Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 021911 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 211 PM EST MON MAR 2 2015 .SYNOPSIS... HIGH PRESSURE WILL MOVE ACROSS THE REGION TONIGHT. AN AREA OF LOW PRESSURE AND FRONTAL SYSTEM WILL TRACK WEST OF PENNSYLVANIA LATE TUESDAY AND EARLY WEDNESDAY...BRINGING ANOTHER ROUND OF SIGNIFICANT WINTRY/MIXED PRECIPITATION TO THE REGION TUESDAY AFTERNOON INTO EARLY TUESDAY NIGHT...AND CHANGING TO RAIN BY EARLY WEDNESDAY ACROSS SOUTHERN SECTIONS. COLDER TEMPERATURES WILL FOLLOW FOR THE LATTER PART OF THE WEEK...AND ANOTHER ROUND OF PRECIPITATION MAY FALL AS SNOW WEDNESDAY NIGHT INTO THURSDAY AS A SECOND WAVE OF LOW PRESSURE RIPPLES ALONG THE FRONT. HIGH PRESSURE AND TRANQUIL CONDITIONS WILL RETURN FOR FRIDAY INTO THE FIRST PART OF THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... WATER VAPOR LOOP SHOWS SHARP UPPER TROF HAS MOVED OFF THE NORTHERN MID ATLANTIC COAST AND SHORTWAVE RIDGING IS BUILDING OVER THE OHIO VALLEY. SCT-BKN STRATUS IS DECREASING OVER THE NORTHWEST AND WEST CENTRAL MOUNTAINS WHILE THE SOUTHEAST ANDSOUTH CENTRAL MOUNTAINS ARE CLEAR. WINDS ARE GUSTY THROUGHOUT...WITH METARS INDICATING 25 TO 28 KT GUSTS ACROSS MOST OF CENTRAL PA. HIGH PRESSURE WILL BUILD ACROSS THE REGION TONIGHT BEFORE MOVING OFFSHORE EARLY TUESDAY. WINDS WILL SLACKEN NICELY BY LATE EVENING ACROSS MOST OF CENTRAL PA...LEADING TO A CHILLY NIGHT. MINS WILL RANGE FROM THE SINGLE DIGITS ABOVE ZERO NORTHWEST TO THE MID TEENS SOUTH. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... CONDITIONS WILL GO DOWNHILL FAIRLY QUICKLY ON TUESDAY WITH MOISTURE FROM BAJA MONSOONAL FLOW ADVECTING THROUGH THE OHIO VALLEY AND ARRIVING INTO THE ALLEGHENIES BY LATE MORNING IN THE FORM OF SNOW INITIALLY...SPREADING EASTWARD ACROSS MY CWA THROUGH THE MIDDAY AND EARLY AFTERNOON HOURS. VERY MILD BOUNDARY LAYER FLOW WILL BRING A QUICK MIX AND EVENTUAL CHANGEOVER TO FREEZING RAIN FOR ALL AS THE DAY PROGRESSES. THERE MAY BE A COMPLETE CHANGEOVER TO RAIN ACROSS THE FAR SOUTH AND SOUTHEAST. CONSENSUS BLEND OF 12Z OPERATIONAL MODELS AND ENS GUIDANCE IS CONSISTENT WITH PREVIOUS SOLUTIONS FOR AN INITIAL FEW TO SEVERAL HOUR PERIOD OF SNOW/SLEET TUESDAY...FOLLOWED BY A SIGNIFICANT BOUT OF MIXED PRECIP/FREEZING RAIN TUESDAY AFTERNOON THROUGH EARLY TUESDAY NIGHT. OVERALL IT APPEARS THAT PROLONGED ICE ACCRETION IS THE MAIN THREAT...PRECEDED BY THE COATING TO 1 INCH OF SNOW FAR SOUTH AND 1 TO 2 INCHES OF SNOW IN MOST AREAS (WITH UP TO 3 INCHES NORTH). THE NORTH MAY NOT COMPLETELY MIX OUT...AND EXPECT AREAS OF FREEZING RAIN TO PERSIST THERE THROUGH THE PRE DAWN HOURS ON WEDNESDAY. ICE ACCUMS SHOULD BE ON THE ORDER OF 0.10-0.20 OF AN INCH ACROSS THE NCENT MTNS OF PA...WITH LESSER AMOUNTS IN MOST PLACES TO THE SOUTH OF INTERSTATE 80. IN COLLABORATION WITH ALL SURROUNDING OFFICES...WINTER WEATHER ADVISORIES HAVE BEEN ISSUED FOR A PERIOD OF SNOW/SLEET ACCUM FOLLOWED BY FREEZING RAIN...GENERALLY FROM MIDDAY TUESDAY THROUGH THE EARLY MORNING HOURS ON WEDNESDAY. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... RAIN SHOULD TAPER OFF TO SCATTERED SHOWERS WITH THE PASSAGE OF THE TRAILING COLD FRONT EARLY WEDNESDAY. FOR WED...TOOK SNOW SHOWERS OUT OF THE NW. TIGHT THICKNESS PATTERN ACROSS THE AREA...SUPPORT A LARGE TEMPERATURE GRADIENT FROM NW PA TO SE PA. THERE COULD BE A FEW SHOW SHOWERS ACROSS THE FAR NW...BUT IT LOOKS LIKE MAINLY NW OF OUR AREA. LEFT POPS UP...THINK FRONT WILL BE SLOW TO MOVE OUT. IN FACT...THE 00Z EC AND FRESH IN 06Z NAM BOTH HIGHLIGHT A WEAK WAVE OF LOW PRESSURE...AND EXTENSIVE RIBBON OF DEEP MOISTURE... STREAMING NE ALONG THE NEARLY STALLED-OUT FRONT /JUST SOUTH OF THE MASON/DIXON LINE...AND OHIO RIVER/. THIS WILL GREATLY COMPLICATE THE WEATHER FOR THE LATE WED INTO THURSDAY TIMEFRAME WITH THE POTENTIAL FOR A LIGHT-MDT SNOWFALL ACROSS SE THIRD TO HALF OF PENN. AFTER THE AFOREMENTIONED WAVE OF LOW PRESSURE SCOOTS BY TO OUR NE...A PUSH OF ARCTIC AIR WILL BRING TEMPS AND POPS BACK WELL BELOW NORMAL FOR LATE THURSDAY INTO FRIDAY. THE ONLY GOOD THING SEEMS TO BE EACH ARCTIC SHOT IS A LITTLE LESS POTENT THAN THE LAST AS WE LEAVE THE RECORD COLD OF FEBRUARY BEHIND. && .AVIATION /19Z MONDAY THROUGH SATURDAY/... WNW FLOW OVER CENTRAL PA WITH WINDS 10-20 MPH WITH GUSTS TO AROUND LOCALLY OVER 30 MPH. MVFR CIGS AND OROGRAPHICALLY INDUCED LIGHT SNOW/FLURRIES WILL DIMINISH BY LATE AFTERNOON. VFR CONDS PREVAILING ELSEWHERE. WINDS GRADUALLY DIMINISH TONIGHT AS WE/LL SEE A BRIEF RESPITE UNTIL THE NEXT SYSTEM PUSHES ANOTHER ROUND OF PRECIPITATION AND REDUCED FLYING CONDITIONS INTO THE AREA LATER TUESDAY AND WEDNESDAY. OUTLOOK... TUE...VFR AM. MIXED WINTRY PRECIP WITH CIG/VIS REDUCTIONS AND LLWS DEVELOPING LATE AFT AND LASTING THROUGH TUE NIGHT. WED...CIG/VIS REDUCTIONS CONTINUE IN WINTRY MIX/RAIN. THU...SLOWLY IMPROVING CONDITIONS...LINGERING MVFR NW AND SE. FRI-SAT...MAINLY VFR. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY FROM 3 PM TUESDAY TO 7 AM EST WEDNESDAY FOR PAZ006-011-012-018-037-041-042. WINTER WEATHER ADVISORY FROM 1 PM TUESDAY TO 4 AM EST WEDNESDAY FOR PAZ004-005-010-017-024>026-033>035. WINTER WEATHER ADVISORY FROM 3 PM TUESDAY TO 4 AM EST WEDNESDAY FOR PAZ019-027-028-036-045-046-049>053-056>059- 063>066. && $$ SYNOPSIS...DEVOIR NEAR TERM...DEVOIR SHORT TERM...DEVOIR LONG TERM...LAMBERT/MARTIN AVIATION...DEVOIR/RXR

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