Area Forecast Discussion
Issued by NWS

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000 FXUS61 KPBZ 290804 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 359 AM EDT SAT AUG 29 2015 .SYNOPSIS... DRY CONDITIONS WILL HOLD TODAY AS TEMPERATURES INCREASE. RAIN CHANCES RETURN LATE TONIGHT AND SUNDAY WITH PASSAGE OF A WEAK COLD FRONT. && .NEAR TERM /THROUGH TONIGHT/...
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HIGH CLOUDS CONTINUE TO SKIRT OUR NORTHWESTERN ZONES...BUT SKIES HAVE REMAINED GENERALLY CLEAR AREA-WIDE. THIS AND THE VAST AMOUNT OF LOW TO MID-LEVEL DRY AIR HAS RESULTED IN TEMPERATURES TRENDING SHARPLY COOLER. TEMPERATURES OUTSIDE OF URBAN CORRIDORS AND MAINSTEM RIVER VALLEYS ALREADY PUSHING THE 50 DEGREE MARK. THE LOWER TEMPERATURES COMBINED WITH STEADY DEWPOINTS IN THE LOW TO MID 50S MEANS ANOTHER MORNING OF PATCHY FOG IS EXPECTED. HAVE INSERTED THE MENTION OF FOG IN THE PRE-DAWN HOURS...PRIMARILY HOLDING TO THE RIVER VALLEYS. TEMPERATURES SHOULD REBOUND FAIRLY QUICKLY TODAY AFTER SUNRISE AS THE LOW-LEVEL FLOW VEERS TO THE WEST-SOUTHWEST. UPPER-LEVEL TROF AXIS WILL APPROACH THE AREA THIS AFTERNOON/EVENING BUT COPIOUS DRY AIR AND WEAKENING DYNAMICS WILL KEEP THE BULK OF SATURDAY DRY. BY THE TIME THE WEAKENING FRONT REACHES THE AREA...CONDITIONS WILL BE UNFAVORABLE FOR CONTINUED CONVECTIVE GROWTH. HAVE MAINTAINED SLIGHT CHANCE/ISOLATED WORDING FOR POPS TONIGHT. TAX
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&& .SHORT TERM /SUNDAY THROUGH TUESDAY/...
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FRONT WILL SETTLE INTO THE FORECAST AREA ON SUNDAY. HOWEVER...WITH MIDLEVEL SUPPORT WEAKENING AND PULLING OFF TO THE EAST...AND SURFACE HIGH PRESSURE IN CONTROL...THE FRONT WILL STRETCH OUT AND LARGELY DISSIPATE. ENOUGH MOISTURE AND INSTABILITY WILL REMAIN FOR SCATTERED SHOWERS AND STORMS. COVERAGE WILL BE INFLUENCED BY DIURNAL FACTORS...WITH A PEAK DURING THE AFTERNOON HOURS. GOING TO KEEP POPS IN THE CHANCE RANGE DUE TO LACK OF LARGE-SCALE FORCING...WITH VALUES DROPPING TO SLIGHT CHANCE SUNDAY NIGHT. PRECIP TOTALS WILL LIKELY REMAIN UNDER A QUARTER INCH IN GENERAL...AND WILL NOT DO MUCH TO ALLEVIATE THE OVERALL DRY ANTECEDENT CONDITIONS. ON MONDAY...A DRIER AND MORE STABLE AIRMASS WILL TRY TO SINK INTO THE CWA...BUT WILL BE HINDERED BY WEAK MIDLEVEL ENERGY MOVING NORTHWARDS ACROSS THE CENTRAL APPALACHIANS. DO NOT THINK THAT THIS FAIRLY DIFFUSE VORTICITY WILL MAKE IT TO THE PITTSBURGH AREA...BUT THERE WILL BE ENOUGH SUPPORT FOR SOME ISOLATED SHRA/TSRA MAINLY SOUTH OF I-80. SO WILL MAINTAIN A SLIGHT CHANCE POP DURING THE DAY. LOSS OF HEATING PLUS STRETCHING/WEAKENING OF VORT ENERGY WILL ALLOW PRECIPITATION TO CEASE BY SUNSET. DRIER AIR MAKES A LITTLE MORE HEADWAY SOUTH ON TUESDAY...AND THINK ISOLATED DIURNAL CONVECTION WILL BE LIMITED TO SOUTH OF PIT. BLENDED MOSGUIDE WITH GOING FORECAST TO DERIVE TEMPERATURES. NOT MUCH CHANGE TO VALUES...WITH ABOVE NORMAL TEMPERATURES THROUGHOUT.
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&& .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
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H500 RIDGING PATTERN TAKES HOLD THROUGH THE EXTENDED PERIOD...WITH NO ORGANIZED WEATHER SYSTEMS FORESEEN THROUGH SATURDAY. APPEARS TO BE JUST ENOUGH MOISTURE FOR ISOLATED DIURNAL CONVECTION INTO FRIDAY AT LEAST...AND ELECTED TO ADD SLIGHT CHANCE POPS EACH DAY. HOWEVER...THE STRENGTH OF MID- LEVEL CAPPING WILL NEED TO BE EVALUATED AS TIME GOES ON TO DETERMINE THE DAILY PRECIP CHANCES...WITH FRIDAY AND SATURDAY PARTICULARLY NOTEWORTHY DRY CANDIDATES. MORE CERTAIN IS THE LIKELIHOOD OF CONTINUED ABOVE NORMAL TEMPERATURES...AND HPC GUIDANCE WAS USED IN COMBINATION WITH THE PREVIOUS FORECAST FOR THE VALUES.
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&& .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... QUICKLY FALLING TEMPERATURES AND STEADY DEWPOINTS WILL AGAIN COMBINE FOR PATCHY DENSE FOG CONDITIONS...MAINLY IN CLIMATOLOGICALLY FAVORABLE LOCATIONS. HAVE INCLUDED IFR FOG TEMPO GROUPS FOR BVI/HLG/ZZV/FKL/DUJ WITH THIS UPDATE. THE ONLY FLY IN THE OINTMENT AT THIS POINT IS WHETHER THE HIGH CLOUDS CAN INCREASE THROUGH THE PRE-DAWN HOURS AND HOLD OFF THE RADIATIONAL COOLING. OUTSIDE OF THE MORNING FOG CHANCES...THE AREA WILL REMAIN RESTRICTION FREE THROUGH THE REMAINDER OF THE TAF PERIOD. EXPECTING HIGH CLOUDS TO GIVE WAY TO DIURNAL CU DEVELOPMENT LATER THIS AFTERNOON. LIGHT SURFACE WINDS THIS MORNING WILL INCREASE TO 5-10KTS WHILE VEERING TO THE WEST-SOUTHWEST. TAX OUTLOOK...SATURDAY NIGHT THROUGH WEDNESDAY... BRIEF RESTRICTIONS IN SCATTERED CONVECTION SUNDAY AS A WEAKENING COLD FRONT CROSSES THE REGION. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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