Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 160538 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 138 AM EDT TUE SEP 16 2014 .SYNOPSIS... A WEAK AREA OF LOW PRESSURE WILL MOVE EAST ACROSS THE OHIO RIVER VALLEY TONIGHT BEFORE SLIDING OFF THE DELAWARE COAST DURING THE MIDDAY HOURS TUESDAY. THIS LOW...WILL COMBINE WITH A DISTURBANCE ALOFT TO BRING NUMEROUS SHOWERS TO NORTHERN PENN OVERNIGHT...WITH SHOWERS OF THE MORE SCATTERED VARIETY OVER SOUTHERN PENN. THE REST OF THIS WEEK WILL BE MAINLY DRY AS HIGH PRESSURE BRINGS PLENTY OF SUNSHINE AND AND SLIGHTLY BELOW NORMAL TEMPERATURES TO THE AREA. && .NEAR TERM /UNTIL 8 AM THIS MORNING/...
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THICKENING/LAYERED CLOUDS WILL CONTINUE TO SPREAD EAST ACROSS THE SUSQUEHANNA AND JUNIATA RIVER VALLEYS EARLY THIS MORNING. WEAK...1016 MB SFC LOW WAS CENTERED INVOF KUNV AT 05Z WITH A COLD FRONT TRAILING SWWD THROUGH THE OHIO RIVER VALLEY...AND AN INVERTED TROUGH EXTENDING NWD INTO WRN NEW YORK. PRECIP IN THE FORM OF LIGHT TO MODERATE RAIN SHOWERS HAS BEEN LINKED CLOSELY TO THE THERMALLY DIRECT TRANSVERSE CIRCULATION OF A 100 KT...300 MB JET THAT STRETCHED FROM THE ST LAWRENCE VALLEY...TO LAKE ERIE. THE BEST VERTICAL MOTION ASSOCIATED WITH THIS /RIGHT ENTRANCE/ REGION OF THE JET WILL SLIDE ACRS THE NRN HALF OF PENN THROUGH THE MID MORNING HOURS. A LARGE AREA OF LIGHT TO MDT SHOWERS /COVERING MUCH OF NWRN PENN AND NERN OHIO/ WILL SHIFT EAST THROUGH THE OVERNIGHT HOURS AND TARGET MAINLY THE NORTHERN ONE-THIRD TO ONE-HALF OF THE STATE. 21Z SREF...AND 18Z/00Z OPERATIONAL NAM AND GFS INDICATE BASIN AVERAGE QPF AMOUNTS OF 2-3 TENTHS ACROSS THE NRN TIER COUNTIES OF PENN. EC ENSEMBLES ALSO IMPLY QUITE A SHARP GRADIENT IN POPS FURTHER SOUTH ACROSS THE CWA - BETWEEN 1-80 AND I-70/76. LESS THAN ONE TENTH OF AN INCH IS EXPECTED TO THE SW OF A LINE FROM KFIG TO KUNV AND KMDT. LOW TEMPS CONTINUE TO LOOK IN PRETTY GOOD SHAPE WITH MINS RANGING FROM 45-50F ACROSS THE NRN AND WRN MTNS...TO THE LOWER AND MID 50S ELSEWHERE.
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&& .SHORT TERM /8 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
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COLD FRONT WILL BE MOVING EAST ACROSS THE AREA QUITE FAST THIS MORNING. ANY LIGHT SHOWERS AFTER 12Z TODAY SHOULD BE CONFINED ACROSS THE REGION JUST TO THE EAST OF THE SUSQ MAINSTEM. SKIES WILL BECOME CLEAR TO PARTLY CLOUDY THIS AFTERNOON...THOUGH SOME BRIEFLY BKN...FLAT STRATO CU ARE POSSIBLE...ESPECIALLY ACROSS THE NRN MTNS AND LAUREL HIGHLANDS WINDS WILL STAY LIGHT AND VARIABLE AHEAD OF THE CFRONT...WHILE NW WINDS INCREASE TO 6-8 KTS WITH SOME GUSTS INTO THE L-M TEENS RANGE THIS AFTERNOON ACROSS THE CENTRAL AND WESTERN MTNS. MAIN CONCERN FOR LATE IN THE 2ND PERIOD WILL BE POTENTIAL FOR FROST AND LOCALIZED FREEZING TEMPS ACROSS THE NORTHERN MTNS. 00Z MAV NUMBERS ARE AT THE COLDER END OF ALL GUIDANCE...AND HAVE BFD BELOW 32. CLEAR SKIES AND LIGHT WINDS...ALONG WITH HIGH HEIGHTS AND LOW DEWPOINTS/PW VALUES SUPPORT SOME POTENTIAL FOR FROST ETC. STILL A WAYS OUT...LATER SHIFTS CAN MONITOR AND ISSUE FLAGS AS NEEDED.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... BY WED...SURFACE HIGH PRESSURE OVER OHIO VALLEY WITH DRIER COOLER NORTHWEST FLOW IN LOWER LEVELS. THERE MAY BE SOME CLOUDS LINGERING OVER HIGHER TERRAIN UNDER SUBSIDENCE INVERSION EARLY...BUT CENTRAL PA SHOULD SEE GOOD DEAL OF SUNSHINE OVERALL. HIGHS WILL BE ABOUT 5F BELOW NORMAL. TROUGH ALOFT SHARPENS OVER QUEBEC WED NIGHT/THU...PUSHING A WEAK FRONTAL BOUNDARY SOUTH TOWARD PA ON THU. THIS FRONT WILL CONTINUE TO WEAKEN AS IT EDGES SOUTHWARD...BUT A WEAK SHORTWAVE WILL SLIDE OVERHEAD FROM THE MIDWEST. THIS WILL BRING AN INCREASE IN CLOUDS COVER ALONG WITH JUST A CHANCE FOR A SPRINKLE. NORTHERN PA WILL GET A REINFORCING SHOT OF COOLER AIR...KEEPING HIGHS IN THE UPPER 50S TO LOWER 60S. HIGH PRESSURE THEN BUILDS ACROSS THE GREAT LAKES INTO A 1030MB HIGH OVER NEW ENGLAND BY FRI...BRINGING A PERIOD OF QUIET WEATHER AND UNSEASONABLY COOL TEMPERATURES. MORNING LOWS IN THE 30S ARE LIKELY THU NIGHT IF SKIES CLEAR OUT AS ANTICIPATED. HIGHS ON FRI WILL BE MAINLY IN THE 60S AS NW FLOW CONTINUES. RETURN FLOW BEGINS WEAKLY FRI NIGHT...TAKING A LITTLE OF THE BITE OUT OF OVERNIGHT LOWS /THOUGH STILL CHILLY WITH READINGS MAINLY IN THE 40S/. BUT THIS WILL BEGIN A WARMING TREND FOR THE WEEKEND. TEMPS SAT INTO SUN WILL BE 5-8F WARMER THAN FRI...WITH HIGHS APPROACHING 80F IN THE SE. LOWS WILL BE NOTICEABLY MILDER AS WELL AS LOW LEVEL MOISTURE INCREASES IN STRENGTHENING SW FLOW. HEADING INTO SUNDAY...DEEPENING LOW CENTERED WELL TO OUR NORTH AS A TROUGH AXIS ROTATES THROUGH THE GREAT LAKES WILL BRING PLENTY OF CLOUDS AND A CHANCE FOR SHOWERS. MODELS STILL SHOWING LARGE DIFFERENCES ON EVOLUTION OF THIS SYSTEM...WITH GFS MORE PROGRESSIVE AND ECMWF ACTUALLY BRINGING A SECOND WAVE AROUND THE BACKSIDE OF THE TROUGH AND DEVELOPING A STUBBORN CLOSED UPPER LOW OVER THE REGION. FOR NOW WILL SPLIT THE DIFFERENCE AND HOLD ON TO MENTION OF SHOWERS INTO MON ALONG WITH ANOTHER SHOT OF COOLER AIR AND SEE HOW THIS PLAYS OUT OVER NEXT COUPLE OF DAYS. && .AVIATION /05Z TUESDAY THROUGH SATURDAY/... AREA OF SHOWERS MOVING INTO NWRN PA ATTM. ARE FAIRLY LIGHT BUT WILL LEAD TO SOME GRADUAL REDUCTIONS ESP ACROSS NWRN AIRFIELDS EARLY THEN CENTRAL AND SRN OVERNIGHT. CONDITIONS SHOULD BECOME VFR BY MID TO LATE MORNING ON TUESDAY...AS THE COLD FRONT MOVES EAST OF THE AREA. IT WILL BE BREEZY AT TIMES ON TUE. SOME POTENTIAL FOR FOG TUESDAY NIGHT...AS HIGH PRESSURE BUILDS OVER THE AREA. MAINLY DRY CONDITIONS THE REST OF THE WEEK...AS HIGH PRESSURE PREVAILS. OUTLOOK... WED-SAT...MAINLY VFR CONDITIONS. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT/MARTIN NEAR TERM...LAMBERT SHORT TERM...LAMBERT/MARTIN LONG TERM...RXR AVIATION...GARTNER/MARTIN

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