000
FXUS61 KLWX 200912
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
412 AM EST THU NOV 20 2008
.SYNOPSIS...
CLIPPER SYSTEM TO MOVE ACROSS THE AREA THROUGH FRIDAY. HIGH
PRESSURE BUILDS IN THIS WEEKEND...BEFORE ANOTHER STRONG UPPER
STORM SYSTEM MOVES INTO THE REGION MONDAY THROUGH TUESDAY.
IMPROVING CONDITIONS ARE EXPECTED FOR THE THANKSGIVING HOLIDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SURFACE ANALYSIS AT 06Z HAS A TROUGH AXIS EXTENDING FROM A LOW OVER
THE EASTERN GREAT LAKES SOUTH ACROSS THE EASTERN PANHANDLE OF WEST
VIRGINIA AND INTO SOUTHWESTERN VIRGINIA. TEMPERATURES ACROSS THE
REGION WERE IN THE MID 30S WITH DEW POINTS IN THE TEENS TO NEAR 20.
SURFACE OBSERVATIONS AND SATELLITE IMAGERY HAVE A SOLID MID DECK
OF CLOUDS ACROSS THE REGION. WATER VAPOR IMAGERY HAS AN UPPER LOW
OVER MAINE...WITH WESTERLY FLOW ALOFT.
THE CLIPPER SYSTEM OVER THE GREAT LAKES WILL GRADUALLY WEAKEN AFTER
IT DROPS SOUTHEAST TODAY. EXPECT UPSLOPE SNOW SHOWERS TO DEVELOP
LATER THIS MORNING ACROSS THE WEST...WITH A FEW SHOWERS MAKING IT
FURTHER EAST ACROSS THE POTOMAC HIGHLANDS THIS AFTERNOON. MAY SEE
SOME MINOR ACCUMULATIONS OUT WEST TODAY...LESS THAN AN INCH.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/...
UPSLOPE SNOW SHOWERS REALLY PICK UP OVERNIGHT. MAIN CHALLENGE FOR
TONIGHT IS THE HEADLINE. THERE IS CURRENTLY A WINTER STORM WATCH IN
EFFECT FOR THE WESTERN FIVE ZONES. WHILE THERE WILL BE SOME MINOR
ACCUMULATIONS IN THE HIGHER TERRAIN DURING THE LATE AFTERNOON...THIS
EVENT WILL NOT REALLY BEGIN UNTIL TONIGHT. CONFIDENCE IS NOT HIGH
ENOUGH TO UPGRADE TO A SECOND PERIOD WARNING. THEREFORE...WILL LEAVE
HEADLINES INTACT. AT THIS TIME...EXPECT AROUND 1 TO 3 INCHES TOTAL
ACCUMULATION OVERNIGHT IN THE HEADLINED AREA. SNOW SHOWERS WILL
SPREAD EAST ACROSS THE POTOMAC HIGHLANDS THIS EVENING...THEN
TOWARDS THE BALTIMORE METRO AFTER MIDNIGHT. ACCUMULATION FURTHER
EAST WOULD BE LESS THAN AN INCH AND WOULD NOT BE INCLUDED IN THE
ZONE WORDING.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
DP UPR TROF OVER APLCN MTS WILL BE IN PLACE FRI MRNG...WITH SNOW
EVENT XPCD TO BE ONGOING HIGH TERRAIN OF WRN ZONES. TOTAL
ACCUMULATIONS 4-6IN PSBL FOR UPSLP AREAS OVER 24 HRS. WILL RETAIN
WATCH ATTM...GIVEN LOW CONFIDENCE IN DVLPMT OF WRNG CRITERIA
CONDITIONS.
DRY SLOT FCST TO IMPACT SRN SECTIONS OF CWA...BUT PCPN MAY WRAP
AROUND CIRCULATION INTO NRN AND ERN ZONES. WITH COLD AIR IN
PLACE...ANY PCPN SHUD BE MIX OF RAIN AND SNOW...EVEN INTO METRO
AREAS BY FRI AFTN. NO SGFNT ACCUMULATIONS XPCD.
NWLY FLOW IN WAKE OF UPR TROF WILL CONT MSTR FETCH FROM GRTLKS
RGN...WITH PSBLTY OF LGT SNOW SHOWERS CONTG ON HIGHER TERRAIN FRI
EVE. BY EARLY SAT MRNG...SFC HIPRES BUILDS...WITH LGT LOW LVL
WINDS. DRY WX FCST THRU WKEND.
STG SHRTWV TROF DPNS ACRS N CNTRL CONUS SUN EVE...WITH SWLY FLOW
ALOFT OVER MID ATLC RGN. AS SYSTEM APRCHS...SFC CYCLOGENESIS OVER
GRTLKS RGN WILL INDUCE WARM ADVCTN PATTERN OVER MID ATLC. ALTHOUGH
MSTR RETURN WILL BE LMTD...SLY FLOW SHUD BE SUFFICIENT TO ERODE
LOW LVL COLD AIR SUCH THAT PCPN MON WILL BE LIQUID XCPT HIGH
TERRAIN.
TROF AXIS PASSES THRU TUE...DRIVING CDFNT THRU FCST AREA. WITH
COLD AIR ADVCTN TUE AFTN...MAXIMA MAY BE REACHED EARLY...AND LGT
SNOW SHUD SPREAD EWD THRU TUE. ACCUMULATING SNOW WILL BE PSBL IN
FAVORED UPSLP AREAS TO W...AS SUSTAINED NWLY LOW LVL FLOW XPCD IN
WAKE OF CDFNT.
HIPRES BUILDS AFTER DEPARTURE OF SYSTEM WED AFTN...WITH COOL TEMPS
FCST THRU REMAINDER OF NEXT WK.
&&
.AVIATION /09Z THURSDAY THROUGH MONDAY/...
SOLID MID CLOUD DECK TO STAY IN PLACE ACROSS MUCH OF THE AREA
THROUGH TODAY AND TONIGHT. SNOW SHOWERS WILL BEGIN OVER THE
MOUNTAINS LATER THIS MORNING...INTENSIFYING AND SPREADING EAST
OVERNIGHT. ADDED VICINITY SHOWERS AT KMRB FOR TONIGHT...BUT KEPT
EVERYWHERE ELSE DRY. WINDS WILL INCREASE BEHIND THE CLIPPER SYSTEM
TODAY...SO MAINTAINED A BRIEF PERIOD OF GUSTS OF 20 TO 25 KNOTS THIS
AFTERNOON.
INCRG CHC FOR PCPN...LOW CIGS AND VSBYS AS STG UPR TROF MOVES ACRS
RGN THRU FRI. SFC HIPRES AND IMPROVING CONDITIONS THIS WKEND...BFR
ANOTHER STG SYSTEM APRCHS SUN NGT AND MON. CONDITIONS WORSEN MON
THRU TUE ACRS TERMINALS AS RAIN AND SNOW DVLP WITH ARRIVAL AND
PASSAGE OF CDFNT TUE MRNG.
&&
.MARINE...
MARINE HEADLINES REMAIN IN PLACE FOR TODAY AND TONIGHT. WINDS
GRADUALLY PICK UP THROUGH THE MORNING...WITH GUSTS UP TO 25 KNOTS
POSSIBLE BY THE AFTERNOON. WINDS WILL BE SLOW TO DIMINISH OVERNIGHT
WITH LOW PRESSURE STRENGTHENING OFF THE EAST COAST.
SMALL CRAFT ADZY CONDITIONS TO CONT THRU FRI AS COLD AIR SPREADS
ATOP WARM WATERS AND UPR TROF AXIS MOVES THRU. SFC HIPRES BUILDS
THRU WKEND...WITH STG UPR SYSTEM TO APRCH MON. SLY LOW LVL FLOW
MON WITH INCRG CHC OF PCPN MON THRU TUE.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WINTER STORM WATCH FROM THIS EVENING THROUGH FRIDAY EVENING
FOR MDZ501.
VA...WINTER STORM WATCH FROM THIS EVENING THROUGH FRIDAY EVENING
FOR VAZ021.
WV...WINTER STORM WATCH FROM THIS EVENING THROUGH FRIDAY EVENING
FOR WVZ054-501-503.
MARINE...SMALL CRAFT ADVISORY FROM 9 AM THIS MORNING TO 7 PM EST FRIDAY
FOR ANZ530>537.
&&
$$
SAR/KRAMAR
