Forecast Discussions mentioning any of
"HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 12/31/12
AREA FORECAST DISCUSSION
NWS TUCSON AZ
849 PM MST SUN DEC 30 2012
.SYNOPSIS...THERE IS A GOOD CHANCE OF VALLEY RAIN AND MOUNTAIN SNOW
THIS EVENING INTO MONDAY WITH SNOW ACCUMULATIONS AS LOW AS 3500
FEET. DRY CONDITIONS WILL THEN PREVAIL NEW YEARS DAY THROUGH
SATURDAY WITH A GRADUAL WARMING TREND.
&&
.DISCUSSION...SHOWERS CONTINUE TO SPREAD EAST NORTHEAST ACROSS
SOUTHERN ARIZONA. THE SNOW LEVELS CONTINUE TO FALL. RECENT REPORTS
FROM ORACLE...ROUGHLY 4 KFT...SUGGESTED A LIGHT DUSTING OF SNOW ON
THE GROUND AND ROADS. ALSO...WE HAD REPORTS OF SNOW NEAR NOGALES
WHICH IS AORUND 3700 FEET. SO THE FORECAST APPEARS TO BE ON TRACK
WITH THE SNOW LEVELS DROPPING TO AROUNG 3500 FEET OVERNIGHT. ONE
HOUR LIQUID ACCUMULATION VALUES BASED ON THE TUCSON RADAR ARE LESS
THAN A TENTH OF AN INCH PER HOUR. SO THIS APPEARS TO BE A STEADY
LIGHT RAIN OR SNOW EVENT.
A SECOND BATCH OF STORMS ARE APPROACHING SOUTHERN ARIZONA FROM
CALIFORNIA. THESE STORMS HAVE A LITTLE MORE GUTS TO THEM.
REFLECTIVITY VALUES UP NEAR 50 DBZ WITH A FEW LIGHTNING STRIKES
OBSERVED OVER THE GULF OF CALIFORNIA. THESE STORMS ARE MORE SPOTTY
THOUGH. THE UOFA WRF MODEL SUGGESTS THIS WAVE OF STORMS WILL STILL
CONGEAL AND MOVE ACROSS SOUTHEAST ARIZONA THUS PROMPTING THE
CONITNUED THREAT OF SNOW IN THE HIGHER TERRAIN. THE WINTER ADVISORY
WILL CONTINUE AS SCHEDULED.
&&
.AVIATION...CLOUD LOWERING TO GENERALLY 4-7K FT AGL THIS EVENING AND
CONTINUING THRU MONDAY MORNING. WIDESPREAD -SHRA AND HIGHER TERRAIN
-SHSN THIS EVENING THRU MONDAY MORNING. AREAS OF MVFR CIGS TONIGHT
WITH HIGHER TERRAIN OBSCURATIONS. SCT -SHRA/MTN -SHSN MAINLY EAST OF
KTUS MONDAY AFTERNOON. CLOUDS DECREASING WEST OF KTUS MONDAY
AFTERNOON WITH BKN-OVC CLOUDS MOSTLY AROUND 4-7K FT AGL EAST OF
KTUS. AREAS OF S-SW SURFACE WIND THIS EVENING 10-20 KTS WITH GUSTS
TO 30 KTS EAST AND SOUTH OF KTUS. SURFACE WIND AFTER 31/06Z EASING
TO LESS THAN 10 KTS THRU MONDAY AFTERNOON. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.
&&
.FIRE WEATHER...RAIN AND MOUNTAIN SNOW SHOWERS WILL MOVE ACROSS THE
AREA THIS EVENING THROUGH EARLY MONDAY WITH A FEW SCATTERED SHOWERS
MONDAY AFTERNOON. THE SOUTH TO SOUTHWEST BREEZE ACROSS PORTIONS OF
THE AREA WILL EASE OVERNIGHT. THEN DRY CONDITIONS WILL PREVAIL FROM
TUESDAY THROUGH NEXT WEEKEND WITH A VERY GRADUAL WARMING TREND.
WINDS WILL BE LIGHT THROUGH THE PERIOD AND PREDOMINATELY FROM AN
EASTERLY DIRECTION.
&&
.PREV DISCUSSION...UPPER TROUGH CONTINUES TO DEEPEN OVER THE SWRN
CONUS THIS AFTERNOON. UPPER LOW IS PROGGED TO MOVE EWD ACROSS NRN
ARIZONA TONIGHT...THEN SYSTEM WILL FILL AND MOVE RAPIDLY EWD INTO
THE CENTRAL CONUS PLAINS BY MON EVENING. 30/12Z UNIV OF ARIZONA
WRF-NAM AND WRF-GFS AS WELL AS THE 30/15Z RUC HRRR WERE VERY SIMILAR
WITH DEPICTING TWO PERIODS OF PRECIP ACROSS SE AZ TONIGHT. THE FIRST
PERIOD OF PRECIP IS FORECAST TO OCCUR BASICALLY FROM 6-10 PM MST OR
SO. MORE SHOWERS ARE PROGGED TO MOVE INTO WRN/CENTRAL PIMA COUNTY
AROUND MIDNIGHT...THEN WIDESPREAD VALLEY RAIN/MOUNTAIN SNOW TO OCCUR
LATE TONIGHT INTO MID-MORNING MON.
BASED ON THESE SOLUTIONS AS WELL AS THE 30/12Z NAM/GFS/ECMWF...HAVE
MAINTAINED THE INHERITED WINTER WEATHER ADVISORY FOR AZZ503-506>509
FROM MIDNIGHT TONIGHT TO 9 AM MST MONDAY ABOVE 3500 FEET. STILL
APPEARS THAT SNOW LEVELS LATE TONIGHT INTO MON MORNING WILL RANGE
FROM 3500-4000 FEET. PRECIP MON AFTERNOON TO BE CONFINED MOSTLY TO
GREENLEE...GRAHAM...AND COCHISE COUNTIES EAST OF TUCSON. DRY
CONDITIONS TO OCCUR MON NIGHT EXCEPT FOR A SLIGHT CHANCE OF SNOW
SHOWERS ACROSS THE WHITE MOUNTAINS.
STORM TOTAL LIQUID AMOUNTS ARE EXPECTED TO RANGE FROM ABOUT ONE
TENTH OF AN INCH TO NEARLY ONE THIRD OF AN INCH. STORM TOTAL SNOW
ACCUMULATIONS ABOVE 5000 FEET ARE FORECAST TO RANGE FROM 2-5
INCHES...OR JUST BELOW SNOW ADVISORY CRITERIA. HOWEVER...SNOW
ACCUMULATIONS OF 1 TO 2 INCHES BETWEEN 3500-5000 FEET JUSTIFY THE
WINTER WEATHER ADVISORY FOR THE LOWER ELEVATIONS OF GRAHAM/SRN
GREENLEE/COCHISE/ERN SANTA CRUZ/ERN PINAL COUNTIES.
DRIER NWLY/WLY FLOW ALOFT TUE...THEN GFS/ECMWF WERE SIMILAR WITH
MOVING THE NEXT UPPER LOW SEWD ACROSS NRN BAJA CALIFORNIA TUE NIGHT
AND EARLY WED. AT THIS TIME APPEARS THAT DRY CONDITIONS WILL OCCUR
TUE NIGHT-WED AS BULK OF MOISTURE WILL BE ABOVE 500 MB. UPPER RIDGE
TO THEN PREVAIL OVER THE WRN CONUS THUR-SAT. REMAINING DRY NEXT SUN
AS THE NEXT UPPER LOW IS PROGGED TO BE WELL WEST OF THE AREA.
MARKEDLY COLDER MON WITH HIGH TEMPS TO BE NEARLY 15 DEGS F OR SO
BELOW NORMAL. ALTHOUGH FAIRLY WIDESPREAD FREEZING TEMPS ARE FORECAST
TO OCCUR MON NIGHT...A HARD FREEZE APPEARS TO BE UNLIKELY. A VERY
GRADUAL WARMING TREND IS ON TAP TUE-SAT ALTHOUGH DAYTIME TEMPS ARE
EXPECTED TO REMAIN BELOW NORMAL.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM MST MONDAY
FOR AZZ503-506>509 BETWEEN 3500 AND 5000 FEET.
&&
$$
VISIT US ON FACEBOOK...TWITTER...YOUTUBE...AND AT WEATHER.GOV/TUCSON
DISCUSSION...BF
AVIATION/FIRE WEATHER...CERNIGLIA
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
900 AM PST SAT DEC 29 2012
.SYNOPSIS...
INCREASING CLOUDS AND COOLER WITH LIGHT RAIN AND MOUNTAIN SNOW LIKELY
OVER AND WEST OF THE MOUNTAINS TODAY THROUGH SUNDAY AS A COLD
FRONT MOVES THROUGH THE REGION. ISOLATED THUNDERSTORMS ARE ALSO
POSSIBLE THROUGH SUNDAY AFTERNOON. GUSTY WEST WINDS WILL DEVELOP
OVER THE MOUNTAINS AND DESERTS FOR LATE SUNDAY. WEAK TO MODERATE
OFFSHORE FLOW...FAIR WEATHER AND GRADUAL WARMING TUESDAY THROUGH
MOST OF NEXT WEEK.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
THIS MORNING...SATELLITE IMAGERY SHOWS A LOW PRESSURE SYSTEM
MOVING SOUTHEAST ALONG THE CENTRAL CALIFORNIA COAST. RADAR SHOWS
MOSTLY LIGHT SHOWERS CURRENTLY MOVING THROUGH LOS ANGELES AND
NORTHERN ORANGE COUNTIES...WITH EMBEDDED ISOLATED TSTMS OVER L.A.
COUNTY. POST-FRONTAL CONVECTION CONTINUE TO MOVE INLAND FARTHER TO
THE NORTH. TIMING OF THE PRECIP FOR EXTREME SOUTHWESTERN CA
REMAINS ON TRACK...WITH SHOWERS MOVING INTO SOUTHWEST SAN
BERNARDINO COUNTY LATER THIS MORNING AND SPREADING SOUTH AND EAST
THROUGH THE AFTERNOON. THE BULK OF THE PRECIPITATION IS EXPECTED
TO FALL LATE THIS AFTERNOON AND EVENING AS THE FRONT MOVES
THROUGH...TAPERING OFF TO SHOWERS TONIGHT. SHOWERS MAY LINGER
SUNDAY INTO EARLY MONDAY AS A SECOND SHORTWAVE TROUGH MOVES DOWN
THE BACK SIDE OF THE TROUGH AND OVER SOUTHERN CA. COLD AIR ALOFT
AND MARGINALLY UNSTABLE CONDITIONS COULD CONTINUE ISOLATED
THUNDERSTORMS DURING THE DAY SUNDAY AS WELL.
NUMERICAL MODELS ARE IN GENERALLY GOOD AGREEMENT ON THE TRACK AND
TIMING OF THIS SYSTEM BUT DIFFER SOMEWHAT IN THE DETAILS...WITH
THE GFS AND NAM MODELS HAVING THE DRIER SOLUTIONS. THE PRECIP
FORECAST IS BASED ON A BLEND OF THE ECM AND SREF. RAINFALL TOTALS
FOR THIS SYSTEM WILL RANGE FROM AROUND ONE TENTH TO ONE THIRD INCH
IN THE COASTS/VALLEYS AND ONE QUARTER TO ONE HALF INCH IN THE
MOUNTAINS. LOCALLY HIGHER AMOUNTS ARE POSSIBLE IN HEAVIER SHOWERS
AND THUNDERSTORMS. LITTLE TO NO RAINFALL IS EXPECTED IN THE
DESERTS. THE SNOW LEVEL IS AROUND 4500 FT THIS MORNING...AND IS
EXPECTED TO DROP TO AROUND 4000 FT TONIGHT. SNOWFALL TOTALS WILL
BE BETWEEN 1 TO 3 INCHES ABOVE 4500 FT...WITH ISOLATED AMOUNTS TO
UP TO 4 INCHES ON THE SOUTH SLOPES OF THE SAN BERNARDINO MTNS.
IN ADDITION TO PRECIPITATION...THIS SYSTEM WILL BRING WEST WINDS
WITH GUSTS UP TO 40 MPH IN THE MTNS AND DESERTS SUNDAY AFTERNOON
AND EVENING FOLLOWING FRONTAL PASSAGE. AS THE COLD AIR MOVES IN
FROM THE NORTHWEST...HIGH TEMPERATURES THIS WEEKEND WILL BE
ANYWHERE FROM 10 TO 20 DEGREES BELOW SEASONAL AVERAGES.
WEAK OFFSHORE FLOW WILL DEVELOP FOR MONDAY MORNING AS THE LOW
PRESSURE TROUGH MOVES EAST AND SURFACE HIGH PRESSURE MOVES INTO
THE GREAT BASIN. DESPITE THE OFFSHORE FLOW...COLD AIR MOVING IN
FROM THE NORTH WILL PREVENT MUCH WARMING FROM OCCURRING SO EXPECT
TEMPERATURES TO REMAIN BELOW SEASONAL AVERAGES. BEYOND
MONDAY...THERE IS QUITE A BIT OF UNCERTAINTY IN THE FORECAST AS
MODELS CONTINUE TO BE VERY INCONSISTENT WITH THE TRACK OF ANOTHER TROUGH
FOR TUE INTO WED. THE GFS AND EC HAVE TRENDED MUCH FURTHER WEST
WITH THIS TROUGH...BRINGING IT DOWN ALONG THE CA COAST. THIS
WOULD MEAN WEAKER UPPER SUPPORT FOR THE OFFSHORE WINDS TUESDAY AND
SLIGHTLY COOLER WEATHER. BOTH MODELS EVEN SHOW SOME RAIN OFF THE
COAST...THOUGH AT THIS TIME IT IS TOO FAR WEST TO IMPACT SOUTHERN
CA. STILL EXPECTING SOME INCREASE IN THE OFFSHORE WINDS LATE
TUESDAY INTO WED AS WINDS ALOFT TURN NORTHEAST AND SURFACE
GRADIENTS TIGHTEN. WEAK OFFSHORE WINDS AND GRADUAL WARMING WILL
CONTINUE INTO THE WEEKEND WITH TEMPS NEAR TO SLIGHTLY BELOW
NORMAL. MODELS ARE STILL HINTING AT ANOTHER LOW PRESSURE SYSTEM
FOR NEXT WEEKEND...THOUGH UNCERTAINTY IS HIGH AS THERE IS LITTLE
OR NO AGREEMENT AMONG THE MODELS AT TO WHERE THE LOW/TROUGH WILL
TRACK AND HOW STRONG IT WILL BE.
&&
.AVIATION...
291550Z...COASTAL TO MOUNTAINS AREA OF EXTREME SOUTHERN
CALIFORNIA...CLOUDS CONTINUE TO INCREASE ACROSS THE AREA AND A
FEW SHOWERS ARE BEGINNING TO SHOW UP ON RADAR AND IN OBS AT A FEW
AIRPORTS. STORM SYSTEM IS ON TRACK WITH FOCUS ON ECMWF...LOCAL
WRF AND RAP IN DECENT AGREEMENT WITH FRONTAL PASSAGE AND
SHOWERS...PER TAFS...IN THE KSNA 29/2000Z TO KSAN 30/0100Z.
CEILINGS AND WINDS NOT A MAJOR ISSUE WITH CEILINGS MAYBE TEMPO TO
015 MSL AND VSBY TO 3 MI WITH RA THE OBSCURATION. FORECAST
CONFIDENCE HIGH.
&&
.MARINE...
A HIGH SURF ADVISORY AND A SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS
WILL BEGIN THIS AFTERNOON AND CONTINUE SUNDAY. HAZARDOUS SEAS WILL
BE MAINLY SOUTH OF SAN CLEMENTE ISLAND. HIGHEST SURF WILL BE IN
SOUTHERN SAN DIEGO COUNTY. AN ISOLATED THUNDERSTORM IS POSSIBLE
TODAY AND EARLY SUNDAY. FORECAST CONFIDENCE MEDIUM TO HIGH...SURF
MIGHT BE MORE IMPRESSIVE THAN FORECAST IN NORTH SD AND ORANGE
COUNTIES.
ANOTHER LARGE SWELL ARRIVES NEW YEARS DAY AND CONTINUES INTO
THURSDAY. HIGH SURF ADVISORIES MAY BE NEEDED THEN.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...HIGH SURF ADVISORY FROM 2 PM THIS AFTERNOON TO 2 PM PST SUNDAY
FOR THE SAN DIEGO COUNTY COASTAL AREAS.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 2 PM THIS AFTERNOON
TO 2 PM PST SUNDAY FOR THE WATERS FROM SAN MATEO POINT TO
THE MEXICAN BORDER EXTENDING 30 TO 60 NM OUT INCLUDING SAN
CLEMENTE ISLAND.
&&
$$
PUBLIC...PG
AVIATION/MARINE...PIERCE
AREA FORECAST DISCUSSION
NWS DENVER/BOULDER CO
913 PM MST FRI DEC 28 2012
.UPDATE...
NO BIG CHANGES THIS EVENING FOR THE FORECAST. GUSTY WINDS OVER THE
HIGH MOUNTAIN PASSES OF THE FRONT RANGE MOUNTAINS ARE COMBINING
WITH COLD TEMPERATURES TO CREATE WIND CHILL READINGS OF AROUND 30
DEGREES BELOW ZERO. ADDED THESE TO THE GRIDS...THOUGH THESE
CONDITIONS ARE NOT EXPECTED TO LAST MUCH PAST MIDNIGHT AS THE
WINDS WILL BE DECREASING.
&&
.AVIATION...NO BIG CHANGES EXPECTED FOR THE ONGOING TAFS WITH VFR
CONDITIONS THROUGH SATURDAY. DRAINAGE WINDS STILL EXPECTED FOR
THE AIRPORTS TONIGHT WITH SOME WESTERLY GUSTS AT KBJC. ON
SATURDAY...MODELS CONTINUE TO HINT AT A WEAK CYCLONE DEVELOPING
AROUND OR NORTH OF THE DENVER AREA BY 18Z. THUS...LIGHT SOUTH TO
SOUTHEASTERLY WINDS SHOULD PREVAIL AT THE AREA AIRPORTS THROUGH
THE DAY... PERHAPS MORE EAST TO NORTHEAST AT KDEN DEPENDING ON
WHERE THE CYCLONE SETS UP. VFR TO CONTINUE WITH UNLIMITED
CEILINGS.
&&
.PREV DISCUSSION... /ISSUED 255 PM MST FRI DEC 28 2012/
SHORT TERM...LATEST WATER VAPOR AND IR LOOPS SUGGESTING A WEAK
SHORTWAVE CURRENTLY MOVING ACROSS AREA AS NOTED BY SOME CLOUD
ENHANCEMENT. HOWEVER...WEB CAMS SHOW THE LIGHT SNOW CONFINED TO
AREAS ALONG THE CONTINENTAL DIVIDE AS WELL AS ACROSS THE PARK
RANGE IN WESTERN JACKSON COUNTY. SOME GUSTY WINDS ACROSS THE
HIGHER MOUNTAINS AND OVER THE NORTHERN FOOTHILLS WITH A FEW GUSTS
AROUND 35 MPH. LATEST MODELS SHOW THE SHORTWAVE MOVING EAST OF THE
AREA DURING THE EVENING WITH THE FLOW ALOFT BECOMING MORE NORTH
NORTHWEST. CROSS SECTIONS INDICATE A DECREASE IN MOISTURE WITH
INCREASING SUBSIDENCE. SHOULD SEE MOUNTAIN SNOW COMING TO AN END
BY MIDNIGHT WITH CLEARING SKIES. WINDS TO REMAIN A BIT GUSTY INTO
THE EVENING...BEFORE DECREASING AROUND MIDNIGHT. CLEARING SKIES...
LIGHT WINDS AND SNOW COVER WILL ALLOW FOR THE DEVELOPMENT OF
INVERSIONS IN THE MOUNTAIN VALLEYS AS WELL AS LOW LYING AREAS
ACROSS THE PLAINS. THUS...SHOULD GET QUITE COLD IN THESE AREAS
OVERNIGHT WITH TEMPERATURES BELOW ZERO ESPECIALLY THE KREMMLING
AREA IN GRAND COUNTY. ON SATURDAY...UPPER LEVEL RIDGE BUILDS OVER
COLORADO WITH FLOW ALOFT BECOMING MORE WESTERLY. 7H TEMPERATURES
WARM ABOUT 6-8 DEGREES CELSIUS FROM TODAY`S READINGS. THUS SHOULD
SEE WARMER TEMPERATURES ACROSS MUCH OF THE AREA WITH MAINLY CLEAR
SKIES. HOWEVER...INVERSIONS WILL LIMIT THE WARMUP...ESPECIALLY IN
THE MOUNTAIN VALLEYS. TEMPERATURES ACROSS THE PLAINS TO BE MAINLY
IN THE 30S...WITH MID TO UPPER 20S IN THE GREELEY AREA. WINDS
ALOFT TO BE FAIRLY LIGHT...WITH SOME GUSTY WINDS POSSIBLE ACROSS
THE HIGHER RIDGES.
LONG TERM...SOUTHWEST FLOW ALOFT WILL PREVAIL SATURDAY NIGHT AND
SUNDAY AS AN UPPER LEVEL TROUGH MOVES ONTO THE WEST COAST. THE
TROUGH WILL CONTINUE TO DIG SOUTHEAST AND BE CENTERED OVER THE
SOUTHWESTERN STATES SUNDAY NIGHT. EXPECT A COLD NIGHT IN THE
MOUNTAIN VALLEYS SATURDAY NIGHT UNDER MOSTLY CLEAR SKIES. LOWS
SHOULD DROP BELOW ZERO IN THE MOUNTAIN VALLEYS. CLOUDS WILL INCREASE
DURING THE DAY SUNDAY AS MID AND HIGH LEVEL MOISTURE INCREASE WITH
THE APPROACH OF THE UPPER LEVEL TROUGH.
STILL A LOT OF DIFFERENCES AMONG THE MODELS ON THE TRACK OF THE
UPPER LEVEL TROUGH. THE LATEST ECMWF AND NAM ARE STARTING TO NUDGE
THE TRACK MORE NORTHERLY. MEANWHILE THE GFS CONTINUES TO FAVOR A
SOUTHERLY TRACK ACROSS THE SOUTHERN ROCKIES. BECAUSE OF THIS
NORTHERLY SHIFT...WILL INCREASE POPS ACROSS THE AREA FOR SUNDAY
NIGHT AND MONDAY. WILL HAVE LIKELY POPS FOR THE MOUNTAINS NEAR AND
SOUTH OF I-70. EVEN THE SOUTHERLY TRACK OF GFS SHOWS SNOW FOR THE
CENTRAL AND SOUTHERN MOUNTAINS OF COLORADO. WILL HAVE CHANCE TO
SLIGHT CHANCE ELSEWHERE. AS THIS SYSTEM NEARS...LATER SHIFTS CAN
TREND UP OR DOWN AS THE TRACK OF THE TROUGH BECOMES MORE CLEAR.
EXPECT HIGH TEMPERATURES TO BE COOL MONDAY AND TUESDAY UNDERNEATH
THIS SYSTEM.
ONCE THE TROUGH EXITS THE REGION...QUIET WEATHER WILL PREVAIL. EVEN
THOUGH MODELS ARE SHOWING DIFFERENT UPPER LEVEL PATTERN...ALL OF THE
DIFFERENT SOLUTIONS WOULD RESULT IN COOL AND DRY CONDITIONS.
THEREFORE WILL CONTINUE WITH THE COOL AND DRY CONDITIONS CURRENTLY
IN THE FORECAST.
AVIATION...WINDS HAVE TRENDED TOWARD LIGHT EASTERLY ACROSS THE
AREA AIRPORTS. LATEST RUC AND HRRR INDICATING WINDS TO BECOME
NORTHWEST BY 00Z...THEN SOUTHWESTERLY BY 03Z AS DRAINAGE FLOW
DEVELOPS. THIS TREND SEEMS REASONABLE THOUGH THE DIRECTION WILL BE
MORE WESTERLY AT BJC. ON SATURDAY...MODELS HINT AT A WEAK CYCLONE
DEVELOPING NORTH OF THE DENVER AREA BY 18Z. THUS...LIGHT SOUTHERLY
WINDS SHOULD PREVAIL AT THE AREA AIRPORTS THROUGH THE DAY...
PERHAPS MORE SOUTHEAST AT DEN. VFR TO CONTINUE WITH UNLIMITED
CEILINGS.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...D-L
LONG TERM....MEIER
AVIATION...KRIEDERMAN
AREA FORECAST DISCUSSION
NWS TALLAHASSEE FL
1100 AM EST Sat Dec 29 2012
.NEAR TERM [Rest of Today]...
Updated at: 1100 am EST
Not many changes were made to the forecast today. Cloud cover was
increased slightly, especially in the morning, as stratus has been
slow to break up so far. Temperatures are trending fairly close to a
blend of the 11z RAP and 12z NAM, so that is what the hourly
temperature forecast was based on for the rest of the day. There are
likely to be non-diurnal trends in the temperatures for today, with
cold air advection offsetting the typical diurnal heating. Thus, the
temperatures through the early-to-mid afternoon are likely to be
fairly stready, falling sharply around and after sunset.
&&
.SHORT TERM [Tonight Through Monday]...
For tonight, with a cold airmass and decoupling winds, there is high
confidence that all but the SE Big Bend will see a freeze. Local
confidence tool places highest probabilities (100%) across NW third
of our area down to nil chances across SE Big Bend. Guidance shows
that CAA should be strong enough to offset a slight breeze as high
remains to our NW. Freeze Watch remains in effect for all but the SE
Big Bend from 07-14z Sunday. This watch will likely be upgraded to a
warning later today. Wind chills are likely to be in the 20s across
much of the area, and perhaps isolated upper teens in SE Alabama so
a wind chill advisory may also be issued later today for this area.
On Sunday, high will build north of the region with ridge likely
extending from Appalachians down to the Nrn Gulf of Mex. So expect
another cool day with highs in the low to mid 50s to be followed by
another chilly Sunday Night, with the potential for yet another more
limited freeze as high pressure becomes centered over the
Southeast. Local confidence tool with 70% chance of freezing temps
NRN tier GA counties down to zero coastal Panhandle counties. On
Monday, next upper trough to move from Rockies EWD to MS Valley
by nightfall. this will help shift local surface high ewd with
veering winds ahead of this the next weather system. as a result,
temps will begin to rise to the low to mid 60s.
&&
.Long Term [Monday night through next Saturday]...
Not much change to the forecast since this time yesterday. The
period is forecast to begin with zonal flow on the toes of an
approaching, weak, shortwave entering the Southern Plains with high
pressure just beginning to break down at the surface. As the
shortwave grazes the Gulf coast, surface cyclogenesis will commence,
and the entire system will move into the Southeast on Wednesday. It
will take another shortwave developing in the Southern Plains early
on Thursday to completely clear out the remnants of the
aforementioned system as another surface low and attendant front
pass through the Tri-State area Thursday through early Friday.
Instability will be greatly lacking with both systems and only
showers are expected. Near average to slightly below average
temperatures are expected to dominate the extended range forecast.
&&
.AVIATION [through 12z Sunday]...
Updated at: 649 am EST
Showers have come to an end at all terminals. Ceilings will bounce
between IFR and MVFR for the next hour or so before stabilizing to
MVFR restrictions for all terminals through the first part of the
day. Thereafter, it is likely that all but KABY will scatter to VFR.
KABY will take a bit longer and will likely have at least high end
MVFR ceilings for much of the day. The only other concern will be
gusty WNW winds. Expect gusts between 25 to 30 knots early, falling
to around 20 knots later in the afternoon. VFR conditions will
prevail overnight tonight.
&&
.MARINE...
Latest forecast winds show 20-kt winds spreading across wrn legs and
beginning to impact eastern legs, so advisory remains in effect for
all the waters. A winds shift was already occurring as a cold front
crosses the marine area. Offshore winds and seas should then stay
elevated for much of the weekend with seas peaking at 8 feet at the
offshore buoys. Winds and seas will drop below headline criteria by
Sunday evening and then gradually veer to onshore once again for
early next week. The next cold front is forecast to cross the waters
Tuesday evening.
&&
.FIRE WEATHER...
Although relative humidity values will be below the "critical" 35%
mark for north Florida on Sunday, ERC values are currently forecast
to be very low (for Saturday at least). Thus if this remains
constant, Red Flag criteria will not be met. Beyond Sunday, relative
humidity values will climb above 35% relieving any Red Flag concerns.
&&
.HYDROLOGY...
No flood concerns expected from the recent rainfall. One half inch
rainfall forecast tonight will help keep flows up a bit on the
smaller creeks and streams some possibly reaching action stage in
the upper drainages. Meanwhile routed flow down stream continues
to generate minor rises on the lower Choctawhatchee, Ochlockonee
and Withlacoochee Rivers. Nothing significant is happening on the
Chattahoochee or Apalachicola Rivers from the recent rainfall and
nothing significant is expected with tonight`s rainfall. All other
drainages including the Suwannee River are pretty much flat.
Models continue to indicate a more significant rain event around
New Years that might last a day or two. Though the amounts do not
look enough to generate a flood event, this could be a welcome
rain across the drought affected areas.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 60 31 55 31 66 / 10 0 0 0 10
Panama City 55 35 55 40 65 / 0 0 0 0 10
Dothan 49 28 52 33 62 / 10 0 0 0 10
Albany 50 28 54 30 64 / 10 0 0 0 10
Valdosta 63 31 54 32 66 / 10 0 0 0 0
Cross City 70 32 57 33 70 / 10 0 0 0 0
Apalachicola 63 35 55 41 64 / 10 0 0 0 10
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...FREEZE WATCH from late tonight through Sunday morning for
Calhoun-Central Walton-Coastal Bay-Coastal Franklin-
Coastal Gulf-Coastal Wakulla-Gadsden-Holmes-Inland Bay-
Inland Franklin-Inland Gulf-Inland Jefferson-Inland
Wakulla-Inland Walton-Jackson-Leon-Liberty-South Walton-
Washington.
GA...FREEZE WATCH from late tonight through Sunday morning for
all zones.
AL...FREEZE WATCH from late tonight through Sunday morning for
Coffee-Dale-Geneva-Henry-Houston.
GM...SMALL CRAFT ADVISORY until 10 AM EST Sunday for all zones.
&&
$$
NEAR TERM...Lamers
SHORT TERM...Block
LONG TERM...Harrigan
AVIATION...Harrigan
MARINE...Block
FIRE WEATHER...Harrigan
HYDROLOGY...Lanier
AREA FORECAST DISCUSSION
NWS CHARLESTON SC
434 AM EST SAT DEC 29 2012
.SYNOPSIS...
HIGH PRESSURE WILL BUILD INTO THE AREA BEHIND A COLD FRONT TODAY.
ANOTHER FRONTAL SYSTEM WILL DROP INTO THE SOUTHEAST UNITED STATES
TUESDAY AND PERSIST IN THE VICINITY THROUGH THURSDAY NIGHT. HIGH
PRESSURE WILL BUILD BACK IN FOR LATE NEXT WEEK INTO THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
PRE-DAWN...RAINFALL WASTED NO TIME DEVELOPING AFTER MIDNIGHT AS THE
SYNOPTIC SYSTEM MOVING THROUGH THE REGION IS QUITE DYNAMIC WITH A
110 KT JET AT 500 MM BLASTING THROUGH THE LOWER GULF COAST AREA.
THE RUC HAS A GOOD HANDLE ON THE POCKET OF BEST MID LEVEL INSTABILITY
OVER THE NORTHERN HALF OF FLORIDA AND FAIRLY UNSTABLE MID LEVELS
ARE PROGGED TO SHIFT NE OVER THE EASTERN PART OF OUR FORECAST AREA
AROUND DAYBREAK. WE WILL CONTINUE TO MENTION ISOLATED THUNDER AT
FORECAST INITIALIZATION TIME BUT THE WINDOW IS VERY SMALL. WAVES
OF LOW PRES MOVING THROUGH...BUT RISK FOR ANY SURFACE BASED INSTABILITY
LOOKS TO STAY TO OUR S ANCHORED BY THE WIDESPREAD RAIN CURRENTLY
FALLING IN OUR AREA.
TODAY...SECONDARY LOW PRES DEVELOPING OVER FORECAST AREA IS FORECAST
TO RACE NE ALONG THE SOUTH CAROLINA COAST NEAR DAYBREAK THEN DEEPEN
ALONG THE NORTH CAROLINA OUTER BANKS AT MIDDAY. WIDESPREAD RAINFALL
IS FORECAST TO QUICKLY END BETWEEN 7 AM AND 10 AM AS THE ATTENDANT
COLD FRONT RACES OFF OUR COAST AND A STRONG DRY SLOT BLASTS IN FROM
THE W TO SW OVER GEORGIA AND SOUTH CAROLINA. WE THINK RAIN WILL BE
OVER FOR ALL OF OUR REGION PRIOR TO NOON AT THE RATE THE BACK EDGE
OF THE PCPN SHIELD IS ADVANCING. DOWNSLOPING POST-FRONTAL LOW
LEVEL FLOW AND BUILDING MID LEVEL SUBSIDENCE SHOULD RESULT IN
RAPID CLEARING BY THIS AFTERNOON. TEMPS LATER TODAY SHOULD RANGE
FROM THE MID 50S CLOSE TO THE CSRA AND SE MIDLANDS TO THE LOWER
60S CLOSE TO THE COAST...MAX READINGS A COUPLE OF DEGREES WARMER.
IT WILL BECOME BREEZY TODAY ESPECIALLY AFTER THE SUNSHINE COMMENCES
AND MIXING IMPROVES.
WE HAVE ISSUED A LAKE WIND ADVISORY FOR GUSTY W WINDS 15 TO 25 KT
THIS AFTERNOON...MOST PREVALENT ALONG LAKE SHORES.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
A MODIFYING CONTINENTAL POLAR AIR MASS WILL BEGIN TO TAKE HOLD TONIGHT
AS SURFACE HIGH PRES WORKS IN FROM THE W. MAINLY CLEAR SKIES AND
STIRRING W TO NW SURFACE WINDS WILL DRIVE IN COLDER AIR WITH TIME.
MANY INLAND AREAS LIKELY TO BE NEAR OR EVEN SLIGHTLY BELOW FREEZING
BY DAYBREAK SUNDAY.
LAKE WIND ADVISORY TO CONTINUE THROUGH THE EVENING OVER LAKE MOULTRIE
AS WINDS AND WAVES PEAK IN THE EVENING AS COLD AIR ADVECTION AND
MIXING PARAMETERS SUGGEST FREQUENT GUSTS OVER OPEN LAKE WATERS
REACHING 25 KT.
A PRONOUNCED MID-LEVEL RIDGE WILL BUILD ACROSS THE AREA SUNDAY AND
MONDAY WITH SURFACE HIGH PRESSURE MODIFYING AS IT SHIFTS EAST. COLD
ADVECTION ON SUNDAY WILL KEEP HIGH TEMPS IN THE LOWER 50S. HOWEVER
BY MONDAY AS THE SURFACE RIDGE SHIFTS EAST...THE COLD ADVECTION WILL
ABATE. A WEAK COASTAL TROUGH MAY DEVELOP OFF THE GA COAST LATE
MONDAY AFTERNOON...PRODUCING ISOLATED RAIN SHOWERS OVER THE ADJACENT
WATERS. WE WILL ALSO SEE AN INCREASE IN HIGH CLOUDS AS THE DAY WEARS
ON. TEMPS SHOULD REBOUND NICELY WITH HIGHS REACHING 60-63F.
MONDAY NIGHT INTO TUESDAY THE UPPER PATTERN TRANSITIONS TO A BROAD
TROUGH ACROSS THE EASTERN UNITED STATES. SOME ELONGATED VORTICITY
ENERGY LIFTING ACROSS THE CAROLINAS WILL PUSH A SPRAWLING FRONT INTO
THE AREA FROM THE NORTHWEST ON TUESDAY. THE LATEST PROGS SHOW A
SLOWER PROGRESSION FOR THE ASSOCIATED RAIN SHOWERS SO WE BACKED OFF
ON POPS A BIT MONDAY NIGHT AND TUESDAY MORNING. WE NOW SHOW CHANCE
POPS SPREADING INTO INLAND AREAS TUESDAY AFTERNOON. HIGH TEMPS COULD
REALLY VARY BASED ON THE SPEED OF THE FRONT AND HOW EARLY THE RAIN
MAKES IT IN. GUIDANCE INDICATES FAIRLY STRONG LOW-LEVEL WARM
ADVECTION IN ADVANCE OF THE FRONT SO WE BUMPED HIGHS INTO THE
MID/UPPER 60S ACROSS THE SOUTHERN TWO-THIRDS OF THE AREA WITH LOWER
60S FARTHER NORTH.
&&
.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
TUESDAY NIGHT THROUGH THURSDAY NIGHT LOOK FAIRLY ACTIVE DUE TO A
PLETHORA OF UPPER DISTURBANCES RIPPLING THROUGH THE BROAD EASTERN
UNITED STATES TROUGH. A WEAK FRONT SHOULD REMAIN DRAPED ACROSS THE
FORECAST AREA WITH NUMEROUS SURFACE WAVES RIDING ALONG IT. WE KEPT
CHANCE POPS IN THE FORECAST THROUGH THURSDAY...TAPERING OFF THURSDAY
NIGHT. COOL...DRY HIGH PRESSURE WILL BUILD IN FRIDAY THROUGH
SATURDAY.
&&
.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
CONDITIONS THEN DETERIORATING THIS MORNING AS RAINS QUICKLY BREAKING
OUT AND SWEEPING ENE. A WARM FRONT WILL LIFT NORTH THROUGH THE
TERMINALS WITH A 40-50 KT LOW-LEVEL JET INITIATING LOW-LEVEL WIND
SHEAR /LLWS/ AT BOTH TERMINALS AFTER 08-09Z. THE RISK FOR LLWS
WILL LINGER UNTIL THE PASSAGE OF A COLD FRONT ROUGHLY AROUND
14-15Z. A WELL DEFINED RAIN BAND WILL ACCOMPANY THE FRONT WITH
RAIN REACHING THE TERMINALS AS EARLY AS 08-09Z. EXPECT MVFR
CEILINGS TO PREVAIL WITH OCCASIONAL REDUCTIONS IN VISIBILITIES DUE
TO THE RAIN GENERALLY IN THE 08-15Z TIME FRAME. HAVE MAINTAINED
TEMPORARY IFR CEILINGS AT BOTH TERMINALS ANYWHERE FROM ABOUT
09-13Z. EXPECT RAPID CLEARING TO ENSUE ONCE THE FRONT SHIFTS
OFFSHORE AND DOWNSLOPE TRAJECTORIES TAKE HOLD.
EXTENDED AVIATION OUTLOOK...INCREASING CHANCES FOR SUB-VFR
CONDITIONS LATE TUESDAY AND WEDNESDAY AS A COLD FRONT DROPS SOUTH
INTO THE AREA.
&&
.MARINE...
A POTENT WARM FRONT IS FORECAST TO PUNCH THROUGH THE WATERS PRIOR
TO DAWN WITH A STRONG SW LOW LEVEL JET SHIFTING OVERHEAD. IT IS
A VERY COMPLEX COASTAL WATERS FORECAST THIS MORNING DUE TO VARYING
SEA SURFACE TEMPS FROM THE COAST TO 60 NM OFFSHORE. THIS EFFECTS
THE MIXING POTENTIAL OF THESE STRONG WINDS AND OUR FORECAST APPEARS
TO HAVE A REASONABLE HANDLE ON TIMING AND TRENDS. WATCHING STRONG
CONVECTION MOVING OUT OF NE FLORIDA EARLY THIS MORNING AND THERE
COULD BE A RISK FOR STRONG GUSTY WINDS WITH STORMS OVER WATERS
PRIOR TO DAYBREAK. CLOSE TO THE GULF STEAM WELL SE OF SAVANNAH
THERE COULD BE A VERY BRIEF PERIOD OF SOUTHERLY GALES AS WELL.
AFTER MID MORNING...THERE WILL PROBABLY BE A BIT OF A POST-FRONTAL
LULL AS DIRECTIONS SHIFT W. SPEEDS WILL BE RAMPING UP AGAIN THIS
AFTERNOON AS COOLER AND DRIER AIR ADVECTS INTO THE REGION. TONIGHT
WE HAVE ISSUED SMALL CRAFT ADVISORIES ALL WATERS AS W TO NW SURGING
LOOKS STRONG ENOUGH TO PRODUCE FREQUENT GUSTS OVER 25 KT WITH THE
STRONGEST FLOW OFF THE GEORGIA COAST DUE TO FAVORABLE JETTING
PROFILES. SEA HEIGHTS THROUGH TONIGHT DIFFICULT TO PIN DOWN AS
MIXING PROFILES START OFF VERY POOR THIS MORNING AND THEN BECOME
QUITE FAVORABLE TONIGHT. WE HAVE MADE SOME ADJUSTMENTS TO WAVE
WATCH OUTPUT OVER GEORGIA WATERS THIS EVENING AS FORECAST HEIGHTS
AROUND GRAYS REEF APPEAR TOO LOW FOR THE CHOPPY WIND WAVE POTENTIAL.
CONDITIONS WILL IMPROVE QUICKLY ON SUNDAY WITH TRANQUIL CONDITIONS
THROUGH MONDAY NIGHT. INCREASING SOUTHWEST FLOW AHEAD OF THE NEXT
FRONT MAY PUSH WINDS AS HIGH AS 15-20 KT WITH SEAS REACHING 5 FT
OVER THE OUTER PORTIONS. A STRONGER SURGE WILL OCCUR LATE NEXT WEEK
WHEN COLD HIGH PRESSURE BUILDS OVER THE WATERS.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...LAKE WIND ADVISORY FROM 11 AM THIS MORNING TO 1 AM EST SUNDAY
FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 9 AM EST SUNDAY
FOR AMZ350-352-354.
SMALL CRAFT ADVISORY UNTIL 11 AM EST SUNDAY FOR AMZ374.
&&
$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...JRL
LONG TERM...JRL
AVIATION...
MARINE...JRL
AREA FORECAST DISCUSSION...CORRECTED
NWS LINCOLN IL
226 PM CST SAT DEC 29 2012
.DISCUSSION...
ISSUED 220 PM CST SAT DEC 29 2012
THE MAIN CONCERN IS THE STORM SYSTEM FOR MONDAY AND NEW YEARS EVE.
MAJOR DIFFERENCES ARE STILL SHOWING UP BETWEEN THE MODELS ON THIS
ONE. THE NAM IS MUCH STRONGER AND FARTHER NORTH WITH THE BAND OF
HEAVY SNOW...INDICATING 4-7 INCHES OF SNOW ACROSS A LARGE PORTION
OF CENTRAL IL...NORTH OF I-70. PART OF THAT HAS TO DO WITH ITS
CONTINUATION OF STEADY SNOWS IN THE NORTH OVERNIGHT NEW YEARS
EVE...WHERE THE OTHER MODELS DROP PRECIP OFF IN THE EVENING. THAT
ADDITIONAL SNOW SEEMS TO BE LINKED TO THE NAM BEING THE ONLY
MODEL TO TAKE A LOW PRESSURE CENTER ACROSS SOUTHERN ILLINOIS NEW
YEARS EVE NIGHT.
THE CANADIAN GEM HAS A SIMILAR PATH FOR THE SNOW BAND AS THE
NAM...BUT HAS LESS ACCUMULATION. THE ECMWF/GFS/UKMET ARE ALL
MUCH FARTHER SOUTH AND WEAKER WITH THE DYNAMICS/PRECIP IN OUR
AREA. THEY DO INDICATE 2-3 INCHES COULD ACCUMULATE SOUTHEAST OF
I-70...WITH THE NORTHERN EDGE OF 1 INCH NEAR I-72. THAT IS THE
PATH THAT HPC HAS GENERALLY FOLLOWED...AND WE WERE PRIMARILY
INDICATING THAT IN OUR GRIDS. HOWEVER...THE NAM AND RAP WERE THE
ONLY MODELS TO SHOW THE AMOUNT OF SNOW WE PICKED UP IN OUR
SOUTHEAST COUNTIES LAST NIGHT...SO THAT LEAVES SOME UNEASY CONCERN
FOR SUCH A BUSY HOLIDAY NIGHT...IF THAT SNOW BAND DOES SHIFT
NORTH.
WE WILL GENERALLY STAY THE COURSE FOR NOW AND ADJUST AMOUNTS
SLIGHTLY TOWARD THE CURRENT SOUTHWARD CONSENSUS.
SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT
AFTER SOME LINGERING LIGHT SNOW SHOWERS/FLURRIES DEPART TO THE
EAST THIS EVENING...CLEARING SKIES APPEAR POISED TO MOVE INTO
CENTRAL ILLINOIS. NIGHT TIME MOISTURE/CLOUD TRENDS CAN BE A BIT
TRICKY WITH ADVANCING HIGH PRESSURE...SINCE THE SUBSIDENCE
INVERSION CAN SOMETIMES TRAP LOW LEVEL MOISTURE THAT THE WEAKER
LOW LEVEL WINDS ARE UNABLE TO PUSH OUT. THAT CAN LEAD TO BACK-
BUILDING LOW CLOUDS/STRATUS AT NIGHT...AFTER A STEADY CLEARING
PROGRESS IS EVIDENT BEFORE SUNSET. PILOT REPORTS CONFIRM THE THIN
LAYER OF MOISTURE OF THIS CLOUD DECK...SO THE CLEARING MAY
CONTINUE TONIGHT AS ADVERTISED IN THE MODELS. WE DID SLOW DOWN THE
PROGRESSION IN THE SKY GRIDS...BUT DO EVENTUALLY CLEAR THINGS OUT
IN THE EAST TOWARD MORNING.
THE TIMING OF THE CLEARING CAN HAVE A BIG IMPACT ON LOW
TEMPERATURES...BUT WITH CLEARING EXPECTED IN MOST AREAS BY
MORNING...WE SHOULD BE SEE LOWS DROP BELOW NORMAL ACROSS THE
BOARD...WITH SOME SINGLE DIGIT LOWS NW OF THE IL RIVER.
HIGH PRESSURE WILL PROVIDE SUNNY SKIES AND QUIET CONDITIONS ON
SUNDAY...BUT THE QUICKLY APPROACHING LOW PRESSURE SYSTEM WILL
BRING INCREASING CLOUDS SUNDAY NIGHT.
MONDAY MORNING...SNOW SHOULD BEGIN TO ADVANCE ACROSS OUR CENTRAL
COUNTIES FROM SW TO NE. LOOKING AT THE CONSENSUS MODELS
(ECMWF/GFS/UKMET) IT APPEARS THAT THE MAIN PERIOD OF STEADIER
SNOWS WILL BE MONDAY AFTERNOON AND EVENING...WHERE MOST OF THE
ACCUMULATION WILL OCCUR. SNOWFALL TOTALS UNDER THAT SCENARIO WOULD
RANGE FROM LESS THAN A HALF INCH TOWARD PEORIA...WITH THE ONE INCH
LINE AS FAR NORTH AS A LINE FROM RUSHVILLE TO LINCOLN TO
CHAMPAIGN...1-2" FROM THAT LINE SOUTH TO I-70...AND 2-3" SOUTH OF
I-70.
SOME SNOW SHOWERS MAY LINGER IN THE SOUTHEAST AFTER MIDNIGHT NEW
YEARS EVE...BUT PRECIP SHOULD COME TO AN END BY SUNRISE ON
TUESDAY. CLEARING SKIES ARE EVEN FORECAST FOR THE AFTERNOON AS
HIGH PRESSURE BUILDS INTO THE AREA FROM THE WEST. A COLD NIGHT
WILL BE ON TAP TUES NIGHT UNDER CLEAR SKIES AND LIGHT
WINDS...ALONG WITH A FRESH SNOW COVER. LOW TEMPS WOULD LIKELY DROP
BELOW GUIDANCE AND INTO THE SINGLE DIGITS IN MANY AREAS.
LONG TERM...WEDNESDAY THROUGH SATURDAY.
THE EXTENDED PERIOD WILL BE DOMINATED BY COLD AND DRY CONDITIONS
UNDER SURFACE HIGH PRESSURE. THE NORTHERN STEAM STORM TRACK LOOKS
TO REMAIN FARTHER NORTH ACROSS THE GREAT LAKES...AND THE SOUTHERN
STREAM REMAINS SOUTH...PUSHING STORM SYSTEMS ACROSS THE GULF
COAST. WE WILL KEEP HIGHS AND LOWS BELOW NORMAL...WITH THE COLDEST
NIGHT LOOKING LIKE THURSDAY NIGHT.
SHIMON
&&
.AVIATION...
ISSUED 1117 AM CST SAT DEC 29 2012
FLURRIES REMAIN SCATTERED AROUND THE AREA LATE THIS MORNING WITH
OCCASIONAL VSBYS AS LOW AS 1SM. THESE CONDITIONS SHOULD CONTINUE
THROUGH THE AFTERNOON WITH A GRADUAL DROP OFF IN COVERAGE THIS
EVENING. MIDDAY SAT IMAGERY SHOWS ONLY SLOW PROGRESS OF CLEARING
ACROSS IOWA WITH CIGS ACTUALLY LOWER ACROSS ERN IA COMPARED TO THE
FORECAST TAF SITES. AS MID-LEVEL ANTI-CYCLONIC FLOW BEGINS TO
PRODUCE SUBSIDENCE TONIGHT...PARTIAL CLEARING WILL SPREAD
SOUTHWEST TO NORTHEAST LATE TONIGHT AND CIGS SHOULD CLIMB BUT
LIKELY REMAIN MVFR UNTIL THEY SCATTER OUT SUNDAY MORNING.
BARKER
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS LINCOLN IL
220 PM CST SAT DEC 29 2012
.DISCUSSION...
ISSUED 220 PM CST SAT DEC 29 2012
THE MAIN CONCERN IS THE STORM SYSTEM FOR MONDAY AND NEW YEARS EVE.
MAJOR DIFFERENCES ARE STILL SHOWING UP BETWEEN THE MODELS ON THIS
ONE. THE NAM IS MUCH STRONGER AND FARTHER NORTH WITH THE BAND OF
HEAVY SNOW...INDICATING 4-7 INCHES OF SNOW ACROSS A LARGE PORTION
OF CENTRAL IL...NORTH OF I-70. PART OF THAT HAS TO DO WITH ITS
CONTINUATION OF STEADY SNOWS IN THE NORTH OVERNIGHT NEW YEARS
EVE...WHERE THE OTHER MODELS DROP PRECIP OFF IN THE EVENING. THAT
ADDITIONAL SNOW SEEMS TO BE LIKED TO THE NAM BEING THE ONLY
MODEL TO TAKE A LOW PRESSURE CENTER ACROSS SOUTHERN ILLINOIS NEW
YEARS EVE NIGHT.
THE CANADIAN GEM HAS A SIMILAR PATH FOR THE SNOW BAND AS THE
NAM...BUT HAS LESS ACCUMULATION. THE ECMWF/GFS/UKMET ARE ALL
MUCH FARTHER SOUTH AND WEAKER WITH THE DYNAMICS/PRECIP IN OUR
AREA. THEY DO INDICATE 2-3 INCHES COULD ACCUMULATE IN OUR AREA
SOUTHEAST OF I-70...WITH THE NORTHERN EDGE OF 1 INCH NEAR I-72.
THAT IS THE PATH THAT HPC HAS GENERALLY FOLLOWED...AND WE WERE
PRIMARILY INDICATING IN OUR GRIDS. HOWEVER...THE NAM AND RAP WERE
THE ONLY MODELS TO SHOW THE AMOUNT OF SNOW WE PICKED UP IN OUR
SOUTHEAST COUNTIES LAST NIGHT...SO THAT LEAVES SOME UNEASY CONCERN
FOR SUCH A BUSY HOLIDAY NIGHT.
WE WILL GENERALLY STAY THE COURSE FOR NOW AND ADJUST AMOUNTS
SLIGHTLY TOWARD THE CURRENT SOUTHWARD CONSENSUS.
SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT
AFTER SOME LINGERING LIGHT SNOW SHOWERS/FLURRIES DEPART TO THE
EAST THIS EVENING...CLEARING SKIES APPEAR POISED TO MOVE INTO
CENTRAL ILLINOIS. NIGHT TIME MOISTURE/CLOUD TRENDS CAN BE A BIT
TRICKY WITH ADVANCING HIGH PRESSURE...SINCE THE SUBSIDENCE
INVERSION CAN SOMETIMES TRAP LOW LEVEL MOISTURE THAT THE WEAKER
LOW LEVEL WINDS ARE UNABLE TO PUSH OUT. THAT CAN LEAD TO BACK-
BUILDING LOW CLOUDS/STRATUS AT NIGHT...AFTER A STEADY CLEARING
PROGRESS IS EVIDENT BEFORE SUNSET. PILOT REPORTS CONFIRM THE THIN
LAYER OF MOISTURE OF THIS CLOUD DECK...SO THE CLEARING MAY
CONTINUE TONIGHT AS ADVERTISED IN THE MODELS. WE DID SLOW DOWN THE
PROGRESSION IN THE SKY GRIDS...BUT DO EVENTUALLY CLEAR THINGS OUT
IN THE EAST TOWARD MORNING.
THE TIMING OF THE CLEARING CAN HAVE A BIG IMPACT ON LOW
TEMPERATURES...BUT WITH CLEARING IN MOST AREAS BY MORNING...WE
SHOULD BE SEE LOWS DROP BELOW NORMAL ACROSS THE BOARD...WITH
SOME SINGLE DIGIT LOWS NW OF THE IL RIVER.
HIGH PRESSURE WILL PROVIDE SUNNY SKIES AND QUIET CONDITIONS ON
SUNDAY...BUT THE QUICKLY APPROACHING LOW PRESSURE SYSTEM WILL
BRING INCREASING CLOUDS SUNDAY NIGHT.
MONDAY MORNING...SNOW SHOULD BEGIN TO ADVANCE ACROSS OUR CENTRAL
COUNTIES FROM SW TO NE. LOOKING AT THE CONSENSUS MODELS
(ECMWF/GFS/UKMET) IT APPEARS THAT THE MAIN PERIOD OF STEADIER
SNOWS WILL BE MONDAY AFTERNOON AND EVENING...WHERE MOST OF THE
ACCUMULATION WILL OCCUR. SNOWFALL TOTALS UNDER THAT SCENARIO WOULD
RANGE FROM LESS THAN A HALF INCH TOWARD PEORIA...WITH THE ONE INCH
LINE AS FAR NORTH AS A LINE FROM RUSHVILLE TO LINCOLN TO
CHAMPAIGN...1-2" FROM THAT LINE SOUTH TO I-70...AND 2-3" SOUTH OF
I-70.
SOME SNOW SHOWERS MAY LINGER IN THE SOUTHEAST AFTER MIDNIGHT NEW
YEARS EVE...BUT PRECIP SHOULD COME TO AN END BY SUNRISE ON
TUESDAY. CLEARING SKIES ARE EVEN FORECAST FOR THE AFTERNOON AS
HIGH PRESSURE BUILDS INTO THE AREA FROM THE WEST. A COLD NIGHT
WILL BE ON TAP TUES NIGHT UNDER CLEAR SKIES AND LIGHT
WINDS...ALONG WITH A FRESH SNOW COVER. LOW TEMPS WOULD LIKELY DROP
BELOW GUIDANCE AND INTO THE SINGLE DIGITS IN MANY AREAS.
LONG TERM...WEDNESDAY THROUGH SATURDAY.
THE EXTENDED PERIOD WILL BE DOMINATED BY COLD AND DRY CONDITIONS
UNDER SURFACE HIGH PRESSURE. THE NORTHERN STEAM STORM TRACK LOOKS
TO REMAIN FARTHER NORTH ACROSS THE GREAT LAKES...AND THE SOUTHERN
STREAM REMAINS SOUTH...PUSHING STORM SYSTEMS ACROSS THE GULF
COAST. WE WILL KEEP HIGHS AND LOWS BELOW NORMAL...WITH THE COLDEST
NIGHT LOOKING LIKE THURSDAY NIGHT.
SHIMON
&&
.AVIATION...
ISSUED 1117 AM CST SAT DEC 29 2012
FLURRIES REMAIN SCATTERED AROUND THE AREA LATE THIS MORNING WITH
OCCASIONAL VSBYS AS LOW AS 1SM. THESE CONDITIONS SHOULD CONTINUE
THROUGH THE AFTERNOON WITH A GRADUAL DROP OFF IN COVERAGE THIS
EVENING. MIDDAY SAT IMAGERY SHOWS ONLY SLOW PROGRESS OF CLEARING
ACROSS IOWA WITH CIGS ACTUALLY LOWER ACROSS ERN IA COMPARED TO THE
FORECAST TAF SITES. AS MID-LEVEL ANTI-CYCLONIC FLOW BEGINS TO
PRODUCE SUBSIDENCE TONIGHT...PARTIAL CLEARING WILL SPREAD
SOUTHWEST TO NORTHEAST LATE TONIGHT AND CIGS SHOULD CLIMB BUT
LIKELY REMAIN MVFR UNTIL THEY SCATTER OUT SUNDAY MORNING.
BARKER
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
156 PM CST SAT DEC 29 2012
.DISCUSSION...
1159 AM CST
MAIN CONCERN ARE THE ONGOING SNOW SHOWERS ACROSS NORTHEAST
ILLINOIS AND NORTHWEST INDIANA...WITH LAKE EFFECT SNOW SHOWERS TO
PERSIST ACROSS NORTHWEST INDIANA LATE THIS AFTERNOON AND EARLY
EVENING.
LATEST RADAR IMAGERY DEPICTING PERSISTENT SNOW SHOWERS EARLY THIS
AFTERNOON ACROSS THE AREA...WITH ONLY LIGHT SNOW ONGOING AT THIS
TIME. THESE SNOW SHOWERS CONTINUE TO DEVELOP NEAR SURFACE
TROUGH/MID LEVEL TROUGH AXIS SITUATED FROM EASTERN WISCONSIN
SOUTHEAST THROUGH SOUTHERN LAKE MICHIGAN...OUT AHEAD OF SEVERAL
SUBTLE SHORT WAVE TROUGHS TRAVERSING UPPER LEVEL CYCLONIC FLOW.
DESPITE THE APPROACH OF ANOTHER MID LEVEL TROUGH AXIS TO THE
WEST...DEEPER FORCING WITHIN THIS SURFACE/MID LEVEL TROUGH AXIS
WILL WEAKEN WITH TIME EARLY THIS AFTERNOON AS IT DAMPENS OUT WITH
MAIN SURFACE LOW CONTINUING TO DEPART TO THE EAST. WHAT THIS MEANS
IN THE NEAR TERM IS CURRENT LIGHT SNOW ACROSS NORTHEAST ILLINOIS
WILL SLOWLY DIMINISH THROUGH MID AFTERNOON WITH ONLY LIGHT
ACCUMULATIONS OF AT MOST A COUPLE TENTHS OF AN INCH OF SNOWFALL.
ALTHOUGH...DO EXPECT FLURRIES TO REMAIN POSSIBLE ACROSS ALL OF
NORTHERN ILLINOIS THROUGH THE REMAINDER OF THE AFTERNOON AS WEAK
ASCENT OUT AHEAD OF THE APPROACHING MID LEVEL TROUGH REMAINS.
FOCUS THEN SHIFTS TO LAKE EFFECT POTENTIAL ACROSS NORTHWEST
INDIANA. CURRENT RADAR RETURNS ACROSS SOUTHERN LAKE MICHIGAN AND
NORTHWEST INDIANA ARE INDICATING THAT BETTER LAKE EFFECT SNOW IS
ONGOING AT THIS TIME. THIS IS IN RESPONSE TO BOUNDARY LAYER WINDS
SHIFTING MORE NORTHERLY ACROSS THE LENGTH OF THE LAKE AND COLD
ADVECTION HELPING FOR BETTER THERMODYNAMIC CONDITIONS OVER THE
LAKE. WITH LATEST RAP ANALYSIS INDICATING MODERATE DELTA TS IN
PLACE AND STRONG FORCING ASSOCIATED WITH CURRENT SURFACE
CONVERGENCE ACROSS THE SOUTHERN END OF THE LAKE...EXPECT THIS LAKE
EFFECT SNOW TO CONTINUE TO INCREASE IN INTENSITY THROUGH THIS
AFTERNOON. ALTHOUGH DO EXPECT SEVERAL HOURS OF LIGHT TO MODERATE
SNOW ACROSS LAKE AND PORTER COUNTIES IN INDIANA...THIS WILL REMAIN
RATHER BRIEF AS BETTER CONVERGENCE WILL CONTINUE TO SHIFT EAST
WITH TIME. THIS WILL SHIFT BETTER SNOW DEVELOPMENT JUST EAST OF
PORTER COUNTY BY LATE THIS AFTERNOON. HIGH RES/SHORT TERM GUIDANCE
HAS BEEN INDICATING THIS LIKELY SCENARIO OVER THE LAST COUPLE OF
HOURS...AND FEEL CONFIDENT THIS WILL OCCUR AS CURRENT OBSERVATIONS
ARE ALREADY SHOWING BETTER CONVERGENCE JUST TO THE EAST OF OUR
CWA...WITH WESTERLY WINDS IN PLACE ACROSS PORTER COUNTY. SNOWFALL
THIS AFTERNOON FOR LAKE AND PORTER COUNTIES IN INDIANA WILL
CONSIST OF AROUND AN INCH OF ADDITIONAL SNOWFALL IN LAKE
COUNTY...AND WITH 1 TO 2 INCHES EXPECTED IN PORTER COUNTY. WITH
THE MAIN AXIS OF HEAVIER SNOW EXPECTED JUST TO THE EAST OF PORTER
COUNTY LINE THROUGH THIS EVENING...IT WOULD NOT BE OUT OF THE
QUESTION FOR AREAS IN AND AROUND THIS LOCATION TO POSSIBLY OBSERVE
3 INCHES BEFORE ALL THE SNOW SHIFTS COMPLETELY TO THE EAST.
RODRIGUEZ
//PREV DISCUSSION...
453 AM CST
LIGHT SNOW AND FLURRIES TO CONTINUE ACROSS THE NORTHERN 2/3RD OF
THE FORECAST AREA THIS MORNING. VAD WINDS FROM SE WI AND NE IL
88D AND TERMINAL DOPPLER RADARS ARE SHOWING A WEAK MID LEVEL LOW
OVER THE EASTERN PORTION OF THE WI-IL STATE LINE. THE 29.06Z GFS
AND 29.00Z GEM BEST DEPICT THE FEATURE BUT POSITION IT A BIT TOO
FAR TO THE N. THIS MID LEVEL LOW IS PROGGED BY THE ABOVE
MENTIONED MODELS TO FURTHER WEAKEN AS IT MOVES ESE TO FAR SW
LOWER MI AND NORTHERN IN BY 18Z. WEAK LOWER LEVEL WARM AIR
ADVECTION ASSOCIATED WITH THIS MID LEVEL LOW IS RESULTING IN
SUFFICIENT ISENTROPIC UPGLIDE FOR LIGHT SNOW AND FLURRIES TO
CONTINUE UNTIL LATER THIS MORNING WHEN THE DISTURBANCE HAS MOVED
FURTHER TO THE ESE.
WATER VAPOR SATELLITE LOOP SHOWS THE MEAN UPPER TROF AXIS FROM
NORTHWESTERN HUDSON BAY S ACROSS THE UPPER MIDWEST AND ON TO THE
LOWER MS VALLEY. WITHIN THIS TROF ARE A PAIR OF SHORT WAVES...
ONE CURRENTLY OVER SOUTHERN LAKE MI S TO SW IN GENERATING A BROAD
SWATH OF PRECIPITATION FROM THE MID OH VALLEY TO THE NORTHEASTERN
STATES. THE SECOND SHORT WAVE IS OVER EASTERN MN SSW TO IA AND
THEN SW TO EASTERN KS. NO PRECIPITATION OR COOLING CLOUD TOPS ARE
SEEN WITH THIS FEATURE WHICH IS TO CROSS OVER THE LOCAL FORECAST
AREA DURING THE EARLY AND MID AFTERNOON.
DEEPER CLOUDS HAVE BEEN MOVING TO THE E ACROSS SE WI AND NW AND
W CENTRAL IL DURING THE EARLY MORNING HOURS. LOW STRATUS STILL
EXTENDS ALL THE WAY W ACROSS IA TO THE MO RIVER AND MN TO NEAR
ITS BORDER WITH THE DAKOTAS. MODEL RH PROGS SUGGEST THIS IS TO
CONTINUE TODAY THOUGH THE LOWER CLOUD DECK WILL NOT START
CLEARING W TO E UNTIL LATE AFTERNOON AND TONIGHT. SUSPECT THAT
LACK OF MID LEVEL CLOUDS AND OF THICKER LOW LEVEL CLOUDS WILL
PRECLUDE ANY ADDITIONAL LIGHT SNOW THIS AFTERNOON.
HOWEVER...COLDER AIR SPREADING S OVER THE WESTERN GREAT LAKES IN
THE WAKE OF THE FIRST SHORT WAVE IS RESULTING IN THE DEVELOPMENT
OF A MID LAKE SNOW BAND WHICH STARTED FORMING AROUND 06Z. THE
BAND IS BECOMING WELL ORGANIZED AND E OF FAR SOUTHEASTERN WI AND
IS JUST OFFSHORE OF FAR NW IN. EARLIER MODELS SUGGESTED THAT THE
BAND WOULD FORM ALONG THE WEST SIDE OF THE LAKE AND CATCH EXTREME
NE IL BEFORE BACKING FLOW BUSHED IT OUT TO MID LAKE. IT NOW
APPEARS THAT AREAS ALONG THE IL SHORE WILL BE SPARED ANY LAKE
EFFECT SNOWS AS LATEST HI RES MODELS ARE INDICATING THE
CONVERGENCE AND RESULTING SNOW BAND WILL IMPACT PORTER AND
EASTERN LAKE COUNTIES THIS MORNING BEFORE CONTINUED BACKING OF
THE WIND FIELD SHIFTS THE TAIL END OF THE BAND FURTHER E TOWARD
FAR SW LOWER MI AND N CENTRAL IN.
NO SIGNIFICANT STORMS SEEN AFFECTING THE AREA OVER THE NEXT WEEK.
THERE IS A CHANCE OF SOME LIGHT SNOW ACROSS THE SOUTH PORTION OF
THE FORECAST AREA MON AND MON NIGHT AS A DISTURBANCE MOVING E
ACROSS THE PLAINS SENDS A RIPPLE ALONG A STATIONARY FRONT THE IS
PROGGED TO EXTEND FROM SOUTHERN MO NORTHEASTWARD ACROSS SW AND E
CENTRAL IL. THERE IS ALSO A SMALL CHANCE OF LIGHT SNOW ACROSS
MAINLY NORTHERN IL WED NIGHT INTO THU AS A SHORT WAVE DROPS OVER
THE UPPER MIDWEST AND MID MS VALLEY.
OF NOTE IS THE COLDER...MORE TYPICAL JANUARY TYPE TEMPERATURES
THAT WILL BE FELT ESPECIALLY DURING MID AND LATE NEXT WEEK. THE
COLD AIR THAT HAS BEEN CONTAINED TO THE ARCTIC AND NORTHERN
CANADA HAS GRADUALLY SPREAD S AND NOW SITS OVER MANITOBA AND
WESTERN ONTARIO. AS THE SHORT WAVE CROSSES THE REGION LATER TODAY
AND THIS EVENING THIS COLD AIR WILL BE DIRECTED ACROSS THE UPPER
MIDWEST. THIS COLDER AIR STARTS TO RETREAT OVERNIGHT SAT AND SUN
AS RIDGING BUILDS IN FROM THE W BACKING THE FLOW FORM OUT OF THE
W AND EVENTUALLY SW SO BY MONDAY TEMPERATURES AT BACK TO OR A TAD
ABOVE NORMALS FOR EARLY JANUARY.
THE COLD AIR DEPARTS FOR ONLY A SHORT PERIOD BEFORE MAKING A
STRONGER APPEARANCE DURING BUT MAKES A RETURN VISIT MONDAY AS A
COLD FRONT TRAILING SOUTHWESTWARD FROM LOW PRESSURE MOVING ACROSS
ONTARIO. THE COLD AIR WILL BE AROUND FOR A BIT LONGER THIS TIME
AS THE MEAN FLOW REMAINS FROM THE NNW AND N THROUGH THE MID AND
LATE WEEK. TEMPERATURES LOOK TO MODERATE FOR NEXT WEEKEND AS AIR
OF PACIFIC ORIGIN SPREADS ACROSS THE NORTHERN ROCKIES AND
NORTHERN PLAINS AS THE UPPER FLOW DE-AMPLIFIES.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* SNOW FLURRIES IN THE AREA. VISIBILITY SHOULD REMAIN VFR.
* WEST TO NORTHWEST WINDS. GRADUALLY TURNING TO SOUTHWEST LATE
TONIGHT INTO SUNDAY.
PAW
//DISCUSSION...UPDATED 18Z...
AVIATION CONDITIONS CONTINUE TO BE CHALLENGING FOR THE CHICAGO
AREA TERMINALS THIS AFTERNOON. THERE IS A BAND OF LIGHT SNOW
ACROSS THE AREA THAN WILL CONTINUE TO AFFECT GYY AND COULD GET
INTO ORD...MDW OR DPA AT TIMES. VISIBILITIES IN THE 3-5 MILES
RANGE WITH THE LIGHT SNOW. EVENTUALLY THE SLIGHTLY DRIER AIR AT RFD
THIS AFTERNOON WILL WORK ITS WAY EAST AND BRING THE SNOW TO AN END
THIS EVENING.
A HIGH PRESSURE RIDGE WILL MOVE ACROSS NORTHERN ILLINOIS AND
NORTHWEST INDIANA TONIGHT AND SUNDAY...WHICH WILL HELP TO BREAK UP
THE CEILINGS AND SHIFT THE WINDS TO THE WEST AND SOUTHWEST.
PAW
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* MEDIUM CONFIDENCE IN VISIBILITY REMAINING VFR.
* HIGH CONFIDENCE IN WIND TREND.
PAW
//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...
SUNDAY NIGHT...DRY. VFR.
* MONDAY...DRY. MVFR POSSIBLE.
* TUESDAY AND WEDNESDAY...DRY/VFR.
* WEDNESDAY NIGHT AND THURSDAY...SLIGHT CHANCE OF SNOW SHOWERS/MVFR.
* FRIDAY...DRY. VFR.
BEACHLER
&&
.MARINE...
300 AM CST
RATHER QUIET PERIOD FOR LAKE MICHIGAN WILL CONTINUE...OUTSIDE OF
THE POTENTIAL FOR SMALL CRAFT CONDS ALONG THE NORTHWEST INDIANA
NEARSHORE WATERS. OTHERWISE WINDS WILL REMAIN SUB-GALE CRITERIA
FOR THE OPEN WATERS.
A TROUGH OF LOW PRESSURE CONTINUES TO LIFT OFF TO THE NORTHEAST...AS
A BROAD RIDGE OF HIGH PRESSURE OVER THE CENTRAL PLAINS STRETCHES
TO THE WESTERN GULF OF MEXICO. THIS HIGH PRESSURE WILL DRIFT EAST
AND BECOME CENTERED ACROSS THE TENNESSEE VALLEY SUNDAY. THIS WILL
PROVIDE AN INFLUENCE ON THE WEATHER OVER LAKE MICHIGAN WITH A
GRADIENT SETTING THE STAGE FOR WINDS TO INCREASE TO 15 TO 25 KT
FROM THE NW/W. A FEW GUSTS TO 30 KT LATE TONIGHT MAY OCCUR...HOWEVER
NOT EXPECTING A WIDESPREAD SITUATION. AS A RESULT OF THE INCREASED
WINDS AND FETCH...WAVES WILL BUILD TO SMALL CRAFT CONDS OR 4 TO 7
FT ALONG THE INDIANA NEARSHORE WATERS THIS AFTERNOON THROUGH
SUNDAY MORNING.
THEN WINDS SLOWLY SHIFT TO THE SW MIDDAY SUN AND SHOULD AID IN
LOWERING WAVES TO ARND 3 TO 5 FT. THEN THE SOUTHWEST FLOW WILL
CONTINUE THROUGH MON AS YET ANOTHER LOW PRESSURE SYSTEM IS
EXPECTED TO LIFT NORTHEAST ACROSS THE UPPER MIDWEST TO NORTH OF
LAKE SUPERIOR MON. A TRAILING FRONTAL BOUNDARY WILL REACH LAKE
MICHIGAN LATER MON. THEN ANOTHER TIGHT PRESSURE GRADIENT DEVELOPS
TUE...HOWEVER GUIDANCE DOES NOT INDICATE THAT WINDS WOULD GUSTS
ABOVE 30 KT.
BEACHLER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 9 AM SUNDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1226 PM CST SAT DEC 29 2012
.DISCUSSION...
1159 AM CST
MAIN CONCERN ARE THE ONGOING SNOW SHOWERS ACROSS NORTHEAST
ILLINOIS AND NORTHWEST INDIANA...WITH LAKE EFFECT SNOW SHOWERS TO
PERSIST ACROSS NORTHWEST INDIANA LATE THIS AFTERNOON AND EARLY
EVENING.
LATEST RADAR IMAGERY DEPICTING PERSISTENT SNOW SHOWERS EARLY THIS
AFTERNOON ACROSS THE AREA...WITH ONLY LIGHT SNOW ONGOING AT THIS
TIME. THESE SNOW SHOWERS CONTINUE TO DEVELOP NEAR SURFACE
TROUGH/MID LEVEL TROUGH AXIS SITUATED FROM EASTERN WISCONSIN
SOUTHEAST THROUGH SOUTHERN LAKE MICHIGAN...OUT AHEAD OF SEVERAL
SUBTLE SHORT WAVE TROUGHS TRAVERSING UPPER LEVEL CYCLONIC FLOW.
DESPITE THE APPROACH OF ANOTHER MID LEVEL TROUGH AXIS TO THE
WEST...DEEPER FORCING WITHIN THIS SURFACE/MID LEVEL TROUGH AXIS
WILL WEAKEN WITH TIME EARLY THIS AFTERNOON AS IT DAMPENS OUT WITH
MAIN SURFACE LOW CONTINUING TO DEPART TO THE EAST. WHAT THIS MEANS
IN THE NEAR TERM IS CURRENT LIGHT SNOW ACROSS NORTHEAST ILLINOIS
WILL SLOWLY DIMINISH THROUGH MID AFTERNOON WITH ONLY LIGHT
ACCUMULATIONS OF AT MOST A COUPLE TENTHS OF AN INCH OF SNOWFALL.
ALTHOUGH...DO EXPECT FLURRIES TO REMAIN POSSIBLE ACROSS ALL OF
NORTHERN ILLINOIS THROUGH THE REMAINDER OF THE AFTERNOON AS WEAK
ASCENT OUT AHEAD OF THE APPROACHING MID LEVEL TROUGH REMAINS.
FOCUS THEN SHIFTS TO LAKE EFFECT POTENTIAL ACROSS NORTHWEST
INDIANA. CURRENT RADAR RETURNS ACROSS SOUTHERN LAKE MICHIGAN AND
NORTHWEST INDIANA ARE INDICATING THAT BETTER LAKE EFFECT SNOW IS
ONGOING AT THIS TIME. THIS IS IN RESPONSE TO BOUNDARY LAYER WINDS
SHIFTING MORE NORTHERLY ACROSS THE LENGTH OF THE LAKE AND COLD
ADVECTION HELPING FOR BETTER THERMODYNAMIC CONDITIONS OVER THE
LAKE. WITH LATEST RAP ANALYSIS INDICATING MODERATE DELTA TS IN
PLACE AND STRONG FORCING ASSOCIATED WITH CURRENT SURFACE
CONVERGENCE ACROSS THE SOUTHERN END OF THE LAKE...EXPECT THIS LAKE
EFFECT SNOW TO CONTINUE TO INCREASE IN INTENSITY THROUGH THIS
AFTERNOON. ALTHOUGH DO EXPECT SEVERAL HOURS OF LIGHT TO MODERATE
SNOW ACROSS LAKE AND PORTER COUNTIES IN INDIANA...THIS WILL REMAIN
RATHER BRIEF AS BETTER CONVERGENCE WILL CONTINUE TO SHIFT EAST
WITH TIME. THIS WILL SHIFT BETTER SNOW DEVELOPMENT JUST EAST OF
PORTER COUNTY BY LATE THIS AFTERNOON. HIGH RES/SHORT TERM GUIDANCE
HAS BEEN INDICATING THIS LIKELY SCENARIO OVER THE LAST COUPLE OF
HOURS...AND FEEL CONFIDENT THIS WILL OCCUR AS CURRENT OBSERVATIONS
ARE ALREADY SHOWING BETTER CONVERGENCE JUST TO THE EAST OF OUR
CWA...WITH WESTERLY WINDS IN PLACE ACROSS PORTER COUNTY. SNOWFALL
THIS AFTERNOON FOR LAKE AND PORTER COUNTIES IN INDIANA WILL
CONSIST OF AROUND AN INCH OF ADDITIONAL SNOWFALL IN LAKE
COUNTY...AND WITH 1 TO 2 INCHES EXPECTED IN PORTER COUNTY. WITH
THE MAIN AXIS OF HEAVIER SNOW EXPECTED JUST TO THE EAST OF PORTER
COUNTY LINE THROUGH THIS EVENING...IT WOULD NOT BE OUT OF THE
QUESTION FOR AREAS IN AND AROUND THIS LOCATION TO POSSIBLY OBSERVE
3 INCHES BEFORE ALL THE SNOW SHIFTS COMPLETELY TO THE EAST.
RODRIGUEZ
&&
.PREV DISCUSSION...
453 AM CST
LIGHT SNOW AND FLURRIES TO CONTINUE ACROSS THE NORTHERN 2/3RD OF
THE FORECAST AREA THIS MORNING. VAD WINDS FROM SE WI AND NE IL
88D AND TERMINAL DOPPLER RADARS ARE SHOWING A WEAK MID LEVEL LOW
OVER THE EASTERN PORTION OF THE WI-IL STATE LINE. THE 29.06Z GFS
AND 29.00Z GEM BEST DEPICT THE FEATURE BUT POSITION IT A BIT TOO
FAR TO THE N. THIS MID LEVEL LOW IS PROGGED BY THE ABOVE
MENTIONED MODELS TO FURTHER WEAKEN AS IT MOVES ESE TO FAR SW
LOWER MI AND NORTHERN IN BY 18Z. WEAK LOWER LEVEL WARM AIR
ADVECTION ASSOCIATED WITH THIS MID LEVEL LOW IS RESULTING IN
SUFFICIENT ISENTROPIC UPGLIDE FOR LIGHT SNOW AND FLURRIES TO
CONTINUE UNTIL LATER THIS MORNING WHEN THE DISTURBANCE HAS MOVED
FURTHER TO THE ESE.
WATER VAPOR SATELLITE LOOP SHOWS THE MEAN UPPER TROF AXIS FROM
NORTHWESTERN HUDSON BAY S ACROSS THE UPPER MIDWEST AND ON TO THE
LOWER MS VALLEY. WITHIN THIS TROF ARE A PAIR OF SHORT WAVES...
ONE CURRENTLY OVER SOUTHERN LAKE MI S TO SW IN GENERATING A BROAD
SWATH OF PRECIPITATION FROM THE MID OH VALLEY TO THE NORTHEASTERN
STATES. THE SECOND SHORT WAVE IS OVER EASTERN MN SSW TO IA AND
THEN SW TO EASTERN KS. NO PRECIPITATION OR COOLING CLOUD TOPS ARE
SEEN WITH THIS FEATURE WHICH IS TO CROSS OVER THE LOCAL FORECAST
AREA DURING THE EARLY AND MID AFTERNOON.
DEEPER CLOUDS HAVE BEEN MOVING TO THE E ACROSS SE WI AND NW AND
W CENTRAL IL DURING THE EARLY MORNING HOURS. LOW STRATUS STILL
EXTENDS ALL THE WAY W ACROSS IA TO THE MO RIVER AND MN TO NEAR
ITS BORDER WITH THE DAKOTAS. MODEL RH PROGS SUGGEST THIS IS TO
CONTINUE TODAY THOUGH THE LOWER CLOUD DECK WILL NOT START
CLEARING W TO E UNTIL LATE AFTERNOON AND TONIGHT. SUSPECT THAT
LACK OF MID LEVEL CLOUDS AND OF THICKER LOW LEVEL CLOUDS WILL
PRECLUDE ANY ADDITIONAL LIGHT SNOW THIS AFTERNOON.
HOWEVER...COLDER AIR SPREADING S OVER THE WESTERN GREAT LAKES IN
THE WAKE OF THE FIRST SHORT WAVE IS RESULTING IN THE DEVELOPMENT
OF A MID LAKE SNOW BAND WHICH STARTED FORMING AROUND 06Z. THE
BAND IS BECOMING WELL ORGANIZED AND E OF FAR SOUTHEASTERN WI AND
IS JUST OFFSHORE OF FAR NW IN. EARLIER MODELS SUGGESTED THAT THE
BAND WOULD FORM ALONG THE WEST SIDE OF THE LAKE AND CATCH EXTREME
NE IL BEFORE BACKING FLOW BUSHED IT OUT TO MID LAKE. IT NOW
APPEARS THAT AREAS ALONG THE IL SHORE WILL BE SPARED ANY LAKE
EFFECT SNOWS AS LATEST HI RES MODELS ARE INDICATING THE
CONVERGENCE AND RESULTING SNOW BAND WILL IMPACT PORTER AND
EASTERN LAKE COUNTIES THIS MORNING BEFORE CONTINUED BACKING OF
THE WIND FIELD SHIFTS THE TAIL END OF THE BAND FURTHER E TOWARD
FAR SW LOWER MI AND N CENTRAL IN.
NO SIGNIFICANT STORMS SEEN AFFECTING THE AREA OVER THE NEXT WEEK.
THERE IS A CHANCE OF SOME LIGHT SNOW ACROSS THE SOUTH PORTION OF
THE FORECAST AREA MON AND MON NIGHT AS A DISTURBANCE MOVING E
ACROSS THE PLAINS SENDS A RIPPLE ALONG A STATIONARY FRONT THE IS
PROGGED TO EXTEND FROM SOUTHERN MO NORTHEASTWARD ACROSS SW AND E
CENTRAL IL. THERE IS ALSO A SMALL CHANCE OF LIGHT SNOW ACROSS
MAINLY NORTHERN IL WED NIGHT INTO THU AS A SHORT WAVE DROPS OVER
THE UPPER MIDWEST AND MID MS VALLEY.
OF NOTE IS THE COLDER...MORE TYPICAL JANUARY TYPE TEMPERATURES
THAT WILL BE FELT ESPECIALLY DURING MID AND LATE NEXT WEEK. THE
COLD AIR THAT HAS BEEN CONTAINED TO THE ARCTIC AND NORTHERN
CANADA HAS GRADUALLY SPREAD S AND NOW SITS OVER MANITOBA AND
WESTERN ONTARIO. AS THE SHORT WAVE CROSSES THE REGION LATER TODAY
AND THIS EVENING THIS COLD AIR WILL BE DIRECTED ACROSS THE UPPER
MIDWEST. THIS COLDER AIR STARTS TO RETREAT OVERNIGHT SAT AND SUN
AS RIDGING BUILDS IN FROM THE W BACKING THE FLOW FORM OUT OF THE
W AND EVENTUALLY SW SO BY MONDAY TEMPERATURES AT BACK TO OR A TAD
ABOVE NORMALS FOR EARLY JANUARY.
THE COLD AIR DEPARTS FOR ONLY A SHORT PERIOD BEFORE MAKING A
STRONGER APPEARANCE DURING BUT MAKES A RETURN VISIT MONDAY AS A
COLD FRONT TRAILING SOUTHWESTWARD FROM LOW PRESSURE MOVING ACROSS
ONTARIO. THE COLD AIR WILL BE AROUND FOR A BIT LONGER THIS TIME
AS THE MEAN FLOW REMAINS FROM THE NNW AND N THROUGH THE MID AND
LATE WEEK. TEMPERATURES LOOK TO MODERATE FOR NEXT WEEKEND AS AIR
OF PACIFIC ORIGIN SPREADS ACROSS THE NORTHERN ROCKIES AND
NORTHERN PLAINS AS THE UPPER FLOW DE-AMPLIFIES.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* AREAS OF LIGHT SNOW WILL CONTINUE TO BE NEARBY INTO LATE
AFTERNOON. POSSIBILITY FOR BRIEF VISIBILITY IN THE 3-5 MILE
RANGE...BUT CONFIDENCE TOO LOW TO MENTION IN THE TAFS AT THIS
TIME.
* CEILINGS GENERALLY IN THE 1000 TO 1500 FEET RANGE THROUGH THE
AFTERNOON.
* NORTHWEST WINDS AROUND 10 KT...SLOWLY TURNING WEST/SOUTHWEST
LATE TONIGHT INTO EARLY SUNDAY.
PAW
//DISCUSSION...UPDATED 18Z...
AVIATION CONDITIONS CONTINUE TO BE CHALLENGING FOR THE CHICAGO
AREA TERMINALS THIS AFTERNOON. THERE IS A BAND OF LIGHT SNOW
ACROSS THE AREA THAN WILL CONTINUE TO AFFECT GYY AND COULD GET
INTO ORD...MDW OR DPA AT TIMES. VISIBILITIES IN THE 3-5 MILES
RANGE WITH THE LIGHT SNOW. EVENTUALLY THE SLIGHTLY DRIER AIR AT RFD
THIS AFTERNOON WILL WORK ITS WAY EAST AND BRING THE SNOW TO AN END
THIS EVENING.
A HIGH PRESSURE RIDGE WILL MOVE ACROSS NORTHERN ILLINOIS AND
NORTHWEST INDIANA TONIGHT AND SUNDAY...WHICH WILL HELP TO BREAK UP
THE CEILINGS AND SHIFT THE WINDS TO THE WEST AND SOUTHWEST.
PAW
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH CONFIDENCE IN CEILING AND VISIBILITY TREND. MEDIUM
CONFIDENCE IN EXACT VALUES AND TIMING.
* HIGH CONFIDENCE IN WIND TREND.
PAW
//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...
SUNDAY NIGHT...DRY. VFR.
* MONDAY...DRY. MVFR POSSIBLE.
* TUESDAY AND WEDNESDAY...DRY/VFR.
* WEDNESDAY NIGHT AND THURSDAY...SLIGHT CHANCE OF SNOW SHOWERS/MVFR.
* FRIDAY...DRY. VFR.
BEACHLER
&&
.MARINE...
300 AM CST
RATHER QUIET PERIOD FOR LAKE MICHIGAN WILL CONTINUE...OUTSIDE OF
THE POTENTIAL FOR SMALL CRAFT CONDS ALONG THE NORTHWEST INDIANA
NEARSHORE WATERS. OTHERWISE WINDS WILL REMAIN SUB-GALE CRITERIA
FOR THE OPEN WATERS.
A TROUGH OF LOW PRESSURE CONTINUES TO LIFT OFF TO THE NORTHEAST...AS
A BROAD RIDGE OF HIGH PRESSURE OVER THE CENTRAL PLAINS STRETCHES
TO THE WESTERN GULF OF MEXICO. THIS HIGH PRESSURE WILL DRIFT EAST
AND BECOME CENTERED ACROSS THE TENNESSEE VALLEY SUNDAY. THIS WILL
PROVIDE AN INFLUENCE ON THE WEATHER OVER LAKE MICHIGAN WITH A
GRADIENT SETTING THE STAGE FOR WINDS TO INCREASE TO 15 TO 25 KT
FROM THE NW/W. A FEW GUSTS TO 30 KT LATE TONIGHT MAY OCCUR...HOWEVER
NOT EXPECTING A WIDESPREAD SITUATION. AS A RESULT OF THE INCREASED
WINDS AND FETCH...WAVES WILL BUILD TO SMALL CRAFT CONDS OR 4 TO 7
FT ALONG THE INDIANA NEARSHORE WATERS THIS AFTERNOON THROUGH
SUNDAY MORNING.
THEN WINDS SLOWLY SHIFT TO THE SW MIDDAY SUN AND SHOULD AID IN
LOWERING WAVES TO ARND 3 TO 5 FT. THEN THE SOUTHWEST FLOW WILL
CONTINUE THROUGH MON AS YET ANOTHER LOW PRESSURE SYSTEM IS
EXPECTED TO LIFT NORTHEAST ACROSS THE UPPER MIDWEST TO NORTH OF
LAKE SUPERIOR MON. A TRAILING FRONTAL BOUNDARY WILL REACH LAKE
MICHIGAN LATER MON. THEN ANOTHER TIGHT PRESSURE GRADIENT DEVELOPS
TUE...HOWEVER GUIDANCE DOES NOT INDICATE THAT WINDS WOULD GUSTS
ABOVE 30 KT.
BEACHLER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 9 AM SUNDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
313 AM CST SAT DEC 29 2012
.DISCUSSION...
918 PM CST
FOR EVENING UPDATE...
HAVE MADE ONLY MINOR NEAR-TERM TWEAKS TO EARLIER UPDATE FOR TRENDS
WITH FLURRIES/PATCHY FREEZING DRIZZLE WHICH CONTINUE TO AFFECT
PORTIONS OF NORTHERN IL AT MID-EVENING. HAVE ALSO BEEFED UP POPS
ALONG THE IL/IN LAKE MICHIGAN SHORE AREAS SATURDAY...WITH POTENTIAL
FOR LAKE-EFFECT SNOW SHOWERS.
LOW PRESSURE WAS OVER THE LOWER MISSISSIPPI VALLEY THIS EVENING...
WITH A WEAK INVERTED SURFACE TROUGH EXTENDING NORTH THROUGH IL/WI.
THIS TROUGH IS ASSOCIATED WITH RATHER COMPLEX MID/UPPER LEVEL TROUGH
ACROSS THE MIDWEST...WHICH WILL CONTINUE TO MOVE EAST ACROSS THE
REGION OVERNIGHT. 00Z RAOBS FROM DVN/ILX INDICATE THE NATURE OF OUR
FLURRY/FREEZING DRIZZLE ISSUE THIS EVENING...WITH SATURATED LOW
LEVELS UP TO ABOUT 800 MB...WITH COLDEST TEMPS ONLY ABOUT -8 C TO
-10 C WITHIN THAT MOIST LAYER. THIS WAS RESULTING IN MORE
SUPERCOOLED DROPLETS THAN ICE CRYSTALS...AND DRIZZLE/FREEZING
DRIZZLE AT THE SURFACE WITH OCCASIONAL FINE SNOW GRAINS/FLURRIES. AS
MENTIONED IN EARLIER UPDATE...MAIN UPPER TROUGH AXIS AND STRONGER
VORT OVER IA IS EXPECTED TO PROPAGATE EASTWARD ACROSS NORTHERN IL
AFTER MIDNIGHT...WITH GREATER POTENTIAL TO INTRODUCE ICE CRYSTALS
AND THUS A GREATER PROBABILITY OF LIGHT SNOW/FLURRIES RATHER THAN
THE DRIZZLE EXPERIENCED THIS EVENING. HOWEVER...GUIDANCE IS
CONSISTENT IN WEAKENING THIS WAVE AS IT MOVES EAST AND DRYING UP
MODEL GENERATED QPF AS IT REACHES OUR CWA. THUS HAVE CUT BACK POPS A
BIT AND MENTIONED LIGHT SNOW/FLURRIES WITH NO REAL ACCUMULATION FOR
THE OVERNIGHT ACROSS THE AREA.
ON SATURDAY...INVERTED TROUGH/CONVERGENCE AXIS ENDS UP LINGERING
ALONG THE WESTERN SHORE OF LAKE MICHIGAN AS LOW LEVEL WINDS BACK TO
THE NORTH-NORTHWEST THROUGH AFTERNOON. LAKE-INDUCED THERMODYNAMIC
PROFILES IMPROVE THROUGH LATE SATURDAY...WITH SFC-850 DELTA T
INCREASING TO ABOUT 17 C...AND EQUILIBRIUM LEVELS INCREASING TO
NEARLY 10 KFT LATER IN THE DAY/EVENING. THIS SUPPORTS SCENARIO OF
LAKE EFFECT SNOW SHOWER DEVELOPMENT ALONG THE IL SHORE AND INTO
NORTHWEST INDIANA SATURDAY MORNING/AFTERNOON...WITH THE BAND
EVENTUALLY MOVING EAST OF THE IL SHORE AND AFFECTING MAINLY PORTER
COUNTY SATURDAY EVENING. WHILE DAYTIME TEMPS IN THE LOW/MID 30S
ESPECIALLY DOWNWIND OF THE LAKE ARE A LIMITING FACTOR...THE
POTENTIAL FOR SOME MINOR ACCUMULATION APPEARS TO EXIST ALONG THE IL
SHORE...WITH PERHAPS 2-4 INCHES POSSIBLE OVER NORTHERN/NORTHEASTERN
PORTER COUNTY WHERE THE BAND MAY BE MORE FOCUSED LATE IN THE
DAY/EARLY EVENING HOURS. THUS HAVE BUMPED POPS TO LIKELY IN THESE
AREAS AND INCREASED QPF/SNOW AMOUNTS A BIT. WINDS CONTINUE TO BACK
MORE NORTHWEST-WEST AFTER ABOUT 03Z...WHICH SHOULD SHIFT THE FOCUS
FOR LES EAST OF PORTER COUNTY BY LATE SATURDAY EVENING.
RATZER
//PREV DISCUSSION...
644 PM CST
FOR EARLY EVENING UPDATE...
HAVE ADDED A MENTION OF PATCHY FREEZING DRIZZLE TO FORECAST EARLY
THIS EVENING BASED ON CURRENT OBS/REPORT OF DZ/FZDZ ACROSS PARTS OF
NORTHERN IL.
AREA OF VERY LIGHT REFLECTIVITY...<10 DBZ...OVER NORTHERN IL PER
KLOT 88D DATA WAS PRODUCING LIGHT FREEZING DRIZZLE/FLURRIES PER
REGIONAL AWOS REPORTS AS OF 00Z. THIS APPEARS VERY REASONABLE
BASED ON FORECAST SOUNDINGS FROM 18Z NAM/23Z RAP WHICH DEPICT
SATURATED LOW LEVELS UP TO ABOUT 5000-6000 FT OR ABOUT 800
MB...WITH TEMPS ONLY -9/-10C. THIS SUGGESTS WHILE THERE MAY BE ICE
CRYSTALS PRESENT...SUPERCOOLED LIQUID DROPLETS ARE MORE PREVALENT
WHICH IS SUPPORTED BY THE SURFACE REPORTS OF FREEZING DRIZZLE. HAD
A REPORT FROM THE SOUTHEAST CORNER OF LASALLE COUNTY AROUND 6 PM
INDICATING FOG/DRIZZLE AT 30 DEGREES WITH SOME LIGHT ICING ON
OBJECTS. TEMPS GENERALLY RUNNING 30-32 F ACROSS THE AREA SO CANT
RULE OUT SOME TRACE AMOUNTS OF ICE THOUGH WOULD EXPECT MOST WELL-
TRAVELED AND TREATED ROADS WILL BE OK. SIDEWALKS...PARKING
LOTS...WINDSHIELDS OF PARKED CARS MAY SEE A LITTLE LIGHT GLAZING.
HERE AT THE WFO...VERY LIGHT DRIZZLE MORE LIKE A MIST OCCURRING
WITH NO REAL ACCUMULATION OR ICING. BASED ON THIS HAVE ISSUED AN
SPS HIGHLIGHTING THIS...BUT AT THIS TIME HAVE REFRAINED FROM A
WINTER WX ADVISORY.
STRONGER MID-LEVEL WAVE OVER CENTRAL/SOUTHWEST IA IS EXPECTED TO
APPROACH THE AREA LATER THIS EVENING/OVERNIGHT WITH A LITTLE MORE
MID-LEVEL MOISTURE WHICH SHOULD FAVOR MORE NUMEROUS ICE NUCLEI AND A
GREATER PROBABILITY OF LIGHT SNOW/FLURRIES RATHER THAN FREEZING
DRIZZLE.
WITH MOIST LOW LEVELS AND LIGHT WINDS...AREAS OF FOG ALSO NOTED WITH
VISIBILITY GENERALLY 1-3 MILES. SAME REPORT FROM LASALLE COUNTY
INDICATED VIS AS LOW AS 1/2 MILE...THOUGH WITH CLOUD COVER AM NOT
EXPECTING WIDESPREAD VIS UNDER 1 MILE.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* AREAS OF LGT SN WILL PERSIST.
* LOW CIGS/VSBYS WILL LINGER...WITH CIGS LOWERING TO IFR. WEST OF
ORD/MDW PATCHY LIFR IS POSSIBLE THRU DAYBREAK. SOME BRIEF
IMPROVEMENT WILL OCCUR...HOWEVER FOR A SMALL WINDOW OF TIME.
* WINDS HAVE SHIFTED TO 300-320 DEG AND SPEEDS HAVE INCREASED TO
ARND 6 TO 8 KT. WINDS WILL INCREASE TO ARND 10 KT LATER THIS
MORNING.
BEACHLER
//DISCUSSION...UPDATED 09Z...
SOME BETTER MIXING WAS NOTED ACROSS FAR NORTHEAST IL...MAINLY IN
THE UGN/ORD/MDW/GYY AREAS. THIS HAS RESULTED IN CIGS PUSHING TO
VFR AT TIMES. FEEL THAT THIS WILL REMAIN SHORT LIVED FOR A PERIOD
OF TIME EARLY THIS MORNING...HOWEVER CIGS JUST TO THE WEST OF THIS
AREA REMAIN LOW OR ARND 500-900FT AGL. HAVE OPTED TO INCLUDE THIS
MENTION OF IMPROVED CIGS AS A TEMPO GROUP AS THE DOMINATE CIG WILL
BE THE LOWER CONDS.
WITH THE BETTER MIXING PRECIP HAS CHANGED OVER TO LGT SN ACROSS
THE AIRFIELDS THIS MORNING. VSBYS REMAIN REDUCED FROM THE VERY
MOIST ATMOSPHERE...HOWEVER NOT AS LOW AS PREVIOUSLY ANTICIPATED.
HAVE BUMPED VSBYS UP SLIGHTLY AS WELL AS CIGS TO REFLECT THIS
TREND.
PREV DISCUSSION UPDATED 06Z...
VERY MOIST LOW LEVELS WILL REMAIN ACROSS NORTHERN IL/NORTHWEST IN
AIRFIELDS. THIS NORMALLY IS NOT A PROBLEM...HOWEVER WITH THE LACK
OF LIFT OR MIXING...THIS HAS RESULTED IN VERY LOW CIGS ARND
1200-1400FT AGL TO IN SOME LOCATIONS ARND 1000FT AGL. IN ADDITION
WITH A VERY MOIST NEAR SFC ENVIRONMENT AND TEMPS ARND FREEZING TO
JUST BELOW...THE DZ THAT HAS BEEN FALLING WAS BECOMING FZDZ.
GUIDANCE CONTINUES TO INDICATE THAT SOME LIFT WILL BEGIN TO OCCUR
SHORTLY AND SHOULD BE ENOUGH TO CHANGE ANY FZDZ OVER TO LGT SNOW.
IN ADDITION TO THE REDUCED CIGS...VSBYS WILL ALSO BE REDUCED TO
ARND 2-3SM. FURTHER WEST AWAY FROM THE SLIGHTLY WARMER ORD/MDW
AIRFIELDS...VSBYS COULD DIP TO ARND 1SM OVERNIGHT.
AS THE WEAK SYSTEM CONTINUES TO DRIFT EAST...WINDS WILL BEGIN TO
SHIFT W/NW. THIS WILL AID IN SLIGHTLY DRIER AIR FILTERING INTO THE
REGION FROM THE NW. IT DOES NOT APPEAR THAT THIS DRY AIR WILL BE
ENOUGH TO ERODE THE STRATUS LAYER INITIALLY...OVER TIME CIGS/VSBYS
WILL IMPROVE. GUIDANCE CONTINUES TO INDICATE THAT AFT 15Z CIGS
WILL FINALLY PUSH BACK TO LOW END MVFR. HAVE BACKED OFF ONLY A
COUPLE HOURS FROM EARLIER THINKING WITH RESPECT TO VFR CONDS
RETURNING. FEEL TAHT THIS MAY NOT OCCUR UNTIL AFT 00Z SUN.
MEANWHILE THE OTHER ATTENTION IS TO THE POTENTIAL FOR A LAKE
EFFECT SNOW BAND TO DEVELOP. GUIDANCE AND CURRENT THINKING IS THAT
WITH THE EXPECTED WIND FORECAST FROM THE W/NW...THAT ANY LAKE
EFFECT SNOW WOULD BE CONFINED TO GYY OR AIRFIELDS TO THE EAST OF
THIS. THE CONFIDENCE IN ANY IMPACT ON GYY HAS LOWERED SLIGHTLY
FROM EARLIER THINKING...HOWEVER THIS COULD COME BACK INTO PLAY IF
THE WINDS TURN MORE NORTHERLY. IN WHICH CASE GYY COULD BE IMPACTED
SIGNIFICANTLY WITH LGT TO MOD SNOW AND VSBYS DOWN ARND 1SM OR AT
TIMES LOWER.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* MEDIUM CONFIDENCE IN CIGS LOWERING TO IFR CONDS.
* MEDIUM CONFIDENCE IN VSBYS FORECAST.
* HIGH CONFIDENCE IN WIND DIR/SPEED FORECAST.
* MEDIUM/HIGH CONFIDENCE IN PRECIP REMAINING AS LGT SN.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
* SUNDAY...DRY/VFR.
* MONDAY...DRY. MVFR POSSIBLE.
* TUESDAY AND WEDNESDAY...DRY/VFR.
* WEDNESDAY NIGHT AND THURSDAY...SLIGHT CHANCE OF SNOW SHOWERS/MVFR.
ED F
&&
.MARINE...
300 AM CST
RATHER QUIET PERIOD FOR LAKE MICHIGAN WILL CONTINUE...OUTSIDE OF
THE POTENTIAL FOR SMALL CRAFT CONDS ALONG THE NORTHWEST INDIANA
NEARSHORE WATERS. OTHERWISE WINDS WILL REMAIN SUB-GALE CRITERIA
FOR THE OPEN WATERS.
A TROUGH OF LOW PRESSURE CONTINUES TO LIFT OFF TO THE NORTHEAST...AS
A BROAD RIDGE OF HIGH PRESSURE OVER THE CENTRAL PLAINS STRETCHES
TO THE WESTERN GULF OF MEXICO. THIS HIGH PRESSURE WILL DRIFT EAST
AND BECOME CENTERED ACROSS THE TENNESSEE VALLEY SUNDAY. THIS WILL
PROVIDE AN INFLUENCE ON THE WEATHER OVER LAKE MICHIGAN WITH A
GRADIENT SETTING THE STAGE FOR WINDS TO INCREASE TO 15 TO 25 KT
FROM THE NW/W. A FEW GUSTS TO 30 KT LATE TONIGHT MAY OCCUR...HOWEVER
NOT EXPECTING A WIDESPREAD SITUATION. AS A RESULT OF THE INCREASED
WINDS AND FETCH...WAVES WILL BUILD TO SMALL CRAFT CONDS OR 4 TO 7
FT ALONG THE INDIANA NEARSHORE WATERS THIS AFTERNOON THROUGH
SUNDAY MORNING.
THEN WINDS SLOWLY SHIFT TO THE SW MIDDAY SUN AND SHOULD AID IN
LOWERING WAVES TO ARND 3 TO 5 FT. THEN THE SOUTHWEST FLOW WILL
CONTINUE THROUGH MON AS YET ANOTHER LOW PRESSURE SYSTEM IS
EXPECTED TO LIFT NORTHEAST ACROSS THE UPPER MIDWEST TO NORTH OF
LAKE SUPERIOR MON. A TRAILING FRONTAL BOUNDARY WILL REACH LAKE
MICHIGAN LATER MON. THEN ANOTHER TIGHT PRESSURE GRADIENT DEVELOPS
TUE...HOWEVER GUIDANCE DOES NOT INDICATE THAT WINDS WOULD GUSTS
ABOVE 30 KT.
BEACHLER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ744-LMZ745...3 PM SATURDAY TO 9 AM
SUNDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1202 AM CST SAT DEC 29 2012
.DISCUSSION...
918 PM CST
FOR EVENING UPDATE...
HAVE MADE ONLY MINOR NEAR-TERM TWEAKS TO EARLIER UPDATE FOR TRENDS
WITH FLURRIES/PATCHY FREEZING DRIZZLE WHICH CONTINUE TO AFFECT
PORTIONS OF NORTHERN IL AT MID-EVENING. HAVE ALSO BEEFED UP POPS
ALONG THE IL/IN LAKE MICHIGAN SHORE AREAS SATURDAY...WITH POTENTIAL
FOR LAKE-EFFECT SNOW SHOWERS.
LOW PRESSURE WAS OVER THE LOWER MISSISSIPPI VALLEY THIS EVENING...
WITH A WEAK INVERTED SURFACE TROUGH EXTENDING NORTH THROUGH IL/WI.
THIS TROUGH IS ASSOCIATED WITH RATHER COMPLEX MID/UPPER LEVEL TROUGH
ACROSS THE MIDWEST...WHICH WILL CONTINUE TO MOVE EAST ACROSS THE
REGION OVERNIGHT. 00Z RAOBS FROM DVN/ILX INDICATE THE NATURE OF OUR
FLURRY/FREEZING DRIZZLE ISSUE THIS EVENING...WITH SATURATED LOW
LEVELS UP TO ABOUT 800 MB...WITH COLDEST TEMPS ONLY ABOUT -8 C TO
-10 C WITHIN THAT MOIST LAYER. THIS WAS RESULTING IN MORE
SUPERCOOLED DROPLETS THAN ICE CRYSTALS...AND DRIZZLE/FREEZING
DRIZZLE AT THE SURFACE WITH OCCASIONAL FINE SNOW GRAINS/FLURRIES. AS
MENTIONED IN EARLIER UPDATE...MAIN UPPER TROUGH AXIS AND STRONGER
VORT OVER IA IS EXPECTED TO PROPAGATE EASTWARD ACROSS NORTHERN IL
AFTER MIDNIGHT...WITH GREATER POTENTIAL TO INTRODUCE ICE CRYSTALS
AND THUS A GREATER PROBABILITY OF LIGHT SNOW/FLURRIES RATHER THAN
THE DRIZZLE EXPERIENCED THIS EVENING. HOWEVER...GUIDANCE IS
CONSISTENT IN WEAKENING THIS WAVE AS IT MOVES EAST AND DRYING UP
MODEL GENERATED QPF AS IT REACHES OUR CWA. THUS HAVE CUT BACK POPS A
BIT AND MENTIONED LIGHT SNOW/FLURRIES WITH NO REAL ACCUMULATION FOR
THE OVERNIGHT ACROSS THE AREA.
ON SATURDAY...INVERTED TROUGH/CONVERGENCE AXIS ENDS UP LINGERING
ALONG THE WESTERN SHORE OF LAKE MICHIGAN AS LOW LEVEL WINDS BACK TO
THE NORTH-NORTHWEST THROUGH AFTERNOON. LAKE-INDUCED THERMODYNAMIC
PROFILES IMPROVE THROUGH LATE SATURDAY...WITH SFC-850 DELTA T
INCREASING TO ABOUT 17 C...AND EQUILIBRIUM LEVELS INCREASING TO
NEARLY 10 KFT LATER IN THE DAY/EVENING. THIS SUPPORTS SCENARIO OF
LAKE EFFECT SNOW SHOWER DEVELOPMENT ALONG THE IL SHORE AND INTO
NORTHWEST INDIANA SATURDAY MORNING/AFTERNOON...WITH THE BAND
EVENTUALLY MOVING EAST OF THE IL SHORE AND AFFECTING MAINLY PORTER
COUNTY SATURDAY EVENING. WHILE DAYTIME TEMPS IN THE LOW/MID 30S
ESPECIALLY DOWNWIND OF THE LAKE ARE A LIMITING FACTOR...THE
POTENTIAL FOR SOME MINOR ACCUMULATION APPEARS TO EXIST ALONG THE IL
SHORE...WITH PERHAPS 2-4 INCHES POSSIBLE OVER NORTHERN/NORTHEASTERN
PORTER COUNTY WHERE THE BAND MAY BE MORE FOCUSED LATE IN THE
DAY/EARLY EVENING HOURS. THUS HAVE BUMPED POPS TO LIKELY IN THESE
AREAS AND INCREASED QPF/SNOW AMOUNTS A BIT. WINDS CONTINUE TO BACK
MORE NORTHWEST-WEST AFTER ABOUT 03Z...WHICH SHOULD SHIFT THE FOCUS
FOR LES EAST OF PORTER COUNTY BY LATE SATURDAY EVENING.
RATZER
//PREV DISCUSSION...
644 PM CST
FOR EARLY EVENING UPDATE...
HAVE ADDED A MENTION OF PATCHY FREEZING DRIZZLE TO FORECAST EARLY
THIS EVENING BASED ON CURRENT OBS/REPORT OF DZ/FZDZ ACROSS PARTS OF
NORTHERN IL.
AREA OF VERY LIGHT REFLECTIVITY...<10 DBZ...OVER NORTHERN IL PER
KLOT 88D DATA WAS PRODUCING LIGHT FREEZING DRIZZLE/FLURRIES PER
REGIONAL AWOS REPORTS AS OF 00Z. THIS APPEARS VERY REASONABLE
BASED ON FORECAST SOUNDINGS FROM 18Z NAM/23Z RAP WHICH DEPICT
SATURATED LOW LEVELS UP TO ABOUT 5000-6000 FT OR ABOUT 800
MB...WITH TEMPS ONLY -9/-10C. THIS SUGGESTS WHILE THERE MAY BE ICE
CRYSTALS PRESENT...SUPERCOOLED LIQUID DROPLETS ARE MORE PREVALENT
WHICH IS SUPPORTED BY THE SURFACE REPORTS OF FREEZING DRIZZLE. HAD
A REPORT FROM THE SOUTHEAST CORNER OF LASALLE COUNTY AROUND 6 PM
INDICATING FOG/DRIZZLE AT 30 DEGREES WITH SOME LIGHT ICING ON
OBJECTS. TEMPS GENERALLY RUNNING 30-32 F ACROSS THE AREA SO CANT
RULE OUT SOME TRACE AMOUNTS OF ICE THOUGH WOULD EXPECT MOST WELL-
TRAVELED AND TREATED ROADS WILL BE OK. SIDEWALKS...PARKING
LOTS...WINDSHIELDS OF PARKED CARS MAY SEE A LITTLE LIGHT GLAZING.
HERE AT THE WFO...VERY LIGHT DRIZZLE MORE LIKE A MIST OCCURRING
WITH NO REAL ACCUMULATION OR ICING. BASED ON THIS HAVE ISSUED AN
SPS HIGHLIGHTING THIS...BUT AT THIS TIME HAVE REFRAINED FROM A
WINTER WX ADVISORY.
STRONGER MID-LEVEL WAVE OVER CENTRAL/SOUTHWEST IA IS EXPECTED TO
APPROACH THE AREA LATER THIS EVENING/OVERNIGHT WITH A LITTLE MORE
MID-LEVEL MOISTURE WHICH SHOULD FAVOR MORE NUMEROUS ICE NUCLEI AND A
GREATER PROBABILITY OF LIGHT SNOW/FLURRIES RATHER THAN FREEZING
DRIZZLE.
WITH MOIST LOW LEVELS AND LIGHT WINDS...AREAS OF FOG ALSO NOTED WITH
VISIBILITY GENERALLY 1-3 MILES. SAME REPORT FROM LASALLE COUNTY
INDICATED VIS AS LOW AS 1/2 MILE...THOUGH WITH CLOUD COVER AM NOT
EXPECTING WIDESPREAD VIS UNDER 1 MILE.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* PATCHY DZ/FZDZ WILL TRANSITION TO LGT SN.
* LOW CIGS/VSBYS WILL LINGER THRU OVERNIGHT...WITH CIGS LOWERING
TO IFR. WEST OF ORD/MDW PATCHY LIFR IS POSSIBLE THRU DAYBREAK.
* WINDS WILL REMAIN LGT FROM THE SW AT 5 KT...BECOMING NW ARND
DAYBREAK AND INCREASING TO ARND 10 KT.
BEACHLER
//DISCUSSION...UPDATED 06Z...
VERY MOIST LOW LEVELS WILL REMAIN ACROSS NORTHERN IL/NORTHWEST IN
AIRFIELDS. THIS NORMALLY IS NOT A PROBLEM...HOWEVER WITH THE LACK
OF LIFT OR MIXING...THIS HAS RESULTED IN VERY LOW CIGS ARND
1200-1400FT AGL TO IN SOME LOCATIONS ARND 1000FT AGL. IN ADDITION
WITH A VERY MOIST NEAR SFC ENVIRONMENT AND TEMPS ARND FREEZING TO
JUST BELOW...THE DZ THAT HAS BEEN FALLING WAS BECOMING FZDZ.
GUIDANCE CONTINUES TO INDICATE THAT SOME LIFT WILL BEGIN TO OCCUR
SHORTLY AND SHOULD BE ENOUGH TO CHANGE ANY FZDZ OVER TO LGT SNOW.
IN ADDITION TO THE REDUCED CIGS...VSBYS WILL ALSO BE REDUCED TO
ARND 2-3SM. FURTHER WEST AWAY FROM THE SLIGHTLY WARMER ORD/MDW
AIRFIELDS...VSBYS COULD DIP TO ARND 1SM OVERNIGHT.
AS THE WEAK SYSTEM CONTINUES TO DRIFT EAST...WINDS WILL BEGIN TO
SHIFT W/NW. THIS WILL AID IN SLIGHTLY DRIER AIR FILTERING INTO THE
REGION FROM THE NW. IT DOES NOT APPEAR THAT THIS DRY AIR WILL BE
ENOUGH TO ERODE THE STRATUS LAYER INITIALLY...OVER TIME CIGS/VSBYS
WILL IMPROVE. GUIDANCE CONTINUES TO INDICATE THAT AFT 15Z CIGS
WILL FINALLY PUSH BACK TO LOW END MVFR. HAVE BACKED OFF ONLY A
COUPLE HOURS FROM EARLIER THINKING WITH RESPECT TO VFR CONDS
RETURNING. FEEL TAHT THIS MAY NOT OCCUR UNTIL AFT 00Z SUN.
MEANWHILE THE OTHER ATTENTION IS TO THE POTENTIAL FOR A LAKE
EFFECT SNOW BAND TO DEVELOP. GUIDANCE AND CURRENT THINKING IS THAT
WITH THE EXPECTED WIND FORECAST FROM THE W/NW...THAT ANY LAKE
EFFECT SNOW WOULD BE CONFINED TO GYY OR AIRFIELDS TO THE EAST OF
THIS. THE CONFIDENCE IN ANY IMPACT ON GYY HAS LOWERED SLIGHTLY
FROM EARLIER THINKING...HOWEVER THIS COULD COME BACK INTO PLAY IF
THE WINDS TURN MORE NORTHERLY. IN WHICH CASE GYY COULD BE IMPACTED
SIGNIFICANTLY WITH LGT TO MOD SNOW AND VSBYS DOWN ARND 1SM OR AT
TIMES LOWER.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN CIGS LOWERING TO IFR CONDS.
* MEDIUM CONFIDENCE IN VSBYS FORECAST.
* HIGH CONFIDENCE IN WIND DIR/SPEED FORECAST.
* MEDIUM/HIGH CONFIDENCE IN PRECIP REMAINING AS LGT SN.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
* SUNDAY...DRY/VFR.
* MONDAY...DRY. MVFR POSSIBLE.
* TUESDAY AND WEDNESDAY...DRY/VFR.
* WEDNESDAY NIGHT AND THURSDAY...SLIGHT CHANCE OF SNOW SHOWERS/MVFR.
ED F
&&
.MARINE...
200 PM CST
RELATIVELY LIGHTER WINDS IN PLACE ACROSS THE LAKE EARLY THIS
AFTERNOON AS A FAIRLY WEAK SURFACE PATTERN IS IN PLACE. THE
EXCEPTION IS FOR AREAS NEAR THE MIDDLE PORTIONS OF THE LAKE WHERE
A TIGHTER PRESSURE GRADIENT RESIDES...AND WHERE 10 TO 20 KT WINDS
ARE BEING OBSERVED. WIND DIRECTION REMAINS VARIABLE WITH NORTHERLY
WINDS BEING REPORTED ACROSS THE NORTHERN HALF OF THE LAKE AND
SOUTHERLY WINDS OVER THE SOUTHERN HALF OF THE LAKE. WINDS WILL BE
TURNING TO MORE OF A NORTHERLY DIRECTION TONIGHT AS A WEAK SURFACE
TROUGH SHIFTS EAST ACROSS THE REGION. EXPECT NORTH TO NORTHWEST
WINDS ON SATURDAY WITH AN INCREASE IN SPEEDS...WITH WINDS THEN
TURNING MORE WESTERLY AND DIMINISHING SOME AS HIGH PRESSURE TO THE
WEST SHIFTS EAST THROUGH THE CENTRAL GREAT LAKES SATURDAY NIGHT.
SOUTHWESTERLY WINDS WILL THEN PICK UP SUNDAY THROUGH SUNDAY NIGHT
AS THE NEXT SYSTEM APPROACHES FROM THE WEST.
RODRIGUEZ
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
1233 PM EST SAT DEC 29 2012
.AVIATION...
COLD AIR SPILLING OVER LAKE MICHIGAN COMBINED WITH A LINGERING
INVERTED SURFACE TROUGH IS HELPING TO GENERATE LIGHT SNOW OVER
THE AREA. LAKE EFFECT SNOW IS EXPECTED TO INTENSIFY LATER THIS
EVENING AS CONVECTIVE DEPTHS INCREASE DUE TO CONTINUED CAA. IFR
CONDITIONS AND ACCUMULATIONS OF 1-3 INCHES ARE POSSIBLE AT KSBN.
LOW LEVEL WINDS WILL BACK TO A MORE WESTERLY DIRECTION BY LATER
TONIGHT...QUICKLY SHUTTING OFF LAKE EFFECT PRECIP. FORECAST
SOUNDINGS SUGGEST LOW LEVEL MOISTURE WILL REMAIN TRAPPED BENEATH A
LOWERING INVERSION THOUGH. THIS WOULD SUGGEST LOW END MVFR CIGS
CONTINUING THROUGH THE PERIOD BUT CONFIDENCE IN THIS ASPECT OF THE
FORECAST REMAINS LOW.
&&
.PREV DISCUSSION... /ISSUED 433 AM EST SAT DEC 29 2012/
SHORT TERM...
TODAY THROUGH SUNDAY NIGHT...KEPT THE WINTER WEATHER ADVISORY FOR
FAR SOUTHEAST AREAS GOING UNTIL 7 AM GIVEN THE LATEST SATELLITE AND
RADAR TRENDS. SURFACE OBS AND SURFACE REPORTS OF SNOWFALL
APPROACHING 4 INCHES IN VAN WERT COUNTY SUPPORT TOTAL SNOWFALL
AMOUNTS UP TO 5 INCHES. THE LATEST HRRR SUGGESTS THE SNOW MAY
LINGER A LITTLE LONGER THAN 7 AM THIS MORNING...BUT FOR NOW WILL
KEEP THE EXPIRATION TIME AT 7 AM AND EXTEND LATER IF NEEDED. BACK TO
THE NORTHWEST...LAKE EFFECT SNOW SHOWERS WERE JUST BEGINNING TO
DEVELOP OVER SOUTHERN LAKE MICHIGAN AND SHOULD CONTINUE TO EXPAND IN
COVERAGE. LAKE PARAMETERS NOT IMPRESSIVE...BUT SHOULD SUPPORT LAKE
EFFECT SNOW WITH LIGHT SNOW ACCUMULATIONS. MADE SOME ADJUSTMENTS
ACCORDING TO THE LATEST HIGH RES MODEL DATA TO LAKE EFFECT
TRAJECTORIES AND COVERAGE TODAY AND TONIGHT. OTHERWISE...AS FOR
TEMPERATURES...WENT WITH THE WARMER MET FOR LOWS TONIGHT AND HIGHS
SUNDAY.
LONG TERM...
PROGRESSIVE SPLIT FLW PATTN CONTS UNABATED YET REMAINS POTENTIALLY
PROBLEMATIC AS EVIDENT W/CURRENT SYS OVR THE TN VALLEY THIS MORNING.
GIVEN WORRISOME TREND TWD NEWD PLACEMENT OF DEEPER SRN STREAM WV AND
NWD POSITIONING OF DOWNSTREAM MID LVL CONFLUENCE ZONE SEEN IN ECMWF
AND IN TANDEM W/00Z NAM/UKMET WILL CAUTIOUSLY BREAK FM PRIOR
CONTINUITY WRT POPS MON-MON NIGHT W/CONSENSUS INDICATIONS OF AT
LEAST PARTIAL STREAM PHASING POSSIBLE.
HWVR GRADUAL BLDG OF NEG HGT ANOMALIES CNTRD OVR SE CANADA UPSTREAM
OF BLDG DOWNSTREAM BLOCK OVR GREENLAND AGAIN POINT TO INCREASING
POLAR WEDGING DVLPG MID-LATE PD. IN FACT MULTIDAY MEANS OF GFS MOS
GUIDANCE CONT W/A DOWNWARD TREND ESP THU-FRI PD IN WAKE OF POLAR
FNTL PASSAGE. SOME LK RESPONSE XPCD GIVEN DEGREE/DEPTH OF CAA WING
WED NIGHT AND THU. HWVR SWD CONSENSUS PLACEMENT OF SFC RIDGE CNTR
ACRS THE CNTRL PLAINS WOULD SUGGEST LIMITED RESPONSE IN FACE OF
GENERAL WRLY LL FETCH AND EXTREMELY DRY BNDRY LYR FEED OUT OF RIDGE.
THUS WILL KEEP W/TEMPERED POPS FOR THE TIME BEING. REGARDLESS GIVEN
CORRESPONDING AGREEMENT BTWN GFS/ECMWF WILL UNDERCUT THU/FRI TEMPS
FURTHER IN LIGHT OF BLDG LL THERMAL TROUGH ACRS THE NERN US.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 5 AM EST MONDAY
FOR LMZ043-046.
&&
$$
SHORT TERM...SKIPPER
LONG TERM...T
AVIATION...AGD
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
433 AM EST SAT DEC 29 2012
.SHORT TERM...
TODAY THROUGH SUNDAY NIGHT...KEPT THE WINTER WEATHER ADVISORY FOR
FAR SOUTHEAST AREAS GOING UNTIL 7 AM GIVEN THE LATEST SATELLITE AND
RADAR TRENDS. SURFACE OBS AND SURFACE REPORTS OF SNOWFALL
APPROACHING 4 INCHES IN VAN WERT COUNTY SUPPORT TOTAL SNOWFALL
AMOUNTS UP TO 5 INCHES. THE LATEST HRRR SUGGESTS THE SNOW MAY
LINGER A LITTLE LONGER THAN 7 AM THIS MORNING...BUT FOR NOW WILL
KEEP THE EXPIRATION TIME AT 7 AM AND EXTEND LATER IF NEEDED. BACK TO
THE NORTHWEST...LAKE EFFECT SNOW SHOWERS WERE JUST BEGINNING TO
DEVELOP OVER SOUTHERN LAKE MICHIGAN AND SHOULD CONTINUE TO EXPAND IN
COVERAGE. LAKE PARAMETERS NOT IMPRESSIVE...BUT SHOULD SUPPORT LAKE
EFFECT SNOW WITH LIGHT SNOW ACCUMULATIONS. MADE SOME ADJUSTMENTS
ACCORDING TO THE LATEST HIGH RES MODEL DATA TO LAKE EFFECT
TRAJECTORIES AND COVERAGE TODAY AND TONIGHT. OTHERWISE...AS FOR
TEMPERATURES...WENT WITH THE WARMER MET FOR LOWS TONIGHT AND HIGHS
SUNDAY.
&&
.LONG TERM...
PROGRESSIVE SPLIT FLW PATTN CONTS UNABATED YET REMAINS POTENTIALLY
PROBLEMATIC AS EVIDENT W/CURRENT SYS OVR THE TN VALLEY THIS MORNING.
GIVEN WORRISOME TREND TWD NEWD PLACEMENT OF DEEPER SRN STREAM WV AND
NWD POSITIONING OF DOWNSTREAM MID LVL CONFLUENCE ZONE SEEN IN ECMWF
AND IN TANDEM W/00Z NAM/UKMET WILL CAUTIOUSLY BREAK FM PRIOR
CONTINUITY WRT POPS MON-MON NIGHT W/CONSENSUS INDICATIONS OF AT
LEAST PARTIAL STREAM PHASING POSSIBLE.
HWVR GRADUAL BLDG OF NEG HGT ANOMALIES CNTRD OVR SE CANADA UPSTREAM
OF BLDG DOWNSTREAM BLOCK OVR GREENLAND AGAIN POINT TO INCREASING
POLAR WEDGING DVLPG MID-LATE PD. IN FACT MULTIDAY MEANS OF GFS MOS
GUIDANCE CONT W/A DOWNWARD TREND ESP THU-FRI PD IN WAKE OF POLAR
FNTL PASSAGE. SOME LK RESPONSE XPCD GIVEN DEGREE/DEPTH OF CAA WING
WED NIGHT AND THU. HWVR SWD CONSENSUS PLACEMENT OF SFC RIDGE CNTR
ACRS THE CNTRL PLAINS WOULD SUGGEST LIMITED RESPONSE IN FACE OF
GENERAL WRLY LL FETCH AND EXTREMELY DRY BNDRY LYR FEED OUT OF RIDGE.
THUS WILL KEEP W/TEMPERED POPS FOR THE TIME BEING. REGARDLESS GIVEN
CORRESPONDING AGREEMENT BTWN GFS/ECMWF WILL UNDERCUT THU/FRI TEMPS
FURTHER IN LIGHT OF BLDG LL THERMAL TROUGH ACRS THE NERN US.
&&
.AVIATION...
AN IMPRESSIVE BAND OF SNOW CONTINUES FROM SOUTHERN INDIANA INTO
NORTHEAST INDIANA...EXTENDING INTO THE FWA TERMINAL SITE. THE
HEAVIER SNOW SHOULD STAY SE OF FWA...GIVEN CURRENT TRENDS AND
OBS...WENT WITH A 4 HOUR TEMPO GROUP DOWN TO 3/4 MILE. CURRENT
THINKING IS SNOW SHOULD END BY 15Z...WITH WINDS BECOMING WEST.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER WEATHER ADVISORY UNTIL 7 AM EST THIS MORNING FOR INZ026-
027-032>034.
MI...NONE.
OH...WINTER WEATHER ADVISORY UNTIL 7 AM EST THIS MORNING FOR OHZ016-
024-025.
LM...NONE.
&&
$$
SHORT TERM...SKIPPER
LONG TERM...T
AVIATION...SKIPPER
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
307 PM CST SAT DEC 29 2012
.SYNOPSIS...
THE MORNING UA ANALYSIS SHOWED AN UPPER TROF OVER THE CENTRAL U.S.
THE MAIN TROF AXIS EXTENDED FROM LAKE MICHIGAN THROUGH THE LOWER
OHIO VALLEY WITH A SECONDARY SHORT WAVE OVER WESTERN IOWA. AT THE
SURFACE THE REGION WAS UNDER CYCLONIC FLOW ASSOCIATED WITH LOW
PRESSURE OFF THE MID ATLANTIC COAST. WIDESPREAD LOW CLOUDS OVER THE
AREA THIS MORNING WERE ACCOMPANIED BY SOME LIGHT SNOW. THE CLOUDS
HAVE BEEN STEADILY CLEARING FROM WEST TO EAST THROUGH EARLY THIS
AFTERNOON.
&&
.SHORT TERM...TONIGHT AND SUNDAY...
EXTRAPOLATION OF THE CLEARING LINE HAS THE BACK EDGE OF THE LOW
CLOUDS EAST OF THE CWFA BY 03Z. THIS LOOKS REASONABLE...EXCEPT FOR
NORTHWEST ILLINOIS WHERE MODEL PROGS HOLD HIGHER VALUES OF LOW LEVEL
RH THROUGH MIDNIGHT AS THE LOW LEVEL RIDGE BUILDS INTO THAT AREA
FIRST. HAVE SET THE GRIDS UP FOR A FASTER CLEARING TREND OVER THE
SOUTHWEST HALF OF THE AREA THIS EVENING AND A LITTLE SLOWER TREND IN
THE NORTHEAST. THERE IS ALSO SOME CONCERN FOR STRATUS AND FOG
DEVELOPING JUST EAST OF THE RIDGE AXIS LATE TONIGHT...SIMILAR TO
WHAT HAPPENED IN EASTERN SOUTH DAKOTA THIS MORNING. THE RAP AND NAM
.5KM RH PROGS WERE HINTING AT THIS OCCURRING OVER EASTERN IA AFTER
MIDNIGHT. WHILE THIS CANNOT BE RULED OUT...THERE IS NOT ENOUGH
CONFIDENCE IN ITS OCCURRENCE TO INCLUDE IN THE FORECAST JUST YET.
CLEARING SKIES AND LIGHT WINDS TONIGHT SHOULD ALLOW FOR GOOD
RADIATIONAL COOLING WITH LOWS JUST BELOW ZERO NORTHWEST TO AROUND
10 IN THE SOUTHEAST. THE SURFACE RIDGE AXIS WILL BE EAST OF THE
AREA BY 12Z SUNDAY WITH SOUTH WINDS INCREASING DURING THE DAY AS THE
RIDGE CONTINUES TO MOVE EAST AND A COLD FRONT MOVES INTO NORTHWEST
IOWA. HIGH CLOUDS WILL ALSO BE ON THE INCREASE. TEMPERATURES WILL
BE A CHALLENGE TOMORROW WITH MODELS SHOWING A SHALLOW BUT STRONG
INVERSION OVER THE AREA. HIGHS IN THE MID 20S NORTH TO LOW 30S SOUTH
WERE BASED ON THE SHALLOW MIXING. IF WINDS ARE STRONGER THAN
FORECAST THEN...MIXING WILL BE DEEPER AND THE FORECAST HIGHS WILL BE
ON THE COLD SIDE. DLF
.LONG TERM...MONDAY THROUGH SATURDAY
TWO MAIN CONCERNS IN THIS TIME FRAME ARE THE WEAK CYCLOGENESIS
EVENT WHICH COULD BRING PRECIP TO THE SOUTH LATE MONDAY AND EARLY
TUESDAY...AND THE MUDDLE AMONGST THE MODELS WITH THE UPPER AIR
PATTERN AND SUBSEQUENT DETAILS MIDWEEK.
REGARDING THE MONDAY EVENT...THE NAM IS MORE VIGOROUS AND FURTHER
NORTH WITH DEVELOPING THE LOW THAN THE GFS AND ECMWF...WHICH ARE
WEAKER AND FURTHER SOUTH. HAVE SHADED POPS TO FAVOR THE GFS/ECMWF
SOLUTIONS AND KEPT QPF/SNOW ON THE LIGHT SIDE.
AT MID WEEK...THE EXTENDED MODELS ARE INCONSISTENT AMONG
THEMSELVES AND FROM RUN TO RUN IN HANDLING THE COMPLEX SPLIT FLOW
PATTERN WHICH INCLUDES A SOUTHWEST U.S. CUTOFF AND AN ACTIVE
NORTHERN STREAM. THE 12Z ECMWF MOVES A CLIPPER SYSTEM TO OUR
NORTHEAST WEDNESDAY-THURSDAY...WHICH IS FURTHER NORTH AND EAST AT
THAN AT 00Z WHEN IT WAS PROGGED OVER OUR AREA. MEANWHILE...THE
12Z GFS PROGS THIS CLIPPER SYSTEM FASTER AND EVEN FURTHER
NORTHEAST...SO IT APPEARS THIS WOULD BE A NONEVENT FOR US.
THE GFS DOES HOLD MORE ENERGY BACK OVER THE NORTHERN ROCKIES WHICH
EVENTUALLY CUTS OFF AND DRIFTS ACROSS THE CENTRAL U.S. THROUGH
THE WEEKEND. HOWEVER...THIS GFS RUN IS AN OUTLIER RELATIVE TO THE 00Z
ENSEMBLE MEAN.
THUS FAITH IN ANY OF THESE SOLUTIONS IS LOW. HOWEVER...THE COMMON
THEME IS THAT TROUGHINESS DEVELOPS AND PROGRESSES THROUGH THE
CENTRAL U.S. LATE NEXT WEEK. THERE APPEARS TO BE NO SIGNIFICANT
PRECIP EVENT IN THIS TIME FRAME...AND INDICATIONS ARE THAT
REENFORCING COLD AIR MIGHT GIVE US OUR COLDEST TEMPS SO FAR THIS
SEASON SOMETIME LATE NEXT WEEK INTO THE WEEKEND. WOLF
&&
.AVIATION...
THE BACK EDGE OF THE MVFR CIGS HAS ALREADY CLEARED KCID AND KBRL
WITH THE CURRENT MOVEMENT SUGGESTING CLEARING AT KMLI AROUND 23Z.
MODEL RH PROGS ARE SUGGESTING KDBQ MAY CLEAR OUT SLOWER THAN THE
REST OF THE AREA...SO HELD CEILINGS IN THERE THROUGH MID EVENING.
A SURFACE RIDGE AXIS CURRENTLY OVER EASTERN NEBRASKA AND EASTERN
SOUTH DAKOTA WILL MOVE INTO EASTERN IOWA BY LATE TONIGHT. LATEST
OBSERVATIONS AND SATELLITE IMAGERY WERE SHOWING A NARROW BAND OF
LIFR CIGS AND VSBYS JUST EAST OF THE RIDGE IN EASTERN SOUTH DAKOTA.
SHORT RANGE MODEL GUIDANCE WAS HINTING THAT THESE LOW CLOUDS/FOG
COULD MOVE INTO EASTERN IA WITH THE RIDGE AXIS LATE TONIGHT. THESE
CONDITIONS WERE NOT INCLUDED IN THE TERMINAL FORECASTS JUST YET BUT
MAY BE DURING LATER UPDATES IF TRENDS SUPPORT THEIR INCLUSION.
DLF
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
DLF/WOLF
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
1151 AM CST SAT DEC 29 2012
.UPDATE...
GRIDS WERE UPDATED EARLIER TO EMPHASIZE THE LIGHT SNOW MORE AND TO
DELAY CLEARING UNTIL THE OVERNIGHT HOURS. LIGHT SNOW WAS OCCURRING
WEST INTO CENTRAL IA THIS MORNING AND ALSO NORTHWEST INTO
SOUTHEAST MN WITH VISIBILITIES AT TIMES UNDER 3 MILES. BASED ON
THESE UPSTREAM CONDITIONS WE SHOULD CONTINUE TO SEE SOME
INTERMITTENT LIGHT SNOW AT MOST LOCATIONS THROUGH MOST OF THIS
AFTERNOON AND PICKING UP A TENTH OR TWO TENTHS OF INCH AT SOME
LOCATIONS IS NOT OUT OF THE QUESTION. ALSO BASED ON CURRENT TRENDS
OVER WESTERN IOWA AND THE RAP .5KM RH PROGS...HAVE SLOWED THE
CLEARING TREND DOWN WITH MOST OF THE AREA CLEARING THIS EVENING OR
JUST AFTER MIDNIGHT. AN AREA OF STRATUS/FOG OVER EASTERN SOUTH
DAKOTA AND JUST EAST OF THE SURFACE RIDGE AXIS WILL HAVE HAVE TO
BE WATCHED AS A SPOILER TO THE CLEARING. THESE CLOUDS WERE
EXPANDING TO THE SOUTHEAST THIS MORNING AND THE RAP CLOUD BASE
PRODUCT WAS HINTING AT LOW CEILINGS OVER EASTERN IOWA LATE TONIGHT
AS THE RIDGE AXIS MOVES IN. DLF
&&
.AVIATION...
MVFR CIGS WITH SNOW SHOWERS DROPPING VISIBILITIES TO AROUND 3
MILES AT TIMES CAN BE EXPECTED THROUGH THIS AFTERNOON. TIMING OF THE
BACK EDGE OF THE MVFR CLOUDS SUGGESTS CLEARING AT MOST TAFS SITES
THIS EVENING. HOWEVER...KDBQ MAY BE THE EXCEPTION WITH MODEL LOW
LEVEL RH FIELDS KEEPING HIGHER RH VALUES OVER NORTHEAST
IOWA/NORTHWEST ILLINOIS INTO THE OVERNIGHT HOURS. A SURFACE RIDGE
AXIS CURRENTLY OVER EASTERN NEBRASKA AND EASTERN SOUTH DAKOTA WILL
MOVE INTO EASTERN IOWA BY LATE TONIGHT. LATEST OBSERVATIONS AND
SATELLITE IMAGERY WERE SHOWING A NARROW BAND OF LIFR CIGS AND
VSBYS JUST EAST OF THE RIDGE IN EASTERN SOUTH DAKOTA. SHORT RANGE
MODEL GUIDANCE WAS HINTING THAT THESE LOW CLOUDS/FOG COULD MOVE
INTO EASTERN IA WITH THE RIDGE AXIS LATE TONIGHT. THESE CONDITIONS
WERE NOT INCLUDED IN THE TERMINAL FORECASTS JUST YET BUT MAY BE
DURING LATER UPDATES IF TRENDS SUPPORT THEIR INCLUSION.
DLF
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
555 AM CST SAT DEC 29 2012
.UPDATE...
RECENT RAP TRENDS ARE RAISING QUESTIONS ON HOW FAST THE CLEARING
WILL OCCUR DURING THE AFTERNOON HOURS. THE 0.5KM AGL CONDENSATION
PRESSURE DEFICITS CONTINUE TO INDICATE BREAKS DEVELOPING IN THE
STRATUS THIS AFTERNOON AS STRONGER SUBSIDENCE MOVES IN BEHIND THE
DEPARTING SHORTWAVE. HOWEVER...THE TRUE CLEARING MAY NOT OCCUR
OVER THE EASTERN 60 PERCENT OF THE CWFA UNTIL CLOSER TO SUNSET.
IF CORRECT...THEN THE CLEARING DEVELOPING THIS AFTERNOON WOULD
HAVE TO BE SLOWED DOWN. LIKEWISE...THE LONGER CLOUDS HOLD AROUND
THE SMALLER THE DIURNAL RISE IN TEMPERATURES. GIVEN THE CLOUDS AND
CAA...MOST AREAS WILL REMAIN NEARLY STEADY THROUGH THE DAY OR ONLY
SEE A FEW DEGREES RISE. THE EASTERN THIRD TO HALF OF THE CWFA
WOULD HAVE THE BEST CHANCE AT SEEING TEMPERATURES RISE A COUPLE OF
DEGREES DURING THE DAY.
PERSISTENT FLURRIES BACK INTO CENTRAL IOWA MEANS THAT SCATTERED
FLURRIES WILL BE POSSIBLE ACROSS THE ENTIRE AREA DURING THE
MORNING. BASED ON VISIBILITIES...THERE ARE ISOLD SHSN EMBEDDED
WITHIN THE FLURRIES. THE AREAL COVERAGE ON THE SHSN IS AT BEST 10
PERCENT SO WILL CONTINUE WITH ONLY THE MENTION OF FLURRIES. ..08..
&&
.AVIATION...
CONDITIONS ARE MAINLY MVFR WITH FLURRIES ACROSS IOWA/ILLINOIS BUT
THERE ARE POCKETS OF VFR AND IFR CONDITIONS. THERE ARE ISOLD SHSN
WITH LOCALLY LOWER MVFR CIGS/VSBYS. SUBSIDENCE DEVELOPING AFT
18Z/29 WILL ALLOW THE STRATUS DECK TO DEVELOP BREAKS AS CLEARING
MOVES EAST ACROSS IOWA. VFR CONDITIONS ARE EXPECTED TO DEVELOP BY
OR AFTER 00Z/30 FOR ALL TAF SITES. ..08..
&&
.PREV DISCUSSION... /ISSUED 300 AM CST SAT DEC 29 2012/
SYNOPSIS...
06Z SFC ANALYSIS HAS SEVERAL LOWS IN THE OHIO AND TENNESSEE VALLEYS.
INVERTED TROFS RAN FROM A LOW NEAR KSDF INTO LAKE MICHIGAN AND OHIO.
DEW POINTS WERE IN THE 20S AND 30S OVER THE GREAT LAKES AND
SOUTHEAST WITH SINGLE DIGITS AND TEENS IN THE PLAINS.
SHORT TERM...TODAY AND TONIGHT...
CLEARING TRENDS AND PRECIPITATION POTENTIAL ARE THE IMMEDIATE CONCERNS.
SATELLITE CONTINUES TO SHOW PLENTY OF ST TRAPPED BELOW THE INVERSION.
WHAT APPEARS TO REPRESENT THE BACK EDGE OF THE CLOUDS REASONABLY WELL IS
THE 0.5KM AGL CONDENSATION PRESSURE DEFICITS FROM THE RAP MODEL WITH
SOME LOOSE AGREEMENT WITH THE WRF/GFS AT THE SAME LEVEL. ASSUMING THAT
THIS IS CORRECT...CLOUDS WILL CONTINUE ACROSS THE AREA THROUGH THE
MORNING FOLLOWED BY FAIRLY SIGNIFICANT CLEARING DURING THE AFTERNOON
HOURS AS STRONGER SUBSIDENCE DEVELOPS BEHIND A DEPARTING SHORTWAVE. THE
FAR EASTERN PARTS OF THE CWFA MAY NOT CLEAR UNTIL SHORTLY AFTER SUNSET.
RAP MODEL TRENDS ALSO SHOW NEUTRAL TO WEAK F VECTOR CONVERGENCE ACROSS
MOST THE THE CWFA DURING THE MORNING HOURS WITH LOW CONDENSATION
PRESSURE DEFICITS. THUS SCATTERED FLURRIES SHOULD CONTINUE ACROSS MOST
OF THE CWFA DURING THE MORNING WITH FLURRIES ENDING OVER THE EASTERN
HALF OF THE CWFA DURING THE AFTERNOON.
BASED ON CURRENT TEMPERATURES ACROSS THE AREA...CAA SHOULD ALLOW A
DROP OF ABOUT 1-2 DEGREES PRIOR TO SUNRISE ACROSS THE AREA. CAA
CONTINUES THROUGH THE DAY SO TEMPERATURES WILL REMAIN EITHER STEADY
OR ONLY RISE A FEW DEGREES DURING THE DAY.
TONIGHT...CLEAR OR NEARLY CLEAR SKIES SHOULD BE SEEN ACROSS THE AREA.
THE SNOW FIELD COMBINED WITH LIGHT WINDS ARE EXPECTED TO CREATE A WIDE
RANGE IN TEMPERATURES. SINGLE DIGITS SHOULD BE SEEN ACROSS A MAJORITY OF
THE CWFA. IT IS CONCEIVABLE THAT SUB ZERO READINGS MAY BE SEEN OVER THE
RELATIVELY DEEPER SNOW PACK ACROSS THE NORTHWEST PART OF THE CWFA.
08
LONG TERM...SUNDAY THROUGH NEXT FRIDAY...
MOSTLY DRY TO DRY CONDITIONS WITH WELL BELOW NORMAL TEMPERATURES.
OVERVIEW...INITIALIZATION GOOD WITH LITTLE SENSIBLE WEATHER ISSUES
BESIDES NORMAL WINTER COLD AIR BL MOISTURE ISSUES OVER SNOW PACK.
RUN TO RUN CONTINUITY SUPPORTS A 70/30 BLEND OF GFS/HI-RES ECMWF WITH
NAM TOO FAR NORTH ON MONDAY SYSTEM. PERSISTENCE SUPPORTS WHEN SKIES
ARE FAIR FOR SLIGHTLY LARGER DIURNAL RANGES THAN GUIDANCE.
SUNDAY...LITTLE CHANGE WITH INCREASING HIGH CLOUDS LATE AND OVERNIGHT
WITH MID 20S NORTH TO LOWER TO MIDDLE 30S SOUTHWEST. SUNDAY NIGHT...
SW WINDS OF 5 TO 15 MPH AND MID/HIGH CLOUDS SUPPORT NEARLY STEADY
TEMPERATURES CENTRAL AND SOUTHEAST SECTIONS WITH FALLING TEMPS FAR
NW AS NEXT ARCTIC FRONT ARRIVES.
MONDAY...KEPT LOW POPS SOUTHEAST SECTIONS AS ARCTIC FRONT WITH NW
UPPER FLOW TO CUT OFF MOISTURE TRANSPORT OVER NW SECTIONS.
TEMPERATURES NEARLY STEADY BEHIND FRONT AND FALLING LATE PM IN SE
SECTIONS. LATEST ANALYSIS AND TOOLS SUGGEST ANY SNOW AMOUNTS IN SOUTH
TO BE LESS THAN IN INCH. MONDAY NIGHT...SKIES TO CLEAR WITH
TEMPERATURES CRASHING TO COLDEST READINGS YET THIS WINTER WITH BELOW
ZERO READINGS NW TO LOWER TEENS FAR SE SECTIONS.
TUESDAY THROUGH FRIDAY...COLD NORTHERLY UPPER LEVEL FLOW WITH NEXT
UPPER TROUGH AND ARCTIC FRONT TO ARRIVE LATE WEDNESDAY. THIS SYSTEM
IS TAILORED FOR LATER SHIFTS TO ADD FLURRIES DUE TO VERY COLD AIR
ALOFT AND CYCLONIC CONVERGENT TURNING. MINS FRIDAY AM MAY STILL BE
A CATEGORY OR TWO TOO MILD WITH HI/S STRUGGLING TO MAKE DOUBLE DIGITS
NW SECTIONS THURSDAY AND FRIDAY...15-20 DEGREES BELOW NORMAL.
NICHOLS
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
300 AM CST SAT DEC 29 2012
.SYNOPSIS...
06Z SFC ANALYSIS HAS SEVERAL LOWS IN THE OHIO AND TENNESSEE VALLEYS.
INVERTED TROFS RAN FROM A LOW NEAR KSDF INTO LAKE MICHIGAN AND OHIO.
DEW POINTS WERE IN THE 20S AND 30S OVER THE GREAT LAKES AND
SOUTHEAST WITH SINGLE DIGITS AND TEENS IN THE PLAINS.
&&
.SHORT TERM...TODAY AND TONIGHT...
CLEARING TRENDS AND PRECIPITATION POTENTIAL ARE THE IMMEDIATE CONCERNS.
SATELLITE CONTINUES TO SHOW PLENTY OF ST TRAPPED BELOW THE INVERSION.
WHAT APPEARS TO REPRESENT THE BACK EDGE OF THE CLOUDS REASONABLY WELL IS
THE 0.5KM AGL CONDENSATION PRESSURE DEFICITS FROM THE RAP MODEL WITH
SOME LOOSE AGREEMENT WITH THE WRF/GFS AT THE SAME LEVEL. ASSUMING THAT
THIS IS CORRECT...CLOUDS WILL CONTINUE ACROSS THE AREA THROUGH THE
MORNING FOLLOWED BY FAIRLY SIGNIFICANT CLEARING DURING THE AFTERNOON
HOURS AS STRONGER SUBSIDENCE DEVELOPS BEHIND A DEPARTING SHORTWAVE. THE
FAR EASTERN PARTS OF THE CWFA MAY NOT CLEAR UNTIL SHORTLY AFTER SUNSET.
RAP MODEL TRENDS ALSO SHOW NEUTRAL TO WEAK F VECTOR CONVERGENCE ACROSS
MOST THE THE CWFA DURING THE MORNING HOURS WITH LOW CONDENSATION
PRESSURE DEFICITS. THUS SCATTERED FLURRIES SHOULD CONTINUE ACROSS MOST
OF THE CWFA DURING THE MORNING WITH FLURRIES ENDING OVER THE EASTERN
HALF OF THE CWFA DURING THE AFTERNOON.
BASED ON CURRENT TEMPERATURES ACROSS THE AREA...CAA SHOULD ALLOW A
DROP OF ABOUT 1-2 DEGREES PRIOR TO SUNRISE ACROSS THE AREA. CAA
CONTINUES THROUGH THE DAY SO TEMPERATURES WILL REMAIN EITHER STEADY
OR ONLY RISE A FEW DEGREES DURING THE DAY.
TONIGHT...CLEAR OR NEARLY CLEAR SKIES SHOULD BE SEEN ACROSS THE AREA.
THE SNOW FIELD COMBINED WITH LIGHT WINDS ARE EXPECTED TO CREATE A WIDE
RANGE IN TEMPERATURES. SINGLE DIGITS SHOULD BE SEEN ACROSS A MAJORITY OF
THE CWFA. IT IS CONCEIVABLE THAT SUB ZERO READINGS MAY BE SEEN OVER THE
RELATIVELY DEEPER SNOW PACK ACROSS THE NORTHWEST PART OF THE CWFA.
08
.LONG TERM...SUNDAY THROUGH NEXT FRIDAY...
MOSTLY DRY TO DRY CONDITIONS WITH WELL BELOW NORMAL TEMPERATURES.
OVERVIEW...INITIALIZATION GOOD WITH LITTLE SENSIBLE WEATHER ISSUES
BESIDES NORMAL WINTER COLD AIR BL MOISTURE ISSUES OVER SNOW PACK.
RUN TO RUN CONTINUITY SUPPORTS A 70/30 BLEND OF GFS/HI-RES ECMWF WITH
NAM TOO FAR NORTH ON MONDAY SYSTEM. PERSISTENCE SUPPORTS WHEN SKIES
ARE FAIR FOR SLIGHTLY LARGER DIURNAL RANGES THAN GUIDANCE.
SUNDAY...LITTLE CHANGE WITH INCREASING HIGH CLOUDS LATE AND OVERNIGHT
WITH MID 20S NORTH TO LOWER TO MIDDLE 30S SOUTHWEST. SUNDAY NIGHT...
SW WINDS OF 5 TO 15 MPH AND MID/HIGH CLOUDS SUPPORT NEARLY STEADY
TEMPERATURES CENTRAL AND SOUTHEAST SECTIONS WITH FALLING TEMPS FAR
NW AS NEXT ARCTIC FRONT ARRIVES.
MONDAY...KEPT LOW POPS SOUTHEAST SECTIONS AS ARCTIC FRONT WITH NW
UPPER FLOW TO CUT OFF MOISTURE TRANSPORT OVER NW SECTIONS.
TEMPERATURES NEARLY STEADY BEHIND FRONT AND FALLING LATE PM IN SE
SECTIONS. LATEST ANALYSIS AND TOOLS SUGGEST ANY SNOW AMOUNTS IN SOUTH
TO BE LESS THAN IN INCH. MONDAY NIGHT...SKIES TO CLEAR WITH
TEMPERATURES CRASHING TO COLDEST READINGS YET THIS WINTER WITH BELOW
ZERO READINGS NW TO LOWER TEENS FAR SE SECTIONS.
TUESDAY THROUGH FRIDAY...COLD NORTHERLY UPPER LEVEL FLOW WITH NEXT
UPPER TROUGH AND ARCTIC FRONT TO ARRIVE LATE WEDNESDAY. THIS SYSTEM
IS TAILORED FOR LATER SHIFTS TO ADD FLURRIES DUE TO VERY COLD AIR
ALOFT AND CYCLONIC CONVERGENT TURNING. MINS FRIDAY AM MAY STILL BE
A CATEGORY OR TWO TOO MILD WITH HI/S STRUGGLING TO MAKE DOUBLE DIGITS
NW SECTIONS THURSDAY AND FRIDAY...15-20 DEGREES BELOW NORMAL.
NICHOLS
&&
.AVIATION...
CONDITIONS ARE RANGING FROM VFR TO MVFR WITH FLURRIES. LOCALIZED IFR
CIGS ARE POSSIBLE. MVFR CONDITIONS WITH BORDERLINE IFR CIGS WILL BE
SEEN THROUGH 18Z/29 WITH SCATTERED FLURRIES. SUBSIDENCE DEVELOPING
AFT 18Z/29 IS EXPECTED TO BREAK UP THE 1-2KFT AGL CIGS. VFR
CONDITIONS ARE EXPECTED AFT 00Z/30.
08
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
08/NICHOLS
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
1010 AM EST SAT DEC 29 2012
.SYNOPSIS...
LOW PRESSURE RAPIDLY DEVELOPING ALONG THE CAROLINA COAST WILL
TRACK NORTHEAST OFF CAPE HATTERAS THIS AFTERNOON...AND TO INTO
THE CANADIAN MARITIMES ON SUNDAY. HIGH PRESSURE BUILDS ACROSS THE
MID-ATLANTIC THROUGH SUNDAY NIGHT BEFORE SHIFTING SOUTHEAST ON
MONDAY. THE NEXT DISTURBANCE WILL AFFECT THE REGION LATE MONDAY
NIGHT AND TUESDAY. AN UPPER TROUGH THEN LOOKS TO PERSIST OVER THE
NORTHEASTERN STATES THROUGH THE END OF THE WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 1430Z...PHASING HAS BEGUN WITH PRECIP VOID BETWEEN THE
NORTHERN UPPER LOW OVER THE MIDWEST AND THE COASTAL LOW IN THE
SOUTHERN STREAM FILLING IN QUICKLY ACROSS THE LWX CWA. THE WINTER
WEATHER ADVISORY WAS MAINTAINED FOR ALL AREAS TODAY...WITH A NOTE
THAT FOR CENTRAL MARYLAND AND NORTHERN VIRGINIA THE HIGHER SNOW
TOTALS WOULD BE AT LEAST ABOVE A FEW HUNDRED FEET. BANDS OF
PRECIP...INDICATIVE OF COASTAL CYCLOGENESIS NOW EXTEND FROM THE
MASON-DIXON TO THE OUTER BANKS. THE RAIN SNOW LINE IS OVER THE
WESTERN SUBURBS OF BALT-WASH...IN LINE WITH THE ADVISORY. PRECIP
INTENSITY WILL CONTINUE TO INCREASE AS EVERYTHING SHIFTS EAST WITH
THE COASTAL LOW BOMBING OUT /RAPID PRESSURE FALLS/. IT WOULD NOT
BE SURPRISING TO SEE A QUICK 3 OR 4 INCHES ABOVE 700 FT ALONG THE
MASON DIXON /EAST FROM HAGERSTOWN/ WHERE THE TEMPERATURE PROFILE
SUPPORTS ALL SNOW. WILL CONTINUE MONITORING REPORTS BUT CONFIDENCE
IS FOR STICKING WITH THE ADVISORY THROUGH THE EVENT.
ALREADY LOOKING AT THE BACK EDGE OF PRECIP OVER THE SHENANDOAH
VALLEY WHICH IS IN LINE WITH HRRR GUIDANCE AND SATELLITE WV
IMAGERY OF THE DRY SLOT. PLAN WAS TO CANCEL ADVISORY FOR SWRN
ZONES EAST OF THE ALLEGHENY FRONT AROUND MIDDAY AND THAT LOOKS TO
BE ON TRACK. THE RADAR COVERAGE WILL PIVOT A BIT MORE NW TO SELY
AS THE LOW MOVES NORTHEAST...SO PRECIP IS EXPECTED TO CONTINUE INTO THE
MID AFTERNOON FOR NERN ZONES /I.E. BALTIMORE REGION/.
ADVISORY EXTENDED THROUGH TONIGHT FOR WEST OF THE ALLEGHENY FRONT
WITH UPSLOPE SNOW CONTINUING IN EARNEST THROUGH TONIGHT...LIGHT
SNOW AND FLURRIES FOR SUNDAY. 5-7 INCHES OUT THERE /24 HR ADVISORY
CRITERION FOR THE WESTERN FIVE COUNTIES IS 8 INCHES/.
WIND TONIGHT...COLD AIR ADVECTION AND THE RAPIDLY DEVELOPING LOW
OFF THE MID ATLANTIC COAST WILL PRODUCE STRONG GUSTS OVERNIGHT.
NEAR WIND ADVISORY LEVELS /46 MPH GUSTS/ FOR THE RIDGELINES...BLUE
RIDGE AND WEST...WITH 30 TO 35 MPH GUSTS AT LOWER ELEVATIONS
INCLUDING THE BALT-WASH METRO. WIND CHILLS INTO THE TEENS
EVERYWHERE EXCEPT LOWER SRN MD /AND SINGLE DIGITS IN THE POTOMAC
HIGHLANDS/.
&&
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
SUNDAY APPEARS TO BE THE NICER DAY OF THE WEEKEND...BUT ONLY IF YOU
ARE LOOKING OUTSIDE FROM INDOORS DUE TO WIND. A MOSTLY SUNNY SKY IS
EXPECTED... BUT HIGHS WILL NOT GET OUT OF THE 30S IN MOST
AREAS...AND A BITING BREEZE WILL YIELD WIND CHILLS IN THE 20S MOST
OF THE DAY. ONLY PRECIP IN PLAY IS UPSLOPE...WHICH WILL BE
TAPERING OFF BY EARLY AFTERNOON SUNDAY. WINDS SHOULD ALSO TAPER
OFF AFTER SUNSET...LEADING TO A CHILLY SUNDAY NIGHT WITH
WIDESPREAD LOWS AROUND 20 AWAY FROM THE CITIES.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
NEW YEARS EVE WILL FEATURE A BRIEF BREAK BETWEEN SYSTEMS IN
FAST-MOVING ZONAL FLOW...WITH PRECIP CHANCES RETURNING TO THE
ALLEGHENY FRONT BY LATE MONDAY AFTERNOON AND ESPECIALLY MONDAY
NIGHT. HAVE REMOVED ALL POPS EAST OF THE HIGHLANDS THOUGH.
UPPER SUPPORT DOES ARRIVE GRADUALLY ON NEW YEARS DAY. ALTHOUGH THE
OPERATIONAL MODELS ARE SHOWING THE BULK OF THE PRECIP TO THE SOUTH
OF THE AREA...ENSEMBLES LEND ENOUGH SUPPORT TO RETAIN CHANCE POPS
JUST ABOUT EVERYWHERE. BROAD BRUSHED MOST OF THE AREA WITH RAIN OR
SNOW WORDING...BUT HIGHS ARE SOLIDLY ABOVE FREEZING SO RIGHT NOW
THIS DOES NOT APPEAR TO BE A BIG DEAL. WORTH MONITORING THOUGH.
MODEL AND ENSEMBLE TRENDS ARE TO PUSH THE PRECIP OUT TUESDAY
NIGHT...AND SO HAVE FOLLOWED SUIT BY LEAVING ONLY A SLIGHT CHANCE
FOR SNOW.
THE SECOND HALF OF THE WEEK WAS LEFT UNCHANGED FOR NOW DUE TO
UNCERTAINTY IN THE DETAILS OF THE PATTERN. THERE COULD BE A WEAK
CLIPPER SYSTEM TOWARD THE END OF THE WEEK...BUT WHAT DEFINITELY
APPEARS LIKELY IS THINGS GETTING EVEN COLDER THAN THEY ARE ALREADY.
ENSEMBLES SHOW HIGH PRESSURE OVERTAKING MUCH OF THE COUNTRY...AND
THIS WILL PUMP COLD AIR INTO A LARGE PART OF THE CONUS. THE GFS
ENSEMBLE MEAN MAX TEMP FOR FRIDAY IS BELOW FREEZING OVER OUR ENTIRE
AREA. OUR FORECAST IS NOT QUITE THAT COLD YET SINCE THESE THINGS DO
SEEM TO SOMETIMES TREND WARMER OVER TIME. THE LAST COMPLETELY
SUBFREEZING DAY /HIGH BELOW 32/ AT DCA WAS NEARLY TWO YEARS
AGO...JAN 22 2011.
&&
.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
IFR CIGS AND VSBYS THROUGH THE AFTERNOON...ENDING EARLY AFTERNOON
FOR KCHO...WITH LIFR AT TIMES IN SNOW /NW OF BWI AND DCA/.
PRECIPITATION WILL END FROM SOUTHWEST TO NORTHEAST DURING THROUGH
THE REST OF THE DAY. BEHIND THE SYSTEM...VFR CONDITIONS RETURN
AND WINDS SHIFT TO THE NORTHWEST GUSTING TO 25 KT TONIGHT.
GUSTY WINDS ON SUNDAY...WITH NW WIND GUSTS 25 TO 30 KT.
PRECIPITATION... SNOW WITH SOME RAIN...POSSIBLE AT ALL TERMINALS
ON TUESDAY.
&&
.MARINE...
SOUTHEAST FLOW 10 TO 15 KT THROUGH THE EARLY AFTERNOON...SWITCHING
WLY/NWLY THIS AFTERNOON AND INCREASING AS A RAPIDLY DEVELOPING STORM
SYSTEM MOVES FROM THE CAROLINA COAST TO A POSITION OFF THE MID-
ATLANTIC COAST. GRADIENT STRENGTHENS AS THE STORM INTENSIFIES. SCA
IS ALREADY IN EFFECT FOR TONIGHT. LOCAL ENHANCEMENT DOWN THE BAY
COULD BRING WIND GUSTS CLOSE TO GALE FORCE TONIGHT.
EXTENDED SCA THROUGH SUNDAY FOR ALL THE WATERS AS GUSTY WINDS ARE
EXPECTED TO CONTINUE. THOSE WINDS MAY TAPER OFF ON THE TIDAL POTOMAC
BY EARLY AFTERNOON BUT JUST CARRIED IT FOR ALL ZONES FOR NOW. SCA
MAY NEED TO BE EXTENDED INTO SUNDAY NIGHT FOR THE LOWER MARYLAND BAY
AND PERHAPS LOWERMOST TIDAL POTOMAC.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WINTER WEATHER ADVISORY UNTIL 7 AM EST SUNDAY FOR MDZ501.
WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR
MDZ003>007-009-010.
WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
MDZ502.
VA...WINTER WEATHER ADVISORY UNTIL 7 AM EST SUNDAY FOR VAZ503.
WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR VAZ028-
030-031-042-501.
WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
VAZ025>027-029-038>040-504.
WV...WINTER WEATHER ADVISORY UNTIL 7 AM EST SUNDAY FOR WVZ501-503-
505.
WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR
WVZ051>053.
WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
WVZ050-055-502-504-506.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 PM EST SUNDAY
FOR ANZ530>543.
&&
$$
SYNOPSIS...JCE/BPP
NEAR TERM...BAJ/BPP
SHORT TERM...JCE
LONG TERM...JCE
AVIATION...JCE/BAJ/BPP
MARINE...JCE/BAJ/BPP
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
406 PM EST SAT DEC 29 2012
.SHORT TERM...THIS EVENING AND TONIGHT
SURFACE OBSERVATIONS UPSTREAM OVER NORTHERN LAKE HURON SUPPORT THE
MAIN STRUCTURE OF LAKE HURON AGGREGATE TROUGH HAS BROKEN DOWN. HIGH
RESOLUTION MODEL DATA HAS BEEN DEPICTING A SOLUTION THAT SUPPORTED
TRACKING A MESOVORTEX OR WELL ORGANIZED LOW LEVEL CONVERGENCE BANDING
STRUCTURE INTO PORTIONS OF HURON COUNTY AND THE NORTHERN THUMB AS
THE NORTHWESTERLY FLOW BECAME DOMINANT. WITH NO REDUCTION IN SFC
VISIBILITIES EARLIER THIS AFTERNOON FOR THE UPSTREAM SHORELINE AREAS
OF NORTHERN LOWER THIS IDEA FOR A MESOLOW CAN NOW BE ABANDONED. THIS
IS IMPORTANT BECAUSE THE IDEA OF LONGER DURATION DUE TO PROPAGATION
EFFECTS CAN BE APTLY BE DISCOUNTED AS WELL.
THE LAKE EFFECT EVENT NOW ANTICIPATED WILL BE A BRIEF
ONE...RELEGATED TO DEVELOPED ACTIVITY ADVECTING THROUGH ON THE LEAD
BACKED NORTHEASTERLY PUSH...VERY MUCH OF A SQUALL NATURE. SATELLITE
IMAGERY HAS SHOWN LOW CLOUD STRATOCUMULUS AGGRESSIVELY PUSHING INTO
EASTERN HURON COUNTY/MARKED WITH A GRAVITY STRUCTURE DURING THE PAST
HOUR. KDTX/KAPX BEAMS ARE BOTH OVERSHOOTING THE ACTIVITY WITH THE
AREAS OF INTEREST AT ROUGHLY 90 NM OR APPX 10 KFT AGL ON THE .5
DEGREE. ENVIRONMENT CANADA EXETER RADAR IS IN A BETTER LOCATION AND
IS SHOWING 25-30 DBZ EXTENDING INLAND/EAST OF BAD AXE. PLACED SOME
CALLS TO FIELD REPORTS AND DID MANAGE TO GET A CREDIBLE REPORT OF .5
INCH PER ONE HALF HOUR IN PORT HOPE. HOWEVER...THE SNOW HAD ALREADY
BEEN ON THE WANE SUGGESTING A TENUOUS SETUP. VARIOUS HI RESOLUTION
FLAVORS OF NWP - 3.5KM ARW WRF - 4 KM NMM SPC WRF - 3KM HRRR AND 13
KM RAP NOW AGREE IN SWEEPING THIS LAKE EFFECT THROUGH DURING 19-22Z.
DURATION OF SNOWFALL SHOULD ONLY LAST 1-1.5 HOUR AT MOST BEFORE
PUSHING BACK INTO LAKE HURON. THEREFORE...THE FORECAST WILL CALL FOR
A CONDITIONAL...UP TO 2 INCHES FOR LOCATIONS OF HURON/SANILAC
COUNTIES EAST OF A LINE FROM BAD AXE TO SANDUSKY.
OTHERWISE...LARGE SCALE MIDLEVEL TROUGH IS NOW ADVANCING INTO THE
WESTERN PORTIONS OF LOWER MICHIGAN. THE OLD 850-700MB DEFORMATION
FORCING THAT IS A CARRYOVER FROM LAST NIGHT HAS BEEN EFFICIENT IN
GENERATING AFTERNOON LIGHT SNOW/FLURRIES HERE ACROSS MUCH OF THE
REGION. HIGHEST REFLECTIVITIES HAVE BEEN IN EXCESS OF 20 DBZ BUT IS
LACKING IN ANY BITE/MORE OF A FUNCTION OF A FEW LARGE FLAKES. NOT
EXPECTING MUCH ACCUMULATION WITH THIS BEFORE DISSIPATING.
LOWS TONIGHT ARE VERY TRICKY AND DEPENDENT ON CLOUD COVER. DID STEER
THE FORECASTED LOWS A LITTLE TOWARDS RECENT GUIDANCE...AROUND 20
DEGREES.
&&
.LONG TERM...SUNDAY THROUGH SATURDAY
QUIET WEATHER EXPECTED SUNDAY/SUNDAY NIGHT AS HIGH PRESSURE BUILDS
ACROSS THE EASTERN CONUS W/ THE NORTHERN EXTENT OF SURFACE RIDGING
PROVIDING RELATIVELY LIGHT WINDS AND PARTLY CLOUDY SKIES FOR THE
SOUTHERN GREAT LAKES. AS THE RIDGE AXIS PROGRESSES EAST OF THE AREA
ON MONDAY...CLOUDS/WINDS WILL INCREASE WITH THE APPROACH OF THE NEXT
DISTURBANCE. THIS SYSTEM WILL CROSS NORTH OF THE AREA...BUT PUSH A
COLD FRONT THROUGH THE REGION BY MONDAY NIGHT.
THE STORM SYSTEM THAT HAS BASICALLY THE ONLY POTENTIAL TO BRING
NOTEWORTHY SNOW TO THE AREA IS CURRENTLY SPINNING OVER CALIFORNIA.
OF THE 12Z MODEL SUITE...THE NAM12 IS THE ONLY MODEL TRYING TO
MAINTAIN SOME INTEGRITY TO THIS WAVE AS IT EJECTS NORTHEAST OUT OF
THE FOUR CORNERS ALONG THE MEAN CENTRAL CONUS UPPER TROUGH INTO A
LARGELY CONFLUENT UPPER FLOW OVER THE NORTHEAST QUADRANT OF THE
NATION.
IN ADDITION TO SHOWING THE STRONGEST SOLUTION FOR THIS SHORTWAVE
ITSELF...THE OTHER MAIN DIFFERENCE IS THE HANDLING OF SHORTWAVE
ENERGY DIGGING SOUTH/SOUTHEAST INTO POLAR VORTEX NEAR HUDSON BAY AS
THE NAM..THROUGH THIS PROCESS...MAINTAINS A MORE NORTHERN POSITION
TO THIS FEATURE AND ALLOWS ITS "STRONGER" WAVE TO EJECT FURTHER
NORTH INTO THE OHIO VALLEY/SOUTHERN GREAT LAKES AND BRING SEVERAL
INCHES OF SNOW TO PARTS OF LOWER MICHIGAN.
WHILE THE ARCTIC JET ENERGY THAT WILL EVENTUALLY DICTATE THE
EVOLUTION OF THE HUDSON BAY LOW AND THE STEERING OF THE SOUTHERN
STREAM WAVE HAS YET TO BE SAMPLED VERY WELL...IT IS HARD TO IGNORE
SUCH A STRONG MODEL CONSENSUS AGAINST THE NAM...WHICH CALLS FOR
STRONGER AMPLIFICATION OF THE NORTHERN STREAM OVER EASTERN CANADA.
THIS SCENARIO WILL SHUNT THE SOUTHERN SYSTEM ON A TRACK WELL SOUTH
OF THE AREA AND KEEP ANY NOTABLE PRECIPITATION CONFINED TO THE
TENNESSEE VALLEY AND POINTS SOUTH WITH IT WITH JUST SCATTERED SNOW
SHOWERS OVER LOWER MICHIGAN WITHIN THE CYCLONIC NORTHWEST FLOW AS
COLDER AIR SURGES THROUGH THE GREAT LAKES WITH THE EVOLUTION OF THIS
NORTHERN SYSTEM.
WILL MAINTAIN A FORECAST BASED ON THIS IDEA...WITH LITTLE/NO CHANCE
OF SIGNIFICANT SNOW AND ALSO A DECENT COOL DOWN AS THIS STRONG
EASTERN CANADA UPPER LOW/TROUGH ALLOWS FOR A DECENT PENETRATION OF
POLAR/MODIFIED ARCTIC AIR INTO THE REGION. SO...AFTER EDGING BACK TO
HIGH TEMPERATURES IN THE 30S ON MONDAY...20S WILL BE THE RULE MUCH
OF THE UPCOMING WEEK WITH LOWS IN THE SINGLE DIGITS/TEENS MUCH OF
THE TIME.
&&
.MARINE...
A MODEST INCREASE TO THE SURFACE PRESSURE GRADIENT COMBINED WITH
WINDS ROTATING TO A MORE ONSHORE DIRECTION WILL MAINTAIN A MODERATE
BREEZE ACROSS CENTRAL AND SOUTHERN LAKE HURON TODAY. WAVE HEIGHTS
ARE ALREADY RAMPING UP INTO THE 4 TO 7 FOOT RANGE THIS AFTERNOON.
SMALL CRAFT ADVISORIES REMAIN IN EFFECT FROM OUTER SAGINAW BAY TO
PORT HURON THROUGH TONIGHT.
A MODERATE SOUTHWEST FLOW WILL DEVELOP SUNDAY NIGHT INTO MONDAY AS
THE SURFACE PRESSURE GRADIENT TIGHTENS OVER AREA WATERS AS LOW
PRESSURE CROSSES NORTH OF THE REGION. GUSTY NORTHWEST WINDS WILL
DEVELOP BY MIDWEEK NEXT WEEK AS COLDER AIR SPREADS INTO THE GREAT
LAKES REGION IN THE WAKE OF THIS SYSTEM.
&&
.AVIATION...ISSUED 1234 PM EST SAT DEC 29 2012
//DISCUSSION...
RESIDUAL MIDLEVEL DYNAMICS FROM AN EARLIER FRONTAL ZONE IS NOW
ADVECTING INTO SOUTHERN PORTIONS OF SOUTHEASTERN MICHIGAN FROM THE
NORTHWEST. FOR NOW...FLOW TRAJECTORY AND LATEST TRENDS SUGGESTS
PRECIPITATION WILL NOT IMPACT KFNT AND KMBS. BEHAVIOR OF BASE
REFLECTIVITY PRODUCTS HAS BEEN INTERESTING...SUGGESTING THAT
SEEDER FEEDER PROCESSES ARE IN PLAY TO HELP GENERATE A MODESTLY
BURGEONING AREA OF LIGHT SNOW. LACK OF ANY TANGIBLE DRY AIR
ADVECTION FOLLOWING LAST NIGHTS SYSTEM CERTAINLY SUPPORTS THIS
IDEA. EXPECTATIONS ARE FOR A PERIOD OF MVFR TYPE SNOW ACTIVITY
WITH SOME IFR VISIBILITIES RESULTING DUE TO THE ADDITION OF BR/HZ.
THE LAKE EFFECT SNOW ACTIVITY THAT IS EXPECTED TO CRASH INTO
PORTIONS OF THE THUMB LATER ON...SHOULD BE SUBSEQUENTLY SWEPT
EASTWARD. PERSISTENT NORTHWESTERLY...CYCLONIC FLOW SUPPORTS
STRATOCUMULUS THROUGHOUT THE TAF CYCLE.
FOR DTW...MVFR TO OCCASIONAL IFR VISBY LIGHT SNOW IS EXPECTED OVER
THE NEXT 3 TO 4 HOURS. THE REASON FOR IFR VISBY IS DUE TO THE
PERSISTENCE OF BR/HZ. CEILING HEIGHTS ARE EXPECTED TO REMAIN MVFR
THROUGHOUT THE PERIOD. MODEL DATA IS SUGGESTING IFR CEILING HEIGHTS
LATE TONIGHT/TOMORROW MORNING BUT ATTM...SUSPECT THE MODELS ARE
OVERDONE ON THE AMOUNT OF NEAR SURFACE MOISTURE.
//DTW THRESHOLD THREATS...
* HIGH CONFIDENCE CEILINGS WILL BE BELOW 5000 FT.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
SMALL CRAFT ADVISORY...OUTER SAGINAW BAY...UNTIL 1 AM SUNDAY.
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
SANILAC...UNTIL 7 AM SUNDAY.
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT SANILAC TO PORT
HURON...FROM 10 PM SATURDAY TO 10 AM SUNDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
SHORT TERM...CB
LONG TERM....DG
MARINE.......CB
AVIATION.....CB
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
356 PM EST SAT DEC 29 2012
.SYNOPSIS...
ISSUED AT 321 PM EST SAT DEC 29 2012
ANOTHER ROUND OF MOSTLY LIGHT SNOW WILL OCCUR OVERNIGHT. UP TO AN
INCH OR TWO OF ACCUMULATION WILL BE POSSIBLE ALONG THE LAKESHORE
NEAR SOUTH HAVEN. AFTER A RATHER DRY SUNDAY AND SUNDAY NIGHT...THE
COMING WORK WEEK WILL BE COLDER THAN NORMAL WITH SLIGHT CHANCES FOR
SNOW MAINLY NEAR THE LAKE SHORE EACH DAY.
&&
.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 321 PM EST SAT DEC 29 2012
AS NOTED IN THE PREVIOUS FORECAST UPDATE DISCUSSION...WE EXPECT
A SHOT OF LAKE ENHANCED SNOW EARLY TONIGHT MAINLY SOUTH OF HOLLAND.
THE BEST TIMEFRAME LOOKS BETWEEN 10 PM AND 2 AM. MOST RECENT RUNS
OF THE RAP HAVE BACKED TOTAL ACCUMULATIONS AT SOUTH HAVEN DOWN TO AN
INCH OR LESS COMPARED TO EARLIER AMOUNTS OF 2+ INCHES. HOWEVER...
PREFER TO MATCH UP WITH SLIGHTLY HIGHER AMOUNTS ADVERTISED BY IWX TO
ACCOUNT FOR LAKE MOISTURE THAT MAY NOT BE HANDLED WELL BY THE MODELS.
OTHERWISE...FEW CHANGES WERE MADE TO THE FORECAST. DID RAISE POPS
AND SNOW AMOUNTS MONDAY AND MONDAY NIGHT OVER OUR NRN ZONES TO
ACCOUNT FOR COLD FRONT DROPPING SOUTH THROUGH THE AREA AND TO BETTER
MATCH WITH APX TO OUR NORTH.
.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 321 PM EST SAT DEC 29 2012
THE FOCUS OF THE FORECAST CONTINUES TO BE CENTERED ON THE ARCTIC AIR
MASS THAT IS EXPECTED TO COME DOWN AND THE RESULTING LAKE EFFECT
SNOW SHOWER CHCS.
TUE AND TUE NIGHT LOOK RATHER QUIET. SOME LIGHT LAKE EFFECT WILL BE
POSSIBLE ON TUE AS WE SHOULD SEE A WEAK UPPER TROUGH MOVE BY.
SUFFICIENT INSTABILITY OVER THE LAKE WILL ALSO BE PRESENT WITH H850
TEMPS AROUND -10 TO -12C. THE LAKE EFFECT POTENTIAL WILL DIMINISH
LATE TUE AND MAINLY DRY CONDITIONS ARE EXPECTED TUE NIGHT WITH
RIDGING BUILDING IN.
WE ARE STILL EXPECTING A FAIRLY VIGOROUS UPPER TROUGH TO DROP DOWN
IN THE REGION WED-THU. THIS WILL BRING A THREAT OF SYNOPTIC SNOW
ALONG WITH SOME LAKE ENHANCEMENT/POTENTIAL AS COLDER AIR WILL FOLLOW
IN BEHIND IT. THE MODELS HAVE BEEN STRUGGLING WITH THE EXACT TRACK
WHICH WILL HAVE IMPLICATIONS ON HOW MUCH SNOW FALLS AND WHERE IT
FALLS. THE LATEST MODELS SHOW IT TRACKING NORTH OF THE AREA AND
HAVING MOST OF THE SNOW NORTH OF IT. THE FLOW IS ALSO IMPORTANT DUE
TO LAKE ENHANCEMENT POTENTIAL. FOR NOW WE HAVE A CHC OF SNOW SHOWERS
EVERYWHERE. THIS WILL HAVE TO BE FINE TUNED.
THE NOTEWORTHY CHANGE IN THE MODELS IS A TREND TOWARD A SHORTER STAY
FOR THE ARCTIC AIR. THE MODELS ARE MORE PROGRESSIVE THAN PREVIOUS
RUNS WITH THE UPPER TROUGH AND ARCTIC AIR. THIS IS LIKELY HAVING TO
DO WITH THE SPLIT FLOW THAT DEVELOPS. THE UPPER TROUGH IS EXPECTED
TO BE GONE BY THU NIGHT. THIS WOULD MEAN LESS LAKE EFFECT POTENTIAL.
BY FRI...THE AIR AT H850 IS NOT EVEN COLD ENOUGH FOR LAKE EFFECT. WE
END UP ONCE AGAIN IN NO MANS LAND BETWEEN THE JET STREAMS. THIS
WOULD BRING US SEASONABLE TEMPERATURES WITH LITTLE IF ANY PCPN CHCS.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1250 PM EST SAT DEC 29 2012
THE TWO MAIN ITEMS OF INTEREST WITH THIS SET OF FCSTS IS THE
CURRENT SNOW MOVING OUT THIS AFTERNOON AND THEN LAKE EFFECT TRENDS
FOR TONIGHT AND TOMORROW.
THE AREA OF LIGHT SNOW WAS SOUTHEAST OF A LINE FROM KALAMAZOO TO
GRAND RAPIDS TO ALMA AS OF 1745Z THIS AFTERNOON. THIS SNOW IS
PRODUCING LOW MVFR TO IFR CONDITIONS. THIS IS EXPECTED TO MOVE OUT
TO THE SE OF ALL THE TERMINALS BY AROUND 21Z THIS AFTERNOON. SOME
SCATTERED VFR CONDITIONS ARE POSSIBLE BEHIND THE SNOW FOR A SHORT
TIME. MORE MVFR CIGS AROUND 2500 FT ACROSS CENTRAL LOWER MICHIGAN
WILL MOVE IN LATER THIS AFTERNOON.
LAKE EFFECT SNOW SHOWERS WILL GRADUALLY MOVE IN LATE THIS
AFTERNOON AND MORE SO TONIGHT AS NNE WINDS GRADUALLY SHIFT TO THE
WEST OVERNIGHT TONIGHT. LAKE EFFECT WILL SPREAD ACROSS THE
LAKESHORE FIRST LATE AFTERNOON/EARLY EVENING...THEN INLAND
THEREAFTER. MAINLY MVFR CIGS AND VSBYS ARE EXPECTED WITH SOME SPOTTY
IFR POSSIBLE CLOSER TO THE LAKESHORE. SNOW SHOWERS WILL SLOWLY
DIMINISH THROUGH 18Z SUN THEN BEFORE ENDING AFTER THE TAF PERIOD.
&&
.MARINE...
ISSUED AT 351 PM EST SAT DEC 29 2012
NO CHANGES WERE MADE TO THE INHERITED FORECAST. LATEST LOCAL RUN
OF THE GLERL KEEPS WAVES BELOW SMALL CRAFT CRITERIA UNTIL WELL
AFTER MIDNIGHT. THIS IS A FEW HOURS AFTER THE 10 PM OFFICIAL START
OF THE SMALL CRAFT ADVISORY. THERE MAY BE A BRIEF PERIOD OF SUB-
ADVISORY WAVES SUNDAY AFTERNOON. HOWEVER THIS WILL BE SHORT-LIVED
AS WINDS NEAR OR AT GALE FORCE ARE EXPECTED BOTH SUNDAY NIGHT AND
MONDAY.
&&
.HYDROLOGY...
ISSUED AT 321 PM EST SAT DEC 29 2012
NO HYDRO CONCERNS DUE TO VERY LITTLE QPF. RIVER ICE WILL BE LIKELY
TO DEVELOP BY THE END OF THE COMING WORK WEEK.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST SUNDAY
FOR LMZ844>849.
&&
$$
SYNOPSIS...TJT
SHORT TERM...TJT
LONG TERM...NJJ
AVIATION...NJJ
HYDROLOGY...TJT
MARINE...TJT
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
321 PM EST SAT DEC 29 2012
.SYNOPSIS...
ISSUED AT 321 PM EST SAT DEC 29 2012
ANOTHER ROUND OF MOSTLY LIGHT SNOW WILL OCCUR OVERNIGHT. UP TO AN
INCH OR TWO OF ACCUMULATION WILL BE POSSIBLE ALONG THE LAKESHORE
NEAR SOUTH HAVEN. AFTER A RATHER DRY SUNDAY AND SUNDAY NIGHT...THE
COMING WORK WEEK WILL BE COLDER THAN NORMAL WITH SLIGHT CHANCES FOR
SNOW MAINLY NEAR THE LAKE SHORE EACH DAY.
&&
.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 321 PM EST SAT DEC 29 2012
AS NOTED IN THE PREVIOUS FORECAST UPDATE DISCUSSION...WE EXPECT
A SHOT OF LAKE ENHANCED SNOW EARLY TONIGHT MAINLY SOUTH OF HOLLAND.
THE BEST TIMEFRAME LOOKS BETWEEN 10 PM AND 2 AM. MOST RECENT RUNS
OF THE RAP HAVE BACKED TOTAL ACCUMULATIONS AT SOUTH HAVEN DOWN TO AN
INCH OR LESS COMPARED TO EARLIER AMOUNTS OF 2+ INCHES. HOWEVER...
PREFER TO MATCH UP WITH SLIGHTLY HIGHER AMOUNTS ADVERTISED BY IWX TO
ACCOUNT FOR LAKE MOISTURE THAT MAY NOT BE HANDLED WELL BY THE MODELS.
OTHERWISE...FEW CHANGES WERE MADE TO THE FORECAST. DID RAISE POPS
AND SNOW AMOUNTS MONDAY AND MONDAY NIGHT OVER OUR NRN ZONES TO
ACCOUNT FOR COLD FRONT DROPPING SOUTH THROUGH THE AREA AND TO BETTER
MATCH WITH APX TO OUR NORTH.
.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 321 PM EST SAT DEC 29 2012
THE FOCUS OF THE FORECAST CONTINUES TO BE CENTERED ON THE ARCTIC AIR
MASS THAT IS EXPECTED TO COME DOWN AND THE RESULTING LAKE EFFECT
SNOW SHOWER CHCS.
TUE AND TUE NIGHT LOOK RATHER QUIET. SOME LIGHT LAKE EFFECT WILL BE
POSSIBLE ON TUE AS WE SHOULD SEE A WEAK UPPER TROUGH MOVE BY.
SUFFICIENT INSTABILITY OVER THE LAKE WILL ALSO BE PRESENT WITH H850
TEMPS AROUND -10 TO -12C. THE LAKE EFFECT POTENTIAL WILL DIMINISH
LATE TUE AND MAINLY DRY CONDITIONS ARE EXPECTED TUE NIGHT WITH
RIDGING BUILDING IN.
WE ARE STILL EXPECTING A FAIRLY VIGOROUS UPPER TROUGH TO DROP DOWN
IN THE REGION WED-THU. THIS WILL BRING A THREAT OF SYNOPTIC SNOW
ALONG WITH SOME LAKE ENHANCEMENT/POTENTIAL AS COLDER AIR WILL FOLLOW
IN BEHIND IT. THE MODELS HAVE BEEN STRUGGLING WITH THE EXACT TRACK
WHICH WILL HAVE IMPLICATIONS ON HOW MUCH SNOW FALLS AND WHERE IT
FALLS. THE LATEST MODELS SHOW IT TRACKING NORTH OF THE AREA AND
HAVING MOST OF THE SNOW NORTH OF IT. THE FLOW IS ALSO IMPORTANT DUE
TO LAKE ENHANCEMENT POTENTIAL. FOR NOW WE HAVE A CHC OF SNOW SHOWERS
EVERYWHERE. THIS WILL HAVE TO BE FINE TUNED.
THE NOTEWORTHY CHANGE IN THE MODELS IS A TREND TOWARD A SHORTER STAY
FOR THE ARCTIC AIR. THE MODELS ARE MORE PROGRESSIVE THAN PREVIOUS
RUNS WITH THE UPPER TROUGH AND ARCTIC AIR. THIS IS LIKELY HAVING TO
DO WITH THE SPLIT FLOW THAT DEVELOPS. THE UPPER TROUGH IS EXPECTED
TO BE GONE BY THU NIGHT. THIS WOULD MEAN LESS LAKE EFFECT POTENTIAL.
BY FRI...THE AIR AT H850 IS NOT EVEN COLD ENOUGH FOR LAKE EFFECT. WE
END UP ONCE AGAIN IN NO MANS LAND BETWEEN THE JET STREAMS. THIS
WOULD BRING US SEASONABLE TEMPERATURES WITH LITTLE IF ANY PCPN CHCS.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1250 PM EST SAT DEC 29 2012
THE TWO MAIN ITEMS OF INTEREST WITH THIS SET OF FCSTS IS THE
CURRENT SNOW MOVING OUT THIS AFTERNOON AND THEN LAKE EFFECT TRENDS
FOR TONIGHT AND TOMORROW.
THE AREA OF LIGHT SNOW WAS SOUTHEAST OF A LINE FROM KALAMAZOO TO
GRAND RAPIDS TO ALMA AS OF 1745Z THIS AFTERNOON. THIS SNOW IS
PRODUCING LOW MVFR TO IFR CONDITIONS. THIS IS EXPECTED TO MOVE OUT
TO THE SE OF ALL THE TERMINALS BY AROUND 21Z THIS AFTERNOON. SOME
SCATTERED VFR CONDITIONS ARE POSSIBLE BEHIND THE SNOW FOR A SHORT
TIME. MORE MVFR CIGS AROUND 2500 FT ACROSS CENTRAL LOWER MICHIGAN
WILL MOVE IN LATER THIS AFTERNOON.
LAKE EFFECT SNOW SHOWERS WILL GRADUALLY MOVE IN LATE THIS
AFTERNOON AND MORE SO TONIGHT AS NNE WINDS GRADUALLY SHIFT TO THE
WEST OVERNIGHT TONIGHT. LAKE EFFECT WILL SPREAD ACROSS THE
LAKESHORE FIRST LATE AFTERNOON/EARLY EVENING...THEN INLAND
THEREAFTER. MAINLY MVFR CIGS AND VSBYS ARE EXPECTED WITH SOME SPOTTY
IFR POSSIBLE CLOSER TO THE LAKESHORE. SNOW SHOWERS WILL SLOWLY
DIMINISH THROUGH 18Z SUN THEN BEFORE ENDING AFTER THE TAF PERIOD.
&&
.MARINE...
ISSUED AT 321 PM EST SAT DEC 29 2012
NO CHANGES WERE MADE TO THE INHERITED FORECAST. LATEST LOCAL RUN OF
THE GLERL KEEPS WAVES BELOW SMALL CRAFT CRITERIA UNTIL WELL AFTER
MIDNIGHT. THIS IS A FEW HOURS AFTER THE 10 PM OFFICIAL START OF
THE SMALL CRAFT ADVISORY. A SUNDAY AFTERNOON EXPIRATION STILL
LOOKS ON TRACK.
&&
.HYDROLOGY...
ISSUED AT 321 PM EST SAT DEC 29 2012
NO HYDRO CONCERNS DUE TO VERY LITTLE QPF. RIVER ICE WILL BE LIKELY
TO DEVELOP BY THE END OF THE COMING WORK WEEK.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST SUNDAY
FOR LMZ844>849.
&&
$$
SYNOPSIS...TJT
SHORT TERM...TJT
LONG TERM...NJJ
AVIATION...NJJ
HYDROLOGY...TJT
MARINE...TJT
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
1250 PM EST SAT DEC 29 2012
.SYNOPSIS...
ISSUED AT 330 AM EST SAT DEC 29 2012
A FEW LIGHT SNOW SHOWERS AND FLURRIES WILL LINGER THIS MORNING WITH
LIGHT LAKE EFFECT SNOW SHOWERS EXPECTED TONIGHT INTO SUNDAY MORNING.
TEMPERATURES WILL AVERAGE BELOW NORMAL THROUGH THE COMING WEEK WITH
SEVERAL CHANCES FOR SNOW SHOWERS AND A SHOT OF MUCH COLDER AIR
EXPECTED FOR LATE WEEK.
&&
.UPDATE...
ISSUED AT 1125 AM EST SAT DEC 29 2012
UPDATED FORECASTS TO LOWER POPS NORTH OF I-96. HAVE ALSO DECREASED
POPS INTO THIS EVENING ALONG THE INTERIOR I-94 CORRIDOR. WE ARE
LOOKING FOR A QUICK BURST OF LAKE ENHANCED SNOW MAINLY BEFORE
MIDNIGHT MAINLY SOUTH OF HOLLAND THAT COULD ADD AN INCH OR SO NEAR
THE LAKESHORE.
RADAR LOOP INDICATES PRESENCE OF A SURFACE MESOLOW OVER
SOUTHEASTERN LAKE MICHIGAN THAT IS WEAKENING AND MOVING SOUTHEAST
TOWARDS SOUTH HAVEN. MESOSCALE SUBSIDENCE BEHIND THIS FEATURE IS
RESULTING IN A SHARP TRAILING EDGE TO THE SNOW THAT IS APPROACHING
I-96 FROM THE NORTH. TO THE WEST...A WEAK N-S UPPER POT VORT LOBE
NOTED ON WATER VAPOR IMAGERY IS CROSSING IA/MN AT THIS TIME AND
SHOULD IMPACT THE CWFA THIS EVENING AT ITS CURRENT RATE OF SPEED.
LATEST RAP SNOW TOOL GUIDANCE FOR SOUTH HAVEN (LWA) SUGGESTS THAT 1
TO 2 INCHES OF SNOW COULD FALL IN THE 9 PM - 1 AM TIME FRAME
THERE.
UPDATE
ISSUED AT 704 AM EST SAT DEC 29 2012
I HAVE UPDATED THE FORECAST TO ALLOW THE SNOW BAND JUST NOW MOVING
INTO THE I-96 AREA TO CONTINUE TO MOVE SOUTH OVER TIME. THIS IS
REALLY A WEAK COLD FRONT THAT IS MOVING SOUTH WITH TIME BEHIND THE
DEPARTING STORM. THE NAM SHOWS SOME WEAK LIFT IN THE DGZ AS THIS
FEATURE MOVES SOUTH WITH TIME. IT DOES TAKE IT`S TIME THROUGH BY
21Z THERE IS STILL LIFT OVER OUR SE CWA WITH THIS FEATURE. ONCE
THE FEATURE MOVES SOUTH THE SNOW WILL END FROM NORTH TO SOUTH BUT
IT MAY TAKE UNTIL NOON OR SO FOR IT TO END BY INTERSTATE 96 AND
LATER BY INTERSTATE 94. ACCUMULATIONS WILL LIMITED AS LIFT IS
FEEBLE AND CURRENT VISIBILITIES ARE IN THE 3 TO 6 MILE RANGE.
&&
.SHORT TERM...(TODAY THROUGH MONDAY AFTERNOON)
ISSUED AT 330 AM EST SAT DEC 29 2012
A FEW LIGHT SNOW SHOWERS AND FLURRIES WILL LINGER THIS MORNING.
STEADIER SYNOPTIC LIGHT SNOW WILL CLIP OUR EXTREME SE FCST AREA OVER
TOWARD JXN THIS MORNING AND EARLY AFTERNOON. LIGHT SNOW BEGAN IN JXN
ABOUT AN HOUR AGO AND VERY LIGHT ACCUMULATIONS OF UNDER AN INCH ARE
ANTICIPATED THERE.
AN UPPER LEVEL DISTURBANCE WILL BRING LAKE ENHANCED LIGHT SNOW
SHOWERS AND FLURRIES TONIGHT INTO SUNDAY MORNING BUT WITH LITTLE IF
ANY ACCUMULATIONS. A HIGH PRESSURE RIDGE WILL BRING FAIR WX SUNDAY
AFTERNOON THROUGH SUNDAY NIGHT BEFORE AN APPROACHING COLD FRONT
BRINGS A CHC OF LIGHT SNOW SHOWERS MONDAY.
.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 330 AM EST SAT DEC 29 2012
THE MAIN FOCUS OF THE LONG TERM PORTION OF THE FCST WILL BE ON THE
ARCTIC AIR MASS THAT IS EXPECTED TO COME DOWN LATER NEXT WEEK AND
THE LAKE EFFECT POTENTIAL WITH IT. THERE IS ALSO SOME POTENTIAL FOR
A SW FLOW EVENT MONDAY NIGHT.
CONFIDENCE IN THIS FORECAST IS BUILDING WITH EACH MODEL RUN SINCE
THE ARCTIC OUTBREAK HAS BEEN SHOWN BY THE GFS AND ECMWF FOR 5 DAYS
IN A ROW...ON BOTH THE 00Z AND 12Z RUNS.
THE LATEST RUN OF THE ECMWF AND GEM SHOW WHAT I HAVE BEEN TRYING TO
SAY FOR THE PAST 4 SHIFTS... THE SYSTEM WILL BE STRONG THAN
CURRENTLY FORECAST BY ANY OF THE MODELS. I BASE THIS ON THE 180-200
JET CORE THAT CROSSED THE DATELINE FRIDAY AFTERNOON. THE MODELS
CONTINUE TO SHOW THIS SYSTEM CLIMBING THE UPPER RIDGE AND DIVING
SOUTHEAST BY TUESDAY NIGHT INTO WEDNESDAY. THIS MAY ACTUALLY SLOW
DOWN THE PUSH OF COLD AIR BY 12 HOURS IF A DECENT SURFACE WAVES
DEVELOPS WHICH I BELIEVE WILL HAPPEN (AS PER LATEST ECMWF). THIS
WOULD MEAN A SIGNIFICANT WIND/SNOW EVENT FOR OUR CWA WED
NIGHT/THURSDAY. GIVEN THE ECMWF THIS WOULD NOT BE JUST THE LAKE
SHORE...SEEMS THERE WILL BE AN I-94 CONVERGENCE BAND THURSDAY SO
THIS SNOW WILL SPREAD WELL INLAND TOO. I INCREASED THE POP TO AROUND
50 PCT BECAUSE THERE IS LITTLE QUESTION IN MY MIND... IF THE COLD
AIR COMES DOWN IT WILL SNOW!
AS FOR MONDAY NIGHT/EARLY TUESDAY AS THE NEXT SHORTWAVE MOVES ACROSS
THE AREA WINDS WILL TURN SOUTHWEST SOME LIFT IN THE DECENT LIFT IN
THE DGZ AROUND 06Z TUESDAY. THIS COULD BE ONE OF THOSE SURPRISE
SNOW EVENTS... WE WILL HAVE TO WATCH THIS CLOSELY.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1250 PM EST SAT DEC 29 2012
THE TWO MAIN ITEMS OF INTEREST WITH THIS SET OF FCSTS IS THE
CURRENT SNOW MOVING OUT THIS AFTERNOON AND THEN LAKE EFFECT TRENDS
FOR TONIGHT AND TOMORROW.
THE AREA OF LIGHT SNOW WAS SOUTHEAST OF A LINE FROM KALAMAZOO TO
GRAND RAPIDS TO ALMA AS OF 1745Z THIS AFTERNOON. THIS SNOW IS
PRODUCING LOW MVFR TO IFR CONDITIONS. THIS IS EXPECTED TO MOVE OUT
TO THE SE OF ALL THE TERMINALS BY AROUND 21Z THIS AFTERNOON. SOME
SCATTERED VFR CONDITIONS ARE POSSIBLE BEHIND THE SNOW FOR A SHORT
TIME. MORE MVFR CIGS AROUND 2500 FT ACROSS CENTRAL LOWER MICHIGAN
WILL MOVE IN LATER THIS AFTERNOON.
LAKE EFFECT SNOW SHOWERS WILL GRADUALLY MOVE IN LATE THIS
AFTERNOON AND MORE SO TONIGHT AS NNE WINDS GRADUALLY SHIFT TO THE
WEST OVERNIGHT TONIGHT. LAKE EFFECT WILL SPREAD ACROSS THE
LAKESHORE FIRST LATE AFTERNOON/EARLY EVENING...THEN INLAND
THEREAFTER. MAINLY MVFR CIGS AND VSBYS ARE EXPECTED WITH SOME SPOTTY
IFR POSSIBLE CLOSER TO THE LAKESHORE. SNOW SHOWERS WILL SLOWLY
DIMINISH THROUGH 18Z SUN THEN BEFORE ENDING AFTER THE TAF PERIOD.
&&
.MARINE...
ISSUED AT 330 AM EST SAT DEC 29 2012
WINDS AND WAVES WILL REACH SCA CRITERIA LATE THIS EVENING SO WE WILL
HOIST A SCA FROM ST. JOSEPH TO MANISTEE FROM THEN THROUGH EARLY
SUNDAY AFTERNOON.
&&
.HYDROLOGY...
ISSUED AT 330 AM EST SAT DEC 29 2012
NO HYDRO CONCERNS DUE TO VERY LITTLE QPF BUT RIVER ICE WILL DEVELOP
THIS WEEK... PARTICULARLY LATE IN THE WEEK.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST SUNDAY
FOR LMZ844>849.
&&
$$
UPDATE...TJT
SYNOPSIS...LAURENS
SHORT TERM...LAURENS
LONG TERM...WDM
AVIATION...NJJ
HYDROLOGY...LAURENS
MARINE...LAURENS
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
1234 PM EST SAT DEC 29 2012
.AVIATION...
//DISCUSSION...
RESIDUAL MIDLEVEL DYNAMICS FROM AN EARLIER FRONTAL ZONE IS NOW
ADVECTING INTO SOUTHERN PORTIONS OF SOUTHEASTERN MICHIGAN FROM THE
NORTHWEST. FOR NOW...FLOW TRAJECTORY AND LATEST TRENDS SUGGESTS
PRECIPITATION WILL NOT IMPACT KFNT AND KMBS. BEHAVIOR OF BASE
REFLECTIVITY PRODUCTS HAS BEEN INTERESTING...SUGGESTING THAT
SEEDER FEEDER PROCESSES ARE IN PLAY TO HELP GENERATE A MODESTLY
BURGEONING AREA OF LIGHT SNOW. LACK OF ANY TANGIBLE DRY AIR
ADVECTION FOLLOWING LAST NIGHTS SYSTEM CERTAINLY SUPPORTS THIS
IDEA. EXPECTATIONS ARE FOR A PERIOD OF MVFR TYPE SNOW ACTIVITY
WITH SOME IFR VISIBILITIES RESULTING DUE TO THE ADDITION OF BR/HZ.
THE LAKE EFFECT SNOW ACTIVITY THAT IS EXPECTED TO CRASH INTO
PORTIONS OF THE THUMB LATER ON...SHOULD BE SUBSEQUENTLY SWEPT
EASTWARD. PERSISTENT NORTHWESTERLY...CYCLONIC FLOW SUPPORTS
STRATOCUMULUS THROUGHOUT THE TAF CYCLE.
FOR DTW...MVFR TO OCCASIONAL IFR VISBY LIGHT SNOW IS EXPECTED OVER
THE NEXT 3 TO 4 HOURS. THE REASON FOR IFR VISBY IS DUE TO THE
PERSISTENCE OF BR/HZ. CEILING HEIGHTS ARE EXPECTED TO REMAIN MVFR
THROUGHOUT THE PERIOD. MODEL DATA IS SUGGESTING IFR CEILING HEIGHTS
LATE TONIGHT/TOMORROW MORNING BUT ATTM...SUSPECT THE MODELS ARE
OVERDONE ON THE AMOUNT OF NEAR SURFACE MOISTURE.
//DTW THRESHOLD THREATS...
* HIGH CONFIDENCE CEILINGS WILL BE BELOW 5000 FT.
&&
.PREV DISCUSSION...ISSUED 1114 AM EST SAT DEC 29 2012
UPDATE...
SYSTEM SNOW FROM LAST NIGHTS EVENT HAS ALL BUT ENDED ACROSS
SOUTHEASTERN MICHIGAN. THERE IS SOME 3-4SM VISBY VARIETY LIGHT
SNOW CURRENTLY TRACKING TOWARDS THE WESTERN CWA FROM WESTERN
MICHIGAN. THIS ACTIVITY APPEARS TO BE DRIVEN BY A 850-700MB
TEMPERATURE GRADIENT STRUCTURE AND ASSOCIATED DEFORMATION THAT
HAD STALLED OUT ACROSS SECTIONS OF MID MICHIGAN OVERNIGHT. THIS
AXIS IS BECOMING FLUSHED/BACKED INTO SOUTHERN SECTIONS OF THE
LOWER PENINSULA AS MIDLEVEL WINDS BACK NORTHWESTERLY IN RESPONSE
TO THE SURFACE LOW PRESSURE CENTER NOW TRACKING INTO WESTERN PA.
FORCING DYNAMICS HAVE BEEN ERODING WITH A DOWNTREND OF
CONVERGENCE. A GENERAL CHANCE POP WILL SUFFICE. ANY ACCUMULATIONS
SHOULD BE LIMITED TO SECTIONS OF WASHTENAW/LENAWEE COUNTIES WHERE
A FEW TENTHS OF ADDITIONAL SNOWFALL IS POSSIBLE LATER THIS
AFTERNOON.
OTHERWISE...MAIN THING TO WATCH GOING FORWARD IS THE LAKE EFFECT
SNOWFALL POTENTIAL FOR THE NORTHERN THUMB AND IMMEDIATE LAKE HURON
SHORELINE. IT HAS BEEN DIFFICULT GAUGING INTENSITY AND LOCATION
OF EXISTING LAKE EFFECT/CLOUD MATERIAL DUE TO SPARSE RADAR NETWORK
AND HIGH CLOUDS OBSCURING ANY LOOK DOWN LOW. THERE WERE A FEW IR
IMAGES EARLIER THAT SUGGESTED PRE-EXISTING ORGANIZED BANDING
STRUCTURES. A SAMPLE OF SHORELINE SURFACE OBSERVATIONS DEPICT
CYCLONIC FLOW OUT OVER NORTH CENTRAL LAKE HURON SIGNALING A
MODERATE LAKE AGGREGATE TROUGH. THE SAME BACKING OF WINDS THAT IS
OCCURRING OVER PORTIONS OF LAKE MICHIGAN/WESTERN LOWER MICHIGAN
WILL EVENTUALLY CATCH UP TO LAKE HURON AND ACT IN ERODING THE LAKE
AGGREGATE TROUGH STRUCTURE. THE OBSERVATIONAL SETUP/REGIME AGREES
WELL WITH LATEST HRRR AND IN HOUSE HI RESOLUTION WRF RUNS THAT
CRASH A LAKE SCALE MESOVORTEX INTO HURON COUNTY DURING THE
AFTERNOON. CLOUD BEARING MEAN WIND SHOULD PUSH DEVELOPED LAKE
EFFECT SOUTHWARD WITH A TRAJECTORY THAT SHOULD HIT THE TIP OF THE
THUMB DIRECTLY. MODELS DISAGREE ON TIMING BY AS MUCH AS 3 HOURS
OR SO...WHICH MAKES TIMING THE ONSET DIFFICULT. DURATION IS EXPECTED
TO BE BRIEF...A FEW HOURS AT THOSE LOCATIONS IMPACTED WHICH WILL
LIMIT SNOWFALL AMOUNTS. LAKE EFFECT PARAMETERS ARE SO SO...4C
LAKE SFC TEMPERATURES YIELDING SFC-850 DELTA T OF -15C AND EQL
HEIGHTS REACHING 8 KFT AGL. DID INCREASE THE CONDITIONAL SNOWFALL
ACCUMULATIONS IN THE THUMB AS CONFIDENCE HAS INCREMENTALLY
INCREASED. LOCALLY...ACCUMULATIONS OF UP TO 3 INCHES WILL BE
POSSIBLE.
PREV DISCUSSION...ISSUED 405 AM EST SAT DEC 29 2012
SHORT TERM...TODAY THROUGH TONIGHT
EXTREMELY LOW H7-H4 STATIC STABILITY HAS ALLOWED FOR AN IMPRESSIVE
RESPONSE TO AN UNIMPRESSIVE FORCING FIELD OVER SOUTHEAST MICHIGAN
THIS MORNING. HEIGHT FALLS LEADING AN APPROACHING SHORTWAVE TROUGH
HAVE ALLOWED FOR NORTHWARD DEVELOPMENT OF WEAK DEFORMATION AND
300-305K ISENTROPIC ASCENT WHICH HAS RESULTED IN WIDESPREAD LIGHT
SNOW ALONG/SOUTH OF I-69. THE INHERITED FORECAST STILL LOOKS ON
TRACK GIVEN THE LATEST TRENDS IN OBSERVATIONS AND THE 00Z SUITE OF
GUIDANCE WHICH OFFERED LITTLE REASON TO DEVIATE FROM THE OFFICIAL
FORECAST REASONING. GIVEN AN EXPECTED DURATION OF ANYWHERE FROM 5
HOURS (NORTH) TO 9 HOURS (SOUTH) AND THERMODYNAMIC PROFILES
SUPPORTIVE OF SNOW RATIOS IN THE 10 TO 15:1 RANGE, A SOLID
2-3"/ISOLATED 4" IS STILL A REASONABLE EXPECTATION FOR FAR SOUTHEAST
AREAS, ESPECIALLY MONROE COUNTY...WITH A SOLID 1-2"/ISOLATED 3"
STILL FORECAST ALONG AND SOUTH OF A PORT HURON TO HOWELL LINE.
CONFIDENCE IS INCREASED COMPARED TO PREVIOUS FORECASTS AS IT APPEARS
THAT THE FORCING FIELD WILL SEE A BOOST BETWEEN 10-13Z AS THE TROUGH
AXIS OVER THE WESTERN GREAT LAKES ROTATES INTO THE AREA. LIGHT SNOW
MAY ULTIMATELY BE SLOW TO BREAK UP/TAPER OFF UNTIL PASSAGE OF THE
TROUGH TO THE EAST AFTER 18Z.
ATTENTION THEN TURNS TO LAKE EFFECT POTENTIAL FOR THE
CENTRAL/EASTERN THUMB DURING THE AFTERNOON AND EVENING HOURS.
VEERING BOUNDARY LAYER WIND BEHIND THE DEPARTING LOW WILL FORCE A
LAKE-INDUCED TROUGH TO ROTATE CYCLONICALLY ACROSS THE THUMB AS BL
FLOW SIMULTANEOUSLY BECOMES FOCUSED ONSHORE. IN AN ATTEMPT TO FINE
TUNE THE MESOSCALE ASPECTS OF THE FORECAST, MADE AN AGGRESSIVE
UPWARD BOOST TO POPS FOR BAD AXE AND POINTS EAST IN HURON/SANILAC
COUNTIES, BUT STILL STAYED ON THE CONSERVATIVE SIDE WITH REGARD TO
COVERAGE AND ACCUMULATION POTENTIAL...ALTHOUGH BOTH OF THESE WERE
STILL GIVEN AN UPWARD NUDGE, JUST TO A LESSER DEGREE. THE ROTATING
WIND FIELD IS EXPECTED TO LEAVE NO MORE THAN A 6 HOUR WINDOW THAT
WILL BE FAVORABLE FOR LES CONDITIONS IN THE THUMB, WHICH WILL BE THE
MAIN FACTOR IN LIMITING ACCUMULATING SNOW POTENTIAL IN THIS HIGH
PROBABILITY/SHORT DURATION LES SCENARIO.
LIGHT SNOW SHOWERS WILL THEN POTENTIALLY EXPAND FROM NORTH TO SOUTH
THROUGH THE AFTERNOON AS THE LAKE TROUGH AXIS ROTATES THROUGH THE
CWA DURING PEAK HEATING, GRADUALLY WEAKENING AS IT DOES SO.
ADDITIONAL MINOR ACCUMULATIONS WILL THEREFORE BE POSSIBLE IN THE
21Z-03Z TIME FRAME FOR A WIDE PORTION OF THE AREA, BUT ELECTED TO
LEAVE THE CURRENT FORECAST FOR A FEW ADDITIONAL TENTHS UNCHANGED
UNTIL LAKE-INDUCED EFFECTS BECOME BETTER DEFINED IN THE OBSERVATIONS
LATE THIS MORNING/EARLY THIS AFTERNOON.
DECREASING, BUT STILL PLENTIFUL, LOW CLOUDS AND A FRESH COUPLE
INCHES OF SNOW PACK WILL FAVOR OVERNIGHT LOWS IN THE UPPER TEENS,
JUST A TOUCH COOLER THAN THIS MORNING. A MORE SIGNIFICANT DOWNWARD
ADJUSTMENT WILL BE NEEDED SHOULD CLEARING OCCUR EARLIER THAN
EXPECTED.
LONG TERM...SUNDAY THROUGH FRIDAY
A RIDGE OF HIGH PRESSURE WILL BRING QUIET WEATHER DURING THE SECOND
HALF OF THE WEEKEND AS COOLER THAN NORMAL TEMPERATURES CONTINUE
ACROSS THE CENTRAL GREAT LAKES REGION. ATTENTION CONTINUES TO BE ON
TWO SYSTEMS TRACKING CLOSE TO SOUTHEAST MICHIGAN MONDAY AND MONDAY
NIGHT. THE MODELS CONTINUE TO KEEP THESE SYSTEMS FROM PHASING
TOGETHER OVER THE CENTRAL GREAT LAKES AS THE NORTHERN SYSTEM TRACKS
THROUGH SOUTHERN CANADA...FAR ENOUGH NORTH TO NOT PHASE WITH THE
SOUTHERN SYSTEM ACROSS THE OHIO VALLEY. HOWEVER THE NAM HAS COME IN
THIS RUN WITH THE SOUTHERN SYSTEM TRACKING MUCH FURTHER NORTH THAN
ANY OTHER MODEL INCLUDING THE CANADIAN/ECMWF/GFS. THIS FAR NORTH
SOLUTION WOULD BRING A SOLID INCH OF SNOW ACROSS MUCH OF SOUTHEAST
MICHIGAN AS THE NAM BRINGS THE SURFACE LOW THROUGH THE SOUTHERN
GREAT LAKES DURING THIS PERIOD. THE CANADIAN/ECMWF/GFS MODELS KEEP
THE LOW WELL TO THE SOUTH...TRACKING THROUGH THE TENNESSEE VALLEY
WITH A RIDGE ACROSS THE UPPER PLAINS ASSISTING IN KEEPING THE LOW ON
A SOUTHERN TRACK. SINCE THE NAM IS A SIGNIFICANT OUTLIER AND GIVEN
THE LARGE RIDGE ACROSS THE PLAINS WILL STICK WITH THE SOUTHERN
SOLUTION AND MAINTAIN A MOSTLY DRY FORECAST FOR MUCH OF THE CWA. THE
MAIN EXCEPTION WILL BE ACROSS THE FAR SOUTH WHICH MAY GET A GLANCING
BLOW OF SNOW SHOWERS AS A SHORTWAVE TRACKS THROUGH THE SOUTHERN
GREAT LAKES MONDAY NIGHT.
THE MAIN STORY DURING THE MIDDLE TO LATE PART OF THE WEEK WILL BE AN
ARCTIC AIRMASS THAT WILL MAKE ITS PRESENCE FELT ACROSS THE GREAT
LAKES REGION...BRINGING THE COLDEST AIR OF THE SEASON TO SOUTHEAST
MICHIGAN. THIS COLD AIRMASS WILL LIMIT HIGH TEMPERATURES TO AROUND
20 DEGREES THURSDAY AND FRIDAY...WITH SEVERAL LOCATIONS LIKELY NOT
EVEN REACHING THIS MARK. THE COLDEST PART OF THIS AIRMASS WILL BE
FELT DURING THE OVERNIGHT HOURS AS LOW TEMPERATURES GET DOWN INTO
THE SINGLE DIGITS BELOW ZERO THURSDAY NIGHT AS 850 MB TEMPERATURES
PLUMMET WELL INTO THE TEENS BELOW ZERO WITH SOME BREAKS IN THE
CLOUDS PROVIDING JUST ENOUGH RADIATIONAL COOLING TO PLUMMET
TEMPERATURES QUICKLY. DESPITE MODEL GUIDANCE COMING IN SEVERAL
DEGREES WARMER...THE MODELS GENERALLY HAVE A TOUGH TIME RESOLVING
ARCTIC OUTBREAKS. THEREFORE CONFIDENCE IS HIGHER THAN NORMAL IN
GOING SEVERAL DEGREES BELOW GUIDANCE NUMBERS THIS FAR OUT.
THE SECOND PART OF THE STORY DURING THE MID TO LATE PART OF THE WEEK
WITH BE ADDITIONAL SNOWFALL CHANCES AS A NORTHERLY FETCH OFF LAKE
HURON PRODUCES SEVERAL OPPORTUNITIES FOR LAKE EFFECT SNOW SHOWERS
ACROSS THE THUMB REGION. THE COLD AIRMASS WILL OFFER DELTA T VALUES
IN EXCESS OF 20...WITH THE MAIN LIMITING FACTOR BEING THE EXACT WIND
DIRECTION WHICH WILL DETERMINE WHO GETS THE MAJORITY OF THE LAKE
EFFECT SNOW. THIS FAR OUT WILL BLANKET THE THUMB WITH CHANCY SNOW
POPS UNTIL WIND DIRECTIONS CAN BE BETTER RESOLVED IN SUBSEQUENT RUNS.
MARINE...
A MODEST INCREASE TO THE SURFACE PRESSURE GRADIENT COMBINED WITH
WINDS ROTATING TO A MORE ONSHORE DIRECTION WILL RESULT IN THE
DEVELOPMENT OF A MODERATE BREEZE ACROSS CENTRAL AND SOUTHERN LAKE
HURON TODAY WHICH IS FORECAST TO DRIVE SIGNIFICANT WAVE HEIGHTS INTO
THE 3 TO 5 FOOT RANGE BEGINNING EARLY THIS AFTERNOON. FOR THIS
REASON...SMALL CRAFT ADVISORIES ARE NOW IN EFFECT FROM OUTER SAGINAW
BAY TO PORT SANILAC FOR THIS AFTERNOON THROUGH TONIGHT. DEPENDING ON
THE EXACT EVOLUTION OF THE WIND FIELD...THE ADVISORIES MAY NEED TO
BE ADJUSTED FURTHER SOUTHWARD TOWARD PORT HURON FOR THIS EVENING.
A MODERATE SOUTHWEST FLOW WILL DEVELOP SUNDAY NIGHT INTO MONDAY AS
THE SURFACE PRESSURE GRADIENT TIGHTENS OVER AREA WATERS AS LOW
PRESSURE CROSSES NORTH OF THE REGION. GUSTY NORTHWEST WINDS WILL
DEVELOP BY MIDWEEK NEXT WEEK AS COLDER AIR SPREADS INTO THE GREAT
LAKES REGION IN THE WAKE OF THIS SYSTEM.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
SANILAC...UNTIL 7 AM SUNDAY.
SMALL CRAFT ADVISORY...OUTER SAGINAW BAY...UNTIL 1 AM SUNDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....CB
UPDATE.......CB
SHORT TERM...JVC
LONG TERM....KURIMSKI
MARINE.......JVC
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
1126 AM EST SAT DEC 29 2012
.SYNOPSIS...
ISSUED AT 330 AM EST SAT DEC 29 2012
A FEW LIGHT SNOW SHOWERS AND FLURRIES WILL LINGER THIS MORNING WITH
LIGHT LAKE EFFECT SNOW SHOWERS EXPECTED TONIGHT INTO SUNDAY MORNING.
TEMPERATURES WILL AVERAGE BELOW NORMAL THROUGH THE COMING WEEK WITH
SEVERAL CHANCES FOR SNOW SHOWERS AND A SHOT OF MUCH COLDER AIR
EXPECTED FOR LATE WEEK.
&&
.UPDATE...
ISSUED AT 1125 AM EST SAT DEC 29 2012
UPDATED FORECASTS TO LOWER POPS NORTH OF I-96. HAVE ALSO DECREASED
POPS INTO THIS EVENING ALONG THE INTERIOR I-94 CORRIDOR. WE ARE
LOOKING FOR A QUICK BURST OF LAKE ENHANCED SNOW MAINLY BEFORE
MIDNIGHT MAINLY SOUTH OF HOLLAND THAT COULD ADD AN INCH OR SO NEAR
THE LAKESHORE.
RADAR LOOP INDICATES PRESENCE OF A SURFACE MESOLOW OVER
SOUTHEASTERN LAKE MICHIGAN THAT IS WEAKENING AND MOVING SOUTHEAST
TOWARDS SOUTH HAVEN. MESOSCALE SUBSIDENCE BEHIND THIS FEATURE IS
RESULTING IN A SHARP TRAILING EDGE TO THE SNOW THAT IS APPROACHING
I-96 FROM THE NORTH. TO THE WEST...A WEAK N-S UPPER POT VORT LOBE
NOTED ON WATER VAPOR IMAGERY IS CROSSING IA/MN AT THIS TIME AND
SHOULD IMPACT THE CWFA THIS EVENING AT ITS CURRENT RATE OF SPEED.
LATEST RAP SNOW TOOL GUIDANCE FOR SOUTH HAVEN (LWA) SUGGESTS THAT 1
TO 2 INCHES OF SNOW COULD FALL IN THE 9 PM - 1 AM TIME FRAME
THERE.
UPDATE
ISSUED AT 704 AM EST SAT DEC 29 2012
I HAVE UPDATED THE FORECAST TO ALLOW THE SNOW BAND JUST NOW MOVING
INTO THE I-96 AREA TO CONTINUE TO MOVE SOUTH OVER TIME. THIS IS
REALLY A WEAK COLD FRONT THAT IS MOVING SOUTH WITH TIME BEHIND THE
DEPARTING STORM. THE NAM SHOWS SOME WEAK LIFT IN THE DGZ AS THIS
FEATURE MOVES SOUTH WITH TIME. IT DOES TAKE IT`S TIME THROUGH BY
21Z THERE IS STILL LIFT OVER OUR SE CWA WITH THIS FEATURE. ONCE
THE FEATURE MOVES SOUTH THE SNOW WILL END FROM NORTH TO SOUTH BUT
IT MAY TAKE UNTIL NOON OR SO FOR IT TO END BY INTERSTATE 96 AND
LATER BY INTERSTATE 94. ACCUMULATIONS WILL LIMITED AS LIFT IS
FEEBLE AND CURRENT VISIBILITIES ARE IN THE 3 TO 6 MILE RANGE.
&&
.SHORT TERM...(TODAY THROUGH MONDAY AFTERNOON)
ISSUED AT 330 AM EST SAT DEC 29 2012
A FEW LIGHT SNOW SHOWERS AND FLURRIES WILL LINGER THIS MORNING.
STEADIER SYNOPTIC LIGHT SNOW WILL CLIP OUR EXTREME SE FCST AREA OVER
TOWARD JXN THIS MORNING AND EARLY AFTERNOON. LIGHT SNOW BEGAN IN JXN
ABOUT AN HOUR AGO AND VERY LIGHT ACCUMULATIONS OF UNDER AN INCH ARE
ANTICIPATED THERE.
AN UPPER LEVEL DISTURBANCE WILL BRING LAKE ENHANCED LIGHT SNOW
SHOWERS AND FLURRIES TONIGHT INTO SUNDAY MORNING BUT WITH LITTLE IF
ANY ACCUMULATIONS. A HIGH PRESSURE RIDGE WILL BRING FAIR WX SUNDAY
AFTERNOON THROUGH SUNDAY NIGHT BEFORE AN APPROACHING COLD FRONT
BRINGS A CHC OF LIGHT SNOW SHOWERS MONDAY.
.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 330 AM EST SAT DEC 29 2012
THE MAIN FOCUS OF THE LONG TERM PORTION OF THE FCST WILL BE ON THE
ARCTIC AIR MASS THAT IS EXPECTED TO COME DOWN LATER NEXT WEEK AND
THE LAKE EFFECT POTENTIAL WITH IT. THERE IS ALSO SOME POTENTIAL FOR
A SW FLOW EVENT MONDAY NIGHT.
CONFIDENCE IN THIS FORECAST IS BUILDING WITH EACH MODEL RUN SINCE
THE ARCTIC OUTBREAK HAS BEEN SHOWN BY THE GFS AND ECMWF FOR 5 DAYS
IN A ROW...ON BOTH THE 00Z AND 12Z RUNS.
THE LATEST RUN OF THE ECMWF AND GEM SHOW WHAT I HAVE BEEN TRYING TO
SAY FOR THE PAST 4 SHIFTS... THE SYSTEM WILL BE STRONG THAN
CURRENTLY FORECAST BY ANY OF THE MODELS. I BASE THIS ON THE 180-200
JET CORE THAT CROSSED THE DATELINE FRIDAY AFTERNOON. THE MODELS
CONTINUE TO SHOW THIS SYSTEM CLIMBING THE UPPER RIDGE AND DIVING
SOUTHEAST BY TUESDAY NIGHT INTO WEDNESDAY. THIS MAY ACTUALLY SLOW
DOWN THE PUSH OF COLD AIR BY 12 HOURS IF A DECENT SURFACE WAVES
DEVELOPS WHICH I BELIEVE WILL HAPPEN (AS PER LATEST ECMWF). THIS
WOULD MEAN A SIGNIFICANT WIND/SNOW EVENT FOR OUR CWA WED
NIGHT/THURSDAY. GIVEN THE ECMWF THIS WOULD NOT BE JUST THE LAKE
SHORE...SEEMS THERE WILL BE AN I-94 CONVERGENCE BAND THURSDAY SO
THIS SNOW WILL SPREAD WELL INLAND TOO. I INCREASED THE POP TO AROUND
50 PCT BECAUSE THERE IS LITTLE QUESTION IN MY MIND... IF THE COLD
AIR COMES DOWN IT WILL SNOW!
AS FOR MONDAY NIGHT/EARLY TUESDAY AS THE NEXT SHORTWAVE MOVES ACROSS
THE AREA WINDS WILL TURN SOUTHWEST SOME LIFT IN THE DECENT LIFT IN
THE DGZ AROUND 06Z TUESDAY. THIS COULD BE ONE OF THOSE SURPRISE
SNOW EVENTS... WE WILL HAVE TO WATCH THIS CLOSELY.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 704 AM EST SAT DEC 29 2012
AS THE SNOW BAND MOVES OUT OF THE JXN AREA ANOTHER SNOW BAND
ASSOCIATED WITH A WEAK COLD FRONT WILL MOVE ACROSS ALL OF THE TAF
SITES TODAY. OVERALL I EXPECT MVFR CIGS/VSBY AS THIS MOVES THROUGH
SOME BRIEF IFR VSBY ARE POSSIBLE IN THE BETTER SNOW SHOWERS.
TONIGHT WINDS SHIFT FROM NORTH TO WEST AND THAT WILL BRING LAKE
EFFECT INLAND TO MKG..,GRR...BTL AND AZO OVERNIGHT. MORE MVFR
CIGS/VSBY AS THIS TOO WILL BE LIGHT SNOW AS LIFT IS WEAK.
&&
.MARINE...
ISSUED AT 330 AM EST SAT DEC 29 2012
WINDS AND WAVES WILL REACH SCA CRITERIA LATE THIS EVENING SO WE WILL
HOIST A SCA FROM ST. JOSEPH TO MANISTEE FROM THEN THROUGH EARLY
SUNDAY AFTERNOON.
&&
.HYDROLOGY...
ISSUED AT 330 AM EST SAT DEC 29 2012
NO HYDRO CONCERNS DUE TO VERY LITTLE QPF BUT RIVER ICE WILL DEVELOP
THIS WEEK... PARTICULARLY LATE IN THE WEEK.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST SUNDAY
FOR LMZ844>849.
&&
$$
UPDATE...TJT
SYNOPSIS...LAURENS
SHORT TERM...LAURENS
LONG TERM...WDM
AVIATION...WDM
HYDROLOGY...LAURENS
MARINE...LAURENS
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
1114 AM EST SAT DEC 29 2012
.UPDATE...
SYSTEM SNOW FROM LAST NIGHTS EVENT HAS ALL BUT ENDED ACROSS
SOUTHEASTERN MICHIGAN. THERE IS SOME 3-4SM VISBY VARIETY LIGHT
SNOW CURRENTLY TRACKING TOWARDS THE WESTERN CWA FROM WESTERN
MICHIGAN. THIS ACTIVITY APPEARS TO BE DRIVEN BY A 850-700MB
TEMPERATURE GRADIENT STRUCTURE AND ASSOCIATED DEFORMATION THAT
HAD STALLED OUT ACROSS SECTIONS OF MID MICHIGAN OVERNIGHT. THIS
AXIS IS BECOMING FLUSHED/BACKED INTO SOUTHERN SECTIONS OF THE
LOWER PENINSULA AS MIDLEVEL WINDS BACK NORTHWESTERLY IN RESPONSE
TO THE SURFACE LOW PRESSURE CENTER NOW TRACKING INTO WESTERN PA.
FORCING DYNAMICS HAVE BEEN ERODING WITH A DOWNTREND OF
CONVERGENCE. A GENERAL CHANCE POP WILL SUFFICE. ANY ACCUMULATIONS
SHOULD BE LIMITED TO SECTIONS OF WASHTENAW/LENAWEE COUNTIES WHERE
A FEW TENTHS OF ADDITIONAL SNOWFALL IS POSSIBLE LATER THIS
AFTERNOON.
OTHERWISE...MAIN THING TO WATCH GOING FORWARD IS THE LAKE EFFECT
SNOWFALL POTENTIAL FOR THE NORTHERN THUMB AND IMMEDIATE LAKE HURON
SHORELINE. IT HAS BEEN DIFFICULT GAUGING INTENSITY AND LOCATION
OF EXISTING LAKE EFFECT/CLOUD MATERIAL DUE TO SPARSE RADAR NETWORK
AND HIGH CLOUDS OBSCURING ANY LOOK DOWN LOW. THERE WERE A FEW IR
IMAGES EARLIER THAT SUGGESTED PRE-EXISTING ORGANIZED BANDING
STRUCTURES. A SAMPLE OF SHORELINE SURFACE OBSERVATIONS DEPICT
CYCLONIC FLOW OUT OVER NORTH CENTRAL LAKE HURON SIGNALING A
MODERATE LAKE AGGREGATE TROUGH. THE SAME BACKING OF WINDS THAT IS
OCCURRING OVER PORTIONS OF LAKE MICHIGAN/WESTERN LOWER MICHIGAN
WILL EVENTUALLY CATCH UP TO LAKE HURON AND ACT IN ERODING THE LAKE
AGGREGATE TROUGH STRUCTURE. THE OBSERVATIONAL SETUP/REGIME AGREES
WELL WITH LATEST HRRR AND IN HOUSE HI RESOLUTION WRF RUNS THAT
CRASH A LAKE SCALE MESOVORTEX INTO HURON COUNTY DURING THE
AFTERNOON. CLOUD BEARING MEAN WIND SHOULD PUSH DEVELOPED LAKE
EFFECT SOUTHWARD WITH A TRAJECTORY THAT SHOULD HIT THE TIP OF THE
THUMB DIRECTLY. MODELS DISAGREE ON TIMING BY AS MUCH AS 3 HOURS
OR SO...WHICH MAKES TIMING THE ONSET DIFFICULT. DURATION IS EXPECTED
TO BE BRIEF...A FEW HOURS AT THOSE LOCATIONS IMPACTED WHICH WILL
LIMIT SNOWFALL AMOUNTS. LAKE EFFECT PARAMETERS ARE SO SO...4C
LAKE SFC TEMPERATURES YIELDING SFC-850 DELTA T OF -15C AND EQL
HEIGHTS REACHING 8 KFT AGL. DID INCREASE THE CONDITIONAL SNOWFALL
ACCUMULATIONS IN THE THUMB AS CONFIDENCE HAS INCREMENTALLY
INCREASED. LOCALLY...ACCUMULATIONS OF UP TO 3 INCHES WILL BE
POSSIBLE.
&&
.AVIATION...ISSUED 604 AM EST SAT DEC 29 2012
//DISCUSSION...
LIGHT TO OCCASIONALLY MODERATE SNOW HAS EXPANDED INTO SOUTHEAST
MICHIGAN THIS MORNING, BRINGING MVFR TO IFR CONDITIONS TO KFNT AND
POINTS SOUTH. SNOW WILL BE RELATIVELY SHORT-LIVED FOR NORTHERN
LOCATIONS SUCH AS FNT, WHERE AN ADDITIONAL COUPLE HOURS OR SO OF
LIGHT SNOW MAY RESULT IN SOME MINOR ACCUMULATIONS. THE AIRFIELDS OF
THE METRO DETROIT AREA, HOWEVER, WILL SEE A MORE PERSISTENT SNOW
GRADUALLY TAPER OFF IN COVERAGE BETWEEN NOW AND LATE MORNING WHEN
ANYWHERE FROM 1 TO 3 INCHES TOTAL CONTINUES TO LOOK PROBABLE.
ADDITIONAL LIGHT SNOW SHOWERS MAY TRACK FROM NORTH TO SOUTH ACROSS
THE AREA THIS AFTERNOON BRINGING LITTLE TO NO ADDITIONAL
ACCUMULATION.
FOR DTW...SNOW WILL PERSIST WITH REDUCED VSBYS THROUGH AT LEAST 14Z,
BEFORE GRADUALLY TAPERING OFF TO LOW OVERCAST CIGS AND FLURRIES BY
17Z. 2 TO 3 INCHES OF TOTAL ACCUMULATION IS STILL EXPECTED FOR KDTW.
//DTW THRESHOLD THREATS...
* HIGH CONFIDENCE CEILINGS WILL BE BELOW 5000 FT.
* LOW CONFIDENCE VISIBILITIES WILL DROP BELOW A HALF MILE IN SNOW
THIS MORNING.
&&
.PREV DISCUSSION...ISSUED 405 AM EST SAT DEC 29 2012
SHORT TERM...TODAY THROUGH TONIGHT
EXTREMELY LOW H7-H4 STATIC STABILITY HAS ALLOWED FOR AN IMPRESSIVE
RESPONSE TO AN UNIMPRESSIVE FORCING FIELD OVER SOUTHEAST MICHIGAN
THIS MORNING. HEIGHT FALLS LEADING AN APPROACHING SHORTWAVE TROUGH
HAVE ALLOWED FOR NORTHWARD DEVELOPMENT OF WEAK DEFORMATION AND
300-305K ISENTROPIC ASCENT WHICH HAS RESULTED IN WIDESPREAD LIGHT
SNOW ALONG/SOUTH OF I-69. THE INHERITED FORECAST STILL LOOKS ON
TRACK GIVEN THE LATEST TRENDS IN OBSERVATIONS AND THE 00Z SUITE OF
GUIDANCE WHICH OFFERED LITTLE REASON TO DEVIATE FROM THE OFFICIAL
FORECAST REASONING. GIVEN AN EXPECTED DURATION OF ANYWHERE FROM 5
HOURS (NORTH) TO 9 HOURS (SOUTH) AND THERMODYNAMIC PROFILES
SUPPORTIVE OF SNOW RATIOS IN THE 10 TO 15:1 RANGE, A SOLID
2-3"/ISOLATED 4" IS STILL A REASONABLE EXPECTATION FOR FAR SOUTHEAST
AREAS, ESPECIALLY MONROE COUNTY...WITH A SOLID 1-2"/ISOLATED 3"
STILL FORECAST ALONG AND SOUTH OF A PORT HURON TO HOWELL LINE.
CONFIDENCE IS INCREASED COMPARED TO PREVIOUS FORECASTS AS IT APPEARS
THAT THE FORCING FIELD WILL SEE A BOOST BETWEEN 10-13Z AS THE TROUGH
AXIS OVER THE WESTERN GREAT LAKES ROTATES INTO THE AREA. LIGHT SNOW
MAY ULTIMATELY BE SLOW TO BREAK UP/TAPER OFF UNTIL PASSAGE OF THE
TROUGH TO THE EAST AFTER 18Z.
ATTENTION THEN TURNS TO LAKE EFFECT POTENTIAL FOR THE
CENTRAL/EASTERN THUMB DURING THE AFTERNOON AND EVENING HOURS.
VEERING BOUNDARY LAYER WIND BEHIND THE DEPARTING LOW WILL FORCE A
LAKE-INDUCED TROUGH TO ROTATE CYCLONICALLY ACROSS THE THUMB AS BL
FLOW SIMULTANEOUSLY BECOMES FOCUSED ONSHORE. IN AN ATTEMPT TO FINE
TUNE THE MESOSCALE ASPECTS OF THE FORECAST, MADE AN AGGRESSIVE
UPWARD BOOST TO POPS FOR BAD AXE AND POINTS EAST IN HURON/SANILAC
COUNTIES, BUT STILL STAYED ON THE CONSERVATIVE SIDE WITH REGARD TO
COVERAGE AND ACCUMULATION POTENTIAL...ALTHOUGH BOTH OF THESE WERE
STILL GIVEN AN UPWARD NUDGE, JUST TO A LESSER DEGREE. THE ROTATING
WIND FIELD IS EXPECTED TO LEAVE NO MORE THAN A 6 HOUR WINDOW THAT
WILL BE FAVORABLE FOR LES CONDITIONS IN THE THUMB, WHICH WILL BE THE
MAIN FACTOR IN LIMITING ACCUMULATING SNOW POTENTIAL IN THIS HIGH
PROBABILITY/SHORT DURATION LES SCENARIO.
LIGHT SNOW SHOWERS WILL THEN POTENTIALLY EXPAND FROM NORTH TO SOUTH
THROUGH THE AFTERNOON AS THE LAKE TROUGH AXIS ROTATES THROUGH THE
CWA DURING PEAK HEATING, GRADUALLY WEAKENING AS IT DOES SO.
ADDITIONAL MINOR ACCUMULATIONS WILL THEREFORE BE POSSIBLE IN THE
21Z-03Z TIME FRAME FOR A WIDE PORTION OF THE AREA, BUT ELECTED TO
LEAVE THE CURRENT FORECAST FOR A FEW ADDITIONAL TENTHS UNCHANGED
UNTIL LAKE-INDUCED EFFECTS BECOME BETTER DEFINED IN THE OBSERVATIONS
LATE THIS MORNING/EARLY THIS AFTERNOON.
DECREASING, BUT STILL PLENTIFUL, LOW CLOUDS AND A FRESH COUPLE
INCHES OF SNOW PACK WILL FAVOR OVERNIGHT LOWS IN THE UPPER TEENS,
JUST A TOUCH COOLER THAN THIS MORNING. A MORE SIGNIFICANT DOWNWARD
ADJUSTMENT WILL BE NEEDED SHOULD CLEARING OCCUR EARLIER THAN
EXPECTED.
LONG TERM...SUNDAY THROUGH FRIDAY
A RIDGE OF HIGH PRESSURE WILL BRING QUIET WEATHER DURING THE SECOND
HALF OF THE WEEKEND AS COOLER THAN NORMAL TEMPERATURES CONTINUE
ACROSS THE CENTRAL GREAT LAKES REGION. ATTENTION CONTINUES TO BE ON
TWO SYSTEMS TRACKING CLOSE TO SOUTHEAST MICHIGAN MONDAY AND MONDAY
NIGHT. THE MODELS CONTINUE TO KEEP THESE SYSTEMS FROM PHASING
TOGETHER OVER THE CENTRAL GREAT LAKES AS THE NORTHERN SYSTEM TRACKS
THROUGH SOUTHERN CANADA...FAR ENOUGH NORTH TO NOT PHASE WITH THE
SOUTHERN SYSTEM ACROSS THE OHIO VALLEY. HOWEVER THE NAM HAS COME IN
THIS RUN WITH THE SOUTHERN SYSTEM TRACKING MUCH FURTHER NORTH THAN
ANY OTHER MODEL INCLUDING THE CANADIAN/ECMWF/GFS. THIS FAR NORTH
SOLUTION WOULD BRING A SOLID INCH OF SNOW ACROSS MUCH OF SOUTHEAST
MICHIGAN AS THE NAM BRINGS THE SURFACE LOW THROUGH THE SOUTHERN
GREAT LAKES DURING THIS PERIOD. THE CANADIAN/ECMWF/GFS MODELS KEEP
THE LOW WELL TO THE SOUTH...TRACKING THROUGH THE TENNESSEE VALLEY
WITH A RIDGE ACROSS THE UPPER PLAINS ASSISTING IN KEEPING THE LOW ON
A SOUTHERN TRACK. SINCE THE NAM IS A SIGNIFICANT OUTLIER AND GIVEN
THE LARGE RIDGE ACROSS THE PLAINS WILL STICK WITH THE SOUTHERN
SOLUTION AND MAINTAIN A MOSTLY DRY FORECAST FOR MUCH OF THE CWA. THE
MAIN EXCEPTION WILL BE ACROSS THE FAR SOUTH WHICH MAY GET A GLANCING
BLOW OF SNOW SHOWERS AS A SHORTWAVE TRACKS THROUGH THE SOUTHERN
GREAT LAKES MONDAY NIGHT.
THE MAIN STORY DURING THE MIDDLE TO LATE PART OF THE WEEK WILL BE AN
ARCTIC AIRMASS THAT WILL MAKE ITS PRESENCE FELT ACROSS THE GREAT
LAKES REGION...BRINGING THE COLDEST AIR OF THE SEASON TO SOUTHEAST
MICHIGAN. THIS COLD AIRMASS WILL LIMIT HIGH TEMPERATURES TO AROUND
20 DEGREES THURSDAY AND FRIDAY...WITH SEVERAL LOCATIONS LIKELY NOT
EVEN REACHING THIS MARK. THE COLDEST PART OF THIS AIRMASS WILL BE
FELT DURING THE OVERNIGHT HOURS AS LOW TEMPERATURES GET DOWN INTO
THE SINGLE DIGITS BELOW ZERO THURSDAY NIGHT AS 850 MB TEMPERATURES
PLUMMET WELL INTO THE TEENS BELOW ZERO WITH SOME BREAKS IN THE
CLOUDS PROVIDING JUST ENOUGH RADIATIONAL COOLING TO PLUMMET
TEMPERATURES QUICKLY. DESPITE MODEL GUIDANCE COMING IN SEVERAL
DEGREES WARMER...THE MODELS GENERALLY HAVE A TOUGH TIME RESOLVING
ARCTIC OUTBREAKS. THEREFORE CONFIDENCE IS HIGHER THAN NORMAL IN
GOING SEVERAL DEGREES BELOW GUIDANCE NUMBERS THIS FAR OUT.
THE SECOND PART OF THE STORY DURING THE MID TO LATE PART OF THE WEEK
WITH BE ADDITIONAL SNOWFALL CHANCES AS A NORTHERLY FETCH OFF LAKE
HURON PRODUCES SEVERAL OPPORTUNITIES FOR LAKE EFFECT SNOW SHOWERS
ACROSS THE THUMB REGION. THE COLD AIRMASS WILL OFFER DELTA T VALUES
IN EXCESS OF 20...WITH THE MAIN LIMITING FACTOR BEING THE EXACT WIND
DIRECTION WHICH WILL DETERMINE WHO GETS THE MAJORITY OF THE LAKE
EFFECT SNOW. THIS FAR OUT WILL BLANKET THE THUMB WITH CHANCY SNOW
POPS UNTIL WIND DIRECTIONS CAN BE BETTER RESOLVED IN SUBSEQUENT RUNS.
MARINE...
A MODEST INCREASE TO THE SURFACE PRESSURE GRADIENT COMBINED WITH
WINDS ROTATING TO A MORE ONSHORE DIRECTION WILL RESULT IN THE
DEVELOPMENT OF A MODERATE BREEZE ACROSS CENTRAL AND SOUTHERN LAKE
HURON TODAY WHICH IS FORECAST TO DRIVE SIGNIFICANT WAVE HEIGHTS INTO
THE 3 TO 5 FOOT RANGE BEGINNING EARLY THIS AFTERNOON. FOR THIS
REASON...SMALL CRAFT ADVISORIES ARE NOW IN EFFECT FROM OUTER SAGINAW
BAY TO PORT SANILAC FOR THIS AFTERNOON THROUGH TONIGHT. DEPENDING ON
THE EXACT EVOLUTION OF THE WIND FIELD...THE ADVISORIES MAY NEED TO
BE ADJUSTED FURTHER SOUTHWARD TOWARD PORT HURON FOR THIS EVENING.
A MODERATE SOUTHWEST FLOW WILL DEVELOP SUNDAY NIGHT INTO MONDAY AS
THE SURFACE PRESSURE GRADIENT TIGHTENS OVER AREA WATERS AS LOW
PRESSURE CROSSES NORTH OF THE REGION. GUSTY NORTHWEST WINDS WILL
DEVELOP BY MIDWEEK NEXT WEEK AS COLDER AIR SPREADS INTO THE GREAT
LAKES REGION IN THE WAKE OF THIS SYSTEM.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
SANILAC...UNTIL 7 AM SUNDAY.
SMALL CRAFT ADVISORY...OUTER SAGINAW BAY...UNTIL 1 AM SUNDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
UPDATE.......CB
AVIATION.....JVC
SHORT TERM...JVC
LONG TERM....KURIMSKI
MARINE.......JVC
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
1159 AM CST SAT DEC 29 2012
AVIATION... /18Z TAF ISSUANCE/
A TROUGH OF LOW PRESSURE ALOFT IS PASSING ACROSS EASTERN MN ATTM.
LIGHT SNOW ACROSS THE TWIN CITIES WILL MOVE ACROSS KRNH AND KEAU
EARLY IN THE AFTERNOON WITH 2SM VSBYS ALONG WITH CEILINGS DIPPING
BELOW 1K FEET. SUBSIDENCE IN THE WAKE OF THE TROUGH IS HELPING TO
DIMINISH CLOUDINESS TO OUR WEST. SOME VFR CEILINGS IN THE 035-040
FOOT RANGE IN WEST CENTRAL MN WILL BE MOVING THROUGH KAXN AND
KRWF. SOME -SN STILL POSSIBLE FOR A FEW HOURS AT KAXN ALONG MVFR
CEILINGS. CONFIDENCE ON FORECAST FOR TONIGHT IS LOW. HIGH
PRESSURE WILL BE PASSING BY WITH LOW LEVEL WARMING DURING THE
OVERNIGHT HOURS. CONCERN IS THAT STRATUS AND FOG MAY DEVELOP FOR
THE MN TAF SITES SIMILAR TO THAT OF THIS MORNING IN EASTERN SD.
VARIOUS GUIDANCE IN THE SHORT TERM IS INDICATING VFR. FOR
NOW...DROPPED VSBYS TO MVFR DURING THE EVENING WITH FEW-SCT CLOUDS
IN THE 008-015 RANGE. WEST WINDS THIS AFTERNOON 7-9 KNOTS BACKING
SW 3-5 KNOTS TONIGHT AND THEN S 8-10 KNOTS ON SUNDAY.
KMSP...MAIN SNOW AREA IS NOW EAST OF THE AIRFIELD WITH BKN-OVC
MVFR CEILINGS. POTENTIAL FOR SCT CONDITIONS IN THE 19Z-21Z TIME
FRAME. VFR CEILINGS IN THE 035-040 POSSIBLE LATE THIS AFTERNOON
AND EARLY TONIGHT. MVFR VSBY LIKELY LATE TONIGHT AND SUNDAY
MORNING.
/OUTLOOK FOR KMSP/
SUN...VFR. WINDS S 5-10 KTS.
MON...MVFR CIGS. WINDS NW 15 TO 20 KTS.
TUE...VFR. WINDS WSW 10 KTS.
&&
.DISCUSSION... /ISSUED ISSUED 427 AM CST SAT DEC 29 2012/
.SHORT TERM...TODAY THROUGH MONDAY NIGHT
STRATUS HAS REDEVELOPED ACROSS ALL OF MN AND WI OVERNIGHT WITH
ONLY SMALL SIGNS OF ERODING OVER FAR WRN MN EARLY THIS MORNING.
AREAS OF FREEZING FOG HAVE ALSO FORMED WITH SOME VISIBILITY
RESTRICTIONS DOWN TO 1/4 MILE. BECAUSE THE DGZ IS SO LOW AND
SATURATED...HAVE ALSO SEEN SEVERAL OBS REPORTING FLURRIES OR LIGHT
SNOW SHOWERS.
CONFIDENCE IS QUITE LOW WITH RESPECT TO TIMING THE CLOUD
DISSIPATION TODAY. NAM AND RAP ARE MOST PESSIMISTIC KEEPING LOW
CLOUDS IN THROUGH THE AFTERNOON. GFS AND LAMP ARE A LITTLE MORE
OPTIMISTIC WITH CLEARING THIS AFTERNOON. GIVEN THE TIME OF YEAR
AND HOW SOLID IT LOOKS ON SATELLITE...AM LEANING TOWARD THE MORE
PESSIMISTIC SOLUTION. AS A RESULT OF THE WIDESPREAD
STRATUS...TEMPERATURES REMAINED A BIT WARMER THAN ANTICIPATED
OVERNIGHT AND AS OF 4 AM ARE NEAR FORECAST HIGHS FOR TODAY. LITTLE
DIURNAL CLIMB EXPECTED THOUGH DUE TO SAID CLOUDS AND WEAK CAA SO
STILL FORECASTING HIGHS IN THE TEENS.
CLEARING SHOULD ARRIVE TONIGHT ACCORDING TO ALL AVAILABLE
GUIDANCE. THERE IS SOME CONCERN HOWEVER THAT IF THEY DO NOT
DISSIPATE THIS AFTERNOON THEY MAY STICK AROUND THROUGH TONIGHT AS
THE INVERSION INTENSIFIES. ASSUMING THE GUIDANCE IS RIGHT...
TONIGHT SHOULD BE A COLD ONE AS A RIDGE AXIS SETTLES OVERHEAD.
LOWS IN THE SINGLE DIGITS ABOVE AND BELOW ZERO ARE EXPECTED.
LOW PRESSURE WILL ZIP ACROSS SOUTHERN CANADA SUNDAY WITH A COLD
FRONT ARRIVING SUNDAY EVENING. WAA AHEAD OF THIS SYSTEM WILL BRING
A QUICK REBOUND OF TEMPS BACK INTO THE 20S. COULD SEE SOME
FLURRIES ACROSS CNTRL MN AND WI WHERE MOISTURE DEPTH AND FORCING
SHOULD BE GREATER...OTHERWISE THE COLD FRONT WILL BE DRY. VERY
STRONG CAA BEHIND THE FRONT WILL BRING STEADY OR FALLING TEMPS
INTO THE SINGLE DIGITS COME MONDAY AS 925 MB TEMPS CRASH TO -18C.
A RIDGE WILL SETTLE OVERHEAD MONDAY NIGHT. CLEAR SKIES...LIGHT
WINDS...AND A VERY COLD AIRMASS SHOULD ALLOW MOST PLACES TO
PLUMMET INTO THE TEENS BELOW ZERO...AND PERHAPS TO 20 BELOW IN
SOME OF THE COLDEST LOCATIONS. THE PLACEMENT OF THE RIDGE WILL BE
CRUCIAL. GFS HAS BEEN FURTHEST EAST WITH IT AND BRINGS WAA ACROSS
WRN MN LATE MONDAY NIGHT WITH THE COLDEST TEMPS ACROSS WI.
NAM/DGEX/GEM/ECMWF HAVE BEEN A BIT FURTHER WEST WITH THE CORE OF
THE COLD AIR. INTERESTINGLY...THE 29.00Z NAM/GEM...28.18Z
DGEX...AND 28.12Z EURO HAD GOOD CONSISTENCY WITH TEMPS RANGING
FROM NEAR -22F OVER ERN CHIPPEWA CO MN...TO ABOUT -5F IN THE TWIN
CITIES METRO. LEANED TOWARD THOSE RAW SOLUTIONS FOR THIS FORECAST
AND DISCARDED THE GFS. 29.00Z EURO CAME IN A TAD WARMER. WITH
TEMPS SUCH AS THESE...IT WON/T TAKE MUCH TO BRING THE WIND CHILL
WAY DOWN. EVEN A 5 KT WIND WOULD RESULT IN -20 TO -30F.
.LONG TERM...NEW YEARS DAY THROUGH FRIDAY
RIDGE SETTLES SOUTH WITH RETURN FLOW ALLOWING ANOTHER QUICK
REBOUND OF TEMPS BACK INTO THE TEENS ON NEW YEARS DAY.
ANOTHER SYSTEM ZIPPING ACROSS THE NORTHERN GREAT LAKES WILL BRING
A WEAK FRONT SOUTH ON TUESDAY. MEANWHILE...YET ANOTHER SYSTEM
WILL DIVE SOUTHEAST INTO THE NORTHERN PLAINS TUESDAY NIGHT AND
BRING A STRONG COLD FRONT THROUGH WEDNESDAY OR WEDNESDAY EVENING.
THIS SYSTEM MAY BRING A BIT OF LIGHT SNOW BEFORE ANOTHER SURGE OF
ARCTIC AIR SPILLS SOUTH. COULD SEE A SIMILAR SCENARIO FROM EARLIER
IN THE WEEK WITH LOWS IN THE TEENS BELOW ZERO THURSDAY MORNING AND
HIGHS IN THE SINGLE DIGITS. THIS ONE HAS A LITTLE MORE UNCERTAINTY
WITH THE POTENTIAL FOR CLOUDS TO LINGER SO DID NOT GO TOO CRAZY
WITH TEMPERATURES YET.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
RAH/BB
AREA FORECAST DISCUSSION...UPDATED FOR 12Z TAFS
NWS TWIN CITIES/CHANHASSEN MN
540 AM CST SAT DEC 29 2012
.DISCUSSION...ISSUED 427 AM CST
.SHORT TERM...TODAY THROUGH MONDAY NIGHT.
STRATUS HAS REDEVELOPED ACROSS ALL OF MN AND WI OVERNIGHT WITH
ONLY SMALL SIGNS OF ERODING OVER FAR WRN MN EARLY THIS MORNING.
AREAS OF FREEZING FOG HAVE ALSO FORMED WITH SOME VISIBILITY
RESTRICTIONS DOWN TO 1/4 MILE. BECAUSE THE DGZ IS SO LOW AND
SATURATED...HAVE ALSO SEEN SEVERAL OBS REPORTING FLURRIES OR LIGHT
SNOW SHOWERS.
CONFIDENCE IS QUITE LOW WITH RESPECT TO TIMING THE CLOUD
DISSIPATION TODAY. NAM AND RAP ARE MOST PESSIMISTIC KEEPING LOW
CLOUDS IN THROUGH THE AFTERNOON. GFS AND LAMP ARE A LITTLE MORE
OPTIMISTIC WITH CLEARING THIS AFTERNOON. GIVEN THE TIME OF YEAR
AND HOW SOLID IT LOOKS ON SATELLITE...AM LEANING TOWARD THE MORE
PESSIMISTIC SOLUTION. AS A RESULT OF THE WIDESPREAD
STRATUS...TEMPERATURES REMAINED A BIT WARMER THAN ANTICIPATED
OVERNIGHT AND AS OF 4 AM ARE NEAR FORECAST HIGHS FOR TODAY. LITTLE
DIURNAL CLIMB EXPECTED THOUGH DUE TO SAID CLOUDS AND WEAK CAA SO
STILL FORECASTING HIGHS IN THE TEENS.
CLEARING SHOULD ARRIVE TONIGHT ACCORDING TO ALL AVAILABLE
GUIDANCE. THERE IS SOME CONCERN HOWEVER THAT IF THEY DO NOT
DISSIPATE THIS AFTERNOON THEY MAY STICK AROUND THROUGH TONIGHT AS
THE INVERSION INTENSIFIES. ASSUMING THE GUIDANCE IS RIGHT...
TONIGHT SHOULD BE A COLD ONE AS A RIDGE AXIS SETTLES OVERHEAD.
LOWS IN THE SINGLE DIGITS ABOVE AND BELOW ZERO ARE EXPECTED.
LOW PRESSURE WILL ZIP ACROSS SOUTHERN CANADA SUNDAY WITH A COLD
FRONT ARRIVING SUNDAY EVENING. WAA AHEAD OF THIS SYSTEM WILL BRING
A QUICK REBOUND OF TEMPS BACK INTO THE 20S. COULD SEE SOME
FLURRIES ACROSS CNTRL MN AND WI WHERE MOISTURE DEPTH AND FORCING
SHOULD BE GREATER...OTHERWISE THE COLD FRONT WILL BE DRY. VERY
STRONG CAA BEHIND THE FRONT WILL BRING STEADY OR FALLING TEMPS
INTO THE SINGLE DIGITS COME MONDAY AS 925 MB TEMPS CRASH TO -18C.
A RIDGE WILL SETTLE OVERHEAD MONDAY NIGHT. CLEAR SKIES...LIGHT
WINDS...AND A VERY COLD AIRMASS SHOULD ALLOW MOST PLACES TO
PLUMMET INTO THE TEENS BELOW ZERO...AND PERHAPS TO 20 BELOW IN
SOME OF THE COLDEST LOCATIONS. THE PLACEMENT OF THE RIDGE WILL BE
CRUCIAL. GFS HAS BEEN FURTHEST EAST WITH IT AND BRINGS WAA ACROSS
WRN MN LATE MONDAY NIGHT WITH THE COLDEST TEMPS ACROSS WI.
NAM/DGEX/GEM/ECMWF HAVE BEEN A BIT FURTHER WEST WITH THE CORE OF
THE COLD AIR. INTERESTINGLY...THE 29.00Z NAM/GEM...28.18Z
DGEX...AND 28.12Z EURO HAD GOOD CONSISTENCY WITH TEMPS RANGING
FROM NEAR -22F OVER ERN CHIPPEWA CO MN...TO ABOUT -5F IN THE TWIN
CITIES METRO. LEANED TOWARD THOSE RAW SOLUTIONS FOR THIS FORECAST
AND DISCARDED THE GFS. 29.00Z EURO CAME IN A TAD WARMER. WITH
TEMPS SUCH AS THESE...IT WON/T TAKE MUCH TO BRING THE WIND CHILL
WAY DOWN. EVEN A 5 KT WIND WOULD RESULT IN -20 TO -30F.
.LONG TERM...NEW YEARS DAY THROUGH FRIDAY.
RIDGE SETTLES SOUTH WITH RETURN FLOW ALLOWING ANOTHER QUICK
REBOUND OF TEMPS BACK INTO THE TEENS ON NEW YEARS DAY.
ANOTHER SYSTEM ZIPPING ACROSS THE NORTHERN GREAT LAKES WILL BRING
A WEAK FRONT SOUTH ON TUESDAY. MEANWHILE...YET ANOTHER SYSTEM
WILL DIVE SOUTHEAST INTO THE NORTHERN PLAINS TUESDAY NIGHT AND
BRING A STRONG COLD FRONT THROUGH WEDNESDAY OR WEDNESDAY EVENING.
THIS SYSTEM MAY BRING A BIT OF LIGHT SNOW BEFORE ANOTHER SURGE OF
ARCTIC AIR SPILLS SOUTH. COULD SEE A SIMILAR SCENARIO FROM EARLIER
IN THE WEEK WITH LOWS IN THE TEENS BELOW ZERO THURSDAY MORNING AND
HIGHS IN THE SINGLE DIGITS. THIS ONE HAS A LITTLE MORE UNCERTAINTY
WITH THE POTENTIAL FOR CLOUDS TO LINGER SO DID NOT GO TOO CRAZY
WITH TEMPERATURES YET.
&&
.AVIATION.../12Z TAF ISSUANCE/
A RATHER MESSY AVIATION FORECAST WITH SOME CLEARING CURRENTLY
PUSHING INTO W MN...BUT STRATUS/FOG REFORMING UNDER SFC RIDGE IN E
SODAK. RWF WILL PRBLY GO SCT SHORTLY...BUT THINK THAT IFR CONDS WILL
REFORM FOR A FEW HRS. SIMILAR SITU FOR AXN. IFR CONDS ON THE W
DOORSTEP OF STC WILL MOVE INTO THAT TAF VERY SHORTLY AND LAST THRU
THE MRNG. REMAINING TAFS SHUD REMAIN MVFR THIS MRNG WITH IFR CONDS
LIKELY STAYING FARTHER WEST. SLO IMPRVG TREND DRNG THE AFTN...BUT
NO MUCH CONFIDENCE ON TIMING WITH SFC RIDGE ONLY PUSHING INTO W MN
BY 00Z.
KMSP...EXPECT CIGS TO REMAIN AOA OVC018 THRU THE MRNG. MAY SEE CIGS
GO BKN020 DRNG THE AFTN. SFC WNDS WNW AOB 10 KTS BCMG SW OVERNIGHT.
/OUTLOOK FOR KMSP/
SUN...VFR. WINDS SSE 5-10 KTS.
MON...MVFR. WINDS NW 15 TO 20 KTS.
TUE...VFR. WINDS WSW 10 TO 15 KTS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
BORGHOFF/BAP
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
427 AM CST SAT DEC 29 2012
.DISCUSSION...
.SHORT TERM...TODAY THROUGH MONDAY NIGHT.
STRATUS HAS REDEVELOPED ACROSS ALL OF MN AND WI OVERNIGHT WITH
ONLY SMALL SIGNS OF ERODING OVER FAR WRN MN EARLY THIS MORNING.
AREAS OF FREEZING FOG HAVE ALSO FORMED WITH SOME VISIBILITY
RESTRICTIONS DOWN TO 1/4 MILE. BECAUSE THE DGZ IS SO LOW AND
SATURATED...HAVE ALSO SEEN SEVERAL OBS REPORTING FLURRIES OR LIGHT
SNOW SHOWERS.
CONFIDENCE IS QUITE LOW WITH RESPECT TO TIMING THE CLOUD
DISSIPATION TODAY. NAM AND RAP ARE MOST PESSIMISTIC KEEPING LOW
CLOUDS IN THROUGH THE AFTERNOON. GFS AND LAMP ARE A LITTLE MORE
OPTIMISTIC WITH CLEARING THIS AFTERNOON. GIVEN THE TIME OF YEAR
AND HOW SOLID IT LOOKS ON SATELLITE...AM LEANING TOWARD THE MORE
PESSIMISTIC SOLUTION. AS A RESULT OF THE WIDESPREAD
STRATUS...TEMPERATURES REMAINED A BIT WARMER THAN ANTICIPATED
OVERNIGHT AND AS OF 4 AM ARE NEAR FORECAST HIGHS FOR TODAY. LITTLE
DIURNAL CLIMB EXPECTED THOUGH DUE TO SAID CLOUDS AND WEAK CAA SO
STILL FORECASTING HIGHS IN THE TEENS.
CLEARING SHOULD ARRIVE TONIGHT ACCORDING TO ALL AVAILABLE
GUIDANCE. THERE IS SOME CONCERN HOWEVER THAT IF THEY DO NOT
DISSIPATE THIS AFTERNOON THEY MAY STICK AROUND THROUGH TONIGHT AS
THE INVERSION INTENSIFIES. ASSUMING THE GUIDANCE IS RIGHT...
TONIGHT SHOULD BE A COLD ONE AS A RIDGE AXIS SETTLES OVERHEAD.
LOWS IN THE SINGLE DIGITS ABOVE AND BELOW ZERO ARE EXPECTED.
LOW PRESSURE WILL ZIP ACROSS SOUTHERN CANADA SUNDAY WITH A COLD
FRONT ARRIVING SUNDAY EVENING. WAA AHEAD OF THIS SYSTEM WILL BRING
A QUICK REBOUND OF TEMPS BACK INTO THE 20S. COULD SEE SOME
FLURRIES ACROSS CNTRL MN AND WI WHERE MOISTURE DEPTH AND FORCING
SHOULD BE GREATER...OTHERWISE THE COLD FRONT WILL BE DRY. VERY
STRONG CAA BEHIND THE FRONT WILL BRING STEADY OR FALLING TEMPS
INTO THE SINGLE DIGITS COME MONDAY AS 925 MB TEMPS CRASH TO -18C.
A RIDGE WILL SETTLE OVERHEAD MONDAY NIGHT. CLEAR SKIES...LIGHT
WINDS...AND A VERY COLD AIRMASS SHOULD ALLOW MOST PLACES TO
PLUMMET INTO THE TEENS BELOW ZERO...AND PERHAPS TO 20 BELOW IN
SOME OF THE COLDEST LOCATIONS. THE PLACEMENT OF THE RIDGE WILL BE
CRUCIAL. GFS HAS BEEN FURTHEST EAST WITH IT AND BRINGS WAA ACROSS
WRN MN LATE MONDAY NIGHT WITH THE COLDEST TEMPS ACROSS WI.
NAM/DGEX/GEM/ECMWF HAVE BEEN A BIT FURTHER WEST WITH THE CORE OF
THE COLD AIR. INTERESTINGLY...THE 29.00Z NAM/GEM...28.18Z
DGEX...AND 28.12Z EURO HAD GOOD CONSISTENCY WITH TEMPS RANGING
FROM NEAR -22F OVER ERN CHIPPEWA CO MN...TO ABOUT -5F IN THE TWIN
CITIES METRO. LEANED TOWARD THOSE RAW SOLUTIONS FOR THIS FORECAST
AND DISCARDED THE GFS. 29.00Z EURO CAME IN A TAD WARMER. WITH
TEMPS SUCH AS THESE...IT WON/T TAKE MUCH TO BRING THE WIND CHILL
WAY DOWN. EVEN A 5 KT WIND WOULD RESULT IN -20 TO -30F.
.LONG TERM...NEW YEARS DAY THROUGH FRIDAY.
RIDGE SETTLES SOUTH WITH RETURN FLOW ALLOWING ANOTHER QUICK
REBOUND OF TEMPS BACK INTO THE TEENS ON NEW YEARS DAY.
ANOTHER SYSTEM ZIPPING ACROSS THE NORTHERN GREAT LAKES WILL BRING
A WEAK FRONT SOUTH ON TUESDAY. MEANWHILE...YET ANOTHER SYSTEM
WILL DIVE SOUTHEAST INTO THE NORTHERN PLAINS TUESDAY NIGHT AND
BRING A STRONG COLD FRONT THROUGH WEDNESDAY OR WEDNESDAY EVENING.
THIS SYSTEM MAY BRING A BIT OF LIGHT SNOW BEFORE ANOTHER SURGE OF
ARCTIC AIR SPILLS SOUTH. COULD SEE A SIMILAR SCENARIO FROM EARLIER
IN THE WEEK WITH LOWS IN THE TEENS BELOW ZERO THURSDAY MORNING AND
HIGHS IN THE SINGLE DIGITS. THIS ONE HAS A LITTLE MORE UNCERTAINTY
WITH THE POTENTIAL FOR CLOUDS TO LINGER SO DID NOT GO TOO CRAZY
WITH TEMPERATURES YET.
&&
.AVIATION.../06Z TAF ISSUANCE/
CONDITIONS VARY SIGNIFICANTLY AT TAF ISSUANCE TIME...RANGING FROM
LIFR AT AXN...RWF...RNH...TO MVFR AT STC AND VFR AT MSP AND EAU.
BREAKS IN MID LEVEL CLOUD COVER HAVE FACILITATED REDEVELOPMENT OF
LOW CLOUDS AND FREEZING FOG...MOST WIDESPREAD ACROSS WRN MN UNDER
THE SURFACE RIDGE AXIS AND MORE PATCHY FURTHER EAST. THINK THE LOW
CLOUDS WILL SPREAD EAST OVERNIGHT AND IMPACT MSP AND EAU BETWEEN
07-09Z. CONDITIONS SHOULD IMPROVE GRADUALLY ON SATURDAY...BUT
CONFIDENCE REMAINS RATHER LOW WITH RESPECT TO TIMING THE RETURN
OF VFR CONDITIONS. CLOUDS MAY PERSIST A BIT LONGER THAN CURRENTLY
ADVERTISED.
KMSP...MSP IS CURRENTLY LOCATED IN A VFR HOLE SURROUNDED BY MVFR
CIGS. SATELLITE INDICATES THIS HOLE IS BEGINNING TO FILL AND MVFR
CIGS SHOULD BEGIN IMPACTING THE TERMINAL BY 08Z. IMPROVING
CONDITIONS ARE EXPECTED SATURDAY MORNING WITH VFR BY AFTERNOON.
/OUTLOOK FOR KMSP/
SUN...VFR. WINDS SSE 5-10 KTS.
MON...VFR. WINDS NW 5-10 KTS.
TUE...VFR. WINDS WSW 5 KTS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
BORGHOFF
AREA FORECAST DISCUSSION
NWS KANSAS CITY/PLEASANT HILL MO
923 PM CST Sun Dec 30 2012
.UPDATE...
/855 PM CST Sun Dec 30 2012/
00Z high res NWP data are still in line with the current fcst for
the upcoming winter storm. Dprog/dt of the HRRR depicts precip to
move in from the southwest by 12z and quickly overspread the CWA.
Upstream 00Z RAOBS resolved a 400 mb lower layer of dry air that
will take some time to saturate before the precip reaches the ground.
The dry air, however, will aid to quickly modify the relatively mild
overnight temps via evaporation (wet bulbing). As that occurs the
precip may begin as -RN then quickly change over to -SN. Of note, the
latest modeled sndgs for the area tomorrow indicate the snow ice
crystal structure will foster compacting suggesting many locations
may realize the lower side of the 2-4" envelope currently forecasted.
Pietrycha
&&
.DISCUSSION...
Overnight and morning model guidance has come into modest agreement
for the winter system that will eject out into the Plains tonight and
Monday. General consensus among most model guidance is on a broad
2-4" snow across most of the forecast area, generally along and south
of the Highway 36 corridor. Confidence in these snow amounts is high
enough that a winter weather advisory has been issued for these areas
from 6 am Mon to 6 am Tues. Latest guidance brings advisory-criteria
snows up to Kirksville so advisory will be expanded northward into
Grundy, Sullivan and Adair Counties with the afternoon package.
For tonight, upper trough swinging across the Upper Midwest will
allow a cold front to drop into far northwest MO by 12Z Mon. This
front will interact with a broad upper trough to the west which will
send a few mid-level impulses into the area Monday and Monday night.
This broad upper lift looks to be the primary forcing mechanism for
this event, and with little in the way of enhanced mesoscale forcing,
precip rates should generally be light with snowfall rates less than
one inch per hour. Best timing for snowfall looks to be between 12Z
and 18Z Monday as one impulse interacts with the front which will be
pushing to near the MO River. A slight enhancement to snowfall rates
near this front could result in a band of about 2"-3" of snow from
Kansas City to Moberly with around 1" on either side. Behind this
first impulse there may be a lull in precipitation Monday afternoon
before a stronger sheared vort max pushes into the region Monday
evening. This second round will be working with decreasing
tropospheric moisture and little mesoscale lift so additional
snowfall amounts look to be about an inch for the entire advisory
area.
Ahead of the front, temperatures may rise into the lower or middle
30s across areas south of Kansas City into Central Missouri. This may
allow snow to mix with or even change to rain across these areas late
Monday morning which throws quite a bit of uncertainty into snowfall
amounts there. Kept snow amounts limited to an inch or so with the
morning round due to potential melting, which may keep storm total
snows closer to 2-inches across the southern forecast area. Further
north where temps should stay below freezing for the entire event,
there could be a few periods of freezing drizzle especially Monday
afternoon and evening when precipitation will become lighter and lift
stays confined to the low-levels. Do not expect icing to be a concern
with this activity though.
Impacts with this system should be relatively minor through the day
Monday since snowfall rates will be light and near-freezing
temperatures should help keep treated surfaces clear. Any problems
Monday morning are likely to be on untreated roadways. Bigger
concern is after dark as the New Years Eve festivities start up, as
falling temperatures will freeze any water/slush that had melted during
the day and create hazardous icy roads, particularly the ones that
are untreated. Round 2 of snowfall will drop up to another inch on
top of this ice which will be particularly hazardous.
Sheared upper trough axis will remain north of the forecast area on
Wednesday, but will drift far enough south to allow a cold Canadian
high to sag southward into the area. Trended below guidance for temps
Weds and Weds night due to anticipated snow cover across the entire
forecast area.
Hawblitzel
Medium Range (Wednesday-Sunday)...
Quiet weather will continue through the medium range portions of the
forecast. A minor shortwave will pass through the CWA on Thursday.
It remains unclear if there will be enough lingering low-level
moisture to squeeze out any flurries over the CWA and thus will
continue not to mention. Thursday will be the coldest day of the medium
range due to cold advection associated with the aforementioned upper
trough. The good news is that mid-level ridging will begin to
increase as we arrive at the weekend. In fact, 850 MB temperatures
will climb between 2C and 4C by Saturday which could result in
readings back in the 40s depending on the impacts of snow.
Dux
&&
.AVIATION...
FOR 00Z TAFS...VFR CIGS AND VIS TO HOLD OVERNIGHT BEFORE -SN DEVELOPS
OVER THE KC-AREA TERMINALS AFTER SUNRISE TOMORROW. IFR CONDITIONS ARE
THEN EXPECTED THROUGH THE REST OF THE PERIOD WITH STEADY -SN THROUGH
EARLY AFTERNOON, FOLLOWED BY A DECREASE IN SNOWFALL RATES AND A
SLIGHT IMPROVEMENT TO VIS THEREAFTER. FURTHERMORE, DURING THE
AFTERNOON HOURS THE SNOW MAY CHANGE OVER TO -FZDZ BUT CONFIDENCE IN
THIS SCENARIO IS TOO LOW AT THIS TIME TO INTRODUCE INTO THE TAFS.
NOTE, JUST BEYOND THE END OF THE TAF PERIOD, ANOTHER BAND OF -SN IS
EXPECTED TO DEVELOP AND PERSIST INTO THE OVERNIGHT HOURS.
Pietrycha
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER WEATHER ADVISORY from 6 AM Monday to 6 AM CST Tuesday FOR
MOZ012>017-020>025-028>033-037>040-043>046-053-054.
KS...WINTER WEATHER ADVISORY from 6 AM Monday to 6 AM CST Tuesday FOR
KSZ025-057-060-102>105.
&&
$$
WFO EAX
AREA FORECAST DISCUSSION
NWS GREAT FALLS MT
1025 PM MST Fri Dec 28 2012
Updated Aviation
.DISCUSSION...
Update forthcoming. Have made a few adjustments to the pop and
weather grids this evening. Weak instability associated with a
passing shortwave has resulted in a little light snow in the West
Yellowstone area. This was depicted well on the 18z GFS run and also
with the HRRR analysis. The GFS decreases precipitation chances
after midnight as upper ridging develops over the area. Southwest
winds will continue overnight and keep temperatures generally above
zero. Emanuel
&&
.AVIATION...
Updated 0600Z.
VFR conditions will prevail at all TAF sites through Saturday
afternoon. Some mid- and upper-level clouds will move over the area
tonight and thicken during the day on Saturday ahead of the next
disturbance. Winds will remain light around 10 to 15 kts tonight
along the Rocky Mountain Front and then increase again by midday
Saturday. As the next disturbance moves into the forecast area by
Saturday afternoon for areas along the Continental Divide and
southwest Montana including KBZN and KHLN, light snow and MVFR
conditions may develop though any snow amounts will be light. Light
snow may spread into the plains later Saturday evening and Saturday
night and have added VCSH to all TAFs though confidence is low. Some
mountain obscuration is expected tonight with widespread mountain
obscuration by Saturday afternoon. MLV
&&
.PREV DISCUSSION...ISSUED 255 PM MST Fri Dec 28 2012
Tonight through Sunday...Current radar shows quiet conditions
throughout the area and will remain quiet through Saturday
evening. A shortwave will move across the area Saturday night
bringing light snow to most locations. Expect one inch or less in
the valleys and adjacent plains and generally 1 to 3 inches in the
mountains. Impacts with this system are expected to be minimal.
Light snow will taper off during the day on Sunday and will push out
of the area by Sunday evening. Main change to the forecast package
was to raise pops on Sunday...by using a model blend of the NAM and
SREF. Temperatures remain cool...and near seasonal averages on
Saturday...then dropping about 10 degrees on Sunday in the wake of
the shortwave. Mercer
Sunday Night through Thursday...Generally good agreement among
models through period. An upper level ridge of high pressure will
slowly build into Pacific Northwest. Daytime high temperatures will
warm to above normal for much of the forecast area Tuesday and will
remain through Friday. In the far northeast, cold air may remain
trapped in the Milk River Valley so have lowered temperatures a bit
in this area. With higher pressure over the Continental Divide,
breezy downslope winds will be common during the period. This ridge
will be quite dry, too, with downslope winds there will be little or
no chance of snow even over the mountains. Only possible exception
to this will be during the Wednesday time frame. Models diverge a
bit at this time with the GFS dropping shortwave energy and a weak
surface cold front through eastern Montana. Have tweaked pops up a
bit over my far eastern zones but am expecting the remainder of the
forecast area to remain dry. Models keep the ridge in place over the
northern Rockies through the end of the week so have dried out
precipitation for the entire area during this period. Britton/mpj
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 18 34 20 25 / 0 0 70 50
CTB 17 32 7 24 / 0 30 50 0
HLN 11 27 16 24 / 0 0 50 40
BZN 7 23 13 21 / 0 0 70 50
WEY 2 19 8 19 / 10 10 60 40
DLN 7 27 16 23 / 0 10 70 40
HVR 9 28 11 23 / 0 10 60 20
LWT 14 33 16 24 / 0 0 40 60
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
AREA FORECAST DISCUSSION
NWS BINGHAMTON NY
1253 PM EST SAT DEC 29 2012
.SYNOPSIS...
LOW PRESSURE WILL TRACK ACROSS THE MID ATLANTIC REGION THIS AFTERNOON,
SPREADING 3 TO 7 INCHES OF SNOW ACROSS MUCH OF UPSTATE NY AND
NORTHEAST PA. A NORTHWEST FLOW BEHIND THIS LOW PRESSURE SYSTEM WILL
GENERATE LAKE EFFECT SNOW SHOWERS FOR UPSTATE NEW YORK FOR THE
REST OF THE WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
IR AND WATER VAPOR IMAGERY SHOW AN IMPRESSIVE UPPER LEVEL WAVE
MOVING INTO WRN PA/NY W VA. COOLING CLOUD TOPS CONTINUE ACRS NY
AND NRN PA ASSCTD WITHE STRONG MID-LEVEL ASCENT. THE TROP PRESSURE
ON THE 1.5 PV SURFACE WAS DOWN TO 560 MB AS PER THE LATEST RAP IN
THE ERN OH VLLY. THIS MATCHED VERY WELL WITH THE SATELLITE DEPICTION
OF THE CENTER OF THE UPPER LEVEL CRLCN. THIS UPPER LEVEL WAVE WILL
MOVE INTO ERN NY BY 2-3Z AS ANOTHER UPR LVL PV INTRUSION...DOWN
TO 490 MB...DEVELOPS OFF THE COAST INDICATIVE OF THE TRANSFER OF THE
MAIN ENERGY TO THE DEVELOPING COASTAL LOW. PRESENTLY THE UPPER
LEVEL WAVE IN THE ERN OH VLLY HAD A SFC REFLECTION MOVING INTO WRN PA
THAT WILL EVENTUALLY GET SWALLOWED UP BY THE DEEPENING SFC CYCLONE
OFF THE E COAST BY THIS EVENING. THIS LOW WILL BE WELL EAST OF THE NJ
COAST BY 00Z. BELIEVE THE HEAVIEST SNOW WILL TAPER DOWN BY LATE
AFTERNOON AS THE MAIN LIFTING WITH THIS UPPER LEVEL WAVE SHIFTS TO
THE EAST. LIGHTER SNOWS WILL PERSIST INTO THE EARLY EVENING.
THE SATELLITE CONTS TO REVEAL THAT THE DEEPER MOISTURE REMAINS OFF
THE EAST COAST AND WAS THE MAIN REASON WHY THIS STORM LIKELY WON/T
BECOME A MAJOR EVENT FOR OUR AREA AS THE UPPER LEVEL WAVE JUST IS
NOT TAPPING INTO THE DEEPER MOISTURE OFFSHORE FOR OUR AREA.
BELIEVE MOST OF OUR FORECAST AREA SEES BETWEEN 4 AND 7
INCHES...WITH BETWEEN 3 AND 6 INCHES IN SCRANTON/WILKES BARRE
AREA/POCONOS WHERE CURRENT SNOW REPORTS SHOW THAN LESS THAN 1
INCH HAS OCCURRED THERE SO FAR. THE BULK OF THEIR SNOW WILL COME
WITH A SIGNIFICANT BAND OF HEAVIER SNOW MOVING INTO SC PA ATTM.
WILL CONTINUE WITH WINTER WEATHER ADVISORIES ALL ZONES. IF SNOW
REPORTS APPROACH 5-6 ICNHES BY 1 PM AND RADAR TRENDS CONTINUES TO
SHOW REDEVELOPMENT TO THE SOUTHWEST MAY HAVE TO UPGRADE TO WINTER
STORM WARNING IN SOME AREAS. DON/T THINK THIS WILL BE THE
CASE...BUT IT COULD COME CLOSE SOME AREAS IN C NY/NRN PA. LATEST
12Z NAM SNOWFALL PROJECTIONS SHOW A SOLID 4-6 INCHES SUPPORTING ADVY.
MOST OF OUR SNOWFALL REPORTS IN NY AND FAR NRN PA ARE 2-3 INCHES
WITH THE SCRANTON AREA LESS THAN 1 INCH AS STATED ABOVE.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
CONTINUING WW ADVISORY TODAY. LATEST MODEL PROGS SUGGEST A VERY
WIDESPREAD SWATH OF 3 TO 5 INCHES OF SNOW ACROSS FA, WITH
POTENTIAL FOR 6-7 INCHES OVER THE VERY HIGH TERRAIN OF THE POCONOS
AND WESTERN CATSKILLS.
THERE ARE CONCERNS WHICH COULD HINDER SNOWFALL AMOUNTS, INCLUDING
RELATIVELY SHALLOW MOIST LAYER AND FAST MOVEMENT OF SYSTEM.
HOWEVER ATMOSPHERIC DYNAMICS ARE VERY STRONG AND CONFIDENCE IS NOW
HIGH FOR ADVISORY ACCUMS. OF NOTE IS IMPRESSIVE PV INTRUSION
VISIBLE DOWN TO 600-500MB ON NAM.
STORM WILL PULL OUT THIS EVENING, WITH A COLD NORTHWEST FLOW
GENERATING LAKE BANDS OFF OF ONTARIO. PRE-EXISTING LL MOIST LAYER
COMBINED WITH LAKE INDUCED INSTABILITY (850MB TEMPS -10C TO -12C)
WILL BE SOMEWHAT TEMPERED BY SHEAR IN THE LOW LAYERS. EXPECT AN
INCH OR TWO OF LAKE SNOW BY SUNDAY AFTERNOON, WHEN INVERSION
BUILDS DOWN AND HIGH PRESSURE STARTS TO LOCK IN.
SUNDAY NIGHT INTO MONDAY...HIGH PRESSURE, FAIR WEATHER, AND A
BRIEF MODERATION IN TEMPERATURES BACK TOWARD SEASONAL NORMS. SHORT
WAVE APPROACHES MONDAY NIGHT, GENERATING LIGHT SNOW SHOWERS.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
2 AM UPDATE...
VRY FEW CHGS NEEDED TO LONG TERM AS IT APPEARS TO BE A PROLONGED
PD OF LK EFFECT ACTIVITY EACH DAY UNDER COLD NW FLOW DROPPING
SOUTH OUT OF CANADA. CDFNT LOOKS TO MV THRU ON THURSDAY, THUS HV
LOWERED MIN TEMPS FOR FRI MRNG AND AGAIN FOR MAXES ON FRIDAY.
SINGLE DIGITS APPEAR LKLY FOR FRIDAY MORNING WITH PERHAPS SOME
LOCALES DROPPING BLO ZERO.
PREV DISCO BLO...
1 PM UPDATE...
FOLLOWED HPC GUIDANCE. A COLD SPELL WITH BELOW NORMAL TEMPERATURES
BUT NO MAJOR CYCLONES AND HEAVY SNOW. MOSTLY LAKE EFFECT. MONDAY
NIGHT STARTS WITH A COLD FRONT BRINGING A REINFORCING SHOT OF COLD
AIR. LIGHT SNOW WITH THE FRONT THEN LAKE EFFECT. THE REST OF THE
EXTENDED MORE OF THE SAME. ANOTHER COLD FRONT THU OR FRI BUT AGAIN
NOT TAPPING ANY ATLANTIC OR GULF MOISTURE. COLDEST DAY OF WEEK
FRIDAY WITH LOWS IN SINGLE DIGITS.
&&
.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
1230 PM UPDATE...
IFR VSBYS MAJORITY OF THE DAY WITH SNOW HEAVY AT TIMES. IFR CIGS
TOO MOSTLY AT THE HIGHER ELEV SITES OF BGM AND ITH. SOME VSBYS
UNDER A QUARTER MILE IN HEAVY SNOW THIS AFTN WILL DROP CONDITIONS
BELOW FLIGHT MINIMUMS. IFR TO CONTINUE THROUGH THE EVENING BEFORE THE
SNOW TAPERS OFF LATE TONIGHT. LOW LEVEL FLOW SHIFTS TO NW THIS
EVENING PROVIDING LAKE EFFECT ENHANCEMENT TO THE LINGERING SNOW.
FOR SUNDAY MVFR CONDITIONS IN NY WITH LAKE EFFECT SNOW SHOWERS AND
VFR AT KAVP.
E WINDS AT 5 TO 10 KTS SHIFTING TO NW LATE THIS AFTN...THEN
CONTINUING TONIGHT. SUNDAY NW WINDS AT 10 TO 15 KTS.
OUTLOOK...
SUN AFTN AND NGT...MVFR/IFR POSSIBLE FOR CNY TERMINALS...IN LAKE
EFFECT SN ACTIVITY.
MON...VFR.
MON NGT TO WED NGT...MVFR/IFR ESPECIALLY FOR CNY TERMINALS.
THU...VFR.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...WINTER WEATHER ADVISORY UNTIL 9 PM EST THIS EVENING FOR
PAZ038>040-043-044-047-048-072.
NY...WINTER WEATHER ADVISORY UNTIL 9 PM EST THIS EVENING FOR NYZ009-
015>018-022>025-036-037-044>046-055>057-062.
&&
$$
SYNOPSIS...DJP
NEAR TERM...DJN
SHORT TERM...DJP
LONG TERM...PVN/TAC
AVIATION...TAC
AREA FORECAST DISCUSSION
NWS BINGHAMTON NY
1036 AM EST SAT DEC 29 2012
.SYNOPSIS...
LOW PRESSURE WILL TRACK ACROSS THE MID ATLANTIC REGION THIS AFTERNOON,
SPREADING 3 TO 7 INCHES OF SNOW ACROSS MUCH OF UPSTATE NY AND
NORTHEAST PA. A NORTHWEST FLOW BEHIND THIS LOW PRESSURE SYSTEM WILL
GENERATE LAKE EFFECT SNOW SHOWERS FOR UPSTATE NEW YORK FOR THE
REST OF THE WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
IR AND WATER VAPOR IMAGERY SHOW AN IMPRESSIVE UPPER LEVEL WAVE
MOVING INTO WRN PA/NY W VA. COOLING CLOUD TOPS CONTINUE ACRS NY
AND NRN PA ASSCTD WITHE STRONG MID-LEVEL ASCENT. THE TROP PRESSURE
ON THE 1.5 PV SURFACE WAS DOWN TO 560 MB AS PER THE LATEST RAP IN
THE ERN OH VLLY. THIS MATCHED VERY WELL WITH THE SATELLITE DEPICTION
OF THE CENTER OF THE UPPER LEVEL CRLCN. THIS UPPER LEVEL WAVE WILL
MOVE INTO ERN NY BY 2-3Z AS ANOTHER UPR LVL PV INTRUSION...DOWN
TO 490 MB...DEVELOPS OFF THE COAST INDICATIVE OF THE TRANSFER OF THE
MAIN ENERGY TO THE DEVELOPING COASTAL LOW. PRESENTLY THE UPPER
LEVEL WAVE IN THE ERN OH VLLY HAD A SFC REFLECTION MOVING INTO WRN PA
THAT WILL EVENTUALLY GET SWALLOWED UP BY THE DEEPENING SFC CYCLONE
OFF THE E COAST BY THIS EVENING. THIS LOW WILL BE WELL EAST OF THE NJ
COAST BY 00Z. BELIEVE THE HEAVIEST SNOW WILL TAPER DOWN BY LATE
AFTERNOON AS THE MAIN LIFTING WITH THIS UPPER LEVEL WAVE SHIFTS TO
THE EAST. LIGHTER SNOWS WILL PERSIST INTO THE EARLY EVENING.
THE SATELLITE CONTS TO REVEAL THAT THE DEEPER MOISTURE REMAINS OFF
THE EAST COAST AND WAS THE MAIN REASON WHY THIS STORM LIKELY WON/T
BECOME A MAJOR EVENT FOR OUR AREA AS THE UPPER LEVEL WAVE JUST IS
NOT TAPPING INTO THE DEEPER MOISTURE OFFSHORE FOR OUR AREA.
BELIEVE MOST OF OUR FORECAST AREA SEES BETWEEN 4 AND 7
INCHES...WITH BETWEEN 3 AND 6 INCHES IN SCRANTON/WILKES BARRE
AREA/POCONOS WHERE CURRENT SNOW REPORTS SHOW THAN LESS THAN 1
INCH HAS OCCURRED THERE SO FAR. THE BULK OF THEIR SNOW WILL COME
WITH A SIGNIFICANT BAND OF HEAVIER SNOW MOVING INTO SC PA ATTM.
WILL CONTINUE WITH WINTER WEATHER ADVISORIES ALL ZONES. IF SNOW
REPORTS APPROACH 5-6 ICNHES BY 1 PM AND RADAR TRENDS CONTINUES TO
SHOW REDEVELOPMENT TO THE SOUTHWEST MAY HAVE TO UPGRADE TO WINTER
STORM WARNING IN SOME AREAS. DON/T THINK THIS WILL BE THE
CASE...BUT IT COULD COME CLOSE SOME AREAS IN C NY/NRN PA. LATEST
12Z NAM SNOWFALL PROJECTIONS SHOW A SOLID 4-6 INCHES SUPPORTING ADVY.
MOST OF OUR SNOWFALL REPORTS IN NY AND FAR NRN PA ARE 2-3 INCHES
WITH THE SCRANTON AREA LESS THAN 1 INCH AS STATED ABOVE.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
CONTINUING WW ADVISORY TODAY. LATEST MODEL PROGS SUGGEST A VERY
WIDESPREAD SWATH OF 3 TO 5 INCHES OF SNOW ACROSS FA, WITH
POTENTIAL FOR 6-7 INCHES OVER THE VERY HIGH TERRAIN OF THE POCONOS
AND WESTERN CATSKILLS.
THERE ARE CONCERNS WHICH COULD HINDER SNOWFALL AMOUNTS, INCLUDING
RELATIVELY SHALLOW MOIST LAYER AND FAST MOVEMENT OF SYSTEM.
HOWEVER ATMOSPHERIC DYNAMICS ARE VERY STRONG AND CONFIDENCE IS NOW
HIGH FOR ADVISORY ACCUMS. OF NOTE IS IMPRESSIVE PV INTRUSION
VISIBLE DOWN TO 600-500MB ON NAM.
STORM WILL PULL OUT THIS EVENING, WITH A COLD NORTHWEST FLOW
GENERATING LAKE BANDS OFF OF ONTARIO. PRE-EXISTING LL MOIST LAYER
COMBINED WITH LAKE INDUCED INSTABILITY (850MB TEMPS -10C TO -12C)
WILL BE SOMEWHAT TEMPERED BY SHEAR IN THE LOW LAYERS. EXPECT AN
INCH OR TWO OF LAKE SNOW BY SUNDAY AFTERNOON, WHEN INVERSION
BUILDS DOWN AND HIGH PRESSURE STARTS TO LOCK IN.
SUNDAY NIGHT INTO MONDAY...HIGH PRESSURE, FAIR WEATHER, AND A
BRIEF MODERATION IN TEMPERATURES BACK TOWARD SEASONAL NORMS. SHORT
WAVE APPROACHES MONDAY NIGHT, GENERATING LIGHT SNOW SHOWERS.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
2 AM UPDATE...
VRY FEW CHGS NEEDED TO LONG TERM AS IT APPEARS TO BE A PROLONGED
PD OF LK EFFECT ACTIVITY EACH DAY UNDER COLD NW FLOW DROPPING
SOUTH OUT OF CANADA. CDFNT LOOKS TO MV THRU ON THURSDAY, THUS HV
LOWERED MIN TEMPS FOR FRI MRNG AND AGAIN FOR MAXES ON FRIDAY.
SINGLE DIGITS APPEAR LKLY FOR FRIDAY MORNING WITH PERHAPS SOME
LOCALES DROPPING BLO ZERO.
PREV DISCO BLO...
1 PM UPDATE...
FOLLOWED HPC GUIDANCE. A COLD SPELL WITH BELOW NORMAL TEMPERATURES
BUT NO MAJOR CYCLONES AND HEAVY SNOW. MOSTLY LAKE EFFECT. MONDAY
NIGHT STARTS WITH A COLD FRONT BRINGING A REINFORCING SHOT OF COLD
AIR. LIGHT SNOW WITH THE FRONT THEN LAKE EFFECT. THE REST OF THE
EXTENDED MORE OF THE SAME. ANOTHER COLD FRONT THU OR FRI BUT AGAIN
NOT TAPPING ANY ATLANTIC OR GULF MOISTURE. COLDEST DAY OF WEEK
FRIDAY WITH LOWS IN SINGLE DIGITS.
&&
.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
12Z UPDATE...
MVFR AND IFR EXPECTED MAJORITY OF THE DAY AS SNOW MOVES INTO THE
REGION. EXPECT IFR CONDS TO MOVE INTO KSYR AND KRME AFTER 14Z AND
BY 1230Z AT KBGM. ELSEWHERE REMAINDER OF TERMINALS SHOULD START
OFF THE TAF VALID TIME AT IFR. IFR CONDS CONTINUE INTO THE EVENING
HOURS AS LAKE EFFECT SNOW SHOWERS WILL KICK IN ON THE BACKSIDE OF
THE DEPARTING SYSTEM. FURTHER SOUTH AWAY FROM THE LAKES, KELM, KBGM
AND KAVP EXPECTED TO GO MVFR AFTER 06Z.
WINDS LIGHT AND VARIABLE EARLY ON THEN BECOME MORE SOUTHEASTERLY AROUND
5KTS THROUGHOUT THE MORNING HOURS THEN BECOMING NORTHWEST AFTER
22Z AND INCREASING TO NEAR 10KTS.
OUTLOOK...
SUN THROUGH TUE...MVFR/IFR POSSIBLE FOR CNY TERMINALS...IN LAKE
EFFECT SN ACTIVITY.
WED...VFR. SOME MVFR-IFR -SHSN KSYR/KRME.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...WINTER WEATHER ADVISORY UNTIL 9 PM EST THIS EVENING FOR
PAZ038>040-043-044-047-048-072.
NY...WINTER WEATHER ADVISORY UNTIL 9 PM EST THIS EVENING FOR NYZ009-
015>018-022>025-036-037-044>046-055>057-062.
&&
$$
SYNOPSIS...DJP/DJN
NEAR TERM...DJN
SHORT TERM...DJP
LONG TERM...PVN/TAC
AVIATION...PVN
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
639 AM EST SAT DEC 29 2012
.SYNOPSIS...
LOW PRESSURE MOVING NORTHEAST OFF THE COAST TODAY WILL BRING RAIN
THROUGH THE FIRST HALF OF TODAY. THIS LOW WILL INTENSIFY AS IT
MOVES AWAY SUNDAY...BRINGING GUSTY NORTHWEST WINDS AND MUCH
COOLER TEMPERATURES. HIGH PRESSURE BUILDS ACROSS THE AREA
MONDAY...BEFORE A COLD FRONT CROSSES THE CAROLINAS TUESDAY
BRINGING A CHANCE FOR SHOWERS. THIS FRONT STALLS SOUTH OF THE AREA
WEDNESDAY...AND A LOW PRESSURE MAY DEVELOP ALONG THIS AND BRING
MORE RAIN TO THE REGION LATE IN THE WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 630 AM SATURDAY...EVERY FORECAST MODEL INCLUDING THE RUC AND
HRRR ARE STRUGGLING BADLY WITH THE RAPIDLY EVOLVING LOW PRESSURE
NEAR GEORGETOWN. MESONET AND BUOY DATA HAS BEEN INVALUABLE IN
LOCATING THE COASTAL FRONT THAT EXTENDS FROM 10 MILES EAST OF
WRIGHTSVILLE BEACH...ACROSS KURE BEACH TO NEAR SOUTHPORT...TO ABOUT
15 MILES EAST OF MYRTLE BEACH...TO NEAR THE MOUTH OF THE SANTEE
RIVER SOUTH OF GEORGETOWN. THE MESONET SITE ON BALD HEAD ISLAND HAS
A SOUTH WIND WITH 61 DEGREES...WHILE BOLIVIA IN CENTRAL BRUNSWICK
COUNTY HAS A NORTH WIND AND 47 DEGREES. TEMPERATURES HAVE BEEN
FALLING IN WILMINGTON FOR THE PAST 90 MINUTES AS STRONG PRESSURE
FALLS AND FRONTOGENETIC PROCESSES ARE PACKING TEMPERATURE ISOTHERMS
TIGHTER NEAR THE FRONT. THE FEW LUCKY LOCATIONS ON THE COAST THAT
HAVE GOTTEN INTO THE SUBTROPICAL AIRMASS WILL SEE THEIR WINDS WHIP
AROUND TO THE NORTHWEST WITHIN THE NEXT 60-90 MINUTES AS THE LOW
RACES UP THE COAST AND THE COLDER AIR SURGES BACK OFFSHORE. RADAR
SHOWS THE BACK EDGE OF THE MODERATE TO OCCASIONALLY HEAVY SHOWER
ACTIVITY WILL BE APPROACHING DARLINGTON AND FLORENCE IN LESS THAN
TWO HOURS...AND MAY BE OFF THE COAST BY 10-11 AM. THIS IS EVEN
FASTER THAN MY PREVIOUS FORECAST UPDATE SHOWED.
IN ADDITION TO ALL THE MANUAL ADJUSTMENTS TO THE FORECAST MENTIONED
ABOVE...HIGH TEMPERATURES WILL PROBABLY NOT BE ABLE TO REACH THE 60S
ALONG ANY PORTION OF THE SOUTH CAROLINA COAST OR ANY NC COASTAL
LOCATIONS ASIDE FROM BALD HEAD ISLAND AND SOUTHPORT...SO I HAVE
ADJUSTED HIGHS DOWN SEVERAL DEGREES INTO THE UPPER 50S WHICH IS
ITSELF CONTINGENT ON ENOUGH SUNSHINE DEVELOPING THIS AFTERNOON TO
OFFSET THE COLD ADVECTION BEHIND THE DEPARTING LOW. PREVIOUS
DISCUSSION FROM 300 AM FOLLOWS...
A COMPLEX SURFACE PATTERN THIS MORNING CONSISTS OF LOW PRESSURE JUST
EAST OF PENSACOLA WITH A SECOND CENTER NORTH OF KNOXVILLE. A COASTAL
FRONT 30-40 MILES EAST OF THE CAROLINA COAST EXTENDS BACK INTO THE
LOW NEAR PENSACOLA. THIS FLORIDA LOW IS QUICKLY BECOMING THE
DOMINANT FEATURE AND WILL RAPIDLY MOVE NORTHEAST ALONG THE FRONT
THIS MORNING...CROSSING OUR PORTION OF THE EASTERN CAROLINAS SHORTLY
AFTER DAYBREAK. IN THE UPPER LEVELS TWO SHORTWAVES ARE ROUNDING THE
BASE OF THE LONGWAVE TROUGH IN THE PLAINS STATES. ONE DISTURBANCE
WILL PASS JUST NORTH OF THE CAROLINAS THIS MORNING...WHILE THE
SECOND WILL FOLLOW A PATH ACROSS THE CAROLINAS TONIGHT.
MOIST ISENTROPIC LIFT ALONG THE 305K-310K SURFACES (8000-14000 FT
AGL) SHOULD RESULT IN WIDESPREAD RAIN THROUGH MID-MORNING. NEAR THE
COAST LAPSE RATES ALOFT WILL STEEPEN SUFFICIENTLY TO GENERATE
200-500 J/KG OF ELEVATED CAPE WHICH MAY RESULT IN ISOLATED
THUNDERSTORMS TOO. COMPARED TO PREVIOUS FORECASTS...00Z SYNOPTIC
MODELS PLUS MORE RECENT MESOSCALE MODEL RUNS SHOW RAIN RAPIDLY
CLEARING OUT FROM WEST TO EAST THIS MORNING. PRECIPITATION MAY SHUT
DOWN WEST OF I-95 BY 930 AM...AND MAY GET OFF THE COAST BY 11 AM. I
WILL BUILD A LITTLE FUDGE FACTOR INTO MY FORECAST POPS TO ACCOUNT
FOR UNCERTAINTY BUT AM STILL INDICATING DRY CONDITIONS THIS
AFTERNOON WITH SKIES BECOMING MOSTLY CLEAR TO PARTLY CLOUDY.
POST-FRONTAL MOISTURE PLUS COLD MID-LEVEL AIR ASSOCIATED WITH THE
SECOND UPPER DISTURBANCE THIS EVENING COULD RESULT IN A TEMPORARY
INCREASE IN CLOUDINESS...BUT ISENTROPIC DOWNGLIDE THROUGH THE MOIST
LAYER ON THE 285K SURFACE SHOULD PRECLUDE ANY PRECIPITATION.
TEMPERATURES PROBABLY HAVE THE LARGEST UNCERTAINTY WITH TODAY`S
FORECAST. THE COASTAL FRONT WILL SEPARATE SUBTROPICAL AIR OFFSHORE
FROM A COOL WEDGE-LIKE AIRMASS INLAND. IF THIS BOUNDARY SNEAKS
FARTHER ONSHORE THAN EXPECTED WE SHOULD HAVE A TEMPERATURE BUST FOR
THE BEACH TOWNS PLUS WILMINGTON. (2 AM TEMPERATURES ARE ALREADY IN
THE UPPER 60S OUT AT THE FRYING PAN SHOALS BUOY!) FARTHER INLAND OUR
TEMPERATURE FORECAST CONFIDENCE IS A LITTLE BETTER SINCE THERE IS A
MUCH SMALLER CHANCE OF WARM AIR SNEAKING IN AHEAD OF THE LOW. EVEN
WITH SOME SUNSHINE THIS AFTERNOON TEMPERATURES WILL STRUGGLE INTO
THE MID TO UPPER 50S INLAND WITH A FEW LOWER 60S AT THE COAST. COLD
ADVECTION ON BREEZY WEST WINDS TONIGHT SHOULD DROP LOWS INTO THE
LOWER 30S INLAND AND MID 30S AT THE COAST.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 300 AM SATURDAY...CLEAR AND COLD SUNDAY AS HIGH PRESSURE
BUILDS ACROSS THE CAROLINAS BEHIND A DEPARTING COLD FRONT. STRONG
PRESSURE GRADIENT BETWEEN ADVANCING HIGH AND DEPARTING SYSTEM IN THE
CANADIAN MARITIMES CREATES GUSTY NW WINDS THROUGH THE DAY. ALTHOUGH
MID-LEVEL CAA PERSISTS THROUGH THE DAY...1000-850MB THICKNESSES
ACTUALLY INCREASE AS SURFACE HIGH BUILDS EASTWARD. THIS WILL HELP
MODIFY TEMPS SOMEWHAT...AND HAVE BUMPED SUNDAY`S HIGHS SLIGHTLY
ALTHOUGH REMAINING WELL BELOW CLIMO...UPPER 40S TO NEAR 50. IT WILL
FEEL EVEN COLDER THANKS TO THE BITING WINDS THOUGH...AND WIND CHILLS
WILL ECLIPSE 40 DEGREES ONLY FOR A FEW HOURS. HIGH PRESSURE SITS
OVERHEAD SUNDAY NIGHT AND WITH A VERY DRY COLUMN IN PLACE (PWATS
LESS THAN ONE-QUARTER INCH)...VERY GOOD RADIATIONAL COOLING WILL
OCCUR. EXPECT MINS SUNDAY NIGHT TO BOTTOM OUT IN THE MID 20S...LOW
20S IN THE TYPICALLY COLDEST SPOTS...BUT AROUND 30 AT THE IMMEDIATE
COAST.
HIGH PRESSURE DRIFTS OFFSHORE MONDAY AND WARMER RETURN FLOW AIR
WORKS BACK INTO THE AREA. THIS HELPS TEMPS RISE TO AROUND
CLIMO...BUT ALSO INCREASES MOISTURE AND CLOUD COVER. DO NOT
ANTICIPATE MUCH IN THE WAY OF SHOWERS MONDAY...AND WHAT DOES OCCUR
WILL BE OVERNIGHT INTO TUESDAY MORNING AHEAD OF AN ADVANCING COLD
FRONT. TIME HEIGHTS SHOW CONSIDERABLE DRY AIR PERSISTING UNTIL WELL
AFTER DARK WHICH SHOULD INHIBIT ANY RAINFALL FOR MOST OF THE
PERIOD...BUT SOME MID-LEVEL LIFT SHOULD SQUEEZE OUT A FEW
SHOWERS...MOSTLY ACROSS NW PORTIONS OF THE CWA...BEFORE DAYBREAK
TUESDAY. WILL CONTINUE INHERITED SCHC POP FOR THAT AREA OVERNIGHT.
MINS WILL BE HELD IN CHECK THANKS TO THE CLOUD COVER AND SOUTHERLY
WINDS...FALLING ONLY TO AROUND 40 MONDAY NIGHT.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 300 AM SATURDAY...TWO WEAK SYSTEMS TO AFFECT THE AREA DURING
THE EXTENDED...ALONG WITH CONTINUED BELOW-CLIMO TEMPS THROUGH THE
WEEK.
GUIDANCE HAS COME INTO MUCH BETTER AGREEMENT IN THE EVOLUTION OF THE
MID-LEVEL PATTERN THROUGH NEXT WEEK. THE WEEK WILL BE DOMINATED BY
SPLIT FLOW AT 500MB...WITH A LARGE CUTOFF LOW ANCHORED ACROSS THE
SOUTHWEST THROUGH EARLY THURSDAY. THE SPLIT FLOW KEEPS SYSTEMS WEAK
AND MOVING QUICKLY ACROSS THE NATION...WHILE MARGINAL CONFLUENCE
ACROSS THE EAST ALLOWS FOR ARCTIC AIR TO INTRUDE ACROSS THE
NORTH...MODIFYING SLIGHTLY THROUGH THE CAROLINAS.
A NORTHERN STREAM LOW DRAPES A COLD FRONT ACROSS THE AREA ON TUESDAY
BRINGING WITH IT A CHANCE FOR SHOWERS AS IT SINKS SOUTHWARD THROUGH
THE DAY. LITTLE OF ANY UPPER SUPPORT IS EVIDENT IN THE
GUIDANCE...AND MOISTURE FLUX AHEAD OF THE FRONT IS LIMITED...SO NOT
A BIG QPF MAKER FOR THE REGION. FRONT STALLS SOUTH ON WEDNESDAY AND
MUCH OF THE DAY WILL BE DRY...ALBEIT WITH CONTINUED MID/UPPER
CLOUDS. THURSDAY IS A MORE INTERESTING DAY AS THE SOUTHWEST CLOSED
LOW FINALLY OPENS AND EJECTS INTO THE FLOW...RACING EAST TO BECOME
OFFSHORE BY FRIDAY MORNING. AT THE SAME TIME...A NORTHERN STREAM
SHORTWAVE MAY TRY TO PHASE WITH THIS FEATURE TO CREATE A COASTAL LOW
ALONG THE RESIDUAL FRONT AND BRING MORE SIGNIFICANT RAINFALL TO THE
REGION. ATTM...DUE TO THE SPEED OF THE FLOW ALOFT...THINK PHASING IS
A MUCH LESS LIKELY SOLUTION...AND BEING THIS FAR OUT IN TIME WILL
SHOW CHC POP THURSDAY WITH A WEAKER AND FASTER LOW MOVING AWAY BY
FRIDAY MORNING...WITH COLD AND DRY CONDITIONS EXPECTED BEHIND IT.
TEMPS THROUGH THE PERIOD WILL BE SLIGHTLY BELOW CLIMO FOR
HIGHS...AND SLIGHTLY ABOVE FOR LOWS WITH CLOUDS/RAIN INHIBITING
GREAT NOCTURNAL COOLING.
&&
.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
AS OF 12Z...PRETTY CRAZY TEMPERATURE GRADIENT BETWEEN ILM AND BALD
HEAD ISLAND...43F VERSES 63F. GOOD ISENTROPIC LIFT ALONG THE WARM
FRONT WILL GIVE US MVFR/IFR CONDITIONS IN MODERATE TO HEAVY RAIN FOR
THE NEXT FEW HOURS. A RUMBLE OF THUNDER IS POSSIBLE AT THE MYRTLES
WHERE SOME INSTABILITY WILL RESIDE. NORTHEAST WINDS WILL HANG IN AT
THE NORTHERN TERMINALS THROUGH AT LEAST 14Z...AS THE WEDGE TRIES TO
DIG IN. A BRIEF SHIFT TO THE SOUTH IS POSSIBLE IF THE WARM FRONT
MANAGES TO MOVE NORTHWARD. COLD FRONT AND APPROACHING LOW WILL
WHISKS THEIR WAY THROUGH THE REGION BY LATE MORNING...WITH A
NOTICEABLE WIND SHIFT TO THE WEST. CONDITIONS IMPROVING TO VFR THIS
AFTERNOON WITH GUSTY WEST WINDS.
EXTENDED OUTLOOK...VFR CONDITIONS EXPECTED SUNDAY AND MONDAY. CHANCE
FOR RAIN TUESDAY. VFR EXPECTED WEDNESDAY.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 630 AM SATURDAY...MESONET AND BUOY DATA HAS BEEN INVALUABLE IN
LOCATING THE FRONT THIS MORNING WHICH CURRENTLY EXTENDS FROM 10
MILES EAST OF WRIGHTSVILLE BEACH...ACROSS KURE BEACH TO NEAR
SOUTHPORT...TO ABOUT 15 MILES EAST OF MYRTLE BEACH...AND TO NEAR THE
MOUTH OF THE SANTEE RIVER SOUTH OF GEORGETOWN. EAST OF THIS BOUNDARY
WINDS ARE 25 TO 30 KNOTS FROM THE SOUTH...WHILE TO THE WEST OF THE
BOUNDARY A SLIGHTLY WEAKER NORTHERLY WIND IS BLOWING. LOW PRESSURE
HAS RACED NORTH FROM FLORIDA THIS MORNING AND IS ANALYZED NEAR THE
SANTEE RIVER CURRENTLY. THE LOW SHOULD MOVE TO NEAR CAPE FEAR BY 730
AM...AND THEN EAST OF SURF CITY SHORTLY AFTER 800 AM. AS THE LOW
PUSHES NORTH OF THE AREA THE COLDER AIR WILL SURGE BACK OUT ACROSS
THE COASTAL WATERS WITH NORTHWESTERLY WINDS REPLACING ANY REMAINING
WARM SOUTHERLY WINDS. THIS IS AN EXTREMELY DYNAMIC SITUATION THAT NO
COMPUTER MODEL IS CAPTURING VERY WELL. SHOWERS AND EMBEDDED
THUNDERSTORMS WILL CONTINUE THROUGH MID MORNING BEFORE DRIER AIR
ARRIVES FROM THE WEST AND ERODES THE PRECIPITATION. SEAS SHOULD
SPIKE UP BY SEVERAL FEET IN THE NEXT HOUR OR TWO DUE TO THE STRONG
(NEARLY GALE-FORCE) WINDS OFFSHORE. PREVIOUS DISCUSSION FROM 300 AM
FOLLOWS...
A COASTAL FRONT ABOUT 30-40 MILES OUT FROM THE COAST WILL MOVE VERY
CLOSE TO THE BEACHES THIS MORNING... POTENTIALLY MAKING IT ONSHORE
AROUND CAPE FEAR AND NEAR GEORGETOWN. LOW PRESSURE OVER NORTHERN
FLORIDA WILL RACE NORTHEAST ALONG THIS FRONT...MOVING OVER THE
CAROLINA COASTLINE ABOUT AN HOUR AFTER SUNRISE. AFTER THIS LOW MOVES
NORTH OF THE AREA THE FRONT WILL BE PUSHED BACK OFFSHORE WITH COOLER
WESTERLY WINDS EXPECTED FOR THE REMAINDER OF TODAY. WINDS WILL VEER
NORTHWESTERLY AROUND MIDNIGHT TONIGHT AS A RENEWED SURGE OF COLD AIR
BLOWS ACROSS THE CAROLINAS.
SMALL CRAFT ADVISORIES WILL REMAIN POSTED FOR WINDS AND FOR LARGE
SEAS EXPECTED TO DEVELOP. NEARSHORE WIND SPEEDS ALONE WOULD PROBABLY
NOT BUILD SEAS TO 6 FEET...BUT MUCH STRONGER WINDS BLOWING GALE
FORCE OR STRONGER OVER THE GULF STREAM WILL PRODUCE LARGE SEAS THAT
WILL SPREAD INTO THE AREA SHORTLY AFTER DAYBREAK. SEAS COULD BUILD
TO 7-9 FEET WITHIN 20 MILES OF SHORE...ESPECIALLY NEAR FRYING PAN
SHOALS. SEAS WILL SHIFT TO MORE SHORT-PERIOD WIND WAVES WITH THE
OFFSHORE WINDS EXPECTED THIS AFTERNOON INTO TONIGHT.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 300 AM SATURDAY...GUSTY NW WINDS BEHIND A DEPARTING COLD FRONT
WILL BE 20-25 KTS EARLY SUNDAY...AND A SMALL CRAFT ADVISORY WILL BE
ONGOING AT THE START OF THE PERIOD. THESE WINDS WILL EASE RATHER
QUICKLY HOWEVER...AND ANY ADVISORIES WILL EXPIRE SUNDAY AFTN. AS
HIGH PRESSURE BUILDS EAST TOWARDS...AND THEN OVER...THE WATERS
SUNDAY NIGHT AND MONDAY WINDS DROP TO 10 KTS OR LESS FROM THE
NORTH...BEFORE BACKING TO THE SW AT AROUND 10 KTS LATE MONDAY AND
THROUGH THE END OF THE PERIOD. SEAS WILL BE HIGHEST EARLY SUNDAY
WHEN THE GUSTY NW WINDS HELP DRIVE THEM TO 3-5 FT. THE COMBINATION
OF DECREASING WIND SPEEDS PLUS THE NW FETCH DIRECTION QUICKLY CAUSES
SEAS TO DROP TO 1-3 FT SUNDAY NIGHT...AND THEN PERSIST AT THESE
HEIGHTS THROUGH MONDAY.
LONG TERM /TUESDAY THROUGH WEDNESDAY/...
AS OF 300 AM SATURDAY...W/SW WINDS OF 10-15 KTS START THE PERIOD AS
THE WATERS EXIST IN A PRE-FRONTAL AIRMASS. WINDS INCREASE GRADUALLY
THROUGH TUESDAY AS COLD FRONT APPROACHES FROM THE NW...BEFORE
VEERING TO THE NW BEHIND FROPA EARLY WEDNESDAY...AGAIN AT 10-15 KTS.
FRONT STALLS SOUTH OF THE WATERS DURING WEDNESDAY...SO WINDS VEER TO
THE NORTH AND REMAIN FROM THIS DIRECTION AT AROUND 10 KTS THROUGH
WED NIGHT. SEAS OF 2-3 FT EARLY TUESDAY RISE BRIEFLY TO AS MUCH AS
3-5 FT EARLY WEDNESDAY IMMEDIATELY AHEAD OF THE COLD FRONT...BEFORE
RETURNING AGAIN TO 2-3 FT BY THE END OF THE PERIOD. SEAS WILL BE
NEARLY ENTIRELY WIND-WAVE DRIVEN THROUGH THE EXTENDED.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 PM EST SUNDAY FOR
AMZ250-252-254- 256.
&&
$$
SYNOPSIS...JDW
NEAR TERM...TRA
SHORT TERM...JDW
LONG TERM...JDW
AVIATION...DL
AREA FORECAST DISCUSSION
NWS NEWPORT/MOREHEAD CITY NC
340 AM EST SAT DEC 29 2012
.SYNOPSIS...
LOW PRESSURE WILL APPROACH FROM THE SOUTHWEST TONIGHT AND MOVE
ALONG THE COAST SATURDAY. STRONG HIGH PRESSURE WILL BUILD IN FROM
THE WEST SUNDAY AND EXTEND OVER THE AREA MONDAY. A COLD FRONT WITH
LIMITED MOISTURE WILL MOVE THROUGH THE AREA TUESDAY THEN STALL TO
THE SOUTH WEDNESDAY AND THURSDAY.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
AS OF 1245 AM SAT...MINOR ADJUSTMENTS WITH UPDATE. PATCHY -RA WILL
CONTINUE NEXT COUPLE OF HOURS WITH MORE WDSPRD ACTIVITY DEVELOPING
AFTER 3AM.
PREV DISC...SHORTWAVE RIDGING AND HIGH PRES MOVE EWD TONIGHT AS A
ROBUST SHORTWAVE TROUGH AND SFC LOW REFLECTION PUSH ACROSS THE
SOUTHEAST. CLOUDS WILL CONTINUE TO LOWER THROUGH THE EVENING WITH
ISENTROPIC LIFT INCREASING AFTER MIDNIGHT WITH LITTLE COND PRES
DEFICITS AFTER 09Z. WINDS WILL CONTINUE TO BE LIGHT MOST OF THE
OVERNIGHT BUT INCREASING OUT OF THE S/SE TO AROUND 10-15 MPH LATE
COASTAL SECTIONS AS A WARM FRONT STRENGTHENS ALONG THE IMMEDIATE
COAST. CLOUDS AND EVENTUALLY PCPN WILL KEEP DIURNAL TEMPS RANGE TO
A MINIMUM WITH LOWS AROUND 40 INLAND AND L/M 40S COAST.
&&
.SHORT TERM /TODAY/...
AS OF 330 PM FRIDAY...ISENTROPIC LIFT STRONGEST THROUGH THE
MORNING HOURS SAT AS DEEPENING LOW PRES LIFTS NE ALONG THE FRONTAL
BOUNDARY PROGGED TO BE ALIGNED ALONG THE COAST. GENERALLY
STRATIFORM RAIN INLAND BUT COULD SEE ISOLATED CONVECTION ALONG THE
COAST WHERE WEAK MU CAPE AND HIGHER DEWPOINTS WILL RESIDE. MODEL
QPF AROUND A QUARTER TO HALF INCH WITH UP TO AN INCH NEAR THE
COAST IN WETTER MODEL SOLUTIONS. WINDS CONTINUE LIGHT INLAND
THROUGH THE MORNING HOURS BUT ARE EXPECTED TO INCREASE OUT OF THE
S/SW TO 15-25 MPH MID TO LATE MORNING ALONG THE COAST. ONCE THE
LOW PUSHES OFF THE COAST AROUND MID DAY AND DEEPENS AS IT LIFTS
AWAY FROM THE AREA...WINDS SHIFT TO WLY AND INCREASE TO AROUND
15-20 MPH WITH GUSTS TO 25 MPH INLAND AND 20-30 MPH WITH GUSTS TO
AROUND 35 MPH ALONG THE COAST. MAX TEMPS EXPECTED IN THE L/M50S
INLAND TO U50S TO AROUND 60 COAST.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
AS OF 310 AM SAT...SURFACE RIDGE ACROSS THE MID MISSISSIPPI VALLEY
WILL CONTINUE TO PUSH EAST OVER THE REGION SUN INTO MON. WEAK UPPER
LEVEL RIDGE WILL PASS WELL SOUTH OF THE REGION SUN INTO MON WHICH
WILL SHIFT NW FLOW ALOFT TO ZONAL WESTERLY FLOW BY MON. TEMPS WILL
BE SEVERAL DEGREES BELOW CLIMO SUN AND MON WITH LOW LEVEL THICKNESSES
RANGING 1290-1300 METERS SUN TO AROUND 1320 METERS MON. THESE VALUES
WILL YIELD TEMPS IN THE MID 40S SUN TO LOWER 50S MON...UNDER FULL
INSOLATION BOTH DAY. COLDEST NIGHT OF THE EXTENDED WILL BE SUN
NIGHT WITH LIGHT CAA/NW FLOW WHICH WILL DROP TEMPS INTO THE MID
20S INLAND TO LOW 30S ALONG THE OBX.
SURFACE RIDGE MOVES OFFSHORE MON EVENING/NIGHT AHEAD OF AN APPROACHING
LOW PRESSURE SYSTEM DEVELOPING ACROSS DEEP SOUTH AL/MS. SURFACE
WINDS WILL BECOME SW MON EVENING ALLOWING WEAK WAA TO INITIATE
AHEAD OF THE FRONTAL SYSTEM. LIGHT PRECIP SHOULD BEGIN NEW YEARS
DAY MORNING AND CONTINUE CLOUDY/LIGHT RAIN THROUGH TUES NIGHT WHEN
THE WEAK FRONT BECOMES SHUNTED SOUTH OF EASTERN NC. MINOR ADJUSTMENTS
TO POPS/WX WITH FAIRLY GOOD AGREEMENT BETWEEN LATEST MEDIUM GUIDANCE.
BEST FORCING FOR LARGE SCALE ASCENT WILL REMAIN NORTH OF THE REGION
SO EXPECT LOW QPF...RANGING 0.15-0.25 INCHES TUES/TUES NIGHT. WITH
THE SURFACE BOUNDARY SOUTH OF EASTERN NC ON WED...EXPECT MOSTLY DRY
CONDITIONS WITH N/NE CAA HOLDING TEMPS 50-55 DEGREES.
THE SOUTHERN STREAM REMAINS ACTIVE WITH ANOTHER LOW PRESSURE SYSTEM
PASSING SOUTHEAST OFF THE COAST ON THURS INTO THURS NIGHT. HIGH
PRESSURE ACROSS THE OHIO RIVER VALLEY WILL PUSH SE ACROSS EASTERN NC
FRI INTO THE WEEKEND WITH TEMPS FALLING BACK BELOW CLIMO.
&&
.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
SHORT TERM /THROUGH 06Z SUNDAY/...
AS OF 1230 AM SAT...MVFR CIGS HAVE DEVELOPED AT KPGV AND KISO AND
EXPECTED MVFR KEWN AND KOAJ BY AROUND 09Z WAS RAIN CONTINUES TO
SPREAD IN FROM SW. ALL MOS GDNC SUPPORTS IFR CIGS DEVELOPING AROUND
12Z AS RAIN BECOMES WDSPRD...AND CONTINUING THROUGH MORNING WITH LOW
PRES MOVING ALONG COAST. RAIN WILL END BY EARLY AFTN WITH CONDITIONS
IMPROVING TO VFR BY LATE AFTN AS DRIER AIR MOVES IN BEHIND DEPARTING
LOW...WITH WINDS BECOMING GUSTY FROM WEST.
LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 320 AM SAT...PREDOMINANT VFR CONDITIONS EXPECTED SUN AND MON
AS HIGH PRESSURE TRAVERSES THE REGION. WINDS SHIFT SW LATE MON AS
HIGH PRESSURE SHIFTS OFFSHORE AHEAD OF AN APPROACHING FRONTAL
SYSTEM TUES INTO WED. EXPECT SUB-VFR CONDITIONS MAINLY IN LOWERED
CEILINGS TUES AFTERNOON THROUGH EARLY WED...THEN RETURN TO VFR WED
MIDDAY AS THE FRONT SHIFTS WELL SE OF THE TERMINALS.
&&
.MARINE...
SHORT TERM /THROUGH SATURDAY/...
AS OF 1245 AM SAT...DEVELOPING WARM FRONT BNDRY IS REMAINING A BIT
FARTHER OFFSHORE...RESULTING IN WINDS REMAINING NE OVER CENTRAL AND
SRN WATERS. LATEST NAM12 AND HRRR HAVE BEST HANDLE ON THIS AND
UPDATED FOR OVERNIGHT INTO SAT MORNING WITH BLEND OF THESE MODELS.
INITIAL WEAK SFC WAVE DEVELOPMENT ALONG BNDRY WILL LIKELY KEEP WINDS
NE UNTIL STRONGER LOW MOVES UP DURING MORNING HOURS.
PREV DISC...LOW PRES WILL TRACK ALONG THE SOUTHEAST WITH A WARM
FRONT STRENGTHENING ALONG THE COAST TONIGHT. THE DEEPENING LOW PRES
SYSTEM WILL LIFT NE ACROSS ERN NC SAT MORNING AND OFFSHORE DURING
THE AFTERNOON. S/SELY WINDS WILL INCREASE AFTER MIDNIGHT TONIGHT AND
ARE EXPECTED TO REACH SMALL CRAFT ADVISORY CRITERIA SHORTLY AFTER 8
AM ACROSS THE COASTAL WATERS SOUTH OF OREGON INLET. THE LOW PUSHES
OFF THE COAST AROUND MID DAY WITH WINDS SHIFTING TO WESTERLY AND
INCREASING AS PRES GRADIENTS TIGHTEN AND EXPECT WINDS ACROSS THE
REST OF THE WATERS TO REACH SMALL CRAFT CRITERIA IN THE AFTERNOON.
FOLLOWED WAVEWATCH CLOSELY FOR SEAS WHICH BUILD QUICKLY SAT MORNING
AND APPROACHING THEIR PEAK AROUND 5-8 FT SRN WATERS AND 4-6 FT NRN
WATERS LATE AFTERNOON.
LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 330 AM SAT...SCA CONDITIONS WILL CONTINUE ACROSS ALL COASTAL
WATERS AND SOUNDS SUN AS STRONG PRESSURE GRADIENT WILL PRODUCE NW
WINDS GUSTING TO 30 KTS AND ELEVATED SEAS ACROSS THE COASTAL
WATERS. SURFACE RIDGE BUILDS EAST OVER THE WATERS LATE SUN INTO
MON WHICH WILL REDUCE THE PRESSURE GRADIENT AND ALLOW SCAS TO END
BY MON MORNING. WINDS SHIFT SW MON NIGHT WITH SEAS RANGING 2-4
FT. SW/WSW WINDS INCREASE 15-20 KT MON NIGHT INTO TUES BUT EXPECT
CONDITIONS TO REMAIN BELOW SCA CRITERIA. WEAK COLD FRONT WILL SAG
SOUTHEAST THROUGH THE WATERS TUES NIGHT INTO WED WITH WINDS
SHIFTING NW BY WED MORNING. GRADIENT WILL REMAIN MODERATE AND VOID
OF STRONG CAA...SO EXPECT NW WINDS 10-15 KTS WED AND SEAS 3-5 FT.
GENERALLY USED WAVEWATCH III GUIDANCE FOR THE EXTENDED THROUGH
TUES HOWEVER WWIII WINDS WERE TOO LOW ON WED SO MANUALLY ADJUSTED
FOR THAT TIME PERIOD. OVERALL MINOR TWEAKS TO SEAS FROM PREVIOUS
FORECAST PACKAGE.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 10 PM EST SUNDAY FOR
AMZ135.
SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 10 PM EST
SUNDAY FOR AMZ130.
SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 6 AM EST MONDAY
FOR AMZ152-154.
SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 6 PM EST SUNDAY
FOR AMZ156-158.
SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 AM EST MONDAY FOR
AMZ150.
&&
$$
SYNOPSIS...SK
NEAR TERM...JBM/SK
SHORT TERM...SK
LONG TERM...DAG
AVIATION...JBM/DAG
MARINE...JBM/SK/DAG
AREA FORECAST DISCUSSION
NWS NEWPORT/MOREHEAD CITY NC
120 AM EST SAT DEC 29 2012
.SYNOPSIS...
LOW PRESSURE WILL APPROACH FROM THE SOUTHWEST TONIGHT AND MOVE
ALONG THE COAST SATURDAY. STRONG HIGH PRESSURE WILL BUILD IN FROM
THE WEST SUNDAY AND EXTEND OVER THE AREA MONDAY. A COLD FRONT WITH
LIMITED MOISTURE WILL MOVE THROUGH THE AREA TUESDAY THEN STALL TO
THE SOUTH WEDNESDAY AND THURSDAY.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
AS OF 1245 AM SAT...MINOR ADJUSTMENTS WITH UPDATE. PATCHY -RA WILL
CONTINUE NEXT COUPLE OF HOURS WITH MORE WDSPRD ACTIVITY DEVELOPING
AFTER 3AM.
PREV DISC...SHORTWAVE RIDGING AND HIGH PRES MOVE EWD TONIGHT AS A
ROBUST SHORTWAVE TROUGH AND SFC LOW REFLECTION PUSH ACROSS THE
SOUTHEAST. CLOUDS WILL CONTINUE TO LOWER THROUGH THE EVENING WITH
ISENTROPIC LIFT INCREASING AFTER MIDNIGHT WITH LITTLE COND PRES
DEFICITS AFTER 09Z. WINDS WILL CONTINUE TO BE LIGHT MOST OF THE
OVERNIGHT BUT INCREASING OUT OF THE S/SE TO AROUND 10-15 MPH LATE
COASTAL SECTIONS AS A WARM FRONT STRENGTHENS ALONG THE IMMEDIATE
COAST. CLOUDS AND EVENTUALLY PCPN WILL KEEP DIURNAL TEMPS RANGE TO
A MINIMUM WITH LOWS AROUND 40 INLAND AND L/M 40S COAST.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
AS OF 330 PM FRIDAY...ISENTROPIC LIFT STRONGEST THROUGH THE
MORNING HOURS SAT AS DEEPENING LOW PRES LIFTS NE ALONG THE FRONTAL
BOUNDARY PROGGED TO BE ALIGNED ALONG THE COAST. GENERALLY
STRATIFORM RAIN INLAND BUT COULD SEE ISOLATED CONVECTION ALONG THE
COAST WHERE WEAK MU CAPE AND HIGHER DEWPOINTS WILL RESIDE. MODEL
QPF AROUND A QUARTER TO HALF INCH WITH UP TO AN INCH NEAR THE
COAST IN WETTER MODEL SOLUTIONS. WINDS CONTINUE LIGHT INLAND
THROUGH THE MORNING HOURS BUT ARE EXPECTED TO INCREASE OUT OF THE
S/SW TO 15-25 MPH MID TO LATE MORNING ALONG THE COAST. ONCE THE
LOW PUSHES OFF THE COAST AROUND MID DAY AND DEEPENS AS IT LIFTS
AWAY FROM THE AREA...WINDS SHIFT TO WLY AND INCREASE TO AROUND
15-20 MPH WITH GUSTS TO 25 MPH INLAND AND 20-30 MPH WITH GUSTS TO
AROUND 35 MPH ALONG THE COAST. MAX TEMPS EXPECTED IN THE L/M50S
INLAND TO U50S TO AROUND 60 COAST.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
AS OF 245 PM FRIDAY...AT THE BEGINNING OF THE PERIOD...COLD FRONT
WILL BE MOVING OFFSHORE TAKING ANY PRECIPITATION WITH IT SATURDAY
EVENING. UPPER HEIGHTS BUILD AS SURFACE HIGH PRESSURE SETTLES OVER
THE CAROLINAS SUNDAY AND MONDAY. SUNDAY WILL BE CHILLY WITH
MAXIMUM TEMPERATURES MAINLY IN THE MIDDLE AND UPPER 40S WITH LOWS
BY MONDAY MORNING IN THE 20S EXCEPT LOWER TO MIDDLE 30S ALONG THE
IMMEDIATE COAST. SOME SLIGHT MODERATION IN TEMPERATURES ON MONDAY
AS LOW-LEVEL FLOW VEERS BACK TO THE SOUTHWEST AS LOW-LEVEL WARM
AIR ADVECTION PUSHES MAXIMUM TEMPERATURES INTO THE LOWER 50S. BOTH
SUNDAY AND MONDAY SHOULD BE DRY WITH A GOOD AMOUNT OF SUNSHINE.
A SOUTHERN STREAM SYSTEM BRINGS A RETURN OF RAIN TO THE AREA FOR
TUESDAY AFTERNOON THROUGH TUESDAY NIGHT. THE SOUTHERN STREAM
REMAINS ACTIVE WITH ANOTHER SYSTEM ON THURSDAY INTO THURSDAY
NIGHT. MODELS STILL AGREE THAT THIS SYSTEM WILL BE SUPPRESSED TO
THE SOUTH...BUT THERMAL PROFILES KEEP THE COLUMN WELL ABOVE
CRITICAL THICKNESS VALUES...SO EXPECT ONLY RAIN. BOTH THE GFS AND
ECMWF KEEP CONDITIONS DRY BUT RATHER COLD FOR NEXT WEEKEND.
&&
.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
SHORT TERM /THROUGH 06Z SUNDAY/...
AS OF 1230 AM SAT...MVFR CIGS HAVE DEVELOPED AT KPGV AND KISO AND
EXPECTED MVFR KEWN AND KOAJ BY AROUND 09Z WAS RAIN CONTINUES TO
SPREAD IN FROM SW. ALL MOS GDNC SUPPORTS IFR CIGS DEVELOPING AROUND
12Z AS RAIN BECOMES WDSPRD...AND CONTINUING THROUGH MORNING WITH LOW
PRES MOVING ALONG COAST. RAIN WILL END BY EARLY AFTN WITH CONDITIONS
IMPROVING TO VFR BY LATE AFTN AS DRIER AIR MOVES IN BEHIND DEPARTING
LOW...WITH WINDS BECOMING GUSTY FROM WEST.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 245 PM FRIDAY...SUB VFR CONDITIONS ARE EXPECTED EARLY
SATURDAY AS LOW PRESSURE MOVES THRU THE AREA WITH WIDESPREAD
PRECIP. CONDITIONS WILL BE IMPROVING AS THE LOW MOVES NE SAT AFTN.
MOSTLY VFR CONDITIONS ARE ANTICIPATED SUNDAY AND MONDAY AS HIGH
PRESSURE INFLUENCES THE WEATHER. PRECIP MAY BREAK OUT AHEAD OF A
FRONTAL SYSTEM LATE TUESDAY WITH SOME SUB VFR CONDITIONS POSSIBLE
ATTM.
&&
.MARINE...
SHORT TERM /THROUGH SATURDAY/...
AS OF 1245 AM SAT...DEVELOPING WARM FRONT BNDRY IS REMAINING A BIT
FARTHER OFFSHORE...RESULTING IN WINDS REMAINING NE OVER CENTRAL AND
SRN WATERS. LATEST NAM12 AND HRRR HAVE BEST HANDLE ON THIS AND
UPDATED FOR OVERNIGHT INTO SAT MORNING WITH BLEND OF THESE MODELS.
INITIAL WEAK SFC WAVE DEVELOPMENT ALONG BNDRY WILL LIKELY KEEP WINDS
NE UNTIL STRONGER LOW MOVES UP DURING MORNING HOURS.
PREV DISC...LOW PRES WILL TRACK ALONG THE SOUTHEAST WITH A WARM
FRONT STRENGTHENING ALONG THE COAST TONIGHT. THE DEEPENING LOW PRES
SYSTEM WILL LIFT NE ACROSS ERN NC SAT MORNING AND OFFSHORE DURING
THE AFTERNOON. S/SELY WINDS WILL INCREASE AFTER MIDNIGHT TONIGHT AND
ARE EXPECTED TO REACH SMALL CRAFT ADVISORY CRITERIA SHORTLY AFTER 8
AM ACROSS THE COASTAL WATERS SOUTH OF OREGON INLET. THE LOW PUSHES
OFF THE COAST AROUND MID DAY WITH WINDS SHIFTING TO WESTERLY AND
INCREASING AS PRES GRADIENTS TIGHTEN AND EXPECT WINDS ACROSS THE
REST OF THE WATERS TO REACH SMALL CRAFT CRITERIA IN THE AFTERNOON.
FOLLOWED WAVEWATCH CLOSELY FOR SEAS WHICH BUILD QUICKLY SAT MORNING
AND APPROACHING THEIR PEAK AROUND 5-8 FT SRN WATERS AND 4-6 FT NRN
WATERS LATE AFTERNOON.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 245 PM FRIDAY...STRONG COLD AIR ADVECTION BEHIND COLD FRONT
WILL LEAD TO STRONG CRAFT ADVISORY WINDS AND SEAS SATURDAY NIGHT
INTO SUNDAY NIGHT AS THE NORTH CAROLINA COAST WILL LIE IN THE
GRADIENT BETWEEN 1032 MB HIGH OVER KENTUCKY AND STRONG EXITING LOW
PRESSURE OVER THE NORTH ATLANTIC. WIND AND SEAS SUBSIDE MONDAY
INTO TUESDAY AS AXIS OF HIGH PRESSURE SETTLES OVER THE NORTH
CAROLINA COASTAL WATERS AND SOUNDS. A BRIEF PERIOD OF SMALL CRAFT
SEAS AND NEAR SMALL CRAFT LEVEL WINDS WILL LIKELY OCCUR ON THE
BACKSIDE OF ANOTHER SOUTHERN STREAM LOW TUESDAY NIGHT INTO
WEDNESDAY PER LATEST WAVEWATCH 4 GUIDANCE.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON SATURDAY TO 6 PM EST SUNDAY FOR
AMZ135.
SMALL CRAFT ADVISORY FROM 4 PM SATURDAY TO 6 PM EST SUNDAY FOR
AMZ130.
SMALL CRAFT ADVISORY FROM 8 AM SATURDAY TO 6 AM EST MONDAY FOR
AMZ152-154.
SMALL CRAFT ADVISORY FROM 8 AM SATURDAY TO 3 PM EST SUNDAY FOR
AMZ156-158.
SMALL CRAFT ADVISORY FROM NOON SATURDAY TO 6 AM EST MONDAY FOR
AMZ150.
&&
$$
SYNOPSIS...SK
NEAR TERM...JBM/SK
SHORT TERM...SK
LONG TERM...CTC
AVIATION...JBM/CTC
MARINE...JBM/SK/CTC
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
1243 AM EST SAT DEC 29 2012
.SYNOPSIS...
RAIN WILL MOVE INTO THE AREA LATE TONIGHT...PREVAILING THROUGH
SATURDAY MORNING AS LOW PRESSURE SCOOTS NORTHEAST FROM THE GULF
COAST STATES. THE LOW WILL INTENSIFY AS IT MOVES AWAY FROM THE
REGION SATURDAY AFTERNOON AND NIGHT...BRINGING BRISK WEST AND
NORTHWEST WINDS. BUILDING HIGH PRESSURE WILL IMPORT DRIER AND
COLDER AIR SUNDAY AND MONDAY...FOLLOWED BY A WEAK COLD FRONTAL
PASSAGE ON TUESDAY. A STORM SYSTEM OFFSHORE MAY BRING MORE RAIN
TO THE EASTERN CAROLINAS LATE NEXT WEEK.
&&
.NEAR TERM /THROUGH SATURDAY/...
AS OF 1230 AM SATURDAY...I HAVE DELAYED THE ONSET OF PRECIPITATION
BY A FEW HOURS PER RADAR TRENDS AND LATEST HRRR MODEL RUNS. ALSO
SHUT DOWN PRECIP MUCH FASTER SATURDAY AFTERNOON THAN WAS ORIGINALLY
FORECAST. VIRTUALLY NO MODEL GUIDANCE I CAN FIND KEEPS PRECIP
ANYWHERE AFTER 18Z SATURDAY. OTHERWISE NO SIGNIFICANT CHANGES TO
TEMPS/DEWPOINTS/WINDS ARE NEEDED. PREVIOUS DISCUSSION FROM 900 PM
FOLLOWS...
CLOUD COVER AND WEAK WARM SECTOR ADVECTION HAVE NEARLY LEVELED OFF
NOCTURNAL TEMPERATURE CURVES AND SEVERAL SITES POTENTIALLY MAY HAVE
ALREADY REALIZED MINIMUM TEMPERATURES FOR THE NIGHT. SURFACE LOW
NEAR MOBILE ALABAMA WILL MOVE QUICKLY NE OVERNIGHT...BRINGING A
DECENT OVER-RUNNING STRATIFORM TYPE RAINFALL. MOST-USABLE CAPE
ANALYSIS FROM NEAR TERM MODEL SUITES INDICATE ELEVATED INSTABILITY
WILL EXIST ALONG OUR VERY SOUTHERN COAST AT 12Z WITH THE BULK OF
INSTABILITY ALOFT REMAINING NEAR THE COAST AND OFFSHORE MAINLY AFTER
12Z SATURDAY...AND NO THUNDER WILL BE ADVERTISED...AT LEAST FOR THE
OVERNIGHT HOURS.
LIGHT E-NE WINDS OVERNIGHT WILL BECOME S-SE AND INTENSIFY INTO
THE PRE-DAWN HOURS OF SATURDAY...AS AN INVERTED SURFACE TROUGH
POSITIONED JUST OFFSHORE...IS DRAWN CLOSER TO THE COAST. THIS
SHOULD ENSURE RISING T/TD VALUES ACROSS THE EASTERN ZONES INTO
DAYBREAK...WHILE CONCURRENTLY INCREASING THE SURFACE CONVERGENCE
COMPONENT...LOCALLY BOOSTING OMEGA AND THE POTENTIAL FOR EMBEDDED
HEAVIER SHOWERS EARLY SATURDAY MORNING FROM MYR TO SUT TO ILM
TO HAMPSTEAD TO TOPSAIL ISLAND TO SURF CITY.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
AS OF 3 PM FRIDAY...A QUICK SHOT OF WARM AND MOIST AIR AS LOW
PRESSURE RACES ACROSS THE FORECAST AREA SAT MORNING. THIS AREA OF
LOW PRESSURE WILL BE WEAK AND RATHER BROAD AS IT MOVES OVERHEAD.
EXPECT THE MORNING WILL BE WET WITH A MODERATE RAIN FALLING. A
COASTAL TROUGH/WARM FRONT WILL LIE ACROSS THE COASTAL WATERS AND
MAY BRIEFLY SNEAK ONTO LAND DURING SAT MORNING. EXAMINATION OF
STABILITY PARAMETERS SUGGESTS THERE IS A RISK FOR ELEVATED
CONVECTION. THE INSTABILITY IS SMALL AND LIMITED TO AROUND 850
MB...WITH CAPE VALUES UP TO ABOUT 300 J/KG THUS...CAN NOT RULE
OUT A THUNDERSTORM/RUMBLE OF THUNDER...WITH PERHAPS A SLIGHTLY
HIGHER PROBABILITY ON THE COAST. THERE WILL HOWEVER BE NO SEVERE
WEATHER AS THE LOW LEVELS SHOULD REMAIN STABLE ENOUGH EVEN IN THE
VICINITY OF THE COASTAL TROUGH.
LOW PRESSURE WILL CONSOLIDATE AND STRENGTHEN RAPIDLY AS IT MOVES
OFF THE VIRGINIA CAPES SAT AFTERNOON AND THEN OFF THE NEW ENGLAND
COAST SAT NIGHT. THUS THE RAIN WILL SHUTOFF QUICKLY LATE MORNING
THROUGH MIDDAY. AS LOW PRESSURE DEEPENS...WEST TO NORTHWEST WINDS
ON THE BACKSIDE OF THE LOW WILL STRENGTHEN AS THE PRESSURE
GRADIENT TIGHTENS UP ACROSS THE EASTERN CAROLINAS. WINDS ARE
EXPECTED TO GUST TO 25 TO 30 MPH SAT AFTERNOON. THESE WINDS WILL
QUICKLY BRING DRIER AIR INTO THE AREA AND SO THICK MORNING CLOUDS
ARE EXPECTED TO ERODE...GIVING WAY TO PARTLY TO AT TIMES MOSTLY
SUNNY SKIES.
TEMPS WILL BE TRICKY...AND THE BUST POTENTIAL IS HIGH...ESPECIALLY
AT THE COAST WHERE SOUTHERLY WINDS MAY DEVELOP FOR A TIME EARLY
ON. COLDER AND DRIER AIR WILL BE ARRIVING IN THE WAKE OF LOW
PRESSURE...BUT THIS WILL BE MITIGATED BY AFTERNOON SUNSHINE AND
DOWNSLOPING WINDS. AT THIS TIME...WILL FORECAST COOLEST READINGS
ACROSS THE NORTHERN PEE DEE UP THROUGH LBT AND EYF...MID AND UPPER
50S. THERE IS A CHANCE FOR LOWER TO MID 60S FOR PORTIONS OF THE
SOUTHERN PEE DEE TO THE GRAND STRAND AND THEN UP THROUGH THE CAPE
FEAR REGION.
WINDS WILL BE SLOW TO DIMINISH SAT NIGHT AS THE GRADIENT WILL
REMAIN RATHER TIGHT...THUS TEMPS SHOULD BE RATHER UNIFORM ACROSS
THE AREA...LOWER TO MID 30S. SHOULD WINDS GO LIGHT EARLY SUN
MORNING...THERE MAY BE A FEW UPPER 20S WELL INLAND.
CHILLY HIGH PRESSURE WILL BUILD SOLIDLY ACROSS THE AREA SUN AND
SUN NIGHT. EVEN WITH CLOUDLESS SKIES...TEMPS WILL STRUGGLE TO GAIN
ANY UPWARD MOMENTUM. GIVEN 850 MB TEMPS WILL BE MINUS 1 TO MINUS 2
DEG C...EXPECT HIGHS IN THE MID 40S IN MOST LOCATIONS. THE BOTTOM
SHOULD QUICKLY DROP OUT OF THE THERMOMETER SUN NIGHT AS TEMPS FALL
SHARPLY DURING THE EVE. IDEAL RADIATIONAL COOLING IS EXPECTED WITH
LOWS BY MON MORNING IN THE 20S AND AS LOW AS THE LOWER 20S.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 3 PM FRIDAY...SURFACE HIGH PRESSURE AND LOW AMPLITUDE MID
LEVEL RIDGING BOTH GRADUALLY MOVE OFF THE COAST LATER MONDAY.
SHALLOW COOL SFC AIR MASS TO KEEP TEMPS CHILLY ESPECIALLY WITH
LATER DAY INC IN CLOUD COVER. MOISTURE ADVECTION GETS STRONGER
MONDAY NIGHT INTO TUESDAY. APPROACHING COLD FRONT TO ADD LIFT TO
THE ONGOING WARM/MOIST ADVECTION AND SOME LIGHT RAIN SHOULD BREAK
OUT DESPITE MID LEVEL FORCING BEING WEAK IN ZONAL FLOW. WEDNESDAY
WILL BRING A WEAK PUSH OF DRY AIR BEHIND THE BOUNDARY AS IT STALLS
NOT TOO FAR TO OUR SOUTH. MEANWHILE THE NEXT SYSTEMS ALOFT TAKE
SHAPE OVER THE PLAINS AND MEXICO (SPLIT FLOW). THE LATTER SHEARS
OUT AND STREAKS BY RAPIDLY CAUSING A FLAT WAVE OF LOW PRESSURE TO
DEVELOP ALONG THE OFFSHORE BOUNDARY. RAIN MAY ONCE AGAIN
OVERSPREAD THE REGION ON THURSDAY, THIS TIME FROM THE SOUTH. THE
NORTHERN BRANCH FEATURE ENDS UP BECOMING A BROAD POSITIVELY TILTED
TROUGH IN THE EAST THAT WILL HELP KEEP THE AREA VERY CHILLY.
&&
.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
AS OF 06Z...HAVE PUSHED BACK THE ONSET OF PCPN ACROSS THE TERMINALS
AS PER THE LOCAL MODELS THAT SHOW RAIN OVERSPREADING THE REGION FROM
WEST TO EAST AFTER 08Z-10Z. SURFACE LOW TO MOVE RAPIDLY TO THE NE
WITH THE GFS BRINGING THE LOW RIGHT OVER THE CAPE FEAR REGION AND
ITS ASSOCIATED HEAVIER RAIN AS WELL. WILL MENTION A TEMPO GROUP FROM
12Z-15Z FOR THE COASTAL TAFS FOR CHANCE TSRA. SYSTEM MOVES RAPIDLY
TO THE NE WITH PCPN ENDING BY 15-16Z. WINDS SHIFT TO THE W AND PICK
UP TO AROUND 15KTS WITH GUSTS 20-25KTS AFTER 16-18ZZ. MODERATE
DEGREE OF CONFIDENCE IN EXPECTING IFR CEILINGS BETWEEN 12Z-15Z WITH
MAINLY MVFR CONDITIONS BETWEEN 09Z-12Z. VFR CONDITIONS EXPECTED
AFTER 16Z WITH ISOLATED MVFR IN CEILINGS AT THE COASTAL TERMINALS.
EXTENDED OUTLOOK...VFR CONDITIONS EXPECTED SUNDAY AND MONDAY. CHANCE
FOR RAIN TUESDAY. VFR EXPECTED WEDNESDAY.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 1230 AM SATURDAY...RAIN WILL NOT BEGIN UNTIL JUST A FEW HOURS
BEFORE DAYBREAK...BUT THUNDERSTORM CHANCES APPEAR TO BE INCREASING
AS A SLUG OF MODERATELY UNSTABLE AIR WILL DEVELOP JUST A FEW
THOUSAND FEET OVER THE OCEAN SURFACE BETWEEN 6 AM AND 11 AM SATURDAY
MORNING. THE SURFACE WARM FRONT HAS PUSHED ACROSS THE FRYING PAN
SHOALS BUOY LOCATION WHERE SFC WINDS ARE NOW SOUTHEAST. LOOK FOR
WINDS TO SHIFT EVEN NEARSHORE OVER THE NEXT FEW HOURS. THE BIGGEST
CHANGE TO THE FORECAST IS TO DELAY INCREASING SEA HEIGHTS BY SEVERAL
HOURS AS IT WILL TAKE TIME FOR STRONGER WINDS OFFSHORE TO TRANSLATE
INTO LARGER SEAS. THE FRYING PAN SHOALS BUOY IS STILL ONLY 2 FEET AT
LATEST REPORT. PREVIOUS DISCUSSION FROM 900 PM FOLLOWS...
INCREASING WINDS WILL BRING WORSENING MARINE CONDITIONS LATE TONIGHT
INTO EARLY SATURDAY AS AN APPROACHING SFC LOW OVER THE NORTHERN GULF
OF MEXICO MOVES SWIFTLY NE...RAMPING UP SOUTH WINDS OVER THE WATERS.
SEAS OF 2-3 FEET LATE THIS EVENING WILL APPROACH 5-6 FEET NEAR
DAYBREAK WITH POTENTIAL WIND GUSTS TO 25 KT TOWARD 12Z OR 7AM
SATURDAY. DEVELOPING RAIN COULD REDUCE VISIBILITIES TO LESS THAN 2
MILES IN RAIN AND MIST BY SUNRISE.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 3 PM FRIDAY...A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR
ALL WATERS SAT THROUGH MIDDAY ON SUN. WEAK LOW PRESSURE WILL MOVE
OVERHEAD SAT MORNING. A COASTAL TROUGH WILL LIKELY LIE ACROSS THE
WATERS SAT MORNING. LOW PRESSURE WILL INTENSIFY OFF THE VIRGINIA
CAPES...RESULTING IN A TIGHT PRESSURE GRADIENT BY SAT AFTERNOON
AND THIS GRADIENT WILL PERSIST THROUGH SAT NIGHT BEFORE BEGINNING
TO RELAX ON SUN. WILL INITIALIZE WITH A SOUTH WIND...BUT WINDS
WILL SHIFT QUICKLY TO THE W AROUND MIDDAY SAT AND THEN TO THE NW
SAT NIGHT. NNW WINDS SUN WILL BECOME NNE TO NE BY MON MORNING.
WINDS WILL BE AS HIGH AS AROUND 25 KT SAT AFTERNOON AND SAT
NIGHT...FALLING BELOW ADVISORY CRITERIA DURING SUN. SEAS WILL
QUICKLY BUILD SAT MORNING...AS HIGH AS 6 TO 8 FT ACROSS THE OUTER
WATERS. THE WESTERLY WINDS WILL HELP TO KNOCK WAVE HEIGHTS DOWN
ACROSS THE NEAR SHORE WATERS SAT AFTERNOON AND EVE. SEAS SAT NIGHT
WILL BE UP TO 4 TO 6 FT ACROSS THE OUTERMOST WATERS. SEAS WILL
DROP STEADILY DURING THE DAY SUN AND SUN NIGHT.
LONG TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 3 PM FRIDAY...LIGHT WINDS AND DIMINUTIVE SEAS EXPECTED ON
MONDAY AS HIGH PRESSURE MAKES A SLOW EASTWARD TREK FROM THE
LANDMASS TO AN OFFSHORE POSITION. SO WHILE WIND SPEEDS WILL REMAIN
VERY LIGHT THERE SHOULD BE CONSIDERABLE CHANGES IN WIND DIRECTION
THROUGH THE DAY AND EVENING. A SOUTHERLY COMPONENT BECOMES
DOMINANT HOWEVER BY MONDAY NIGHT IN THE RETURN FLOW REGIME ON THE
WESTERN PERIPHERY OF THE ANTICYCLONE. BY TUESDAY THE APPROACH OF A
COLD FRONT WILL TIGHTEN THE GRADIENT SLIGHTLY AND A SMALL INCREASE
IN SEAS WILL BE NOTED. AS THE FRONT PUSHES THROUGH TUESDAY NIGHT A
SHARP VEER TO A NORTHERLY WIND WILL TAKE PLACE. THE BOUNDARY WILL
NOT TRAVEL VERY FAR TO THE SOUTH WHICH SHOULD PRECLUDE ANY BIG
POST-FRONTAL COLD SURGE OF HIGHER WINDS. NEVERTHELESS GUIDANCE
RAMPING UP TO WHERE ADVISORY WOULD BE NEEDED. NOT SURE IF THIS IS
CORRECT SO WILL CAP SEAS AT SCEC-WORTHY 5 FT FOR NOW.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 5 AM SATURDAY TO 1 PM EST
SUNDAY FOR AMZ250-252-254-256.
&&
$$
NEAR TERM...MJC/TRA
SHORT TERM...RJD
LONG TERM...MBB
AVIATION...MAC
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
1115 AM EST SAT DEC 29 2012
.SYNOPSIS...
A WIDESPREAD 3 TO 5 INCH SNOWFALL WILL OCCUR TODAY. A FEW
LOCATIONS COULD GET UP TO 6 INCHES OF SNOW FROM THIS FAST-MOVING
SYSTEM. WINDS WILL TURN TO THE NORTHWEST THIS EVENING AND BECOME
GUSTY WITH SNOW SHOWERS LIKELY DOWNSTREAM OF LAKE ERIE AND IN THE
LAUREL HIGHLANDS. NEXT WEEK LOOKS QUIET WITH ONLY A COUPLE OF WEAK
WEATHER SYSTEMS PASSING BY. THE BIG STORY LATER NEXT WEEK WITH BE
THE POSSIBILITY OF VERY COLD AIR ENTERING THE STATE.
&&
.NEAR TERM /UNTIL 7 PM THIS EVENING/...
THE WESTERN SURFACE LOW IS JUST WEST OF JOHNSTOWN. THE DRY SLOW
IS CLOSE TO THIS FEATURE AND SNOW IN WEST-CENTRAL AREAS HAS
DIMINISHED. THE SHORT-WAVE IS STILL TO THE WEST SO ANOTHER INCH OR
SO OF SNOW IS POSSIBLE UNTIL IT PASSES TO THE EAST EARLY THIS
AFTERNOON. THE SURFACE LOW DEVELOPING ALONG THE COAST IS TAKING
OVER. SECOND MILLER-B WINTER STORM EVOLUTION THIS WEEK.
THE SECONDARY LOW HAS BANDS TO ITS NORTH AND WEST WHICH SHOULD
BRING A PERIOD OF ENHANCED SNOW FALL TO ADAMS...YORK...AND
LANCASTER COUNTIES WHICH SHOULD GET THEM INTO THE 3-4 INCH RANGE
EARLY THIS AFTERNOON. MODIFIED GRIDS TO SHOW THIS.
THE RAP AND HRRR CONTINUE TO SHOW THE SNOW PULLING OUT OF THE REGION
RAPIDLY IN THE 1 PM TO 3 PM RANGE FROM SW TO ENE. INTENSITIES
REALLY DROP OFF FAST BASED ON RAP/HRRR SYNTHETIC RADAR AFTER ABOUT
2 PM EVEN IN THE EAST.
BY ABOUT 5-6 PM ANY ACCUMULATING SNOW SHOULD BE ABOUT OVER. MOSTLY
LIGHT SNOW AND FLURRIES AFTER 5-6 PM OVER MOST OF CWA. LINGERING
IN THE MOUNTAINS.
FOR MOST LOCATIONS THE HEAVIEST SNOW HAS LIKELY FALLEN...EXCEPT IN
THE SOUTHEAST WHERE THE NEXT 0-3 HOURS COULD BE THE BEST.
&&
.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM SUNDAY/...
MONITORING SNOW SHOWER AND ACCUMULATING SNOW IN SW MOUNTAINS AND
NW PA DURING THIS PERIOD. MOST OTHER AREAS TO EAST WILL SEE LITTLE
OR NOW SNOW AFTER 9 PM GIVE OR TAKE 1-3 HOURS. CONSIDERING AND
ADVISORY IN SW MTNS SUNDAY.
PREVIOUS DISCUSSION....THE LOW DEPARTS AND
DEEPENS OFF THE EAST COAST THIS EVENING. RESIDUAL MOISTURE FROM
THE EXITING LOW...COUPLED WITH W/NW FLOW AND UPSLOPE TOPOGRAPHIC
ENHANCEMENT WILL MAKE SNOW SHOWERS ACROSS THE SNOW BELT AND IN THE
LAUREL HIGHLANDS. THESE SHOWERS SHOULD BE MAINLY LIGHT AND SHOULD
DIE DOWN SUNDAY EVENING. THOSE FAVORED/UPSLOPE LOCATIONS IN THE
LAURELS AND DOWNWIND OF THE LAKES COULD PICK UP ANOTHER INCH OR
TWO TONIGHT AND ANOTHER INCH SUNDAY MORNING BEFORE THE FLOW
BECOMES ANTICYCLONIC. THOSE VALUES SHOULD BE JUST SUB- ADVISORY
FOR THEM. BUT ALLOWING LEEWAY...THE CURRENT ADVY FOR THOSE AREAS
COULD BE EXTENDED IF NECESSARY TO COVER THE ADDITIONAL
LAKE/UPSLOPE SNOW. OTHERWISE...SUNDAY WILL BE A BREEZY BUT FAIR
DAY FOR THE REST OF THE AREA. GUSTS COULD BE INTO THE L30S IN THE
SRN MTS AND EAST...BUT NO WORRY OF WIND ADVY. MAX TEMPS ON SUNDAY
WILL BE SIMILAR TO TODAY.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
THE FLOW WILL SHIFT TO A MORE ZONAL PATTERN AS ANOTHER SYSTEM
MAKES ITS WAY TOWARD THE REGION FOR MONDAY NIGHT/NEW YEARS EVE.
THE CURRENT MODELS ARE FAIRLY CONSISTENT AND HAVE SUFFICIENT PWATS
AND LIFT FROM A JET STREAK TO CREATE SNOW SHOWERS OVER AT LEAST
THE WESTERN HALF OF THE AREA MON NIGHT AND TUES MORNING. A FEW
NORTHERN STREAM FEATURES WILL CROSS THE LOWER GREAT LAKES AROUND
MID-WEEK AND MAKE LAKE EFFECT SHOWERS. AN ARCTIC AIR MASS BEGINS
TO MOVE THROUGH SOUTHERN CANADA AND DECREASING 850MB TEMPERATURES
WILL CONTINUE THROUGH THE LATTER HALF OF THE WEEK. CURRENT RUNS
HAVE PA UNDER M16C TEMPERATURES AT 850MB FRIDAY MORNING. THE GFS
AND EC PROPAGATE ANOTHER TROUGH THROUGH PENNSYLVANIA FRIDAY.
EXPECT HIGH TEMPERATURES THIS WEEK TO BE AT OR BELOW
FREEZING...WITH HIGHS IN THE UPPER TEENS POSSIBLE BY THE END OF
NEXT WEEK. COUPLE THE LOW TEMPS WITH THE GUSTY FLOW...AND WIND
CHILLS COULD BE AN ISSUE DURING THIS TIME FRAME. LOWS THROUGH THE
LATER HALF OF THE WEEK SHOULD BE IN THE LOW TEENS.
&&
.AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
THE SNOW HAS REDUCED VISIBILITIES AND CIGS ACROSS THE ENTIRE
REGION. SNOW RATES OF 1 TO 2 INCHES PER HOUR BENEATH BANDS WILL
POSE DEICING ISSUES TOO. CONDITIONS WILL REMAIN POOR THROUGH AT
LEAST 17Z TODAY.
SNOW RATES SHOULD STEADILY DIMINISH SOUTHWEST TO NORTH EAST THIS
AFTERNOON AND EVENING. VISIBILITIES SHOULD RISE TO OVER 3 MILES
LATER THIS EVENING IN MANY SOUTHERN LOCATIONS. PERHAPS VFR A FEW
HOURS BEFORE MIDNIGHT IN THE 02 TO 03Z TIME-FRAME AS THE STORM AND
SNOW LIFTS TO OUR NORTH AND EAST.
GUSTY WINDS APPEAR LIKELY OVERNIGHT TONIGHT INTO SUNDAY WITH
SCATTERED SNOW SHOWERS DEVELOPING IN THE WESTERN AND NORTHWESTERN
MTNS. NWLRY UPSLOPE FLOW WILL LIKELY KEEP FLYING CONDS AT KJST AND
KBFD MARGINAL AFTER THE STORM WITH LOW CLOUDS AND PERIODS OF
LOWERED VISIBILITIES.
MOST OTHER LOCATIONS SHOULD HAVE GENERALLY GOOD FLYING CONDITIONS SUNDAY.
OUTLOOK...
SUN...SHSN AND REDUCED FLIGHT CONDS POSSIBLE WESTERN AND NORTHERN
MTNS.
MON...NO SIG WX EXPECTED.
TUE...CFROPA POSSIBLE. SHSN REDUCED CIGS/VI`S AND GUSTY WINDS
POSS.
WED...MAINLY VFR.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR
PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-
049>053-056>059-063>066.
&&
$$
SYNOPSIS...DANGELO/LA CORTE
NEAR TERM...GRUMM
SHORT TERM...GRUMM/DANGELO
LONG TERM...DANGELO/CERU
AVIATION...GRUMM/GARTNER
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
946 AM EST SAT DEC 29 2012
.SYNOPSIS...
A WIDESPREAD 3 TO 5 INCH SNOWFALL WILL OCCUR TODAY. A FEW
LOCATIONS COULD GET UP TO 6 INCHES OF SNOW FROM THIS FAST-MOVING
SYSTEM. WINDS WILL TURN TO THE NORTHWEST THIS EVENING AND BECOME
GUSTY WITH SNOW SHOWERS LIKELY DOWNSTREAM OF LAKE ERIE AND IN THE
LAUREL HIGHLANDS. NEXT WEEK LOOKS QUIET WITH ONLY A COUPLE OF WEAK
WEATHER SYSTEMS PASSING BY. THE BIG STORY LATER NEXT WEEK WITH BE
THE POSSIBILITY OF VERY COLD AIR ENTERING THE STATE.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SNOW IS FALLING BASICALLY OVER ALL OF THE REGION. VERY LIGHT SNOW
REPORTED IN EASTERN LANCASTER COUNTY. HAD CALLS ABOUT WHEN WILL IT
SNOW! ADJUSTED GRIDS WITH LATEST BLENDED GUIDANCE WHICH CLIPPED
QPF AND THUS SNOWFALL IN SOUTHERN AND EASTERN AREAS. SOME AREAS IN
NORTH-CENTRAL PA SHOW 0.50 INCHES OF QPF. WITH HIGHER RATIOS A FEW
AREAS COULD TOP 6 INCHES. STILL ANTICIPATING MOST LOCATIONS WILL
STAY IN 3-6 INCH RANGE.
SATELLITE SHOWS SHARP DRY SLOT MOVING INTO SW PA. THIS FAVORS SOME
ENHANCE BANDING TO ITS NORTH AND EAST PERHAPS NORTHERN TIER IN A
FEW HOURS. WILL MONITOR ENHANCED CSI EFFECT FROM ABOUT STATE
COLLEGE NORTHWARD THIS AM AND EARLY THIS AFTERNOON. COULD PUSH UP
SNOW TOTALS A BIT TOO. BUT ECHOES ARE WEAKENING BENEATH AND JUST
AHEAD OF IT. THIS CAN BE SEEN ON RADAR IN SW PA...BUT IN ADVANCE
OF IT IS WHERE BEST CSI POTENTIAL WILL BE.
THE RAP AND HRRR SHOW SNOW PULLING OUT OF THE REGION RAPIDLY IN
THE 1 PM TO 3 PM RANGE FROM SW TO ENE. BY ABOUT 5 PM ANY
ACCUMULATING SNOW WOULD BE CONFINED TO NORTHEASTERN AREAS. MOSTLY
LIGHT SNOW AND FLURRIES AFTER 5 PM OVER MOST OF CWA. LINGERING IN
THE MOUNTAINS.
THE BAND IN VA-MD COULD CLIP SOUTHERN YORK AND LANCASTER COUNTIES
BEFORE NOON AND GET THE SNOW FALL TO INCREASE THERE. SOMETHING TO
WATCH IN EXTREME SE. THE 14Z RAP SHOWS SLIGHT ENHANCED SNOW IN
LANCASTER COUNTY AROUND 17Z.
WE HAVE ENTERED THE BEST PERIOD OF HEAVY SNOW AND WILL TRACK IN
NOWCASTS. VISIBILITIES WILL BE LOW OVER MOST OF THE REGION THROUGH
AT LEAST 1 PM AND ROADS WITH 1 TO 2 INCH RATES AT TIMES AT THEIR WORSE.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
MONITORING SNOW SHOWER AND ACCUMULATING SNOW IN SW MOUNTAINS AND
NW PA DURING THIS PERIOD. MOST OTHER AREAS TO EAST WILL SEE LITTLE
OR NOW SNOW AFTER 9 PM GIVE OR TAKE 1-3 HOURS.
PREVIOUS DISCUSSION....THE LOW DEPARTS AND
DEEPENS OFF THE EAST COAST THIS EVENING. RESIDUAL MOISTURE FROM
THE EXITING LOW...COUPLED WITH W/NW FLOW AND UPSLOPE TOPOGRAPHIC
ENHANCEMENT WILL MAKE SNOW SHOWERS ACROSS THE SNOW BELT AND IN THE
LAUREL HIGHLANDS. THESE SHOWERS SHOULD BE MAINLY LIGHT AND SHOULD
DIE DOWN SUNDAY EVENING. THOSE FAVORED/UPSLOPE LOCATIONS IN THE
LAURELS AND DOWNWIND OF THE LAKES COULD PICK UP ANOTHER INCH OR
TWO TONIGHT AND ANOTHER INCH SUNDAY MORNING BEFORE THE FLOW
BECOMES ANTICYCLONIC. THOSE VALUES SHOULD BE JUST SUB- ADVISORY
FOR THEM. BUT ALLOWING LEEWAY...THE CURRENT ADVY FOR THOSE AREAS
COULD BE EXTENDED IF NECESSARY TO COVER THE ADDITIONAL
LAKE/UPSLOPE SNOW. OTHERWISE...SUNDAY WILL BE A BREEZY BUT FAIR
DAY FOR THE REST OF THE AREA. GUSTS COULD BE INTO THE L30S IN THE
SRN MTS AND EAST...BUT NO WORRY OF WIND ADVY. MAX TEMPS ON SUNDAY
WILL BE SIMILAR TO TODAY.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
THE FLOW WILL SHIFT TO A MORE ZONAL PATTERN AS ANOTHER SYSTEM
MAKES ITS WAY TOWARD THE REGION FOR MONDAY NIGHT/NEW YEARS EVE.
THE CURRENT MODELS ARE FAIRLY CONSISTENT AND HAVE SUFFICIENT PWATS
AND LIFT FROM A JET STREAK TO CREATE SNOW SHOWERS OVER AT LEAST
THE WESTERN HALF OF THE AREA MON NIGHT AND TUES MORNING. A FEW
NORTHERN STREAM FEATURES WILL CROSS THE LOWER GREAT LAKES AROUND
MID-WEEK AND MAKE LAKE EFFECT SHOWERS. AN ARCTIC AIR MASS BEGINS
TO MOVE THROUGH SOUTHERN CANADA AND DECREASING 850MB TEMPERATURES
WILL CONTINUE THROUGH THE LATTER HALF OF THE WEEK. CURRENT RUNS
HAVE PA UNDER M16C TEMPERATURES AT 850MB FRIDAY MORNING. THE GFS
AND EC PROPAGATE ANOTHER TROUGH THROUGH PENNSYLVANIA FRIDAY.
EXPECT HIGH TEMPERATURES THIS WEEK TO BE AT OR BELOW
FREEZING...WITH HIGHS IN THE UPPER TEENS POSSIBLE BY THE END OF
NEXT WEEK. COUPLE THE LOW TEMPS WITH THE GUSTY FLOW...AND WIND
CHILLS COULD BE AN ISSUE DURING THIS TIME FRAME. LOWS THROUGH THE
LATER HALF OF THE WEEK SHOULD BE IN THE LOW TEENS.
&&
.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
THE SNOW HAS REDUCED VISIBILITIES AND CIGS ACROSS THE ENTIRE
REGION. SNOW RATES OF 1 TO 2 INCHES PER HOUR BENEATH BANDS WILL
POSE DEICING ISSUES TOO. CONDITIONS WILL REMAIN POOR THROUGH AT
LEAST 17Z TODAY.
SNOW RATES SHOULD STEADILY DIMINISH SOUTHWEST TO NORTH EAST THIS
AFTERNOON AND EVENING. VISIBILITIES SHOULD RISE TO OVER 3 MILES
LATER THIS EVENING IN MANY SOUTHERN LOCATIONS. PERHAPS VFR A FEW
HOURS BEFORE MIDNIGHT IN THE 02 TO 03Z TIME-FRAME AS THE STORM AND
SNOW LIFTS TO OUR NORTH AND EAST.
GUSTY WINDS APPEAR LIKELY OVERNIGHT TONIGHT INTO SUNDAY WITH
SCATTERED SNOW SHOWERS DEVELOPING IN THE WESTERN AND NORTHWESTERN
MTNS. NWLRY UPSLOPE FLOW WILL LIKELY KEEP FLYING CONDS AT KJST AND
KBFD MARGINAL AFTER THE STORM WITH LOW CLOUDS AND PERIODS OF
LOWERED VISIBILITIES.
MOST OTHER LOCATIONS SHOULD HAVE GENERALLY GOOD FLYING CONDITIONS SUNDAY.
OUTLOOK...
SUN...SHSN AND REDUCED FLIGHT CONDS POSSIBLE WESTERN AND NORTHERN
MTNS.
MON...NO SIG WX EXPECTED.
TUE...CFROPA POSSIBLE. SHSN REDUCED CIGS/VI`S AND GUSTY WINDS
POSS.
WED...MAINLY VFR.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR
PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-
049>053-056>059-063>066.
&&
$$
SYNOPSIS...DANGELO/LA CORTE
NEAR TERM...GRUMM/DANGELO
SHORT TERM...GRUMM/DANGELO
LONG TERM...DANGELO/CERU
AVIATION...GRUMM/GARTNER
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
937 AM EST SAT DEC 29 2012
.SYNOPSIS...
A WIDESPREAD 3 TO 5 INCH SNOWFALL WILL OCCUR TODAY. A FEW
LOCATIONS COULD GET UP TO 6 INCHES OF SNOW FROM THIS FAST-MOVING
SYSTEM. WINDS WILL TURN TO THE NORTHWEST THIS EVENING AND BECOME
GUSTY WITH SNOW SHOWERS LIKELY DOWNSTREAM OF LAKE ERIE AND IN THE
LAUREL HIGHLANDS. NEXT WEEK LOOKS QUIET WITH ONLY A COUPLE OF WEAK
WEATHER SYSTEMS PASSING BY. THE BIG STORY LATER NEXT WEEK WITH BE
THE POSSIBILITY OF VERY COLD AIR ENTERING THE STATE.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SNOW IS FALLING BASICALLY OVER ALL OF THE REGION. VERY LIGHT SNOW
REPORTED IN EASTERN LANCASTER COUNTY. HAD CALLS ABOUT WHEN WILL IT
SNOW! ADJUSTED GRIDS WITH LATEST BLENDED GUIDANCE WHICH CLIPPED
QPF AND THUS SNOWFALL IN SOUTHERN AND EASTERN AREAS. SOME AREAS IN
NORTH-CENTRAL PA SHOW 0.50 INCHES OF QPF. WITH HIGHER RATIOS A FEW
AREAS COULD TOP 6 INCHES. STILL ANTICIPATING MOST LOCATIONS WILL
STAY IN 3-6 INCH RANGE.
SATELLITE SHOWS SHARP DRY SLOT MOVING INTO SW PA. THIS FAVORS SOME
ENHANCE BANDING TO ITS NORTH AND EAST PERHAPS NORTHERN TIER IN A
FEW HOURS. WILL MONITOR ENHANCED CSI EFFECT FROM ABOUT STATE
COLLEGE NORTHWARD THIS AM AND EARLY THIS AFTERNOON. COULD PUSH UP
SNOW TOTALS A BIT TOO. BUT ECHOES ARE WEAKENING BENEATH AND JUST
AHEAD OF IT. THIS CAN BE SEEN ON RADAR IN SW PA...BUT IN ADVANCE
OF IT IS WHERE BEST CSI POTENTIAL WILL BE.
THE RAP AND HRRR SHOW SNOW PULLING OUT OF THE REGION RAPIDLY IN
THE 1 PM TO 3 PM RANGE FROM SW TO ENE. BY ABOUT 5 PM ANY
ACCUMULATING SNOW WOULD BE CONFINED TO NORTHEASTERN AREAS. MOSTLY
LIGHT SNOW AND FLURRIES AFTER 5 PM OVER MOST OF CWA. LINGERING IN
THE MOUNTAINS.
THE BAND IN VA-MD COULD CLIP SOUTHERN YORK AND LANCASTER COUNTIES
BEFORE NOON AND GET THE SNOW FALL TO INCREASE THERE. SOMETHING TO
WATCH IN EXTREME SE. THE 14Z RAP SHOWS SLIGHT ENHANCED SNOW IN
LANCASTER COUNTY AROUND 17Z.
WE HAVE ENTERED THE BEST PERIOD OF HEAVY SNOW AND WILL TRACK IN
NOWCASTS. VISIBILITIES WILL BE LOW OVER MOST OF THE REGION THROUGH
AT LEAST 1 PM AND ROADS WITH 1 TO 2 INCH RATES AT TIMES AT THEIR WORSE.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
MONITORING SNOW SHOWER AND ACCUMULATING SNOW IN SW MOUNTAINS AND
NW PA DURING THIS PERIOD. MOST OTHER AREAS TO EAST WILL SEE LITTLE
OR NOW SNOW AFTER 9 PM GIVE OR TAKE 1-3 HOURS.
PREVIOUS DISCUSSION....THE LOW DEPARTS AND
DEEPENS OFF THE EAST COAST THIS EVENING. RESIDUAL MOISTURE FROM
THE EXITING LOW...COUPLED WITH W/NW FLOW AND UPSLOPE TOPOGRAPHIC
ENHANCEMENT WILL MAKE SNOW SHOWERS ACROSS THE SNOW BELT AND IN THE
LAUREL HIGHLANDS. THESE SHOWERS SHOULD BE MAINLY LIGHT AND SHOULD
DIE DOWN SUNDAY EVENING. THOSE FAVORED/UPSLOPE LOCATIONS IN THE
LAURELS AND DOWNWIND OF THE LAKES COULD PICK UP ANOTHER INCH OR
TWO TONIGHT AND ANOTHER INCH SUNDAY MORNING BEFORE THE FLOW
BECOMES ANTICYCLONIC. THOSE VALUES SHOULD BE JUST SUB- ADVISORY
FOR THEM. BUT ALLOWING LEEWAY...THE CURRENT ADVY FOR THOSE AREAS
COULD BE EXTENDED IF NECESSARY TO COVER THE ADDITIONAL
LAKE/UPSLOPE SNOW. OTHERWISE...SUNDAY WILL BE A BREEZY BUT FAIR
DAY FOR THE REST OF THE AREA. GUSTS COULD BE INTO THE L30S IN THE
SRN MTS AND EAST...BUT NO WORRY OF WIND ADVY. MAX TEMPS ON SUNDAY
WILL BE SIMILAR TO TODAY.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
THE FLOW WILL SHIFT TO A MORE ZONAL PATTERN AS ANOTHER SYSTEM
MAKES ITS WAY TOWARD THE REGION FOR MONDAY NIGHT/NEW YEARS EVE.
THE CURRENT MODELS ARE FAIRLY CONSISTENT AND HAVE SUFFICIENT PWATS
AND LIFT FROM A JET STREAK TO CREATE SNOW SHOWERS OVER AT LEAST
THE WESTERN HALF OF THE AREA MON NIGHT AND TUES MORNING. A FEW
NORTHERN STREAM FEATURES WILL CROSS THE LOWER GREAT LAKES AROUND
MID-WEEK AND MAKE LAKE EFFECT SHOWERS. AN ARCTIC AIR MASS BEGINS
TO MOVE THROUGH SOUTHERN CANADA AND DECREASING 850MB TEMPERATURES
WILL CONTINUE THROUGH THE LATTER HALF OF THE WEEK. CURRENT RUNS
HAVE PA UNDER M16C TEMPERATURES AT 850MB FRIDAY MORNING. THE GFS
AND EC PROPAGATE ANOTHER TROUGH THROUGH PENNSYLVANIA FRIDAY.
EXPECT HIGH TEMPERATURES THIS WEEK TO BE AT OR BELOW
FREEZING...WITH HIGHS IN THE UPPER TEENS POSSIBLE BY THE END OF
NEXT WEEK. COUPLE THE LOW TEMPS WITH THE GUSTY FLOW...AND WIND
CHILLS COULD BE AN ISSUE DURING THIS TIME FRAME. LOWS THROUGH THE
LATER HALF OF THE WEEK SHOULD BE IN THE LOW TEENS.
&&
.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
BROAD SHIELD OF SNOW COVERING WRN TWO THIRDS OF CENTRAL PA AT THIS
TIME AS WEAK SFC LOW TRACKS INTO WRN PA. SNOW OF VARYING
INTENSITIES IS PRODUCING IFR CIGS AT ALL CENTRAL AND WESTERN
AIRFIELDS. IN THE EAST...MDT CURRENTLY HAS MVFR CIGS WHILE ARE IPT
AND LNS ARE ACTUALLY VFR. SNOW...ALONG WITH REDUCED CIGS AND VSBYS
SHOULD COME BACK INTO EASTERN SITE WITHIN THE NEXT HOUR.
EXPECT STEADY SNOW TO CONTINUE INTO THE AFTERNOON HOURS WITH
GENERALLY IFR/LIFR CONDS AT ALL TAF SITES FOR SEVERAL HOURS. CONDITIONS
WILL BEGIN TO IMPROVE FROM WEST TO EAST DURING THE LATE AFTERNOON.
GUSTY WINDS APPEAR LIKELY OVERNIGHT TONIGHT INTO SUNDAY WITH
SCATTERED SNOW SHOWERS DEVELOPING IN THE WESTERN AND NORTHWESTERN
MTNS. NWLRY UPSLOPE FLOW WILL LIKELY KEEP FLYING CONDS AT KJST AND
KBFD MARGINAL AFTER THE STORM WITH LOW CLOUDS AND PERIODS OF
LOWERED VISIBILITIES.
OUTLOOK...
SUN...SHSN AND REDUCED FLIGHT CONDS POSSIBLE WESTERN AND NORTHERN
MTNS.
MON...NO SIG WX EXPECTED.
TUE...CFROPA POSSIBLE. SHSN REDUCED CIGS/VI`S AND GUSTY WINDS
POSS.
WED...MAINLY VFR.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR
PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-
049>053-056>059-063>066.
&&
$$
SYNOPSIS...DANGELO/LA CORTE
NEAR TERM...GRUMM/DANGELO
SHORT TERM...GRUMM/DANGELO
LONG TERM...DANGELO/CERU
AVIATION...GRUMM/GARTNER
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
855 PM CST SUN DEC 30 2012
.DISCUSSION.../ISSUED AT 855 PM CST/
STRATUS APPROACHING NORTHERN CWA AND SHOULD SPREAD SOUTH ACROSS CWA
OVERNIGHT. SO BUMPED UP CLOUD COVER. ALSO THESE CLOUDS WILL HELP
HOLE TEMPERATURES UP AND LOWS WILL LIKELY NOT BE HIT UNTIL 15Z OR
16Z ON MONDAY. SO WILL KEEP LOWS ABOVE ZERO TONIGHT.
&&
.AVIATION.../FOR THE 00Z TAF ISSUANCE/
SURFACE COLD FRONT CONTINUES TO PUSH ACROSS THE AREA WITH WINDS
TURNING WEST AND NORTHWEST BEHIND IT....WITH SPEEDS GENERALLY AROUND
10 KTS. MVFR STRATUS IS CURRENTLY MOVING SOUTH ACROSS NORTH DAKOTA
ALONG THE 850MB FRONT. TIMING AND COVERAGE OF THIS ACROSS OUR CWA
REMAINS UNCERTAIN. RAP AND HRRR SHOW STRATUS DEVELOPING AHEAD OF THE
CURRENT AREA ACROSS NORTHEAST SOUTH DAKOTA...AND ACCELERATES THIS
SOUTH INTO OUR CWA. THUS HAVE SPED UP THE TIMING OF MVFR STRATUS
INTO THE TAF SITES. ALTHOUGH IF STRATUS DOES NOT BEGIN TO EXPAND AND
ACCELERATE...THE SLOWER TIMING IN THE EARLIER TAFS MAY STILL BE
CORRECT. ONCE THE STRATUS MOVES IN IT WILL BE SLOW TO CLEAR. DRIER
AIR WILL TRY TO ADVECT IN FROM THE NORTHWEST...BUT FLOW WILL BECOME
WEAKER AS TOMORROW PROGRESSES. THUS WILL LEAVE MVFR CLOUDS IN FOR
FSD AND SUX THROUGH THE DAY...ALTHOUGH CONFIDENCE REMAINS LOW.
ALSO...WHILE AM CURRENTLY JUST GOING MVFR...IT IS POSSIBLE THAT WE
SEE SOME IFR CIGS AT TIMES AS WELL INTO TOMORROW...SO WILL HAVE TO
MONITOR CIG HEIGHTS AS STRATUS GETS CLOSER. /CHENARD
&&
.DISCUSSION.../ISSUED AT 300 PM CST/
COLD FRONT WILL BE MOVING THROUGH THE FORECAST AREA TONIGHT BEHIND A
PRE FRONTAL WIND SHIFT WHICH IS MOVING THROUGH AT THIS TIME. MAIN
CONCERNS ARE HOW FAR TEMPERATURES WILL FALL BEHIND THE FRONT AS WELL
AS POTENTIAL FOR STRATUS. THE COLD FRONT CURRENTLY EXTENDS FROM
NORTHEAST ND TO JUST NORTH OF BISMARCK AND IS WELL DEPICTED ON THE
11-3.9 MICRON SATELLITE IMAGE. THERE IS AN ORGANIZED LAYER OF
STRATUS BEHIND IT INTO SOUTHERN CANADA...THEN IT CLEARS OUT AGAIN
NORTH OF THERE. BELIEVE THAT SOME OF THIS STRATUS WILL OOZE DOWN
BEHIND THE FRONT INTO OUR FORECAST AREA OVERNIGHT AND LATE
TONIGHT...WITH THE STRATUS THEN CLEARING THROUGH THE MORNING ON
MONDAY. THE SHORTER RANGE MODELS REALLY DO NOT BRING ANY STRATUS
DOWN INTO OUR FORECAST. HOWEVER THAT SAID...THEY ARE HAVING A
DIFFICULT TIME IN ANALYZING THE CURRENT STRATUS. EVEN IF THE LOW
CLOUDS WOULD NOT HAPPEN TO COME DOWN...THERE IS ENOUGH HIGH LEVEL
CLOUDS STREAMING NORTHEASTWARD AHEAD OF AN UPPER TROUGH IN THE
SOUTHWEST U.S...SO SKY COVER WILL LIKELY NOT BE REAL PRISTINE. IN
ADDITION...SOME MOISTURE IN THE 850-700MB LAYER MAY ALSO MOVE
SOUTHWARD WHICH IS CURRENTLY EVIDENT IN ND. TEMPERATURES A BIT
PROBLEMATIC. FOR LOWS WENT A LITTLE COOLER THAN MOST GUIDANCES...
HEDGING CLOSER TO THE MOS/MET/MAV GUIDANCES WHICH ARE THE COLDEST.
HOWEVER DUE TO A LACK OF CALM WINDS AND SOME AFOREMENTIONED CLOUD
COVER...IT IS LIKELY THAT THE BOTTOM WILL NOT FALL OUT OF TONIGHTS
TEMPERATURES.
ON MONDAY...EXPECT A VERY SLOW RISE WITH TEMPERATURES...WITH EAST
CENTRAL SD AND SOUTHWEST MN LIKELY NOT GETTING OUT OF THE SINGLE
DIGITS. AT THIS TIME IT APPEARS THAT WIND CHILLS WILL STAY MODERATED
ENOUGH TO NOT WARRANT AN ADVISORY. LASTLY CONCERNING MONDAY...SKY
COVER WILL PROBABLY STAY MOSTLY CLOUDY IN OUR SOUTHERN AND WESTERN
ZONES AHEAD OF THE UPPER TROUGH TO THE SOUTHWEST OF OUR AREA. BUT
CLOUDS SHOULD CLEAR HEADING NORTHEASTWARD FROM THERE. /MJF
HIGH PRESSURE SETTLES INTO THE REGION ON MONDAY NIGHT...WITH WINDS
DYING OFF AS THE RIDGE AXIS PASSES DIRECTLY OVERHEAD. WITH PROGGED
925 MB TEMPS RUNNING IN THE RANGE OF -8 C TO -14 C ACROSS THE
AREA...IT WILL BE A VERY COLD NIGHT...THOUGH TEMPERATURES MAY BE
HELD SOMEWHAT IN CHECK BY THE PRESENCE OF LOW AND MID CLOUDS WHICH
WILL SPREAD FROM WEST TO EAST OVER THE AREA OVERNIGHT. WITH THE
BRUNT OF THE COLDER AIRMASS BEING IN OUR EAST IN CONJUNCTION WITH A
LONGER PERIOD OF RELATIVELY CLOUD FREE SKIES DURING THEN
NIGHT...LOWS WILL GENERALLY DROP TO AROUND 10 DEGREES BELOW ZERO
FROM THE INTERSTATE 29 CORRIDOR EASTWARD. IT WILL STILL BE VERY COLD
IN THE WEST HOWEVER...WITH LOWS IN THE SINGLE DIGITS BELOW ZERO.
THE SURFACE RIDGE MOVES QUICKLY TO THE EAST ON TUESDAY...AND IN A
SOUTHERLY FLOW ON THE BACKSIDE OF THE HIGH...TEMPERATURES WILL BEGIN
TO WARM A BIT. THIS WILL YIELD AFTERNOON TEMPERATURES IN THE MID
TEENS EAST TO LOWER 20S THROUGH THE MISSOURI RIVER CORRIDOR.
MODELS IN GOOD AGREEMENT ON DROPPING AN UPPER LEVEL LOW INTO THE
NORTHERN PLAINS AND UPPER MIDWEST ON WEDNESDAY INTO WEDNESDAY
NIGHT...AS A SURFACE COLD FRONT SWINGS ACROSS THE AREA THROUGH THE
DAY. DYNAMICS WITH THE SYSTEM ARE NOT THAT IMPRESSIVE...BUT THERE
DOES APPEAR TO BE ENOUGH LIFT AND MOISTURE AROUND TO PRODUCE VERY
LIGHT SNOW MAINLY DURING THE DAY ON WEDNESDAY...TAPERING OFF IN THE
EVENING. WILL BE A RELATIVELY MILDER DAY HOWEVER WITH THE COLDER AIR
LAGGING...WITH HIGHS NEAR 20 NORTHEAST TO MID 20S ALONG THE
MISSOURI RIVER CORRIDOR. THE COLDER AIR FILTERS IN ON WEDNESDAY
NIGHT WITH SOME LINGERING FLURRIES POSSIBLE...AND TEMPERATURES WILL
BOTTOM OUT IN THE SINGLE DIGITS BY EARLY THURSDAY MORNING. THE BULK
OF THE COLDER AIR WILL BE ENTRENCHED ACROSS THE AREA ON THURSDAY
WITH HIGHS LOWER TEENS EAST TO NEAR 20 OVER SOUTH CENTRAL SOUTH
DAKOTA.
FOR THE REMAINDER OF THE WEEK AND INTO THE WEEKEND...MODELS IN
FAIRLY GOOD AGREEMENT ON OVERALL SYNOPTIC FLOW THROUGH THE
PERIOD...WITH OUR AREA IN A GENERAL NORTHWESTERLY UPPER LEVEL FLOW
WITH THE DEPARTURE OF THE ABOVE MENTIONED MIDWEEK SYSTEM. MODELS IN
LESS AGREEMENT ON THE MESOSCALE FEATURES...THOUGH THE MAJORITY OF
GUIDANCE IS SUGGESTING A MAINLY DRY PERIOD WITH A WARMING TREND
THROUGH THE END OF NEXT WEEKEND.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE.
&&
$$
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
610 PM CST SUN DEC 30 2012
.DISCUSSION.../ISSUED AT 300 PM CST/
COLD FRONT WILL BE MOVING THROUGH THE FORECAST AREA TONIGHT BEHIND A
PRE FRONTAL WIND SHIFT WHICH IS MOVING THROUGH AT THIS TIME. MAIN
CONCERNS ARE HOW FAR TEMPERATURES WILL FALL BEHIND THE FRONT AS WELL
AS POTENTIAL FOR STRATUS. THE COLD FRONT CURRENTLY EXTENDS FROM
NORTHEAST ND TO JUST NORTH OF BISMARCK AND IS WELL DEPICTED ON THE
11-3.9 MICRON SATELLITE IMAGE. THERE IS AN ORGANIZED LAYER OF
STRATUS BEHIND IT INTO SOUTHERN CANADA...THEN IT CLEARS OUT AGAIN
NORTH OF THERE. BELIEVE THAT SOME OF THIS STRATUS WILL OOZE DOWN
BEHIND THE FRONT INTO OUR FORECAST AREA OVERNIGHT AND LATE
TONIGHT...WITH THE STRATUS THEN CLEARING THROUGH THE MORNING ON
MONDAY. THE SHORTER RANGE MODELS REALLY DO NOT BRING ANY STRATUS
DOWN INTO OUR FORECAST. HOWEVER THAT SAID...THEY ARE HAVING A
DIFFICULT TIME IN ANALYZING THE CURRENT STRATUS. EVEN IF THE LOW
CLOUDS WOULD NOT HAPPEN TO COME DOWN...THERE IS ENOUGH HIGH LEVEL
CLOUDS STREAMING NORTHEASTWARD AHEAD OF AN UPPER TROUGH IN THE
SOUTHWEST U.S...SO SKY COVER WILL LIKELY NOT BE REAL PRISTINE. IN
ADDITION...SOME MOISTURE IN THE 850-700MB LAYER MAY ALSO MOVE
SOUTHWARD WHICH IS CURRENTLY EVIDENT IN ND. TEMPERATURES A BIT
PROBLEMATIC. FOR LOWS WENT A LITTLE COOLER THAN MOST GUIDANCES...
HEDGING CLOSER TO THE MOS/MET/MAV GUIDANCES WHICH ARE THE COLDEST.
HOWEVER DUE TO A LACK OF CALM WINDS AND SOME AFOREMENTIONED CLOUD
COVER...IT IS LIKELY THAT THE BOTTOM WILL NOT FALL OUT OF TONIGHTS
TEMPERATURES.
ON MONDAY...EXPECT A VERY SLOW RISE WITH TEMPERATURES...WITH EAST
CENTRAL SD AND SOUTHWEST MN LIKELY NOT GETTING OUT OF THE SINGLE
DIGITS. AT THIS TIME IT APPEARS THAT WIND CHILLS WILL STAY MODERATED
ENOUGH TO NOT WARRANT AN ADVISORY. LASTLY CONCERNING MONDAY...SKY
COVER WILL PROBABLY STAY MOSTLY CLOUDY IN OUR SOUTHERN AND WESTERN
ZONES AHEAD OF THE UPPER TROUGH TO THE SOUTHWEST OF OUR AREA. BUT
CLOUDS SHOULD CLEAR HEADING NORTHEASTWARD FROM THERE. /MJF
HIGH PRESSURE SETTLES INTO THE REGION ON MONDAY NIGHT...WITH WINDS
DYING OFF AS THE RIDGE AXIS PASSES DIRECTLY OVERHEAD. WITH PROGGED
925 MB TEMPS RUNNING IN THE RANGE OF -8 C TO -14 C ACROSS THE
AREA...IT WILL BE A VERY COLD NIGHT...THOUGH TEMPERATURES MAY BE
HELD SOMEWHAT IN CHECK BY THE PRESENCE OF LOW AND MID CLOUDS WHICH
WILL SPREAD FROM WEST TO EAST OVER THE AREA OVERNIGHT. WITH THE
BRUNT OF THE COLDER AIRMASS BEING IN OUR EAST IN CONJUNCTION WITH A
LONGER PERIOD OF RELATIVELY CLOUD FREE SKIES DURING THEN
NIGHT...LOWS WILL GENERALLY DROP TO AROUND 10 DEGREES BELOW ZERO
FROM THE INTERSTATE 29 CORRIDOR EASTWARD. IT WILL STILL BE VERY COLD
IN THE WEST HOWEVER...WITH LOWS IN THE SINGLE DIGITS BELOW ZERO.
THE SURFACE RIDGE MOVES QUICKLY TO THE EAST ON TUESDAY...AND IN A
SOUTHERLY FLOW ON THE BACKSIDE OF THE HIGH...TEMPERATURES WILL BEGIN
TO WARM A BIT. THIS WILL YIELD AFTERNOON TEMPERATURES IN THE MID
TEENS EAST TO LOWER 20S THROUGH THE MISSOURI RIVER CORRIDOR.
MODELS IN GOOD AGREEMENT ON DROPPING AN UPPER LEVEL LOW INTO THE
NORTHERN PLAINS AND UPPER MIDWEST ON WEDNESDAY INTO WEDNESDAY
NIGHT...AS A SURFACE COLD FRONT SWINGS ACROSS THE AREA THROUGH THE
DAY. DYNAMICS WITH THE SYSTEM ARE NOT THAT IMPRESSIVE...BUT THERE
DOES APPEAR TO BE ENOUGH LIFT AND MOISTURE AROUND TO PRODUCE VERY
LIGHT SNOW MAINLY DURING THE DAY ON WEDNESDAY...TAPERING OFF IN THE
EVENING. WILL BE A RELATIVELY MILDER DAY HOWEVER WITH THE COLDER AIR
LAGGING...WITH HIGHS NEAR 20 NORTHEAST TO MID 20S ALONG THE
MISSOURI RIVER CORRIDOR. THE COLDER AIR FILTERS IN ON WEDNESDAY
NIGHT WITH SOME LINGERING FLURRIES POSSIBLE...AND TEMPERATURES WILL
BOTTOM OUT IN THE SINGLE DIGITS BY EARLY THURSDAY MORNING. THE BULK
OF THE COLDER AIR WILL BE ENTRENCHED ACROSS THE AREA ON THURSDAY
WITH HIGHS LOWER TEENS EAST TO NEAR 20 OVER SOUTH CENTRAL SOUTH
DAKOTA.
FOR THE REMAINDER OF THE WEEK AND INTO THE WEEKEND...MODELS IN
FAIRLY GOOD AGREEMENT ON OVERALL SYNOPTIC FLOW THROUGH THE
PERIOD...WITH OUR AREA IN A GENERAL NORTHWESTERLY UPPER LEVEL FLOW
WITH THE DEPARTURE OF THE ABOVE MENTIONED MIDWEEK SYSTEM. MODELS IN
LESS AGREEMENT ON THE MESOSCALE FEATURES...THOUGH THE MAJORITY OF
GUIDANCE IS SUGGESTING A MAINLY DRY PERIOD WITH A WARMING TREND
THROUGH THE END OF NEXT WEEKEND.
&&
.AVIATION.../FOR THE 00Z TAF ISSUANCE/
SURFACE COLD FRONT CONTINUES TO PUSH ACROSS THE AREA WITH WINDS
TURNING WEST AND NORTHWEST BEHIND IT....WITH SPEEDS GENERALLY AROUND
10 KTS. MVFR STRATUS IS CURRENTLY MOVING SOUTH ACROSS NORTH DAKOTA
ALONG THE 850MB FRONT. TIMING AND COVERAGE OF THIS ACROSS OUR CWA
REMAINS UNCERTAIN. RAP AND HRRR SHOW STRATUS DEVELOPING AHEAD OF THE
CURRENT AREA ACROSS NORTHEAST SOUTH DAKOTA...AND ACCELERATES THIS
SOUTH INTO OUR CWA. THUS HAVE SPED UP THE TIMING OF MVFR STRATUS
INTO THE TAF SITES. ALTHOUGH IF STRATUS DOES NOT BEGIN TO EXPAND AND
ACCELERATE...THE SLOWER TIMING IN THE EARLIER TAFS MAY STILL BE
CORRECT. ONCE THE STRATUS MOVES IN IT WILL BE SLOW TO CLEAR. DRIER
AIR WILL TRY TO ADVECT IN FROM THE NORTHWEST...BUT FLOW WILL BECOME
WEAKER AS TOMORROW PROGRESSES. THUS WILL LEAVE MVFR CLOUDS IN FOR
FSD AND SUX THROUGH THE DAY...ALTHOUGH CONFIDENCE REMAINS LOW.
ALSO...WHILE AM CURRENTLY JUST GOING MVFR...IT IS POSSIBLE THAT WE
SEE SOME IFR CIGS AT TIMES AS WELL INTO TOMORROW...SO WILL HAVE TO
MONITOR CIG HEIGHTS AS STRATUS GETS CLOSER. /CHENARD
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
315 AM CST MON DEC 31 2012
.SYNOPSIS...
06Z SFC ANALYSIS HAS A WEAK LOW NORTH OF KLSE WITH A WARM FRONT
THROUGH SOUTHERN WISCONSIN. A COLD FRONT RAN FROM THE LOW TO ANOTHER
LOW IN SOUTHEAST COLORADO. THERE WAS A SUBTLE PRE-FRONTAL TROF FROM
THE LOW INTO EASTERN KANSAS. A SECONDARY ARCTIC FRONT RAN FROM
WESTERN LAKE SUPERIOR INTO SOUTH DAKOTA. DEW POINTS WERE IN THE
TEENS AND 20S ACROSS THE MIDWEST WITH 30S IN THE SOUTHERN PLAINS AND
DEEP SOUTH.
&&
.SHORT TERM...TODAY AND TONIGHT...
TIMING AND NORTHERN EXTENT OF THE SNOW ARE THE MAIN QUESTIONS.
BASED ON DATA THROUGH 06Z...THE RAP MODEL SEEMS TO HAVE A MORE
REALISTIC REPRESENTATION OF WHAT IS CURRENTLY GOING ON. PER THE RAP
MODEL...CONDENSATION PRESSURE DEFICITS BEGIN COLLAPSING ACROSS THE
FAR SOUTH RIGHT AROUND SUNRISE IN THE 850-700MB LAYER. HOWEVER...
CONDENSATION PRESSURE DEFICITS IN THE 1000-850MB LAYER DO NOT
COLLAPSE UNTIL MID MORNING. SO...WILL GO WITH THE IDEA OF SCHC/CHC
POPS ACROSS THE EXTREME SOUTH FOR THE MORNING COMMUTE WITH A BAND OF
FLURRIES IMMEDIATELY NORTH OF THERE.
BY MID TO LATE MORNING -SN WILL QUICKLY BREAK OUT ACROSS THE FAR
SOUTHERN CWFA AND EXPAND 15-30 MILES NORTHWARD DURING THE EARLY
AFTERNOON HOURS. LIKELY TO CATEGORICAL POPS LOOK REASONABLE
GENERALLY SOUTH OF A KPIA TO KTVK LINE WITH SCHC/CHC POPS UP AS FAR
NORTH AS A KOTM TO KVYS LINE.
DURING THE EARLY AFTERNOON HOURS THE RAP MODEL SHOWS A NEW BAND OF
FORCING DEVELOPING ALONG THE I-80 CORRIDOR WITH SOME MOISTURE
CONVERGENCE. FCST SOUNDINGS IN THIS AREA STILL SHOW AN APPRECIABLE
AMOUNT OF DRY AIR IN THE LOWER LEVELS SO SOME FLURRIES MAY BE
POSSIBLE.
BY LATE AFTERNOON THE FORCING BEGINS PUSHING TO THE SOUTH/EAST SO
THE SNOW SHOULD MIGRATE ABOUT 20-30 MILES TO THE SOUTH.
AS FOR AMOUNTS...THE EXTREME SOUTHERN BORDER AREA OF THE CWFA SHOULD
SEE AROUND AN INCH. A DUSTING WILL BE POSSIBLE AS FAR NORTH AS A
KOTM TO KGBG LINE.
TONIGHT...LIGHT SNOW WILL CONTINUE INTO THE EVENING HOURS BUT WILL
SLOWLY DECREASE IN COVERAGE/INTENSITY. AFTER MIDNIGHT...THE FORCING
CONTINUES TO WEAKEN AS THE SYSTEM MOVES INTO THE OHIO VALLEY SO THE
LIGHT SNOW WILL SLOWLY COME TO AN END. ANY ADDITIONAL AMOUNTS
TONIGHT WILL ONLY BE A TRACE TO A DUSTING.
08
.LONG TERM...TUESDAY THROUGH NEXT SUNDAY...
COLD AND DRY WITH WARMING TREND STARTING NEXT WEEKEND.
OVERVIEW...INITIALIZATION IS GOOD WITH MOST SOLUTIONS A BIT TOO MOIST
WITH TODAY/S SYSTEM. UPSTREAM...NO SENSIBLE WEATHER ISSUES. RUN TO
RUN CONTINUITY SUGGEST A 80/20 BLEND OF HI-RES ECMWF/GFS THERMAL
FIELDS. ADD TONIGHT/S VERIFICATION AND RECENT PERSISTENCE SUPPORT
WHEN SKIES ARE FAIR FOR SLIGHTLY HIGHER MAX/S THAN HIGHEST GUIDANCE
AND WITH LIGHT WINDS...MINS LOWER THAN COLDEST GUIDANCE.
TUESDAY THROUGH SUNDAY...MINOR CHANGES OF A DEGREE OR TWO MADE.
QUIET PATTERN...NEXT UPPER TROUGH AND MORE COLD AIR STILL SCHEDULED
TO ARRIVE LATE WEDNESDAY AND THURSDAY WITH POSSIBLE FLURRIES FOR
LATER SHIFTS. LOCAL BL TOOLS SUGGEST TEMPERATURES MAY NEED RAISING
BY A CATEGORY SATURDAY ONWARD.
NICHOLS
&&
.AVIATION...
SFC COLD FRONT MOVING THROUGH CENTRAL IA WILL PASS THROUGH THE
TERMINALS BETWEEN 08Z-14Z. GUSTY SOUTH WINDS 10-20+ KTS TO SHIFT TO
W/NW WITH FRONTAL PASSAGE. KDVN WSR-88D VWP SHOWING WINDS AT 45 KTS
AROUND 2000 FT AGL BUT OVERALL WINDS WILL BE DECREASING ALOFT IN THE
NEXT FEW HRS WITH FRONT MOVING IN AND WITH THIS ALONG WITH GUSTY SFC
WINDS HAVE OPTED TO NO LONGER MENTION LLWS MENTION WITH 06Z TAFS.
SATELLITE AND OBS SHOW LOW CLOUDS OVER PORTIONS OF DAKOTAS INTO MN
TRAILING WELL BEHIND SFC COLD FRONT. THERE IS A LOT OF UNCERTAINTY
ON THE EVOLUTION OF THESE CLOUDS AS SOME SHORT RANGE GUIDANCE
CONTINUES TO SUGGEST INCOMING SUBSIDENCE TO ERODE AS THEY APPROACH.
OVERALL... WHILE MAY SEE SOME MVFR CIGS DURING DAY ON MON... JUST
NOT CONFIDENT ON WHERE AND FOR HOW LONG... SO HAVE JUST CONTINUED
WITH SCATTERED MVFR BASES TO HINT AT POTENTIAL AND LET LATER SHIFTS
EVALUATE TRENDS. OTHER CONCERN WITH 06Z TAFS IS -SN POTENTIAL MAINLY
AT KBRL... AS STORM SYSTEM EJECTS FROM THE SOUTHERN PLAINS AND
SPREADS PCPN INTO NORTHEAST MO... WEST CENTRAL IL AND FAR SOUTHEAST
IA. FCST SOUNDINGS SHOW A LOT OF DRY AIR TO OVERCOME AT KBRL BUT
SUFFICIENT LIFT FOR A CHANCE OF PERIOD OF -SN WITH MVFR CONDITIONS
AT KBRL FROM LATE AM THROUGH EARLY PM. OTHERWISE... MAINLY JUST
FLURRIES AT KBRL WITH VSBYS AT OR ABOVE 6SM... WITH LOW PROBABILITY
OF -FZDZ.
05
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
08/NICHOLS/05
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
400 AM CST MON DEC 31 2012
.DISCUSSION...
A COLD FRONT HAS PASSED ACROSS THE FORECAST AREA THIS
MORNING...WITH BRISK NORTHWEST WINDS AND FAIRLY WIDESPREAD
STRATUS CLOUDS NOTED IN ITS WAKE. AN ATYPICAL TEMPERATURE TREND
WILL ENSUE TODAY...WITH READINGS EXPECTED TO FALL THROUGHOUT THE
MORNING...AND THEN ONLY WARM A COUPLE DEGREES OR REMAIN STEADY
THIS AFTERNOON.
ATTENTION THEN TURNS TO TONIGHT...AS NEW YEARS EVE-GOERS ARE MET
WITH VERY COLD TEMPERATURES UNDER THE MOSTLY CLEAR SKIES ATTENDANT
WITH THE SURFACE RIDGE. WHILE WIND SPEEDS ARE BORDERLINE AND
VALUES ARE MARGINAL OVER SOUTHERN MN...IT/S CLOSE ENOUGH TO
WARRANT ISSUANCE OF A WIND CHILL ADVISORY GIVEN THE SENSITIVITY
AROUND A HOLIDAY TIME PERIOD. MAX TEMPERATURES ON TUESDAY WILL RANK
WITHIN THE COLDEST 15 PERCENT OF NEW YEARS DAYS HIGHS IN MANY
LOCATIONS...WITH HIGHS ONLY EXPECTED TO RANGE BETWEEN 9 AND 15
DEGREES.
WEDNESDAY WILL BRING THE NEXT CHANCE OF MEASURABLE SNOW...ALBEIT
ONLY HALF INCH OR LOWER AMOUNTS...AS AN UPPER LOW DROPS SOUTH FROM
MANTIOBA/SASKATCHEWAN. A FAIRLY DECENT PV ACVECTION SIGNATURE AND
275K ISENTROPIC LIFT ARE NOTED ON WEDNESDAY...ESPECIALLY ACROSS
WEST CENTRAL MN WHERE HIGH CHANCE POPS HAVE BEEN MAINTAINED.
THURSDAY INTO THE WEEKEND WILL BRING MODERATING TEMPERATURES AS A
MID/UPPER RIDGE BUILDS OVER THE WESTERN HALF OF THE CONUS. HIGH
TEMPERATURES WILL WARM INTO THE 20S AND 30S FOR FRIDAY THROUGH THE
WEEKEND.
&&
.AVIATION.../00Z TAF ISSUANCE/
STRATUS BEHIND COLD FRONT IS HEALTHIEST IN WESTERN MN...AND MORE
SCATTERED FROM CENTRAL INTO NERN MN. SIGNIFICANT SURGE OF DRY AIR
CONTINUES TO MOVE THROUGH NWRN MN. LATEST RAP DOES A GOOD JOB
LATCHING ONTO THIS. BOTTOM LINE IS THAT EASTERN MN AND WESTERN
WISC WILL BE IN AND OUT OF THE STRATUS THROUGH THE NIGHT. WESTERN
MN SITES AXN/RWF ARE MORE LIKELY TO SEE PERSISTENT STRATUS FOR
MOST OF THE NIGHT BUT EVEN THOSE LOCATIONS WILL SEE SOME POCKETS
OF SCATTERED CLOUDS. MUCH DRIER AIR FROM NWRN MN SHOULD ARRIVE
10Z- 14Z FROM NORTHWEST TO SOUTHEAST...BRINGING SKC OR FEW CLOUDS.
ONLY OTHER ISSUE WILL BE GUSTY WINDS REACHING 20 KNOTS AT TIMES
BEFORE SETTLING DOWN AS SURFACE HIGH BUILDS IN LATE MONDAY
AFTERNOON.
KMSP...STRATUS IS QUITE PPATCHY AND KMSP WILL BE VARYING BETWEEN
OVC AND SCT AT TIMES THROUGH AT LEAST 11Z AND MAYBE EVEN 14Z.
SHOULD BE MOSTLY CLEAR THEREAFTER WITH INCOMING DRY AIR FROM
NORTHWEST. NW WINDS WITH SOME GUSTS NEAR 20 KTS MONDAY MORNING
WITH COLD ADVECTION.
/OUTLOOK FOR KMSP/
TUE...VFR. SW WINDS 5-10 KNOTS.
WED...MVFR CONDITIONS/-SN. SW WINDS 5-10 KNOTS BECOMING NW.
THU...VFR. NW WINDS 5-10 KNOTS BECOMING W.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WIND CHILL ADVISORY FROM 10 PM THIS EVENING TO 9 AM CST TUESDAY
FOR BLUE EARTH-BROWN-CHIPPEWA-DOUGLAS-FARIBAULT-FREEBORN-
GOODHUE-KANDIYOHI-LAC QUI PARLE-LE SUEUR-MARTIN-MCLEOD-
MEEKER-NICOLLET-POPE-REDWOOD-RENVILLE-RICE-SIBLEY-STEARNS-
STEELE-STEVENS-SWIFT-TODD-WASECA-WATONWAN-YELLOW MEDICINE.
WI...NONE.
&&
$$
LS/TDK
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
1159 PM CST SUN DEC 30 2012
.UPDATE...
UPDATED FOR AVIATION DISCUSSION BELOW.
&&
.DISCUSSION...
/ISSUED 216 PM CST SUN DEC 30 2012/
OVERVIEW...COLD TEMPERATURES EXPECTED THROUGH THE NEW YEAR WITH
GRADUAL WARMING LATE THIS WEEK. NEAR NORMAL TEMPS BY NEXT WEEKEND.
CHANCE OF LIGHT SNOW REMAINS IN THE FORECAST FOR WEDNESDAY AS
CLIPPER SYSTEM DROPS SOUTH ACROSS THE AREA.
ARCTIC FRONT IS NOW STRETCHED OUT ACROSS THE EASTERN DAKOTAS AND
DOWN INTO EASTERN NEBRASKA. STRONG SOUTHWESTERLY FLOW HAS WARMED
WESTERN IA AND EASTERN NE INTO THE 30S AND 40S. THE FLOW REMAINS
MORE SOUTHEAST HERE AND A THICK CANOPY OF CIRRUS ASSOCIATED WITH
THE JET IS SLOWING THE TEMPERATURE RISE IN MN/WI. COLD FRONT AND
WEAK SURFACE TROUGH MOVE THROUGH LATE THIS EVENING...AND COULD
PROVIDE MORE LOW CLOUDS TO FAR EASTERN MN AND WESTERN WI. THERE IS A
SMALL CHANCE FOR FLURRIES OR EVEN A LIGHT PATCHY FREEZING DRIZZLE
GIVEN THE SATURATION DOWN LOW. HOWEVER...WE`RE NOT EVEN COMPLETELY
CONFIDENT IN CLOUD COVER...LET ALONG SHAKING OUT DRIZZLE/FLURRIES.
THE ISENTROPIC SURFACES AREN`T AS QUICK TO SATURATE TONIGHT
COMPARED TO WHAT THE NAM/GFS WAS SHOWING YESTERDAY. ALSO...THE
LOWEST CONDENSATION PRESSURE DEFICITS ARE LOWEST RIGHT ALONG OR
JUST BEHIND THE ARCTIC BOUNDARY IN AN AREA OF COLD AIR ADVECTION.
TYPICALLY IF WE ARE GOING TO GET DRIZZLE...IT WOULD HAPPEN OUT
AHEAD OF THE FRONT WHERE THERE IS WARM AIR/MOISTURE ADVECTION AND
ISENTROPIC LIFT. SO...WE LEFT ANY PRECIP OUT OF THE FORECAST
TONIGHT...BUT DID INCREASE CLOUD COVER IN EASTERN MN AND WI.
THE FRONT SHOULD LEAD TO A NON DIURNAL TREND WITH THE TEMPERATURES
TOMORROW WHERE WE SHOULD COOL DURING THE DAY AND WILL LIKELY SEE
OUR HIGHS IN THE MORNING. STILL FAVORING A EC/NAM BLEND IN
TEMPERATURES ON NEW YEARS EVE...WITH THE GEM LIKELY TOO COLD AND
THE GFS LIKELY TOO WARM. THE GEM WOULD SUGGEST -15 TO -23...AND
OUR FORECAST IS MORE IN THE -8 TO -17 RANGE. THE WIND ISN`T VERY
STRONG BY THE TIME THE COLDEST TEMPS SETTLE IN AFTER 06Z ON JAN.
1...BUT APPARENT TEMPS STILL LOOK COLD ENOUGH FOR A WIND CHILL
ADVISORY MONDAY NIGHT INTO TUESDAY MORNING.
CLIPPER SYSTEM STILL ON TRACK FOR WEDNESDAY AND AGAIN RAISED POPS
10-20% ACROSS THE FORECAST AREA. WOULDN`T BE SURPRISED TO
EVENTUALLY NEED LIKELY TO CATEGORICAL POPS FOR WIDESPREAD LIGHT
SNOW. SNOW RATIOS WILL PROBABLY BE IN THE 16-19:1 RANGE GIVEN THE
COLDER TEMPS. THE 500 MB LOW DROPS ALMOST STRAIGHT SOUTH ACROSS
THE EASTERN DAKOTAS AND WESTERN MN DURING THE DAY ON
WEDNESDAY. THE 30.12Z GUIDANCE SHIFTED THE TRACK WESTWARD FROM
PREVIOUS RUNS. 700 MB LOW TRACK LOOKS GOOD FOR LIGHT SNOW ACROSS
MUCH OF THE FORECAST AREA...SO UNLESS SOMETHING CHANGES OVER THE
NEXT DAY...POPS SHOULD BE INCREASED. ALSO CARRYING ABOUT 0.5-1.0"
OF SNOW IN THE FORECAST AT THIS POINT.
&&
.AVIATION.../00Z TAF ISSUANCE/
STRATUS BEHIND COLD FRONT IS HEALTHIEST IN WESTERN MN...AND MORE
SCATTERED FROM CENTRAL INTO NERN MN. SIGNIFICANT SURGE OF DRY AIR
CONTINUES TO MOVE THROUGH NWRN MN. LATEST RAP DOES A GOOD JOB
LATCHING ONTO THIS. BOTTOM LINE IS THAT EASTERN MN AND WESTERN
WISC WILL BE IN AND OUT OF THE STRATUS THROUGH THE NIGHT. WESTERN
MN SITES AXN/RWF ARE MORE LIKELY TO SEE PERSISTENT STRATUS FOR
MOST OF THE NIGHT BUT EVEN THOSE LOCATIONS WILL SEE SOME POCKETS
OF SCATTERED CLOUDS. MUCH DRIER AIR FROM NWRN MN SHOULD ARRIVE
10Z- 14Z FROM NORTHWEST TO SOUTHEAST...BRINGING SKC OR FEW CLOUDS.
ONLY OTHER ISSUE WILL BE GUSTY WINDS REACHING 20 KNOTS AT TIMES
BEFORE SETTLING DOWN AS SURFACE HIGH BUILDS IN LATE MONDAY
AFTERNOON.
KMSP...STRATUS IS QUITE PPATCHY AND KMSP WILL BE VARYING BETWEEN
OVC AND SCT AT TIMES THROUGH AT LEAST 11Z AND MAYBE EVEN 14Z.
SHOULD BE MOSTLY CLEAR THEREAFTER WITH INCOMING DRY AIR FROM
NORTHWEST. NW WINDS WITH SOME GUSTS NEAR 20 KTS MONDAY MORNING
WITH COLD ADVECTION.
/OUTLOOK FOR KMSP/
TUE...VFR. SW WINDS 5-10 KNOTS.
WED...MVFR CONDITIONS/-SN. SW WINDS 5-10 KNOTS BECOMING NW.
THU...VFR. NW WINDS 5-10 KNOTS BECOMING W.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
CLF/TDK
AREA FORECAST DISCUSSION
NWS BISMARCK ND
143 AM CST MON DEC 31 2012
.DISCUSSION...
CLOUDS CONTINUE TO DIMINISH ASYMMETRICALLY SO CHALLENGES IN
GETTING TEMPERATURES RIGHT TONIGHT. LATEST HRRR SEEMS TO HAVE A
GOOD HANDLE ON THE CURRENT SITUATION SO LEANED IN ITS DIRECTION.
GRADUAL CLEARING AREA MOVING SOUTH ACROSS CENTRAL ND...WITH CLOUDS
PERSISTING WEST NEAR A SFC BOUNDARY. WHERE CLOUDS CLEAR
TEMPERATURES DROP SIGNIFICANTLY. ISOLD FLURRIES ACCOMPANYING THE
CLOUDS WEST AND SOUTH. ADJUSTED OVERNIGHT LOWS UP SIGNIFICANTLY
SOUTH AND LOWERED NORTH CENTRAL AND NORTHEAST THROUGH 15Z. WIND
CHILL HEADLINES ON TRACK.
&&
.AVIATION...AT 1 AM CST...SURFACE HIGH PRESSURE CONTINUED TO
BUILD INTO NORTHERN NORTH DAKOTA. THE SURFACE HIGH WILL SQUEEZE
THE MVFR TO LOCALLY IFR CONDITIONS INTO WESTERN NORTH DAKOTA
(KISN-KDIK) INTO MONDAY MORNING. MVFR BECOMING VFR AT KBIS-KJMS
LATE SUNDAY NIGHT INTO MONDAY MORNING AS THE HIGH BUILDS SOUTH.
VFR AT KMOT. THEN THE BAND OF MVFR STRATUS WILL MOVE EAST INTO
CENTRAL NORTH DAKOTA KMOT-KBIS AFTER 18-20Z.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 9 AM CST THIS MORNING FOR NDZ002>005-
010>013-022-023-025-037-048-051.
&&
$$
UPDATE...NH
AVIATION...WAA
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
307 AM CST MON DEC 31 2012
.TODAY AND TONIGHT...FORECAST CONFIDENCE IS MEDIUM.
LOW LEVEL MIXING...CONVERGENCE AND SHALLOW MOISTURE MAY YET CAUSE
STRATUS TO FORM VICINITY OF COLD FRONT PASSING THRU SRN WI EARLY
THIS MRNG. STRONG WARM AIR ADVECTION AHEAD OF THE FRONT CAUSED
TEMPS TO WARM INTO THE UPPER 20S TO LOWER 30S...WHICH WILL LIKELY
BE CLOSE TO THE DAYTIME HIGHS IN THE EASTERN AREAS. EXPECT THE
COLDER AIR TO SURGE INTO THE WEST EARLY THIS MRNG WITH MINIMAL
TEMPERATURE RECOVERY DURING THE DAY.
DIFFICULT TO IGNORE UPSTREAM SCT-BKN STRATUS FIELD OVER NORTHWEST
WI INTO MN. LOW LEVEL COLD AIR ADVECTION SETTLES INTO SRN WI TODAY
BEFORE BECOMING MORE NEUTRAL TONIGHT. LOW LEVEL CYCLONIC CURVATURE
LINGERS OVER THE AREA AS WELL...BUT ATMOSPHERE ABOVE INVERSION
REMAINS FAIRLY DRY THRU 10K FEET. BOTH NAM AND GFS SHOW LOW LEVEL
RH DECREASING TODAY...BUT THIS GUIDANCE DOES NOT APPEAR TO HAVE
GOOD HANDLE ON UPSTREAM STRATUS. LATEST HRRR ALSO BULLISH ON
MINIMAL LOW CLOUDS.
NEVER THE LESS...SRN WI WILL GET GRAZED BY PASSING HIGHER CLOUDS
FROM FORCING OCCURRING ALONG BAROCLINIC ZONE JUST TO THE SOUTH.
HENCE THINKING CLOUD CONDITIONS WILL VARY FROM PARTLY SUNNY TO
MOSTLY CLOUDY TODAY...AND WILL REMAIN MORE PESSIMISTIC AT THIS
TIME.
BUILDING SUBSIDENCE ASSOCIATED WITH APPROACHING RIDGING WILL
RESULT IN ANY STRATUS AND HIGHER CLOUDS CLEARING OVERNIGHT
TONIGHT. 925 TEMPS TUMBLE TO BETWEEN 11 AND 14 DEGREES CELSIUS
BELOW ZERO. WITH WIDESPREAD SNOW FIELD ACROSS SRN WI...EXPECT
TEMPERATURES TO FALL INTO THE SINGLE DIGITS ABOVE ZERO WITH SOME
BELOW ZERO READINGS. NORTHWEST WINDS CONTINUING AT 4 TO 10 KNOTS
WILL CAUSE WIND CHILL READINGS TO FALL TO BETWEEN 10 AND 15 BELOW
ZERO MOST AREAS LATE TONIGHT.
.TUESDAY THROUGH WEDNESDAY NIGHT...FORECAST CONFIDENCE IS MEDIUM
TO HIGH.
SHORT TERM MODELS SHOWING MODEST 500MB SHORTWAVE TROUGH SLIDING
SOUTHEAST ACROSS THE AREA TUESDAY...WITH FLOW BECOMING
SOUTHWESTERLY BY 18Z WEDNESDAY...BEFORE MORE AMPLIFIED SHORTWAVE
TROUGH SLIDES SOUTHEAST INTO THE REGION WEDNESDAY NIGHT. AT THE
SURFACE...HIGH PRESSURE RIDGE KEEPS HOLD OF THE AREA TUESDAY AND
TUESDAY NIGHT...WITH A LOW PASSING NORTH OF THE AREA WEDNESDAY
NIGHT.
SOME MOISTURE IN THE LOW LEVELS MOVES INTO THE AREA LATER TUESDAY
NIGHT INTO WEDNESDAY. MODEST UPWARD VERTICAL MOTION SEEN WEDNESDAY
NIGHT WITH SHORTWAVE...WITH AREA FORECAST SOUNDINGS SHOWING SOME
MOISTURE IN THE LOW TO MID LEVELS. GFS SHOWING BETTER MOISTURE IN
THE LOW LEVELS THAN THE NAM. SPOTTY LIGHT QPF SEEN IN THE AREA
WEDNESDAY NIGHT ON GFS/CANADIAN/ECMWF...DRY ON NAM.
WILL CONTINUE TO MENTION LOW END POPS FOR LIGHT SNOW LATE
WEDNESDAY IN THE FAR WESTERN COUNTIES...AND ACROSS THE AREA
WEDNESDAY NIGHT...WITH TUESDAY INTO WEDNESDAY MAINLY DRY. COLD
TEMPERATURES WILL LINGER THROUGH THE PERIOD...WITH 925MB
TEMPERATURES TRYING TO CLIMB INTO THE SINGLE DEGREES BELOW ZERO
CELSIUS RANGE.
.THURSDAY THROUGH SUNDAY...FORECAST CONFIDENCE IS MEDIUM.
ECMWF/GFS BOTH SHOWING SHORTWAVE TROUGH EXIT THE REGION...WITH THE
ASSOCIATED SURFACE LOW SHIFTING EAST. GFS FORECAST SOUNDINGS
SHOWING DRY AIR COLUMN DURING THIS TIME...SO KEPT DRY FORECAST
GOING. HIGH PRESSURE THEN PASSES SOUTH OF THE REGION THURSDAY
NIGHT THROUGH FRIDAY NIGHT...WITH WARM AIR ADVECTION TRYING TO
MOVE INTO THE REGION.
ECMWF/GFS THEN SHOW DIFFERENCES FOR SATURDAY THROUGH SUNDAY. THE
GFS TRIES TO BRING A 500MB SHORTWAVE TROUGH THROUGH THE REGION
SATURDAY INTO SATURDAY EVENING...ALONG WITH A COLD FRONT MOVING
SOUTHEAST THROUGH THE AREA 00Z SUNDAY. DECENT MOISTURE ON GFS
FORECAST SOUNDINGS ARE SEEN. LIGHT QPF OCCURS WITH THESE FEATURES.
ANOTHER SHORTWAVE MOVES SOUTHEAST INTO THE REGION LATER ON SUNDAY.
THE ECMWF SHOWS A 500MB SHORTWAVE TROUGH PASSING TO THE NORTHWEST
OF THE AREA SUNDAY AFTERNOON AND NIGHT...WITH MODEST NORTHWEST
FLOW ACROSS THE AREA. WEAK HIGH PRESSURE MOVES SOUTH OF THE AREA
SATURDAY AND SATURDAY NIGHT...WITH SOUTHWEST WINDS SUNDAY.
GIVEN THE DIFFERENCES...WENT WITH THE CONSENSUS POPS FOR THE
WEEKEND...WHICH KEEPS THINGS DRY. TEMPERATURES WERE HANDLED IN A
SIMILAR WAY...WHICH BRINGS MORE SEASONABLE TEMPERATURES TO THE
AREA.
&&
.AVIATION/12Z TAFS/...LOW LEVEL COLD AIR ADVECTION AND WEAK
CYCLONIC CURVATURE MAY ALLOW STRATUS TO DEVELOP OVER SRN WI TODAY
CONTINUING INTO THIS EVENING. HOWEVER QUITE A BIT OF DRY AIR
BETWEEN 2K AND 10K FEET. ALSO NEED TO WATCH UPSTREAM STRATUS FIELD
OVER SRN MN POSSIBLY ADVECTING INTO SRN WI LATER THIS MRNG AND
AFTN...BUT VERY WELL COULD MIX OUT IN DRIER AIR.
LATEST HRRR MODEL OPTIMISTIC ON VFR CONDITIONS TODAY...WHILE
LATEST NAM CONTINUES TO BRING PERIOD OF STRATUS INTO SRN WI BEHIND
CDFNT MOVING THRU NEXT FEW HOURS. HOWEVER NOT SEEING ANY INCREASE
IN STRATUS OVER CENTRAL WI. AT THIS POINT...CONFIDENCE LOW ON
TIMING AND COVERAGE OF MVFR LOW CLOUDS FOR THIS TAF PERIOD.
&&
.MARINE...WILL CONTINUE ONGOING SMALL CRAFT ADVY THROUGH 15Z THIS
MRNG. EXPECT GUSTY SOUTHWEST WINDS TO 25 KNOTS TO CONTINUE NEXT
FEW HOURS AHEAD OF CDFNT WHICH WILL BE PASSING ACROSS NEARSHORE
WATERS BETWEEN 11Z AND 14Z. WINDS WILL BECOME WEST AND THEN
NORTHWEST UPON FRONTAL PASSAGE THIS MRNG...HOWEVER LOW LEVEL COLD
AIR ADVECTION WEAK. HENCE STILL EXPECT WINDS TO MOSTLY SETTLE
BELOW SMALL CRAFT ADVISORY THRESHOLD LATER THIS MRNG. WITH COLDER
AIR SETTLING IN...WILL NEED TO WATCH FOR FREEZING SPRAY THREAT
REST OF THE WEEK.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 9 AM CST THIS MORNING FOR LMZ643>646.
&&
$$
TODAY/TONIGHT AND AVIATION/MARINE...MBK
TUESDAY THROUGH SUNDAY...WOOD
AREA FORECAST DISCUSSION...UPDATED
NWS MILWAUKEE/SULLIVAN WI
1154 AM CST SAT DEC 29 2012
.UPDATE...
A SHORTWAVE SWINGING ACROSS EASTERN MN AND IOWA INTO WESTERN WI LATE
THIS MORNING IS PRODUCING SNOW SHOWERS WITH VISIBILITIES DOWN TO 4
NM AT VARIOUS SITES. THE SHORTWAVE WILL PROGRESS EAST WITH THE UPPER
TROUGH THIS AFTERNOON. THEREFORE...INCREASED THE POPS ACROSS ALL OF
THE FORECAST AREA TO MENTION OCCASIONAL LIGHT SNOW OR SCATTERED SNOW
SHOWERS.
MEANWHILE...THE REMNANTS OF THE SYSTEM LAST NIGHT WITH THAT LAKE
ENHANCEMENT BAND THAT STALLED OVER EAST CENTRAL WISCONSIN IS MAKING
ITS WAY SOUTHWARD THROUGH KENOSHA THIS MORNING. THE SNOW SHOWERS
WILL CONTINUE TO GRADUALLY SHIFT SOUTHEAST THROUGH THE AFTERNOON AND
DIMINISH. WINDS IN THE EAST MAY SHIFT TO NORTH FOR A TIME...BUT THEN
SHIFT BACK TO THE NORTHWEST LATER THIS AFTERNOON AND TO THE WEST
TONIGHT.
A FEW FLURRIES MAY LINGER INTO THE EARLY EVENING IN SOUTHEAST WI
UNTIL THAT UPPER TROUGH COMPLETELY CLEARS THE STATE. THEN SKIES WILL
GRADUALLY SCATTER OUT OVERNIGHT AND SHOULD BECOME CLEAR SUNDAY
MORNING WITH HIGH PRESSURE MOVING IN.
&&
.AVIATION/18Z TAFS/...
THE AREA OF SNOW SHOWERS IN EASTERN WI WILL GRADUALLY DIMINISH THIS
AFTERNOON. MEANWHILE...ANOTHER AREA OF LIGHT SNOW SHOWERS WILL
SPREAD ACROSS SOUTHERN WI LATER THIS AFTERNOON. CIGS SHOULD REMAIN
IN FUEL ALTERNATE CATEGORY FOR THE DURATION. VSBYS COULD DROP TO
MVFR AT TIMES WITH SNOW THIS AFTERNOON. SNOW FLURRIES MAY LINGER IN
SOUTHEAST WI THROUGH 9 PM THIS EVENING. OTHERWISE...ALL SNOW SHOULD
END BY EARLY EVENING.
STRATUS WILL BE SLOW TO CLEAR TONIGHT...BUT EXPECT IT TO SCATTER OUT
EARLY SUNDAY MORNING AS HIGH PRESSURE MOVES IN.
&&
.PREV DISCUSSION... /ISSUED 330 AM CST SAT DEC 29 2012/
SHORT TERM...
TODAY-FORECAST CONFIDENCE MEDIUM
INVERTED SURFACE TROUGH AND LAKE ENHANCED BAND OF -SN TO
OCCASIONALLY MODERATE SN WILL AFFECT ERN CWA THIS MRNG AS THEY PIVOT
SOUTHWARD. BOTH NAM AND GFS SHOWING LOW LEVEL FN VECTOR RESPONSE TO
FRONTOGENETICAL FORCING TIED TO SURFACE TROUGH EARLY THIS MRNG IN
THE EAST WITH THESE FEATURES. HENCE ENOUGH CONFIDENCE THAT -SN WL
BE FALLING AFTER 12Z TO BUMP UP TO CATEGORICAL WORDING IN THE
EAST...WITH ADDITIONAL SNOWFALL MOSTLY LESS THAN AN INCH. EXTENDED
WINTER WX ADVY FOR SHEBOYGAN COUNTY TO 13Z TO ACCOUNT FOR LAKE
ENHANCED BAND MOVING THRU. CURRENT VSBY DOWN TO 3/4NM AT KSBM.
KMKX AND TMKE RADARS SHOWING 15 TO 20DBZ TIED TO THIS ENHANCED BAND
OVER NORTHEAST CWA. MORE IMPRESSIVE 25-30DBZ BAND HAS REMAINED
OFFSHORE OVER LAKE MI. NOT IMPOSSIBLE THIS COULD MOVE SOUTHWEST AND
AFFECT SOUTHERN OZAUKEE AND MILWAUKEE COUNTIES AROUND 12Z WHEN NAM12
SHOWS STRONG OMEGA AFFECTING THIS AREA. FORTUNATELY...LOW LEVEL
WINDS CONTINUE TO BACK THROUGH THE MORNING AND AFTERNOON...NOT
ALLOWING THE STRONG CONVERGENCE TO FOCUS ON ONE AREA FOR A PROLONGED
PERIOD OF TIME. BY 20Z...LAKE ENHANCED SNOWFALL AND SURFACE TROUGH
WILL HAVE SAGGED SOUTH OF THE AREA WITH LINGERING PATCHY -SN OR
FLURRIES IN ERN CWA.
TONIGHT-FORECAST CONFIDENCE MEDIUM
NORTHWEST WINDS IN THE LOW TO MID LEVELS WILL USHER DRIER AIR INTO
THE AREA OVERNIGHT AS SHORT WAVE RIDGING BUILDS UPSTREAM OVER THE
NORTHERN PLAINS. HOWEVER LINGERING LOW LEVEL MOISTURE AND THERMAL
TROUGH MAY RESULT IN STRATUS STICKING AROUND OR POSSIBLY
REDEVELOPING FOR A TIME OVERNIGHT...HENCE LOW CONFIDENCE ON AMOUNT
OF OVERNIGHT CLEARING AT THIS TIME.
SUNDAY-FORECAST CONFIDENCE HIGH
POLAR RIDGE OVERHEAD FIRST THING WITH A COLD START...BUT THEN
STRONG WARM ADVECTION OCCURRING DURING THE DAY. IN FACT...925 MB
TEMPS WARM TO ABOUT -2C...SUGGESTING TEMPERATURES APPROACHING 30.
SEEMS THAT MIXING WILL BE PRETTY MINIMAL WITH SNOW COVER SO MID
20S MORE LIKELY.
MONDAY-FORECAST CONFIDENCE MEDIUM
FRONT COMES THROUH FIRST THING WITH COLD ADVECTION DURING THE DAY.
925 MB TEMPS DROP FROM -4C TO -10C DURING THE DAY...IMPLYING THAT
READINGS MAY HOLD STEADY OR DROP IN THE MIDDAY AND EARLY
AFTERNOON. CONFIDENCE OVERALL WOULD BE HIGH BUT NAM HAS A SUBTLE
DIFFERENCE FROM OTHER MODELS. NAM KEEPS UPPER RIDGING STRONGER IN
EASTERN STATES AND IS A LITTLE SLOWER WITH NORTHERN BRANCH TROUGH
IN DAKOTAS...ALLOWING A STRONGER MOISTURE SURGE AHEAD OF
CONFLUENCE ZONE A TAD FARTHER NORTH THAN ALL OTHER MODELS. NAM
WOULD ALLOW A BIT OF SNOW IN THE SOUTHEAST BUT OTHER MODELS DRY
AND WILL KEEP IT DRY GIVEN THAT ECMWF AND GFS ARE USUALLY MORE
TRUSTWORTH BEYOND 36 HOURS THAN NAM.
LONG TERM...
TUESDAY-FORECAST CONFIDENCE HIGH
COLD SHOT WITH 925 MB TEMPS AROUND -14C SUGGESTS NEAR ZERO MORNING
TEMPERATURES. CIPS ANALOGS HAVE 40-50% CHANCE OF BELOW ZERO LOWS
AND ABOUT 30% CHANCE OF -20C OR COLDER WIND CHILLS. CURRENTLY WE
ARE LOOKING AT ABOUT -15C WIND CHILLS IN THE WEST SO GETTING CLOSE
TO ADVISORY LEVELS.
WEDNESDAY-FORECAST CONFIDENCE MEDIUM
MODELS HAVE A CLIPPER SYSTEM MOVING THROUGH...WITH GFS FASTER AND
FARTHER NORTH WITH GEMNH AND ECMWF SLOWER AND FARTHER SOUTH. SINCE
GFS IS TYPICALLY FASTER THIS IS NOT SURPRISING. 00Z GFSE HAD HIGH
STANDARD DEVIATION OF ABOUT 10MB OVER MN...AND A COUPLE OF MEMBERS
WITH CLIPPER TRACKING SOUTH LIKE OTHER GUIDANCE. ADDED 20-30%
CHANCE OF SNOW DURING THIS PERIOD GIVEN ECMWF TRACK AND FACT THAT
COLD AIRMASS WITH DENDRITE ZONE AROUND 850 MB WILL MAKE IT EASY TO
PRODUCE SNOW.
THURSDAY-FORECAST CONFIDENCE MEDIUM
SHOULD BE COLD NO MATTER WHAT HAPPENS WITH CLIPPER WITH 925 MB
TEMPS AROUND -15C. COULD HAVE ANOTHER BELOW ZERO NIGHT AWAY FROM
THE LAKE ESPECIALLY IF THE POLAR RIDGE BUILDS IN AS FORECAST AND
SKIES CLEAR OUT. WIND CHILLS WILL AGAIN FLIRT WITH ADVISORY LEVELS
IN -10 TO -20C RANGE.
FRIDAY-FORECAST CONFIDENCE MEDIUM
BUILDING RIDGE ALOFT AND INTRUSION OF WESTERLY LOW LEVEL FLOW AND
MODIFIED PACIFIC AIRMASS INDICATES POTENTIAL FOR MODERATION.
PROBLEM IS THAT WITH EXTENSIVE SNOW COVER STRONG INVERSION COULD
LIMIT HOW MUCH MIXING DOWN OF WARM AIR OCCURS SO IT SHOULD BE
MILDER BUT MAY NOT GET MUCH ABOVE NORMAL.
AVIATION/12Z TAFS/...
AREAS OF -SN WL KEEP VSBYS AND CIGS IN MVFR OR
LOWER CATEGORY FOR A TIME THIS MRNG IN ERN TAF SITES. AREAS OF -SN
WL DIMINISH LATER THIS MRNG AND AFTER WITH IMPROVING CIGS EXPCD
TNGT. RAP GUIDANCE HAS BEEN THE BEST IN HANDLING LOW LEVEL RH LATELY
AND KEEPS LOW CLOUDS IN THRU 00Z/30. CONFIDENCE LOW ON CLEARING
TNGT AS EXTENSIVE STRATUS SHIELD/RESIDUAL MOISTURE CAUGHT IN
VICINITY OF RIDGELINE ACROSS MN/IA...WL LIKELY WORK ITS WAY EWD
TNGT.
MARINE...EXPECT WIND DIRECTION TO VARY FROM THE NORTHWEST TO NORTH
TO NORTHEAST THIS MORNING AS SURFACE TROUGH SLIPS SOUTH ACROSS
NEARSHORE AREAS. SUSTAINED WINDS AND GUSTS ARE EXPECTED TO REMAIN
BELOW 20KTS. NEXT POTENTIAL FOR STRONGER WIND GUSTS LATER SUNDAY
NIGHT AND MONDAY AHEAD OF NEXT LOW PRESSURE SYSTEM APPROACHING
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&
$$
UPDATE...MRC
TODAY/TONIGHT AND AVIATION/MARINE...MBK
SUNDAY THROUGH FRIDAY...COLLAR
AREA FORECAST DISCUSSION
NWS PHOENIX AZ
856 AM MST MON DEC 31 2012
.SYNOPSIS...
SNOW SHOWERS TO THE EAST OF PHOENIX WILL TAPER OFF THROUGH THE
DAY...WITH ONLY MINOR ACCUMULATIONS EXPECTED IN THE HIGHEST
ELEVATIONS. VERY COLD AIR WILL SETTLE OVER THE AREA TONIGHT WITH
FREEZE WARNINGS IN PLACE ACROSS THE LOWER ARIZONA DESERTS. A GRADUAL
CLIMB BACK TOWARD NORMAL TEMPERATURES WILL BEGIN ON TUESDAY LASTING
THROUGH THE WEEKEND.
&&
.DISCUSSION...
MID MORNING SATELLITE IMAGERY REVEALS AN UPPER LOW OVER CENTRAL
ARIZONA...WITH A TROUGH AXIS STRETCHING BACK THROUGH EASTERN ARIZONA
INTO SONORA. REGIONAL RADAR IMAGERY INDICATES THAT THE VAST MAJORITY
OF THE PRECIP HAS EXITED THE FORECAST AREA AND IS NOW CONCENTRATED
IN NEW MEXICO. REPORTS IN AND AROUND GLOBE INDICATE THAT ROUGHLY AN
INCH OF SNOW HAS FALLEN SINCE LAST NIGHT AROUND 4000FT...WITH HIGHER
AMOUNTS LIKELY ABOVE THAT. MEANWHILE ACROSS THE LOWER
DESERTS...PRECIP AMOUNTS APPEAR TO BE CONFINED TO AREAS EAST OF
INTERSTATE 17 FOR THE MOST PART /THERE ARE A FEW REPORTS OF A
HUNDREDTH OR TWO IN THE WEST VALLEY/. MOST NUMBERS IN THE EAST
VALLEY ARE BETWEEN A TENTH AND A QUARTER OF AN INCH. PRECIP HAS LONG
SINCE ENDED THOUGH WITH SUNNY SKIES AND COOL TEMPERATURES
PREVAILING.
IN THE VERY SHORT TERM...THE 12Z NAM AND 14Z RAP MODELS INDICATE
THAT ALL THE STRONGEST UVV HAS EXITED THE AREA...WITH ONLY WEAK
ASCENT NOTED IN THE 850-500MB LAYER. VERTICAL MOTION THROUGH THE
DENDRITIC GROWTH REGION IS VERY WEAK AND WILL ONLY CONTINUE TO
DIMINISH AS THE REST OF THE MORNING GOES ON. WHILE THE UPPER LEVEL
COLD POOL WILL REMAIN IN PLACE FOR THE REST OF THE MORNING...A LOOP
OF WV IMAGERY INDICATES IT SHOULD BEGIN EXITING THE AREA SHORTLY. HI
RES WRF MODELS ONLY SHOW A FEW INSTABILITY SHOWERS DEVELOPING NORTH
AND EAST OF PHOENIX WITH THE REST OF THE AREA REMAINING DRY. I WILL
DISCONTINUE THE WINTER WEATHER ADVISORY A FEW HOURS EARLY AS THE
OVERALL TREND WILL BE ONE OF IMPROVING CONDITIONS.
WILL ONLY MAKE MINOR ADJUSTMENTS TO THE TEMPS/CLOUD COVER FORECAST
FOR TODAY BASED ON OBSERVATIONAL TRENDS THROUGH MID MORNING.
CERTAINLY WILL BE A CHILLY END TO THE YEAR WITH TEMPS ABOUT 10-15
DEGREES BELOW NORMAL.
&&
.PREVIOUS DISCUSSION...
WITH COLDER AIRMASS ALOFT...DAYTIME TEMPS TODAY EXPECTED ON THE
ORDER OF 8 TO 12 DEGREES BELOW LATE DECEMBER NORMALS. OVERNIGHT IN
THE WAKE OF TROUGH MOSTLY CALM WINDS...STILL COLD AIRMASS ALOFT AND
CLEARING SKIES WILL SUPPORT FREEZING TEMPERATURES FOR THE DESERTS
ACROSS LA PAZ...YUMA...MARICOPA AND PINAL COUNTIES. AS SUCH...THE
PREVIOUSLY ISSUED FREEZE WATCH HAS BEEN UPGRADED TO A FREEZE WARNING
FOR TUESDAY MORNING.
EARLIER FORECAST MODEL RUNS SHOWED A SECONDARY DRY WEATHER SYSTEM
SKIRTING THROUGH THE REGION FROM THE GREAT BASIN STATES TUESDAY
AFTN. LATEST RUNS NOW DROP THIS SYSTEM WELL TO OUR SOUTH MOVING IT
ACROSS NORTHERN MEXICO FOR WEDNESDAY. OUTSIDE OF INCREASED NORTHERLY
BREEZES ALONG THE COLORADO RIVER VALLEY AND ANOTHER SHOT OF COOLER
AIR...THIS SYSTEM WILL HAVE LITTLE IMPACT TO THE FORECAST AREA.
WEDNESDAY MORNING COULD HAVE ANOTHER COOL START AS SKIES ONCE AGAIN
WILL CLEAR ACROSS THE REGION. HOWEVER...EASTERLY BREEZES OVERNIGHT
IN RESPONSE TO THE TROUGHING DRAPING ACROSS THE DIVIDE AND INTO
EASTERN ARIZONA MAY AIDE IN KEEPING THE LOWER DESERTS MIXED
OVERNIGHT. STILL CONFIDENT THAT TUESDAY AM WILL BE THE COLDEST...BUT
COULD SEE COOL ENOUGH TEMPS TO POSSIBLY WARRANT A SPECIAL WEATHER
STATEMENT FOR NEAR FREEZING TEMPERATURES WEDNESDAY AM...STAY TUNED.
FOR THE EXTENDED PERIOD...LONGWAVE TROUGHING ACROSS THE SOUTHERN
U.S. WILL LINGER INTO EAST CENTRAL ARIZONA WHILE UPPER LEVEL RIDGING
BEGINS TO AMPLIFY OVER THE WEST COAST. TEMPERATURES WILL SEE A SLOW
WARMING TREND THROUGH MIDWEEK AS HEIGHTS BEGIN TO ELEVATE ALOFT AND
CONDITIONS WILL REMAIN DRY. FORECAST SPREAD GREATLY INCREASES BEYOND
SATURDAY...AS THE EURO/GEM SOLNS BEGIN TO FAVOR THE BREAKDOWN OF THE
RIDGE AND A CUTOFF FEATURE DROPPING OUT OF THE PAC NW DOWN THE WEST
COAST FOR EARLY NEXT WEEK. THE GFS LAGS BEHIND WITH A SLOWER MOVING
CUTOFF FEATURE CIRCULATING NEAR 130W 30N FOR NEXT MONDAY. BLENDED IN
SOME OF THE CLIMO POP GRID INFLU FOR SATURDAY AND BEYOND...OTHERWISE
HELD OFF ON ADDITIONAL GRID CHANGES.
&&
.AVIATION...
SOUTH CENTRAL ARIZONA INCLUDING KPHX...KIWA...KSDL...
THROUGH 15Z MON...BKN 3-5 THSD AGL...ISOLD RAIN SHWR. LIGHT WIND.
FROM 15Z MON TO 20Z MON...SCT 5 THSD AGL...SCT-BKN 100 AGL. LIGHT
WIND. FRM 20Z MON TO 03Z TUE...SCT 6 THSD AGL. LIGHT WIND.
SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH...
THROUGH 03Z TUE...GENERALLY CLEAR SKIES. NORTH WIND 5 TO 10 KNOTS.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
A DRY COLD AIRMASS WILL CONTINUE TO COVER THE REGION THROUGH
THURSDAY. NORTHEAST BREEZES...SOMETIMES GUSTY...IN THE 10 TO 20 MPH
RANGE CAN BE EXPECTED WEDNESDAY. MINIMUM RH VALUES IN THE 15 TO 20
PERCENT RANGE WILL CONTINUE. THURSDAY THROUGH SUNDAY...DRY
CONDITIONS WITH WARMER TEMPERATURES WILL DEVELOP. LIGHT WIND.
MINIMUM RH VALUES WILL CONTINUE IN THE 15 TO 20 PERCENT RANGE.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...FREEZE WATCH FROM LATE MONDAY NIGHT THROUGH TUESDAY MORNING
AZZ021>023-026>028.
CA...NONE.
&&
$$
VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX
DISCUSSION...LEINS/NOLTE
AVIATION...VASQUEZ
FIRE WEATHER...VASQUEZ
AREA FORECAST DISCUSSION
NWS PHOENIX AZ
352 AM MST MON DEC 31 2012
.SYNOPSIS...
LIGHT MOUNTAIN SNOW SHOWERS WILL CONTINUE FOR THE HIGHER TERRAIN
EAST OF PHOENIX THROUGH THE MORNING HOURS WITH LIGHTER MORE ISOLATED
RAIN SHOWERS LINGERING ACROSS CENTRAL ARIZONA. LIGHT INSTABILITY
SHOWERS ARE POSSIBLE THIS AFTERNOON ACROSS THE CENTRAL ARIZONA
DESERTS WITH DAYTIME TEMPERATURES EXPECTED WELL BELOW NORMAL. COOL
DAYTIME TEMPERATURES COMBINED WITH COLD AIR ALOFT WILL SUPPORT
FREEZING TEMPERATURES TUESDAY MORNING EAST OF THE COLORADO RIVER
INTO CENTRAL ARIZONA. TEMPERATURES WILL BEGIN A SLOW WARM UP
TUESDAY...LASTING THROUGH THE END OF THE WEEK WITH DRY CONDITIONS
EXPECTED AS WELL.
&&
.DISCUSSION...
SCATTERED LIGHT SHOWER ACTIVITY CONTINUES ACROSS PHOENIX AND EAST
TOWARDS THE HIGHER TERRAIN AS THE UPPER TROUGH AND COLD FRONT
CONTINUE TO MOVE THROUGH ARIZONA THIS MORNING. OUT WEST ACROSS SE CA
THE SHOWER ACTIVITY HAS ENDED WITH ONLY ISOLATED PATCHES OF STRATOCU
LINGERING. HRRR AND LOCAL WRF MODELS STILL HANDLING PRECIP
PLACEMENT/TIMING THE BEST THIS AM...WITH WIDESPREAD SHOWER ACTIVITY
CURRENTLY EXPANDING ACROSS SOUTHERN ARIZONA FROM CENTRAL PINAL
COUNTY...THROUGH TUCSON...NOGALES AND POINTS EAST. SAMPLING 3AM
TEMPS/DEWPOINTS AROUND THE AREA...SNOW LEVELS ESTIMATED BETWEEN 3500
AND 4000 FEET. ADDITIONAL POCKETS OF VORT ENERGY WILL MOVE THROUGH
THE REGION AROUND THE TROUGH BASE...CONTINUING LIGHT PRECIP ACTIVITY
ESPECIALLY FOR THE UPSLOPE AREAS EAST OF PHOENIX THROUGH MIDDAY.
WILL CONTINUE THE WINTER WEATHER ADVISORY FOR AREAS ABOVE 4000FT IN
ZONE 24...SOUTHERN GILA COUNTY...THROUGH THE MORNING AS ADDITIONAL
LIGHT SNOW ACCUMULATIONS ARE POSSIBLE.
LAST DAY OF 2012 INTO NEW YEARS EVE...EXPECT A GRADUAL CLEARING OF
SKIES FROM THE WEST WITH SLIGHT CHANCES FOR AFTN INSTABILITY SHOWERS
TO FILL IN ACROSS PORTIONS OF THE CENTRAL AZ DESERTS. WITH COLDER
AIRMASS ALOFT...DAYTIME TEMPS TODAY EXPECTED ON THE ORDER OF 8 TO 12
DEGREES BELOW LATE DECEMBER NORMALS. OVERNIGHT IN THE WAKE OF TROUGH
MOSTLY CALM WINDS...STILL COLD AIRMASS ALOFT AND CLEARING SKIES WILL
SUPPORT FREEZING TEMPERATURES FOR THE DESERTS ACROSS LA
PAZ...YUMA...MARICOPA AND PINAL COUNTIES. AS SUCH...THE PREVIOUSLY
ISSUED FREEZE WATCH HAS BEEN UPGRADED TO A FREEZE WARNING FOR
TUESDAY MORNING.
EARLIER FORECAST MODEL RUNS SHOWED A SECONDARY DRY WEATHER SYSTEM
SKIRTING THROUGH THE REGION FROM THE GREAT BASIN STATES TUESDAY
AFTN. LATEST RUNS NOW DROP THIS SYSTEM WELL TO OUR SOUTH MOVING IT
ACROSS NORTHERN MEXICO FOR WEDNESDAY. OUTSIDE OF INCREASED NORTHERLY
BREEZES ALONG THE COLORADO RIVER VALLEY AND ANOTHER SHOT OF COOLER
AIR..THIS SYSTEM WILL HAVE LITTLE IMPACT TO THE FORECAST AREA.
WEDNESDAY MORNING COULD HAVE ANOTHER COOL START AS SKIES ONCE AGAIN
WILL CLEAR ACROSS THE REGION. HOWEVER...EASTERLY BREEZES OVERNIGHT
IN RESPONSE TO THE TROUGHING DRAPING ACROSS THE DIVIDE AND INTO
EASTERN ARIZONA MAY AIDE IN KEEPING THE LOWER DESERTS MIXED
OVERNIGHT. STILL CONFIDENT THAT TUESDAY AM WILL BE THE COLDEST...BUT
COULD SEE COOL ENOUGH TEMPS TO POSSIBLY WARRANT A SPECIAL WEATHER
STATEMENT FOR NEAR FREEZING TEMPERATURES WEDNESDAY AM...STAY TUNED.
FOR THE EXTENDED PERIOD...LONGWAVE TROUGHING ACROSS THE SOUTHERN
U.S. WILL LINGER INTO EAST CENTRAL ARIZONA WHILE UPPER LEVEL RIDGING
BEGINS TO AMPLIFY OVER THE WEST COAST. TEMPERATURES WILL SEE A SLOW
WARMING TREND THROUGH MIDWEEK AS HEIGHTS BEGIN TO ELEVATE ALOFT AND
CONDITIONS WILL REMAIN DRY. FORECAST SPREAD GREATLY INCREASES BEYOND
SATURDAY...AS THE EURO/GEM SOLNS BEGIN TO FAVOR THE BREAKDOWN OF THE
RIDGE AND A CUTOFF FEATURE DROPPING OUT OF THE PAC NW DOWN THE WEST
COAST FOR EARLY NEXT WEEK. THE GFS LAGS BEHIND WITH A SLOWER MOVING
CUTOFF FEATURE CIRCULATING NEAR 130W 30N FOR NEXT MONDAY. BLENDED IN
SOME OF THE CLIMO POP GRID INFLU FOR SATURDAY AND BEYOND...OTHERWISE
HELD OFF ON ADDITIONAL GRID CHANGES.
&&
.AVIATION...
SOUTH CENTRAL ARIZONA INCLUDING KPHX...KIWA...KSDL...
THROUGH 15Z MON...BKN 3-5 THSD AGL...ISOLD RAIN SHWR. LIGHT WIND.
FROM 15Z MON TO 20Z MON...SCT 5 THSD AGL...SCT-BKN 100 AGL. LIGHT
WIND. FRM 20Z MON TO 03Z TUE...SCT 6 THSD AGL. LIGHT WIND.
SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH...
THROUGH 03Z TUE...GENERALLY CLEAR SKIES. NORTH WIND 5 TO 10 KNOTS.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
A DRY COLD AIRMASS WILL CONTINUE TO COVER THE REGION THROUGH
THURSDAY. NORTHEAST BREEZES...SOMETIMES GUSTY...IN THE 10 TO 20 MPH
RANGE CAN BE EXPECTED WEDNESDAY. MINIMUM RH VALUES IN THE 15 TO 20
PERCENT RANGE WILL CONTINUE. THURSDAY THROUGH SUNDAY...DRY
CONDITIONS WITH WARMER TEMPERATURES WILL DEVELOP. LIGHT WIND.
MINIMUM RH VALUES WILL CONTINUE IN THE 15 TO 20 PERCENT RANGE.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...FREEZE WATCH FROM LATE MONDAY NIGHT THROUGH TUESDAY MORNING
AZZ021>023-026>028.
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON MST
MONDAY ABOVE 4000 FEET FOR AZZ024.
CA...NONE.
&&
$$
VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX
DISCUSSION...NOLTE
AVIATION...VASQUEZ
FIRE WEATHER...VASQUEZ
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
543 AM CST MON DEC 31 2012
.UPDATE...
RECENT RAP TRENDS GENERALLY INDICATE THE EARLIER THINKING IS ON
TRACK. THERE IS A PRE-FRONTAL TROF IMMEDIATELY AHEAD OF THE COLD
FRONT WITH THE TROF ALONG THE MISSISSIPPI RIVER. CURRENT RADAR
RETURNS ARE MID LEVEL CLOUDS BEING PICKED UP.
A MINOR FRESHENING OF THE FCST WILL BE DONE SHORTLY TO BETTER
REFLECT THE FRONTAL PLACEMENT AND RECENT TEMPERATURE TRENDS.
TEMPERATURES TODAY SHOULD BE STEADY OVER MOST OF THE CWFA WITH A
STEADY OR SLOW FALL ACROSS THE SOUTHEAST THIRD TO 40 PERCENT OF
THE CWFA. ..08..
&&
.AVIATION...
THE FRONT HAS GONE THROUGH KCID AND IS CURRENTLY GOING THROUGH
KDBQ. A SUBTLE PRE-FRONTAL TROF IS IMMEDIATELY AHEAD OF THE FRONT
BUT BOTH WILL BE GOING THROUGH KMLI/KBRL BY 14Z/31. KCID/KDBQ
CONTINUE TO HAVE A SCATTERED 1-2KFT AGL LAYER IN THE 12Z TAFS. IF
THE RAP MODEL TRENDS ARE CORRECT...THERE MAY BE A THREAT OF MVFR
OR IFR CIGS AT KDBQ AROUND 18Z/31. KBRL WILL BE IMPACTED BY THE
STORM MOVING INTO THE OHIO VALLEY WITH MVFR CONDITIONS DVLPG WITH
A POTENTIAL FOR A PERIOD OF IFR CONDITIONS AFT 18Z/31. ..08..
&&
.PREV DISCUSSION... /ISSUED 315 AM CST MON DEC 31 2012/
SYNOPSIS...
06Z SFC ANALYSIS HAS A WEAK LOW NORTH OF KLSE WITH A WARM FRONT
THROUGH SOUTHERN WISCONSIN. A COLD FRONT RAN FROM THE LOW TO ANOTHER
LOW IN SOUTHEAST COLORADO. THERE WAS A SUBTLE PRE-FRONTAL TROF FROM
THE LOW INTO EASTERN KANSAS. A SECONDARY ARCTIC FRONT RAN FROM
WESTERN LAKE SUPERIOR INTO SOUTH DAKOTA. DEW POINTS WERE IN THE
TEENS AND 20S ACROSS THE MIDWEST WITH 30S IN THE SOUTHERN PLAINS AND
DEEP SOUTH.
SHORT TERM...TODAY AND TONIGHT...
TIMING AND NORTHERN EXTENT OF THE SNOW ARE THE MAIN QUESTIONS.
BASED ON DATA THROUGH 06Z...THE RAP MODEL SEEMS TO HAVE A MORE
REALISTIC REPRESENTATION OF WHAT IS CURRENTLY GOING ON. PER THE RAP
MODEL...CONDENSATION PRESSURE DEFICITS BEGIN COLLAPSING ACROSS THE
FAR SOUTH RIGHT AROUND SUNRISE IN THE 850-700MB LAYER. HOWEVER...
CONDENSATION PRESSURE DEFICITS IN THE 1000-850MB LAYER DO NOT
COLLAPSE UNTIL MID MORNING. SO...WILL GO WITH THE IDEA OF SCHC/CHC
POPS ACROSS THE EXTREME SOUTH FOR THE MORNING COMMUTE WITH A BAND OF
FLURRIES IMMEDIATELY NORTH OF THERE.
BY MID TO LATE MORNING -SN WILL QUICKLY BREAK OUT ACROSS THE FAR
SOUTHERN CWFA AND EXPAND 15-30 MILES NORTHWARD DURING THE EARLY
AFTERNOON HOURS. LIKELY TO CATEGORICAL POPS LOOK REASONABLE
GENERALLY SOUTH OF A KPIA TO KTVK LINE WITH SCHC/CHC POPS UP AS FAR
NORTH AS A KOTM TO KVYS LINE.
DURING THE EARLY AFTERNOON HOURS THE RAP MODEL SHOWS A NEW BAND OF
FORCING DEVELOPING ALONG THE I-80 CORRIDOR WITH SOME MOISTURE
CONVERGENCE. FCST SOUNDINGS IN THIS AREA STILL SHOW AN APPRECIABLE
AMOUNT OF DRY AIR IN THE LOWER LEVELS SO SOME FLURRIES MAY BE
POSSIBLE.
BY LATE AFTERNOON THE FORCING BEGINS PUSHING TO THE SOUTH/EAST SO
THE SNOW SHOULD MIGRATE ABOUT 20-30 MILES TO THE SOUTH.
AS FOR AMOUNTS...THE EXTREME SOUTHERN BORDER AREA OF THE CWFA SHOULD
SEE AROUND AN INCH. A DUSTING WILL BE POSSIBLE AS FAR NORTH AS A
KOTM TO KGBG LINE.
TONIGHT...LIGHT SNOW WILL CONTINUE INTO THE EVENING HOURS BUT WILL
SLOWLY DECREASE IN COVERAGE/INTENSITY. AFTER MIDNIGHT...THE FORCING
CONTINUES TO WEAKEN AS THE SYSTEM MOVES INTO THE OHIO VALLEY SO THE
LIGHT SNOW WILL SLOWLY COME TO AN END. ANY ADDITIONAL AMOUNTS
TONIGHT WILL ONLY BE A TRACE TO A DUSTING.
08
LONG TERM...TUESDAY THROUGH NEXT SUNDAY...
COLD AND DRY WITH WARMING TREND STARTING NEXT WEEKEND.
OVERVIEW...INITIALIZATION IS GOOD WITH MOST SOLUTIONS A BIT TOO MOIST
WITH TODAY/S SYSTEM. UPSTREAM...NO SENSIBLE WEATHER ISSUES. RUN TO
RUN CONTINUITY SUGGEST A 80/20 BLEND OF HI-RES ECMWF/GFS THERMAL
FIELDS. ADD TONIGHT/S VERIFICATION AND RECENT PERSISTENCE SUPPORT
WHEN SKIES ARE FAIR FOR SLIGHTLY HIGHER MAX/S THAN HIGHEST GUIDANCE
AND WITH LIGHT WINDS...MINS LOWER THAN COLDEST GUIDANCE.
TUESDAY THROUGH SUNDAY...MINOR CHANGES OF A DEGREE OR TWO MADE.
QUIET PATTERN...NEXT UPPER TROUGH AND MORE COLD AIR STILL SCHEDULED
TO ARRIVE LATE WEDNESDAY AND THURSDAY WITH POSSIBLE FLURRIES FOR
LATER SHIFTS. LOCAL BL TOOLS SUGGEST TEMPERATURES MAY NEED RAISING
BY A CATEGORY SATURDAY ONWARD.
NICHOLS
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NWS RAPID CITY SD
431 AM MST MON DEC 31 2012
.AVIATION...12Z TAFS
AN AREA OF STRATUS WITH MVFR/IFR CIGS WILL CONTINUE TO ADVECT
ACROSS PARTS OF WESTERN AND CENTRAL SOUTH DAKOTA. CONDITIONS ON
THE WHOLE WILL IMPROVE THROUGH THIS AFTERNOON. PESKY STATUS IN
THE LEE OF THE BH REMAINS ERODED INVOF KRAP BY BH DOWNSLOPING.
RETAINED SCT IFR CIGS THERE FOR NOW UNTIL A BETTER HANDLE ON
DOWNSLOPE TRENDS ARE ESTABLISHED. LATEST RAP AND NAM GUIDANCE
SUGGEST A POSSIBLE INFLUX OF LOWER CIGS LATER THIS MORNING AND
INTO THE AFTERNOON WITH A DEEPENING SE WIND. HOWEVER...DIURNAL
HEATING AND CONTINUED WESTERLY FLOW AT H7 AND ABOVE SUGGEST VFR
CONDITIONS MAY PREVAIL. WILL MONITOR ATTM.
&&
.PREV DISCUSSION... /ISSUED 311 AM MST MON DEC 31 2012/
DISCUSSION...CURRENT SURFACE ANALYSIS SHOWS LOW PRESSURE OVER
SOUTHWESTERN ONTARIO...WITH A COLD FRONT STRETCHING ACROSS
MN...NORTHERN SD...AND INTO EASTERN MT. HIGH PRESSURE IS LOCATED
TO THE NORTH OVER THE CANADIAN PRAIRIE PROVS. LOW PRESSURE IS ALSO
DEVELOPING TO THE SOUTH OF THE REGION ACROSS THE SOUTHERN ROCKIES.
UPPER LEVEL ANALYSIS CONTINUES TO SHOW LOW OVER THE HUDSON BAY
REGION...WITH NORTHWESTERLY FLOW OVER OUR REGION. TROF OVER THE
SOUTHWESTERN CONUS IS NOW MOVING EASTWARD INTO THE SOUTHERN
ROCKIES AND PLAINS. SAT PICS ARE SHOWING EXTENSIVE AREA OF STRATUS
STRETCHING FROM EASTERN MT INTO MUCH OF THE DAKOTAS. THE COVERAGE
OF THE STRATUS IS MORE SPOTTY OVER WESTERN SD...BUT WILL LIKELY
FILL IN A BIT MORE EARLY THIS MORNING AND LINGER THROUGH A GOOD
PORTION OF THE DAY...ESPECIALLY FOR AREAS EAST OF THE BLACK HILLS
INTO CENTRAL SD. TEMPS CURRENTLY RANGE FROM THE SINGLE DIGITS AND
LOWER TEENS OVER MOSTLY CLEAR AREAS...TO THE TEENS AND LOWER 20S
WHERE CLOUD COVER IS IN PLACE. WINDS ARE LIGHT AND VARIABLE OVER
MOST OF THE AREA.
A SOMEWHAT UNSETTLED AND CONTINUED COLD PATTERN CAN BE EXPECTED
THROUGH WEDNESDAY AS A SERIES OF UPPER LEVEL DISTURBANCES PASS
THROUGH THE AREA IN NORTHWESTERLY FLOW. MOISTURE WITH THESE
SYSTEMS WILL BE RATHER LIMITED...BUT IT IS LOOKING LIKE SOME LIGHT
ACCUMULATIONS OF SNOW WILL BE LIKELY ACROSS PORTIONS OF THE AREA
TUESDAY NIGHT AND WEDNESDAY...ESPECIALLY NORTHEASTERN WY AND THE
NORTHERN BLACK HILLS.
FOR TODAY...AREAS OF LOW CLOUDS WILL PERSIST ACROSS THE AREA...
MAINLY TO THE NORTH AND EAST OF THE BLACK HILLS. COVERAGE SHOULD
DISSIPATE SOME BY THE MIDDAY AND AFTERNOON HOURS. WILL ALSO
INCLUDE A FEW FLURRIES IN THE FORECAST FOR NORTHWESTERN SD INTO
POSSIBLY FAR NORTHEASTERN WY. TEMPS WILL BE ON THE COLD SIDE AS
FRONT SKIRTS THE AREA. HIGHS WILL BE IN THE MID TEENS TO MID
20S...COLDEST OVER NORTHEASTERN PORTIONS OF THE CWA. ANOTHER
DISTURBANCE WILL SLIDE SOUTHWARD FROM CANADA THIS AFTERNOON AND
TONIGHT. MOISTURE WILL AGAIN BE VERY LIMITED WITH THIS WAVE...BUT
WILL GO AHEAD AND ADD SOME FLURRIES TO THE FORECAST FOR TONIGHT...
MAINLY FOR THE HIGHER ELEVATIONS OF NORTHEASTERN WY AND THE BLACK
HILLS.
NEW YEARS DAY WILL START OFF WITH SOME SUNSHINE...THEN INCREASING
CLOUDS IN THE AFTERNOON FROM THE NORTH AS THE NEXT WAVE
APPROACHES. THIS ONE LOOKS LIKE IT WILL HAVE MORE MOISTURE TO
WORK WITH AS IT SLIDES THROUGH TUESDAY NIGHT. THE BETTER MOISTURE
AND LIFT WILL PASS THROUGH NORTHEASTERN WY AND FAR WESTERN SD WITH
THIS WAVE. HAVE RAISED POPS OVER WESTERN PORTIONS OF THE
CWA...WITH LIKELY POPS OVER NORTHEASTERN WY AND THE NORTHERN BLACK
HILLS AREA. COULD SEE AN INCH OR TWO OF SNOW ACROSS PORTIONS OF
NORTHEASTERN WY AND THE NORTHERN HILLS OVERNIGHT. HIGHS ON TUESDAY
WILL BE IN THE 20S...WITH LOWS TUESDAY NIGHT IN THE SINGLE DIGITS
AND TEENS.
AS THIS WAVE PASSES SOUTH BY EARLY WEDNESDAY...ANOTHER ONE WILL
SLIDE SOUTH THROUGH THE NORTHERN PLAINS WEDNESDAY INTO WEDNESDAY
NIGHT. ASSOCIATED COLD FRONT WILL ALSO PASS THROUGH THE AREA
WEDNESDAY MORNING. MODELS DIFFER SOME ON THE TRACK AND STRENGTH OF
THIS ONE...BUT THE BRUNT OF IT WILL PASS EAST OF THE FORECAST
AREA. THERE WILL STILL BE ENOUGH LIFT AND MOISTURE TO THE WEST OF
IT TO BRING SNOW SHOWERS. WINDS WILL BE RATHER GUSTY BY LATE
WEDNESDAY MORNING ACROSS THE SD PLAINS AS FRONT PASSES AND
PRESSURE GRADIENT TIGHTENS. WILL LIKELY SEE SOME BLOWING SNOW
WHERE SNOW DOES FALL. THIS SYSTEM COULD BRING AN INCH OR SO OF
SNOW TO SOME AREAS AS IT PASSES...MAINLY OVER WESTERN SD. UPSLOPE
ENHANCED SNOWFALL OVER THE NORTHERN HILLS COULD BRING A FEW INCHES
TO FAVORED AREAS. HIGHS WILL GENERALLY BE IN THE 20S.
EXTENDED...A TRANSITION TO WARMER NW PAC ORIGIN FLOW WILL OCCUR IN
THE LONG TERM PERIOD AS A MASSIVE WESTERN NOAM RIDGE
ADVECTS/PROPAGATES EAST IN THE PERIOD. THE MAIN FOCUS IN THE PERIOD
WILL BE AN EXPANDING EAST ASIAN UPPER JET THAT WILL SUPPORT AN
EASTWARD SHIFT OF LOWER HEIGHTS...AND DOWNSTREAM ANTECEDENT RIDGING.
FORECAST MODELS REMAIN WARM PER A PAC DOWNSLOPE MODIFIED AIRMASS
EXPECTED INTO THE REGION BY LATER THUR AT THE EARLIEST. BOTH THE GEM
AND THE GFS PROG H85 T/S IN THE 5-8 C RANGE...WHICH IF MIXED WOULD
SUPPORT HIGHS WELL INTO THE 40S /AND POSSIBLY LOWER 50S IN THE LEE
OF THE BH/...ESP IF TIMING OF THE THERMAL RIDGE LINES UP WITH
DAYTIME HEATING. EVEN GIVEN THE RUN TO RUN CONTINUITY...STILL DID
NOT JUMP ON A SOLUTION THAT WARM THIS FAR OUT /ESP GIVEN CONCERNS ON
SNOW PACK/...BUT CONTINUE TO BIAS TEMPS UP IN THE FRI-SUN
PERIOD...ESP OVER THE HIGHER TERRAIN. ONE KEY AND NOTICEABLE
DIFFERENCE AMONG FORECAST MODELS IS THE HANDLING OF A NW CONUS
CLOSED UPPER LOW TOWARD THE END OF THE WEEK...WHICH EXPLAINS SOME
MINOR THERMAL AND HEIGHT DIFFERENCES TOWARD NEXT WEEKEND. THE 00Z
ECMWF RETAINS A CLOSED LOW OVER THE PAC NW THROUGH FRI WITH MUCH
SLOWER EASTWARD PROGRESSION OF THIS FEATURE...WHILE THE GFS AND GEM
EJECT THIS SYSTEM EAST 1-1/2 DAYS EARLIER. THE ECMWF SOLUTION HAS
SOME SUPPORT FROM GEFS MEMBERS. HOWEVER...MEAN GEFS SOLUTIONS ARE
LEANING TOWARD THE GEM/GFS SOLUTION OF A RIDGE SQUASHING WAVE
FRI...WHICH COULD SUPPORT A SMALL CHANCE FOR LIGHT SNOW AND SLIGHTLY
COOLER TEMPS ACROSS THE NORTHERN ZONES FRI. HENCE...HAVE REMAINED
CONSERVATIVE PER SIG TRENDING TOO FAR FROM CONSENSUS AND PREVIOUS
FORECAST NUMBERS...ESP IN THIS PERIOD. OTHERWISE...DRY NW FLOW WILL
PREVAIL THROUGH THE REMAINDER OF THE PERIOD...WITH MUCH MILDER
CONDITIONS EXPECTED TO CONTINUE INTO THE FOLLOWING WEEK PER ZONAL
FLOW...GIVEN STRONG INDICATIONS FOR REMOVAL OF THE NORTH ATLANTIC
BLOCK.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
SHORT TERM...26
EXTENDED...JC
AVIATION...JC
AREA FORECAST DISCUSSION
NWS FORT WORTH TX
940 AM CST MON DEC 31 2012
.AVIATION...
AMENDED TAFS TO SHOW DECREASING VISIBILITIES AND CEILINGS AS WARM
FRONT APPROACHES FROM THE SOUTHWEST. DONT THINK THE WARM FRONT
WILL MOVE THROUGH TAF SITES AND THEREFORE HAVE KEPT WINDS S/SE
THROUGH THIS EVENING. RUC FORECAST OF CIGS NEAR 200-500 FEET LOOK
REASONABLE AND VSBY SHOULD DROP BELOW 2 MILES. IT IS UNCLEAR HOW
MUCH IMPROVEMENT THERE WILL BE LATER THIS AFTERNOON BUT AS WINDS
GO WESTERLY JUST ABOVE THE SURFACE THIS MAY ALLOW VSBY TO IMPROVE.
RAIN SHOULD END AROUND 18-19Z. WILL CONTINUE TO MONITOR TRENDS.
TR.92
.../PREVIOUS AVIATION DISCUSSION/...
CIGS AND VSBYS HAVE DECREASED DURING THE PAST FEW HOURS DUE TO THE
LIGHT RAIN SPREADING EAST TO THE I-35 CORRIDOR. THIS TREND SHOULD
CONTINUE...AND TAFS WILL LIKELY BE INITIALIZED WITH IFR
CIGS WHICH SHOULD PERSIST THROUGH MUCH OF THE DAY. MEANWHILE A
COASTAL TROUGH WILL TRY TO LIFT NORTH LATER TODAY AS A WARM FRONT...
BUT SHOULD REMAIN SOUTH OF TAF LOCATIONS. ISENTROPIC ASCENT WILL
CONTINUE NORTH OF THE BOUNDARY...FURTHER SATURATING THE LOWER
ATMOSPHERE AND LIKELY ADDING FOG TO THE MIX. EXPECT GENERALLY
1-3SM VISIBILITIES WITH CIGS LOWERING TO NEAR 005 AT ALL LOCATIONS
BY MIDDAY.
INITIAL SHORTWAVE WILL EJECT NORTHEAST OF THE REGION THIS EVENING
ALLOWING A WEAK COLD FRONT TO EASE SOUTH OF THE TERMINALS. THIS
MAY ALLOW CONDITIONS TO IMPROVE BRIEFLY AROUND SUNSET...BUT
THE SHALLOW NATURE OF THE COOL AIRMASS AND QUICK RETURN OF
ISENTROPIC LIFT MAY CAUSE FOG FORMATION AND REDUCED
VISIBILITIES AGAIN BY 06Z. FORTUNATELY THE LATEST MOS GUIDANCE
HAS BACKED OFF THE SEVERITY OF THE CONDITIONS TONIGHT SO IT LOOKS
LIKE FOG MAY BE SHORT LIVED DURING THE OVERNIGHT HOURS. A SECOND
SHORTWAVE WILL THEN TRANSLATE THE AREA TUESDAY MORNING...WHICH
SHOULD CREATE A STRONGER PUSH OF DRIER AIR AND IMPROVING
CONDITIONS AFTER 12Z TUESDAY.
30
&&
.UPDATE...
WE HAVE NOTICED A FEW MITIGATING ITEMS THAT IS KEEPING RAIN FROM
BEING MORE THAN JUST VERY LIGHT RAIN OR DRIZZLE. ONE REASON IS THE
DRY LAYER NOTED ON THE 12Z FWD SOUNDING BETWEEN 850-650MB...MEANING
THE COLUMN IS SHALLOW AND NOT DEEPLY SATURATED. SECOND...THE DRY
SLOT ASSOCIATED WITH THE UPPER JET MAX ROUNDING THE BASE OF THE
FOUR CORNERS UPPER TROUGH IS NOW PUNCHING NORTHEAST UP THROUGH
WESTERN TEXAS AND MOVING EAST FASTER THAN EXPECTED.
WITH THESE TRENDS IN MIND...HAVE UPDATED MORNING FORECAST TO LOWER
POPS IN THE WESTERN THIRD OF NORTH TEXAS INTO THE CHANCE CATEGORY...
GOING TO SLIGHT CHANCE IN THE AFTERNOON. TOO MUCH UNCERTAINTY ON
THE AFTERNOON PERIOD AND WILL MAINTAIN ONGOING FORECAST. RAIN
AMOUNTS WILL BE LIGHT WITH AREAS OF FOG EXPECTED THROUGH MUCH OF
THE DAY.
THE APPROACHING UPPER TROUGH WILL LIKELY STEEPEN LAPSE RATES
ACROSS CENTRAL/SOUTHEAST TEXAS NEAR FRONTAL WAVE TO OUR SOUTH.
WILL MAINTAIN ISOLATED THUNDERSTORM MENTION ACROSS THESE AREAS.
05/
&&
.PREV DISCUSSION... /ISSUED 300 AM CST MON DEC 31 2012/
A WET AND COOL FORECAST IS EXPECTED TODAY INTO THIS EVENING...AS
DEEP LONGWAVE TROUGH OVER THE GREAT BASIN/FOUR CORNERS REGION
CONTINUES MOVING PROGRESSIVELY EAST TOWARD THE SOUTHERN PLAINS THE
NEXT 24-36 HOURS. ISENTROPIC ASCENT AND WAA OVER THE TOP OF THE
FRONTAL INVERSION ANCHORED AROUND 800MB HAS ALREADY BEGUN IN
ERNEST ACROSS THE SOUTH PLAINS INTO WESTERN NORTH TX EARLY THIS
MORNING WITH WIDESPREAD AREAS OF LIGHT RAIN OCCURRING ACROSS THESE
AREAS. THE RAIN SHIELD WILL SPREAD GRADUALLY EAST ACROSS NORTH
TEXAS THROUGH THE DAY WITH THE BEST SATURATION AND UPGLIDE
OCCURRING ACROSS THE NORTHEAST HALF OF THE CWA WHERE RAINFALL
UPWARDS TO ONE INCH OR SLIGHTLY MORE ARE NOT OUT OF THE QUESTION
WITH LESSER AMOUNTS FURTHER SOUTH. ALSO WITH LOW LEVEL COLD AIR IN
PLACE...THE INCREASING LIGHT TO OCCASIONALLY MODERATE RAINFALL
WILL HELP BOTH VISIBILITIES AND CEILINGS FALL AFTER DAYBREAK AND
THROUGHOUT MOST OF THE DAY. EXPECT THE MOST WIDESPREAD FOG AND
RAIN TO OCCUR ACROSS THE NORTHERN COUNTIES...AND MORE PATCHY
ACROSS THE SOUTH AND WEST WITHIN THE WARMER TEMPERATURES NEAR THE
WARM FRONT. EITHER WAY...CONDITIONS WILL BE SLOPPY INTO THE
EVENING HOURS.
ANOTHER CHALLENGE TODAY IS HIGH TEMPERATURES...AS A FRONTAL WAVE
DEVELOPS ACROSS SOUTH-CENTRAL TEXAS AND MOVES UP THROUGH THE UPPER
TEXAS COAST DURING THE EVENING HOURS. MODELS HAVE DIFFERENT
PERSPECTIVES ON HOW FAR NORTH THE WARM FRONT WILL MOVE INTO OUR
CENTRAL TEXAS AND SOUTHEAST COUNTIES. HAVE DECIDED TO LEAN WITH A
COMPROMISE AT THIS POINT AS IT IS ANYONE/S GUESS ON THIS EVOLUTION
AND KEEP HIGHS IN THE 40S NORTH OF I-20...TO 55-60 IN OUR CENTRAL
TEXAS AND FAR SOUTHWEST COUNTIES. LAPSE RATES WILL STEEPEN WITHIN
THE NORTHWEST EDGE OF THE WARM NOSE AHEAD OF THE SYSTEM AND NEAR
THE WARM FRONT ACROSS OUR SOUTHERN COUNTIES THIS AFTERNOON AND
EVENING. WITH UNCERTAINTIES REGARDING WHERE THE WARM FRONT WILL
RESIDE...HAVE ONLY ADDED ISOLATED THUNDERSTORMS TO AREAS SOUTHEAST
OF A KILLEEN-ATHENS LINE THIS AFTERNOON/EVENING. DO NOT EXPECT
SEVERE STORMS...BUT A STRONG STORM OR TWO WITH HAIL IS POSSIBLE
WITH LOW FREEZING LEVELS IN PLACE. THERE COULD BE A BRIEF 3-6 HOUR
WINDOW FOR SURFACE-BASED ACTIVITY IN MILAM/ROBERTSON/LEON/ANDERSON
COUNTIES WHERE GUSTY WINDS COULD BE A THREAT AS WELL.
MEANWHILE TONIGHT...A COLD FRONT CURRENTLY OVER THE CENTRAL HIGH
PLAINS WILL ARRIVE ACROSS THE RED RIVER BY MID-LATE EVENING...THEN
SURGE SLOWLY THROUGH NEW YEARS MORNING. LOOK FOR AREAS OF FOG TO
CONTINUE AHEAD OF THE FRONT DURING THE EVENING HOURS WITH LIGHTER
WINDS AND WARMER TEMPERATURES. IT APPEARS ANY CHANCES FOR WINTER
PRECIPITATION WILL BE SHUT DOWN ACROSS OUR AREA WITH A DRIER
AIRMASS ARRIVING AND WESTERLY FLOW PROVIDING ISENTROPIC DOWNGLIDE
WITHIN THE LOWER LEVELS. A FEW SHOWERS WILL PERSIST ACROSS THE
SOUTHEAST COUNTIES THROUGH TUESDAY MORNING.
A DRY AND COLD PERIOD WILL OCCUR NEW YEARS DAY AND THROUGH THE
MIDDLE PART OF THE WEEK...AS A PERSISTENT TROUGH CONTINUES ACROSS
THE CENTRAL CONUS AND HELPS REINFORCE THE CHILLY AIRMASS IN PLACE
WITH ADDITIONAL POLAR SURGES. HAVE GONE BELOW MOS VALUES ON HIGH
TEMPERATURES WITH LITTLE IN THE WAY OF WAA OR RETURN FLOW OCCURRING
THROUGH THURSDAY. MID LEVEL ENERGY DOES DEEPEN ACROSS THE OKLAHOMA
INTO THE OZARKS ON THURSDAY AND HAVE HELD SLIGHT CHANCES FOR A COOL
RAIN WELL SOUTH OF I-20 WHERE WEAK ISENTROPIC ASCENT MAY OCCUR...BUT
CONFIDENCE IS NOT HIGH AT THIS TIME WITH MODEL DIFFERENCES ON
POSITION AND STRENGTH OF THIS SHORTWAVE DROPPING SOUTH.
OTHERWISE...A GRADUAL MODIFICATION ON TEMPS AND DRY CONDITIONS ARE
EXPECTED FRIDAY INTO NEXT WEEKEND...THOUGH AGAIN MODEL AGREEMENT
IS POOR ON OVERALL PATTERNS BOTH ALOFT AND AT THE SURFACE.
05/
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 46 38 45 29 41 / 100 10 10 5 10
WACO, TX 53 43 48 30 44 / 80 20 20 5 10
PARIS, TX 41 37 45 26 40 / 100 30 10 10 10
DENTON, TX 45 35 41 25 40 / 90 10 10 5 10
MCKINNEY, TX 44 37 43 25 40 / 100 10 10 5 10
DALLAS, TX 46 39 45 31 41 / 100 10 10 5 10
TERRELL, TX 47 40 46 28 41 / 100 20 10 10 10
CORSICANA, TX 52 43 48 32 42 / 90 40 20 10 10
TEMPLE, TX 56 44 49 31 45 / 70 30 20 5 10
MINERAL WELLS, TX 52 35 43 25 42 / 50 10 10 5 10
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
/
AREA FORECAST DISCUSSION
NWS GRAND JUNCTION CO
300 PM MST MON DEC 31 2012
.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 300 PM MST MON DEC 31 2012
IMPROVING CONDITIONS AS THE ACTIVE SHORT WAVE MOVES DOWNSTREAM...EXCEPT
FOR SOME ENHANCED CONVECTIVE SNOW SHOWERS OVER THE SAN JUANS. SOME
OF THIS ACTIVITY STILL IMPACTING PAGOSA SPRINGS...AND THE HIGHER
RESOLUTION RAP MODEL KEEPS SNOW ONGOING INTO THE EVENING HOURS BUT
ENDING BY MID EVENING. REFINED THE WINTER WEATHER ADVISORY FOR
THIS AREA AS CONFIDENCE IS HIGH THAT SNOW WILL HAVE ENDED BY LATE
EVENING. WITH PARTIAL CLEARING OVERNIGHT...TEMPERATURES WILL
PLUNGE AFTER SUNSET AND THEN LEVEL OUT AROUND MIDNIGHT.
UPSTREAM DISTURBANCE OVER MONTANA AND NORTH DAKOTA KEEPS A TROUGH
CARVED OUT OVER WESTERN COLORADO ON NEW YEARS DAY. MOISTURE SOURCE
FOR THIS SHORT WAVE IS CONTINENTAL AND THEREFORE PRECIPITABLE
WATER IS LOW...BUT DOES KEEP THE AIR MASS UNSETTLED DURING THE
LATE MORNING AND EARLY AFTERNOON HOURS. EXPECT SHALLOW CONVECTIVE
SNOW SHOWERS OR FLURRIES TO FORM ACROSS THE HIGH COUNTRY. AREAL
COVERAGE WILL NOT BE WIDESPREAD AND FAVOR NORTH FACING SLOPES.
ESSENTIALLY THIS SHORT WAVE KEEPS THE COLD AIR MASS LOCKED IN.
2013 STARTS THE WAY THAT 2012 ENDED...COLD WITH LITTLE CHANGE.
THE FOLLOWING UPSTREAM WAVE BRUSHES THE PARK/GORE RANGE LATE ON
TUESDAY NIGHT. LIMITED MOISTURE ONCE AGAIN BUT SOME OROGRAPHIC
FLURRIES ARE EXPECTED...OTHERWISE MOSTLY CLEAR WITH STRONG
RADIATIONAL COOLING AS SURFACE HIGH PRESSURE COVERS THE REGION.
.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 300 PM MST MON DEC 31 2012
IN GENERAL...LOOKS LIKE A MOSTLY DRY LAST HALF OF THE WEEK AS A
BLOCKING RIDGE DEVELOPS OVER THE INTERMOUNTAIN WEST WED AND THU. AS
THIS OCCURS...A SHORTWAVE IN NORTHERLY FLOW CLIPS OUR AREA WED AS
IT DROPS FROM CENTRAL CANADA THROUGH THE PLAINS. LITTLE MOISTURE
ASSOCIATED WITH IT OVER CO...SO WILL CONTINUE WITH JUST A SLIGHT
CHANCE OF SNOW MAINLY NEAR THE CONTINENTAL DIVIDE. LATE IN THE
WEEK...A PACIFIC SHORTWAVE FIGHTS THROUGH/OVER THE RIDGE CROSSING
THE NORTHERN ROCKIES EARLY ON FRIDAY AND BRUSHING BY OUR AREA ON
SATURDAY. AGAIN...LITTLE MOISTURE ASSOCIATED WITH IT IN THE MODELS.
RIDGE REBOUNDS OVER UT/CO BY SUNDAY. ECMWF THEN BRINGS A PROGRESSIVE
PACIFIC TROUGH ACROSS OUR AREA ON MONDAY...WHILE THE GFS INSTEAD
CLOSES OFF A LOW ALONG THE WEST.
THE MAIN CHALLENGE FOR THIS FORECAST PERIOD MAY BE THE VALLEY
TEMPERATURES...WHICH WILL BE SLOW TO WARM. SNOW COVER AND TRAPPED
COLD AIR WITH HIGH PRESSURE AT THE SURFACE WILL PROMOTE SURFACE
INVERSIONS WED-FRI THAT WILL BE DIFFICULT TO DISLODGE. THE WEAK
DISTURBANCES WED AND SAT DON/T LOOK STRONG ENOUGH TO SCOUR OUT MANY
VALLEYS...AND AREAS LIKE THE GRAND VALLEY AND I-70 CORRIDOR WILL SEE
AIR QUALITY SLOWLY DECLINE. HAVE UNDERCUT MOS AND CONSENSUS GUIDANCE
FOR THE VALLEYS AS A RESULT. HIGHER ELEVATIONS... HOWEVER...SHOULD
SEE A SLOW MODERATION IN TEMPS BY THE WEEKEND.
&&
.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 300 PM MST MON DEC 31 2012
CEILING AND VISIBILITY WILL GRADUALLY IMPROVE NEAR AND ACROSS THE
MOUNTAINS THIS EVENING AS SNOW DIMINISHES IN MOST AREAS BY 06Z. THE
MAIN AVIATION CONCERN WILL THEN BE THE POTENTIAL FOR FOG FORMATION
IN MANY OF THE VALLEYS. DO NOT ANTICIPATE DENSE FOG WITH THE LACK OF
SIGNIFICANT MELTING TO REALLY MOISTEN THE AIR NEXT TO THE GROUND
...BUT COLD TEMPERATURES AND FRESH SNOW COVER NEVERTHELESS COULD
RESULT IN SOME FOG. WILL ACCOUNT FOR THIS POSSIBILITY WITH EITHER
VCFG OR MVFR VISIBILITY IN BR IN ALL TAFS TONIGHT.
VFR CONDITIONS EXPECTED AT ALL TAF SITES TUESDAY AFTERNOON.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY UNTIL 9 PM MST THIS EVENING FOR COZ018-
019-023.
UT...NONE.
&&
$$
SHORT TERM...PF
LONG TERM...JAD
AVIATION...JAD
AREA FORECAST DISCUSSION...UPDATED
NWS FORT WORTH TX
1056 AM CST MON DEC 31 2012
.UPDATE...
A GLOOMY DAY CONTINUES ACROSS THE REGION THIS MORNING. WIDESPREAD
FOG CONTINUES WITH VISIBILITIES OCCASIONALLY BELOW A
MILE...MAINLY SOUTH OF INTERSTATE 20. MOST OF THE RAIN IS NOW EAST
OF A LINE FROM GAINESVILLE TO GRANBURY TO LAMPASAS...HOWEVER...A
FEW AREAS OF DRIZZLE ARE OCCURRING WEST OF THIS LINE ALONG WITH THE
FOG. THE RAIN WILL CONTINUE TO SLOWLY PROGRESS EAST TODAY WITH
HIGHEST RAIN CHANCES OVER THE NORTHEAST AND EASTERN COUNTIES. THE
RAIN WILL LIKELY COME TO AN END OVER ALL BUT THE SOUTHEASTERN
THIRD OF THE REGION BY SUNSET. A DRYLINE/WARM FRONT WILL PUNCH
INTO THE WESTERN ZONES THIS AFTERNOON...CLEARING OUT THE CLOUDS
AND ALLOWING TEMPS TO WARM INTO THE UPPER 50S. IN ADDITION...A
WARM FRONT WILL MOVE NORTH INTO OUR FAR SOUTH AND SOUTHEASTERN
COUNTIES...WARMING TEMPS THERE INTO THE MID AND UPPER 50S. IT IS
POSSIBLE THAT SOME 60 DEGREE TEMPS WILL BE REACHED IN EITHER OF
THESE TWO PLACES...BUT THE ARRIVAL OF BOTH FEATURES WILL BE LATER
IN THE DAY. UNTIL THEN...CLOUDY SKIES AND THE RAIN AND FOG WILL
KEEP TEMPERATURES COOL WITHOUT MUCH CHANGE THROUGHOUT THE DAY.
NEAR THE WARM FRONT LATER THIS AFTERNOON...SOME WEAK ELEVATED
INSTABILITY IS PRESENT ON AREA SOUNDINGS AND HAVE OPTED TO LEAVE
THE ISOLATED THUNDER MENTION IN THE FAR SOUTHEASTERN COUNTIES
AFTER 00Z/6 PM CST. WITH THE FREEZING LEVEL UP AROUND 11-12
KFT...WILL REMOVE THE MENTION OF HAIL FROM THE HWO.
82/JLD
&&
.AVIATION...
AMENDED TAFS TO SHOW DECREASING VISIBILITIES AND CEILINGS AS WARM
FRONT APPROACHES FROM THE SOUTHWEST. DONT THINK THE WARM FRONT
WILL MOVE THROUGH TAF SITES AND THEREFORE HAVE KEPT WINDS S/SE
THROUGH THIS EVENING. RUC FORECAST OF CIGS NEAR 200-500 FEET LOOK
REASONABLE AND VSBY SHOULD DROP BELOW 2 MILES. IT IS UNCLEAR HOW
MUCH IMPROVEMENT THERE WILL BE LATER THIS AFTERNOON BUT AS WINDS
GO WESTERLY JUST ABOVE THE SURFACE THIS MAY ALLOW VSBY TO IMPROVE.
RAIN SHOULD END AROUND 18-19Z. WILL CONTINUE TO MONITOR TRENDS.
TR.92
.../PREVIOUS AVIATION DISCUSSION/...
CIGS AND VSBYS HAVE DECREASED DURING THE PAST FEW HOURS DUE TO THE
LIGHT RAIN SPREADING EAST TO THE I-35 CORRIDOR. THIS TREND SHOULD
CONTINUE...AND TAFS WILL LIKELY BE INITIALIZED WITH IFR
CIGS WHICH SHOULD PERSIST THROUGH MUCH OF THE DAY. MEANWHILE A
COASTAL TROUGH WILL TRY TO LIFT NORTH LATER TODAY AS A WARM FRONT...
BUT SHOULD REMAIN SOUTH OF TAF LOCATIONS. ISENTROPIC ASCENT WILL
CONTINUE NORTH OF THE BOUNDARY...FURTHER SATURATING THE LOWER
ATMOSPHERE AND LIKELY ADDING FOG TO THE MIX. EXPECT GENERALLY
1-3SM VISIBILITIES WITH CIGS LOWERING TO NEAR 005 AT ALL LOCATIONS
BY MIDDAY.
INITIAL SHORTWAVE WILL EJECT NORTHEAST OF THE REGION THIS EVENING
ALLOWING A WEAK COLD FRONT TO EASE SOUTH OF THE TERMINALS. THIS
MAY ALLOW CONDITIONS TO IMPROVE BRIEFLY AROUND SUNSET...BUT
THE SHALLOW NATURE OF THE COOL AIRMASS AND QUICK RETURN OF
ISENTROPIC LIFT MAY CAUSE FOG FORMATION AND REDUCED
VISIBILITIES AGAIN BY 06Z. FORTUNATELY THE LATEST MOS GUIDANCE
HAS BACKED OFF THE SEVERITY OF THE CONDITIONS TONIGHT SO IT LOOKS
LIKE FOG MAY BE SHORT LIVED DURING THE OVERNIGHT HOURS. A SECOND
SHORTWAVE WILL THEN TRANSLATE THE AREA TUESDAY MORNING...WHICH
SHOULD CREATE A STRONGER PUSH OF DRIER AIR AND IMPROVING
CONDITIONS AFTER 12Z TUESDAY.
30
&&
.PREV UPDATE...
.UPDATE...
WE HAVE NOTICED A FEW MITIGATING ITEMS THAT IS KEEPING RAIN FROM
BEING MORE THAN JUST VERY LIGHT RAIN OR DRIZZLE. ONE REASON IS THE
DRY LAYER NOTED ON THE 12Z FWD SOUNDING BETWEEN 850-650MB...MEANING
THE COLUMN IS SHALLOW AND NOT DEEPLY SATURATED. SECOND...THE DRY
SLOT ASSOCIATED WITH THE UPPER JET MAX ROUNDING THE BASE OF THE
FOUR CORNERS UPPER TROUGH IS NOW PUNCHING NORTHEAST UP THROUGH
WESTERN TEXAS AND MOVING EAST FASTER THAN EXPECTED.
WITH THESE TRENDS IN MIND...HAVE UPDATED MORNING FORECAST TO LOWER
POPS IN THE WESTERN THIRD OF NORTH TEXAS INTO THE CHANCE CATEGORY...
GOING TO SLIGHT CHANCE IN THE AFTERNOON. TOO MUCH UNCERTAINTY ON
THE AFTERNOON PERIOD AND WILL MAINTAIN ONGOING FORECAST. RAIN
AMOUNTS WILL BE LIGHT WITH AREAS OF FOG EXPECTED THROUGH MUCH OF
THE DAY.
THE APPROACHING UPPER TROUGH WILL LIKELY STEEPEN LAPSE RATES
ACROSS CENTRAL/SOUTHEAST TEXAS NEAR FRONTAL WAVE TO OUR SOUTH.
WILL MAINTAIN ISOLATED THUNDERSTORM MENTION ACROSS THESE AREAS.
05/
&&
.PREV DISCUSSION... /ISSUED 300 AM CST MON DEC 31 2012/
A WET AND COOL FORECAST IS EXPECTED TODAY INTO THIS EVENING...AS
DEEP LONGWAVE TROUGH OVER THE GREAT BASIN/FOUR CORNERS REGION
CONTINUES MOVING PROGRESSIVELY EAST TOWARD THE SOUTHERN PLAINS THE
NEXT 24-36 HOURS. ISENTROPIC ASCENT AND WAA OVER THE TOP OF THE
FRONTAL INVERSION ANCHORED AROUND 800MB HAS ALREADY BEGUN IN
ERNEST ACROSS THE SOUTH PLAINS INTO WESTERN NORTH TX EARLY THIS
MORNING WITH WIDESPREAD AREAS OF LIGHT RAIN OCCURRING ACROSS THESE
AREAS. THE RAIN SHIELD WILL SPREAD GRADUALLY EAST ACROSS NORTH
TEXAS THROUGH THE DAY WITH THE BEST SATURATION AND UPGLIDE
OCCURRING ACROSS THE NORTHEAST HALF OF THE CWA WHERE RAINFALL
UPWARDS TO ONE INCH OR SLIGHTLY MORE ARE NOT OUT OF THE QUESTION
WITH LESSER AMOUNTS FURTHER SOUTH. ALSO WITH LOW LEVEL COLD AIR IN
PLACE...THE INCREASING LIGHT TO OCCASIONALLY MODERATE RAINFALL
WILL HELP BOTH VISIBILITIES AND CEILINGS FALL AFTER DAYBREAK AND
THROUGHOUT MOST OF THE DAY. EXPECT THE MOST WIDESPREAD FOG AND
RAIN TO OCCUR ACROSS THE NORTHERN COUNTIES...AND MORE PATCHY
ACROSS THE SOUTH AND WEST WITHIN THE WARMER TEMPERATURES NEAR THE
WARM FRONT. EITHER WAY...CONDITIONS WILL BE SLOPPY INTO THE
EVENING HOURS.
ANOTHER CHALLENGE TODAY IS HIGH TEMPERATURES...AS A FRONTAL WAVE
DEVELOPS ACROSS SOUTH-CENTRAL TEXAS AND MOVES UP THROUGH THE UPPER
TEXAS COAST DURING THE EVENING HOURS. MODELS HAVE DIFFERENT
PERSPECTIVES ON HOW FAR NORTH THE WARM FRONT WILL MOVE INTO OUR
CENTRAL TEXAS AND SOUTHEAST COUNTIES. HAVE DECIDED TO LEAN WITH A
COMPROMISE AT THIS POINT AS IT IS ANYONE/S GUESS ON THIS EVOLUTION
AND KEEP HIGHS IN THE 40S NORTH OF I-20...TO 55-60 IN OUR CENTRAL
TEXAS AND FAR SOUTHWEST COUNTIES. LAPSE RATES WILL STEEPEN WITHIN
THE NORTHWEST EDGE OF THE WARM NOSE AHEAD OF THE SYSTEM AND NEAR
THE WARM FRONT ACROSS OUR SOUTHERN COUNTIES THIS AFTERNOON AND
EVENING. WITH UNCERTAINTIES REGARDING WHERE THE WARM FRONT WILL
RESIDE...HAVE ONLY ADDED ISOLATED THUNDERSTORMS TO AREAS SOUTHEAST
OF A KILLEEN-ATHENS LINE THIS AFTERNOON/EVENING. DO NOT EXPECT
SEVERE STORMS...BUT A STRONG STORM OR TWO WITH HAIL IS POSSIBLE
WITH LOW FREEZING LEVELS IN PLACE. THERE COULD BE A BRIEF 3-6 HOUR
WINDOW FOR SURFACE-BASED ACTIVITY IN MILAM/ROBERTSON/LEON/ANDERSON
COUNTIES WHERE GUSTY WINDS COULD BE A THREAT AS WELL.
MEANWHILE TONIGHT...A COLD FRONT CURRENTLY OVER THE CENTRAL HIGH
PLAINS WILL ARRIVE ACROSS THE RED RIVER BY MID-LATE EVENING...THEN
SURGE SLOWLY THROUGH NEW YEARS MORNING. LOOK FOR AREAS OF FOG TO
CONTINUE AHEAD OF THE FRONT DURING THE EVENING HOURS WITH LIGHTER
WINDS AND WARMER TEMPERATURES. IT APPEARS ANY CHANCES FOR WINTER
PRECIPITATION WILL BE SHUT DOWN ACROSS OUR AREA WITH A DRIER
AIRMASS ARRIVING AND WESTERLY FLOW PROVIDING ISENTROPIC DOWNGLIDE
WITHIN THE LOWER LEVELS. A FEW SHOWERS WILL PERSIST ACROSS THE
SOUTHEAST COUNTIES THROUGH TUESDAY MORNING.
A DRY AND COLD PERIOD WILL OCCUR NEW YEARS DAY AND THROUGH THE
MIDDLE PART OF THE WEEK...AS A PERSISTENT TROUGH CONTINUES ACROSS
THE CENTRAL CONUS AND HELPS REINFORCE THE CHILLY AIRMASS IN PLACE
WITH ADDITIONAL POLAR SURGES. HAVE GONE BELOW MOS VALUES ON HIGH
TEMPERATURES WITH LITTLE IN THE WAY OF WAA OR RETURN FLOW OCCURRING
THROUGH THURSDAY. MID LEVEL ENERGY DOES DEEPEN ACROSS THE OKLAHOMA
INTO THE OZARKS ON THURSDAY AND HAVE HELD SLIGHT CHANCES FOR A COOL
RAIN WELL SOUTH OF I-20 WHERE WEAK ISENTROPIC ASCENT MAY OCCUR...BUT
CONFIDENCE IS NOT HIGH AT THIS TIME WITH MODEL DIFFERENCES ON
POSITION AND STRENGTH OF THIS SHORTWAVE DROPPING SOUTH.
OTHERWISE...A GRADUAL MODIFICATION ON TEMPS AND DRY CONDITIONS ARE
EXPECTED FRIDAY INTO NEXT WEEKEND...THOUGH AGAIN MODEL AGREEMENT
IS POOR ON OVERALL PATTERNS BOTH ALOFT AND AT THE SURFACE.
05/
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 46 38 45 29 41 / 90 10 10 5 10
WACO, TX 53 43 48 30 44 / 70 20 20 5 10
PARIS, TX 43 37 45 26 40 / 100 30 10 10 10
DENTON, TX 45 35 41 25 40 / 80 10 10 5 10
MCKINNEY, TX 45 37 43 25 40 / 100 10 10 5 10
DALLAS, TX 46 39 45 31 41 / 100 10 10 5 10
TERRELL, TX 48 40 46 28 41 / 100 20 10 10 10
CORSICANA, TX 52 43 48 32 42 / 90 40 20 10 10
TEMPLE, TX 56 44 49 31 45 / 60 30 20 5 10
MINERAL WELLS, TX 51 35 43 25 42 / 10 10 10 5 10
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
92/82
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
556 PM EST MON DEC 31 2012
.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO MOVE OFFSHORE TONIGHT...WHILE A
WEAK LOW PRESSURE LOW PRESSURE SYSTEM WILL PASS ALONG THE GULF
COAST OVERNIGHT AND TUESDAY. THIS SYSTEM WILL BRING A MIX OF RAIN
AND WINTRY PRECIPITATION TO THE AREA TONIGHT...BEFORE
PRECIPITATION TRANSITIONS TO RAIN LATE TUESDAY MORNING. THE SYSTEM
WILL PAST EAST OF THE AREA TUESDAY NIGHT...WITH HIGH PRESSURE
BUILDING IN FROM THE WEST ON WEDNESDAY.
&&
.NEAR TERM /THROUGH TUESDAY/...
AS OF 530 PM EST MONDAY...
DEWPOINTS REMAIN VERY LOW ACROSS THE REGION ATTM AND EXPECT THIS
TO KEEP MOST PRECIP ALOFT. HOWEVER AS PRECIP CONTINUES TO STREAM
IN FROM THE WEST PER LATEST REGIONAL RADARS EXPECT SOME DEGREE OF
SATURATION TO OCCUR ESPCLY HIGHER ELEVATIONS ALONG THE I-77
CORRIDOR THIS EVENING DESPITE MODELS SUGGESTING OTHERWISE. THUS
ADDING IN A BIT MORE LOW POP ACROSS SW VA INTO TONIGHT WHERE
EXPECT MAY BE SOME SLEET MIXED IN ONCE PRECIP STARTS TO REACH THE
SURFACE. WILL NEED TO WATCH AND SEE IF CAN GET ENOUGH COOLING TO
PUSH TEMPS DOWN TO NEAR FREEZING LATER ON WHICH MAY NOT OCCUR
UNTIL LATE TONIGHT IF AT ALL.
OTRW AS MORE ORGANIZED PRECIPITATION MOVES INTO THE AREA LATE
TONIGHT...BELIEVE WE WILL SEE LOW LEVEL TEMPERATURES QUICKLY DROP
DUE TO EVAPORATIVE COOLING...RESULTING IN PERIODS OF SNOW
INITIALLY...PERHAPS CHANGING OVER TO POCKETS OF SLEET OR FREEZING
RAIN TOWARD SUNRISE ESPCLY FAR NW. BECAUSE THE EVAPORATIVE
COOLING MAY BE STRONG ENOUGH TO LOWER THE ATMOSPHERIC COLUMN BELOW
FREEZING...RESULTING IN MAINLY SNOW...AND DUE TO THE LIGHT
PRECIPITATION AMOUNTS EXPECTED...HAVE DECIDED TO FOREGO A WINTER
WEATHER ADVISORY AT THIS TIME...ALTHOUGH THE EVENING SHIFT MAY
DECIDE TO ISSUE ONE LATER.
AFTER SUNRISE WEDNESDAY...LOW LEVEL TEMPERATURES ARE EXPECTED TO
REBOUND ABOVE FREEZING...RESULTING IN MAINLY RAIN ACROSS THE
AREA...WHILE PORTIONS OF SOUTHEAST WEST VIRGINIA AND THE ALLEGHANY
HIGHLANDS WILL LIKELY KEEP SNOW THROUGH THE AFTERNOON. AS THE LOW
PRESSURE SYSTEM CONTINUES EAST THROUGH THE DAY...EXPECT WINDS
ACROSS THE AREA TO BECOME MORE NORTHWESTERLY DURING THE EVENING...
ALLOWING COLDER AIR TO BUILD IN WHICH WILL CAUSE RAIN TO
TRANSITION TO SNOW SHOWER ACTIVITY FROM WEST TO EAST.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
AS OF 220 PM MONDAY...
POSITION OF UPPER JET AND SFC FEATURES ARE GOING TO IMPACT OUR
WEATHER TUES NIGHT AS MAIN FOCUS OF PRECIP SHIFTS SOUTH OF US. STILL
ENOUGH AMPLE MOISTURE EARLY TO KEEP HIGHER POPS OVER THE SOUTH AND
WEST...WITH RAIN TRANSITIONING OVER TO SNOW AS COLDER AIR STARTS TO
WORK BACK IN FROM THE NORTHWEST. MODELS ARE IN ENOUGH AGREEMENT AND
ARE KEEPING THE THERMAL PROFILE AS MORE OF A RAIN/SNOW
LAYOUT...GIVEN LACK OF DEEP SW FLOW AT 8H WITH WEAK WARM NOSE. THERE
APPEARS TO BE AT TIMES A SLIGHT RISE ABOVE FREEZING EARLY THAT
CANNOT RULE OUT SLEET THOUGH ITS MARGINAL SO LEFT THE PTYPE TUE
EVENING AS RAIN/SNOW.
LATE TUESDAY NIGHT...THE SYSTEM SHIFTS SOUTHEAST AND WILL SEE PRECIP
START TO WANE. MOISTURE BECOMES SHALLOW OVER THE MTNS SUCH THAT
FREEZING DRIZZLE WILL FALL IN THE HIGHER RIDGES.
HIGH PRESSURE STARTS TO WORK INTO THE CENTRAL APPALACHIANS WEDNESDAY
BUT THE SFC FRONT STAYS LOCKED IN OVER THE SOUTHEAST. MAY SEE THE
SOUTHERN HALF OF THE CWA STAY CLOUDY WEDNESDAY WITH SW FLOW
ALOFT....BUT WILL BE CLOSE. ALLOWED FOR MORE CLOUDS THOUGH SHOULD BE
SOME SUNSHINE AT TIMES ESPECIALLY NORTH OF A LINE FROM I-81 IN THE
SOUTHWEST TO LYNCHBURG.
APPEARS MODELS START TO EDGE SOME MOISTURE BACK OUR WAY WED NIGHT-
THU. MARGINAL AT BEST AND WILL KEEP POPS SMALL OVER THE SRN CWA
MAINLY SOUTH OF VA/NC BORDER. IF PRECIP GETS IN EARLY ENOUGH COULD
SEE A FEW SNOW FLAKES AND/OR SLEET PELLETS ACROSS SOUTHSIDE VA/NRN
NC. STILL NOT EXPECTING MUCH.
TEMPS THIS PERIOD STAY COOL GIVEN MORE CLOUDS. HIGHS WED-THU RANGE
FROM THE MID TO UPPER 30S MTNS TO LOWER TO MID 40S EAST.
LOWS ARE GOING TO BE IMPACTED BY CLOUDS AS WELL WITH 20S WEST TO
AROUND 30 TO LOWER 30S SOUTHEAST.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 230 PM EST MONDAY...
LOW PRESSURE OFF THE SOUTHEAST COAST WILL CONTINUE TO MOVE EAST INTO
THE ATLANTIC OCEAN THURSDAY NIGHT INTO FRIDAY MORNING. WILL ALLOW
FOR A SLIGHT CHANCE OF RAIN THURSDAY EVENING IN OUR SOUTHEAST WITH
ECMWF SHOWING THE NORTHERN EXTENT OF THE ASSOCIATED PRECIPITATION
BRUSHING THE SOUTHEAST CORNER OF THE CWA. MODEL DIFFERENCES REMAIN
WITH THE TIMING AND STRENGTH OF THE SHORTWAVE WHICH PIVOTS OUT OF
THE OHIO VALLEY AROUND THE UPPER TROUGH THURSDAY NIGHT. BECAUSE OF
THIS UNCERTAINTY...KEPT SOME LIGHT POPS IN THE WESTERN UPSLOPE AREAS
THURSDAY NIGHT INTO FRIDAY. HIGH PRESSURE WILL BUILD EAST OUT OF THE
CENTRAL U.S. ON FRIDAY. THE 1030 MB SURFACE HIGH WILL REMAIN ACROSS
THE REGION DURING THE WEEKEND. WITH THE HIGH CENTER SETTLING SOUTH
AND A SOUTHWEST FLOW WILL CONTINUE TO MODERATE TEMPERATURES EARLY
NEXT WEEK. ANOTHER STORM MAY SPREAD MOISTURE INTO OUR REGION OUT OF
THE CENTRAL PLAINS AROUND THE MIDDLE OF NEXT WEEK.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
AS OF 540 PM EST MONDAY...
EXPANSIVE MID DECK CANOPY CONTINUES TO SLOWLY LOWER ACROSS THE
REGION FROM WEST TO EAST ATTM...ALTHOUGH BASES STILL GENERALLY 8 KFT
AND ABOVE. RADAR IS ALSO INDICATING LIGHT RETURNS MAKING THEIR WAY
ACROSS THE FAR SW MOUNTAINS INTO THE AREA...BUT WITH THE LOW
LEVELS STILL VERY DRY...DO NOT SEE MORE THAN LIGHT SPRINKLES OR A
FEW SLEET PELLETS MAKING IT TO THE SURFACE OVER THE NEXT FEW
HOURS.
MODELS CONTINUE TO SLOW DOWN ANY EASTWARD PROGRESSION OF PRECIP
OVERNIGHT...LIKELY DUE TO SO MUCH DRY AIR AND ONLY LIGHT PRECIP
GIVEN A LACK OF A WELL DEFINED SURFACE SYSTEM. GUIDANCE ALSO
REMAINS A BIT WARMER PER LESS EVAPORATIVE COOLING PROVIDED BY
ONLY VERY LIGHT PRECIP WITH EVEN THE LATEST RAP AND LOCAL WRF
SOLUTIONS QUITE DRY UNTIL AROUND DAYBREAK. HOWEVER...MODEL INIT
REMAINS ALL OVER THE PLACE UNDER SUCH A STRUNG OUT AREA OF DEEP
MOISTURE ALONG THE SRN JET AND LIKELY HAVING A HARD TIME IN WHERE
TO FOCUS PRECIP ATTM. THUS HAVE KEPT IN LIGHT MIXED PRECIP FOR
MANY OF THE WESTERN SITES WITH PERHAPS A PERIOD OF VERY LIGHT
FREEZING RAIN POSSIBLE IN THE VALLEYS AT KLWB/KBCB TOWARD DAWN BUT
CONFIDENCE LOW. OTRW INCLUDING A BIT MORE IN THE WAY OF PL MENTION
AT LEAST AT THE ONSET OVERNIGHT ACROSS THE WEST WHILE LEAVING
THINGS MAINLY VFR OVERNIGHT WITH ONLY SPOTTY -RA OUT EAST.
PRECIPITATION WILL BECOME WIDESPREAD TUESDAY MORNING WITH A MUCH
BETTER PROBABILITY OF MVFR OR EVEN IFR CONDITIONS...AND LOW TO
MEDIUM CONFIDENCE THAT SITES FROM KBCB WESTWARD WILL SEE MIXED
PRECIPITATION CHANGE TO RAIN BY LATE MORNING AS TEMPERATURES WARM.
HOWEVER KLWB MAY GET STUCK AROUND FREEZING INTO THE AFTERNOON SO
MAY BE TOUGH TO DISLODGE THE MIXED BAG THERE UNTIL PRECIP TAPERS
OFF IN THE AFTERNOON. AS A SURFACE LOW PRESSURE SYSTEM PASSES
THROUGH THE CAROLINAS TUESDAY AND TUESDAY NIGHT...COLDER AIR WILL
MOVE INTO THE AREA. ON TUESDAY EVENING PRECIPITATION WILL CHANGE
TO SNOW SHOWERS...WHICH WILL CONTINUE IN SOUTHEAST WEST
VIRGINIA...INCLUDING KLWB AND KBLF INTO EARLY WEDNESDAY MORNING.
VFR WEATHER IS EXPECTED WEDNESDAY AFTERNOON INTO SATURDAY FOR
MOST OF THE REGION. A LOW PRESSURE SYSTEM PASSING WELL TO THE
SOUTH MAY BRING SUB-VFR CONDITIONS TO DAN ON THURSDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...NF
NEAR TERM...JH/NF
SHORT TERM...WP
LONG TERM...KK
AVIATION...AMS/JH/NF
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
332 PM CST MON DEC 31 2012
.VERY SHORT TERM...TONIGHT AND NEW YEARS DAY...FORECAST CONFIDENCE MEDIUM.
THE GREATEST UNCERTAINTY FOR TONIGHT IS SKY COVER...WHICH WILL
IMPACT THE LOW TEMPERATURES.
COLD AIR ADVECTION WITH CYCLONIC FLOW ALOFT LED TO STRATUS OVER
SOUTHERN WISCONSIN TODAY. THE STRATUS IS DISSIPATING FROM WEST TO
EAST THIS AFTERNOON...AND ALREADY SCATTERED OUT IN MADISON.
MEANWHILE...THE CIRRUS SHIELD OVER SOUTHERN WI SEEMS TO BE TAKING A
LITTLE LONGER TO MOVE OUT OF THE AREA...ALTHOUGH IT APPEARS THIN ON
THE VISIBLE SATELLITE IMAGERY.
925MB TEMPS WILL DROP DOWN TO -12 TO -14C OVERNIGHT. THE PRESSURE
GRADIENT WILL WEAKEN AS HIGH PRESSURE SHIFTS INTO WESTERN WISCONSIN
TONIGHT. SO TEMPS WILL BE SLOWER TO FALL IN THE EVENING...BUT WILL
LIKELY PLUMMET AFTER MIDNIGHT...ESPECIALLY NORTHWEST OF MADISON TO
FOND DU LAC SINCE THEY WILL HAVE THE LONGEST TIME TO RADIATE OUT.
WHILE THE STRATUS WILL LIKELY CLEAR IN THE SOUTHEAST FORECAST AREA
BEFORE MIDNIGHT...IT MAY TAKE LONGER FOR THE CIRRUS TO CLEAR...THUS
KEEPING THE TEMPS HIGHER THROUGH THE NIGHT. TRIED TO STICK CLOSE TO
MOS GUIDANCE IN THIS AREA.
925MB TEMPS WILL HOLD STEADY ON TUESDAY. DESPITE THE EXPECTED
SUNSHINE...MAX TEMPS SHOULD BARELY RISE OUT OF THE SINGLE DIGITS BY
THE AFTERNOON WITH THE EXCEPTION OF NEAR THE LAKESHORE.
.SHORT TERM...TUESDAY NIGHT THROUGH THURSDAY.
TUESDAY NIGHT AND WEDNESDAY...FORECAST CONFIDENCE MEDIUM TO HIGH.
THERMAL TROUGH MOVES OFF TO THE EAST WITH INCREASING CLOUDS AND WARM
AIR ADVECTION ON DEVELOPING SOUTHERLY WINDS AS SURFACE RIDGE SLIDES
SOUTHEAST LEADING TO OVERNIGHT LOWS AROUND/JUST AFTER MIDNIGHT...
THEN STEADY OR SLOWLY WARMING TEMPERATURES. RISE CONTINUES INTO
WEDNESDAY AHEAD ON SOUTH WINDS AHEAD OF SHORT WAVE TROUGH AND
ASSOCIATED SURFACE LOW. BEST LOWER LAYER Q-VECTOR CONVERGENCE
CROSSES REGION WEDNESDAY AFTERNOON...BUT MOISTURE LACKING EXCEPT IN
THE FAR NW...SO WILL LIMIT SLIGHT CHANCE POPS TO THERE.
WEDNESDAY NIGHT...FORECAST CONFIDENCE MEDIUM.
HAVE UPPED POPS TO CHANCE IN THE WEST AS MODELS ARE IN AGREEMENT
THAT MOISTURE WILL BE DEEP ENOUGH TO REACH THE DENDRITE GROWTH ZONE
FOR A FEW HOURS...WITH ENOUGH OMEGA FOR A POTENTIAL TO SQUEEZE OUT A
HUNDREDTH OF AN INCH OF QPF AND A FEW TENTHS OF AN INCH OF VERY
LIGHT SNOW. THIS IS STILL A HIGH PROBABILITY OF OCCURRENCE AND LOW
PROBABILITY OF MEASURING SITUATION. TEMPERATURES WILL ONLY COOL
SLOWLY THROUGH THE EVENING AND INTO THE OVERNIGHT...THEN DIP TOWARDS
DAYBREAK WITH CLOUDS HANGING IN AND COLD AIR ADVECTION NOT KICKING IN
UNTIL AFTER 06Z TO 09Z.
THURSDAY...FORECAST CONFIDENCE MEDIUM
COLD ADVECTION DURING THE DAY WILL PREVENT MUCH OF A TEMPERATURE
RISE...HIGHS IN THE LOW TO MID 20S...AS THERMAL TROUGH MOVES
ACROSS REGION DURING THE DAY. CLOUDY SKIES EARLY AND PARTLY SUNNY
SKIES AT BEST IN THE AFTERNOON AS SURFACE RIDGE BUILDS IN LATE IN
THE DAY.
.LONG TERM...HURSDAY NIGHT THROUGH MONDAY. FORECAST CONFIDENCE LOW
TO MEDIUM.
MODERATING TREND BEGINS WITH MORE WESTERLY UPPER FLOW AS SHORT WAVE
BREAKS DOWN WESTERN RIDGE AND BROAD SURFACE HIGH SETS UP OVER THE
SOUTHERN PLAINS. MODELS DIFFER WITH PCPN CHANCES WITH THIS SHORT
WAVE AS IT MOVES ACROSS THE UPPER MIDWEST SATURDAY/SUNDAY. BLENDED
SOLUTIONS DID NOT CONVERGE WITH A HIGH ENOUGH POP IN ANY ONE PERIOD
TO PRODUCE PRECIPITATION...THOUGH GFS/ECMWF/GEMNH ALL DO PRODUCE
LIGHT QPF. WILL LEAVE DRY FOR NOW...BUT WOULD NOT BE SURPRISED TO
SEE POPS IN LATER FORECASTS. WEST SOUTHWEST FLOW BEHIND THE SHORT
WAVE LEADS TO DOWNSLOPE WARMING OVER THE NORTHERN PLAINS AND RAISES
THICKNESSES TO SUPPORT UPPER 20S TO LOWER 30S SUNDAY...AND LOW TO
MID 30S MONDAY.
&&
.AVIATION/00Z TAFS/...
COLD AIR ADVECTION WITH CYCLONIC FLOW ALOFT LED TO STRATUS OVER
SOUTHERN WISCONSIN TODAY. THE AREA OF LOW CLOUDS CANNOT BE SEEN
BENEATH THE DECK OF THE CIRRUS SHIELD IN VISIBLE SATELLITE
IMAGERY...SO RELYING ON SURFACE OBSERVATIONS. THE NORTHWEST EDGE OF
THE STRATUS DECK HAS BEEN GRADUALLY ERODING FROM THE
NORTHWEST...ALREADY SCATTERING OUT AT KMSN. IT HAS NOT SPREAD INTO
KENW YET...BUT ANTICIPATING THAT IT DOES FOR A FEW HOURS THIS
EVENING.
THE LATEST RAP SOUNDINGS IN BUFKIT PICK UP ON THE STRATUS TODAY AND
NOW CLEAR THEM OUT AROUND 04Z. THE CIRRUS MAY BE A LITTLE SLOWER TO
CLEAR.
EXPECTING CLEAR SKIES/VFR CONDITIONS ON TUESDAY WITH LIGHTER WINDS
AS HIGH PRESSURE BUILDS OVER THE AREA.
&&
.MARINE...WINDS WILL CONTINUE TO DIMINISH OVERNIGHT AND TUESDAY AS
HIGH PRESSURE BUILDS INTO THE REGION. WITH COLDER AIR SETTLING
IN...WILL NEED TO WATCH FOR FREEZING SPRAY THREAT REST OF THE WEEK.
WINDS WILL INCREASE OUT OF THE SOUTHWEST ON WEDNESDAY AS LOW
PRESSURE MOVES ACROSS LAKE SUPERIOR.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&
$$
TONIGHT/TUESDAY AND AVIATION/MARINE...MRC
TUESDAY NIGHT THROUGH MONDAY...REM
AREA FORECAST DISCUSSION...UPDATED
NWS MILWAUKEE/SULLIVAN WI
1208 PM CST MON DEC 31 2012
.UPDATE...
COLD AIR ADVECTION WITH CYCLONIC FLOW ALOFT IS LEADING TO STRATUS
OVER SOUTHERN WISCONSIN THIS MORNING. TEMPERATURES WILL HOLD STEADY
IN THE WEST AND FALL IN THE EAST THROUGH THE DAY. THE CLOUDS SHOULD
LINGER THROUGH MUCH OF THE DAYLIGHT HOURS AND THERE IS UNCERTAINTY
ABOUT HOW QUICKLY THEY WILL CLEAR OVERNIGHT.
&&
.AVIATION/18Z TAFS/...
COLD AIR ADVECTION WITH CYCLONIC FLOW ALOFT IS LEADING TO STRATUS
OVER SOUTHERN WISCONSIN THIS MORNING. THE AREA OF LOW CLOUDS CANNOT
BE SEEN BENEATH THE DECK OF THE THICK CIRRUS SHIELD IN VISIBLE
SATELLITE IMAGERY...SO RELYING ON SURFACE OBSERVATIONS. THE
SOUTHEAST EDGE OF THE STRATUS DECK APPEARS TO BE FROM WEST BEND TO
SULLIVAN TO SOUTHERN DANE COUNTY TO MINERAL POINT AND PLATTEVILLE.
THE SSEC GOES-E CLOUD THICKNESS PRODUCT IS SHOWING HIGH PROBABILITY
FOR IFR OVER ALMOST ALL OF SOUTHERN WI EXCEPT THE LAKESHORE COUNTIES
AT THIS TIME. GIVEN THE BETTER MIXING RIGHT ALONG THE LAKE...LOW
CONFIDENCE ON THE STRATUS GETTING INTO MILWAUKEE AND KENOSHA.
THE RAP SOUNDINGS IN BUFKIT ARE PICKING UP ON THE STRATUS TODAY AND
THEY LOWER THE CEILINGS OVERNIGHT AND LINGER IT THROUGH LATE
TONIGHT. FOR NOW...WILL NOT JUMP ON THAT SOLUTION AND SCATTER OUT
THE CLOUDS JUST BEFORE MIDNIGHT. LOW CONFIDENCE.
&&
.PREV DISCUSSION... /ISSUED 307 AM CST MON DEC 31 2012/
TODAY AND TONIGHT...FORECAST CONFIDENCE IS MEDIUM.
LOW LEVEL MIXING...CONVERGENCE AND SHALLOW MOISTURE MAY YET CAUSE
STRATUS TO FORM VICINITY OF COLD FRONT PASSING THRU SRN WI EARLY
THIS MRNG. STRONG WARM AIR ADVECTION AHEAD OF THE FRONT CAUSED
TEMPS TO WARM INTO THE UPPER 20S TO LOWER 30S...WHICH WILL LIKELY
BE CLOSE TO THE DAYTIME HIGHS IN THE EASTERN AREAS. EXPECT THE
COLDER AIR TO SURGE INTO THE WEST EARLY THIS MRNG WITH MINIMAL
TEMPERATURE RECOVERY DURING THE DAY.
DIFFICULT TO IGNORE UPSTREAM SCT-BKN STRATUS FIELD OVER NORTHWEST
WI INTO MN. LOW LEVEL COLD AIR ADVECTION SETTLES INTO SRN WI TODAY
BEFORE BECOMING MORE NEUTRAL TONIGHT. LOW LEVEL CYCLONIC CURVATURE
LINGERS OVER THE AREA AS WELL...BUT ATMOSPHERE ABOVE INVERSION
REMAINS FAIRLY DRY THRU 10K FEET. BOTH NAM AND GFS SHOW LOW LEVEL
RH DECREASING TODAY...BUT THIS GUIDANCE DOES NOT APPEAR TO HAVE
GOOD HANDLE ON UPSTREAM STRATUS. LATEST HRRR ALSO BULLISH ON
MINIMAL LOW CLOUDS.
NEVER THE LESS...SRN WI WILL GET GRAZED BY PASSING HIGHER CLOUDS
FROM FORCING OCCURRING ALONG BAROCLINIC ZONE JUST TO THE SOUTH.
HENCE THINKING CLOUD CONDITIONS WILL VARY FROM PARTLY SUNNY TO
MOSTLY CLOUDY TODAY...AND WILL REMAIN MORE PESSIMISTIC AT THIS
TIME.
BUILDING SUBSIDENCE ASSOCIATED WITH APPROACHING RIDGING WILL
RESULT IN ANY STRATUS AND HIGHER CLOUDS CLEARING OVERNIGHT
TONIGHT. 925 TEMPS TUMBLE TO BETWEEN 11 AND 14 DEGREES CELSIUS
BELOW ZERO. WITH WIDESPREAD SNOW FIELD ACROSS SRN WI...EXPECT
TEMPERATURES TO FALL INTO THE SINGLE DIGITS ABOVE ZERO WITH SOME
BELOW ZERO READINGS. NORTHWEST WINDS CONTINUING AT 4 TO 10 KNOTS
WILL CAUSE WIND CHILL READINGS TO FALL TO BETWEEN 10 AND 15 BELOW
ZERO MOST AREAS LATE TONIGHT.
TUESDAY THROUGH WEDNESDAY NIGHT...FORECAST CONFIDENCE IS MEDIUM
TO HIGH.
SHORT TERM MODELS SHOWING MODEST 500MB SHORTWAVE TROUGH SLIDING
SOUTHEAST ACROSS THE AREA TUESDAY...WITH FLOW BECOMING
SOUTHWESTERLY BY 18Z WEDNESDAY...BEFORE MORE AMPLIFIED SHORTWAVE
TROUGH SLIDES SOUTHEAST INTO THE REGION WEDNESDAY NIGHT. AT THE
SURFACE...HIGH PRESSURE RIDGE KEEPS HOLD OF THE AREA TUESDAY AND
TUESDAY NIGHT...WITH A LOW PASSING NORTH OF THE AREA WEDNESDAY
NIGHT.
SOME MOISTURE IN THE LOW LEVELS MOVES INTO THE AREA LATER TUESDAY
NIGHT INTO WEDNESDAY. MODEST UPWARD VERTICAL MOTION SEEN WEDNESDAY
NIGHT WITH SHORTWAVE...WITH AREA FORECAST SOUNDINGS SHOWING SOME
MOISTURE IN THE LOW TO MID LEVELS. GFS SHOWING BETTER MOISTURE IN
THE LOW LEVELS THAN THE NAM. SPOTTY LIGHT QPF SEEN IN THE AREA
WEDNESDAY NIGHT ON GFS/CANADIAN/ECMWF...DRY ON NAM.
WILL CONTINUE TO MENTION LOW END POPS FOR LIGHT SNOW LATE
WEDNESDAY IN THE FAR WESTERN COUNTIES...AND ACROSS THE AREA
WEDNESDAY NIGHT...WITH TUESDAY INTO WEDNESDAY MAINLY DRY. COLD
TEMPERATURES WILL LINGER THROUGH THE PERIOD...WITH 925MB
TEMPERATURES TRYING TO CLIMB INTO THE SINGLE DEGREES BELOW ZERO
CELSIUS RANGE.
THURSDAY THROUGH SUNDAY...FORECAST CONFIDENCE IS MEDIUM.
ECMWF/GFS BOTH SHOWING SHORTWAVE TROUGH EXIT THE REGION...WITH THE
ASSOCIATED SURFACE LOW SHIFTING EAST. GFS FORECAST SOUNDINGS
SHOWING DRY AIR COLUMN DURING THIS TIME...SO KEPT DRY FORECAST
GOING. HIGH PRESSURE THEN PASSES SOUTH OF THE REGION THURSDAY
NIGHT THROUGH FRIDAY NIGHT...WITH WARM AIR ADVECTION TRYING TO
MOVE INTO THE REGION.
ECMWF/GFS THEN SHOW DIFFERENCES FOR SATURDAY THROUGH SUNDAY. THE
GFS TRIES TO BRING A 500MB SHORTWAVE TROUGH THROUGH THE REGION
SATURDAY INTO SATURDAY EVENING...ALONG WITH A COLD FRONT MOVING
SOUTHEAST THROUGH THE AREA 00Z SUNDAY. DECENT MOISTURE ON GFS
FORECAST SOUNDINGS ARE SEEN. LIGHT QPF OCCURS WITH THESE FEATURES.
ANOTHER SHORTWAVE MOVES SOUTHEAST INTO THE REGION LATER ON SUNDAY.
THE ECMWF SHOWS A 500MB SHORTWAVE TROUGH PASSING TO THE NORTHWEST
OF THE AREA SUNDAY AFTERNOON AND NIGHT...WITH MODEST NORTHWEST
FLOW ACROSS THE AREA. WEAK HIGH PRESSURE MOVES SOUTH OF THE AREA
SATURDAY AND SATURDAY NIGHT...WITH SOUTHWEST WINDS SUNDAY.
GIVEN THE DIFFERENCES...WENT WITH THE CONSENSUS POPS FOR THE
WEEKEND...WHICH KEEPS THINGS DRY. TEMPERATURES WERE HANDLED IN A
SIMILAR WAY...WHICH BRINGS MORE SEASONABLE TEMPERATURES TO THE
AREA.
AVIATION/12Z TAFS/...LOW LEVEL COLD AIR ADVECTION AND WEAK
CYCLONIC CURVATURE MAY ALLOW STRATUS TO DEVELOP OVER SRN WI TODAY
CONTINUING INTO THIS EVENING. HOWEVER QUITE A BIT OF DRY AIR
BETWEEN 2K AND 10K FEET. ALSO NEED TO WATCH UPSTREAM STRATUS FIELD
OVER SRN MN POSSIBLY ADVECTING INTO SRN WI LATER THIS MRNG AND
AFTN...BUT VERY WELL COULD MIX OUT IN DRIER AIR.
LATEST HRRR MODEL OPTIMISTIC ON VFR CONDITIONS TODAY...WHILE
LATEST NAM CONTINUES TO BRING PERIOD OF STRATUS INTO SRN WI BEHIND
CDFNT MOVING THRU NEXT FEW HOURS. HOWEVER NOT SEEING ANY INCREASE
IN STRATUS OVER CENTRAL WI. AT THIS POINT...CONFIDENCE LOW ON
TIMING AND COVERAGE OF MVFR LOW CLOUDS FOR THIS TAF PERIOD.
MARINE...WILL CONTINUE ONGOING SMALL CRAFT ADVY THROUGH 15Z THIS
MRNG. EXPECT GUSTY SOUTHWEST WINDS TO 25 KNOTS TO CONTINUE NEXT
FEW HOURS AHEAD OF CDFNT WHICH WILL BE PASSING ACROSS NEARSHORE
WATERS BETWEEN 11Z AND 14Z. WINDS WILL BECOME WEST AND THEN
NORTHWEST UPON FRONTAL PASSAGE THIS MRNG...HOWEVER LOW LEVEL COLD
AIR ADVECTION WEAK. HENCE STILL EXPECT WINDS TO MOSTLY SETTLE
BELOW SMALL CRAFT ADVISORY THRESHOLD LATER THIS MRNG. WITH COLDER
AIR SETTLING IN...WILL NEED TO WATCH FOR FREEZING SPRAY THREAT
REST OF THE WEEK.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&
$$
UPDATE...MRC
TODAY/TONIGHT AND AVIATION/MARINE...MBK
TUESDAY THROUGH SUNDAY...WOOD