Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 211902 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 302 PM EDT MON APR 21 2014 .SYNOPSIS...
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HIGH PRESSURE WILL FINALLY LOSE ITS GRIP OVER THE AREA TONIGHT AS CLOUDS INCREASE AHEAD OF AN APPROACHING COLD FRONT. SHOWERS AND PERHAPS A THUNDERSTORM ARE EXPECTED WITH THE FRONTAL PASSAGE ON TUESDAY...ALONG WITH GUSTY WINDS AND ISOLATED THUNDER. MUCH COLDER AIR WILL WORK INTO THE COMMONWEALTH FOR TUESDAY NIGHT AND WEDNESDAY...WITH LAKE EFFECT SNOW SHOWERS OVER THE NORTHWEST AND WEST CENTRAL MOUNTAINS AND FLURRIES POSSIBLE OVER THE REST OF THE CENTRAL AND NORTHERN MOUNTAINS. A COOL BUT MAINLY DRY PERIOD IS EXPECTED WEDNESDAY AND THURSDAY...WITH HIGH PRESSURE RETURNING TO THE AREA. THE NEXT COLD FRONT AND ASSOCIATED RAIN CHANCES ARE FORECAST TO ARRIVE ON FRIDAY.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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GORGEOUS AFTERNOON IN PROGRESS AS MOSTLY SUNNY SKIES COMBINE WITH SFC HIGH PRESSURE CENTERED OVER DEL MARVA REGION TO WARM THINGS UP NICELY. DOWNSLOPING SOUTHERLY WIND ALLOWING WESTERN AND NORTHWEST PA TO WARM UP THE MOST...WITH TEMPS IN THE LOWER TO MIDDLE 70S PRESENTLY. MOST PARTS OF CENTRAL PA ARE IN THE MID TO UPPER 60S WITH A BEAUTIFUL EVENING EXPECTED...AND ONLY SOME INCREASING HIGH CLOUDS WORKING THEIR WAY EAST AS THE UPPER RIDGE BEGINS TO BREAK DOWN OVERHEAD. CLOUDS WILL INCREASE AHEAD OF THE FRONT OVERNIGHT...WITH SHOWERS LIKELY ACROSS FAR WESTERN AND NORTHWEST BY 12Z. MINS WILL BE MUCH MILDER THAN RECENT MORNINGS...RANGING THROUGH THE 50S.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
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FRONTAL SYSTEM CROSSES CENTRAL PA ON TUESDAY...AND TIMING OF FROPA FROM 15Z TO 20Z IS SUPPORTIVE OF THUNDER ACCOMPANYING THE FRONT. INSTABILITY STILL APPEARS TO BE LACKING AT THIS TIME HOWEVER...WITH MUCAPES ONLY IN THE 300-450 J/KG RANGE...LIKELY LIMITED BY SFC DEWPOINTS. STILL...THE INSTABILITY WILL BE SUFFICIENT TO MIX DOWN SOME 25 TO 35KT GUSTS AND EXPECT TO SEE A NARROW COLD FRONTAL RAINBAND FEATURE WITH THE FROPA. MUCH COLDER AIR DIVES INTO WEST CENTRAL PA BY 00Z...WITH 850 MB READINGS PLUNGING BELOW ZERO. NOT LOOKING FOR ANYTHING SEVERE...THOUGH SMALL HAIL MAY BE POSSIBLE WITH STRONG JET MAX AND RAPIDLY COOLING TEMPS ALOFT. MAXES WILL OCCUR MID TO LATE MORNING TO EARLY AFTERNOON...WITH HIGHS RANGING FROM THE MID 50S NORTHWEST TO AROUND 70 SOUTHEAST.
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&& .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... SFC LOW OVER NORTHERN NEW ENGLAND AT 00Z WED WILL DEEPEN INTO THE CANADIAN MARITIMES THROUGH DAY 3/WED...AS THE PARENT UPPER LEVEL TROUGH AMPLIFIES SEWD ACROSS THE NORTHEASTERN CONUS AND EVENTUALLY CLOSES-OFF NEAR THE GULF OF MAINE/SOUTH OF NOVA SCOTIA BY 12Z THURS. THIS SHOULD MARK THE BEGINNING OF A LARGER SCALE PATTERN TRANSITION FROM MODERATELY PROGRESSIVE TO A BLOCKY/SLOWER-EVOLVING REGIME BY THE WEEKEND AND INTO EARLY NEXT WEEK. FRONTAL RAIN SHOWERS SHOULD EXIT THE ERN 1/3 OF THE CWA LATE TUES EVE/EARLY TUES NIGHT. GUSTY POST-FRONTAL WNW FLOW WILL INCREASE THROUGH WEDNESDAY AND HELP DIRECT AN ABNORMALLY COOL CANADIAN AIRMASS INTO THE AREA FOR THE MIDDLE OF THE WEEK. DAYTIME HIGHS ON WEDNESDAY WILL AVG 5-10 DEGREES BELOW NORMAL WITH A GRADUAL REBOUND ON THURSDAY. CAN/T RULE OUT SOME SNOW SHOWERS DOWNWIND OF LAKE ERIE AND OVER THE WESTERN HIGH TERRAIN WEDNESDAY MORNING. SFC HIGH PRES RIDGE AXIS WILL CROSS THE AREA ON THURSDAY. AT THIS TIME IT APPEARS THAT THERE WILL BE ENOUGH OF A PRES GRADIENT AND NW WIND TO PREVENT FROST/FREEZE HEADLINES FOR THE LOWER SUSQ. VALLEY THURSDAY MORNING. THERE IS DECENT MODEL/ENSEMBLE AGREEMENT IN A SHORTWAVE TROUGH AND SFC LOW PRESSURE TRACKING THROUGH THE GREAT LAKES REGION BY THE END OF THE WEEK...WITH THE NEXT COLD FRONT FCST TO ARRIVE ON FRIDAY ACCOMPANIED BY THE CHC FOR SHOWERS. THERE IS INCREASING SPREAD IN THE GUIDANCE FOR THE WEEKEND AND INTO EARLY NEXT WEEK WITH HINTS OF A REX BLOCK DEVELOPING OVER THE CENTRAL NOAM AND MEAN TROUGH LINGERING OVER SERN CANADA AND PERHAPS THE NERN US. THE 21/12Z GFS ARE STRONGLY IN FAVOR OF THIS EVOLUTION WHILE THE 21/00Z ECMWF AND 21/12Z GEFS ARE NOT QUITE AS AMPLIFIED WITH TROUGHING OVER SERN CANADA/NERN US. DUE TO THE VARIABILITY IN THE GUIDANCE...OPTED FOR A CONSENSUS BLEND FOR MAX/MIN/POP WHICH RESULTED IN NEAR NORMAL TEMPS AND RELATIVELY LOW PROBS FOR RAIN. && .AVIATION /19Z MONDAY THROUGH SATURDAY/...
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A WEAKENING RIDGE ALOFT WILL CONTINUE TO BRING VFR CONDITIONS THROUGH TONIGHT. HIGH CLOUDS WILL INCREASE LATER THIS EVENING... WITH THICKENING AND LOWERING MID LEVEL CLOUDS AFTER MIDNIGHT. FOR TUE...A SHORT WAVE AND ASSOCIATED FRONT WILL BRING RAIN SHOWERS TO PENNSYLVANIA...STARTING IN THE NW BY 12Z. MAY SEE AN ISOLATED TSTORM IN THE SUSQ VALLEY LATER IN THE DAY. BREEZY NW WINDS WILL DEVELOP IN THE AFTERNOON...AND CONTINUE INTO WED. OUTLOOK... TUE...SEVERAL-HOUR PERIOD OF MVFR CIGS POSS WITH BRIEF MVFR VSBYS IN SHOWERS ACCOMPANYING A COLD FRONTAL PASSAGE. BREEZY NW WINDS DEVELOPING LATE. TUE NIGHT-WED...MVFR NORTH/WEST WITH SCT -SHRA...VFR ELSEWHERE. BREEZY NW WINDS. THU...VFR. NO SIG WX. FRI...MVFR WITH CHC SHRA. SAT...MVFR WITH CHC SHRA
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&& .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DEVOIR/STEINBUGL NEAR TERM...DEVOIR SHORT TERM...DEVOIR LONG TERM...STEINBUGL AVIATION...DEVOIR/RXR

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