Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 030743 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 243 AM EST TUE MAR 3 2015 .SYNOPSIS... HIGH PRESSURE CENTERED OVER THE REGION WILL DRIFT EAST TO THE SOUTHERN NEW ENGLAND COAST BY THIS AFTERNOON. AN AREA OF LOW PRESSURE OVER THE CENTRAL PLAINS STATES WILL MOVE QUICKLY NORTHEAST TO THE UPPER GREAT LAKES BY TONIGHT. A SURGE OF DEEP MOISTURE AHEAD OF THIS LOW WILL RIDE UP AN OVER THE COLD AIR IN PLACE ACROSS PENNSYLVANIA AND LEAD TO ANOTHER ROUND OF SIGNIFICANT WINTRY/MIXED PRECIPITATION THIS AFTERNOON INTO EARLY TONIGHT. THE PRECIPITATION WILL LIKELY TURN TO RAIN ACROSS SOUTHERN SECTIONS EARLY WEDNESDAY. COLDER TEMPERATURES WILL FOLLOW FOR THE LATTER PART OF THE WEEK...AND SNOW WILL RETURN WEDNESDAY EVENING INTO THURSDAY AS A WAVE OF LOW PRESSURE RIPPLES ALONG A NEARLY STATIONARY FRONT THAT WILL BE DRAPED JUST TO OUR SOUTH. HIGH PRESSURE AND COLD AIR WILL RETURN FOR FRIDAY INTO THE FIRST PART OF THE WEEKEND. && .NEAR TERM /UNTIL 10 AM THIS MORNING/... SFC HIGH PRESSURE /1032 MB/ WAS CENTERED OVER THE WESTERN SOUTHERN TIER OF NEW YORK AT 07Z AND WILL BE DRIFTING EAST ALONG THE PENN/NEW YORK BORDER THROUGH SUNRISE. THIN CIRRUS STREAMING TWD THE WRN MTNS OF PENN WILL QUICKLY LOWER AND THICKEN UP DURING THE MID TO LATE MORNING HOURS TODAY...BUT NOT BEFORE THE DAMAGE HAS BEEN DONE WITH RESPECT TO SOLIDIFYING A VERY COLD BOUNDARY LAYER PRIMED FOR SUPPORTING SNOW THIS AFTERNOON...THEN AN EXTENDED PERIOD OF MIXED PRECIP LATE TODAY AND TONIGHT. MORE DETAILS ON THAT BELOW IN THE SHORT TERM SECTION OF THE DISCUSSION. EARLY MORNING LOWS WITH WINDS GOING LIGHT AND VARIABLE WILL BE IN THE SINGLE DIGITS BELOW ZERO ACROSS THE NW MTNS...IN THE LOWER TO MID TEENS THROUGHOUT THE CENTRAL RIDGE AND VALLEY REGION OF THE STATE...AND UPPER TEENS TO AROUND 20F IN THE SOUTHEAST. STILL EXPECT PRECIP ONSET FROM THE SOUTHWEST TO HOLD OFF UNTIL AFTER 15Z/10AM. && .SHORT TERM /10 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... CONDITIONS WILL GO DOWNHILL FAIRLY QUICKLY ON TODAY 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 THIS AFTERNOON...FOLLOWED BY A SIGNIFICANT BOUT OF MIXED PRECIP/FREEZING RAIN LATER THIS AFTERNOON THROUGH EARLY TONIGHT. 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. WINTER WEATHER ADVISORIES CONTINUE FOR A PERIOD OF SNOW/SLEET ACCUM...FOLLOWED BY FREEZING RAIN...GENERALLY FROM MIDDAY TODAY THROUGH THE EARLY MORNING HOURS ON WEDNESDAY. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... AN ACTIVE LATE-WINTER PATTERN WILL AFFECT 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 CONSENSUS IS TO MAINTAIN A RIDGE IN THE WEST AND TROUGH IN THE EAST...LIMITING TEMPERATURE MODERATIONS TO NO BETTER THAN CLIMATE NORMALS. MODELS SHOW AN ACTIVE PCPN ZONE EXTENDING FROM THE SRN PLAINS ENEWD INTO THE NRN MID ATLANTIC STATES...IN BTWN A POSITIVELY TILTED TROUGH PUSHING THROUGH THE PLAINS/MIDWEST/GREAT LAKES AND ABOVE NORMAL RIDGING FROM THE GOMEX INTO THE WRN ATLANTIC OCEAN. SEVERAL WAVES OF LOW PRESSURE ARE FCST TO MOVE ALONG A SW-NE ORIENTED COLD FRONT WHICH SHOULD SLOWLY PROGRESS EWD TOWARD THE COAST WED-THUR AS NRN STREAM ENERGY CROSSES THE GREAT LAKES. THERE ARE SOME DIFFERENCES WITH MODEL QPF BUT THE CONSENSUS POINTS TOWARD THE SRN PA FOR THE HIGHEST PCPN AMTS. USED A MULTI MODEL BLEND WITH PSEUDO BIAS CORRECTION FACTOR TO DERIVE GRIDDED QPF AMTS WHICH CONSERVATIVELY 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 FROM NW TO SE WED-WED NGT AS THE COLD FRONT PUSHES EAST. THIS SHOULD SUPPORT A GENERAL TRANSITION FROM RAIN TO SNOW ACROSS THE CWA. WITH A DECENT AMOUNT OF MSTR AVAILABLE/STRIPE OF ABOVE NORMAL PW LOCATED JUST SOUTH OF PA...THE POTENTIAL EXISTS FOR MODERATE TO HEAVY SNOW OVER THE SRN PORTIONS OF THE AREA. HOWEVER GIVEN THE UNCERTAINTY AT DAY 3-4 RANGE IN THE FRONTAL WAVES AND THERMAL PROFILES IN A STATE OF FLUX GOING FROM WARM TO COLD...CONFIDENCE IN BIG AMOUNTS IS QUESTIONABLE. FOR NOW THE DAY 3+4 NUMBERS RANGE FROM 0-2" NORTH OF I-80...2-4" FROM I80 TO THE PA TURNPIKE/I-81 AND AMOUNTS IN EXCESS OF 4" POSSIBLE ALONG/S OF THE TURNPIKE/I-81. THIS IS SUBJECT TO CHANGE AS ANY SLIGHT SHIFT IN THE QPF AXIS IS PLAUSIBLE AT THIS POINT. THE TAKEAWAY HERE IS THAT WINTER WX WILL LKLY CONTINUE TO IMPACT THE AREA THROUGH MIDWEEK WITH THE GREATEST RISK FOR HEAVY SNOW OVER THE SRN PORTIONS OF THE CWA. WHAT IS HOPEFULLY THE LAST SHOT OF ARCTIC AIR SHOULD ARRIVE BEHIND THE COLD FRONT THURSDAY WITH SINGLE DIGIT LOWS +/- OF FRIDAY MORNING. MAY BE THE COLDEST MORNING UNTIL NEXT WINTER. SOME SNOW SHOWERS ARE POSSIBLE OVER THE WEEKEND WITH A REINFORCING COLD FRONT. TEMPS WILL REMAIN AT OR BELOW AVG THROUGH THE PERIOD. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... MINOR ADJUSTMENTS MADE TO 03Z TAFS. EARLIER DISCUSSION BELOW. LOOKING AT JUST A FEW CLDS OVERNIGHT WITH VFR CONDITIONS. WINDS WILL DIE DOWN IN ANOTHER HOUR OR TWO. A FAST MOVING SYSTEM MOVING ACROSS THE GREAT LAKES WILL PULL WARM AIR INTO THE AREA LATE TUE. SNOW WILL QUICKLY MOVE IN DURING THE AFTERNOON AND MIX WITH AND CHANGE TO A MIXTURE OF FREEZING RAIN...SNOW...AND SLEET BY LATE TUE AFT AND EARLY EVENING...BEFORE CHANGING TO RAIN LATE TUESDAY NIGHT INTO EARLY WED. A FEW RAIN SHOWERS WILL BE ACROSS THE AREA ON WED. AS COLDER AIR WORKS BACK TO THE SOUTH LATE WED INTO EARLY THU...LOW PRESSURE MOVING NE ALONG THE FRONT WILL LIKELY RESULT IN A NASTY MIXTURE OF PRECIPITATION. POTENTIAL IS THERE FOR HEAVY WET SNOW AND SIGNIFICANT FREEZING RAIN AS WELL. IMPROVING CONDITIONS FOR LATE THU. OUTLOOK... 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 THIS AFTERNOON TO 7 AM EST WEDNESDAY FOR PAZ006-011-012-018-037-041-042. WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 4 AM EST WEDNESDAY FOR PAZ004-005-010-017-024>026-033>035. WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 4 AM EST WEDNESDAY FOR PAZ019-027-028-036-045-046-049>053-056>059- 063>066. && $$ SYNOPSIS...LAMBERT/DANGELO NEAR TERM...LAMBERT SHORT TERM...LAMBERT/DANGELO LONG TERM...STEINBUGL AVIATION...MARTIN

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