCE IS
EXPECTED TO PROGRESSES SLOWLY EAST TO THE HWY 1 CORRIDOR BY 15-18Z
AND THE COASTAL PLAIN BY 18-21Z. THE LATEST RAP GUIDANCE INDICATES
THIS FEATURE WILL BECOME INCREASINGLY SHEARED/DEAMPLIFIED BY THE
AFTERNOON HOURS...AND IT IS DIFFICULT TO ASCERTAIN WHAT (IF ANY)
CONTRIBUTION TO ASCENT MAY BE ASSOCIATED WITH IT. LIGHT MID-LEVEL
FLOW WILL BE PRESENT OVER THE CAROLINAS TODAY...SOUTH OF THE PRIMARY
BELT OF WESTERLIES WHERE A WEAKNESS HAS DEVELOPED IN H5 RIDGE
EXTENDING WEST-EAST ACROSS THE SOUTHERN 1/3 OF THE CONUS...AND IT
WILL BE DIFFICULT FOR ANY ADDITIONAL MID/UPPER LEVEL DISTURBANCES TO
TRACK INTO THE AREA THROUGH TONIGHT. LOWER-LEVEL FORCING WILL BE
CONFINED TO CONVERGENCE ASSOC/W A WEAKENING SFC-H85 TROUGH OVER
WESTERN PORTIONS OF THE STATE TODAY...WITH THE BEST LOW-LEVEL
CONVERGENCE SHIFTING EAST INTO PORTIONS OF THE NW/NORTHERN PIEDMONT
OVERNIGHT. RELATIVELY SPEEDY (20-30 KT) SW LOW-LEVEL FLOW WILL BE
PRESENT ON THE EASTERN PERIPHERY OF THE TROUGH OVER CENTRAL NC. WEAK
MID-LEVEL LAPSE RATES AND BROKEN CLOUD COVER WILL LIMIT DIURNAL
DESTABILIZATION IN THE WEST TODAY...WITH MLCAPE VALUES OF ~1000 J/KG
OR LESS. ALTHOUGH STRONGER INSOLATION MAY BE PRESENT IN EASTERN
PORTIONS...WEAK MID-LEVEL LAPSE RATES COUPLED WITH A RELATIVELY
DRIER BOUNDARY LAYER SHOULD LIMIT MLCAPE VALUES TO 1000-1500
J/KG...THOUGH UP TO 2000 J/KG WILL BE POSSIBLE IF BOUNDARY LAYER
MOISTURE IS GREATER THAN PROGGED. ABOVE NORMAL MOISTURE WILL BE
PRESENT THROUGHOUT THE COLUMN TODAY/TONIGHT...WITH PWAT VALUES
PROGGED NEAR 2.00" EVERYWHERE.
THE LATEST 00Z CONVECTION ALLOWING MODELS (CAMS) INDICATE CONVECTION
DEVELOPING ON THE EASTERN PERIPHERY OF THE WEAKENING H5 DISTURBANCE
IN VICINITY OF THE HWY 1 CORRIDOR BETWEEN 12-18Z TODAY...SHIFTING
EAST INTO THE COASTAL PLAIN BY MID/LATE AFTERNOON. THE CAMS ALSO
INDICATE CONVECTION DEVELOPING IN VICINITY OF THE SFC-H85 TROUGH
OVER THE FOOTHILLS/MOUNTAINS THIS AFTERNOON...SHIFTING INTO PORTIONS
OF THE NW/NORTHERN PIEDMONT OVERNIGHT IN ASSOCIATION WITH WEAK
LOW-LEVEL CONVERGENCE IN THE PRESENCE OF A VERY MOIST AND MARGINALLY
UNSTABLE AIRMASS. WILL BASE PRECIP CHANCES THROUGH TONIGHT ON THE
AFOREMENTIONED REASONING...HOWEVER...CONFIDENCE IN THE TIMING/
COVERAGE OF CONVECTION REMAINS RELATIVELY LOW GIVEN THE PRESENCE OF
WEAK STEERING FLOW.
TEMPERATURES:
WITH RELATIVELY LITTLE CHANGE IN AIRMASS...HIGHS TODAY WILL BE
SIMILAR TO PREVIOUS DAYS...DEPENDING PRIMARILY ON CLOUD COVER AND
CONVECTION. WILL INDICATE HIGHS RANGING FROM THE LOWER/MID 80S WEST
TO MID/UPPER 80S EAST. LOWS TONIGHT WILL ALSO BE BASED ON
PERSISTENCE...IN THE LOWER 70S.
HAZARDOUS WEATHER:
VERY WEAK DEEP-LAYER SHEAR WILL BE UNSUPPORTIVE OF CONVECTIVE
ORGANIZATION TODAY. GIVEN AN INCREASINGLY DEAMPLIFIED PATTERN OVER
THE CAROLINAS...A THERMODYNAMIC ENVIRONMENT CHARACTERIZED BY LOW
DCAPE AND WEAK MID-LEVEL LAPSE RATES...THE THREAT FOR AN ISOLD
SEVERE STORM WILL BE VERY LOW...THOUGH NON-ZERO (AS LONG AS DEEP
CONVECTION IS PRESENT) GIVEN ENHANCED (~25 KT) LOW-LEVEL FLOW AND A
VERY MOIST COLUMN SUPPORTIVE OF PRECIP LOADING. LOCALLY HEAVY
RAINFALL AND ISOLD FLOODING CANNOT BE RULED OUT IN URBAN AREAS...
THOUGH THE THREAT APPEARS LOWER THAN PREVIOUS DAYS. -VINCENT
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 230 AM WEDNESDAY...
THERE IS A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS AGAIN THURSDAY
AFTERNOON AND EVENING AS A WEAKENING COLD FRONT IS FORECAST TO STALL
ACROSS CENTRAL NORTH CAROLINA THURSDAY. THE UPPER DYNAMICS WILL BE
VERY WEAK. HOWEVER... CONTINUED HI PW`S AND STRONG HEATING
ESPECIALLY IN THE SOUTH AND EAST WILL SUPPORT SCATTERED STRONG
THUNDERSTORMS... WITH THE PRIMARY THREATS OF LOCALLY HEAVY RAIN AND
GUSTY WIND. WE WILL CARRY THE HIGHEST POP IN THE EAST AND SOUTH...
BUT EVEN THE NW WILL HAVE LOW CHANCE POPS. HIGHS IN THE MID TO UPPER
80S NW RANGING TO AROUND 90 SE. THE POPS WILL BECOME SLIGHT CHANCE
BY LATE EVENING THURSDAY... SUPPORTED BY THE LINGERING NEARLY
STATIONARY BOUNDARY. LOWS GENERALLY 70-73.
FRIDAY AND FRIDAY NIGHT... THIS MAY BE THE DAY WHEN WE HAVE THE
LOWEST POPS... ESPECIALLY OVER THE PIEDMONT WHERE SOME DRIER AIR
(VERY SLIGHTLY DRIER AIR MAY FILTER IN WITH DEW POINTS IN THE MID
60S). THAT IS... IF... THE LOW LEVEL BOUNDARY DRIFTS INTO THE
COASTAL PLAIN OR WASHES OUT ENTIRELY PER SOME MODEL SOLUTIONS. THIS
APPEARS POSSIBLE... YET BY LATE IN THE DAY EXPECT THE SEA BREEZE/OLD
FRONT COMBO TO DRIFT BACK WNW INTO THE EASTERN PIEDMONT BY EARLY
EVENING BRINGING BACK 70+ DEW POINTS. WE WILL STILL CARRY SLIGHT TO
LOW CHANCE POP FOR SHOWERS AND THUNDERSTORMS... MAINLY FROM FAY AND
RDU EASTWARD DURING FRIDAY AFTERNOON AND EARLY EVENING. OTHERWISE...
PARTLY SUNNY WARM AND HUMID. HIGHS 88-94 NW TO SANDHILLS.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 245 AM WEDNESDAY...
BIG PATTERN CHANGE IN THE OFFING...
A FAIRLY DEEP MID-UPPER LEVEL TROUGH IS FORECAST TO DEVELOP OVER THE
GREAT LAKES AND SWING EASTWARD OVER THE WEEKEND. THE ACTUAL COLD
FRONT IS PROJECTED FOR SATURDAY. THIS WILL SWEEP THE VERY MUGGY
OPPRESSIVE AIR MASS CURRENTLY OVER THE AREA OUT TO SEA SUNDAY AND
MONDAY. THE MODELS HAVE BEEN TRENDING TOWARD A MORE PROGRESSIVE
TROUGH PASSAGE FOR OUR REGION AND LATITUDE. THIS WOULD MEAN LESS IN
THE WAY OF SEVERE AND FLOODING POTENTIAL OVER THE WEEKEND. STAY
TUNED.
WE WILL CONTINUE TO CARRY INCREASING CHANCES OF SHOWERS AND STORMS
SAT-SAT NIGHT... SHIFTING EAST MORE QUICKLY SUNDAY. MODELS NOW
PROJECT THE ACTUAL FRONT TO PUSH EAST THROUGH OUR REGION BY LATE
SATURDAY. THIS WOULD MEAN LOWERING HUMIDITIES AND MUCH LOWER POP FOR
SUNDAY (A DAY TO A DAY AND A HALF EARLIER THAN PROJECTED 24 HOURS
AGO). WE WILL TREND THAT WAY... BUT KEEP A CHANCE POP MAINLY EAST
SUNDAY.
TURNING COOLER AND MUCH DRIER MONDAY AND TUESDAY. LOWS 55-60. HIGHS
77-82.
&&
.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
AS OF 200 AM WEDNESDAY...
24-HR TAF PERIOD:
A MOIST/SPEEDY (25 KT AT 1000 FT AGL) LOW-LEVEL FLOW IS EXPECTED TO
RESULT IN THE DEVELOPMENT OF IFR CEILINGS AT ALL AVIATION TERMINALS
BETWEEN 08-10Z THIS MORNING...PERSISTING THROUGH 13Z...THEN LIFTING
TO MVFR AND EVENTUALLY SCATTERING OUT TO VFR IN MOST LOCATIONS BY
15Z. EXCEPTIONS INCLUDE THE INT/GSO TERMINALS WHERE MVFR CEILINGS
COULD PERSIST THROUGH THE AFTERNOON. LIFR FOG HAS DEVELOPED THE PAST
SEVERAL MORNINGS BETWEEN 10-12Z AT THE FAY/RWI TERMINALS AND
PERSISTENCE WOULD SUGGEST SIMILAR CONDITIONS THIS MORNING...
HOWEVER...A SOMEWHAT TIGHTER MSLP GRADIENT AND PERSISTENT SOUTHERLY
BREEZE MAY PREVENT VISBYS FROM FALLING BELOW MVFR. EXPECT THE BEST
CHANCE OF CONVECTION AT THE INT/GSO TERMINALS BETWEEN 15Z THIS
MORNING AND 03Z THIS EVENING...WHERE VCSH WILL BE MENTIONED. AT THE
RDU/FAY/RWI TERMINALS...CONFIDENCE IN AFTERNOON CONVECTION IS LOWER
THAN AT INT/GSO. AS A RESULT...WILL KEEP VFR CONDITIONS IN PLACE AT
RDU/FAY/RWI ONCE MORNING FOG AND STRATUS HAS LIFTED AND SCATTERED
OUT. OTHERWISE...ANTICIPATE A CHANCE FOR IFR CEILINGS/VISBYS ONCE
AGAIN BY THE END OF THE TAF PERIOD...06-12Z THURSDAY MORNING.
LOOKING AHEAD:
SUB-VFR STRATUS OR FOG WILL BE POSSIBLE DURING THE EARLY MORNING
HOURS (07-13Z) ON BOTH FRI/SAT...ALONG WITH ISOLD SHOWERS AND STORMS
DURING THE AFTERNOON AND EARLY EVENING HOURS...PRIMARILY AT THE
FAY/RWI TAF SITES. MORE WIDESPREAD SHOWERS/STORMS WILL BE POSSIBLE
SATURDAY NIGHT/SUNDAY AS AN UNSEASONABLY DEEP UPPER LEVEL TROUGH
APPROACHES FROM THE WEST. -VINCENT
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...VINCENT
NEAR TERM....VINCENT
SHORT TERM...BADGETT
LONG TERM...BADGETT
AVIATION...VINCENT
AREA FORECAST DISCUSSION
NWS RALEIGH NC
245 AM EDT WED SEP 5 2012
.SYNOPSIS...
A WARM AND MOIST AIR MASS WILL PERSIST OVER THE AREA THROUGH
THURSDAY... AS A LINGERING TROUGH OF LOW PRESSURE HOLDS OVERHEAD. A
BIG PATTERN CHANGE IS EXPECTED BY LATE IN THE WEEKEND AND EARLY NEXT
WEEK AS MUCH DRIER AND COOLER AIR WILL ARRIVE FROM THE UPPER
MIDWEST.
&&
.NEAR TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
AS OF 805 PM TUESDAY...
THE LATEST SURFACE ANALYSIS SHOWED A WEAK SURFACE TROUGH OVER THE
FAR WESTERN PIEDMONT...ALSO SHOWING UP ON MSAS AS AN AREA OF WEAK
SURFACE CONVERGENCE. HOWEVER...PARTIALLY DUE TO LIMITED
INSTABILITY...A RELATIVE MINIMUM OF THAT IN VICINITY OF THE TROUGH
ON THE LATEST MSAS...STORMS WERE HAVING A HARD TIME BECOMING ROBUST.
WHERE THE GREATER INSTABILITY WAS OVER THE COASTAL PLAIN...WITH MSAS
LIFTED INDEX VALUES NEARLY TO -5C...SLIGHTLY DRIER AIR AND MORE
OVERALL CIN AS NOTED ON NEAR-TERM NAM AND GFS BUFR SOUNDINGS WERE
LIKELY CONTRIBUTING TO SCANT DEVELOPMENT AS OF THIS WRITING.
OVERNIGHT...BOTH THE 18Z AND THE LATEST RAP DIMINISH LIFT BY 06Z...
AND EVEN THE GFS...WITH QPF LINGERING LONGER THROUGH THE OVERNIGHT
DESPITE STABILIZING BUFR SOUNDINGS IN CENTRAL NORTH CAROLINA...HAS
850MB LIFT DIMINISHING AS CONVERGENCE ALOFT INCREASES. THE LATEST
RADAR TRENDS SUPPORT THE LATEST HRRR WRF...WITH MUCH OF THE DEEP
CONVECTION HAVING DIMINISHED BY 05Z.
HIGHER PRECIPITABLE WATER AIR SPREADS EAST OVERNIGHT...SO THAT BY
12Z BASICALLY ALL OF CENTRAL NORTH CAROLINA IS IN A SIMILAR AIR MASS
WITH PRECIPITABLE WATER VALUES AROUND TWO INCHES AND K INDICES AT OR
APPROACHING THE MID 30S. SURFACE-BASED AND DCAPE VALUES FALL...AND
THE NAM ACTUALLY SEEMS TO FORECAST A SLIGHT INCREASE IN SURFACE
RIDGING THAT MAY HELP TO LIMIT DEVELOPMENT OVERNIGHT. IN THE MOIST
AIR MASS...AND WITH A SHEAR AXIS ALOFT OR JUST OFF TO OUR WEST...
WILL CONTINUE THE ISOLATED SHOWERS OVERNIGHT IN THE FORECAST...BUT
CURRENTLY IT IS EXPECTED MOST LOCATIONS LATE TONIGHT SHOULD REMAIN
DRY.
SREF PROBABILITIES OF VISIBILITIES BELOW 3 MILES ARE LIMITED
OVERNIGHT...IN CONCERT WITH THE LATEST MOS GUIDANCE...WHILE SREF
PROBABILITIES OF LOW CLOUDS ARE MOSTLY ABOVE 50 PERCENT BY 12Z
WEDNESDAY. THIS IS CONSISTENT WITH THE LATEST GFS AND NAM BUFR
SOUNDINGS. SHOULD BE PATCHY FOG AT BEST TOWARD THE COASTAL PLAIN
WHERE THE INCREASING CLOUDS SHOULD BE NOTED LATER...WITH FOG LIMITED
BY SOME WIND...ALBEIT LIGHT...CONTINUING OVERNIGHT. OVERNIGHT LOWS
NEAR PERSISTENCE...MAINLY 70 TO 73. -DJF
WEDNESDAY AND WEDNESDAY NIGHT:
STRONG DAYTIME HEATING WILL SERVE TO RENEW CONVECTIVE INITIATION
ACROSS CENTRAL NC WEDNESDAY AFTERNOON...FOCUSED ALONG THE LINGERING
SUBTROPICAL MOISTURE PLUME CONFINED WITHIN THE LOWER-MID LEVEL
TROUGH AXIS RESIDING OVER THE AREA. VERY SIMILAR TO THE PAST FEW
DAYS...THE MAIN CONCERN WILL BE FROM TRAINING...HEAVY RAIN PRODUCING
THUNDERSTORMS...WITH A SECONDARY/ISOLATED SEVERE THREAT DUE TO WEAK
WINDS ALOFT AND WEAK FORCING.
HIGHS WILL DEPEND ON HOW SOON WE GET CONVECTION TO POP...BUT WESTERN
PIEDMONT PORTIONS OF THE AREA SHOULD BE A GOOD 2 TO 3 DEGREES COOLER
THAN CENTRAL AND EASTERN AREAS WITH DELAYED HEATING FROM SLOWER
BREAKUP/BURN OFF OF MORNING STRATUS/FOG. HIGHS IN THE MID 80S NW TO
NEAR 90 JUST ABOUT EVERYWHERE ELSE. LOWS WEDNESDAY NIGHT THE LOWER
70S WITH AREAS OF STRATUS AND FOG. -CBL
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 230 AM WEDNESDAY...
THERE IS A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS AGAIN THURSDAY
AFTERNOON AND EVENING AS A WEAKENING COLD FRONT IS FORECAST TO STALL
ACROSS CENTRAL NORTH CAROLINA THURSDAY. THE UPPER DYNAMICS WILL BE
VERY WEAK. HOWEVER... CONTINUED HI PW`S AND STRONG HEATING
ESPECIALLY IN THE SOUTH AND EAST WILL SUPPORT SCATTERED STRONG
THUNDERSTORMS... WITH THE PRIMARY THREATS OF LOCALLY HEAVY RAIN AND
GUSTY WIND. WE WILL CARRY THE HIGHEST POP IN THE EAST AND SOUTH...
BUT EVEN THE NW WILL HAVE LOW CHANCE POPS. HIGHS IN THE MID TO UPPER
80S NW RANGING TO AROUND 90 SE. THE POPS WILL BECOME SLIGHT CHANCE
BY LATE EVENING THURSDAY... SUPPORTED BY THE LINGERING NEARLY
STATIONARY BOUNDARY. LOWS GENERALLY 70-73.
FRIDAY AND FRIDAY NIGHT... THIS MAY BE THE DAY WHEN WE HAVE THE
LOWEST POPS... ESPECIALLY OVER THE PIEDMONT WHERE SOME DRIER AIR
(VERY SLIGHTLY DRIER AIR MAY FILTER IN WITH DEW POINTS IN THE MID
60S). THAT IS... IF... THE LOW LEVEL BOUNDARY DRIFTS INTO THE
COASTAL PLAIN OR WASHES OUT ENTIRELY PER SOME MODEL SOLUTIONS. THIS
APPEARS POSSIBLE... YET BY LATE IN THE DAY EXPECT THE SEA BREEZE/OLD
FRONT COMBO TO DRIFT BACK WNW INTO THE EASTERN PIEDMONT BY EARLY
EVENING BRINGING BACK 70+ DEW POINTS. WE WILL STILL CARRY SLIGHT TO
LOW CHANCE POP FOR SHOWERS AND THUNDERSTORMS... MAINLY FROM FAY AND
RDU EASTWARD DURING FRIDAY AFTERNOON AND EARLY EVENING. OTHERWISE...
PARTLY SUNNY WARM AND HUMID. HIGHS 88-94 NW TO SANDHILLS.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 245 AM WEDNESDAY...
BIG PATTERN CHANGE IN THE OFFING...
A FAIRLY DEEP MID-UPPER LEVEL TROUGH IS FORECAST TO DEVELOP OVER THE
GREAT LAKES AND SWING EASTWARD OVER THE WEEKEND. THE ACTUAL COLD
FRONT IS PROJECTED FOR SATURDAY. THIS WILL SWEEP THE VERY MUGGY
OPPRESSIVE AIR MASS CURRENTLY OVER THE AREA OUT TO SEA SUNDAY AND
MONDAY. THE MODELS HAVE BEEN TRENDING TOWARD A MORE PROGRESSIVE
TROUGH PASSAGE FOR OUR REGION AND LATITUDE. THIS WOULD MEAN LESS IN
THE WAY OF SEVERE AND FLOODING POTENTIAL OVER THE WEEKEND. STAY
TUNED.
WE WILL CONTINUE TO CARRY INCREASING CHANCES OF SHOWERS AND STORMS
SAT-SAT NIGHT... SHIFTING EAST MORE QUICKLY SUNDAY. MODELS NOW
PROJECT THE ACTUAL FRONT TO PUSH EAST THROUGH OUR REGION BY LATE
SATURDAY. THIS WOULD MEAN LOWERING HUMIDITIES AND MUCH LOWER POP FOR
SUNDAY (A DAY TO A DAY AND A HALF EARLIER THAN PROJECTED 24 HOURS
AGO). WE WILL TREND THAT WAY... BUT KEEP A CHANCE POP MAINLY EAST
SUNDAY.
TURNING COOLER AND MUCH DRIER MONDAY AND TUESDAY. LOWS 55-60. HIGHS
77-82.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AS OF 745 PM TUESDAY...
CONFIDENCE IS HIGH THAT AVIATION CONDITIONS WILL DETERIORATE AFTER
NIGHTFALL... AND PARTICULARLY AFTER MIDNIGHT... AT ALL CENTRAL NC
TERMINAL FORECAST SITES. THE RISK OF A SHOWER OR ISOLATED STORM WILL
PERSIST NEAR INT/GSO THROUGH 04Z BUT THE CHANCE WILL QUICKLY
DIMINISH AFTER 02Z. ELSEWHERE AT RDU/FAY/RWI... THE CHANCE OF A
SHOWER OR STORM FOR THE REMAINDER OF THE NIGHT IS VERY SMALL. AFTER
04Z... THE RECENT RAINS AND RESULTANT WET GROUND COMBINED WITH VERY
LIGHT WIND FROM THE SE OR SOUTH WILL FAVOR DEVELOPMENT OF LOW
STRATUS AFTER MIDNIGHT. SREF AVIATION PROBABILITIES SHOW A VERY GOOD
CHANCE OF CIGS UNDER 1 KFT OVERNIGHT... ESPECIALLY AT INT/GSO... AND
FORECAST SOUNDINGS SUGGEST THAT CIGS COULD BE LOWER THAN 600 FT AGL.
EXPECT AROUND A 200-500 FT CIG AT ALL SITES AFTER 07Z OR 08Z
TONIGHT... HOLDING THROUGH AROUND 13Z WHEN THE CLOUDS WILL BEGIN TO
LIFT AND MIX OUT TO SCATTERED. VSBYS WILL BE GENERALLY MVFR BETWEEN
07Z AND 13Z... ALTHOUGH VSBYS COULD GET LOWER AT TOWERS... AS CIGS
LOWER. VFR CONDITIONS ARE EXPECTED TO RETURN AFTER 13Z OR 14Z
WEDNESDAY MORNING. THE CHANCE FOR STORMS WEDNESDAY AFTERNOON DOES
NOT APPEAR TO BE HIGH ENOUGH TO INCLUDE AS A PREVAILING CONDITION AT
THIS TIME... BUT THE MOST LIKELY LOCATION OF ANY STORMS WEDNESDAY
AFTERNOON WILL BE AT INT/GSO/RDU.
LOOKING BEYOND 00Z THURSDAY (WEDNESDAY EVENING)... ANOTHER ROUND OF
LOW CIGS AND VSBYS IS EXPECTED LATE WEDNESDAY NIGHT INTO THURSDAY
MORNING AREAWIDE. WE MAY SEE A BRIEF RESPITE FROM THE DAILY
SLOW-MOVING HEAVY-RAIN-PRODUCING STORMS FROM FRIDAY INTO SATURDAY...
HOWEVER MORE RAIN AND STORMS ARE EXPECTED SUNDAY. -GIH
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...BADGETT
NEAR TERM....DJF/CBL
SHORT TERM...BADGETT
LONG TERM...BADGETT
AVIATION...HARTFIELD
AREA FORECAST DISCUSSION
NWS NEWPORT/MOREHEAD CITY NC
1045 PM EDT TUE SEP 4 2012
.SYNOPSIS...
A TROUGH OF LOW PRESSURE REMAINS ANCHORED WEST OF THE REGION
THROUGH WEDNESDAY. A COLD FRONT WILL MOVE INTO THE AREA ON FRIDAY.
THE FRONT WILL LIFT NORTH AS A WARM FRONT AN SATURDAY. A STRONGER
COLD FRONT WILL PUSH THROUGH THE AREA LATE SUNDAY OR EARLY MONDAY.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
AS OF 10 PM TUE...CURRENT FORECAST IN GOOD SHAPE. MADE MINOR
ADJUSTMENTS TO REFLECT OBS. OVERALL...MOSTLY CLEAR TO PARTLY
CLOUDY SKIES ACROSS THE AREA. ADJUSTED POPS TO REFLECT SLIGHT
CHANCE OF PRECIP ALONG THE OBX...AS BOTH THE HRRR AND WRF MODELS
INDICATES MOISTURE ACROSS THE OCEAN. THE DEVELOPMENT OF SOME
PATCHY FOG IS STILL FORECASTED MAINLY. IN THE INLAND AREAS AS WINDS
WILL BE LIGHT. ANY FOG FORMATION WILL BE MIXING OUT AFTER SUNRISE.
EXPECT TEMPS TO RANGE IN THE LOW 70S INLAND AS THE COASTAL AREAS
TO BE IN THE MID-UPPER 70S.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
AS OF 330 PM TUE...BROAD LONG WAVE
TROUGH WILL DEEPEN SOMEWHAT ON THUR ACROSS THE SOUTHERN
APPALACHIANS. LOW LEVEL TROUGH/COLD FRONT WILL SHARPEN ACROSS THE
WESTERN CAROLINAS. AREA OF SHOWERS AND STORMS EXPECTED TO DEVELOP
WEST OF EASTERN NC BY AFTERNOON. BULK OF GUIDANCE KEEPS ORGANIZED
ACTIVITY AWAY FROM THE FA...THOUGH SOME PRECIP MAY PUSH THROUGH
FAR NORTHER TIER...MAINLY NORTH OF PGV TO MQI LINE.
OTHERWISE...SLIGHT CHANCE POPS REMAINER OF THE FA WITH PARTLY
SUNNY SKIES EXPECTED. HIGHS EXPECTED TO REACH 90 FOR MOST
AREAS...THOUGH A TOUCH COOLER FURTHER NORTH AND WEST WHERE MORE
CLOUDS MAY BE PRESENT.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
AS OF 300 PM TUESDAY...LATEST MODELS INDICATE GOOD CONTINUITY WITH
PREVIOUS FCST THINKING. WESTERN EXTENSION OF SUB-TROPICAL RIDGE WILL
CONTINUE TO HOLD OVER AREA WED NIGHT AND THU...THEN BEGIN TO WEAKEN
THU NIGHT AND FRI AS STRONG NRN STREAM TROF BEGINS TO DIG OVER NRN
PLAINS AND WEAK UPR LOW OFF SRN FLA MOVES N-NE. RIDGING WILL TEND TO
SUPPRESS CONVECTIVE DEVELOPMENT ALONG COAST WHILE WEAK UPR TROFFING
INLAND SOULED STILL SUPPORT SCT ACTIVITY OVER LAND...THUS CONTINUED
MAINLY 30-40 POPS INLAND WITH JUST SLGT CHC ALONG COAST. TEMPS
REMAINING ABOVE NORMAL WITH LOWS IN 70S AND HIGHS MID-UPR 80S.
FOR SAT-TUE...12Z ECMWF AND GFS40 HAVE TRENDED TOWARD MORE
PROGRESSIVE SOLUTIONS WITH DEEP UPR TROF MOVING ACROSS AREA OVER THE
WEEKEND...RATHER THAN SLOW MOVING UPR LOW. HOWEVER FCST CONFIDENCE
IS BELOW NORMAL PER HPC EXTENDED DISCUSSION DUE TO MODEL
FLIP-FLOPS...THUS ONLY MINOR ADJUSTMENTS TO PREVIOUS FCST. CONTINUED
NEAR CLIMO 20/30 POPS FOR SAT AND SAT NIGHT...BUT DID INCREASE POPS
TO 50% FOR SUN AND SUN NIGHT WITH GOOD MODEL AGREEMENT ON GOOD CHC
OF SHOWER/TSTMS WITH UPR TROF ENERGY.
PROGRESSIVE UPR TROF PASSAGE WOULD LEAD TO DRY CONDITIONS FOR MON
NIGHT AND TUE...BUT KEPT 20 POPS DURING PERIOD GIVEN BELOW NORMAL
MODEL CONFIDENCE AND SOME THREAT OF SLOWER TROF PASSAGE AND/OR UPR
LOW DEVELOPMENT. TEMPS COOLING TO SLIGHTLY BELOW NORMAL FOR MON-TUE.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
SHORT TERM /THROUGH WEDNESDAY/...
AS OF 730 PM TUE...VFR CONDITIONS EXPECTED FOR THE EARLY EVENING HOURS
THEN IFR CONDITIONS AFTER MIDNIGHT. WITH LOW LEVEL MOISTURE AND
LIGHT AND VARIABLE WINDS...EXPECT PATCHY FOG FORMATION ACROSS THE
TAF SITES. ANY FOG FORMATION AND/OR LOW STRATUS WILL QUICKLY MIX OUT AFTER
SUNRISE. EXPECT SCT TO BKN 4K FT CEILING WITH SOME HIGHER CLOUDS
TO STREAMING ACROSS THE AREA ON WED.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... AS OF
330 AM TUESDAY...PERIOD OF SUB-VFR WITH SCT CONVECTIVE ACTIVITY
WILL CONTINUED WED NIGHT THROUGH SAT NIGHT WITH WEAK UPR TROFFING.
SHOWERS AND TSTMS EXPECTED TO BE MORE WDSPRD SUN AND SUN NIGHT
WITH STRONGER UPR TROF AND ASSCTD COLD FRONT.
&&
.MARINE...
.SHORT TERM /THROUGH WEDNESDAY/...
AS OF 10 PM TUE...MARINE FORECAST CONTINUES TO BE ON TRACK. CURRENT
BUOY OBS IN THE NORTHERN WATERS ARE BTW 4 TO 6 FEET AS THE
SOUTHERN WATERS ARE BTW 4 TO 5 FEET. SEAS ARE EXPECTED TO BUILD
OVERNIGHT. AS SWELLS FROM TROPICAL CYCLONE LESLIE CONTINUES TO
REACH OUR COASTAL WATERS WITH LONG PERIOD SWELL OF 13-14 SECOND.
BASED FCST THROUGH WED ON WW4...AS SWAN SEEMS A BIT TOO BULLISH ON
BUILDING SEAS TO ABOVE 7 FEET TOO QUICKLY. EXPECT SEAS TO BE 4 TO
6 FEET THROUGH THE DAY ON WED. WINDS WILL BE SOUTHERLY TO
SOUTHWESTERLY AT 10 TO 15 KT WITH GUSTS UP TO 20 KT BY WED.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 300 PM TUESDAY...MAIN IMPACT DURING PERIOD WILL BE INCREASED
SWELL ENERGY ASSCTD WITH TS LESLIE. LESLIE IS EXPECTED TO MOVE
SLOWLY TOWARDS BERMUDA AND IS FORECAST TO BECOME QUITE LARGE...WHICH
WILL AID IN PRODUCING LONG PERIOD SWELLS OF 13-15 SECONDS FROM MID
WEEK THROUGH THE WEEKEND. WAVE MODELS TYPICALLY HAVE A DIFFICULT
TIME HANDLING THIS KIND OF SWELL AND USED A BLEND OF PREVIOUS
FCST...SWAN AND WW3 DURING PERIOD. SWELL EXPECTED TO INCREASE TO AT
LEAST 5 TO 7 FEET THURSDAY INTO THE WEEKEND. CLOSEST APPROACH OF
LESLIE LIKELY ON SUNDAY...WITH SWELL OF 8-10 FEET PSBL. THIS WILL
PRODUCE HIGH THREAT OF DANGEROUS RIP CURRENTS...AND COULD SEE HIGH
SURF ADVISORY CONDITIONS ALONG WITH COASTAL FLOOD THREAT FOR
SUSCEPTIBLE AREAS ON OUTER BANKS.
OTHER THAN SCA FOR LARGE SEAS THROUGH PERIOD...S-SW WINDS AROUND 15
KT OR LESS EXPECTED TO PREVAIL WITH FRONTS REMAIN N AND W.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...BEACH HAZARDS STATEMENT THROUGH WEDNESDAY EVENING FOR NCZ095-
098-103-104.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EDT SATURDAY FOR AMZ150-152-
154-156-158.
&&
$$
SYNOPSIS...TL
NEAR TERM...BM
SHORT TERM...TL
LONG TERM...JBM
AVIATION...JBM/BM
MARINE...JBM/TL/BM
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
1105 PM CDT TUE SEP 4 2012
.DISCUSSION.../ISSUED AT 1005 PM CDT/
THUNDERSTORMS WITH SEVERE WEATHER HAVE BEEN MOVING EAST OVER AREA
THIS EVENING INCLUDING CURRENT DAMAGING WIND EVENT IN NORTHWEST IOWA
AND SOUTHWEST MINNESOTA. IF TRENDS CONTINUE AND NOTHING DEVELOPS
BEHIND THESE STORMS WE MAY BE ABLE TO CUT THEM BACK SOONER BUT FOR
NOW WILL HOLD IN.
&&
.AVIATION.../FOR THE 06Z TAF ISSUANCE/
THUNDERSTORMS EASTERN PART OF AREA SHOULD BE JUST EAST OF KSUX AND
WELL EAST OF KHON AND KFSD AT START 0F FORECAST PERIOD/ 06Z. VERY
LOCAL VISIBILITIES AND STRONG WINDS IN THUNDERSTORMS FAR EASTERN
PART OF AREA IN SOUTHWEST MN AND NORTHWEST IA SHOULD END BY 09Z.
OTHERWISE VFR OVER AREA THROUGH 06/06Z. A FEW SURFACE GUSTS AROUND
25 KNOTS FROM THE NORTHWEST OVER AREA 15Z-22Z.
&&
.PREV DISCUSSION.../ISSUED AT 325 PM CDT/
DIFFUSE BOUNDARY IN NORTHWEST IOWA BEGINNING TO LIFT NORTHWARD AS A
WARM FRONT THIS AFTERNOON AS SURFACE LOW PRESSURE STRENGTHENS OVER
THE BLACK HILLS. MIXING HAS ALLOWED DEWPOINTS TO DRAMATICALLY FALL
THIS AFTERNOON ACROSS THE NORTHWESTERN TWO THIRDS OF THE CWA...WHILE
DEEPER MOISTURE HAS ALLOWED DEWPOINTS TO REMAIN IN THE 60S ACROSS
NORTHWEST IOWA. INSTABILITY CONTINUES TO INCREASE THIS
AFTERNOON...ESPECIALLY ACROSS OUR SOUTHEASTERN HALF OF THE FORECAST
AREA WHERE CAPE VALUES ARE GREATER THAN 1500 J/KG...WITH INCREASING
LAPSE RATES AND STRENGTHENING WESTERLIES BRINGING SHEAR UP AROUND 40
KT.
SO FAR...CAPPING IS PREVENTING CONVECTION FROM DEVELOPING...HOWEVER
WITH KSUX ALREADY 95/65 EXPECT THE CAPPING TO BE SURPASSED SOON.
THE HRRR AND NAM CONTINUE TO DEPICT CONVECTION MOVING NORTHEASTWARD
INTO THE MISSOURI VALLEY...EXTREME SOUTHEAST SOUTH DAKOTA AND
NORTHWEST IOWA LATE THIS AFTERNOON THROUGH THE EVENING. IF
CONVECTION DOES MANAGE TO FIRE IN THIS AREA...STORMS COULD
POTENTIALLY BECOME SEVERE WITH LARGE HAIL TO AROUND WALNUT SIZE AND
WIND GUSTS TO 70 MPH.
FURTHER WEST...HIGH BASED CUMULUS FIELD NOW MOVING INTO OUR WESTERN
BORDER. ISOLATED HIGH BASED CONVECTION WILL BE POSSIBLE IN OUR
WESTERN HALF THIS AFTERNOON AND EVENING...BUT EXPECT LITTLE TO NO
SEVERE WEATHER IN THIS AREA WITH SUCH DRY LOW AND MID LEVELS. AS THE
LOW BEGINS TRACKING EAST NORTHEAST ACROSS THE FORECAST AREA THIS
EVENING AND OVERNIGHT...THE TRAILING COLD FRONT WILL SHIFT THE
CONVECTION INTO CENTRAL AND EASTERN PORTIONS OF THE FORECAST AREA
WHERE CONDITIONS ARE MORE FAVORABLE FOR PRECIPITATION. WINDS WILL
LIKELY BECOME FAIRLY BREEZY FROM THE WEST NORTHWEST LATE TONIGHT.
LOWS TONIGHT WILL RANGE FROM THE MID 50S FAR NORTHWEST TO THE MID
60S FAR SOUTHEAST.
RELATIVELY QUIET WEATHER WITH MILDER TEMPERATURES EXPECTED FOR
WEDNESDAY AS SURFACE HIGH PRESSURE SETTLES IN BEHIND THE EXITING
SYSTEM. NORTH NORTHWEST WINDS WILL REMAIN A LITTLE BREEZY THROUGH
THE DAY...BUT SKIES WILL BE SUNNY AND HIGHS ARE EXPECTED IN THE 70S.
/
HIGH PRESSURE WILL BUILD IN OVER THE AREA FOR WEDNESDAY NIGHT. THUS
TRENDED LOWS TOWARDS THE COOLER SIDE OF GUIDANCE...GENERALLY UPPER
40S TO LOWER 50S. A MID LEVEL WAVE AND SOME CLOUD COVER MAY BEGIN
ENTERING OUR WEST BY LATE NIGHT...THUS DID NOT GO QUITE AS COOL AS I
WOULD HAVE IF COMPLETELY CLEAR SKIES WERE MORE LIKELY. MID LEVEL
FORCING OVERHEAD ON THURSDAY OUT AHEAD OF OUR NEXT WAVE...ALSO
SHOULD SEE DECENT ISENTROPIC LIFT. ATMOSPHERE WILL BE ON THE DRY
SIDE THOUGH...THUS FOLLOWED THE NAM AND GFS IDEA OF A DRY DAY.
HOWEVER SHOULD SEE AT LEAST SOME MID LEVEL CLOUD COVER...AND WITH
DECENT MID LEVEL LAPSE RATES...WOULD NOT BE SURPRISED TO SEE A FEW
ELEVATED SHOWERS AND THUNDERSTORMS. THINK THE ECMWF IS PROBABLY
OVERDOING CONVECTION THURSDAY...BUT LOW POPS MAY NEED TO BE ADDED ON
FUTURE SHIFTS IF MODELS TREND A LITTLE MOISTER IN THE MID LEVELS.
WITH UNCERTAINTY ON CLOUD COVER...FOLLOWED A BLEND OF THE COOLER MOS
AND THE WARMER BIAS CORRECTED NAM FOR HIGHS...GENERALLY MID 70S
SOUTHWEST MINNESOTA TO LOW TO MID 80S ELSEWHERE. SURFACE LOW TO OUR
WEST ON THURSDAY WILL PRODUCE BLUSTERY SOUTH SOUTHEAST WINDS WEST OF
THE JAMES RIVER...WITH GUSTS AROUND 25 TO 30 MPH POSSIBLE.
THE BETTER MOISTURE AND DEEP LAYER FORCING MOVES ACROSS THE CWA
THURSDAY NIGHT. THUS LOOKS LIKE A GOOD CHANCE OF SEEING SOME SHOWERS
IN MOST AREAS. INSTABILITY IS ON THE LOW SIDE...BUT SHOULD SEE AT
LEAST A COUPLE HUNDRED J/KG OF ELEVATED CAPE. SO THINKING WE SEE AT
LEAST SOME EMBEDDED THUNDER. WITH THE CLOUDS AND SHOWERS
AROUND...LOWS WILL STAY A BIT WARMER THAN WEDNESDAY
NIGHT...MAINLY IN THE 50S. COULD SEE SOME LINGERING SHOWERS
ACROSS NORTHWEST IOWA FRIDAY MORNING...BUT THESE SHOULD EXIT THE
AREA BY AFTERNOON AS THE TROUGH AXIS AND DEEPER MOISTURE PUSHES
EAST. EXPECT TO SEE GRADUAL CLEARING FROM NORTH TO SOUTH DURING THE
DAY. MUCH COOLER AIR WILL BE ADVECTED IN BEHIND THE FRONT FOR
FRIDAY...AND THIS COMBINED WITH THE LINGERING CLOUD COVER...SHOULD
HOLD HIGHS IN THE MID 60S TO LOWER 70S.
AS WE HEAD INTO THE WEEKEND...OUR UPPER LEVEL LOW WILL PUSH EAST AND
DIG A DEEP TROUGH INTO THE EASTERN PART OF THE COUNTRY. MEANWHILE A
STRONG RIDGE WILL BUILD INTO THE ROCKIES. OUR AREA WILL REMAIN IN
BETWEEN THE TWO MAKING TEMPERATURES A BIT TRICKY. WE WILL TEND TO
SEE A WARMING TREND INTO EARLY NEXT WEEK...BUT HOW WARM DEPENDS ON
THE STRENGTH AND POSITION OF THE ABOVE MENTIONED FEATURES. TRENDED
HIGHS A BIT ABOVE CONSENSUS SUNDAY THROUGH TUESDAY CLOSER TO THE 0Z
ECMWF AND HPC GUIDANCE. THIS GIVES 70S ON SATURDAY...AND UPPER 70S
TO MID 80S SUNDAY THROUGH TUESDAY. THE NEW 12Z ECMWF HAS TRENDED
STRONGER WITH THE RIDGE AND THUS WARMER WITH TEMPERATURES...SO WILL
HAVE TO MONITOR MODEL TRENDS THIS PERIOD. LOWS FRIDAY AND SATURDAY
NIGHT LOOK TO BE ON THE COOL SIDE...WITH LIGHT WINDS AND CLEAR SKIES
EXPECTED. LOWERED THEM A LITTLE BELOW CONSENSUS...WITH MAINLY MID
AND UPPER 40S EXPECTED. AS THE RIDGE BUILDS CLOSER...LOWS SHOULD
WARM INTO THE 50S BY SUNDAY NIGHT. LOOKS DRY SATURDAY THROUGH
TUESDAY. PROBABLY WILL SEE OUR NEXT COLD FRONT APPROACH SOMETIME
AROUND TUESDAY...HOWEVER AT THIS TIME DOES NOT UPPER TO BE MUCH
MOISTURE WITH IT. /CHENARD
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
$$
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
328 AM CDT WED SEP 5 2012
.SHORT TERM...
TODAY AND TONIGHT...FORECAST CONFIDENCE...MEDIUM
MAIN FORECAST CONCERN IS THE APPROACHING SHORTWAVE EXITING THE
NORTHERN PLAINS AND MINNESOTA REGION BEFORE REACHING WESTERN LAKE
SUPERIOR AROUND NOON. 90 KNOT 250 MB JET MAX ROUNDING THE BASE OF
THE SHORTWAVE INCREASES TO 100 KNOTS NEAR LAKE SUPERIOR BY SUNRISE
AND TOWARDS JAMES BAY THIS AFTERNOON. STRONG UPPER DIVERGENCE MOVES
ACROSS NORTHERN WISCONSIN THIS MORNING WITH LESSER VALUES OF
DIVERGENCE ACROSS SOUTHERN WISCONSIN...THAT DIMINISHES EVEN MORE
THIS AFTERNOON.
A RATHER STRONG 700 MB WIND MAX PUSHES INTO WEST CENTRAL WISCONSIN
BY SUNRISE BEFORE LIFTING INTO NORTHEAST WISCONSIN BY NOON. THE
BEST 700 MB MOISTURE CONVERGENCE AND UPWARD MOTION FOLLOWS THIS
FEATURE.
850 MB MOISTURE REMAIN HIGH NEAR 15 CELSIUS THROUGHOUT THE DAY.
WHILE THE BEST DYNAMICS REMAIN NORTH...THE THERMODYNAMICS ARE
BETTER SOUTH WITH ALMOST 20 CELSIUS 850 MB THERMAL RIDGE INTO
SOUTHEAST WISCONSIN BY NOON. THAT DROPS TO NEAR THE ILLINOIS BORDER
BY EARLY EVENING. ZERO TO 1 KM RESULTING IN 2000 J/KG OF CAPE INTO
THE EARLY EVENING IN THE FAR SOUTHEAST AS THE SURFACE FRONT FINALLY
EXITS THE FAR SOUTHEAST.
THEREFORE EXPECT THE MINNESOTA MCS THAT HAS MERGED WITH THE
THUNDERSTORMS ON THE BACK SIDE OF THE OUTFLOW BOUNDARY FROM LAST
EVENINGS MCS TO PUSH EAST AS THE 700 MB WIND MAX MOVES THROUGH.
BEST LIFT NORTH BUT BEST INSTABILITY WELL SOUTH AS THIS MCS MOVES
OUT OF THE HIGH CAPE ENVIRONMENT. THEREFORE EXPECT THE STORMS FROM
THIS MCS TO CONTINUE TO WEAKEN AS IT MOVES ACROSS THE FORECAST AREA
EARLY THIS MORNING. RAP SOUNDINGS ARE QUITE STABLE WITH MID LEVEL
DRY AIR OVER MOST OF THE FORECAST AREA..
THEN THERE WILL BE A CHANCE FOR MORE THUNDERSTORMS THIS AFTERNOON
WITH THE COLD FRONT. HOWEVER BEST DYNAMICS ARE NORTHEAST...WITH
BEST INSTABILITY TO OUR SOUTH. NAM FORECAST SOUNDINGS DO SHOW
STEEP LAPSE RATES IN THE LOW TO MID LEVELS AGAIN THIS
AFTERNOON...ESPECIALLY SOUTHEAST WITH 10C/KM AT 900 MB TO 8 C/KM AT
500 MB. WITH PRECIPITABLE WATER VALUES AROUND 1.6 INCHES...MORE
STORMS ARE POSSIBLE...ALTHOUGH THE BEST SEVERE THREAT SHOULD BE TO
OUR SOUTH AND EAST. INTERESTING IS THE LOCAL SEVERE ENVIRONMENT
PROBABILITY CWASP OFF THE NAM HAS HIGHER VALUES THIS AFTERNOON 75
PCT THAN IT DID YESTERDAY WITH THE FIRST MCS 65 PCT.
STRONG MID LEVEL DRYING LATE TONIGHT BEHIND THE COLD FRONT.
THURSDAY...FORECAST CONFIDENCE IS HIGH.
A DRIER AND COOLER AIRMASS WILL SETTLE INTO SOUTHERN WI WITH HIGH
PRESSURE IN THE WAKE OF THE FRONT. THE MAJORITY OF MODELS AGREE THAT
THE SURFACE COLD FRONT AND 850MB BAROCLINIC ZONE WILL BE SOUTH OF
THE WI BORDER BY 12Z THU SO KEPT THU DRY. EXPECTING A PLEASANTLY
MOSTLY SUNNY DAY WITH HIGHS IN THE UPPER 70S AND LOW DEWPOINTS.
THURSDAY NIGHT THROUGH FRIDAY...FORECAST CONFIDENCE IS MEDIUM.
A LARGE UPPER TROUGH WILL SWING ACROSS THE UPPER MIDWEST AND GREAT
LAKES REGION FRIDAY AND FRIDAY NIGHT. SHOWERS COULD SPREAD INTO
SOUTHERN WI AS EARLY AS THU NIGHT WITH WEAK WARM AIR ADVECTION AND
THE NOSE OF THE UPPER JET INTO THE AREA. BY AROUND 18Z FRIDAY IT
LOOKS LIKE THE STRONGER FORCING WITH THE RIGHT ENTRANCE REGION OF
THE UPPER JET AND STRONGEST FRONTOGENESIS WILL BE MAINLY SOUTH OF
THE WISCONSIN BORDER. THE OTHER BETTER AREA OF FORCING WITH THE MAIN
UPPER TROUGH AND VORT MAX WILL BE CLOSER TO NORTHERN WISCONSIN AND
UPPER MICHIGAN. REDUCED THE POPS SLIGHTLY...BUT KEPT THE CHANCE OF
SHOWERS WORDING FOR FRIDAY. EXPECTING RAIN TO BE LIGHT AND NOT
AMOUNT TO MUCH.
OVERALL FRIDAY WILL BE CLOUDY AND COOL WITH OFF AND ON RAIN SHOWERS.
MAX TEMPS EXPECTED AROUND 70.
THE SURFACE COLD FRONT SHOULD PUSH SOUTH OF THE WI BORDER BY LATE
FRI AFTERNOON. SHOWERS COULD LINGER INTO THE EVENING UNTIL THE UPPER
TROUGH CLEARS THE AREA...BUT DRY AIR WORKING IN BEHIND THE SYSTEM
SHOULD CUT PRECIP CHANCES SIGNIFICANTLY AFTER MIDNIGHT.
.LONG TERM...
SATURDAY...FORECAST CONFIDENCE MEDIUM TO HIGH.
MUCH COOLER AIR WILL SETTLE INTO WI BEHIND THIS UPPER TROUGH AND
SURFACE COLD FRONT BY SATURDAY MORNING AND PERSIST THROUGH THE WEEKEND.
ONE MORE LOBE OF VORTICITY IS FORECAST TO SWING DOWN ACROSS WI SAT
NIGHT. ECMWF AND GFS SPIT OUT SMALL QPF AMOUNTS...BUT EXPECTING THE
ATMOSPHERE TO BE TOO DRY SO LEFT OUT POPS.
925MB TEMPS SHOULD DIP DOWN TO AROUND 12C ON SATURDAY...YIELDING MAX
TEMPS IN THE UPPER 60S WITH AMPLE SUNSHINE. THERE COULD BE A BIT OF
A NORTHWEST BREEZE DURING THE AFTERNOON.
SUNDAY THROUGH WEDNESDAY...FORECAST CONFIDENCE HIGH.
ECMWF AND GFS ARE NOW ON THE SAME TRACK WITH AN OPEN-WAVE 500MB LOW
THAT REMAINS PROGRESSIVE AND MOVES EAST OVER THE WEEKEND. A STRONG
HIGH PRESSURE RIDGE WILL BUILD BACK INTO THE UPPER MIDWEST THROUGH
THE FIRST HALF OF THE WEEK. MAX TEMPS WILL BE IN THE LOW TO MID 70S
WITH LOW DEWPOINTS. NO PRECIP EXPECTED AND THERE SHOULD BE PLENTY OF
SUNSHINE.
&&
.AVIATION/12Z TAFS/...
ONE COMPLEX OF THUNDERSTORMS HAS PUSHED EAST...BUT A SECOND AREA OF
STRONG STORMS OVER SOUTHEAST MINNESOTA WILL PUSH EAST ACROSS MUCH OF
THE FORECAST AREA BUT WEAKEN DUE TO MORE STABLE AIR OVER SOUTH
CENTRAL AND SOUTHEAST WISCONSIN.
THEN ANOTHER CHANCE OF THUNDERSTORMS WITH A COLD FRONT THAT WILL
PUSH ACROSS SOUTHERN WISCONSIN TODAY. SOME OF THESE COULD BE STRONG
LATER THIS AFTERNOON IN THE SOUTHEAST.
MAINLY VFR CIGS...BUT MVFR/IFR IN THE THUNDERSTORMS.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&
$$
TODAY/TONIGHT AND AVIATION/MARINE...HENTZ
THURSDAY THROUGH TUESDAY...MRC
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1145 PM CDT TUE SEP 4 2012
.SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT
256 PM CDT TUE SEP 4 2012
MAIN FORECAST CONCERNS ARE ON CONVECTION THROUGH WEDNESDAY MORNING
AND ASSOCIATED SEVERE WEATHER POTENTIAL.
CURRENTLY AS OF 20Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED A POTENT SHORTWAVE TROUGH OVER SOUTHERN SASKATCHEWAN INTO
EASTERN MONTANA...THEN NEAR ZONAL TO SLIGHT SOUTHWEST FLOW STREAMING
EAST INTO NEW ENGLAND. WITHIN THIS FLOW...A SHORTWAVE WAS PRESENT
OVER FAR WESTERN WISCONSIN...WITH SOME WEAK RIDGING RIGHT BEHIND IT
OVER MINNESOTA. MOSTLY SUNNY SKIES AFTER THE FOG BURNED OFF THIS
MORNING HAS ALLOWED FOR STRONG HEATING ACROSS THE AREA. WITH 12Z
RAOBS HAVING 850MB TEMPS AROUND 18C...TEMPERATURES HAVE CLIMBED INTO
THE MID TO UPPER 80S. DEWPOINTS REMAIN MUGGY FOR THIS TIME OF
YEAR...IN THE MID 60S TO AROUND 70. THE COMBINATION OF THE
TEMPERATURES AND DEWPOINTS HAS RESULTED IN MLCAPE VALUES OF
2000-3000 J/KG WITH LITTLE CIN. AT THE SURFACE...LOW PRESSURE WAS
NEAR AITKIN MN WITH A DRY-LINE ARCING THROUGH NORTHWEST WI INTO
SOUTHEAST MN. PLENTY OF CUMULUS GOING UP AHEAD OF THIS DRY LINE.
STORMS ARE EXPECTED TO DEVELOP IN THE NEXT HOUR OR TWO OUT OF THIS
CUMULUS FIELD. BIG CONCERN FOR SEVERE WEATHER IS WIND GIVEN
MID-LEVEL DRY AIR PRESENT...SEEN ON BOTH WATER VAPOR AND THE 12Z MPX
SOUNDING. TO THE WEST...FAIRLY QUIET ACROSS THE DAKOTAS AHEAD OF
THE POTENT TROUGH. HOWEVER...ANOTHER SURFACE LOW HAS DEVELOPED AHEAD
OF IT NEAR PIERRE. IN ADDITION... GOES PRECIPITABLE WATER IMAGERY
SHOWS MOISTURE BEGINNING TO SURGE TO THE NORTHWEST THROUGH EASTERN
NEBRASKA AHEAD OF THE SURFACE LOW/UPPER TROUGH.
REST OF THE AFTERNOON...ASSUMING CONVECTION FIRES IN THE CUMULUS
FIELD...WHICH IS INDICATED BY MANY MESO-MODELS...EXPECTING IT TO
PROPAGATE EAST-SOUTHEAST QUICKLY DURING THE NEXT FEW HOURS. THIS IS
DUE TO THE DRY MID LEVEL AIR ALLOWING FOR RAPID MOVING OUTFLOW AS
WELL AS THE MAIN SHORTWAVE ACCOMPANYING IT SHIFTING INTO EASTERN
WISCONSIN BY 00Z. THEREFORE...THINKING THE SEVERE THREAT AND
PROBABLY MUCH OF THE PRECIPITATION WILL END BY 00Z. ONLY CAVEAT
COULD BE IN FAR SOUTHWEST WI AND FAR NORTHEAST IA WHERE THERE ARE
HINTS THE TAIL END OF CONVECTION COULD STALL OUT. KEPT SOME HIGHER
CHANCES OF PRECIPITATION DOWN THERE JUST IN CASE.
TONIGHT AND WEDNESDAY...THE POTENT SHORTWAVE OVER EASTERN MONTANA IS
FORECAST TO MOVE INTO WESTERN MINNESOTA BY 12Z WEDNESDAY. AS THIS
OCCURS...THE MOISTURE SEEN LIFTING UP THROUGH EASTERN NEBRASKA RIGHT
NOW IS GOING TO GET ISENTROPICALLY LIFTED UP TOWARDS US. SO AFTER
SOME BRIEF SHORTWAVE RIDGING AND SUBSIDENCE THIS EVENING...ANOTHER
ROUND OF SHOWERS AND THUNDERSTORMS LOOKS LIKELY. DEVELOPMENT MAY
OCCUR SOUTH OF I-90 AS EARLY AS 03Z AS SUGGESTED BY THE 04.12Z
NAM/GFS. BETTER POTENTIAL FOR PRECIPITATION FOR THE ENTIRE AREA IS
AFTER MIDNIGHT AS THE SHORTWAVE APPROACHES AND 850MB MOISTURE
TRANSPORT REALLY INCREASES. MID-LEVEL FLOW IS NICELY DIFFLUENT TOO
AHEAD OF THE WAVE...AIDING IN FORCING. MCS DEVELOPMENT IS CERTAINLY
POSSIBLE...AS NOTED BY THE 04.12Z ECMWF/UKMET/CANADIAN/NAM.
REGARDING SEVERE CONCERN...1-6KM SHEAR VALUES VARY FROM MODEL TO
MODEL. NAM IS ON THE ORDER OF 30-40 KT WHILE THE GFS IS 20-30KT. THE
NAM WOULD DEFINITELY GIVE A SEVERE WEATHER CONCERN...WITH BOTH HAIL
AND DAMAGING WINDS POSSIBLE. THE GFS NOT AS MUCH SO. THEREFORE...
THINK THE SPCS DAY 1 OUTLOOK SLIGHT RISK IDEA IS APPROPRIATE. A BIG
NOTE...THERE IS A POSSIBILITY MCS DEVELOPMENT COULD OCCUR FARTHER
SOUTH SAY MORE OVER IOWA. IF IT DOES...CORFIDI VECTORS WOULD TAKE IT
SOUTHEAST...LIMITING SOME OF THE CONVECTIVE ACTIVITY OVER THE
FORECAST AREA. SHORTWAVE TROUGH IS PROGGED TO HEAD EAST TO CENTRAL
UPPER MICHIGAN AND LAKE MICHIGAN BY 18Z...ALLOWING STRONG ISENTROPIC
DESCENT TO FILTER INTO THE AREA AND CLEAR OUT THE
PRECIPITATION/CLOUDS. COLD FRONTAL BOUNDARY TOO LOOKS TO BE THROUGH
THE AREA AROUND 18Z. 850MB TEMPS FALL QUITE A BIT WITH THE PASSAGE
OF THE TROUGH. THROUGH 12Z WEDNESDAY...THEY HOVER BETWEEN 18-20C. BY
00Z THURSDAY...THOUGH... THEY FALL TO 12-14C. THUS...ANTICIPATE A
COOLER DAY TOMORROW...MORE AROUND SEASONABLE NORMALS.
WEDNESDAY NIGHT AND THURSDAY...TROUGHING OVER THE FORECAST AREA AS A
RESULT OF THAT POTENT SHORTWAVE MOVING THROUGH WEDNESDAY LOOKS TO BE
SHORT-LIVED. THAT IS BECAUSE ANOTHER POTENT TROUGH IS PROGGED TO
DROP SOUTH INTO MONTANA BY 12Z THURSDAY. THERE WILL BE ENOUGH
SUBSIDENCE AND DRY AIR PERSISTING IN THE WAKE OF WEDNESDAYS
SHORTWAVE SUCH THAT WEDNESDAY NIGHT STAYS DRY. AT THE SURFACE...A
HIGH PRESSURE RIDGE IS PROGGED TO BUILD INTO WESTERN PORTIONS OF THE
FORECAST AREA BY 12Z THURSDAY. GIVEN THE RIDGE POSITION...ENOUGH OF
A NORTHWESTERLY BREEZE SHOULD OCCUR TO PREVENT ANY FOG AT LEAST IN
THE MISSISSIPPI RIVER VALLEY. OTHER SMALLER VALLEYS LIKE THE
WISCONSIN MAY STILL BE SUSCEPTIBLE...THOUGH. COOLER NIGHT LIKELY
WITH WINDS LIGHTENING UP THROUGH THE NIGHT AS WELL AS CLEAR SKIES.
SOME OF THE TYPICAL COLD SPOTS COULD FALL INTO THE MID 40S. ON
THURSDAY...THAT POTENT TROUGH DIGS DOWN A LITTLE MORE THROUGH
MONTANA...SETTING UP WEST-SOUTHWEST MID LEVEL FLOW OVER THE AREA.
WITHIN THIS FLOW...THERE COULD BE A SHORTWAVE SKIMMING ACROSS
NORTHERN WISCONSIN IN THE AFTERNOON...BUT OTHERWISE MODELS DO NOT
SHOW ANY OTHER SHORTWAVES OF SIGNIFICANCE. HOWEVER..WITH THAT POTENT
TROUGH DIGGING A LITTLE MORE...IT SETS UP A 310-315K ISENTROPIC
LIFT/MID-LEVEL FRONTOGENESIS ZONE DOWNSTREAM ACROSS THE NORTHERN
PLAINS INTO OUR REGION. LOOKS LIKE ANY PRECIPITATION RESULTING FROM
THIS FORCING WILL STAY WEST OF OUR AREA...BUT AN INCREASE IN
MID/HIGH CLOUDS IS LIKELY...ESPECIALLY IN THE AFTERNOON. 850MB TEMPS
OF 12-14C COMBINED WITH A DECENT AMOUNT OF SUN AND THE DRY AIR
SHOULD ALLOW FOR TEMPERATURES TO CLIMB INTO THE MID TO UPPER 70S.
THURSDAY NIGHT AND FRIDAY...THE POTENT TROUGH OVER MONTANA IS
FORECAST TO DIG SOUTHEAST DURING THIS PERIOD...BEING PUSHED BY
RIDGING DROPPING DOWN INTO SOUTH CENTRAL CANADA. BY 00Z SATURDAY...A
LONG WAVE TROUGH SHOULD EXTEND FROM NORTHEAST ONTARIO...INTO THE
FORECAST AREA AND INTO NEBRASKA. THE MAIN ISSUE WITH THIS POTENT
TROUGH COMING TOWARDS THE AREA IS WHERE DOES THE FRONTOGENESIS ZONE
AHEAD OF IT LAY UP...AND THUS THE ASSOCIATED PRECIPITATION. THE
04.00Z ECMWF KEPT THE BULK OF IT ACROSS IOWA THURSDAY NIGHT AND INTO
ILLINOIS AND MISSOURI ON FRIDAY...THUS FOR THE MOST PART OUR
FORECAST AREA ENDS UP DRY. THE 04.12Z NAM IS FARTHER NORTH...HAVING
PRECIPITATION FALL SOUTH OF INTERSTATE 94 AFTER MIDNIGHT THURSDAY
NIGHT AND FRIDAY. 04.12Z GFS IS A LITTLE MORE INTERESTING. THE MODEL
SUGGESTS SOME HIGHER LEVEL FRONTOGENESIS PRODUCING A BAND OF MOSTLY
LIGHT RAIN...WHICH SLOWLY DROPS SOUTH THROUGH THE AREA AFTER
MIDNIGHT THURSDAY NIGHT THROUGH FRIDAY. THESE BANDS SOMETIMES VERIFY
AND OTHER TIMES NOT. OVERALL...THE BULK OF THE PRECIPITATION IN THE
GFS FALLS TO THE SOUTH. IN ANY EVENT...ALL MODELS SUGGEST A NEED TO
INCREASE PRECIPITATION CHANCES UP TO 40 FOR NOW...MAINLY SOUTH OF
I-90. FURTHER REFINEMENTS WILL BE NEEDED AS WE GET CLOSER TO THIS
PERIOD. WITH MORE CLOUDS AS WELL AS COOLER AIR COMING IN WITH THE
UPPER TROUGH...ANTICIPATE THIS PERIOD TO BE MUCH COOLER THAN AS OF
LATE. THIS WILL BE ESPECIALLY TRUE ON FRIDAY AS 850MB TEMPS FALL TO
6-9C. HIGHS ON FRIDAY MAY GET STUCK IN THE 60S...ESPECIALLY IF IT
RAINS ALL DAY LIKE THE NAM.
.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY
256 PM CDT TUE SEP 4 2012
04.12Z ECMWF/GFS/CANADIAN AND GFS ENSEMBLES ARE A LITTLE DIFFERENT
AMONGST EACH OTHER TODAY COMPARED TO YESTERDAY...MOSTLY WITH REGARDS
TO HANDLING WHETHER THE UPPER TROUGH COMING THROUGH THE FORECAST
AREA FRIDAY ENDS UP CLOSING OFF IN THE OHIO RIVER VALLEY.
INTERESTINGLY...THE 04.12Z ECMWF/CANADIAN AND GFS HAVE NOW
FLIP-FLOPPED WITH EACH OTHER...WITH THE ECMWF/CANADIAN NOW MORE
PROGRESSIVE AND THE GFS CLOSING OFF. FOR OUR AREA...THOUGH...WHICH
EVER SOLUTION PANS OUT REALLY DOESNT MATTER...AS BOTH SCENARIOS
BUILD HIGH PRESSURE INTO THE FORECAST AREA FOR THE WEEKEND. SO MAYBE
AFTER A FEW LINGERING SHOWERS IN NORTHEAST IA/SOUTHWEST WI FRIDAY
NIGHT...EXPECT DECREASING CLOUDS AND DRY WEATHER FOR THE WEEKEND.
CERTAINLY LOOKS COOL COMPARED TO WHAT HAS BEEN SEEN RECENTLY...
THANKS TO 850MB TEMPS OF 6-8C ON SATURDAY AND 10-12C ON SUNDAY.
WOULD NOT BE SURPRISED IF SOME OF THE TYPICAL COLD SPOTS END UP
SEEING SOME UPPER 30S.
FOR EARLY NEXT WEEK...UPPER RIDGING OVER THE WESTERN U.S. IS
FORECAST TO BUILD UP INTO THE FORECAST AREA...BUT FLATTEN PRETTY
QUICKLY BY TUESDAY AS A SHORTWAVE TROUGH CROSSING SOUTHERN CANADA.
WILL SEE A WARM UP WITH THE RIDGING COMING IN...AT LEAST BACK TO
NORMAL. DRY CONDITIONS SHOULD CONTINUE AS WELL WITH THE HIGH
PRESSURE OVER THE WEEKEND BLOCKING GULF OF MEXICO MOISTURE RETURN.
&&
.AVIATION...
1145 PM CDT TUE SEP 4 2012
ANOTHER ROUND OF THUNDERSTORMS WILL IMPACT THE AREA AS AN
ORGANIZED MCS DRIVES ACROSS THE REGION BETWEEN 05-09Z. STRONG WINDS
WILL ACCOMPANY THE STORMS INITIALLY...LIKELY IMPACTING KRST BETWEEN
0530-07Z AND 07-08Z AT KLSE. THE STRONGEST WINDS COULD BE ON A
WEAKENING TREND AS THE STORMS REACH KLSE...HOWEVER.
SHRA/TS COULD LINGER THROUGH WED MORNING...BUT THE BULK OF THIS
ACTIVITY SHOULD HAVE EXITED EAST BY 18Z AS A COLD FRONT SWEEPS
ACROSS THE UPPER MISSISSIPPI RIVER VALLEY. TIMING IS ROUGHLY 16Z AT
KRST AND 18Z AT KLSE.
CLEARING FOR WED NIGHT...AND CONSIDERING THE RAINFALL...SOME
INGREDIENTS FOR FOG. AS OF NOW...THINK LOW LEVEL WINDS WILL BE
STIRRING TOO MUCH...THUS INHIBITING THE FOG. OF COURSE THIS WILL BE
RE-EVALUATED FOR LATER TAF ISSUANCES.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
256 PM CDT TUE SEP 4 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM....AJ
AVIATION.....RIECK
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
351 AM PDT WED SEP 5 2012
.SYNOPSIS...
TWO SOURCES OF MONSOON MOISTURE WILL MOVE ACROSS SOUTHWEST
CALIFORNIA THROUGH THURSDAY. ONE IS COMING FROM THE SOUTHWEST...AND
WILL BRING ABUNDANT CLOUDS AND INTERMITTENT LIGHT RAIN SHOWERS THIS
MORNING. THE OTHER IS COMING FROM THE SOUTHEAST. THIS SHOULD LEAD TO
AFTERNOON AND EVENING THUNDERSTORMS OVER THE MOUNTAINS AND DESERTS
WITH LOCALLY HEAVY RAINS. A HIGH PRESSURE RIDGE WILL BUILD WESTWARD
ACROSS THE AREA ON FRIDAY...TEMPORARILY BRINGING A DRYING TREND.
ANOTHER SURGE OF MONSOON MOISTURE IS POSSIBLE OVER THIS COMING
WEEKEND.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
.THIS MORNING THROUGH EARLY AFTERNOON...
EMBEDDED SHORT WAVE IN THE MID/HIGH LEVEL MONSOON MOISTURE STREAM
COMING IN FROM THE SOUTHWEST IS CAUSING 40-45 DBZ RADAR ECHOES OVER
THE SOUTHERN CALIFORNIA BIGHT. USING LAST NIGHT AS AN ANALOG WHEN
SIMILAR STRENGTH ECHOES MOVED ACROSS SANTA BARBARA/VENTURA/LOS
ANGELES/KERN COUNTIES...THEN SHOULD ONLY SEE LIGHT INTERMITTENT RAIN
WEST OF THE MOUNTAINS THIS MORNING. THE HRRR MODEL COMPOSITE
REFLECTIVITY MATCHES HAS BEEN DOING VERY WELL WITH THE POSITION AND
OBSERVED STRENGTH OF THE RADAR ECHOES. USING THIS MODEL ALSO YIELDS
LIGHT RAINFALL...STARTING AROUND 0700 PDT FOR THE ORANGE COUNTY
COAST...SPREADING INLAND BY 1100 PDT TO INLAND EMPIRE AND NORTH SAN
DIEGO COUNTY. FOR THE EARLY AFTERNOON...SUBSIDENCE FOLLOWING THE
SHORT WAVE SHOULD RESULT IN LESS MID/HIGH LEVEL CLOUDS AND END
SHOWER ACTIVITY WEST OF MOUNTAINS.
OVER MOUNTAINS AND DESERTS...WETTER MID/LOW LEVELS DUE TO MONSOON
MOISTURE STREAM FROM THE SOUTHEAST SHOULD YIELD MEASURABLE RAINFALL
AMOUNTS THIS MORNING...BUT THUNDERSTORM DEVELOPMENT WILL LIKELY
BE DELAYED UNTIL MID AFTERNOON DUE TO EXTENSIVE CLOUD COVER THIS
MORNING.
.MID AFTERNOON THROUGH EARLY EVENING...
MOUNTAINS AND DESERTS HAVE A SLIGHTLY GREATER RISK OF FLASH FLOODING
TODAY...ASSUMING ENOUGH CLEARING TAKES PLACE TO ALLOW DEVELOPMENT OF
CONVERGING DIURNAL WINDS AND RESULTANT LIFTING. THE PRECIPITABLE
WATER VALUES RANGE FROM 1.25 TO ALMOST 2 INCHES. THE STEERING WINDS
WILL INITIALLY BE FROM THE SOUTH AND THEN SHIFT TO SOUTHWEST. THIS
WOULD CARRY THE THUNDERSTORMS DOWN THE DESERT SLOPES...ADDING
ADDITIONAL RAINFALL TO THE LOWER END OF DRAINAGE BASINS AT THE SAME
TIME THAT RUNOFF IS COMING DOWN FROM THE HEADWATERS. NO FLASH FLOOD
WATCH AT THIS TIME BUT STAY TUNED FOR UPDATE LATE THIS MORNING.
.TONIGHT THROUGH THURSDAY...
PRETTY MUCH FORECASTING PERSISTENCE...ALTHOUGH WITHOUT THE THREAT OF
MORNING RAIN WEST OF THE MOUNTAINS. AS NOTED IN PREVIOUS FORECAST
DISCUSSION...AMPLE MID-LEVEL MOISTURE REMAINS THROUGH THURSDAY WITH
PRECIPITABLE WATER VALUES GREATER THE 1.5 INCHES...TRANSPORT WINDS
ARE LIGHT SOUTHWESTERLY SO THUNDERSTORMS THAT DO FORM THURSDAY
AFTERNOON COULD STILL PRODUCE LOCALLY HEAVY DOWNPOURS.
FRIDAY/SATURDAY...
FORECASTING LESS THUNDERSTORM ACTIVITY AND SLIGHT INCREASE IN LATE
NIGHT/EARLY MORNING LOW CLOUDS WEST OF MOUNTAINS DUE TO HIGH
PRESSURE RIDGE BUILDING ALOFT AND CLOSING DOOR ON MONSOON MOISTURE.
HOWEVER ENOUGH RESIDUAL MID LEVEL MOISTURE AND DAYTIME HEATING FOR
ISOLATED THUNDERSTORM DEVELOPMENT.
SUNDAY/MONDAY...
MONSOON DOOR REOPENS FOR ANOTHER SURGE AS AN EASTERLY WAVE/UPPER LOW
TRACKS AROUND THE SW QUADRANT OF THE HIGH CELL AND MOVES ACROSS
NORTHERN BAJA CALIFORNIA/SOUTHWEST CALIFORNIA. HAVE ADDED SOME
POPS...AROUND 20 PERCENT...AND MENTION OF THUNDERSTORMS FOR
MOUNTAINS AND DESERTS ON THESE DAYS.
TUESDAY...
GOING WITH THE TROUGH IN THE WESTERLIES FINALLY MOVING CLOSE ENOUGH
TO BRING DRIER AIR IN FROM THE WEST. LOOK FOR MOSTLY SUNNY/CLEAR
SKIES OVER MOUNTAINS AND DESERTS WITH SLIGHT COOLING...AND MORE
NIGHT/MORNING CLOUDS FOR COASTS AND WESTERN VALLEYS.
&&
.AVIATION...
050930Z...PATCHY STRATUS...WITH BASES AROUND 800 FT MSL AND TOPS
NEAR 1100 FT MSL...IS HAVING DIFFICULTY DEVELOPING AND MAY STEER
CLEAR OF COASTAL AERODROMES THIS MORNING. VERY LIGHT SHOWERS ARE
CURRENTLY OVER THE PACIFIC...MOVING TOWARD THE COAST THIS MORNING.
PRECIPITATION FALLING FROM THESE SHOWERS WILL MOST LIKELY ONLY
CREATE A TRACE AT THE SURFACE. ISOLATED TO SCATTERED SHOWERS AND
TSTMS ARE EXPECTED THIS AFTERNOON AND EVENING OVER THE MTNS AND
DESERTS...WITH BASES AROUND 8K FT MSL AND TOPS AROUND 40K FT MSL.
OTHERWISE...VFR CONDS WITH SCT/BKN CLOUDS AOA 10K FT AND
UNRESTRICTED VIS THROUGH THU MORNING.
&&
.FIRE WEATHER...
A POCKET OF VERY DRY AIR REMAINS OVER THE FOOTHILLS AND LOWER
COASTAL SLOPES AT ELEVATIONS BETWEEN 1000 FEET AND 3500 FEET MSL.
RELATIVE HUMIDITY IN THIS LAYER HAS BEEN IN THE SINGLE DIGITS WITH
LITTLE TO NO RECOVERY OVERNIGHT FOR AT LEAST THE PAST 6 DAYS. THIS
DRY AIR MAY FINALLY BE MODIFIED TODAY IF THE INTERMITTENT LIGHT
RAIN SHOWERS DO OCCUR AS FORECAST. ELSEWHERE RELATIVE HUMIDITY
SHOULD BE HIGH ENOUGH TO RETARD FIRE GROWTH FROM ANY LIGHTNING
OUTSIDE OF WETTING RAIN AREAS...AND INITIAL ATTACK FORCES MAY BE
NEED TO ASSIST WITH OTHER HAZARDS ASSOCIATED WITH
THUNDERSTORMS...SUCH AS FLASH FLOODING.
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE AT THIS TIME.
PZ...NONE.
&&
$$
PUBLIC/FIRE WEATHER...BALFOUR
AVIATION/MARINE...JJT
AREA FORECAST DISCUSSION
NWS RALEIGH NC
744 AM EDT WED SEP 5 2012
.SYNOPSIS...
A MOIST AIRMASS WILL PERSIST OVER THE AREA THROUGH THURSDAY IN
ASSOCIATION WITH A STALLED SURFACE TROUGH OVER THE CAROLINAS. A
BRIEF DRY PERIOD IS EXPECTED ON FRIDAY...FOLLOWED BY A RETURN TO
UNSETTLED WEATHER OVER THE WEEKEND AS AN UNSEASONABLY DEEP UPPER
LEVEL TROUGH APPROACHES FROM THE WEST.
&&
.NEAR TERM /TODAY AND TONIGHT/...
AS OF 245 AM WEDNESDAY...
PRECIPITATION CHANCES:
AN H5 DISTURBANCE WAS NOTED IN WV IMAGERY AND RAP/MESOANALYSIS DATA
OVER THE WESTERN PIEDMONT AT 06Z THIS MORNING. THE DISTURBANCE IS
EXPECTED TO PROGRESSES SLOWLY EAST TO THE HWY 1 CORRIDOR BY 15-18Z
AND THE COASTAL PLAIN BY 18-21Z. THE LATEST RAP GUIDANCE INDICATES
THIS FEATURE WILL BECOME INCREASINGLY SHEARED/DEAMPLIFIED BY THE
AFTERNOON HOURS...AND IT IS DIFFICULT TO ASCERTAIN WHAT (IF ANY)
CONTRIBUTION TO ASCENT MAY BE ASSOCIATED WITH IT. LIGHT MID-LEVEL
FLOW WILL BE PRESENT OVER THE CAROLINAS TODAY...SOUTH OF THE PRIMARY
BELT OF WESTERLIES WHERE A WEAKNESS HAS DEVELOPED IN H5 RIDGE
EXTENDING WEST-EAST ACROSS THE SOUTHERN 1/3 OF THE CONUS...AND IT
WILL BE DIFFICULT FOR ANY ADDITIONAL MID/UPPER LEVEL DISTURBANCES TO
TRACK INTO THE AREA THROUGH TONIGHT. LOWER-LEVEL FORCING WILL BE
CONFINED TO CONVERGENCE ASSOC/W A WEAKENING SFC-H85 TROUGH OVER
WESTERN PORTIONS OF THE STATE TODAY...WITH THE BEST LOW-LEVEL
CONVERGENCE SHIFTING EAST INTO PORTIONS OF THE NW/NORTHERN PIEDMONT
OVERNIGHT. RELATIVELY SPEEDY (20-30 KT) SW LOW-LEVEL FLOW WILL BE
PRESENT ON THE EASTERN PERIPHERY OF THE TROUGH OVER CENTRAL NC. WEAK
MID-LEVEL LAPSE RATES AND BROKEN CLOUD COVER WILL LIMIT DIURNAL
DESTABILIZATION IN THE WEST TODAY...WITH MLCAPE VALUES OF ~1000 J/KG
OR LESS. ALTHOUGH STRONGER INSOLATION MAY BE PRESENT IN EASTERN
PORTIONS...WEAK MID-LEVEL LAPSE RATES COUPLED WITH A RELATIVELY
DRIER BOUNDARY LAYER SHOULD LIMIT MLCAPE VALUES TO 1000-1500
J/KG...THOUGH UP TO 2000 J/KG WILL BE POSSIBLE IF BOUNDARY LAYER
MOISTURE IS GREATER THAN PROGGED. ABOVE NORMAL MOISTURE WILL BE
PRESENT THROUGHOUT THE COLUMN TODAY/TONIGHT...WITH PWAT VALUES
PROGGED NEAR 2.00" EVERYWHERE.
THE LATEST 00Z CONVECTION ALLOWING MODELS (CAMS) INDICATE CONVECTION
DEVELOPING ON THE EASTERN PERIPHERY OF THE WEAKENING H5 DISTURBANCE
IN VICINITY OF THE HWY 1 CORRIDOR BETWEEN 12-18Z TODAY...SHIFTING
EAST INTO THE COASTAL PLAIN BY MID/LATE AFTERNOON. THE CAMS ALSO
INDICATE CONVECTION DEVELOPING IN VICINITY OF THE SFC-H85 TROUGH
OVER THE FOOTHILLS/MOUNTAINS THIS AFTERNOON...SHIFTING INTO PORTIONS
OF THE NW/NORTHERN PIEDMONT OVERNIGHT IN ASSOCIATION WITH WEAK
LOW-LEVEL CONVERGENCE IN THE PRESENCE OF A VERY MOIST AND MARGINALLY
UNSTABLE AIRMASS. WILL BASE PRECIP CHANCES THROUGH TONIGHT ON THE
AFOREMENTIONED REASONING...HOWEVER...CONFIDENCE IN THE TIMING/
COVERAGE OF CONVECTION REMAINS RELATIVELY LOW GIVEN THE PRESENCE OF
WEAK STEERING FLOW.
TEMPERATURES:
WITH RELATIVELY LITTLE CHANGE IN AIRMASS...HIGHS TODAY WILL BE
SIMILAR TO PREVIOUS DAYS...DEPENDING PRIMARILY ON CLOUD COVER AND
CONVECTION. WILL INDICATE HIGHS RANGING FROM THE LOWER/MID 80S WEST
TO MID/UPPER 80S EAST. LOWS TONIGHT WILL ALSO BE BASED ON
PERSISTENCE...IN THE LOWER 70S.
HAZARDOUS WEATHER:
VERY WEAK DEEP-LAYER SHEAR WILL BE UNSUPPORTIVE OF CONVECTIVE
ORGANIZATION TODAY. GIVEN AN INCREASINGLY DEAMPLIFIED PATTERN OVER
THE CAROLINAS...A THERMODYNAMIC ENVIRONMENT CHARACTERIZED BY LOW
DCAPE AND WEAK MID-LEVEL LAPSE RATES...THE THREAT FOR AN ISOLD
SEVERE STORM WILL BE VERY LOW...THOUGH NON-ZERO (AS LONG AS DEEP
CONVECTION IS PRESENT) GIVEN ENHANCED (~25 KT) LOW-LEVEL FLOW AND A
VERY MOIST COLUMN SUPPORTIVE OF PRECIP LOADING. LOCALLY HEAVY
RAINFALL AND ISOLD FLOODING CANNOT BE RULED OUT IN URBAN AREAS...
THOUGH THE THREAT APPEARS LOWER THAN PREVIOUS DAYS. -VINCENT
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 230 AM WEDNESDAY...
THERE IS A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS AGAIN THURSDAY
AFTERNOON AND EVENING AS A WEAKENING COLD FRONT IS FORECAST TO STALL
ACROSS CENTRAL NORTH CAROLINA THURSDAY. THE UPPER DYNAMICS WILL BE
VERY WEAK. HOWEVER... CONTINUED HI PW`S AND STRONG HEATING
ESPECIALLY IN THE SOUTH AND EAST WILL SUPPORT SCATTERED STRONG
THUNDERSTORMS... WITH THE PRIMARY THREATS OF LOCALLY HEAVY RAIN AND
GUSTY WIND. WE WILL CARRY THE HIGHEST POP IN THE EAST AND SOUTH...
BUT EVEN THE NW WILL HAVE LOW CHANCE POPS. HIGHS IN THE MID TO UPPER
80S NW RANGING TO AROUND 90 SE. THE POPS WILL BECOME SLIGHT CHANCE
BY LATE EVENING THURSDAY... SUPPORTED BY THE LINGERING NEARLY
STATIONARY BOUNDARY. LOWS GENERALLY 70-73.
FRIDAY AND FRIDAY NIGHT... THIS MAY BE THE DAY WHEN WE HAVE THE
LOWEST POPS... ESPECIALLY OVER THE PIEDMONT WHERE SOME DRIER AIR
(VERY SLIGHTLY DRIER AIR MAY FILTER IN WITH DEW POINTS IN THE MID
60S). THAT IS... IF... THE LOW LEVEL BOUNDARY DRIFTS INTO THE
COASTAL PLAIN OR WASHES OUT ENTIRELY PER SOME MODEL SOLUTIONS. THIS
APPEARS POSSIBLE... YET BY LATE IN THE DAY EXPECT THE SEA BREEZE/OLD
FRONT COMBO TO DRIFT BACK WNW INTO THE EASTERN PIEDMONT BY EARLY
EVENING BRINGING BACK 70+ DEW POINTS. WE WILL STILL CARRY SLIGHT TO
LOW CHANCE POP FOR SHOWERS AND THUNDERSTORMS... MAINLY FROM FAY AND
RDU EASTWARD DURING FRIDAY AFTERNOON AND EARLY EVENING. OTHERWISE...
PARTLY SUNNY WARM AND HUMID. HIGHS 88-94 NW TO SANDHILLS.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 245 AM WEDNESDAY...
BIG PATTERN CHANGE IN THE OFFING...
A FAIRLY DEEP MID-UPPER LEVEL TROUGH IS FORECAST TO DEVELOP OVER THE
GREAT LAKES AND SWING EASTWARD OVER THE WEEKEND. THE ACTUAL COLD
FRONT IS PROJECTED FOR SATURDAY. THIS WILL SWEEP THE VERY MUGGY
OPPRESSIVE AIR MASS CURRENTLY OVER THE AREA OUT TO SEA SUNDAY AND
MONDAY. THE MODELS HAVE BEEN TRENDING TOWARD A MORE PROGRESSIVE
TROUGH PASSAGE FOR OUR REGION AND LATITUDE. THIS WOULD MEAN LESS IN
THE WAY OF SEVERE AND FLOODING POTENTIAL OVER THE WEEKEND. STAY
TUNED.
WE WILL CONTINUE TO CARRY INCREASING CHANCES OF SHOWERS AND STORMS
SAT-SAT NIGHT... SHIFTING EAST MORE QUICKLY SUNDAY. MODELS NOW
PROJECT THE ACTUAL FRONT TO PUSH EAST THROUGH OUR REGION BY LATE
SATURDAY. THIS WOULD MEAN LOWERING HUMIDITIES AND MUCH LOWER POP FOR
SUNDAY (A DAY TO A DAY AND A HALF EARLIER THAN PROJECTED 24 HOURS
AGO). WE WILL TREND THAT WAY... BUT KEEP A CHANCE POP MAINLY EAST
SUNDAY.
TURNING COOLER AND MUCH DRIER MONDAY AND TUESDAY. LOWS 55-60. HIGHS
77-82.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
AS OF 730 AM WEDNESDAY...
24-HR TAF PERIOD:
IFR CEILINGS THIS MORNING ARE EXPECTED TO LIFT TO MVFR AND
EVENTUALLY SCATTER OUT TO VFR AT MOST LOCATIONS BY 15Z. MVFR
CEILINGS COULD PERSIST INTO THE AFTERNOON AT THE INT/GSO TERMINALS
WHERE SHOWER ACTIVITY WILL BE MORE LIKELY AS THE DAY PROGRESSES.
EXPECT THE BEST CHANCE OF CONVECTION AT THE INT/GSO TERMINALS
BETWEEN 15Z THIS MORNING AND 03Z THIS EVENING...WHERE VCSH WILL BE
MENTIONED. AT THE RDU/FAY/RWI TERMINALS...CONFIDENCE IN AFTERNOON
CONVECTION IS LOWER THAN AT INT/GSO. AS A RESULT...WILL KEEP VFR
CONDITIONS IN PLACE AT RDU/FAY/RWI ONCE MORNING FOG AND STRATUS HAS
LIFTED AND SCATTERED OUT. OTHERWISE...ANTICIPATE A CHANCE FOR
SUB-VFR CEILINGS/VISBYS ONCE AGAIN BY THE END OF THE TAF
PERIOD...06-12Z THURSDAY MORNING.
LOOKING AHEAD:
SUB-VFR STRATUS OR FOG WILL BE POSSIBLE DURING THE EARLY MORNING
HOURS (07-13Z) ON BOTH FRI/SAT...ALONG WITH ISOLD SHOWERS AND STORMS
DURING THE AFTERNOON AND EARLY EVENING HOURS...PRIMARILY AT THE
FAY/RWI TAF SITES. MORE WIDESPREAD SHOWERS/STORMS WILL BE POSSIBLE
SATURDAY NIGHT/SUNDAY AS AN UNSEASONABLY DEEP UPPER LEVEL TROUGH
APPROACHES FROM THE WEST. -VINCENT
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...VINCENT
NEAR TERM....VINCENT
SHORT TERM...BADGETT
LONG TERM...BADGETT
AVIATION...VINCENT
AREA FORECAST DISCUSSION...UPDATED
NWS MILWAUKEE/SULLIVAN WI
957 AM CDT WED SEP 5 2012
.UPDATE...CLEARING CONTINUES TO PROGRESS WEST TO EAST ACROSS
SOUTHERN WISCONSIN THIS MORNING. WITH THE COLD FRONT REMAINING TO
THE WEST...THE SUN SHOULD PUSHING TEMPERATURES INTO THE 80S FOR
AFTERNOON HIGHS. BIG QUESTION IS WHEN THUNDERSTORMS REDEVELOP
AHEAD OF THE FRONT. GIVEN THE EXPECTED TIMING OF THE FRONT...THE
BEST CHANCE FOR MORE STORMS WILL BE ACROSS THE SOUTHEAST FORECAST
AREA...MAINLY SOUTHEAST OF A LINE FROM DARLINGTON TO SHEBOYGAN.
MODELS SOUNDINGS STILL SHOWING PLENTY OF CAPE AND SHEAR THIS
AFTERNOON...SO SEVERE STORMS CERTAINLY POSSIBLE IF THINGS GET
GOING BEFORE THE FRONT GETS THROUGH THE FORECAST AREA.
&&
.AVIATION/18Z TAFS/...WILL CONTINUE TO SEE CLEARING SKIES THROUGH
THIS MORNING. ATTENTION THEN TURNS TO POSSIBLE REDEVELOPMENT OF
STORMS AHEAD OF AN APPROACHING COLD FRONT. THINK BEST CHANCE OF
STORMS THIS AFTERNOON WILL BE ALONG AND SOUTHEAST OF A LINE FROM
DARLINGTON TO SHEBOYGAN. STRONG TO SEVERE STORMS ONCE AGAIN
POSSIBLE...ESPECIALLY FARTHER TO THE SOUTHEAST. LOWER VSBYS LIKELY
WITHIN MODERATE TO HEAVY RAINFALL...OTHERWISE VFR CONDITIONS WILL
PREVAIL THROUGH THE DAY.
IF SKIES CLEAR UP AND WINDS ARE LIGHT ENOUGH...COULD SEE SOME
PATCHY FOG DEVELOP TONIGHT. QUIET WEATHER THEN EXPECTED THURSDAY
UNDER HIGH PRESSURE.
&&
.PREV DISCUSSION... /ISSUED 328 AM CDT WED SEP 5 2012/
SHORT TERM...
TODAY AND TONIGHT...FORECAST CONFIDENCE...MEDIUM
MAIN FORECAST CONCERN IS THE APPROACHING SHORTWAVE EXITING THE
NORTHERN PLAINS AND MINNESOTA REGION BEFORE REACHING WESTERN LAKE
SUPERIOR AROUND NOON. 90 KNOT 250 MB JET MAX ROUNDING THE BASE OF
THE SHORTWAVE INCREASES TO 100 KNOTS NEAR LAKE SUPERIOR BY SUNRISE
AND TOWARDS JAMES BAY THIS AFTERNOON. STRONG UPPER DIVERGENCE MOVES
ACROSS NORTHERN WISCONSIN THIS MORNING WITH LESSER VALUES OF
DIVERGENCE ACROSS SOUTHERN WISCONSIN...THAT DIMINISHES EVEN MORE
THIS AFTERNOON.
A RATHER STRONG 700 MB WIND MAX PUSHES INTO WEST CENTRAL WISCONSIN
BY SUNRISE BEFORE LIFTING INTO NORTHEAST WISCONSIN BY NOON. THE
BEST 700 MB MOISTURE CONVERGENCE AND UPWARD MOTION FOLLOWS THIS
FEATURE.
850 MB MOISTURE REMAIN HIGH NEAR 15 CELSIUS THROUGHOUT THE DAY.
WHILE THE BEST DYNAMICS REMAIN NORTH...THE THERMODYNAMICS ARE
BETTER SOUTH WITH ALMOST 20 CELSIUS 850 MB THERMAL RIDGE INTO
SOUTHEAST WISCONSIN BY NOON. THAT DROPS TO NEAR THE ILLINOIS BORDER
BY EARLY EVENING. ZERO TO 1 KM RESULTING IN 2000 J/KG OF CAPE INTO
THE EARLY EVENING IN THE FAR SOUTHEAST AS THE SURFACE FRONT FINALLY
EXITS THE FAR SOUTHEAST.
THEREFORE EXPECT THE MINNESOTA MCS THAT HAS MERGED WITH THE
THUNDERSTORMS ON THE BACK SIDE OF THE OUTFLOW BOUNDARY FROM LAST
EVENINGS MCS TO PUSH EAST AS THE 700 MB WIND MAX MOVES THROUGH.
BEST LIFT NORTH BUT BEST INSTABILITY WELL SOUTH AS THIS MCS MOVES
OUT OF THE HIGH CAPE ENVIRONMENT. THEREFORE EXPECT THE STORMS FROM
THIS MCS TO CONTINUE TO WEAKEN AS IT MOVES ACROSS THE FORECAST AREA
EARLY THIS MORNING. RAP SOUNDINGS ARE QUITE STABLE WITH MID LEVEL
DRY AIR OVER MOST OF THE FORECAST AREA..
THEN THERE WILL BE A CHANCE FOR MORE THUNDERSTORMS THIS AFTERNOON
WITH THE COLD FRONT. HOWEVER BEST DYNAMICS ARE NORTHEAST...WITH
BEST INSTABILITY TO OUR SOUTH. NAM FORECAST SOUNDINGS DO SHOW
STEEP LAPSE RATES IN THE LOW TO MID LEVELS AGAIN THIS
AFTERNOON...ESPECIALLY SOUTHEAST WITH 10C/KM AT 900 MB TO 8 C/KM AT
500 MB. WITH PRECIPITABLE WATER VALUES AROUND 1.6 INCHES...MORE
STORMS ARE POSSIBLE...ALTHOUGH THE BEST SEVERE THREAT SHOULD BE TO
OUR SOUTH AND EAST. INTERESTING IS THE LOCAL SEVERE ENVIRONMENT
PROBABILITY CWASP OFF THE NAM HAS HIGHER VALUES THIS AFTERNOON 75
PCT THAN IT DID YESTERDAY WITH THE FIRST MCS 65 PCT.
STRONG MID LEVEL DRYING LATE TONIGHT BEHIND THE COLD FRONT.
THURSDAY...FORECAST CONFIDENCE IS HIGH.
A DRIER AND COOLER AIRMASS WILL SETTLE INTO SOUTHERN WI WITH HIGH
PRESSURE IN THE WAKE OF THE FRONT. THE MAJORITY OF MODELS AGREE THAT
THE SURFACE COLD FRONT AND 850MB BAROCLINIC ZONE WILL BE SOUTH OF
THE WI BORDER BY 12Z THU SO KEPT THU DRY. EXPECTING A PLEASANTLY
MOSTLY SUNNY DAY WITH HIGHS IN THE UPPER 70S AND LOW DEWPOINTS.
THURSDAY NIGHT THROUGH FRIDAY...FORECAST CONFIDENCE IS MEDIUM.
A LARGE UPPER TROUGH WILL SWING ACROSS THE UPPER MIDWEST AND GREAT
LAKES REGION FRIDAY AND FRIDAY NIGHT. SHOWERS COULD SPREAD INTO
SOUTHERN WI AS EARLY AS THU NIGHT WITH WEAK WARM AIR ADVECTION AND
THE NOSE OF THE UPPER JET INTO THE AREA. BY AROUND 18Z FRIDAY IT
LOOKS LIKE THE STRONGER FORCING WITH THE RIGHT ENTRANCE REGION OF
THE UPPER JET AND STRONGEST FRONTOGENESIS WILL BE MAINLY SOUTH OF
THE WISCONSIN BORDER. THE OTHER BETTER AREA OF FORCING WITH THE MAIN
UPPER TROUGH AND VORT MAX WILL BE CLOSER TO NORTHERN WISCONSIN AND
UPPER MICHIGAN. REDUCED THE POPS SLIGHTLY...BUT KEPT THE CHANCE OF
SHOWERS WORDING FOR FRIDAY. EXPECTING RAIN TO BE LIGHT AND NOT
AMOUNT TO MUCH.
OVERALL FRIDAY WILL BE CLOUDY AND COOL WITH OFF AND ON RAIN SHOWERS.
MAX TEMPS EXPECTED AROUND 70.
THE SURFACE COLD FRONT SHOULD PUSH SOUTH OF THE WI BORDER BY LATE
FRI AFTERNOON. SHOWERS COULD LINGER INTO THE EVENING UNTIL THE UPPER
TROUGH CLEARS THE AREA...BUT DRY AIR WORKING IN BEHIND THE SYSTEM
SHOULD CUT PRECIP CHANCES SIGNIFICANTLY AFTER MIDNIGHT.
LONG TERM...
SATURDAY...FORECAST CONFIDENCE MEDIUM TO HIGH.
MUCH COOLER AIR WILL SETTLE INTO WI BEHIND THIS UPPER TROUGH AND
SURFACE COLD FRONT BY SATURDAY MORNING AND PERSIST THROUGH THE WEEKEND.
ONE MORE LOBE OF VORTICITY IS FORECAST TO SWING DOWN ACROSS WI SAT
NIGHT. ECMWF AND GFS SPIT OUT SMALL QPF AMOUNTS...BUT EXPECTING THE
ATMOSPHERE TO BE TOO DRY SO LEFT OUT POPS.
925MB TEMPS SHOULD DIP DOWN TO AROUND 12C ON SATURDAY...YIELDING MAX
TEMPS IN THE UPPER 60S WITH AMPLE SUNSHINE. THERE COULD BE A BIT OF
A NORTHWEST BREEZE DURING THE AFTERNOON.
SUNDAY THROUGH WEDNESDAY...FORECAST CONFIDENCE HIGH.
ECMWF AND GFS ARE NOW ON THE SAME TRACK WITH AN OPEN-WAVE 500MB LOW
THAT REMAINS PROGRESSIVE AND MOVES EAST OVER THE WEEKEND. A STRONG
HIGH PRESSURE RIDGE WILL BUILD BACK INTO THE UPPER MIDWEST THROUGH
THE FIRST HALF OF THE WEEK. MAX TEMPS WILL BE IN THE LOW TO MID 70S
WITH LOW DEWPOINTS. NO PRECIP EXPECTED AND THERE SHOULD BE PLENTY OF
SUNSHINE.
AVIATION/12Z TAFS/...
ONE COMPLEX OF THUNDERSTORMS HAS PUSHED EAST...BUT A SECOND AREA OF
STRONG STORMS OVER SOUTHEAST MINNESOTA WILL PUSH EAST ACROSS MUCH OF
THE FORECAST AREA BUT WEAKEN DUE TO MORE STABLE AIR OVER SOUTH
CENTRAL AND SOUTHEAST WISCONSIN.
THEN ANOTHER CHANCE OF THUNDERSTORMS WITH A COLD FRONT THAT WILL
PUSH ACROSS SOUTHERN WISCONSIN TODAY. SOME OF THESE COULD BE STRONG
LATER THIS AFTERNOON IN THE SOUTHEAST.
MAINLY VFR CIGS...BUT MVFR/IFR IN THE THUNDERSTORMS.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&
$$
UPDATE...DDV
TODAY/TONIGHT AND AVIATION/MARINE...HENTZ
THURSDAY THROUGH TUESDAY...MRC
AREA FORECAST DISCUSSION
NWS COLUMBIA SC
1055 AM EDT WED SEP 5 2012
.SYNOPSIS...
UPPER LEVEL TROUGH ASSOCIATED WITH THE REMNANTS OF ISAAC WILL
CONTINUE TO GIVE OUR AREA WARM AND HUMID WEATHER WITH CHANCES OF
SHOWERS AND THUNDERSTORMS THROUGH THURSDAY. THE UPPER TROUGH WILL
SHIFT OFFSHORE BY THURSDAY AS A COLD FRONT APPROACHES FROM THE
WEST ON FRIDAY. THIS WILL BRING ANOTHER CHANCE OF SHOWERS AND
THUNDERSTORMS TO THE AREA FOR THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A FEW SHOWERS STARTING TO DEVELOP IN THE UPSTATE LATE THIS
MORNING. IR/WV SATELLITE IMAGERY SHOWS MAINLY LOW AND MID LEVEL
CLOUDINESS ASSOCIATED WITH UPPER TROUGH WHICH HAS WEAKENED AND
NOW CONTAINS LESS DEEP TROPICAL MOISTURE. THE WV CURVE ACTUALLY
SHOWS SOME DRIER AIR INTERACTING WITH UPPER LOW IN THE WESTERN
PORTION OF THE FORECAST AREA. DECIDED TO LOWER POPS ABOUT 4-5
PERCENT BECAUSE EXPECT LESS COVERAGE. WILL CONFINE 40 PERCENT
TO NORTH AND WEST OF CAE AREA AND KEEP CLOSE TO 30 PERCENT REST
OF AREA. AFTERNOON HIGHS MAINLY IN THE UPPER 80S STILL OK.
SPC HAS REGION IN SEE TEXT BUT WITH RUC AND NAM FORECAST SOUNDINGS
SHOWING SOME DRYING ALOFT...COULD NOT RULE OUT ISOLATED STORMS
WITH STRONG DOWNDRAFTS IF ATMOSPHERE BECOMES UNSTABLE ENOUGH.
RIGHT NOW MODELS ONLY SHOW MEAGER INSTABILITY WITH LIS -2/-4 AND
CAPES AROUND 1000 J/KG. SPC DOWNDRAFT CAPES LOW LESS THAN 800.
SO CHANCES FOR SEVERE STORMS REMAIN QUITE LOW. OTHERWISE...PWS
ARE STILL UP AROUND 2 INCHES. SO THE THREAT FOR SOME HEAVY RAIN
CONTINUES MUCH LIKE PREVIOUS DAYS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
CONVECTIVE ACTIVITY WILL DIMINISH WITH SUNSET AS THE MOISTURE
PLUME AND UPPER LEVEL TROUGH CONTINUE TO SLOWLY SWING INTO THE
FORECAST AREA. BY THURSDAY AFTERNOON THE UPPER LEVEL TROUGH WILL
BE CENTERED OVER THE REGION AND SLIDE TO THE COAST THURSDAY NIGHT.
THIS WILL ALLOW SLIGHTLY DRIER AIR TO MOVE INTO THE NORTHERN
MIDLANDS ON FRIDAY AS THE CHANCE OF SHOWERS MOVES TOWARD THE
COAST. THIS WILL RESULT IN MAINLY DIURNAL SHOWERS AND
THUNDERSTORMS OVER THE AREA EACH AFTERNOON WITH ACTIVITY
DIMINISHING WITH THE LOSS OF HEATING. WITH THE MOISTURE PLUME ALSO
WEAKENING THE CHANCE OF LOCALIZED HEAVY RAINFALL WILL CONTINUE TO
LESSEN. TEMPERATURES WILL GENERALLY BE IN THE UPPER 80S TO AROUND
90 WITH OVERNIGHT LOWS IN THE LOWER 70S.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
MODELS ARE IN GOOD AGREEMENT THROUGH THE LONG TERM WITH SOME MINOR
DIFFERENCES IN TIMING WITH THE FRONTAL SYSTEM FOR THE WEEKEND.
PATTERN WILL REMAIN ACTIVE THROUGH THE FIRST HALF OF THE LONG TERM
AS LOW PRESSURE PUSHES THROUGH THE GREAT LAKES REGION AND A COLD
FRONT CROSSES THE EASTERN US SATURDAY AND SUNDAY. THIS WILL RESULT
IN A CHANCE OF SHOWERS AND THUNDERSTORMS SATURDAY AND SUNDAY WITH
THE FRONT MOVING OFFSHORE SUNDAY NIGHT. BEHIND THE FRONT HIGH
PRESSURE ALONG WITH COOLER AND DRIER AIR WILL MOVE INTO THE REGION
WITH OVERNIGHT LOW TEMPERATURES EXPECTED TO FALL IN TO THE LOWER
60S. THE HIGH PRESSURE WILL REMAIN DOMINANT OVER THE AREA FROM
SUNDAY NIGHT THROUGH TUESDAY. TEMPERATURES THROUGH THE LONG TERM
WILL BE NEAR TO SLIGHTLY ABOVE NORMAL FOR FRIDAY THROUGH
SUNDAY...THEN SLIGHTLY BELOW NORMAL SUNDAY NIGHT THROUGH TUESDAY.
&&
.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
STRATUS AND STRATOCU CONTINUE TO LIFT AS SURFACE HEATING HAS BROUGHT
TEMPERATURES INTO THE UPPER 70S AND LOWER 80S. MAYBE 1-2 MORE HOURS
OF MVFR CEILINGS BUT SHOULD BECOME MOSTLY VFR BY NOON. WITH AFTERNOON
HEATING...ATMOSPHERE WILL BECOME MORE UNSTABLE BUT MODELS NOT SHOWING
BECOMING VERY UNSTABLE. MODELS GIVE ONLY MEAGER INSTABILITY WITH LIS
-2/-4 AND CAPES AROUND 1000 J/KG BUT EXPECT STRONG LOW LEVEL LAPSE
RATES WHICH MAY ALLOW SHOWERS AND THUNDERSTORMS TO DEVELOP. IT LOOKS
LIKE THE COVERAGE SHOULD BE LESS THAN YESTERDAY. DUE TO UNCERTAINTY
AS TO THE TIMING AND LOCATION...DECIDED NOT TO INCLUDE AT TAF SITES.
ANY THAT DO AFFECT ANY TAF SITE MAY HAVE BRIEF IFR-MVFR CONDITIONS.
A FEW SHOWERS AND THUNDERSTORMS MAY LINGER INTO THE EVENING HOURS
BUT ARE EXPECTED TO BE GONE BY 04Z OR MIDNIGHT. AFTER MIDNIGHT...
NAM BUFKIT IS SHOWING LOW LEVEL WINDS SOUTHWEST AT 10-15 KNOTS BELOW
1 KFT. SO NOT MUCH IN THE WAY OF FOG EXPECTED BUT MVFR VSBYS STILL
POSSIBLE AT AGS AND OGB NEAR SUNRISE THURSDAY. ANOTHER ISSUE IS
STRATUS CEILINGS. RIGHT NOW...MODELS SUGGEST LESS LOW LEVEL MOISTURE
THAN PREVIOUS DAYS. SO THE POTENTIAL FOR LOW CEILINGS HAS DIMINISHED.
WITH LOW CONFIDENCE...DECIDED NOT TO INCLUDE IFR CEILINGS THURSDAY
MORNING AT TAF SITES.
EXTENDED AVIATION OUTLOOK...RESTRICTIONS MAINLY FOR AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&
$$
07
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
423 PM EDT WED SEP 5 2012
.SHORT TERM...
TONIGHT THROUGH THURSDAY NIGHT.
SHORT/SMALL WINDOW OF OPPORTUNITY WRT DESTABILIZATION INADOV SFC
FNTL BNDRY ACRS XTRM SERN WI/NRN IL/ERN IA/MO LATE THIS AFTN. OF
NOTE HAS BEEN SPC RAP FAILURE TO ADEQUATELY ASSESS DOWNSTREAM
STABILIZATION AMID WAKE OF MATURE BUBBLE MESOHIGH BEHIND LATE
AM/ERLY AFTN LINEAR CONVECTION THAT NOW ARCHES FM NRN OH TO OH RVR
VALLEY. WHILE EWD ADVANCE OF STEEP 7-5H LAPSE RATES OF 8-9 C/KM
OMINOUS...THE CERTAINLY FAR FROM PRISTINE 0-3KM THERMODYNAMIC
ENVIRON ACRS NERN IL/CWA AMID DENSE CONVECTIVE DEBRIS AND WELL
OVERTURNED ATMOS...WL LKLY QUELL ALL BUT JUST A FLEETING HOPE FOR
ANY FIRM CONVECTIVE MAINTENANCE WITH ERN EXTENT. GIVEN
CONDITIONALITY WRT LATE AFTN INITIATION WITH MODEST LLVL WIND
PROFILE/LWST 100 MB CONVERGENCE AHEAD OF FNT...AND ADDED
CONDITIONALITY FURTHER DOWNSTREAM...HAVE CHOSE LOWER END GUID WITH
NO HIER THAN MID RANGE CHC POPS AFT 02 UTC. SEVERE RISK ALSO
APPEARS TO BE WANING...BUT WL LET HWO CONTINUE TO COVER WITH HIEST
RISKS ACRS SRN CWA/ALONG PROGGED OVERLAP OF SFC CAPE RESERVOIR
AND MODERATE DEEP LYR SHEAR/INCRSG THIS EVE AS 50 KT 5H WNWLY FLOW
ACRS IL/WI SURGES EWD. NIL WX AFTER TONIGHT IN DRYING LLVL ATMOS.
HAVE LWRD TEMPS INVOF KBEH SUBSTANTIALLY TMWR NIGHT IN WEAKENING
SFC FLOW AS 1018 MB PLAINS HIGH SETTLES ACRS SRN GRTLKS...FAVORING
COOL DRAINAGE ALONG LAKESHORE NEAR DAYBREAK FRI.
&&
.LONG TERM...
FRIDAY THROUGH WEDNESDAY...A SIGNIFICANT TROF WILL MOVE ACROSS THE
WESTERN GREAT LAKES REGION EARLY IN THE PERIOD. BOTH THE GFS AND THE
ECMWF HAVE ABANDONED THE EARLY CUT OFF LOW SOLUTION FROM MANY
PREVIOUS RUNS IN LIEU OF A MORE PROGRESSIVE OPEN WAVE SOLUTION DUE
TO MORE PHASING WITH THE NORTHERN STREAM AND THE APPROACH OF ANOTHER
UPSTREAM UPPER TROF. HOWEVER...THE ONGOING TIMING OF THE ARRIVAL OF
THE MAIN TROF OVER THE WESTERN GREAT LAKES REGION STILL APPEARS ON
TRACK WITH THE BEST CHANCE FOR RAIN FRIDAY NIGHT. KEPT SHOWERS
LIKELY FRIDAY NIGHT. ADDED A CHANCE FOR THUNDER SOUTHEAST HALF PER
ECMWF WITH EMBEDDED STORMS POSSIBLE GIVEN MOISTURE AND LIFT
AVAILABLE. OTHERWISE...COOLER AND DRY CONDITIONS SUNDAY AND MONDAY
FOLLOWED BY A RETURN TO ABOVE NORMAL TEMPERATURES WEDNESDAY AND THE
UPPER LEVEL RIDGE BUILDS EAST AHEAD OF THE NEXT UPPER LEVEL TROF CAN
BE EXPECTED. THE 500 MB CANADIAN AND GFS ANALOGS ALSO SUPPORT
TEMPERATURES RISING ABOVE NORMAL.
&&
.AVIATION... /18 UTC TAF/
UPSTREAM DESTABILIZATION RATHER SLOW TO RECOMMENCE HAS PLACED ADDED
CONDITIONALITY UPON CONVECTION ASSOCD WITH PRIMARY FRONTAL BOUNDARY
XTNDG FM SCNTL WI SEWD THROUGH IA TO NWRN MO LATER THIS AFTN. TIMING
WOULD PLACE THIS INTO NWRN IN AFTER SUNSET. ADDED UNCERTAINTY WRT
UNFAVORABLE CONVECTION MAINTENANCE WITH DOWNSTREAM EXTENT WITH SFC
STABILIZATION INCRSG AND MEAGER LLVL WIND FIELD. FOR NOW HAVE
COVERED GRTST POTNL TIMEFRAME WITH 4 HOUR VCTS GROUPINGS AS GRTR
CONFIDENCE FOR TEMPO LACKING ATTM.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
SHORT TERM...MURPHY
LONG TERM...SKIPPER
AVIATION...MURPHY
AREA FORECAST DISCUSSION...UPDATED
NWS ST LOUIS MO
107 PM CDT WED SEP 5 2012
.UPDATE...
ISSUED AT 1240 PM CDT WED SEP 5 2012
SHOWERS AND THUNDERSTORMS OVERSPREAD THE AREA THIS MORNING
COINCIDENT WITH MULTIPLE OUTFLOW BOUNDARIES AND AN MCV DRIFTING
ACROSS THE REGION FROM SW MISSOURI. THUS FAR...RAINFALL AND
CLOUDCOVER HAVE KEPT TEMPERATURES QUITE A BIT COOLER THAN
ORIGINALLY EXPECTED...AND DESPITE A REBOUND ON TAP FOR THIS
AFTERNOON AS THE CLOUDS DISSIPATE...CURRENTLY DO NOT EXPECT THE
METRO AREA TO REACH HEAT ADVISORY CRITERIA. LOCATIONS ACROSS
SOUTHEASTERN MISSOURI AND SOUTHERN ILLINOIS HOWEVER...WHERE
PRECIPITATION AND CLOUDCOVER HAD LESS OF AN IMPACT...COULD VERY
WELL SEE HEAT INDICES IN THE 100-105 DEGREE RANGE. SO HAVE
CONTINUED THE ADVISORY FOR THOSE AREAS.
THE BIG QUESTION THAT REMAINS IS WHETHER ENOUGH DESTABILIZATION
WILL OCCUR TO SUPPORT CONVECTIVE DEVELOPMENT THIS AFTERNOON AND
EVENING IN THE WARM SECTOR AHEAD OF THE APPROACHING COLD FRONT.
MODELS DID NOT CAPTURE THIS MORNINGS ACTIVITY VERY WELL...THOUGH
THE MOST RECENT RUN OF THE HRRR DOES FIRE SOME STORMS LATE THIS
AFTERNOON AHEAD OF THE FRONT. GIVEN UNCERTAINTY...HAVE CONTINUED
CHANCE-HIGH CHANCE POPS FOR THE AREA THIS AFTERNOON AND EARLY THIS
EVENING.
JP
&&
.SHORT TERM...
ISSUED AT 331 AM CDT WED SEP 5 2012
(TODAY AND TONIGHT)
CHALLENGING FORECAST FOR TODAY...MULTIPLE OUTFLOW BOUNDARIES ARE
MOVING INTO THE CWFA FROM THE WEST...THE NORTH-NORTHWEST..AND THE
NORTHEAST THIS MORNING. THE AFFECTS OF WHICH MAY BE MANIFOLD. THE
OVERALL SYNOPTIC PATTERN LOOKS QUITE HOT. AM DISCOUNTING THE
GFS/MAV TEMPERATURES FOR TODAY SINCE IT`S BEEN TOO COLD ALL SUMMER.
THE NAM LOOKS MORE REASONABLE WITH HIGHS OF 95 TO 103 ACROSS THE
CWFA. 00Z 850MB ANALYSIS FROM LAST NIGHT SHOWS 24-25C AIR LURKING
JUST TO OUR SOUTHWEST AND HIGHS REACHED THE 96-105F RANGE ACROSS
SOUTHWEST MISSOURI...ARKANSAS...EASTERN KANSAS...AND OKLAHOMA
YESTERDAY. I SEE NO REASON THAT WE WON`T GET THAT WARM
TODAY...EXCEPT FOR THOSE PESKY OUTFLOW BOUNDARIES AND CONVECTIVE
DEBRIS FROM NOCTURNAL CONVECTION. HOWEVER...AM GOING TO STICK WITH
A WARM FORECAST TODAY. AM THINKING THAT THE CONVECTIVE DEBRIS WILL
CLEAR THE AREA BY MID MORNING AND SHOULDN`T HAVE THAT MUCH IMPACT ON
TEMPERATURES. THE OUTFLOW BOUNDARIES AREN`T COOLING THINGS OFF
EITHER...ALL THEY`RE DOING IS MIXING DOWN WARMER AIR ALOFT...AND
TEMPERATURES ARE ACTUALLY RISING AS THEY PASS. OUTFLOW BOUNDARIES
COULD SERVE AS FOCI FOR CONVECTIVE DEVELOPMENT THIS AFTERNOON...AND
IF CONVECTIVE INITIATION OCCURS TOO EARLY WOULD BE THE PRIMARY
REASON FOR A HIGH TEMPERATURE BUST. REGARDLESS...HIGH DEWPOINTS
AHEAD OF THE COLD FRONT OVER EASTERN MISSOURI AND PARTS OF SOUTHWEST
ILLINOIS COMBINED WITH TEMPERATURES NEAR 100 WILL LIKELY CAUSE HEAT
INDEX VALUES AROUND 105. HAVE GONE AHEAD AND ISSUED A HEAT ADVISORY
TO COVER THIS. EXPECTING SOME DRIER AIR TO MIX DOWN ACROSS CENTRAL
AND NORTHEAST MISSOURI/WEST CENTRAL ILLINOIS WHICH SHOULD HEAT INDEX
VALUES BELOW 105.
TONIGHT SHOULD BE INTERESTING...NAM IS HINTING THAT A STRONG
THUNDERSTORM COMPLEX WILL DEVELOP SOMEWHERE OVER NORTHERN/WEST
CENTRAL ILLINOIS OR EASTERN IOWA AND DROP SOUTHEAST. NAM AND RAP
DEVELOP EYE-POPPING MUCAPE VALUES IN EXCESS OF 4800 J/KG IN THOSE
AREAS AHEAD OF THE FRONT EARLY THIS AFTERNOON TO SUPPORT THE
CONVECTION...AND 0-6KM SHEAR VALUES IN EXCESS OF 30KTS ARE MORE THAN
ENOUGH TO SUPPORT SEVERE WEATHER. THINK A LARGE SEVERE MCS IS
LIKELY UP THERE...JUST UNSURE HOW FAR SOUTH INTO OUR AREA IT WILL
EXTEND. THINK THAT SOME PARTS OF OUR AREA WILL DEFINITELY SEE
THUNDERSTORMS...IF NOT SOME SEVERE WEATHER...JUST UNSURE WHAT THE
AREAL EXTENT WILL BE...SO HAVE KEPT CHANCE-HIGH CHANCE GOING FOR NOW.
CARNEY
&&
.LONG TERM...
ISSUED AT 357 AM CDT WED SEP 5 2012
(THURSDAY THROUGH TUESDAY)
CURRENT THINKING REMAINS BASICALLY UNCHANGED THROUGH EARLY NEXT
WEEK. TONIGHT`S COLD FRONT SHOULD BE THROUGH MOST OF THE AREA BY
12Z THURSDAY MORNING. THE FRONT HANGS UP ACROSS EXTREME SOUTHERN
MISSOURI OR NORTHERN ARKANSAS THURSDAY TEMPERATURES SHOULD BE 8-10
DEGREES COOLER THURSDAY BEHIND THE FRONT...AND BOTH THE GFS AND NAM
HAVE IT FAR ENOUGH SOUTH THAT ONLY EXTREME SOUTHEAST MISSOURI SHOULD
HAVE ANY POSSIBILITY OF RAIN. THURSDAY NIGHT THE MAJOR SHORTWAVE
DROPS INTO THE NORTHERN PLAINS CAUSING THE LOW LEVEL JET TO TO RAMP
UP OVER KANSAS AND MISSOURI. ALL MODELS SHOW GOOD LOW LEVEL
MOISTURE CONVERGENCE AND SPREAD PRECIP OVER MUCH OF WESTERN AND
NORTHERN MISSOURI OVERNIGHT. BY FRIDAY AS THE SHORTWAVE SWINGS INTO
NEBRASKA THERE SHOULD BE WIDESPREAD PRECIP ACROSS THE AREA. RAIN AND
THUNDERSTORMS SHOULD COME END BEHIND THE COLD FRONT LATE FRIDAY
NIGHT. STILL THINK THERE COULD BE SOME SCATTERED AFTERNOON SHOWERS
SATURDAY AS COLD ADVECTION CONTINUES...THOUGH LATEST RUNS OF THE
ECMWF AND GFS ARE DRIER THAN YESTERDAY`S.
SHOULD HAVE A STRETCH OF BEAUTIFUL EARLY-FALL WEATHER SUNDAY AND
MONDAY WITH HIGHS IN THE 70S AND LOWS IN THE 50S. COULD SEE SOME
WARMER TEMPERATURES BUILD BACK INTO THE AREA BY TUESDAY AS THE ECMWF
DEVELOPS AN UPPER LEVEL RIDGE OVER THE AREA.
CARNEY
&&
.AVIATION...
ISSUED AT 1240 PM CDT WED SEP 5 2012
QUITE A BIT OF UNCERTAINTY THROUGH THIS FORECAST PERIOD. ONGOING
CONVECTION ACROSS THE REGION HAS TAPERED OFF ACROSS MISSOURI AND
CONTINUES TO MOVE EASTWARD THROUGH ILLINOIS...AND WAS NOT CAPTURED
WELL BY ANY OF THE MODELS. HENCE...THE POSSIBILITY OF
THUNDERSTORMS THIS AFTERNOON REMAINS UNCERTAIN DUE TO LINGERING
CLOUDCOVER AND STABLILZATION. THUS...HAVE CARRIED VFR CONDITIONS
THROUGH THE VALID TAF PERIOD FOR ALL SITES...WITH TEMPOS FOR SOME
LIGHT RAIN AS SHOWERS SLOWLY PERCOLATE ACROSS THE METRO AREA TAF
SITES.
A COLD FRONT IS STILL PROGGED TO MOVE THROUGH THE AREA THIS
EVENING AND TONIGHT...WHICH WILL VEER WINDS AROUND TO THE
NORTHWEST TONIGHT...AND NORTH ON THURSDAY. WILL CONTINUE TO
MONITOR CONDITIONS AND REASSESS THE FORECAST AS NEEDED DEPENDING
ON ANY CONVECTIVE DEVELOPMENT ALONG AND AHEAD OF THE APPROACHING FRONT.
SPECIFICS FOR KSTL...
JUST A FEW SHOWERS LINGERING ACROSS THE METRO AREA THIS AFTERNOON
IN THE WAKE OF MORNING CONVECTION...THUS HAVE INCLUDED A BRIEF
TEMPO FROM 18-19Z THIS AFTERNOON FOR SOME LIGHT RAIN AT THE
TERMINAL. STABLIZATION DUE TO CLOUDCOVER AND COOLER TEMPERATURES
COULD HINDER CONVECTIVE DEVELOPMENT THIS AFTERNOON AHEAD OF THE
APPROACHING COLD FRONT...THOUGH CONDITIONS WILL CONTINUE TO BE
CLOSELY MONITORED. CONDIFENCE IS TOO LOW AT THE MOMENT TO INCLUDE
MENTION OF PRECIPITATION IN THE TAF BEYOND THE TEMPO GROUP...WITH
VFR CONDITIONS EXPECTED THROUGH THE FORECAST AND WINDS VEERING TO
THE NORTH BEHIND THE APPROACHING FRONT WHICH SHOULD MAKE IT
THROUGH THE TERMINAL BY 00-03Z THIS EVENING.
JP
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR IRON MO-MADISON MO-
REYNOLDS MO-ST. FRANCOIS MO-STE. GENEVIEVE MO.
IL...HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR RANDOLPH IL.
&&
$$
WFO LSX
AREA FORECAST DISCUSSION
NWS ELKO NV
314 PM PDT WED SEP 5 2012
.SYNOPSIS...CURRENTLY...HIGH PRESSURE IS HOVERING OVER THE SILVER
STATE. MEANWHILE AN AREA OF LOW PRESSURE IS MOVING INTO
CALIFORNIA AND WILL CLIP NORTHWESTERN NEVADA TONIGHT. ISOLATED
THUNDERSTORMS POSSIBLE LATE THIS EVENING. OVER NORTHEASTERN
NEVADA...THE LOWS WILL DIP INTO THE FORTIES LATE TONIGHT AND EARLY
THURSDAY. THUNDERSTORMS POSSIBLE THURSDAY AFTERNOON.
&&
.SHORT TERM...TONIGHT THROUGH THURSDAY. THE NAM12 DEPICTS ENHANCED
CAPES AND PWS OVER CENTRAL NEVADA TODAY. ISOLATED CONVECTION
POSSIBLE ALTHOUGH THE BEST INGREDIENTS WILL MATERIALIZE JUST SOUTH
OF THE LKN CWA. AS TIME ELAPSES...PACIFIC ENERGY WILL CLIP THE
NORTHWEST PORTION OF THE LKN CWA TONIGHT...POSSIBLY FUELING A FEW
DRY THUNDERSTORMS. THE FGEN FORCING WITH THIS SYSTEM LOOKS ANEMIC
BUT THE UPPER LEVEL DIFFLUENCE WILL BE THERE...EVEN IF
TEMPORARILY. THE NAM12 AND THE HRRR ARE BOTH PINGING INTO CONVECTION
AGAIN TOMORROW OVER THE CENTRAL ZONES AS MOISTURE GETS ENTRAINED
INTO THE BACK SIDE OF THE MID-LEVEL LOW. THE NAM12 IS PROJECTING
NEGATIVE VALUES OF LI FROM TONOPAH TO CEDAR CITY BY 21Z AND WELL
UP TO DENIO AND JACKPOT BY 00Z...COUPLED WITH A SURGE IN PWS AND
+200 J/KG OF CAPE. THE ELY SOUNDING...IS BY FAR...THE MOST
IMPRESSIVE WITH TOMORROWS ROUND OF CONVECTION...COMPLETE WITH A
CLASSIC INVERTED-V PROFILE AND THE DEEPEST LAYER OF MOISTURE.
.LONG TERM...THURSDAY NIGHT THROUGH NEXT WEDNESDAY. DRY AND QUIET TO
START...BUT RAMPING UP AS FOUR CORNERS LOW AND NORTHEAST PACIFIC
HIGH WORK IN TANDEM TO BRING YET MORE SUBTROPICAL MOISTURE INTO THE
GREAT BASIN ON THE WEEKEND. THE UPPER LOW DRIFTS TO THE NORTHEAST
ALLOWING THE RIDGE TO COME WEST ON FRIDAY AND SATURDAY...WHICH
INHIBITS MOISTURE FLOW INTO THE REGION. AS THE LOW MOVE OVER THE
RIDGE...THE RIDGE FLATTENS AND CREEPS EAST A BIT ALLOWING PW`S TO
SHOOT BACK INTO CENTRAL AND NORTHERN NEVADA. BY SUNDAY
AFTERNOON...LOOKING AT PW`S IN THE 0.75" TO 0.90" RANGE OVER MOST OF
THE AREA. THIS PW AREA ACTUALLY CREEPS BACK IN SOONER THAN THE
WEEKEND...BUT LI`S ARE NOT FAVORABLE FOR CONVECTION UNTIL SUNDAY.
THEREAFTER...THUNDERSTORMS ARE IN THE FORECAST FOR THE SOUTHEAST
HALF OF THE FORECAST AREA...EAST OF LINE FROM ROUGHLY JACKPOT TO
TONOPAH THROUGH THE REST OF THE LONG RANGE PERIOD.
TEMPS WILL REMAIN ABOVE NORMAL IN THE DAY...WITH NEAR TO SLIGHTLY
ABOVE NORMAL AT NIGHT. THE FROST/FREEZE PROGRAM ENDS ON SEP 15...AND
IT APPEARS THAT WE MAY NOT BE ISSUING ANY WARNINGS OR
ADVISORIES...UNLESS THINGS REALLY CHANGE.
&&
.AVIATION...VFR THROUGH 00Z FRIDAY. ISOLATED -TSRA WILL AFFECT THE
VICINITY OF KTPH AND KELY 00Z THURSDAY THROUGH ABOUT 04Z THURSDAY.
ANOTHER ROUND OF VICINITY -TSRA WILL AFFECT KTPH...KELY...AND KWMC
ON THURSDAY AFTERNOON. AROUND KEKO...SOME CU BUILDUPS BUT NOT
BECOMING TS. DRAINAGE WINDS OVERNIGHT...BECOMING SW TO W 10-20 KNOTS
AT ALL SITES AFTER 20Z THURSDAY.
&&
.FIRE WEATHER...A LOW PRESSURE SYSTEM WILL CLIP NORTHWEST NEVADA
TONIGHT PRODUCING ISOLATED DRY THUNDERSTORMS OVER THE WESTERN PORTION
OF 467. NEW STARTS POSSIBLE. A SECOND AREA OF CONCERN WILL BE
OVER CENTRAL NEVADA WHERE MOISTURE IS PRESENT. LIGHTNING STRIKES
ALREADY OBSERVED OVER THE SOUTHERN PORTION OF 457 WHERE THE BEST
PWS HAVE BEEN PROGGED FOR THIS EVENING. ISOLATED THUNDERSTORMS
EXPECTED OVER CENTRAL ZONES...HOWEVER...EXPECTING A MIX OF DRY
AND WET THUNDERSTORMS. MODELS DEPICT A MORE ROBUST ROUND OF
MOISTURE OVER 457 AND 455 TOMORROW AFTERNOON.
&&
.LKN WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
97/98/98/97
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
611 PM EDT WED SEP 5 2012
.SYNOPSIS...
AFTERNOON CONVECTION...FOLLOWED BY DYING MCS MOVING INTO NORTHEAST
KY AND EXTREME SOUTHERN WV THIS EVENING. COLD FRONT ARRIVES THURSDAY
FOLLOWED BY AN UPPER LEVEL LOW AND SURFACE COLD FRONT FOR THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
UPDATED POPS/WX PER LATEST RADAR IMAGES SHOWING DIURNAL CONVECTION
DEVELOPING ACROSS THE SOUTHERN THIRD OF WV. SO...WENT MORE DETERMINISTIC
WITH HIGH LIKELIES. ONLY THE OLD RUN FROM THE HRRR DEPICTED THIS
ACTIVITY WITH THE REST OF MODELS OVERDOING THE REST OF THE AREA
WHICH REMAINS CLEAR SKIES AND DRY.
THE NAM SHOWS FORCING IN THE MID LEVEL OMEGA REACHING THE SOUTHERN
COAL FIELDS LATE THIS EVENING BY 00Z THU...BUT BELIEVE THAT IS
ASSOCIATED WITH THE APPROACHING MCS FEATURE INTO NORTHEAST
KY...WELL AHEAD OF A COLD FRONT.
PREVIOUS DISCUSSION BELOW...
ALMOST LIKE A MID SUMMER PATTERN WHERE WEAK FLOW IS DOMINATED BY
MESOSCALE INFLUENCES...BEFORE COLD FRONT APPROACHES FROM THE WEST
LATER THURSDAY. THE HI RES MODELS HAVE DONE A POOR JOB
INITIALIZING MCS OVER INDIANA THIS MORNING...AND APPARENTLY TOO
AGGRESSIVE IN PUSHING WEAK FRONT AND DEEPER MOISTURE OUT OF AREA
THIS AFTERNOON. THE NAM HAS DONE A BETTER JOB THAN THE GFS...AND
WILL USE NAM DETAILS. STILL...WILL HAVE TO BE MORE AGGRESSIVE THAN
MODELS EARLY IN TONIGHT PERIOD FOR EFFECTS OF THE INDIANA MCS AS
IT MOVES EAST AND WEAKENS. WILL INTRODUCE LOW POPS OVER SOUTHWEST
THIRD OF AREA EARLY TONIGHT TO ACCOUNT FOR POSSIBLE MCS BEFORE IN
SINKS SOUTH OUT OF THE AREA LATE TONIGHT. ALSO...WILL DOWN PLAY
NAM AGGRESSIVENESS ON ANOTHER MCS DROPPING SOUTHEAST OUT OF
NORTHERN INDIANA LATER TONIGHT...UNTIL WE SEE EFFECTS OF PRECEDING
MCS. IN SHORT...HAVE SOME SORT OF LOW POPS OVER THE WESTERN AND
SOUTHERN PORTIONS OVERNIGHT. TEMPS AGAIN OVERNIGHT WILL BE HIGHER
THAN GUIDANCE WITH THE HIGH MOISTURE...CLOSER TO MET NUMBERS.
FOR THURSDAY...COLD FRONT COMES ACROSS FROM THE NORTHWEST...MANLY
AFFECTING THE AREA IN THE AFTERNOON. AGAIN...UNCERTAINTY ON HOW
VIGOROUS THIS FRONT AND CONVECTION WILL BE PROMPTS A CHANCE POP WITH
THE FRONT. TEMPS WILL BE ON THE HIGH SIDE OF GUIDANCE...HITTING 90
MANY LOCATIONS.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY NIGHT/...
PRECIP WILL COME TO AN END FROM WEST TO EAST THURSDAY NIGHT AS WEAK
FRONT PULLS AWAY/DISSIPATES. NAM LINGERS MOISTURE INTO
FRIDAY...WHILE GFS IS A BIT FASTER MOVING IT OUT. HAVE SLIGHT CHANCE
POPS IN THE MOUNTAINS FRIDAY AFTERNOON TO ACCOUNT FOR ANY ISOLATED
DIURNAL CONVECTION THAT MAY DEVELOP.
ONLY A SHORT BREAK BEFORE THE NEXT SYSTEM MOVES IN FOR THE WEEKEND.
MODELS AND ENSEMBLES HAVE CONTINUED TRENDING TOWARDS THE IDEA OF AN
OPEN TROUGH...AND KEEP IT FAIRLY PROGRESSIVE. WITH THIS IN
MIND...SPED UP ENTIRE SYSTEM A BIT...WITH SLIGHT CHANCE POPS
ENTERING SE OHIO LATE FRIDAY EVENING AND INTO THE WV MOUNTAINS
OVERNIGHT. THEN HAVE LIKELY POPS INTO SE OHIO BY SATURDAY MORNING
AND THE WV MOUNTAINS EARLY SATURDAY AFTERNOON. KEPT THE HIGHEST POPS
ALONG AND IN FRONT OF THE SURFACE COLD FRONT...WHICH SHOULD CROSS
THE OHIO RIVER 18Z-20Z AND EXIT EAST OF FORECAST AREA SATURDAY
NIGHT.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
MADE WHOLESALE CHANGES TO THE LONG TERM FORECAST AS MODELS COMING
INTO BETTER AGREEMENT THAN YESTERDAY...NOW SHOWING OPEN WAVE
SWINGING THROUGH OVER THE WEEKEND...AND A THING OF THE PAST AS WE
HEAD INTO THE WORK WEEK. LINGER CHANCE AND SLIGHT CHANCE POPS
THROUGH SUNDAY...MOVING OUT SUNDAY NIGHT AS THE UPPER TROUGH MOVES
EAST AND OUT TO SEA. THIS WILL PROVIDE A MAINLY DRY FORECAST FOR THE
REST OF THE LONG TERM. DID NOT INCLUDE ANY POPS FOR THE WORK WEEK AT
THIS TIME DUE TO LACKING MOISTURE...BUT WITH NORTHWEST FLOW IT MAY
BE POSSIBLE TO GET A LITTLE SHORTWAVE RIPPLE THAT COULD POP A SHOWER
OR TWO AT SOME POINT. TEMPERATURES WILL START OFF BELOW NORMAL ON
MONDAY...WITH A GRADUAL WARMING TREND TO NEAR NORMAL BY MID TO LATE
WEEK AS UPPER RIDGE MOVES INTO SOUTHERN PLAINS.
&&
.AVIATION /22Z WEDNESDAY THROUGH MONDAY/...
18Z WEDNESDAY THRU 12Z THURSDAY...
INCREASED CONVECTION THRU EARLY AFTERNOON OVER SOUTHEASTERN WV AND
SOUTHWEST VA AS EASTWARD MOVING SHORT WAVE AND WEAK FRONTAL BOUNDARY
COLLIDE WITH DEEPER MOISTURE. MAIN EFFECT WILL BE AT BKW. THIS SHORT
WAVE WILL EXIT MOUNTAINS BY 21Z WITH CONVECTION DIMINISHING. VFR
OUTSIDE OF CONVECTION THIS AFTERNOON AND EVENING.
DYING EASTWARD MOVING MCS FROM INDIANA MAY CLIP THE SOUTHWESTERN
THIRD OF THE AREA EARLY TONIGHT AS IT TRIES TO DROP
SOUTHEAST...POSSIBLY AFFECTING HTS. ANOTHER MCS MAY DEVELOP AND
TRACK SOUTHEAST FROM NORTHERN INDIANA TO AFFECT NORTHWEST PORTIONS
OF AREA AFTER 08Z. ALL THIS OVERNIGHT ACTIVITY FORECAST IS WITH LOW
CONFIDENCE...AND WILL GO OPTIMISTIC FOR MAINLY MID CLOUDS WITH THESE
SYSTEMS. HOWEVER...FOG WILL FROM LATER TONIGHT AFTER
06Z...ESPECIALLY EAST PORTIONS WITH LESSER CLOUDS. WILL GO WITH MVFR
TO LOCALLY IFR FOG UNTIL 12Z.
AFTER 12Z...VFR CEILINGS WITH INCREASING CHANCE FOR JUST AFTER THIS
PERIOD AS COLD FRONT APPROACHES.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z FRIDAY...
FORECAST CONFIDENCE: LOW.
ALTERNATE SCENARIOS: EVOLUTION OF ANY OVERNIGHT COMPLEXES WILL
DETERMINE AMOUNT OF CLOUD AND FOG.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
UTC 1HRLY 20 21 22 23 00 01 02 03 04 05 06 07
EDT 1HRLY 16 17 18 19 20 21 22 23 00 01 02 03
CRW CONSISTENCY H H H H H H H H H H H H
HTS CONSISTENCY H H H H H H H H H H M H
BKW CONSISTENCY H H H H H H H H H H H H
EKN CONSISTENCY H H H H H H H H H H H L
PKB CONSISTENCY H H H H H H H H H H M H
CKB CONSISTENCY H H H H H H H H H H M H
AFTER 00Z FRIDAY...
IFR FOG EXPECTED AT MOST TERMINALS 06 TO 12Z THURSDAY. BRIEF IFR
POSSIBLE IN THUNDERSTORMS SATURDAY.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...ARJ/JMV/MZ
NEAR TERM...JMV
SHORT TERM...MZ
LONG TERM...MZ
AVIATION...JMV
AREA FORECAST DISCUSSION
NWS GREENVILLE-SPARTANBURG SC
530 PM EDT WED SEP 5 2012
.SYNOPSIS...
DEEP TROPICAL MOISTURE CURRENTLY OVER THE REGION WILL BEGIN TO
PROGRESSIVELY LESSENING THURSDAY INTO FRIDAY. A STRONG COLD FRONT
WILL MOVE OVER THE CAROLINAS THIS WEEKEND FOLLOWED BY HIGH PRESSURE
THAT WILL PROVIDE COOLER AND DRYER WEATHER INTO THE FIRST OF NEXT
WEEK.
&&
.NEAR TERM /THROUGH THURSDAY/...
530 PM EDT UPDATE...MADE LOWERING CHANGES TO THE POPS/QPF BASED ON
RADAR TRENDS WV IMAGERY AND WRF/ARW OUTPUT. VERY WEAK FORCING ACROSS
THE NRN ZONES AND ACTUAL SUBSIDENCE SOUTH ACROSS THE UPSTATE AND NE
GA HAVE PRECLUDED A SIGFNT CONVECTIVE THREAT IN STRENGTH AND
SPATIALLY THIS EVENING FOR AREAS OUTSIDE THE CENT/NRN NC MTNS AS
WELL AS AREAS SOUTH OF I40. MADE COSMETIC CHANGES TO THE SKY GRIDS
AND MINOR TWEAKS TO TEMPS/TDS...MAINLY ACROSS THE NC MTNS.
THE LATEST WATER VAPOR IMAGERY SHOWS DRIER MID LEVEL AIR SPREADING
ACROSS THE FORECAST AREA SOUTH OF INTERSTATE 40. THE MID LEVEL FLOW
IS QUITE WEAK OVER THE UPSTATE...NE GA AND FAR SRN NC AS A SPUR OF
DEEP LAYER RIDGING HAS PUSHED INTO THE FA FROM THE WEST...FINALLY
DISPLACING THE WEAK...MOIST TROUGH THAT HAD BEEN OVER THE REGION FOR
THE PAST SEVERAL DAYS. THE RAP BRINGS A WEAK SHORT WAVE ACROSS
WESTERN NC THIS EVENING. LLVL CONVERGENCE IS INCREASING OVER THE NC
MTNS AND FOOTHILLS AHEAD OF THE WAVE. THE MODELS ARE SPLIT ON
HOW FAR SOUTHEAST THIS CONVECTION GETS. THE GFS KEEPS IT OVER THE
MTNS AND FOOTHILLS...WHILE THE RAP AND NAM PUSH IT INTO THE NRN
SUBURBS OF CHARLOTTE. WITH THE FINGER OF DRIER AIR PUSHING INTO THE
SRN PIEDMONT I/VE GONE WITH A FORECAST THAT KEEPS THE BEST
CONVECTIVE CHANCES OVER THE MTNS AND FOOTHILLS WITH LOWER POPS ALONG
AND SOUTH OF I-85 AND BACK ACROSS THE SW NC MTNS. THIS IS NOT TO SAY
THAT STORMS WON/T PUSH INTO CHARLOTTE LATER THIS EVENING AS THE
ATMOSPHERE IS NOT CAPPED AND IS MODERATELY UNSTABLE. HOWEVER...THIS
DOES NOT LOOK LIKE THE MOST PROBABLE SOLUTION ATTM.
PATCHY DENSE VALLEY FOG IS EXPECTED OVER THE MTNS TONIGHT. ACROSS
THE FOOTHILLS AND PIEDMONT CONSIDERABLY LESS LOW CLOUD COVER IS
ANTICIPATED OWNING TO A MORE WESTERLY COMPONENT TO THE LLVL WIND
FIELD.
A SHORT WAVE CURRENTLY OVER CENTRAL MISSOURI IS EXPECTED TO CROSS
THE FORECAST AREA DURING THE AFTERNOON HOURS ON THURSDAY. THE DEEP
LAYER RH IS CONSIDERABLY HIGHER ON THU THAN TODAY ALONG AND AHEAD OF
THIS WAVE. BY 21 UTC THE FEATURE IS EXPECTED TO BE OVER THE I-77
CORRIDOR AND IT WILL MOVE EAT OF CHARLOTTE BY THE EARLY EVENING. THE
NAM AND GFS BOTH DEVELOP PCPN BY LATE MORNING AHEAD OF THE SHORT
WAVE. THE NAM HAS PCPN ENDING WITH WEAKLY DIVERGENT LLVL FLOW OVER
MOST OF THE FA DEVELOPING BETWEEN 21-00 UTC. THE WAY IT APPEARS
NOW...A BAND OF SHRA AND A FEW TSTMS WILL DEVELOP DEVELOP OVER THE
FOOTHILLS BY LATE MORNING...OR THEY MAY MOVE INTO THE MTNS AS A
REMNANT OF A WEAKENING MCS. THE CONVECTION WILL MOVE ACROSS THE REST
OF THE FOOTHILLS FROM EARLY TO MID AFTN AND EXIT TO THE EAST BY 6 OR
7 PM. THE SHEAR IS WEAK AND CONVECTION ISN/T EXPECTED TO BE HIGHLY
ORGANIZED AND MOST OF THE STORMS SHOULD BE SUB-SEVERE. THIS IS
GENERALLY SUPPORTED BY THE 12 UTC 4KM SPC WRF AS WELL. FOR NOW I/LL
CAP POPS ARE 40 PERCENT...WITH POPS FALLING OFF QUICKLY TOWARD
SUNSET.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 2 PM EDT WEDNESDAY...THE CONSENSUS OF THE MODEL GUIDANCE
MAINTAINS THAT THE PLUME OF DEEPER MOISTURE WILL HAVE SHIFTED
EASTWARD TO THE COASTAL PLAIN. IN THE WAKE OF A WEAK UPPER WAVE...
THE ENVIRONMENT SHOULD BE LESS FAVORABLE FOR DEEP CONVECTION. THE
CHANCE FOR SHOWERS AND STORMS SHOULD DROP IN THE EARLY EVENING AS
THE FORCING AND MOISTURE MOVE OFF TO THE EAST...TO THE POINT WHERE
THE FCST IS DRY EAST OF THE MTNS FROM 03Z ONWARD. THERE COULD BE A
FEW LINGERING SHOWERS OVER THE MTNS UNTIL LATE EVENING.
FRIDAY LOOKS LIKE A RELATIVELY QUIET TRANSITION DAY WHILE WE WAIT
FOR THE FORCING AND MOISTURE TO RELOAD. A STRONG SHORT WAVE OVER THE
UPPER MS VALLEY WILL DIG AN UPPER TROF DOWN OVER THE UPPER MIDWEST
AND GREAT LAKES THROUGH THE DAY...WHICH WILL GRADUALLY TURN THE FLOW
ALOFT MORE SW. UPPER FORCING WILL BE MINIMAL. THERE SHOULD BE ENOUGH
LOW LEVEL MOISTURE AND BUOYANCY TO SUPPORT SCATTERED SHOWERS AND
STORMS DEVELOPING OVER THE HIGHER TERRAIN WITH DIFFERENTIAL
HEATING...WITH SOME OF THE STORMS MOVING OUT OVER THE FOOTHILLS AND
PIEDMONT IN THE AFTERNOON AND EARLY EVENING. THE STORMS EAST OF THE
BLUE RIDGE WILL DIE OFF WITH SUNSET...BUT WILL KEEP THE CHANCE OF
PRECIP GOING OVERNIGHT ON THE W SIDE OF THE MTNS IN CASE SOME
ACTIVITY MOVES IN FROM THE WEST AHEAD OF THE NEXT FRONT.
THE UPPER TROF CONTINUES TO DIG OVER THE MIDWEST/OH VALLEY ON
SATURDAY AS THE WAVE DROPS SOUTHEASTWARD. DEEP MOISTURE MOVES IN
AHEAD OF THE WAVE TO BE ACTED UPON BY IMPROVED UPPER FORCING AS WE
WORK THROUGH THE DAY. THE OPERATIONAL RUNS FROM ALL THREE MODELS ARE
IN FAIRLY GOOD AGREEMENT WITH THE TIMING OF THE MAIN VORT AXIS
REACHING THE GREAT VALLEY LATE IN THE DAY. THE NEW GFS SWEEPS THE
UPPER TROF AXIS ACROSS THE WESTERN CAROLINAS OVERNIGHT WHILE THE 00Z
RUN PUSHES IT THROUGH SUNDAY MORNING. EITHER WAY...BOTH MODELS
SUGGEST AN EARLIER TIMING OF THE MAIN FRONTAL PRECIP BAND. WILL
LIMIT THE PRECIP TO THE CHANCE RANGE FOR THE TIME BEING BUT WILL
PROBABLY NEED A LIKELY POP FOR AT LEAST THE MTNS...BUT IT IS A
MATTER OF WHICH PERIOD TO FOCUS ON...SATURDAY AFTERNOON OR SATURDAY
NIGHT. WILL NOT RULE OUT SOME SEVERE STORMS IF THE FRONT WILL MOVE
THROUGH EARLY ENOUGH. AT THIS POINT...THINK MOST OF THE PRECIP WILL
HAVE MOVED EAST OF THE FCST AREA BY SUNRISE ON SUNDAY...WHICH AGREES
WITH THE HPC POSITION OF THE MAIN FRONT ON THE COAST AT THAT TIME.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 1130 AM EDT WEDNESDAY...AFTER DEALING WITH A SEMI-TROPICAL AIR
MASS FOR THE LAST TWO WEEKS...IT APPEARS AS THOUGH WE ARE IN FOR A
PERIOD OF SPECTACULAR EARLY AUTUMN-LIKE WEATHER EARLY NEXT WEEK. BUT
FIRST...WE HAVE TO GET A FRONT THROUGH THE CAROLINAS EARLY ON
SUNDAY. THE GFS MOVES THE MAIN SHORT WAVE LOBE ACROSS THE WESTERN
CAROLINAS EARLY SUNDAY MORNING WHILE THE ECMWF HAS THIS FEATURE
CROSSING SUNDAY AFTERNOON. THE TIMING IS FASTER THAN PREVIOUSLY
INDICATED...WITH THE MAIN SFC FRONT POTENTIALLY MOVING ACROSS THE
AREA SATURDAY NIGHT. WILL BACK OFF TO A SLIGHT CHANCE ACROSS THE
REGION ON SUNDAY AS A FEW SHOWERS COULD BE TRIGGERED BY A SECONDARY
FRONT. EITHER WAY...THERE IS A STRONG INDICATION THAT THE PRECIP
WILL BE LONG GONE BY SUNSET SUNDAY...SO THE PRECIP CHANCES ARE
ELIMINATED ALTOGETHER AFTER 00Z MONDAY.
THE UPPER TROF AXIS WILL REACH THE EASTERN SEABOARD BY MONDAY
MORNING AND MOVE SLOWLY OFFSHORE THROUGH MIDWEEK...WHILE AN UPPER
ANTICYCLONE REMAINS PARKED OVER THE SRN PLAINS. THE RESULTING UPPER
RIDGE TO OUR NW WILL BRING DRY HIGH PRESSURE BUILDING IN SUNDAY
NIGHT AND MONDAY. ONCE ESTABLISHED...THIS SURFACE HIGH WILL DOMINATE
OUR WEATHER AS IT MOVES SLOWLY PAST TO THE NORTH THROUGH WEDNESDAY.
THIS SHOULD BRING MOSTLY CLEAR SKY...DRY AIR...HIGH TEMPS IN THE
MID/UPPER 70S AND LOW TEMPS IN THE MID/UPPER 50S. THUS...MONDAY AND
TUESDAY WILL FEEL MORE LIKE LATE SEPTEMBER OR EARLY OCTOBER. THE AIR
MASS SHOULD START TO MODIFY A BIT BY WEDNESDAY.
&&
.AVIATION /22Z WEDNESDAY THROUGH MONDAY/...
AT KCLT 21Z UPDATE...BASED ON THE FAIRLY DEEP STABLE LAYER GENERALLY
ACROSS THE I-85 CORRIDOR...DECIDED TO REMOVE TEMPO -SHRA/VSBY AND
REPLACE WITH A VCSH. A FEW TOWERS COULD GO UP AROUND THE
AIRFIELD...BUT NO GOOD EVIDENCE IS HAD TO EXPECT A DIRECT TERMINAL
IMPACT. ALSO...BASED ON COORDINATION WITH THE NATIONAL GUARD AND
ZLT...AN MVFR CIG WAS INTRODUCED PRE/SUNRISE THROUGH 14Z.
AT KCLT...THE BULK OF THE TSTM ACTIVITY IS EXPECTED TO DEVELOP OVER
THE FOOTHILLS AND STAY 30 TO 50 MILES NORTHWEST OF THE AIRFIELD THIS
AFTERNOON AND EVENING. HOWEVER...THERE IS A LINE OF TCU BACK ACROSS
THE UPSTATE AND INTO THE SRN NC PIEDMONT THAT HAS BEEN PRODUCING
OCCASIONAL LIGHT SHRA. ATTM I HAVE REPLACED TEMPO THUNDER WITH TEMPO
SHRA IN THE TAF. IF STORMS DEVELOP FROM THE LINE OF TOWERS OVER THE
UPSTATE WE SHOULD STILL HAVE A COUPLE OF HOURS OF LEAD TIME BEFORE
THE STORMS AFFECT THE AIRFIELD. THE MODELS BRING SOME MID LEVEL
MOISTURE INTO THE REGION TONIGHT. THE LLVL FLOW ALSO VEERS TO THE
WEST. IF WE DON/T SEE ANY PCPN THIS EVENING...I THINK THE TWO
FACTORS ABOVE SHOULD KEEP STRATUS FROM DEVELOPING OVER THE REGION
TONIGHT.
ELSEWHERE...OVER THE UPSTATE ONLY ISOLATED SHRA ARE EXPECTED THE
REST OF THE AFTN. THERE IS A SMALL CHANCE THAT THE SHRA WILL BUILD
INTO TSTMS...BUT FOR NOW I THINK THE RISK IS TOO SMALL TO INCLUDE
THUNDER IN THE TAFS. WINDS WILL BE OUT OF THE SOUTHWEST AT SPEEDS
UNDER 10 KTS. THERE WILL BE A BETTER CHANCE OF SHRA/TSTMS AT KAVL
AND KHKY CLOSER TO A WEAK SFC TROUGH OF LOW PRESSURE. THE FOG AND
STRATUS FORECAST IS TRICKIER TONIGHT THAN IT HAS BEEN THE PAST
COUPLE DAYS. WINDS WILL VEER TO THE WEST OVERNIGHT. STRATUS MAY
APPROACH THE UPSTATE FROM THE SOUTHWEST LATE...BUT OVERALL I ONLY
SEE SOME MVFR FOG DEVELOPING. THE EXCEPTION WILL BE THE FRENCH BROAD
VALLEY WHERE VALLEY FOG AND STRATUS WILL BE MORE
WIDESPREAD...PARTICULARLY IF THERE IS A PERIOD OF CLEARING
OVERNIGHT. SHRA MAY SPREAD ACROSS THE MTNS AND FOOTHILLS SHORTLY
AFTER SUNRISE AHEAD OF A COLD FRONT THOUGH I/VE TONED THIS BACK IN
THE TAFS.
OUTLOOK...GRADUAL DRYING FROM THE WEST IS EXPECTED ON
THURSDAY...WITH DEEPER DRYING ON FRIDAY. A COLD FRONT WILL APPROACH
THE REGION FROM THE NORTHWEST ON SATURDAY AND MOVE EAST OF THE AREA
ON SUNDAY.
AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE
PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE
CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)...
WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.
&&
$$
SYNOPSIS...PM
NEAR TERM...MCAVOY/SBK
SHORT TERM...PM
LONG TERM...PM
AVIATION...MCAVOY/SBK
AREA FORECAST DISCUSSION
NWS GREENVILLE-SPARTANBURG SC
459 PM EDT WED SEP 5 2012
.SYNOPSIS...
DEEP TROPICAL MOISTURE CURRENTLY OVER THE REGION WILL BEGIN TO
PROGRESSIVELY LESSENING THURSDAY INTO FRIDAY. A STRONG COLD FRONT
WILL MOVE OVER THE CAROLINAS THIS WEEKEND FOLLOWED BY HIGH PRESSURE
THAT WILL PROVIDE COOLER AND DRYER WEATHER INTO THE FIRST OF NEXT
WEEK.
&&
.NEAR TERM /THROUGH THURSDAY/...
THE LATEST WATER VAPOR IMAGERY SHOWS DRIER MID LEVEL AIR SPREADING
ACROSS THE FORECAST AREA SOUTH OF INTERSTATE 40. THE MID LEVEL FLOW
IS QUITE WEAK OVER THE UPSTATE...NE GA AND FAR SRN NC AS A SPUR OF
DEEP LAYER RIDGING HAS PUSHED INTO THE FA FROM THE WEST...FINALLY
DISPLACING THE WEAK...MOIST TROUGH THAT HAD BEEN OVER THE REGION FOR
THE PAST SEVERAL DAYS. THE RAP BRINGS A WEAK SHORT WAVE ACROSS
WESTERN NC THIS EVENING. LLVL CONVERGENCE IS INCREASING OVER THE NC
MTNS AND FOOTHILLS AHEAD OF THE WAVE. THE MODELS ARE SPLIT ON
HOW FAR SOUTHEAST THIS CONVECTION GETS. THE GFS KEEPS IT OVER THE
MTNS AND FOOTHILLS...WHILE THE RAP AND NAM PUSH IT INTO THE NRN
SUBURBS OF CHARLOTTE. WITH THE FINGER OF DRIER AIR PUSHING INTO THE
SRN PIEDMONT I/VE GONE WITH A FORECAST THAT KEEPS THE BEST
CONVECTIVE CHANCES OVER THE MTNS AND FOOTHILLS WITH LOWER POPS ALONG
AND SOUTH OF I-85 AND BACK ACROSS THE SW NC MTNS. THIS IS NOT TO SAY
THAT STORMS WON/T PUSH INTO CHARLOTTE LATER THIS EVENING AS THE
ATMOSPHERE IS NOT CAPPED AND IS MODERATELY UNSTABLE. HOWEVER...THIS
DOES NOT LOOK LIKE THE MOST PROBABLE SOLUTION ATTM.
PATCHY DENSE VALLEY FOG IS EXPECTED OVER THE MTNS TONIGHT. ACROSS
THE FOOTHILLS AND PIEDMONT CONSIDERABLY LESS LOW CLOUD COVER IS
ANTICIPATED OWNING TO A MORE WESTERLY COMPONENT TO THE LLVL WIND
FIELD.
A SHORT WAVE CURRENTLY OVER CENTRAL MISSOURI IS EXPECTED TO CROSS
THE FORECAST AREA DURING THE AFTERNOON HOURS ON THURSDAY. THE DEEP
LAYER RH IS CONSIDERABLY HIGHER ON THU THAN TODAY ALONG AND AHEAD OF
THIS WAVE. BY 21 UTC THE FEATURE IS EXPECTED TO BE OVER THE I-77
CORRIDOR AND IT WILL MOVE EAT OF CHARLOTTE BY THE EARLY EVENING. THE
NAM AND GFS BOTH DEVELOP PCPN BY LATE MORNING AHEAD OF THE SHORT
WAVE. THE NAM HAS PCPN ENDING WITH WEAKLY DIVERGENT LLVL FLOW OVER
MOST OF THE FA DEVELOPING BETWEEN 21-00 UTC. THE WAY IT APPEARS
NOW...A BAND OF SHRA AND A FEW TSTMS WILL DEVELOP DEVELOP OVER THE
FOOTHILLS BY LATE MORNING...OR THEY MAY MOVE INTO THE MTNS AS A
REMNANT OF A WEAKENING MCS. THE CONVECTION WILL MOVE ACROSS THE REST
OF THE FOOTHILLS FROM EARLY TO MID AFTN AND EXIT TO THE EAST BY 6 OR
7 PM. THE SHEAR IS WEAK AND CONVECTION ISN/T EXPECTED TO BE HIGHLY
ORGANIZED AND MOST OF THE STORMS SHOULD BE SUB-SEVERE. THIS IS
GENERALLY SUPPORTED BY THE 12 UTC 4KM SPC WRF AS WELL. FOR NOW I/LL
CAP POPS ARE 40 PERCENT...WITH POPS FALLING OFF QUICKLY TOWARD
SUNSET.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 2 PM EDT WEDNESDAY...THE CONSENSUS OF THE MODEL GUIDANCE
MAINTAINS THAT THE PLUME OF DEEPER MOISTURE WILL HAVE SHIFTED
EASTWARD TO THE COASTAL PLAIN. IN THE WAKE OF A WEAK UPPER WAVE...
THE ENVIRONMENT SHOULD BE LESS FAVORABLE FOR DEEP CONVECTION. THE
CHANCE FOR SHOWERS AND STORMS SHOULD DROP IN THE EARLY EVENING AS
THE FORCING AND MOISTURE MOVE OFF TO THE EAST...TO THE POINT WHERE
THE FCST IS DRY EAST OF THE MTNS FROM 03Z ONWARD. THERE COULD BE A
FEW LINGERING SHOWERS OVER THE MTNS UNTIL LATE EVENING.
FRIDAY LOOKS LIKE A RELATIVELY QUIET TRANSITION DAY WHILE WE WAIT
FOR THE FORCING AND MOISTURE TO RELOAD. A STRONG SHORT WAVE OVER THE
UPPER MS VALLEY WILL DIG AN UPPER TROF DOWN OVER THE UPPER MIDWEST
AND GREAT LAKES THROUGH THE DAY...WHICH WILL GRADUALLY TURN THE FLOW
ALOFT MORE SW. UPPER FORCING WILL BE MINIMAL. THERE SHOULD BE ENOUGH
LOW LEVEL MOISTURE AND BUOYANCY TO SUPPORT SCATTERED SHOWERS AND
STORMS DEVELOPING OVER THE HIGHER TERRAIN WITH DIFFERENTIAL
HEATING...WITH SOME OF THE STORMS MOVING OUT OVER THE FOOTHILLS AND
PIEDMONT IN THE AFTERNOON AND EARLY EVENING. THE STORMS EAST OF THE
BLUE RIDGE WILL DIE OFF WITH SUNSET...BUT WILL KEEP THE CHANCE OF
PRECIP GOING OVERNIGHT ON THE W SIDE OF THE MTNS IN CASE SOME
ACTIVITY MOVES IN FROM THE WEST AHEAD OF THE NEXT FRONT.
THE UPPER TROF CONTINUES TO DIG OVER THE MIDWEST/OH VALLEY ON
SATURDAY AS THE WAVE DROPS SOUTHEASTWARD. DEEP MOISTURE MOVES IN
AHEAD OF THE WAVE TO BE ACTED UPON BY IMPROVED UPPER FORCING AS WE
WORK THROUGH THE DAY. THE OPERATIONAL RUNS FROM ALL THREE MODELS ARE
IN FAIRLY GOOD AGREEMENT WITH THE TIMING OF THE MAIN VORT AXIS
REACHING THE GREAT VALLEY LATE IN THE DAY. THE NEW GFS SWEEPS THE
UPPER TROF AXIS ACROSS THE WESTERN CAROLINAS OVERNIGHT WHILE THE 00Z
RUN PUSHES IT THROUGH SUNDAY MORNING. EITHER WAY...BOTH MODELS
SUGGEST AN EARLIER TIMING OF THE MAIN FRONTAL PRECIP BAND. WILL
LIMIT THE PRECIP TO THE CHANCE RANGE FOR THE TIME BEING BUT WILL
PROBABLY NEED A LIKELY POP FOR AT LEAST THE MTNS...BUT IT IS A
MATTER OF WHICH PERIOD TO FOCUS ON...SATURDAY AFTERNOON OR SATURDAY
NIGHT. WILL NOT RULE OUT SOME SEVERE STORMS IF THE FRONT WILL MOVE
THROUGH EARLY ENOUGH. AT THIS POINT...THINK MOST OF THE PRECIP WILL
HAVE MOVED EAST OF THE FCST AREA BY SUNRISE ON SUNDAY...WHICH AGREES
WITH THE HPC POSITION OF THE MAIN FRONT ON THE COAST AT THAT TIME.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 1130 AM EDT WEDNESDAY...AFTER DEALING WITH A SEMI-TROPICAL AIR
MASS FOR THE LAST TWO WEEKS...IT APPEARS AS THOUGH WE ARE IN FOR A
PERIOD OF SPECTACULAR EARLY AUTUMN-LIKE WEATHER EARLY NEXT WEEK. BUT
FIRST...WE HAVE TO GET A FRONT THROUGH THE CAROLINAS EARLY ON
SUNDAY. THE GFS MOVES THE MAIN SHORT WAVE LOBE ACROSS THE WESTERN
CAROLINAS EARLY SUNDAY MORNING WHILE THE ECMWF HAS THIS FEATURE
CROSSING SUNDAY AFTERNOON. THE TIMING IS FASTER THAN PREVIOUSLY
INDICATED...WITH THE MAIN SFC FRONT POTENTIALLY MOVING ACROSS THE
AREA SATURDAY NIGHT. WILL BACK OFF TO A SLIGHT CHANCE ACROSS THE
REGION ON SUNDAY AS A FEW SHOWERS COULD BE TRIGGERED BY A SECONDARY
FRONT. EITHER WAY...THERE IS A STRONG INDICATION THAT THE PRECIP
WILL BE LONG GONE BY SUNSET SUNDAY...SO THE PRECIP CHANCES ARE
ELIMINATED ALTOGETHER AFTER 00Z MONDAY.
THE UPPER TROF AXIS WILL REACH THE EASTERN SEABOARD BY MONDAY
MORNING AND MOVE SLOWLY OFFSHORE THROUGH MIDWEEK...WHILE AN UPPER
ANTICYCLONE REMAINS PARKED OVER THE SRN PLAINS. THE RESULTING UPPER
RIDGE TO OUR NW WILL BRING DRY HIGH PRESSURE BUILDING IN SUNDAY
NIGHT AND MONDAY. ONCE ESTABLISHED...THIS SURFACE HIGH WILL DOMINATE
OUR WEATHER AS IT MOVES SLOWLY PAST TO THE NORTH THROUGH WEDNESDAY.
THIS SHOULD BRING MOSTLY CLEAR SKY...DRY AIR...HIGH TEMPS IN THE
MID/UPPER 70S AND LOW TEMPS IN THE MID/UPPER 50S. THUS...MONDAY AND
TUESDAY WILL FEEL MORE LIKE LATE SEPTEMBER OR EARLY OCTOBER. THE AIR
MASS SHOULD START TO MODIFY A BIT BY WEDNESDAY.
&&
.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
AT KCLT 21Z UPDATE...BASED ON THE FAIRLY DEEP STABLE LAYER GENERALLY
ACROSS THE I-85 CORRIDOR...DECIDED TO REMOVE TEMPO -SHRA/VSBY AND
REPLACE WITH A VCSH. A FEW TOWERS COULD GO UP AROUND THE
AIRFIELD...BUT NO GOOD EVIDENCE IS HAD TO EXPECT A DIRECT TERMINAL
IMPACT. ALSO...BASED ON COORDINATION WITH THE NATIONAL GUARD AND
ZLT...AN MVFR CIG WAS INTRODUCED PRE/SUNRISE THROUGH 14Z.
AT KCLT...THE BULK OF THE TSTM ACTIVITY IS EXPECTED TO DEVELOP OVER
THE FOOTHILLS AND STAY 30 TO 50 MILES NORTHWEST OF THE AIRFIELD THIS
AFTERNOON AND EVENING. HOWEVER...THERE IS A LINE OF TCU BACK ACROSS
THE UPSTATE AND INTO THE SRN NC PIEDMONT THAT HAS BEEN PRODUCING
OCCASIONAL LIGHT SHRA. ATTM I HAVE REPLACED TEMPO THUNDER WITH TEMPO
SHRA IN THE TAF. IF STORMS DEVELOP FROM THE LINE OF TOWERS OVER THE
UPSTATE WE SHOULD STILL HAVE A COUPLE OF HOURS OF LEAD TIME BEFORE
THE STORMS AFFECT THE AIRFIELD. THE MODELS BRING SOME MID LEVEL
MOISTURE INTO THE REGION TONIGHT. THE LLVL FLOW ALSO VEERS TO THE
WEST. IF WE DON/T SEE ANY PCPN THIS EVENING...I THINK THE TWO
FACTORS ABOVE SHOULD KEEP STRATUS FROM DEVELOPING OVER THE REGION
TONIGHT.
ELSEWHERE...OVER THE UPSTATE ONLY ISOLATED SHRA ARE EXPECTED THE
REST OF THE AFTN. THERE IS A SMALL CHANCE THAT THE SHRA WILL BUILD
INTO TSTMS...BUT FOR NOW I THINK THE RISK IS TOO SMALL TO INCLUDE
THUNDER IN THE TAFS. WINDS WILL BE OUT OF THE SOUTHWEST AT SPEEDS
UNDER 10 KTS. THERE WILL BE A BETTER CHANCE OF SHRA/TSTMS AT KAVL
AND KHKY CLOSER TO A WEAK SFC TROUGH OF LOW PRESSURE. THE FOG AND
STRATUS FORECAST IS TRICKIER TONIGHT THAN IT HAS BEEN THE PAST
COUPLE DAYS. WINDS WILL VEER TO THE WEST OVERNIGHT. STRATUS MAY
APPROACH THE UPSTATE FROM THE SOUTHWEST LATE...BUT OVERALL I ONLY
SEE SOME MVFR FOG DEVELOPING. THE EXCEPTION WILL BE THE FRENCH BROAD
VALLEY WHERE VALLEY FOG AND STRATUS WILL BE MORE
WIDESPREAD...PARTICULARLY IF THERE IS A PERIOD OF CLEARING
OVERNIGHT. SHRA MAY SPREAD ACROSS THE MTNS AND FOOTHILLS SHORTLY
AFTER SUNRISE AHEAD OF A COLD FRONT THOUGH I/VE TONED THIS BACK IN
THE TAFS.
OUTLOOK...GRADUAL DRYING FROM THE WEST IS EXPECTED ON
THURSDAY...WITH DEEPER DRYING ON FRIDAY. A COLD FRONT WILL APPROACH
THE REGION FROM THE NORTHWEST ON SATURDAY AND MOVE EAST OF THE AREA
ON SUNDAY.
AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE
PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE
CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)...
WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.
&&
$$
SYNOPSIS...PM
NEAR TERM...MCAVOY
SHORT TERM...PM
LONG TERM...PM
AVIATION...MCAVOY/SBK
AREA FORECAST DISCUSSION
NWS GREENVILLE-SPARTANBURG SC
238 PM EDT WED SEP 5 2012
.SYNOPSIS...
DEEP TROPICAL MOISTURE CURRENTLY OVER THE REGION WILL BEGIN TO
PROGRESSIVELY LESSENING THURSDAY INTO FRIDAY. A STRONG COLD FRONT
WILL MOVE OVER THE CAROLINAS THIS WEEKEND FOLLOWED BY HIGH PRESSURE
THAT WILL PROVIDE COOLER AND DRYER WEATHER INTO THE FIRST OF NEXT
WEEK.
&&
.NEAR TERM /THROUGH THURSDAY/...
THE LATEST WATER VAPOR IMAGERY SHOWS DRIER MID LEVEL AIR SPREADING
ACROSS THE FORECAST AREA SOUTH OF INTERSTATE 40. THE MID LEVEL FLOW
IS QUITE WEAK OVER THE UPSTATE...NE GA AND FAR SRN NC AS A SPUR OF
DEEP LAYER RIDGING HAS PUSHED INTO THE FA FROM THE WEST...FINALLY
DISPLACING THE WEAK...MOIST TROUGH THAT HAD BEEN OVER THE REGION FOR
THE PAST SEVERAL DAYS. THE RAP BRINGS A WEAK SHORT WAVE ACROSS
WESTERN NC THIS EVENING. LLVL CONVERGENCE IS INCREASING OVER THE NC
MTNS AND FOOTHILLS AHEAD OF THE WAVE. THE MODELS ARE SPLIT ON
HOW FAR SOUTHEAST THIS CONVECTION GETS. THE GFS KEEPS IT OVER THE
MTNS AND FOOTHILLS...WHILE THE RAP AND NAM PUSH IT INTO THE NRN
SUBURBS OF CHARLOTTE. WITH THE FINGER OF DRIER AIR PUSHING INTO THE
SRN PIEDMONT I/VE GONE WITH A FORECAST THAT KEEPS THE BEST
CONVECTIVE CHANCES OVER THE MTNS AND FOOTHILLS WITH LOWER POPS ALONG
AND SOUTH OF I-85 AND BACK ACROSS THE SW NC MTNS. THIS IS NOT TO SAY
THAT STORMS WON/T PUSH INTO CHARLOTTE LATER THIS EVENING AS THE
ATMOSPHERE IS NOT CAPPED AND IS MODERATELY UNSTABLE. HOWEVER...THIS
DOES NOT LOOK LIKE THE MOST PROBABLE SOLUTION ATTM.
PATCHY DENSE VALLEY FOG IS EXPECTED OVER THE MTNS TONIGHT. ACROSS
THE FOOTHILLS AND PIEDMONT CONSIDERABLY LESS LOW CLOUD COVER IS
ANTICIPATED OWNING TO A MORE WESTERLY COMPONENT TO THE LLVL WIND
FIELD.
A SHORT WAVE CURRENTLY OVER CENTRAL MISSOURI IS EXPECTED TO CROSS
THE FORECAST AREA DURING THE AFTERNOON HOURS ON THURSDAY. THE DEEP
LAYER RH IS CONSIDERABLY HIGHER ON THU THAN TODAY ALONG AND AHEAD OF
THIS WAVE. BY 21 UTC THE FEATURE IS EXPECTED TO BE OVER THE I-77
CORRIDOR AND IT WILL MOVE EAT OF CHARLOTTE BY THE EARLY EVENING. THE
NAM AND GFS BOTH DEVELOP PCPN BY LATE MORNING AHEAD OF THE SHORT
WAVE. THE NAM HAS PCPN ENDING WITH WEAKLY DIVERGENT LLVL FLOW OVER
MOST OF THE FA DEVELOPING BETWEEN 21-00 UTC. THE WAY IT APPEARS
NOW...A BAND OF SHRA AND A FEW TSTMS WILL DEVELOP DEVELOP OVER THE
FOOTHILLS BY LATE MORNING...OR THEY MAY MOVE INTO THE MTNS AS A
REMNANT OF A WEAKENING MCS. THE CONVECTION WILL MOVE ACROSS THE REST
OF THE FOOTHILLS FROM EARLY TO MID AFTN AND EXIT TO THE EAST BY 6 OR
7 PM. THE SHEAR IS WEAK AND CONVECTION ISN/T EXPECTED TO BE HIGHLY
ORGANIZED AND MOST OF THE STORMS SHOULD BE SUB-SEVERE. THIS IS
GENERALLY SUPPORTED BY THE 12 UTC 4KM SPC WRF AS WELL. FOR NOW I/LL
CAP POPS ARE 40 PERCENT...WITH POPS FALLING OFF QUICKLY TOWARD
SUNSET.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 2 PM EDT WEDNESDAY...THE CONSENSUS OF THE MODEL GUIDANCE
MAINTAINS THAT THE PLUME OF DEEPER MOISTURE WILL HAVE SHIFTED
EASTWARD TO THE COASTAL PLAIN. IN THE WAKE OF A WEAK UPPER WAVE...
THE ENVIRONMENT SHOULD BE LESS FAVORABLE FOR DEEP CONVECTION. THE
CHANCE FOR SHOWERS AND STORMS SHOULD DROP IN THE EARLY EVENING AS
THE FORCING AND MOISTURE MOVE OFF TO THE EAST...TO THE POINT WHERE
THE FCST IS DRY EAST OF THE MTNS FROM 03Z ONWARD. THERE COULD BE A
FEW LINGERING SHOWERS OVER THE MTNS UNTIL LATE EVENING.
FRIDAY LOOKS LIKE A RELATIVELY QUIET TRANSITION DAY WHILE WE WAIT
FOR THE FORCING AND MOISTURE TO RELOAD. A STRONG SHORT WAVE OVER THE
UPPER MS VALLEY WILL DIG AN UPPER TROF DOWN OVER THE UPPER MIDWEST
AND GREAT LAKES THROUGH THE DAY...WHICH WILL GRADUALLY TURN THE FLOW
ALOFT MORE SW. UPPER FORCING WILL BE MINIMAL. THERE SHOULD BE ENOUGH
LOW LEVEL MOISTURE AND BUOYANCY TO SUPPORT SCATTERED SHOWERS AND
STORMS DEVELOPING OVER THE HIGHER TERRAIN WITH DIFFERENTIAL
HEATING...WITH SOME OF THE STORMS MOVING OUT OVER THE FOOTHILLS AND
PIEDMONT IN THE AFTERNOON AND EARLY EVENING. THE STORMS EAST OF THE
BLUE RIDGE WILL DIE OFF WITH SUNSET...BUT WILL KEEP THE CHANCE OF
PRECIP GOING OVERNIGHT ON THE W SIDE OF THE MTNS IN CASE SOME
ACTIVITY MOVES IN FROM THE WEST AHEAD OF THE NEXT FRONT.
THE UPPER TROF CONTINUES TO DIG OVER THE MIDWEST/OH VALLEY ON
SATURDAY AS THE WAVE DROPS SOUTHEASTWARD. DEEP MOISTURE MOVES IN
AHEAD OF THE WAVE TO BE ACTED UPON BY IMPROVED UPPER FORCING AS WE
WORK THROUGH THE DAY. THE OPERATIONAL RUNS FROM ALL THREE MODELS ARE
IN FAIRLY GOOD AGREEMENT WITH THE TIMING OF THE MAIN VORT AXIS
REACHING THE GREAT VALLEY LATE IN THE DAY. THE NEW GFS SWEEPS THE
UPPER TROF AXIS ACROSS THE WESTERN CAROLINAS OVERNIGHT WHILE THE 00Z
RUN PUSHES IT THROUGH SUNDAY MORNING. EITHER WAY...BOTH MODELS
SUGGEST AN EARLIER TIMING OF THE MAIN FRONTAL PRECIP BAND. WILL
LIMIT THE PRECIP TO THE CHANCE RANGE FOR THE TIME BEING BUT WILL
PROBABLY NEED A LIKELY POP FOR AT LEAST THE MTNS...BUT IT IS A
MATTER OF WHICH PERIOD TO FOCUS ON...SATURDAY AFTERNOON OR SATURDAY
NIGHT. WILL NOT RULE OUT SOME SEVERE STORMS IF THE FRONT WILL MOVE
THROUGH EARLY ENOUGH. AT THIS POINT...THINK MOST OF THE PRECIP WILL
HAVE MOVED EAST OF THE FCST AREA BY SUNRISE ON SUNDAY...WHICH AGREES
WITH THE HPC POSITION OF THE MAIN FRONT ON THE COAST AT THAT TIME.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 1130 AM EDT WEDNESDAY...AFTER DEALING WITH A SEMI-TROPICAL AIR
MASS FOR THE LAST TWO WEEKS...IT APPEARS AS THOUGH WE ARE IN FOR A
PERIOD OF SPECTACULAR EARLY AUTUMN-LIKE WEATHER EARLY NEXT WEEK. BUT
FIRST...WE HAVE TO GET A FRONT THROUGH THE CAROLINAS EARLY ON
SUNDAY. THE GFS MOVES THE MAIN SHORT WAVE LOBE ACROSS THE WESTERN
CAROLINAS EARLY SUNDAY MORNING WHILE THE ECMWF HAS THIS FEATURE
CROSSING SUNDAY AFTERNOON. THE TIMING IS FASTER THAN PREVIOUSLY
INDICATED...WITH THE MAIN SFC FRONT POTENTIALLY MOVING ACROSS THE
AREA SATURDAY NIGHT. WILL BACK OFF TO A SLIGHT CHANCE ACROSS THE
REGION ON SUNDAY AS A FEW SHOWERS COULD BE TRIGGERED BY A SECONDARY
FRONT. EITHER WAY...THERE IS A STRONG INDICATION THAT THE PRECIP
WILL BE LONG GONE BY SUNSET SUNDAY...SO THE PRECIP CHANCES ARE
ELIMINATED ALTOGETHER AFTER 00Z MONDAY.
THE UPPER TROF AXIS WILL REACH THE EASTERN SEABOARD BY MONDAY
MORNING AND MOVE SLOWLY OFFSHORE THROUGH MIDWEEK...WHILE AN UPPER
ANTICYCLONE REMAINS PARKED OVER THE SRN PLAINS. THE RESULTING UPPER
RIDGE TO OUR NW WILL BRING DRY HIGH PRESSURE BUILDING IN SUNDAY
NIGHT AND MONDAY. ONCE ESTABLISHED...THIS SURFACE HIGH WILL DOMINATE
OUR WEATHER AS IT MOVES SLOWLY PAST TO THE NORTH THROUGH WEDNESDAY.
THIS SHOULD BRING MOSTLY CLEAR SKY...DRY AIR...HIGH TEMPS IN THE
MID/UPPER 70S AND LOW TEMPS IN THE MID/UPPER 50S. THUS...MONDAY AND
TUESDAY WILL FEEL MORE LIKE LATE SEPTEMBER OR EARLY OCTOBER. THE AIR
MASS SHOULD START TO MODIFY A BIT BY WEDNESDAY.
&&
.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
AT KCLT...THE BULK OF THE TSTM ACTIVITY IS EXPECTED TO DEVELOP OVER
THE FOOTHILLS AND STAY 30 TO 50 MILES NORTHWEST OF THE AIRFIELD THIS
AFTERNOON AND EVENING. HOWEVER...THERE IS A LINE OF TCU BACK ACROSS
THE UPSTATE AND INTO THE SRN NC PIEDMONT THAT HAS BEEN PRODUCING
OCCASIONAL LIGHT SHRA. ATTM I HAVE REPLACED TEMPO THUNDER WITH TEMPO
SHRA IN THE TAF. IF STORMS DEVELOP FROM THE LINE OF TOWERS OVER THE
UPSTATE WE SHOULD STILL HAVE A COUPLE OF HOURS OF LEAD TIME BEFORE
THE STORMS AFFECT THE AIRFIELD. THE MODELS BRING SOME MID LEVEL
MOISTURE INTO THE REGION TONIGHT. THE LLVL FLOW ALSO VEERS TO THE
WEST. IF WE DON/T SEE ANY PCPN THIS EVENING...I THINK THE TWO
FACTORS ABOVE SHOULD KEEP STRATUS FROM DEVELOPING OVER THE REGION
TONIGHT.
ELSEWHERE...OVER THE UPSTATE ONLY ISOLATED SHRA ARE EXPECTED THE
REST OF THE AFTN. THERE IS A SMALL CHANCE THAT THE SHRA WILL BUILD
INTO TSTMS...BUT FOR NOW I THINK THE RISK IS TOO SMALL TO INCLUDE
THUNDER IN THE TAFS. WINDS WILL BE OUT OF THE SOUTHWEST AT SPEEDS
UNDER 10 KTS. THERE WILL BE A BETTER CHANCE OF SHRA/TSTMS AT KAVL
AND KHKY CLOSER TO A WEAK SFC TROUGH OF LOW PRESSURE. THE FOG AND
STRATUS FORECAST IS TRICKIER TONIGHT THAN IT HAS BEEN THE PAST
COUPLE DAYS. WINDS WILL VEER TO THE WEST OVERNIGHT. STRATUS MAY
APPROACH THE UPSTATE FROM THE SOUTHWEST LATE...BUT OVERALL I ONLY
SEE SOME MVFR FOG DEVELOPING. THE EXCEPTION WILL BE THE FRENCH BROAD
VALLEY WHERE VALLEY FOG AND STRATUS WILL BE MORE
WIDESPREAD...PARTICULARLY IF THERE IS A PERIOD OF CLEARING
OVERNIGHT. SHRA MAY SPREAD ACROSS THE MTNS AND FOOTHILLS SHORTLY
AFTER SUNRISE AHEAD OF A COLD FRONT THOUGH I/VE TONED THIS BACK IN
THE TAFS.
OUTLOOK...GRADUAL DRYING FROM THE WEST IS EXPECTED ON
THURSDAY...WITH DEEPER DRYING ON FRIDAY. A COLD FRONT WILL APPROACH
THE REGION FROM THE NORTHWEST ON SATURDAY AND MOVE EAST OF THE AREA
ON SUNDAY.
AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE
PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE
CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)...
WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.
&&
$$
SYNOPSIS...PM
NEAR TERM...MCAVOY
SHORT TERM...PM
LONG TERM...PM
AVIATION...MCAVOY
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
330 PM CDT WED SEP 5 2012
.SHORT TERM...TONIGHT THROUGH SATURDAY
329 PM CDT WED SEP 5 2012
FOCUS THIS FORECAST PERIOD WAS ON THE NEXT WEATHER SYSTEM COMING
INTO THE AREA THURSDAY NIGHT AND FRIDAY. CHANCES ARE INCREASING
FOR A SHOWER PRODUCER.
CURRENT FRONTAL POSITION TOUGH TO DISCERN RIGHT NOW...BUT MAYBE
THE MORE IMPORTANT ELEMENT IS WHERE THE CONVERGENCE AND
INSTABILITY IS. SURFACE MOISTURE CONVERGENCE CURRENTLY LIES ACROSS
THE SOUTHERNMOST FORECAST AREA PER SPC 19Z ANALYSIS. MLCAPE IS UP
TO 1500 J/KG THERE WITH CIN ABOUT 50 J/KG. THERE IS SOME WEAKER
CONVERGENCE ACROSS NERN IA ALONG ANOTHER WEAK WIND SHIFT FROM WEST
TO N-NW.
THE NEXT FEW HOURS HOLD A CHANCE FOR ISOLATED TSRA ACROSS NERN IA
AND SWRN WI BUT THIS CHANCE SHOULD SHIFT SOUTHEAST BY EVENING.
CURRENTLY DO NOT HAVE A TSRA CHANCE IN THE FORECAST THIS AFTERNOON
OR EVENING.
12Z 250 MB RAOB INFORMATION SHOWING A NICE HEIGHT FALL/RISE/FALL
SIGNAL OVERHEAD AND UPSTREAM INTO WRN ALBERTA...WITH THE
WESTERNMOST FALL OF OVER 100M/12HR ASSOCIATED WITH THE FRIDAY
SHORTWAVE TROUGH SHIFTING SOUTHEAST. A NICE WARM POOL OF AIR SEEN
WITH THAT SHORTWAVE TROUGH OVER ALBERTA/BRITISH COLUMBIA THERE
TOO..AND 100KT JET CORE...WITH LATEST RUC ANALYSIS SHOWING THE
TROPOPAUSE FOLD DOWN TO 500MB OVER CENTRAL BC. SHORTWAVE RIDGE TO
BUILD IN FOR TONIGHT/THURSDAY IS CENTERED NEAR KGGW WITH 80M/12HR
HEIGHT RISES AT 250 MB.
RIDGE BUILDING WILL CONTINUE OVERNIGHT WITH ENOUGH 0-2KM AGL FLOW
/GREATER THAN 10KTS/ TO KEEP MISSISSIPPI RIVER VALLEY FOG OUT OF
THE PICTURE. HOWEVER...HAVE KEPT THE WI RIVER VALLEY FOG IN FOR
THU MORNING AS MORE ORTHOGONAL NW FLOW WILL ALLOW FOR DECOUPLING
IN THE BOUNDARY LAYER. PLUS...DEWPOINTS WILL BE HIGHEST IN THAT
AREA OVERNIGHT...HAVE SLOWED THE DRIER AIR ADVECTION.
ALBERTA/BC SHORTWAVE TROUGH TO BRING FALL-LIKE DYNAMICS TO THE AREA
THURSDAY NIGHT AND INTO FRIDAY. PRETTY GOOD CONSISTENCY IN THE
LARGER SCALE FORCING PRESENTED IN THE 05.12Z NAM/GFS THIS MORNING
AND BECAUSE OF THIS...HAVE RAISED RAIN CHANCES LATE THURSDAY NIGHT
INTO FRIDAY. THE SHORTWAVE ROUGH ENERGY SPLITS AS IT HEADS
SOUTHEAST WITH A PORTION MOVING IN FROM THE DAKOTAS AND THE SECOND
COMING IN FROM THE SOUTHWEST. THESE EACH HAVE A SMALL JET CORE
ASSOCIATED WITH THEM AND BY LATER THU NIGHT-FRIDAY...IT APPEARS THEY
INTERACT IN A COUPLED JET SCENARIO OVER THE AREA FOR GOOD DIVERGENCE
ALOFT. A STRONG BAROCLINIC ZONE IN THE 700-850MB LAYER WITH THE
INITIAL SHORTWAVE TROUGH WILL ALSO CREATE A W-E RAIN BAND WITH ITS
FORCING IN FRONTOGENESIS FROM CENTRAL MN-NRN WI...WHICH SLOWLY
SHIFTS INTO THE NWRN FORECAST AREA BY FRIDAY MORNING. THIS IS
SOMEWHAT IN CONCERT WITH 500-300MB QVECTOR CONVERGENCE.
MEANWHILE...BACK AT THE RANCH...THETA-E CONVERGENCE IN THE LOW-
LEVELS WILL ALSO START INCREASING IN THE WRN AND NRN FORECAST BY
12Z FRIDAY. THEN...QG FORCING INCREASES AS SECOND SHORTWAVE TROUGH
ENERGY PIECE SHIFTS ACROSS THE SOUTHERN FORECAST AREA. 05.12Z
ECMWF HAS THESE COMPONENTS...JUST FURTHER NORTH AND
SOUTH...SPLITTING AROUND THE FORECAST AREA.
05.09Z SREF DATA SUGGESTS ANY CAPE OVER 500 J/KG SHOULD REMAIN SOUTH
OF THE FORECAST AREA WITH DEWPOINTS STRUGGLING TO REACH MIDDLE 50S.
HOWEVER...WITH STEEPER LAPSE RATES IN THE MID-LEVELS AND STRONGER
FRONTOGENESIS...COULD SEE SOME THUNDER THU NIGHT UNTIL IT IS USED
UP.
OVERALL...THE SIGNALS ARE BEST IN THE NRN AND SRN FORECAST
AREA...BUT LARGE ENOUGH SIGNALS EXIST TO MOVE TOWARD A LIGHT RAIN
SHOWER SOLUTION FOR LATE THURSDAY NIGHT AND INTO FRIDAY. AMOUNTS MAY NOT
BE LARGE WITH LIMITED INSTABILITY IN THE FORECAST AREA...AROUND A
QUARTER OF AN INCH TOTAL. RAIN SHOULD CLEAR QUICKLY EAST LATER ON
FRIDAY. CURRENTLY THE FORECAST TEMPERATURES HAVE A 10F DIURNAL
RANGE FRIDAY...AND IF IT SHOWERS ALL DAY...IT WOULD LIKELY BE
ABOUT 5F. CONFIDENCE IS INCREASING ON THE RAIN EVENT...BUT NOT
HIGH ENOUGH TO CUT HIGHS FRIDAY MORE. THIS WILL BE NEEDED IF WE
INCREASE THE RAIN CHANCES MORE IN COMING FORECASTS.
NOTE...THE NCEP GFS MODEL WAS CHANGED TODAY AT 12Z TO TRY AND
SOLVE THE COLD/MOIST BIAS IN THE LOWEST 3KM AGL THAT HAS BEEN
EVIDENT SINCE LAST YEAR. IT APPEARED BETTER WITH ITS
INITIALIZATION IN THE LOW LEVELS.
.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY
329 PM CDT WED SEP 5 2012
WITH NORTHWEST FLOW OVER THE AREA FOR THE WEEKEND...THERE IS SOME
SIGNAL FOR A SHORTWAVE TROUGH TO SHIFT THROUGH THE GREAT LAKES
SATURDAY NIGHT. AT THIS TIME THE 05.00Z ECMWF AND 05.12
GEM/GFS/ECMWF REMAIN CONSISTENT IN SHOWERS OVERNIGHT IN EASTERN
WISCONSIN. THERE IS A VERY DEEP TROPOSPHERIC QG FORCING SIGNAL
MOVING THROUGH EASTERN WI PER THE 05.12Z ECMWF. THUS...HAVE ADDED
SOME SMALL SHOWER CHANCES TO CENTRAL WI AREAS. IF THIS SIGNAL
CONTINUES...MORE CLOUD AND HIGHER RAIN CHANCES WILL BE NEEDED. IT
LOOKS LIKE A FAST MOVER TO LIMIT THE IMPACT ON THE WEEKEND
WEATHER.
RIDGE BUILDING THEN IN CONTROL OF WEATHER SUN-TUE WITH
TEMPERATURES WARMING. THERE ARE SOME SIGNALS THAT TUESDAY COULD BE
IN A PREFRONTAL SOUTHWESTERLY FLOW WITH 90F POSSIBLE. HAVE BUMPED
HIGHS ABOUT 3F AND THE ONLY THING HOLDING OFF THE FORECAST OF
WARMER HIGHS IS THE TIMING OF A STRONG FRONT AT DAY 6 CAN GET
TRICKY.
&&
.AVIATION...THROUGH 18Z THURSDAY
1222 PM CDT WED SEP 5 2012
VFR CONDITIONS EXPECTED AT KRST/KLSE THROUGH THE PERIOD AND MAIN
FORECAST CONCERN IS WHETHER RIVER VALLEY FOG WILL DEVELOP AT KLSE.
LATEST SURFACE ANALYSIS DEPICTS COLD FRONT DRAPED FROM NORTHEAST
WISCONSIN DOWN INTO NORTHERN IOWA. FOR THIS AFTERNOON...MIXING
SHOULD CONTINUE UNTIL AROUND 01Z AND HAVE CONTINUED GUSTS UP TO 18
KTS AT BOTH TAF SITES. REGARDING VALLEY FOG OVERNIGHT...WINDS IN
THE 850 TO 925 MB LAYER ARE EXPECTED TO BE IN THE 10-15 KT RANGE.
COMBINED WITH PLENTY OF DAYTIME MIXING...AND 03Z T/TD SPREADS
BETWEEN 12-15F...ALL OF THESE FACTORS SHOULD PRECLUDE DENSE FOG
DEVELOPMENT. THOUGH BY 12Z THE GRADIENT DOES RELAX A BIT AS THE
SURFACE HIGH BUILDS IN...SO IF THERE WERE TO BE ANY FOG CONCERNS IT
WOULD BE SHORT LIVED...PATCHY AND IN THE 13-14Z TIME FRAME. FOR
THURSDAY...NO CONCERNS WITH SURFACE HIGH PRESSURE IN PLACE...AMPLE
SUNSHINE AND LIGHT WINDS.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
329 PM CDT WED SEP 5 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...BAUMGARDT
LONG TERM...BAUMGARDT
AVIATION...ZT