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-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --000 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/...-- Changed Discussion --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.-- End Changed Discussion --&& .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/...-- Changed Discussion --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.-- End Changed Discussion --&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$
