Area Forecast Discussion
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000 FXUS61 KPBZ 210142 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 942 PM EDT SAT SEP 20 2014 .SYNOPSIS... A COLD FRONT WILL BRING SHOWERS AND THUNDERSTORMS ON SUNDAY. HIGH PRESSURE WILL DOMINATE THE REMAINDER OF THE WEEK WITH DRY WEATHER. && .NEAR TERM /THROUGH SUNDAY/... EVENING UPDATE...MADE ADJUSTMENTS TO POPS OVER THE NEXT SEVERAL HOURS AS SHOWERS APPROACH FROM OHIO SUPPORTED BY A SHORTWAVE ALOFT. PREVIOUS DISCUSSION FOLLOWS... STABLE CONDITIONS EARLY TONIGHT WILL WANE AS HIGH PRESSURE MOVES OFF THE EAST COAST. INCREASING LOW LEVEL MOISTURE WITH THE SUPPORT OF A WEAK UPPER WAVE WILL PROVIDE CLOUD DEVELOPMENT OVERNIGHT. SUFFICIENT FORCING FOR PRECIPITATION REMAINS FURTHER WEST...THUS LOW POPS WERE MAINTAINED LATE TONIGHT. BROAD UPPER LEVEL TROUGH APPROACHING FROM THE UPPER MIDWEST IS EXPECTED TO DEEPEN BY SUNDAY. INSUFFICIENT CAPE DUE TO EXTENSIVE CLOUD COVER...LIMITED DAYTIME HEATING...AND POOR MID LEVEL LAPS RATES WILL OVERALL LIMIT THE COVERAGE AND LONGEVITY OF THUNDERSTORMS. HOWEVER...THE POTENTIAL STILL EXISTS FOR LOW TOPPED THUNDERSTORMS AS LOW LEVEL MOISTURE REMAINS ABUNDANT WHILE LOW LEVEL LAPS RATES STEEPEN AHEAD AND ALONG OF THE SURFACE COLD FRONT. DUE TO THE RELATIVELY DRY AIR ALOFT AND STRONG SHEAR...SHOWERS WITH STRONG WIND GUSTS CAN BE EXPECTED ON SUNDAY. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... UPPER LEVEL TROUGH AXIS IS PREDICTED TO CROSS THE AREA SUNDAY NIGHT. IN THE WAKE OF THE COLD FRONT...A STRONG INVERSION WILL SET UP AS NORTHWEST FLOW DEVELOPS AND THEREFORE LAKE AND TERRAIN ENHANCED SHOWERS/CLOUDS WILL PURSUE EARLY MONDAY MORNING MAINLY NORTH OF I-76...BUT SINCE THE INVERSION LOWERS AND REMAINS SHALLOW...STRATOCU DECK WILL LIKELY SUPERSEDE SHOWERS MUCH OF MONDAY. SURFACE HIGH PRESSURE BUILDS MONDAY NIGHT BRINGING DRIER CONDITIONS TO HELP WEAKEN THE INVERSION. TEMPERATURES WILL BE COOLER THAN AVERAGE DURING THE PERIOD. && .LONG TERM /TUESDAY THROUGH SATURDAY/... ECMWF AND GFS ENSEMBLES REMAIN IN GENL AGRMNT WITH DEPICTIONS OF DRY WEATHER FOR THE UPR OH REGION INTO THE WEEKEND AS BROAD RIDGE IS BUILT OVR MUCH OF THE CONUS. DESPITE RECENT ECMWF DETERMINISTIC TRENDS OF AN AMPLIFYING WEAKNESS OVR THE MID ATLANTIC STATES...SUB CLIMO/DRY POPS WERE THUS MAINTAINED. TEMPS UNDR THIS PTN WOULD MODERATE TO AT LEAST 5 DEGREES ABOVE THE AVGS...FORECAST FOR WHICH WAS BASED ON PERSISTENCE AND THE LATEST WPC GUIDANCE. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... GRADUAL CONDITION DETERIORATION TO MVFR/LCL IFR CAN BE EXPECTED LATE TNGT AND INTO SUNDAY AS A CDFNT APCHS FM THE W. ST DVLPMNT IN THE WARM...MOIST FLOW UNDR THE INVERSION IS ANTICIPATED AS IS ELEVATED SHWR DVLPMNT TWD MRNG. THE BTR CHC FOR IFR IS EXPECTED IN THE MORE WIDESPREAD SHWRS AFTR DAYBREAK. OUTLOOK.../SUNDAY NGT THROUGH THURSDAY/... COLD ADVCTN OFF THE GREAT LAKES IS EXPECTED TO SPPRT MVFR STRATOCU THRU MONDAY. THEREAFTER...GENL VFR IS ONLY EXPECTED TO BE TARNISHED BY PERIDAWN FOG AND LCL ST. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$ 24/15

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