Area Forecast Discussion
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000 FXUS61 KPBZ 281725 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 125 PM EDT THU APR 28 2016 .SYNOPSIS... LOW PRESSURE WILL BRING RAIN TODAY INTO TOMORROW. MORE RAIN WILL ARRIVE LATE SATURDAY INTO SUNDAY. && .NEAR TERM /THROUGH TONIGHT/...
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RAIN SHOWERS WILL CONTINUE TO MOVE THROUGH THE NORTHERN 1/3 OF THE FORECAST AREA ALONG A MID-LEVEL FRONT WITH ISENTROPIC LIFT ACROSS. THIS HAS MET SOME RESISTANCE WITH DRY AIR NORTH OF I-80...BUT OBSERVATIONS REVEAL THAT THE LOWER COLUMN HAS SINCE SATURATED. SURFACE LOW PRESSURE APPROACHING FROM THE WEST WILL GENERATE ADDITIONAL SHOWERS AND PERHAPS A FEW THUNDERSTORMS...BUT COVERAGE SHOULD BE RELEGATED TO SOUTH OF I-70. FORCING WILL THEN BE WEAK OVERNIGHT...AS THE CENTER OF THE LOW MOVES OVER...SO RAIN CHANCES SHOULD BE LIMITED. DESPITE THIS...NOT EXPECTING A COMPLETELY DRY FORECAST AS A DEEP LAYER OF NEAR SURFACE MOISTURE WILL BE RESIDENT THROUGH EARLY FRIDAY. TEMPERATURES HAVE VARIED GREATLY FROM NORTH TO SOUTH AS LOCATIONS SOUTH OF I-70 HAVE PARTIAL CLEARING ALLOWING TEMPERATURES TO RISE INTO THE MID 60S ALREADY. FURTHER NORTH AND ALONG THE EAST COOL AIR IS POOLING UP AGAINST THE HIGHER ELEVATIONS AND WRAPPING NORTH OF I-80. TEMPERATURES HERE WILL HAVE TROUBLE GETTING OUT OF THE MID 40S. WHILE MUCH OF FRIDAY WILL REMAIN DRY...THE OPENING LOW PRESSURE SYSTEM WILL OPEN UP AND PASS ALONG OUR NORTH. THIS WILL BRING ADDITIONAL SCATTERED SHOWERS...PRIMARILY IN THE NORTHERN HALF OF THE FORECAST AREA. TAX
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY/... WITH LOW PRESSURE CENTERED OVER SOUTHWEST PENNSYLVANIA FRIDAY MORNING...SKIES WILL REMAIN OVERCAST UNTIL THE LOW PUSHES EAST. ALTHOUGH SCATTERED SHOWERS WILL CONTINUE FRIDAY...CONDITIONS SHOULD DRY OUT BY THE EVENING. YESTERDAYS 12Z MODELS DEPICTED PRECIPITATION MOVING INTO THE REGION MORE QUICKLY ON SATURDAY...AND TONIGHTS 00Z MODELS HAVE CONTINUED THAT TREND. SIGNIFICANTLY INCREASED POPS FOR SATURDAY AFTERNOON...ESPECIALLY ACROSS THE SOUTH. TEMPERATURES WILL BE SLIGHTLY BELOW NORMAL ON FRIDAY WITH CLOUD COVER...WITH HIGHS INCREASING ABOUT 5 DEGREES ON SATURDAY. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... LATEST MODEL RUNS SHOW GOOD CONTINUITY WITH PREVIOUS RUNS AND OVERALL BETTER AGREEMENT IN REGARDS TO TIMING AND TRACK OF A SURFACE LOW CENTER PROGGED TO TRACK OVER SOUTHERN PORTIONS OF THE FORECAST AREA AND RESULT IN PRECIPITATION CHANCES SATURDAY NIGHT THROUGH MONDAY. OVER THAT TIME ENSEMBLES SHOW PWAT ANOMALIES BETWEEN 1.5 AND 2 STD DEVIATIONS ABOVE NORMAL AND M-CLIMATE RETURN INTERVALS OF 1-2...SO WITH THAT ANTICIPATE A FAIR AMOUNT OF QPF AS THINGS WRAP UP ON MONDAY WITH VALUES FROM AROUND 0.75 ACROSS THE NORTH TO OVER AN INCH SOUTH OF PITTSBURGH DURING THIS TIME. THIS IS SUPPORTED BY THE RAW GEFS MEAN...DETERMINISTIC QPF FORECAST BASED OFF A RE-FORECAST OF THE TOP ANALOGS...AND LATEST CIPS ANALOGS. AT THIS POINT THERE LOOKS TO BE A BREAK MONDAY EVENING THROUGH THE DAY ON WEDNESDAY DURING WHICH TIME RIDGING OVER THE WESTERN CONUS SIGNIFICANTLY STRENGTHENS AND TROUGHING DEEPENS ACROSS THE EASTERN CONUS IN RESPONSE. THERE IS RELATIVELY HIGH CONFIDENCE IN THE LONGWAVE TROUGH DEVELOPING BASED ON MODERNITY`S AND RMOP DATA...BUT HOW DEEP AND TIMING OF SHORTWAVES REMAIN A QUESTION. THERE HAS BEEN A DEEPENING TREND OVER THE PAST 10 MODEL RUNS OF THE PARENT LOW TO THE NORTH. AND WITH THAT IN MIND OPTED TO GO COOLER THAN SUPERBLEND GUIDANCE...BUT NOT TOO FAR BELOW CLIMO NORMS AS TEMP AND HEIGHT ANOMALIES ONLY SIT BETWEEN 1.5 TO 2 AT THIS POINT. && .AVIATION /17Z THURSDAY THROUGH MONDAY/...
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CONDITIONS WILL CONTINUE TO DETERIORATE ALONG THE NORTH AS LOW- LEVEL SATURATION CONTINUES. ONCE TERMINALS NORTH OF KPIT DROP BELOW 10KFT CIGS...THEY SHOULD REMAIN THERE THROUGH THE DURATION OF THE TAF PERIOD. SOME CLEARING SOUTH OF PITTSBURGH WILL ALLOW MVFR/VFR SCATTERING TO OCCUR...BUT THIS SHOULD BE TEMPORARY. HAVE THESE TERMINALS DROPPING TO IFR AGAIN TONIGHT AS THE LOW POSITIONS OVERHEAD. TERMINALS IN BETWEEN...KPIT/KBVI/KAGC...WILL CONTINUE TO BOUNCE AROUND THIS AFTERNOON...BUT ARE EXPECTED TO ALSO DROP TO IFR OR WORSE TONIGHT. LITTLE IMPROVEMENT WILL BE ACHIEVED THROUGH THE DAY FRIDAY. LIGHT NORTHEASTERLY SURFACE FLOW WILL DISSIPATE TO LIGHT AND VARIABLE TONIGHT WITH SURFACE LOW IN THE AREA. SURFACE WINDS WILL THEN REMAIN UNDER 10KTS FROM THE WEST-NORTHWEST AS THE LOW MOVES EAST. TAX .OUTLOOK /THURSDAY NIGHT THROUGH MONDAY/... RESTRICTIONS ARE LIKELY INTO FRIDAY...AND AGAIN SAT NIGHT/SUN...AS AREAS OF LOW PRESSURE CROSS THE REGION. BASED OFF TOP ANALOGS...IFR AND POSSIBLY SOME LIFR MAY BE POSSIBLE ON SUNDAY.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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