Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 031108 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 608 AM EST TUE MAR 3 2015 .SYNOPSIS... HIGH PRESSURE CENTERED OVER THE THE POCONO MOUNTAINS EARLY TODAY 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 STEADY 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 NOON TODAY/... SFC HIGH PRESSURE /1030 MB/ WAS CENTERED OVER NORTHEASTERN PENNSYLVANIA AND WILL BE DRIFTING EAST ACROSS THE LOWER HUDSON RIVER VALLEY DURING THE LATE MORNING HOURS. CIRRUS SHIELD HAS OVERSPREAD ALL OF THE CWA AND THICKENED-UP SUBSTANTIALLY OVER THE PAST FEW HOURS. REGIONAL 88D MOSAIC LOOP SHOWS PLENTY OF 10-20 DBZ RETURNS MOVING QUICKLY EAST INTO THE WESTERN PORTIONS OF OUR CWA.HOWEVER...SFC OBS CONFIRM NOTHING MORE THAN A FEW FLURRIES OR LIGHT SLEET PELLETS REACHING THE GROUND ALL THE WAY BACK THROUGH OHIO AND WVA. EXPECT CONDITIONS TO CHANGE RATHER QUICKLY LATE THIS MORNING AND EARLY THIS AFTERNOON /PER LATEST RAP AND HRRR/ AS AN ANOMALOUSLY STRONG 50-60 KT 850 JET /SREF/ TRANSPORTS A PLUME OF DEEP MOISTURE UP AND OVER THIS DOME OF LLVL COLD AIR. ONLY SOME MINOR CHANGES /UPWARD ADJUSTMENTS/ WERE MADE TO THE POPS FOR TODAY WITH LITTLE OR NO CHANGE IN THE ONSET OF THE PRECIP. EARLY MORNING LOWS WITH WINDS LIGHT AND VARIABLE WERE IN THE SINGLE DIGITS ABOVE AND BELOW ZERO ACROSS THE NRN 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 /NOON TODAY THROUGH 6 PM WEDNESDAY/... CONDITIONS WILL GO DOWNHILL FAIRLY QUICKLY TODAY WITH AN ANTICYCLONIC ARC OF DEEP MOISTURE FROM BAJA MONSOONAL FLOW ADVECTING THROUGH THE OHIO VALLEY AND ARRIVING INTO/BLOSSOMING OVER THE ALLEGHENIES BY LATE THIS MORNING IN THE FORM OF SNOW INITIALLY...SPREADING EASTWARD ACROSS MY CWA THROUGH THE MIDDAY AND EARLY AFTERNOON HOURS. VERY MILD UPPER 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 00Z-06Z OPERATIONAL MODELS AND ENS GUIDANCE IS STILL 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 THROUGHOUT THE CENTRAL AND NRN MTNS OF THE STATE /AND TO A LESSER DEGREE ACROSS THE MID AND LOWER SUSQ VALLEY/...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 THE SHALLOW AND INITIALLY BITTERLY COLD AIR...SO 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 /12Z TUESDAY THROUGH SATURDAY/... VFR CONDITIONS WILL PERSIST INTO THE MID/LATE MORNING HOURS AS HIGH PRESSURE QUICKLY CEDES TO AN APPROACHING WINTER STORM SYSTEM. WINDS THROUGH MID MORNING WILL BE LESS THAN 5 MPH. A FAST MOVING SYSTEM MOVING ACROSS THE GREAT LAKES WILL QUICKLY SPREAD SNOW/SLEET INTO WESTERN SECTIONS BY NOON AND ACROSS ALL OF CENTRAL PA BY MID AFTERNOON. WARMER AIR SURGING IN ON INCREASING SW FLOW WILL BRING A TRANSITION TO A WINTRY MIX/FREEZING RAIN EVENT BY LATE AFTERNOON INTO THE EARLY EVENING...BEFORE CHANGING TO RAIN /FZRA EAST/ LATE TONIGHT INTO EARLY WED. WIDESPREAD SIGNIFICANT RESTRICTIONS TO CIGS/VSBYS WILL ACCOMPANY THIS STORM AT ALL TERMINALS FOR AN EXTENDED PERIOD STARTING LATE THIS MORNING/EARLY THIS AFTERNOON. LLWS WILL ALSO DEVELOP AS 850MB WINDS INCREASE TO AROUND 50 KTS. LATE WED/EARLY THURS AS COLDER AIR WORKS BACK TO THE SOUTH...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. OUTLOOK... WED...SOME IMPROVEMENT TO CONDITIONS BUT SOME REDUCTIONS WILL CONTINUE /ESP SOUTH/ IN RAIN TRANSITIONING BACK TO SNOW LATER IN THE DAY. WED NIGHT...SIG REDUCTIONS IN SNOW DEVELOPING MAINLY ACROSS THE SOUTH. 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 NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...LAMBERT/STEINBUGL AVIATION...RXR

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