857
FXUS61 KPBZ 230253
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
953 PM EST SUN NOV 22 2009
SYNOPSIS
LOW PRESSURE MOVING FROM LOUISIANA TONIGHT TO THE VIRGINIA COAST
MONDAY NIGHT MAY SPREAD SHOWERS AS FAR WEST AS THE UPPER OHIO
VALLEY MONDAY AND MONDAY NIGHT. A LOW PRESSURE SYSTEM COMING FROM
THE CANADIAN ROCKIES WILL STRENGTHEN WHEN IT MOVES THROUGH THE
GREAT LAKES WEDNESDAY AND THANKSGIVING DAY TO GIVE THE UPPER OHIO
VALLEY COLDER TEMPERATURES AND RAIN AND SNOW SHOWERS INTO THE
WEEKEND.
NEAR TERM /THROUGH MONDAY/
AS LOW PRESSURE SYSTEM FROM LOUISIANA HEADS TOWARD THE VIRGINIA
COAST...CLOUDS WILL INCREASE EAST TO WEST ACROSS THE UPPER OHIO
VALLEY LATE TONIGHT AND MONDAY.
AS CONTINUED TO BE SHOWN BY SREF MODEL OUTPUT...THERE IS A CHANCE
THAT SHOWERS FROM THE COASTAL SYSTEM COULD SPREAD WESTWARD ACROSS
THE UPPER OHIO VALLEY MONDAY.
FORECASTED CONTINUED MILD TEMPERATURES THIS PERIOD USING A BLEND
OF CLOSELY CONCURRING GFS AND NAM MOS VALUES.
SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/
SEVERAL SREF MODEL MEMBERS INCLUDING OPERATIONAL NAM MODEL OUTPUT CONTINUE
TO SHOW SHOWERS FROM THE COASTAL SYSTEM BRINGING SHOWERS TO THE
UPPER OHIO VALLEY MONDAY NIGHT INTO TUESDAY. HOWEVER OPERATIONAL
GFS AND ECMWF MODEL OUTPUT SHOW NO RAIN FOR THE AREA. OUR CURRENT
SOLUTION WAS TO KEEP MENTION OF A CHANCE OF SHOWERS MONDAY NIGHT FOR
MOST AREAS...BUT FOR ONLY LOCATIONS NEAR THE MOUNTAINS DAYTIME
TUESDAY.
BASED ON RECENT BLEND OF SREF AND GEFS MODEL OUTPUT...EXPECT THE
FIRST SHOWERS WITH THE INCOMING WESTERN SYSTEM TO BEGIN TO SPREAD
ACROSS THE UPPER OHIO VALLEY TUESDAY NIGHT AND WEDNESDAY.
FOR TEMPERATURES...PREFERRED SLIGHTLY MILDER GFS MOS VALUES THIS
PERIOD.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
LITTLE CHANGE IN THE EXTENDED FORECAST COMPARED TO YESTERDAY. UPPER
LEVEL LOW WILL SLOWLY MOVE FROM THE CENTRAL PLAINS WEDNESDAY NIGHT
TO NEW ENGLAND FRIDAY NIGHT. EXPECTED SCATTERED SHOWERS TO PERSIST
THROUGH MUCH OF THIS TIME PERIOD. TEMPERATURES WILL DROP TO NEAR OR
SLIGHTLY BELOW FREEZING THURSDAY AND FRIDAY NIGHTS...BUT WITH THESE
BEING THE FIRST TWO NIGHTS IN SOME TIME WITH BELOW FREEZING
TEMPERATURES...AT THIS POINT DO NOT THINK THERE WOULD BE ANY
ACCUMULATING SNOW.
MODELS HAVE SURFACE LOW PRESSURE DEVELOPING OFF THE NEW ENGLAND
COAST FRIDAY NIGHT...BUT THIS SYSTEM SHOULD BE TOO FAR TO THE EAST
TO AFFECT LOCAL WEATHER. AS THE UPPER LOW MOVES TO THE EAST FRIDAY
NIGHT...NORTHWEST FLOW SHOULD ALLOW FOR THE DEVELOPMENT OF SOME
LAKE EFFECT SHOWERS INTO SATURDAY. CONDITIONS SHOULD DRY OUT
SATURDAY NIGHT AS HIGH PRESSURE MOVES IN FROM THE SOUTHWEST.
TEMPERATURES WILL BE BELOW NORMAL THROUGH THIS TIME PERIOD.
AVIATION /03Z MONDAY THROUGH FRIDAY/
WINDS WILL DECREASE A FEW KNOTS OVERNIGHT...BUT REMAIN STEADY OUT
OF THE EAST AROUND 5 KTS OVERNIGHT. EXPECT CIRRUS SHIELD TO MOVE
IN OVERNIGHT FROM THE SOUTH WITH A DEVELOPING LOW PRESSURE SYSTEM
OFF THE SOUTHEAST COAST.
THE LOW MOVING UP THE EAST COAST ON MONDAY WILL BRING THE NEXT
CHANCE FOR SHOWERS WITH REDUCED CEILINGS EXPECTED...ESPECIALLY
SOUTHEAST OF A KMGW-KLBE LINE. FOR NOW...WILL JUST KEEP LOW VFR
CEILINGS AT MOST SITES.
A LOW PRESSURE SYSTEM ACROSS THE MISSOURI VALLEY WILL DEVELOP ON
TUESDAY...STRENGTHENING AS IT MOVES INTO THE GREAT LAKES BY
WEDNESDAY. THIS SYSTEM AND ITS ASSOCIATED COLD FRONT WILL RETURN
THE CHANCE FOR REDUCED CEILINGS ACROSS THE AREA FOR THE REST OF
THE WEEK.
PBZ WATCHES/WARNINGS/ADVISORIES
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
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