Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 040449 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1149 PM EST TUE MAR 3 2015 .SYNOPSIS... LOW PRESSURE WILL TRACK NORTH OF PENNSYLVANIA TONIGHT...AS ITS TRAILING COLD FRONT SAGS SOUTH THROUGH THE REGION. A WAVE OF LOW PRESSURE WILL TRACK SOUTH OF PENNSYLVANIA WEDNESDAY NIGHT AND EARLY THURSDAY. HIGH PRESSURE WILL BUILD SOUTHEAST INTO THE STATE FRIDAY AND SATURDAY. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... LL JET AND ASSOC PUSH OF WARM AIR ALOFT HAS CHANGED PRECIP TO PLAIN RAIN OVR MUCH OF THE ALLEGHENY PLATEAU AS OF 04Z. MEANWHILE...FZRA CONTINUES TO FALL ACROSS MOST OF THE REST OF CENTRAL PA. MDL SOUNDINGS...AS WELL AS LATEST HRRR OUTPUT...CONTINUE TO INDICATE THE LOW LVL COLD AIR WILL ERODE FROM WEST TO EAST OVERNIGHT WITH THE LAST OF THE FZRA ENDING ACROSS THE HIGH TERRAIN NE OF KIPT BTWN 06Z-09Z. BASED ON ASOS ICE ACCRETIONS THRU 02Z AND UPSTREAM RADAR TRENDS...HAVE DOWNGRADED ICE STORM WARNING TO A WINT WX ADV ACROSS THE N MTNS. DESPITE WARMING TEMPS...WILL MAINTAIN WINT WX ADV THRU 06Z ACROSS MUCH OF THE ALLEGHENY PLATEAU...DUE TO POTENTIAL OF RESIDUAL ICY SPOTS ON UNTREATED ROADS. SPOTTER FROM WARREN CO CONFIRMED THE ICY ROADS WITH TEMPS ABV 32F AT 01Z. LOW LVL COLD AIR WILL BE MORE PERSISTENT EAST OF THE MTNS...SO HAVE KEPT ADV IN PLACE THRU 12Z...BUT MID SHIFT MAY NEED TO CANCEL EARLY. REGIONAL RADAR LOOP AT 04Z ALREADY SHOWING PRECIP TAPERING OFF ACROSS THE NORTHERN COUNTIES...AND NR TERM MDL DATA INDICATES THE FOCUS OF ADDITIONAL PRECIP TONIGHT /IN THE FORM OF RAIN/ WILL BE OVR THE LAUREL HIGHLANDS...WHERE SWRLY LL JET AND PLUME OF HIGHER PWATS INTERSECT THE HIGHER TERRAIN OF SW PA. MAY HAVE TO BE CONCERNED ABOUT LOCALIZED FLOODING FROM KJST SOUTHWARD...WHERE RAINFALL AND TEMPS APPROACHING 50F COULD WILL PRODUCE SIG SNOWMELT. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... SFC FRONTAL BOUNDARY WILL SAG SOUTH OF PA EARLY WEDNESDAY. HOWEVER...LINGERING PRECIP REMAINS LIKELY ACROSS SOUTHERN PA IN REGION OF 8-7H FGEN FORCING. MDL BLYR TEMPS INDICATE PRECIP WILL FALL AS LGT RAIN ACROSS THE SOUTHEAST COUNTIES. HOWEVER...MDL SOUNDINGS JUST COLD ENOUGH TO SUPPORT A RAIN/SNOW MIX ACROSS THE LAUREL HIGHLANDS...WHERE A LIGHT ACCUM OF UP TO AN INCH APPEARS POSSIBLE BY WED EVENING. DRIER AIR ACROSS NORTHERN PA SHOULD TRANSLATE TO A MAINLY DRY DAY THERE WITH JUST A CHC OF -SHSN. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... AN ACTIVE LATE-WINTER PRECIPITATION PATTERN WILL IMPACT CENTRAL PA THROUGH MIDWEEK FOLLOWED BY WHAT IS HOPEFULLY THE LAST SHOT OF ARCTIC AIR FOR THE SEASON THURSDAY INTO FRIDAY. THE PATTERN SHOULD DRY OUT LATE IN THE WEEK THROUGH THE UPCOMING WEEKEND WITH HIGH PRESSURE IN CONTROL MOST OF THE TIME. THE GENERAL MODEL AND ENSEMBLE CONSENSUS IS TO MAINTAIN A RIDGE IN THE WEST AND TROUGH IN THE EAST THROUGH THE WEEKEND WITH SOME SIGNS OF A PATTERN SHIFT BY THE MIDDLE OF NEXT WEEK WITH TROUGHING FCST TO DEVELOP ALONG THE WEST COAST. BELOW NORMAL TEMPS SHOULD MODERATE CLOSER TO NORMAL EARLY NEXT WEEK WITH SOME HINTS AT EVEN WARMER TEMPS LATER NEXT WEEK. MODELS CONTINUE TO SHOW AN AMPLIFIED AND MOIST SW FLOW ALOFT AND JET ENTRANCE REGION DYNAMICS SUPPORTING A BROAD STRIPE OF PCPN ALONG A WELL DEFINED BAROCLINIC ZONE AHEAD OF PHASING UPPER LEVEL ENERGY OVER THE DSW/ROCKIES ON WED AND MOVING EWD THROUGH THE OH VLY AND MID ATLC ON THURSDAY. SEVERAL WAVES OF LOW PRESSURE ARE FCST TO DEVELOP AND MOVE ENEWD ALONG A SW-NE ORIENTED COLD FRONT WHICH SHOULD PROGRESS AND SETTLE SEWD THROUGH THE MID ATLC REGION BY EARLY THURS...AS ARCTIC HIGH PRESSURE BUILDS INTO THE UPPER PLAINS. AMPLE MOISTURE IS FCST BY THE MODELS TO MOVE INTO A DEEPENING COLD SECTOR ALONG/NORTH OF THE SEWD-ADVANCING COLD FRONTAL BOUNDARY WHICH COULD RESULT IN A LATE SEASON HEAVY SNOW EVENT FOR SOUTH CENTRAL PA WED NGT INTO THURS. THERE ARE MODEL DIFFERENCES WITH THE TIMING OF THE FRONT WHICH IS LKLY TIED TO THE CONSOLIDATION OF SHORTWAVE ENERGY UPSTREAM. THAT SAID...THE CONSENSUS FCST AXIS OF MAX QPF /0.50 INCH OR GREATER/ HAS BEEN FAIRLY CONSISTENT PAINTED OVER THE SRN 1/3 OF THE CWA. SIMILAR TO YESTERDAY...USED A MULTI MODEL BLEND WITH PSEUDO BIAS CORRECTION FACTOR TO DERIVE GRIDDED QPF AMTS WHICH GENERALLY RANGE FROM 0.25 TO 0.75 INCHES ACROSS THE SRN 1/2 OF THE CWA. THE COLUMN WILL BE IN A STATE OF TRANSITION AND COOLING DOWN FROM NW TO SE WED-WED NGT AS THE COLD FRONT PUSHES SOUTHEAST ACROSS THE AREA. THIS SHOULD SUPPORT A TRANSITION FROM RAIN TO SNOW. A PERIOD OF SLEET MAY IMPACT FCST SNOW ACCUMULATIONS WITH THE DURATION A KEY FACTOR IN THIS FCST. WITH INCREASING CONFIDENCE AND GREATEST RISK IN THE POTENTIAL FOR HEAVY SNOW/6+ INCHES...WHICH IS SUPPORTED BY ROBUST WPC ENSEMBLE AS WELL AS THE GEFS MEAN...HAVE ISSUED A WINTER STORM WATCH FOR THE SOUTH-CENTRAL COUNTIES FROM WEDNESDAY EVENING THROUGH THURSDAY EVENING. WHAT IS HOPEFULLY THE LAST SHOT OF ARCTIC AIR THIS SEASON SHOULD ARRIVE BEHIND THE COLD FRONT. FRIDAY MORNING LOWS ARE LKLY TO BE 20-30F BELOW NORMAL WITH SINGLE DIGIT LOWS +/- ZERO DEGREES. SUCH READINGS MAY BREAK DAILY RECORDS. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... 03Z TAFS SENT. MAINLY RAIN NOW IN MOST AREAS. EARLIER DISCUSSION BELOW. A WARM FRONT LIFTING NE FROM THE OH VLY WILL KEEP A LARGE AREA OF FREEZING RAIN AND SLEET ACROSS MOST OF THE AREA THIS EVENING. JST WARM ENOUGH FOR JUST RAIN...BUT GROUND AND OBJECT TEMPS LIKELY STILL COLD. THE OTHER FACTOR OVERNIGHT WILL BE LLWS. THE PRECIPITATION WILL LIKELY GO OVER TO JUST RAIN LATE TONIGHT FOR A SHORT TIME. MANY AREAS MAY JUST SEE NOTHING ONCE THE STRONGER WARM ADVECTION SHUTS OFF. FOR WED...RAIN WILL GO BACK TO SNOW FROM NW TO SE. HARD TO SEE CONDITIONS BEING VERY GOOD. VERY COLD LOW LEVEL AIR WILL BE ADVECTED BACK TO THE SOUTH LATE WED INTO THU. A SERIES OF WEAK LOW PRESSURE SYSTEMS WILL TRACK ALONG THE COLD FRONT FROM LATE WED INTO THU...LIKELY GIVING AT LEAST SOUTHERN PA SOME SNOW. THE COMBINATION OF INCREASING WINDS...SNOW...AND FALLING TEMPERATURES WILL LIKELY RESULT IN POOR CONDITIONS FOR AVIATION. IMPROVING CONDITIONS WILL SET IN FOR FRIDAY INTO MONDAY...AS COLD HIGH PRESSURE BUILDS INTO THE AREA. OUTLOOK... WED NIGHT...SIG REDUCTIONS IN SNOW DEVELOPING MAINLY ACROSS THE SOUTH. THU...SLOWLY IMPROVING CONDITIONS...LINGERING MVFR NW AND SE. FRI-SAT...MAINLY VFR. SUN...MVFR WITH CHC -SHSN MAINLY NORTH AND WEST. VFR SE. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 7 AM EST WEDNESDAY FOR PAZ012- 018-019-025>028-034>037-041-042-045-046-049>053-056>059- 063>066. WINTER WEATHER ADVISORY UNTIL 1 AM EST WEDNESDAY FOR PAZ004>006-010-011-017-024. WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY EVENING FOR PAZ024>028-033>036-056>059-063>066. && $$ SYNOPSIS...FITZGERALD NEAR TERM...FITZGERALD SHORT TERM...FITZGERALD/STEINBUGL LONG TERM...STEINBUGL AVIATION...MARTIN

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