FXUS61 KLWX 091236
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
736 AM EST WED DEC 9 2009
.SYNOPSIS...
LOW PRESSURE WILL MOVE INTO THE GREAT LAKES AND SOUTHERN CANADA
TODAY. THE WARM FRONT ASSOCIATED WITH THIS LOW WILL REMAIN OVER THE
REGION THIS MORNING...BRINGING MORE RAIN. THE COLD FRONT ASSOCIATED
WITH THIS LOW WILL PASS THROUGH THIS AFTERNOON. HIGH PRESSURE WILL
BUILD IN BEHIND THE COLD FRONT TONIGHT THROUGH FRIDAY...BRINGING
DRY AND VERY COLD CONDITIONS. LOW PRESSURE MAY IMPACT THE REGION
DURING THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
QUICK UPDATE TO REMOVE FLOOD WATCH. THE HEAVIEST PRECIP CONTINUES
TO MOVE OFF TO THE EAST.
UPDATED TO REMOVE THE WINTER WEATHER HEADLINES AND ALSO TO REMOVE
THE FLOOD WATCH FOR LOCATIONS NORTH AND WEST OF THE INTERSTATE 95
CORRIDOR. PREV DISCUSSION FOLLOWS...
PCPN HAS CHGD PREDOMINANTLY TO RAIN THIS MRNG. HOWEVER...MESONET
OBS NOTED IN UPR 20S-LWR 30S AT HIGHER ELEVATIONS. ANY RMNG ICE
ACCRETION XPCD TO BE MINIMAL...BUT WILL CONT ADZY/WRNG THRU SLATED
EXPIRATION TIME OF 7 AM.
PCPN WILL CONT EARLY THIS MRNG...BUT DRY SLOT XPCD TO ARRIVE MID-
DAY AND DIVERT MAJORITY OF RAIN EWD. DRY AIR ALOFT WILL INCR
INSTBY AND MAY INVIGORATE A FEW SHALLOW TSTMS BY THIS AFTN...
MAINLY ACRS ERN SECTIONS WHERE COASTAL FRONT FIRMS.
ADDITIONAL CONCERN WILL BE IN SWRN SECTIONS. SWLY LLVL JET AT
H9-H85 WILL STRENGTHEN TO 50-60 KT THIS AFTN AMID DRY SLOT. WHILE
LLVL AMS SHUD RMN STABLE THRU MUCH OF TDA...STABLE LYR DECRS IN
DEPTH AS CLD CVR BREAKS. WIND GUSTS ABV 40 KT MAY IMPACT HIGHER
ELEVATIONS THIS AFTN AND EVE BFR JET DECRS IN MAGNITUDE. THUS...
WIND ADZY HAS BEEN ISSUED FOR SWRN ZONES 09/16Z - 10/03Z.
IN ADDITION...INSTBY INCRS ACRS WV AS COLD AIR ALOFT ARRIVES. LOW-
TOPPED CNVCTN PSBL HERE ALSO...WITH GUSTY /PSBLY AOA 50 KT/ WINDS AS
CNVCTN TRANSPORTS HIGH-MOMENTUM AIR TO SFC.
TEMPS WILL CLIMB ONLY SLGTLY THIS MRNG AS PCPN CONTS BUT ARE XPCD
TO INCR MARKEDLY AS DRY SLOT HELPS TO BREAK UP CLD CVR LATE THIS
MRNG.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
CDFNT ASSOCIATED WITH MODIFIED ARCTIC AMS MOVES THRU RGN LATE THIS
AFTN. GUSTY WINDS CONT THRU EARLY THIS EVE BFR TEMPS DROP
DRASTICALLY AND AIR DRIES. UPSLP SNOW PSBL TNGT ALONG WRN SLOPES
OF ALLEGHENY FRONT...BUT ACCUMULATIONS XPCD TO BE AROUND ONE INCH.
SHARPLY COLDER MINIMA AS SKIES CLR AND VERY COLD...DRY AIR ARRIVES.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
MODIFIED ARCTIC AMS ARRIVES THU IN WAKE OF TROF. DIFFERENCES EXIST
BTWN SHORTER RANGE MODELS IN STRENGTH OF COLD AIR. HAVE COOLED
MAXIMA THU AFTN BY A FEW DEG F OVER PREV FCST...HOWEVER IF GFS IS
CORRECT...THERE IS ROOM TO CONT COOLING TREND. COLD AIR RMNS IN
PLACE FRI. DRY WX AS HIPRES BUILDS.
MINIMAL CHGS MADE TO EXTENDED FCST ATTM. PSBLTY OF A BRIEF SNOW
SAT-SAT NGT AS A QUICK-MOVG SHRTWV TROF PASSES TO S AND
STRENGTHENS A COASTAL LOPRES SYSTEM. ANOTHER ARCTIC ORIGIN AMS
ARRIVES BY EARLY NEXT WEEK.
&&
.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
CONTD SUB-VFR CONDITIONS XPCD ALL TERMINALS THRU MID-MRNG. DRY
SLOT ARRIVES AND DIVERTS HEAVY PCPN EWD LATE THIS MRNG. SOME
BREAKS IN CLDS PSBL...BUT DRY AIR ALOFT MAY INVIGORATE A FEW
CNVCTV ELEMENTS BY THIS AFTN...MAINLY VCTY ERN TERMINALS. PRESSURE
GRADIENT INCRS AND MAY PROMOTE GUSTY WINDS AT ALL TERMINALS.
STRONG CDFNT MOVES THRU EARLY THIS EVE...WITH STRONG WLY WINDS
CONTG THRU TNGT. HIPRES BUILDS THU AND FRI.
SUB-VFR CIGS AND VSBYS PSBL SAT-SAT NGT AS A QUICK-MOVG SHRTWV
TROF COULD YIELD A BRIEF PERIOD OF RAIN OR SNOW. HIPRES BUILDS
AGAIN EARLY NEXT WEEK.
&&
.MARINE...
SMALL CRAFT ADZY CANCELLED THIS MRNG FOR UPR AND MIDDLE PORTIONS
OF TIDAL POTOMAC GIVEN CURRENT OBS. ONSET OF 20 KT GUSTS WAS
DELAYED UNTIL MID-DAY...WHEN DRY SLOT ARRIVES AND LIMITED MIXING
ENSUES.
LWR PORTIONS OF MD CHSPK BAY AND LWR TIDAL POTOMAC UPGRADED TO
GALE WRNG AS COASTAL FRONT XPCD TO BISECT THESE ZONES.
SMALL CRAFT ADZY CONTS...AND GALE WRNG SPREADS NWD...TNGT AS
STRONG CDFNT MOVES ACRS WATERS AND YIELDS WLY WINDS WITH GUSTS UP
TO 40 KT XPCD.
STRONG WINDS MAY CONT INTO THU...BUT ATTM DURATION AND STRENGTH OF
WINDS UNCERTAIN.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...WIND ADVISORY FROM 11 AM THIS MORNING TO 10 PM EST THIS
EVENING FOR VAZ021-025-026-036.
WV...WIND ADVISORY FROM 11 AM THIS MORNING TO 10 PM EST THIS
EVENING FOR WVZ054-501-502.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ532-
533-540-541.
GALE WARNING FROM 6 PM THIS EVENING TO 6 AM EST THURSDAY FOR
ANZ532-533-540-541.
SMALL CRAFT ADVISORY UNTIL 6 AM EST THURSDAY FOR ANZ530-531-
538-539-542.
GALE WARNING UNTIL 6 AM EST THURSDAY FOR ANZ534-537-543.
SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 6 AM EST
THURSDAY FOR ANZ535-536.
&&
$$
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