Area Forecast Discussion
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000 FXUS61 KPBZ 300814 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 415 AM EDT THU OCT 30 2014 .SYNOPSIS... BUILDING HIGH PRESSURE TODAY WITH DRIER WEATHER. ANOTHER LOW PRESSURE SYSTEM WILL BRING UNSETTLED WEATHER FRIDAY AND SATURDAY. && .NEAR TERM /THROUGH TONIGHT/... NEAR SFC FLOW VEERED NWRLY OVERNIGHT AND A PLUME OF LAKE MOISTURE DEVELOPED LOW STRATOCU OVER THE SRN SHORES OF LAKE ERIE AND AREAS ADJACENT. SRN EXPANSION OF THIS CLOUD COVER HAS NOT BEEN NEARLY AS AGGRESSIVE AS PREVIOUSLY FORECAST...HOWEVER...AS DRY AIR ALOFT HAS BEEN ABLE TO ERODE THE MOISTURE UNDER THE UPPER TROF AXIS. THIS HAS SQUASHED WIDESPREAD LAKE-INDUCED SHOWERS AND HAS LED TO ALMOST THE SRN HALF OF THE CWA REMAINING CLEAR THROUGH THE PRE- DAWN HOURS. WINDS HAVE GENERALLY STAYED UP OVERNIGHT ALLOWING SOME MIXING OF THE LOW LEVELS...BUT SHELTERED LOCATIONS UNDER CLEAR SKIES HAVE RADIATED DOWN INTO THE MID 30S. LOOKING FORWARD...CLOUD FORECAST DIFFICULT THROUGH TODAY AS MOST HI-RES MODELS HAVE NOT FULLY RESOLVED THE EXTENT OF THE DRY AIR INHIBITING CLOUD DEVELOPMENT IN THE LOW LEVELS. MODIFIED THE INITIAL SKY FORECAST BASED ON CURRENT SATELLITE TRENDS AND HAVE GRADUALLY BLENDED INTO TONED DOWN VERSION OF THE PREVIOUS FORECAST. EXPECTING TO SEE MOSTLY CLOUDY CONDITIONS PERSIST ALONG THE NORTH UNDER THE LAKE ENHANCED REGION WHILE GETTING AT LEAST SOME PATCHES OF SUN FURTHER SOUTH IN THE CWA. FORECAST AREA REMAINS COOL TODAY UNDER NW FLOW REGIME. WITH VERY LOW SPREAD ACROSS GUIDANCE FOR TEMPS...HAVE MAINTAIN CURRENT FORECAST WITH MINOR TWEAKS BASED ON BIAS CORRECTED MET. TAX && .SHORT TERM /FRIDAY THROUGH SUNDAY/...
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MODELS ARE STILL FORECASTING A RATHER HISTORICALLY DEEP H500 TROUGH/UPPER LOW TO DEVELOP THROUGH SATURDAY. 12Z GEFS/NAEFS ENSEMBLES SHOW STANDARDIZED ANOMALIES OF 4 TO 5 STANDARD DEVIATIONS BELOW NORMAL IN THE CAROLINAS ON SATURDAY. INTERESTINGLY...THE STRENGTH OF THE SYSTEM WILL PLAY A ROLE IN PREVENTING MUCH OF A SNOW IMPACT FOR THE CWA. H500 UPPER LOW IS STILL EXPECTED TO DIP FROM THE WESTERN GREAT LAKES AT 12Z FRIDAY TO THE CAROLINAS BY 12Z SATURDAY. CERTAINLY ENOUGH MOISTURE AND LIFT PROVIDED BY THE LOW FOR WIDESPREAD PRECIPITATION BY FRIDAY AFTERNOON. WHAT IS INTERESTING IS THAT IT STILL APPEARS THAT THE SYSTEM BECOMES SO WRAPPED UP THAT THE CORE OF THE COLD AIR WILL DIP SOUTH OF THE CWA...WHILE RELATIVELY WARMER AIR WRAPS AROUND AND SPILLS IN FROM THE SOUTH AND EAST...ESPECIALLY NEAR THE SURFACE. STILL FORESEE SOME SNOWFLAKES MIXING IN FOR MOST AREAS FRIDAY NIGHT INTO EARLY SATURDAY. THE RIDGES IN THE SOUTHEAST CWA CORNER HAVE THE BEST CHANCE OF GOING TO ALL SNOW AND PERHAPS PICKING UP A LIGHT ACCUMULATION OF AN INCH OR TWO. ELSEWHERE...TEMPERATURES FROM H925 ON DOWN LOOK TOO WARM FOR ACCUMULATION. ON SATURDAY THE UPPER LOW SWINGS AROUND THE BASE OF THE TROUGH AND MOVES OFFSHORE...FEEDING A DEVELOPING NOR`EASTER WELL OFF TO OUR EAST. MOST LOCATIONS WILL TURN BACK TO ALL RAIN BY LATE MORNING. COLDER AIR WILL FINALLY START TO COLLAPSE IN FROM THE NORTH AS LOW LEVEL FLOW TURNS NORTHERLY...BUT BY THEN MOISTURE AVAILABILITY BECOMES MORE QUESTIONABLE. POPS DROP OFF TO CHANCE BY AFTERNOON. COVERAGE WILL CONTINUE TO DECREASE SATURDAY NIGHT...ENDING BEFORE 12Z SUNDAY. BACKSIDE UPSLOPE FLOW DOES NOT LOOK TO BE A SIGNIFICANT CONCERN. DRY WEATHER AND SOME SUNSHINE RETURN FOR SUNDAY. DID NOT MAKE MAJOR CHANGES TO TEMPERATURES...BLENDING IN THE MOST RECENT MOS GUIDANCE. VALUES WILL RUN SOME 10-15 DEGREES BELOW NORMAL AT TIMES THIS WEEKEND. CL
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&& .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
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USED HPC GUIDANCE FOR THIS PERIOD WHICH WAS BASED ON GEFS/ECENS MEANS. A COLD SUNDAY NIGHT WILL BE FOLLOWED BY MODERATING TEMPERATURES...WITH READINGS CLOSE TO SEASONAL BY TUESDAY AS A FLAT UPPER RIDGE MOVES THROUGH. ANOTHER...MUCH MORE SHALLOW TROUGH ARRIVES DURING THE MIDWEEK PERIOD WITH ATTENDANT SURFACE SYSTEMS...PROMISING AN UNSETTLED END TO THE EXTENDED PERIOD. CL
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&& .AVIATION /07Z THURSDAY THROUGH MONDAY/... GENERAL VFR FORECAST THROUGH THE DAY FOR MOST LOCATIONS...ALTHOUGH MVFR CIGS COULD BE OBSERVED TEMPORARILY THIS MORNING AS LARGE STRATO CU FIELD DESCENDS FOLLOWING A PLUME OF LLVL MOISTURE FROM LAKE ERIE. FKL AND DUJ WILL STAY MVFR THROUGH LATE MORNING BEFORE IMPROVING LATER IN THE AFTERNOON COLDER AIR WILL SLOWLY LIFT NORTHWARD THURSDAY ALLOWING FOR STRATOCU DECK TO EVENTUALLY THIN OUT. OUTLOOK.../THURSDAY NIGHT THROUGH MONDAY/... WIDESPREAD RESTRICTIONS ARE EXPECTED ON FRIDAY AS DEEPENING LOW PRES IS PROJECTED TO SHUNT A BROAD MSTR SWATH OVR THE UPR OH REGION. ENSUING COLD ADVCTN WL THEN MAINTAIN STRATOCU POTENTIAL UNTIL SFC HIGH STRENGTHENS ON SUNDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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