Area Forecast Discussion
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000
FXUS61 KPBZ 201444
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1044 AM EDT WED AUG 20 2014

.SYNOPSIS...
OCCASIONAL SHOWERS AND THUNDERSTORMS CAN BE EXPECTED THROUGH THE
WEEKEND AS A SERIES OF DISTURBANCES MOVE THROUGH THE REGION.

&&

.NEAR TERM /THROUGH TONIGHT/...
FLOODING ISSUES CONTINUE ACROSS THE WARNED AREAS DESPITE BATCH OF
HEAVY RAIN HAS FINISHED AND MOVED EAST. RECENT SATELLITE IMAGERY TRENDS
DISPLAY DRY AIR ALOFT MOVING ACROSS THE OHIO VALLEY BEHIND THE
PASSING SHORTWAVE. DESTABILIZATION IS EXPECTED THIS
AFTERNOON...ESPECIALLY WHERE CLEARING OCCURS...WITH HIGH SURFACE
MOISTURE IN PLACE. UPPER LEVEL SHORTWAVE ASSOCIATED WITH SLOW
MOVING UPPER LOW OVER THE GREAT LAKES IS EXPECTED TO HELP INITIATE
CONVECTION IN THE AFTERNOON. THUS...CHANCE TO LIKELY POPS ARE
FORECASTED FOR AREAS WHERE SURFACE BOUNDARY IS DRAPED ACROSS.
CONVECTION IS THEN EXPECTED TO DECREASE THIS EVENING WITH THE LOSS
OF HEATING AND DISPLACEMENT OF THE SHORTWAVE.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
A RELATIVELY STATIONARY BOUNDARY STRETCHING SOUTH FROM A WEAK SFC
LOW WILL REMAIN IN THE AREA THURS THROUGH FRI WITH SEVERAL
DISTURBANCES PROGGED TO TRAVERSE ALONG IT. SHOWERS AND THUNDERSTORMS
SHOULD QUICKLY DEVELOP THURS AS THE BOUNDARY LAYER DESTABILIZES
AROUND MIDDAY. WHILE THE BEST INSTABILITY AND SHEAR APPEAR TO STAY
SOUTH OF THE BOUNDARY THURS...OVER SRN OH...WHERE SPC HAS INCLUDED
A SEE TEXT PORTION OF THE DAY TWO OUTLOOK. MEANWHILE...THE 00Z NAM
SHOWS AROUND 1500J/KG SFC CAPE AND 30-40KTS 0-6KM BULK SHEAR IN OUR
AREA. THE CORE OF THE H5 JET REMAINS OVER SWRN OH. COULD EXPECT A
FEW STRONG TO SEVERE THUNDERSTORMS THURS AFTERNOON/EVENING.

EXPECTING TO SEE A DIURNAL LULL LATER THURS INTO EARLY FRI...BUT
WITH ENOUGH MOISTURE PRESENT ALONG THE BOUNDARY...SHOWER CHANCES
WILL EXIST...MAINLY INTO ERN OH. FRIDAY AS THE UPPER RIDGE TRIES TO
BUILD OVER THE MS VALLEY...A SFC LOW LIFTS THE BOUNDARY NORTH AS A
WARM FRONT SERVING AS A FOCUS FOR ADDITIONAL SHOWERS AND
THUNDERSTORMS. A WAVE AT H7 WILL MOVE ALONG THE BOUNDARY AGAIN
FRI...BUT TIMING DIFFERENCES EXIST AMONG THE MODEL GUIDANCE. AT THIS
POINT WILL CONTINUE TO CARRY HIGH CHC POPS FOCUSED ON THE EARLY
EVENING TIMING OF THE 00Z NAM/ECMWF. PWAT VALUES MAX OUT AROUND 2"
FRIDAY THROUGH ERN OH AND NRN WV ALONG THE CORRIDOR WHERE SHOWERS
AND THUNDERSTORMS ARE EXPECTED. STORM MOTIONS FROM THE 00Z NAM
BUFR SOUNDINGS ARE IN THE 20-30KT RANGE...BUT SHOWERS SHOULD BE
HIGHLY EFFICIENT AND ANY TRAINING COULD LEAD TO WATER PROBLEMS
THROUGH FRI NIGHT.
TAX

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
WITH ACTIVE WEATHER IN THE NEAR TERM...GENERALLY STAYED CLOSE TO THE
PREVIOUS FORECAST BLENDING WITH WPC THINKING FOR THE EXTENDED
PERIOD. MODELS CONTINUE TO SHOW A RIDGE BUILDING IN THE SRN
PLAINS THROUGH THE WEEKEND...SLOWLY SHIFTING THE AXIS INTO OUR
REGION BY EARLY NEXT WEEK. THE WEEKEND WILL REMAIN WARM AND MUGGY
WITH DAILY RAIN CHANCES AS WE SIT ON THE ERN PERIPHERY OF THE RIDGE.
A GRADUAL EASTWARD SHIFT IN THE UPPER TROF AXIS WOULD MEAN A
CONTINUATION OF AT LEAST NEAR NORMAL TEMPS THROUGH MIDDLE OF NEXT
WEEK WITH A DRYING TREND.
TAX

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
SHOWERS AND EMBEDDED THUNDERSTORMS HAVE CONGEALED INTO A RAGGED
MCS THIS MORNING. MAIN LINE OF THUNDER IS HEADING THROUGH EASTERN
OHIO CURRENTLY...AND HAVE TRIED TO TIME TEMPO IFR VSBYS THROUGH
HLG/PIT/AGC/BVI OVER THE NEXT COUPLE OF HOURS. THINK THE LINE WEAKENS
BEFORE IT IMPACTS TERMINALS TO THE EAST.

A RELATIVE LULL WILL BE SEEN LATER THIS MORNING...WITH MOST
LOCATIONS POSSIBLY ACHIEVING VFR. INSTABILITY SHRA/TSRA ARE THEN
EXPECTED THIS AFTERNOON ASSUMING WE GET A BIT OF SUN. MAINTAINING
VCTS FOR NOW AS AM STILL UNCERTAIN ON TIMING AND AREAS OF HIGHEST
PROBABILITY.  ACTIVITY SHOULD START TO WEAKEN AFTER SUNSET.

THINK CLOUDS BREAKUP SOMEWHAT AS WE WILL LIKELY BE IN BETWEEN
DISTURBANCES. HAVE MVFR FOG MENTIONED AT MOST SITES OVERNIGHT...AND
THIS MAY BE OPTIMISTIC AT A FEW.

OUTLOOK.../WEDNESDAY NIGHT THROUGH SUNDAY/...
SEVERAL CROSSING DISTURBANCES WILL CAUSE PERIODIC RESTRICTIONS
INTO THE WEEKEND.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.

&&

$$






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