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000
FXUS61 KLWX 291623
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1115 AM EST THU JAN 29 2004
.UPDATE...
FORECAST LOOKS GOOD OVERALL. DID A QUICK UPDATE TO ZONES TO MAKE
SOME MINOR WORDING CHANGES TO THE FORECAST SKY CONDITIONS. SKIES AT
LATE MORNING RANGED FROM PARTLY CLOUDY WEST TO MOSTLY SUNNY EAST.
EXPECT CLOUDS TO INCREASE THIS AFTERNOON...SO WILL GO WITH A PARTLY
CLOUDY FORECAST ACROSS THE BOARD. WLY WINDS HAVE PLAYED A BIG ROLE
IN GETTING MOST AREAS ABOVE FREEZING THIS MORNING...AFTER SUCH A
COLD START. MAY NEED TO BUMP READINGS UP A LITTLE LATER.
.SHORT TERM TDA AND TNGT...
SOME MID LVL MOISTURE NOTED NW OF CWA ATTM. MODELS IN AGREEMENT IN
ADVECTING THIS INTO THE AREA TDA. WILL START MCLR TDA...THEN EXPECT
SOME INCR IN CLDS. CDFNT MOVES THRU AREA TNGT. NOT MUCH PUNCH TO IT.
SLUG OF MOISTURE SHOWING UP IN THE 700-900 MB LAYER...KINDA DRY ABV
AND BLO THAT. MODELS SPIT OUT SOME SPOTTY 0.01". LIFT IS WEAK. WILL
KEEP A 20 POP GOING AND MENTION FLURRIES POSSIBLE AREA WIDE. NOT
EXPECTING MUCH IF ANYTHING FROM THIS.
SHAVED A COUPLE OF DEGS OFF MOS TEMPS TDA. IT WAS A LTL WARM YDY.
RDH
&&
.LONG TERM (FRIDAY THROUGH WEDNESDAY):
...SIGNIFICANT WINTER STORM POSSIBLE EARLY NEXT WEEK...
OBSERVATIONS: 5 DAY HEMISPHERIC 500MB ANALYSIS LOOP SHOWS A RIDGE
BEGINNING TO DOMINATE EASTERN CANADA...WHILE A JET ARRIVES OVER THE
EASTERN PACIFIC (SEEN VIA TIGHT HEIGHT GRADIENT). WATER VAPOR SHOWS
A RIDGE FORMING OFF THE PACIFIC COAST...AS TWO WAVES APPROACH...ONE
NEAR WESTERN BRITISH COLUMBIA...AND ANOTHER STRONGER WAVE NEARING
45N 150W. A THIRD VIGOROUS WAVE IS FURTHER WEST NEAR 45N 175E.
CLOSER TO HOME...A SHEARING WAVE OVER NORTHERN BAJA CALIFORNIA ALSO
CONTINUES ITS TRAVELS TO THE EAST SOUTHEAST. 300MB ANALYSIS PLACES A
130KT JET OVER THE UPPER MIDWEST WITHIN THE NORTHERN STREAM OF
PHASED EASTERN CONUS FLOW. A 190KT JET RESIDES OVER THE EASTERN
PACIFIC IN THE NORTHERN STREAM...WHILE A 120KT JET APPROACHES BAJA
CALIFORNIA FROM THE WEST IN THE SOUTHERN STREAM. 04Z SURFACE
ANALYSIS PLACES 1026MB HIGH PRESSURE OVER THE CENTRAL GULF
STATES...AND A LEE TROUGH EAST OF THE APPALACHIANS. THE NEXT COLD
FRONTAL BOUNDARY IS CURRENTLY BEING REINFORCED ACROSS THE MIDWEST.
FURTHER NORTHWEST...HIGH PRESSURE OF 1039MB IS CENTERED OVER
NORTHERN SASKATCHEWAN...WITH A CHILLY -56F READING AT 4Z.
MODELS: ETA/GFS/EUROPEAN/CANADIAN/UKMET SHOW THE COLD FRONTAL
BOUNDARY PASSING THROUGH THURSDAY NIGHT...WITH A WAVE ALOFT PASSING
FRIDAY. THE GFS NOW MATCHES OTHER SOLUTIONS WITHOUT A WAVE ALONG THE
BOUNDARY.
MEDIUM RANGE MODELS HAVE COME INTO GOOD AGREEMENT WITH A COLD AIR
DAMMING SCENARIO LATE THIS WEEKEND INTO NEXT WEEK. EACH MODEL
DEVELOPS WHAT COULD BECOME A SIGNIFICANT STORM...BUT CONSISTENCY
BETWEEN THE MODELS ON TIMING AND DETAILS ARE LACKING. ALL MODELS
HOWEVER SHOW A DAMMING SIGNATURE WITH ABOVE FREEZING TEMPERATURES AT
850MB.
ENSEMBLE DATA: 12Z GFS 500MB HEIGHT ENSEMBLES SHOW THE MIDLEVEL
TROUGH PASSING NORTHEAST LATE IN THE WEEK...AS RIDGING DOMINATES
SUNDAY AND MONDAY. A MORE SIGNIFICANT WAVE RIDES ACROSS THE
TENNESSEE VALLEY EARLY NEXT WEEK...AS ITS TROUGH AXIS PASSES INTO
NEW ENGLAND BY MIDWEEK.
GFS ENSEMBLE MOS FROM TUESDAY NIGHTS RUN INDICATES TEMPERATURES
WARMING INTO THE 40S BEGINNING SUNDAY. MEAN POPS RISE INTO THE
CHANCE CATEGORY MONDAY AND TUESDAY.
FORECAST RATIONALE: HAVE PLACED FLURRIES IN THE FORECAST FRIDAY WITH
THE APPROACHING WAVE...GIVEN DRY LOW LEVEL ATMOSPHERE. 18Z 8KM ETA
DID SHOW LIGHT QPF ALONG LOWER SOUTHERN MARYLAND...THIS CAN BE ADDED
IN IF THE TREND CONTINUES. OTHERWISE...EXPECT LAKE EFFECT/UPSLOPE
SPILL-OVER SNOW SHOWERS WEST OF THE ALLEGANY FRONT. LAKE ERIE HAS
FROZEN OVER...BUT DRY AIR WILL BE ABLE TO PICK UP WESTERN GREAT
LAKES MOISTURE...AND POSSIBLE SUBLIMATION OVER ERIE.
WITH -60F DEGREE TEMPERATURES OVER NORTHERN SASKATCHEWAN...AND
NEARLY -30F OVER THE NORTHERN PLAINS...NEXT AIRMASS WILL BE A COLD
ONE. SOUTHEASTWARD PROGRESS OF THE COLD AIRMASS WILL BE SLOWED BY
THE RELATIVELY WARMER WESTERN GREAT LAKES...BUT HEIGHT/PRESSURE
RISES BEHIND THE NEXT SYSTEM WILL ALLOW THE HIGH TO REPOSITION
ITSELF FURTHER EAST IN CANADA...WHEN A REINFORCING DRAINAGE OF THE
COLD AIRMASS IS THEN EXPECTED LATE THIS WEEKEND SOUTH DOWN THE
APPALACHIANS.
GIVEN THE DOMINATE ANTICYCLONE OVER EASTERN CANADA AND
SNOWPACK...AND AFTER COLLABORATION WITH HPC...AM CONFIDENT ENOUGH TO
DRASTICALLY CUT BACK ON ENSEMBLE MOS TEMPERATURES DURING THE LONG
RANGE.
MEDIUM RANGE MODELS AND ENSEMBLES ARE STILL WORKING OUT THE DETAILS
WITH THE NEXT SYSTEM EARLY NEXT WEEK. EACH SOLUTION APPEARS RATHER
WET FOR THIS REGION...JUST WITH DIFFERENT TIMING. AND WITH A COLD
AIRMASS IN PLACE...THIS COULD BE A RECIPE FOR A SIGNIFICANT STORM.
IF CONSISTENCY AMONG GUIDANCE INCREASES...MAY HAVE TO ISSUE A
WINTER STORM OUTLOOK TOMORROW TO GIVE A HEADS UP TO EMERGENCY
MANAGEMENT OFFICIALS BEFORE THE WEEKEND.
ROGOWSKI
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
.DC...NONE.
.MD...NONE.
.VA...NONE.
.WV...NONE.
.MARINE...NONE.
$$
Your thoughts would be appreciated. Thanks.
-ICE MAN JEB
