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/...
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

&&

.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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