FXUS61 KPBZ 050713
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
213 AM EST SAT DEC 5 2009

.SYNOPSIS...
A STORM SYSTEM, MOVING UP THE EASTERN SEABOARD, WILL BRING LIGHT 
SNOW TO EASTERN AND SOUTHERN PORTIONS OF THE AREA. HIGH PRESSURE
WILL PROVIDE DRY WEATHER, BUT BELOW NORMAL TEMPERATURES, FOR THE
START OF THE NEW WEEK.

&&

.NEAR TERM /THROUGH TODAY/...
SFC LOW WILL MOVE ALONG THE EASTERN SEABOARD THIS MORNING AS UL
TROUGH DIGS INTO THE OHIO VALLEY. MOISTURE FROM THE SFC FEATURE
WILL SPREAD WESTWARD INTO TROUGH BRINGING SNOW TO PORTIONS OF THE
REGION. AIR CURRENTLY IN PLACE IS DRY SO IT WILL TAKE A BIT OF
TIME TO GET THE LOWER LEVELS MOISTENED ENOUGH TO ALLOW SNOW TO
REACH THE GROUND. APPEARS BEST AREA FOR ACCUMULATING SNOWS WILL BE
ALONG A BAROCLINIC ZONE THAT WILL STRETCH FROM THE MOUNTAINS OF
NORTHEASTERN WV TOWARD NORTHEASTERN PA. THIS AREA WILL CLIP MY FAR
SOUTHEASTERN COUNTIES SO WILL KEEP THE ADVISORY AS IS. AREA OF MID
LEVEL CONVERGENCE WILL ENHANCE THE SNOWFALL, ESPECIALLY ACROSS THE
HIGHER ELEVATIONS. APPEARS MOST OF THE SNOW WILL FALL BETWEEN 15Z
AND 21Z. EXPECT ACCUMULATIONS IN THE ADVISORY AREA GENERALLY IN
THE 2 TO 4 INCH RANGE WITH A LITTLE BIT MORE POSSIBLE ON THE RIDGE
TOPS. FURTHER WEST, THE SNOWFALL WILL COMPETE WITH A DRY
ATMOSPHERE AND SFC HIGH WHICH WILL MOVE INTO THE MIDWEST BY EARLY
AFTERNOON. THIS SETUP WILL PROVIDE A SHARP CUTOFF FOR THE SNOW AND
WILL LIMIT ANY ACCUMULATIONS. EXPECT GENERALLY LESS THAN AN INCH
ACROSS THE SOUTHEASTERN SECTOR OF CWA. SFC TEMPS JUST ABOVE THE
FREEZING MARK WILL ALSO HELP TO LIMIT ACCUMULATIONS.

TROUGH WILL SHIFT INTO W PA BY LATE AFTERNOON AND KICK SFC LOW
FURTHER EASTWARD. THIS WILL BRING A QUICK END TO THE SNOW FROM WEST
TO EAST.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...
EXPECT SNOW TO END IN ADVISORY AREA SHORTLY AFT 00Z. UL FLOW WILL
BECOME ZONAL AND SFC HIGH WILL MOVE INTO THE MID ATLANTIC. CAA
EXPECTED OVERNIGHT WITH DRIER AIR SHIFTING EASTWARD. MID LEVEL
WINDS REMAIN WESTERLY OVERNIGHT SO ANY LES SHOULD BE CONFINED TO
COUNTIES TO MY NORTH. 

SFC HIGH WILL PROVIDE A DRY BUT COLD DAY SUNDAY.

A WEAK COLD FRONT WILL PASS THROUGH THE AREA MONDAY. THIS WILL
BRING A CHANCE FOR RAIN/SNOW MONDAY. A BIT TOO EARLY TO DETERMINE
WHERE THE CHANGE OVER LINE WILL BE. MOISTURE IS LIMITED, SO DO NOT
EXPECT MUCH PRECIP WITH SYSTEM.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
LOW PRESSURE IS EXPECTED TO TRACK NORTHEAST THROUGH THE CENTRAL 
GREAT LAKES WEDNESDAY. TRACK AND CURRENT TIMING OF THE LOW ACROSS
OHIO AS DEPICTED BY OPERATIONAL GFS, GFS ENSEMBLES, AND ECMWF
WOULD MEAN AN INITIAL WINTRY PRECIPITATION MIX FOLLOWED BY A
CHANGE TO RAIN. THE SYSTEMS COLD FRONT WOULD THEN CHANGE THE RAIN
TO SNOW ON WEDNESDAY NIGHT WITH COLD NORTHWEST FLOW CONTINUING THE
CHANCE FOR SNOW SHOWERS FOR THURSDAY. WARM FRONT AHEAD OF AN
APPROACHING LOW MAY BRING THE POTENTIAL FOR MORE SNOW ON FRIDAY.

&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
BLEND OF RECENT SREF MODEL OUTPUT AND GFS LAMP SHOW BAND OF IFR 
SNOW FROM COASTAL LOW PRESSURE SYSTEM MOVING NORTHEASTWARD ACROSS 
THE MOUNTAINS OF WESTERN MARYLAND...NORTHERN WEST VIRGINIA AND 
SOUTHWESTERN PENNSYLVANIA TODAY.  TAF SITES KMGW AND KLBE CAN HAVE A 
PERIOD OF IFR SNOW 12Z-22Z. KAGC MAY ALSO HAVE A BRIEF IFR PERIOD OF 
SNOW 15Z-19Z. TAF SITES LIKE KHLG KPIT AND KDUJ CAN HAVE A PERIOD OF 
MVFR SNOW. 

NORTHWEST WINDS IN THE WAKE OF THE SYSTEM CAN BRING A PERIOD OF MVFR 
LAKE EFFECT STRATOCUMULUS TO KFKL AND KDUJ TONIGHT.

SURFACE WINDS TODAY ACROSS THE UPPER OHIO VALLEY WILL BE FROM THE 
NORTH 5-10 KTS AND BECOME NORTHWEST 5-10 KTS TONIGHT.  

HIGH PRESSURE COMING FROM THE MIDWEST WILL PROVIDE VFR ACROSS THE 
UPPER OHIO VALLEY TONIGHT INTO EARLY MONDAY. THEN A LOW PRESSURE 
SYSTEM MOVING EASTWARD THROUGH THE GREAT LAKES CAN PROVIDE A PERIOD 
OF MVFR RAIN AND SNOW SHOWERS LATE MONDAY INTO TUESDAY. A STRONG LOW 
PRESSURE SYSTEM COMING FROM OKLAHOMA CAN BRING IFR SNOW AND RAIN TO 
THE UPPER OHIO VALLEY WEDNESDAY.
 

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER WEATHER ADVISORY FROM 6 AM THIS MORNING TO 6 PM EST 
     THIS EVENING FOR MDZ001.
OH...NONE.
PA...NONE.
WV...WINTER WEATHER ADVISORY FROM 6 AM THIS MORNING TO 6 PM EST 
     THIS EVENING FOR WVZ041.

&&

$$