Area Forecast Discussion
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000 FXUS61 KPBZ 280230 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 1030 PM EDT WED MAY 27 2015 .SYNOPSIS... WARM TEMPERATURES AND PERIODIC SHOWER AND THUNDERSTORM CHANCES ARE EXPECTED THROUGH THE REST OF THE WEEK. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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A WEAK VORT WILL RIDE NORTHEASTWARD IN DEEP SOUTHWESTERLY FLOW AHEAD OF THE MAIN SHORT WAVE TROUGH OVER THE CENTRAL GREAT LAKES THIS EVENING. THIS COMBINED WITH UPPER DIVERGENCE FROM THE RIGHT ENTRANCE REGION OF A NEARBY UPPER JET STREAK WILL ALLOW FOR SOME DEGREE OF LARGE SCALE ASCENT ALONG AN AXIS OF HIGH VERTICAL WIND SHEAR THAT EXTENDS FROM SOUTHWESTERN OHIO INTO NORTHWESTERN PENNSYLVANIA. ALONG AND AHEAD OF THIS AXIS...CAPE VALUES HAVE SURGED TOWARD 700-1200 J/KG ACROSS OUR AREA...AND MODEL PROJECTIONS INDICATE 0-6 KM BULK SHEAR WILL APPROACH 45 KTS ALONG AND NORTH OF I-80 THROUGH THE EVENING. RATHER BURLY DCAPE VALUES ARE ALSO PRESENT AHEAD OF ONGOING CONVECTOIN ACROSS NORTHERN OHIO AT THE MOMENT...SO A WIND THREAT SEEMS TO BE THE LARGEST CONCERN GOING INTO THE NEXT SEVERAL HOURS. HOWEVER...ONGOING CONVECTION HAS LARGELY ALREADY GUST OUT...WITH A QUITE DISCERNIBLE OUTFLOW BOUNDARY EVIDENT ON KPBZ WSR-88D...SO THE WIND THREAT WILL BE GENERALLY CONFINED NORTH OF PITTSBURGH...AND ANY SEVERE WIND IS EXTREMELY UNLIKELY AT THIS POINT. THE SURFACE BOUNDARY WILL FOLLOW THIS ACTIVITY THROUGH THE AREA OVERNIGHT TONIGHT MORNING. THIS WILL BRING PROGRESSIVELY DRIER AIR IN FROM THE NORTH AS SURFACE FLOW TURNS NORTHERLY. HOWEVER...LARGE SCALE FORCING FOR THE FRONTAL BOUNDARY WILL BE PEELING TO THE NORTHEAST...AND THE SURFACE HIGH BEHIND THE FRONT FAILS TO BUILD SOUTHEASTWARD. THIS WILL LIKELY LEAD TO THE FRONT NOT CLEARING THE ENTIRETY OF THE SOUTHERN PORTION OF THE AREA BY MORNING OR EVEN INTO THE DAYTIME ON THURSDAY. FRIES
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... RIDGING IS PROGGED TO GRADUALLY BUILD IN THURSDAY...THOUGH A FEW SHOWERS/STORMS COULD LINGER INTO EARLY AFTERNOON ACROSS THE WV/MD RIDGES AS THE SOUTHERN PORTION OF THE WEAKENING SURFACE BOUNDARY CROSSES. MODEL PROGS HAVE SHIFTED THE RIDGE AXIS FURTHER EAST FOR FRIDAY...RESULTING IN A QUICKER RETURN TO SOUTHWEST FLOW WITH A WEAK EMBEDDED CROSSING SHORTWAVE. INCLUDED CHANCE POPS FOR AFTERNOON SHOWERS/STORMS. MOIST SOUTHWEST FLOW IS EXPECTED TO CONTINUE THROUGH SATURDAY AS A COLD FRONT ADVANCES ACROSS THE GREAT LAKES REGION...BRINGING INCREASING POPS THROUGH THE DAY. TEMPERATURES ARE EXPECTED TO CONTINUE AROUND 10 DEGREES ABOVE SEASONAL LEVELS USING THE LATEST GRIDDED MOS AND SREF NUMBERS. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... CHANGES TO THE EXTENDED FORECAST WERE TO TEMPERATURES AND POPS MAINLY INTO MONDAY TO BE IN BETTER COORDINATION WITH SURROUNDING OFFICES AND NEW WPC PROGS. COLD FRONT WILL CROSS REGION AND STALL ACROSS THE CENTRAL APPALACHIANS SUNDAY NIGHT. LIKELY POPS ACROSS THE REGION SATURDAY NIGHT DIMINISHING WEST TO EAST DURING THE DAY SUNDAY. TEMPERATURES WERE LOWERED WITH FROPA AND COOL HIGH PRESSING NOSING SOUTH FROM THE GREAT LAKES INTO MONDAY. HOW FAST STALLED BOUNDARY SHIFTS NORTH AS A WARM FRONT MAIN PROBLEM INTO MID WEEK. FOR NOW STAYED CLOSE TO WPC PROGS...WITH LITTLE CHANGE FROM PREVIOUS FORECAST. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... SUPPORT FOR SHOWERS AND STORMS REMAINS STRONGEST TO THE NW OF ALL OUR SITES. THIS WILL CONTINUE FOR A FEW MORE HOURS BEFORE REMNANT ACTIVITY SAGS SOUTHEASTWARD WITH A WEAK FRONT. THIS WILL BRING DYING SHOWERS AND AN ISOLATED THUNDERSTORM ACROSS THE SITES OVERNIGHT. WINDS WILL SLOWLY TURN WESTERLY THEN NORTHERLY BY THURSDAY AS DRIER AIR WORKS IN...HOWEVER BEFORE IT DOES...SOME RESTRICTIONS ARE LIKELY WHERE IT DOES RAIN. THE FRONT WILL HAVE DIFFICULTY CLEARING THE KMGW AND KZZV BEFORE SURFACE HIGH PRESSURE MOVES EAST TO THE NORTH OF THE AREA...ALLOWING FOR A RESUMPTION IN SOUTHERLY FLOW BY NEAR THE END OF THE FORECAST PERIOD. FRIES .OUTLOOK.../THURSDAY NIGHT MONDAY/... RESTRICTIONS POSSIBLE IN SCT THUNDERSTORMS FRIDAY...WITH MORE WIDESPREAD RESTRICTIONS EXPECTED SATURDAY INTO SUNDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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