Area Forecast Discussion
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000 FXUS61 KPBZ 261528 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 1128 AM EDT TUE MAY 26 2015 .SYNOPSIS... WARM AND HUMID CONDITIONS WILL PERSIST THROUGH THE WEEK...WITH SHOWER AND THUNDERSTORM CHANCES EACH DAY. && .NEAR TERM /THROUGH TONIGHT/...
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A WEAK SHORTWAVE IN SOUTHWEST FLOW SHOULD BRING SCATTERED SHOWERS AND POSSIBLY A THUNDERSTORM TO THE AREA THIS AFTERNOON. MID LEVEL TEMPERATURES OVER THE REGION WILL CONTINUE TO INHIBIT INSTABILITY WHILE DEEP MOISTURE WILL LIMIT THE EVAPORATIVE COOLING POTENTIAL...HENCE ACCELERATING DOWNDRAFT POTENTIAL. DESPITE INCREASED FLOW ALOFT...DEEP LAYER SHEAR PROJECTIONS ARE MARGINAL...AND WITH NAM SURFACE DEWPOINTS AS USUAL OVERDONE...THE SEVERE THREAT LOOKS MARGINAL AT BEST TODAY. THIS IS ALSO SUPPORTED BY THE MORNING INSTABILITY CHART. ANOTHER ADVANCING SHOTRTWAVE IS EXPECTED TO BRING ADDITIONAL SHOWER AND THUNDERSTORM ACTIVITY THIS EVENING AND OVERNIGHT. TEMPERATURES WERE MAINLY TWEAKED DOWNWARD SLIGHTLY TODAY TO GET MORE IN LINE WITH MODEL CONSENSUS.
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&& .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... THE FIRST HALF OF THE PERIOD WILL CONSIST OF UNSETTLED WEATHER AS AN UPPER LEVEL SHORTWAVE TROUGH IS PROGGED TO BE OVER THE GREAT LAKES AND SHIFT EASTWARD. DEEP MOISTURE WILL BE MAINTAINED OVER THE REGION ALLOWED BY SOUTHWEST FLOW. THEREFORE...CHANCE TO LIKELY POPS WERE MAINTAINED AND ADJUSTED SLIGHTLY BASED ON LATEST GUIDANCE. A LULL IN PRECIPITATION CAN BE EXPECTED LATE THURSDAY INTO FRIDAY AS BRIEF HIGH PRESSURE BUILDS UNDER A WEAK RIDGE IN THE WAKE OF THE SHORTWAVE TROUGH. PRECIPITATION CHANCES RISE AGAIN ON SATURDAY SUPPORTED BY AN APPROACHING SURFACE BOUNDARY AND A WEAK SPLIT FLOW ALOFT. THE FRONT IS EXPECTED TO SLOWLY SAG ACROSS THE FORECAST AREA THROUGH SATURDAY AS PREDICTED BY ECMWF AND GFS SOLUTIONS. FORECASTED TEMPERATURES WILL BE ABOVE NORMAL THROUGH THE PERIOD. && .LONG TERM /SATURDAY THROUGH MONDAY/... VARIOUS LONG RANGE SOLUTIONS AGREE ON STUBBORN BOUNDARY LAID ACROSS THE FORECAST AREA THROUGH THE WEEKEND. THEREFORE CHANCE POPS WERE PRESERVED WITH THE SUPPORT OF A SERIES OF UPPER LEVEL DISTURBANCES ACROSS THE UPPER OHIO VALLEY. GFS AND ECMWF DIFFER OVER THE OUTCOME OF AN APPROACHING TROUGH FROM THE MIDWEST IN TERMS OF MAGNITUDE...POSITION...AND TIMING. THEREFORE PERSISTENCE WAS HEAVILY USED IN THE LATTER HALF OF THE PERIOD AND LOW CHANCE POPS WERE INTRODUCED. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/... GENERALLY VFR CONDITIONS ARE EXPECTED TODAY WITH ONLY LOCAL RESTRICTIONS POSSIBLE IN SCATTERED SHOWERS OR ISOLATED THUNDERSTORMS. RESTRICTION POTENTIAL...MAINLY MVFR...IS EXPECTED TO INCREASE TONIGHT WITH A SATURATING BOUNDARY LAYER AND CROSSING SHORTWAVE SUPPORTING SOME SHOWERS. .OUTLOOK.../TUESDAY NIGHT THROUGH SATURDAY/... ABUNDANT MOISTURE AND DISTURBANCES IN SOUTHWEST FLOW ARE LIKELY TO SPAWN PERIODIC RESTRICTIONS UNTIL A COLD FRONT CROSSES ON WEDNESDAY NIGHT. PRECIP CHANCES WILL INCREASE AGAIN THIS WEEKEND. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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