322
FXUS61 KLWX 020851
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
351 AM EST TUE DEC 2 2008
SYNOPSIS
AN UPPER TROUGH WILL MOVE ACROSS THE AREA TODAY. HIGH PRESSURE
AT THE SURFACE BUILDS IN TONIGHT AND WEDNESDAY. A COLD FRONT WILL
MOVE THROUGH ON THURSDAY...USHERING IN COLDER AIR FOR FRIDAY AND
THE WEEKEND.
NEAR TERM /UNTIL 6 PM THIS EVENING/
STILL HAVE SOME SNOW SHOWERS OCCURRING EARLY THIS MORNING IN FAVORED
UPSLOPE AREAS OF THE HIGHLANDS. HOWEVER...LOW LEVEL WINDS ARE
BECOMING LESS FAVORABLE AS THEY LOOK MORE SOUTHWEST THAN WEST OR
NORTHWEST. THIS WILL CUT DOWN ON ACTIVITY ACROSS THE ALLEGHENY
HIGHLANDS /ALLEGANY AND MINERAL COUNTIES/ WHERE LITTLE ADDITIONAL
ACCUMULATION WILL RESULT. WINTER WEATHER ADVISORY WILL BE CANCELLED
FOR THOSE COUNTIES. ACROSS WESTERN GRANT AND PENDLETON/HIGHLAND
COUNTIES...LIGHT ADDITIONAL ACCUMULATIONS WILL REMAIN POSSIBLE
BEFORE SNOW SHOWERS TAPER OFF LATER THIS MORNING. WILL CONTINUE THE
WINTER WEATHER ADVISORY FOR ANOTHER INCH OR SO OF SNOW...AND TOTAL
SNOWFALL ACCUMULATIONS OF 2 TO 4 INCHES FOR THE EVENT WHICH BEGAN
YESTERDAY.
OTHERWISE...LOCATIONS EAST OF THE MTNS ESPECIALLY NEAR INTERSTATE 95
MAY BEGIN WITH SUNSHINE. HOWEVER...MODELS SHOW AN UPPER LEVEL
TROUGH...EXTENDING SOUTH FROM THE EASTERN GREAT LAKES INTO THE OHIO
VALLEY EARLY THIS MORNING...SWINGING EAST ACROSS THE CWA TODAY. FLOW
IS NOT CONDUCIVE FOR ANY PRECIPITATION EAST OF THE MTNS...BUT MAY
SEE A SCT-BKN DECK MAKE IT EAST OF THE MTNS. THEREFORE...WILL
TRANSITION THE SKY TO PARTLY SUNNY.
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/
UPPER TROUGH AXIS WILL BE EAST OF THE CWA BY THIS EVENING. THIS WILL
PROMOTE CLEARING IN THE WAKE OF THE TROUGH. HIGH PRESSURE AT THE
SURFACE ALSO BUILDS INTO THE MID ATLANTIC. THEREFORE...EXPECT DECENT
RADIATIONAL COOLING OVERNIGHT...FAVORING THE COLDEST SET OF MOS FOR
MIN T /SREF ALSO COLDER/. THIS WILL LEAD TO LOW TEMPERATURES IN THE
20S ACROSS MOST AREAS /ACTUALLY PRETTY CLOSE TO AVERAGE FOR THIS
TIME OF YEAR/...WITH LOWER 30S IN THE URBAN CENTERS/NEAR THE BAY AND
SOME TEENS IN THE HIGHLANDS WITH A SNOWPACK.
LONG TERM /WEDNESDAY THROUGH MONDAY/
HIGH PRES WILL BEGIN TO MOVE OFFSHORE WED AFTERNOON. DESPITE FULL
SUNSHINE AND LIGHT SRLY FLOW I HAVE SCALED BACK IN TEMPS A FEW DEGS
DUE TO WEAK POTENTIAL FOR MIXING UNDER A STRONG SUBSIDENCE INVERSION.
SOME MODEST INCREASE IN MOISTURE EXPECTED LATE WED NIGHT AND THU
AHEAD OF ARCTIC FRONT THU. GUIDANCE DRYING THINGS OUT QUICKLY EAST
OF THE MTNS WITH JUST A PASSING SHOWER. HAVE ADJUSTED POPS MAINLY TO
THE MORNING HRS. TEMPS SHOULD CLIMB INTO THE 50S ESPECIALLY EAST OF
THE BLUE RIDGE WITH INCREASING DOWNSLOPE FLOW. BEST COLD ADVECTION
AND PRES RISES NOT UNTIL THE EVENING. AFTER SUNSET...TEMPS WILL
PLUMMET RAPIDLY UNDER GUSTY WNW WINDS OF UP TO 30 MPH. VERY COLD FRI
MORNING WITH LOW WIND CHILLS.
MODELS CONSISTENT WITH A CLIPPER SYSTEM AFFECTING THE REGION SAT
NIGHT AND SUN. MAIN QUESTION AS ALWAYS WITH THESE SYSTEMS IS AMOUNT
OF MOISTURE AVAILABLE WITH GFS MORE MOIST THAN EUROPEAN MODEL. EVEN
A LITTLE COATING COULD CAUSE SOME IMPACTS AS SFC TEMPS WILL BE
VERY COLD IN THE 20S LUCKILY IT IS GOING TO BE ON A WEEKEND AND
NOT DURING A WEEKDAY.
THINGS SETTLE DOWN FOR SUN NIGHT AND MON UNDER COLD HIGH PRES.
MODELS/ENSEMBLES SHOWING VARYING DEGREE OF AMPLIFICATION OF LARGE
SCALE FLOW OVER THE ERN HALF OF THE US. BOTH GFES/ECMWF INDICATE A
POTENTIAL SIG STORM NEXT WEEK. UNCERTAINTY IS HIGH HERE ESPECIALLY
IN TIMING. EARLY PRELIMINARY GUIDANCE FROM HPC (PREEPD) PREFERS THE
WEAKER/MORE PROGRESSIVE SOLUTION FROM THE GFS.
AVIATION /08Z TUESDAY THROUGH SATURDAY/
A TROUGH WILL SWING ACROSS THE TERMINALS THIS AFTERNOON...BUT WILL
ONLY BRING A VFR DECK OF CLOUDS /5-10K FT/. HIGH PRESSURE AT THE
SURFACE BUILDS IN TONIGHT.
IN THE OUTLOOK PERIOD...VFR CONDITIONS EXPECTED. GUSTY WNW WINDS
20-25KT THU INTO FRI THE MAIN CONCERN.
MARINE
WIND SENSORS CONTINUE TO INDICATE SMALL CRAFT ADVISORY WINDS
OCCURRING OVER THE MID BAY AND LOWER POTOMAC EARLY THIS MORNING.
THEREFORE...WILL EXTEND THE SMALL CRAFT ADVISORY IN TIME...WIDENING
THE GOAL POST TO ABOUT 14Z. UPPER TROUGH PASSAGE WILL KEEP WINDS
STIRRED UP IN THE 10 TO 15 KT RANGE THIS AFTERNOON BUT MODELS KEEP
THEM BELOW SMALL CRAFT ADVISORY CRITERIA.
SCA CONDITIONS POSSIBLE BEGINNING WED NIGHT BUT MORE LIKELY THU
INTO FRI.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...NONE.
VA...WINTER WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR
VAZ021.
WV...WINTER WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR
WVZ054-501.
MARINE...SMALL CRAFT ADVISORY UNTIL 9 AM EST THIS MORNING FOR
ANZ532>534-537.
SYNOPSIS...PELOQUIN
NEAR TERM...PELOQUIN
SHORT TERM...PELOQUIN
LONG TERM...LFR
AVIATION...PELOQUIN/LFR
MARINE...PELOQUIN/LFR
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