FXUS61 KPBZ 251510
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1010 AM EST FRI DEC 25 2009

.SYNOPSIS...
A STRONG LOW PRESSURE SYSTEM, MOVING NORTHWARD THROUGH THE MIDWEST,
WILL PUSH FREEZING RAIN AND RAIN INTO THE AREA THIS CHRISTMAS DAY.
COLDER AIR WILL MOVE IN FOR THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
PRECIPITATION CONTINUES TO SPREAD NORTHEASTWARD ACROSS THE REGION
WITH TEMPERATURES REMAINING AT OR BELOW FREEZING MAINLY NORTH OF
PIITSBURGH AND ALONG THE RIDGES. A WINTER STORM WARNING CONTINUES
FOR GARRETT COUNTY MD...PRESTON AND TUCKER COUNTIES IN WV AND
WESTMORELAND AND FAYETTE COUNTIES IN PA...WHERE ICE ACCRETION
SHOULD EXCEED A QUARTER OF AN INCH. WINTER WEATHER ADVISORIES
REMAIN IN EFFECT FOR MUCH OF WESTERN PA...BUT WILL BE CANCELLED
SHORTLY FOR PARTS OF EAST CENTRAL OH AND NORTHERN PANHANDLE OF
WV...WHERE TEMPERATURES HAVE WARMED ABOVE FREEZING.

WIND ADVISORIES REMAIN IN EFFECT FOR THE RIDGES TODAY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
JUDGING FROM RECENT SREF MODEL OUTPUT...EXPECT THE COLD FRONT TO
MOVE THROUGH TONIGHT. THE RESULTING COOL DOWN WILL CHANGE
PRECIPITATION TO ALL SNOW BY LATE SATURDAY NIGHT. THE PROBLEM WITH
PRECIP TONIGHT IS THE LACK OF MID AND UL MOISTURE WHICH WILL NOT
ALLOW FOR ICE TO DROP INTO THE LOWER LEVELS...THUS PREVENTING AN
ATMOSPHERE CONDUCIVE TO SNOW MAKING. HAVE PUT IN A MENTION OF
FREEZING DRIZZLE LATE TONIGHT. THIS WILL HAVE TO BE LOOKED AT MORE
CLOSELY ON A LATER PACKAGE.

FORECASTED TEMPERATURES USING A BLEND OF RECENT SREF MODEL OUTPUT
AND GFS MOS.

WITH UL REMAINING WEST OF THE AREA THIS WEEKEND EXPECT A BREAK IN
PRECIP SATURDAY AND THROUGH THE FIRST HALF OF SUNDAY.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
UPPER LEVEL LOW OVER THE LOWER GREAT LAKES WILL MOVE INTO NEW 
ENGLAND BY TUESDAY. PERSISTENT LOW LEVEL NORTHWEST FLOW AND COLD AIR 
INSTABILITY WILL CONTINUE TO GENERATE SCATTERED SNOW SHOWERS THROUGH 
EARLY TUESDAY. 

SURFACE HIGH PRESSURE WILL BUILD INTO THE REGION LATE TUESDAY AND 
WEDNESDAY BRINGING DRY WEATHER. A LOW PRESSURE SYSTEM OVER THE 
SOUTHEASTERN STATES WILL BRING MOISTURE AND A CHANCE OF SNOW SHOWERS 
TO THE NORTHERN WEST VIRGINIA/WESTERN MARYLAND MOUNTAINS THURSDAY. 

CLOUD COVER WILL HOLD DAYTIME TEMPERATURES DOWN TO FEW DEGREES BELOW 
NORMAL THROUGH THE EXTENDED PERIOD.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
A POTENT LOW PRESSURE SYSTEM WILL LIFT NORTHWARD ACROSS THE MISSOURI 
VALLEY...WITH AN OCCLUDED FRONT CROSSING THE AREA LATE TODAY AND 
TONIGHT. INITIAL PRECIP IS CROSSING EASTERN OHIO INTO FAR SOUTHWEST
PA...AND WILL CONTINUE TO WORK NORTH ACROSS THE REGION...WITH PRECIP 
JUST BEGINNING AT MGW/HLG/PIT/AGC...AND SHOULD BEGIN AT LBE/BVI IN 
THE NEXT HOUR OR SO...MOVING NORTH TO FKL/DUJ BY 15Z. PRECIP WILL BE 
LIQUID FROM A HLG/MGW LINE SOUTH AND WEST. FURTHER 
NORTH...TEMPERATURES ARE HOVERING AROUND FREEZING...AND WITH WET 
BULB EFFECTS...SOME BRIEF FZRA IS PSBL FOR BVI/PIT/AGC/LBE AT ONSET 
FOR AN HOUR OR TWO BEFORE CHANGING TO RAIN. FOR FKL/DUJ...COLDER AIR 
WILL HANG ON LONGER...SO WILL USE FZRA FOR 3-4 HOURS...CHANGING TO 
RAIN THIS AFTN. WINDS ALOFT WILL INCREASE TO 50-60KT AT 2000 FT...SO 
WILL USE LOW LEVEL WIND SHEAR FOR ALL PORTS THROUGH THIS EVENING. SE 
SURFACE WINDS OF 10-15 KT WILL PREVAIL FOR THE EARLY 
MORNING...INCREASING TO 15-20KT WITH GUSTS TO 30-35 KT THIS 
AFTN...WITH THE HIGHEST GUSTS AT LBE IN SOUTHEAST DOWNSLOPE FLOW. 
MVFR/AREAS OF IFR WILL PREVAIL WITH THE PRECIP TODAY INTO THIS 
EVENING...WITH LOWER CLOUDS PERSISTING THROUGH FRIDAY. WITH JUST 
MAINLY LOWER CLOUDS TNGT/EARLY SATURDAY...THINK MOST OF THE PRECIP 
WILL BE LIGHT SNOW SHOWERS AND DRIZZLE/FREEZING DRIZZLE OVERNIGHT.

FOR SATURDAY...THINK MOST AREAS WILL REMAIN DRY AS THE REGION WILL
BE IN THE DRY SLOT BETWEEN THE SURFACE FRONT TO THE EAST...AND
THE PARENT UPPER LOW ACROSS THE MIDWEST. HOWEVER...MAINLY MVFR
CIGS WILL REMAIN. FOR SUNDAY/MONDAY...THE UPPER LOW WILL EJECT
EAST ACROSS THE AREA...WITH SNOW SHOWERS/RESTRICTIONS. CONDITIONS
MAY IMPROVE TUESDAY AS THE LOW IS PROGGED TO EJECT EAST INTO
THE CANADIAN MARITIMES.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WIND ADVISORY UNTIL 8 PM EST THIS EVENING FOR MDZ001.
     WINTER STORM WARNING UNTIL 1 PM EST THIS AFTERNOON FOR MDZ001.
OH...NONE.
PA...WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR 
     PAZ008-009-015-016-023.
     WIND ADVISORY UNTIL 8 PM EST THIS EVENING FOR PAZ030-032.
     WINTER STORM WARNING UNTIL 1 PM EST THIS AFTERNOON FOR PAZ030-
     032.
     WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR PAZ007-013-
     014-020>022.
WV...WIND ADVISORY UNTIL 8 PM EST THIS EVENING FOR WVZ023-041.
     WINTER STORM WARNING UNTIL 1 PM EST THIS AFTERNOON FOR WVZ023-
     041.

&&

$$