Area Forecast Discussion
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000 FXUS61 KPBZ 020559 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 159 AM EDT TUE JUN 2 2015 .SYNOPSIS... AN UPPER LEVEL LOW WILL NEARLY STALL OVER THE OHIO AND TENNESSEE VALLEYS THROUGH THURSDAY...WITH RAINFALL CHANCES MAINLY SOUTH OF PITTSBURGH. TEMPERATURES WILL RISE TO MORE SEASONABLE LEVELS. && .NEAR TERM /THROUGH TONIGHT/... OVERNIGHT PERIOD WILL REQUIRE SOME CHANGES TO POPS. WILL KEEP EVERYTHING IN THE SLIGHT CHANCE OR CHANCE CATEGORY AS ANY SHOWER ACTIVITY WILL BE SPOTTY AND LIGHT. MODELS CONTINUE TO KEEP THE AREA SOCKED IN WITH LOW CLOUDS. MODELS WANT TO SHOVE THE PRECIPITATION AND DEEPER MOISTURE SOUTHWARD THIS MORNING...AS A WEAK UPPER LEVEL RIDGE SQUEEZES IN FROM THE EAST AND OVER SPREADS THE NORTHERN PORTION OF MY FORECAST AREA. CONFIDENCE IN THE CLOUD FORECAST IS LOW WITH STILL A GOOD DEAL OF LOWER MOISTURE SOUTH OF THE AFOREMENTIONED RIDGE AND A PLETHORA OF SHORTWAVES REVOLVING AROUND THE CUTOFF 500 LOW. HAVE DECIDED TO GO WITH AN OPTIMISTIC CLOUD FORECAST...AT LEAST FOR THE NORTHERN HALF OF THE REGION. OBVIOUSLY CLOUDS WILL BE CRITICAL FOR DAYTIME HIGHS...MAKING FOR A TRICKY TEMPERATURES FORECAST AS WELL. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
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STRONG CONSENSUS EXISTS ON A CLOSED UPPER CYCLONE TRAVERSING THE TENNESSEE VALLEY EARLY IN THE PERIOD WITH THE LOWER HALF OF THE TROPOSPHERE AT LEAST FEATURING EASTERLY FLOW OVER THE CWA. THIS SHOULD ALLOW FOR MOISTURE CREEP INTO AT LEAST THE SOUTHERN HALF OF THE CWA...AS WELL AS ALLOW FOR SOME INTERESTING WIND FEATURES FOR WEDNESDAY. MODEL SOLUTIONS FAVOR FAIRLY STRONG EASTERLY FLOW AT THE RIDGETOPS...WITH STRONG LAPSE RATES BELOW THE RIDGETOPS AND A STABLE LAYER NEAR THE RIDGETOPS. THIS SEEMS AS THOUGH IT WOULD BE CONDUCIVE TO DOWNSLOPE WIND GUSTS ON WEDNESDAY. THERE DOES NOT SEEM TO BE ENOUGH MOMENTUM IN THE COLUMN FOR THEM TO BE OF MUCH CONCERN...HOWEVER EASTERLY GUSTS OF 20-30 KTS WOULD SEEM PLAUSIBLE IN WESTMORELAND AND FAYETTE COUNTIES. IN GENERAL...THE PATTERN EVOLVES VERY SLOWLY THROUGH THE REMAINDER OF THE WEEK AS THE UPPER LOW OVER THE SOUTHEAST SLOWLY MIGRATES TOWARD THE COAST AND EVENTUALLY WEAKENS. THIS SLOWLY TURNS OUR LOW LEVEL FLOW FROM THE EAST TO THE NORTHWEST BY LATE IN THE WEEK. THIS FLOW CHANGE WILL ALLOW FOR A BIT OF COLDER AIR ALOFT TO RUN INTO THE AREA...INCREASING LAPSE RATES BY FRIDAY...WHICH SHOULD ALLOW FOR A CHANCE OF SHOWERS AND THUNDERSTORMS. TEMPERATURES THROUGH THE SHORT TERM INDICATE A WARMING TREND AS STRATUS FINALLY GIVES WAY TO BETTER MIXING AND MORE INSOLATION AS THE UPPER LOW LOSES ITS DEFINITION. FRIES
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&& .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
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MODEL AND ENSEMBLE GUIDANCE CONTINUES TO FAVOR THE PASSAGE OF A NORTHWESTERLY COLD FRONT ON SATURDAY...WHICH SHOULD FINALLY BRING A DRIER PERIOD WITH AMPLE SUNSHINE BEHIND IT. HOWEVER...THE IMPROVED CONDITIONS WILL LIKELY BE SHORT-LIVED AS THE CONSENSUS FAVORS CYCLONIC FLOW REESTABLISHING ITSELF OVER THE CWA BY EARLY NEXT WEEK...MEANING A SOUTHERLY DROPPING OF THE JET AXIS AND A BETTER CHANCE THE STRONG TRACK WOULD FAVOR WET CONDITIONS AGAIN BY EARLY NEXT WEEK. FRIES
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&& .AVIATION /06Z TUESDAY THROUGH SATURDAY/... DEGRADED CONDITIONS...INCLUDING IFR CEILINGS...ARE EXPECTED TO CONTINUE OVERNIGHT AS BOUNDARY LAYER MOISTURES REMAINS TRAPPED OVER MOST OF THE UPPER OHIO VALLEY. A WEAK SHORTWAVE IN SOUTHWEST FLOW ALOFT WILL ALSO SUPPORT LIGHT...BUT FAIRLY SPOTTY SHOWERS A IT PASSES OVER THE REGION OVERNIGHT. RIDGING ALOFT MAY OFFER SOME IMPROVEMENT ON TUESDAY...BUT CONFIDENCE IS LOW DUE TO SO MUCH RESIDUAL MOISTURE LOCKED OVER MOST PORTS. WILL OFFER A MORE OPTIMISTIC FORECAST...BUT HESITANTLY. .OUTLOOK.../TUESDAY THROUGH SATURDAY/... CONDITIONAL RESTRICTIONS ARE EXPECTED INTO LATE WEEK AS UPPER TROUGH REMAINS ENTRENCHED OVER THE EASTERN U.S. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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