FXUS61 KLWX 101114
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
614 AM EST THU DEC 10 2009

.SYNOPSIS...
LOW PRESSURE WILL CONTINUE TO TRACK THROUGH QUEBEC TODAY WHILE HIGH  
PRESSURE APPROACHES FROM THE MIDWEST. HIGH PRESSURE WILL BUILD OVER 
THE REGION TONIGHT THROUGH FRIDAY NIGHT...BRINGING DRY AND COLD 
CONDITIONS. HIGH PRESSURE WILL MOVE OFF THE COAST SATURDAY...AND LOW
PRESSURE MAY IMPACT THE AREA SUNDAY INTO EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
UPDATE TO MARINE SECTION. GALE WARNING IS IN EFFECT FOR THE
CHESAPEAKE BAY FROM NORTH OF POOLES ISLAND TO NORTH BEACH.

LOW PRESSURE WILL CONTINUE TO TRACK THROUGH QUEBEC WHILE SURFACE 
HIGH PRESSURE BUILDS INTO THE MIDWEST AND TENNESSEE VALLEY. A
STRONG PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS WILL BRING
BLUSTERY CONDITIONS TODAY. MAX TEMPS LIKELY HAVE ALREADY OCCURRED
EARLY THIS MORNING...TEMPS WILL STAY STEADY OR FALL SLOWLY LATER
THIS MORNING THROUGH THIS AFTERNOON. HAVE REFLECTED THIS TREND IN
THE HOURLY TEMP GRIDS.

TEMPS THIS AFTERNOON WILL LIKELY BE IN THE MID AND UPPER 30S AROUND 
WASHINGTON AND BALTIMORE...BUT COLDER TO THE NORTH AND WEST. TEMPS 
ACROSS THE POTOMAC HIGHLANDS WILL HOLD IN THE TEENS. 

HAVE ISSUED A WIND ADVISORY FOR WESTERN GRANT...HIGHLAND...AND 
PENDLETON COUNTIES. CURRENT FEELING IS THAT COLD AIR WILL BANK UP 
AGAINST THE WESTERN SLOPES OF THE ALLEGHENY FRONT INCREASING THE 
PRESSURE GRADIENT ACROSS THESE AREAS. THIS WILL HELP TO MIX DOWN 
STRONGER WINDS FROM ALOFT. WILL KEEP THE MENTION OF 40 KNOT WIND 
GUSTS CONFINED TO ELEVATIONS ABOVE 3KFT. ELSEWHERE...WIND GUSTS 
AROUND 25 TO 30 KNOTS ARE ANTICIPATED.  

UPSLOPE SNOW SHOWERS WILL CONTINUE TO AFFECT THE WESTERN SLOPES OF 
THE ALLEGHENY FRONT THIS MORNING. WILL KEEP ACCUMULATIONS AROUND AN 
INCH OR LESS SINCE MOST OF THE MOISTURE WILL REMAIN OFF TO THE NORTH 
AND WEST. THIS IS DUE TO A LOW-LEVEL WESTERLY FLOW INSTEAD OF A 
NORTHWESTERLY FLOW. THE SUBSIDENCE INVERSION WILL CONTINUE TO LOWER 
THIS AFTERNOON WHILE DRIER AIR MOVES IN...BRINGING AN END TO THE 
SNOW SHOWERS BY THIS EVENING.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/...
HIGH PRESSURE WILL CONTINUE TO BUILD OVER THE TENNESSEE AND OHIO 
VALLEYS TONIGHT WHILE LOW PRESSURE REMAINS ACROSS EASTERN QUEBEC. 
WINDS WILL DIMINISH SOME TONIGHT...BUT THE PRESSURE GRADIENT BETWEEN 
THESE TWO SYSTEMS WILL REMAIN STRONG ENOUGH FOR BLUSTERY AND COLD 
CONDITIONS. 

THE ARCTIC AIR MASS ASSOCIATED WITH THIS HIGH HAS BEEN MODIFIED...
BUT IT EASILY WILL BRING THE COLDEST AIR MASS OF THE SEASON SO
FAR. TEMPS OVER THE OHIO VALLEY ARE IN THE TEENS AND LOWER 20S.
THIS AIR MASS WILL LIKELY BE OVER OUR CWA TONIGHT...WITH MIN TEMPS
DROPPING INTO THE TEENS AND 20S FOR MANY LOCATIONS DESPITE THE
WINDS HOLDING UP. SINGLE DIGIT TEMPS ARE EXPECTED ACROSS THE
HIGHER ELEVATIONS. THE COMBINATION OF BITTERLY COLD TEMPS AND
GUSTY WINDS OVER THE POTOMAC HIGHLANDS WILL RESULT IN MINIMUM WIND
CHILLS AROUND -10F. A WIND CHILL ADVISORY LIKELY WILL BE
WARRANTED FOR THIS AREA TONIGHT.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
VERY COLD...DRY AIR RMNS IN MID-ATLC RGN THRU SAT MRNG. HIPRES
MOVES OFF THE ATLC COAST SAT AS ZONAL FLOW HELPS INDUCE A RETURN
TO SLY LLVL FLOW.

A LOW-AMPLITUDE SHRTWV TROF EMBEDDED IN THE FLOW AIDS IN DVLPMT OF
COASTAL LOPRES NEAR CAROLINAS SAT EVE. PORTIONS OF FCST AREA XPCD
TO BE GRAZED BY A BRIEF ROUND OF SNOW SAT NGT...WHICH SHUD
TRANSITION TO RAIN ON SUN.

ANOTHER AMS OF ARCTIC ORIGIN WILL ARRIVE BY TUE...WITH SUSTAINED
UPSLP FLOW XPCD TO YIELD SNOW ALONG WRN SLOPES OF ALLEGHENY FRONT
DURG MID-WEEK.

&&

.AVIATION /11Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS EXPECTED THROUGH TONIGHT. WIND GUSTS 25 TO 30 KNOTS 
FROM THE WEST ARE ANTICIPATED TODAY. WINDS WILL DIMINISH SOME 
TONIGHT...BUT GUSTS AROUND 20 KNOTS ARE STILL POSSIBLE OVERNIGHT.

WINDS DECR FRI NGT AS HIPRES BUILDS. PCPN PSBL SAT NGT-SUN BFR
ARRIVAL OF ARCTIC ORIGIN AMS EARLY NEXT WEEK. GUSTY WINDS XPCD TUE
AND WED.

&&

.MARINE...
THE PRESSURE GRADIENT BETWEEN LOW PRESSURE OVER QUEBEC AND HIGH 
PRESSURE BUILDING OVER THE PLAINS AND MIDWEST WILL BRING GUSTY WINDS 
THROUGH TONIGHT. STRONG SCA WINDS ARE EXPECTED TODAY ACROSS THE
MIDDLE PORTION OF THE BAY AS WELL AS THE TIDAL POTOMAC WITH GUSTS
AROUND 30 KNOTS. A GALE WARNING IS IN EFFECT FOR THE CHESAPEAKE
BAY FROM NORTH OF POOLES ISLAND TO NORTH BEACH WHERE GUSTS AROUND
35 KNOTS ARE EXPECTED. WINDS WILL DIMINISH A LITTLE TONIGHT...BUT SCA
CONDITIONS ARE STILL EXPECTED ACROSS ALL OF THE WATERS.

SMALL CRAFT ADZY CONTS TMW. SUCH CONDITIONS MAY PERSIST INTO SAT
AND DVLP AGAIN MON.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR VAZ021.
WV...WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR WVZ054-501.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 PM EST FRIDAY 
     FOR ANZ530>532-538>540.
     GALE WARNING UNTIL 6 PM EST THIS EVENING FOR ANZ530>532-
     538>540.
     SMALL CRAFT ADVISORY UNTIL 6 PM EST FRIDAY FOR ANZ533>537-
     541>543.

&&

$$
LASORSA/KRAMAR