Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 031925 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 225 PM EST TUE MAR 3 2015 .SYNOPSIS...
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MIXED PRECIPITATION WILL CHANGE TO AN EXTENDED PERIOD OF FREEZING RAIN THIS EVENING THROUGH LATE TONIGHT. THE PRECIPITATION WILL LIKELY TURN TO RAIN ACROSS SOUTHERN AND FAR WESTERN 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.
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&& .NEAR TERM /UNTIL 10 PM THIS EVENING/...
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AT MID AFTERNOON...PRECIPITATION TRANSITION IS WELL UNDERWAY WITH INITIAL BURST OF SNOW HAVING PUSHED INTO THE MIDDLE TO LOWER SUSQ RIVER VALLEY. SNOW AND SLEET WILL HAVE CHANGED OVER TO PRIMARILY FREEZING RAIN BY EARLY EVENING. HRRR HAS VASCILLATED CONSIDERABLY FROM HOUR TO HOUR...BOTH WITH QPF AND OVERNIGHT TEMPERATURES...AND THUS AM BASING THE ICE FORECAST AND ITS ASSOCIATED NEAR- TO SHORT- TERM CHANGES ON SHORT RANGE ENSEMBES AND IN PARTICULAR SREF THREATS WHICH CONSECUTIVELY HAVE INDICATED 80% OR GREATER CONFIDENCE IN .25"+ OF ICE ACCRETION FROM LATE THIS AFTERNOON THROUGH THE EARLY MORNING HOURS (PAST MIDNIGHT) OF WEDNESDAY. WILL UPGRADE TO WINTER STORM WARNINGS (THERE IS STILL SOME SNOW/SLEET BEFORE THE COMPLETE CHANGEOVER) FOR ICE ACROSS THE NORTH CENTRAL MOUNTAINS...WHERE GREATER THAN 0.25" OF ICE IS EXPECTED. FARTHER WEST...A CHANGEOVER TO RAIN IS EXPECTED OVER WARREN AND ELK COUNTIES...HOLDING DOWN AMOUNTS ALONG THE WESTERN BORDERS OF THOSE COUNTIES. THE WARNING AREA MAY NEED TO BE EXPANDED FARTHER SOUTH INTO THE CENTRAL MOUNTAINS IN TIME...BUT CONFIDENCE IN DOING SO SOUTH OF INTERSTATE 80 WAS LOW GIVEN CONFLICTING HRRR LLVL TEMPERATURE READINGS AND QPF DISTRIBUTION THROUGH LATE TONIGHT. THE REST OF THE SOUTHERN THIRD OF CENTRAL PA IS SEEING A SEVERAL HOUR LULL IN PRECIP AT MID AFTERNOON AS A RESULT OF A DRY SLOT WHICH FOLLOWED THE INITIAL WAA BURST. PRECIP FILLING IN BEHIND IS FZRA OVER THE LAURELS AND HEADING INTO THE CENTRAL MOUNTAINS WITH A FEW REPORTS STILL OF SOME SLEET PELLETS MIXED IN. NEAR TERM DETAILS APPEAR TO BE IN GOOD SHAPE. EVE SHIFT WILL CONT TO MONITOR EVOLUTION OF QPF AND ADJUST ICE AMOUNTS AS NECESSARY.
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&& .SHORT TERM /10 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
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PROLONGED ICE ACCRETION IS THE MAIN THREAT LATE TONIGHT INTO WEDNESDAY MORNING THROUGHOUT THE CENTRAL AND NRN MTNS OF THE STATE. BY LATE TONIGHT...WARM AIR WILL BE FLOODING THE SOUTH AND CHANGING FZRA OVER TO PLAIN RAIN. THE NORTH MAY NOT COMPLETELY MIX OUT THE SHALLOW AND INITIALLY QUITE 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 0.20-0.30 OF AN INCH ACROSS THE NCENT MTNS OF PA WHERE ADVISORIES ARE BEING UPGRADED TO WARNINGS...WITH LESSER AMOUNTS IN MOST PLACES TO THE SOUTH OF INTERSTATE 80.
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&& .LONG TERM /WEDNESDAY 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 /19Z TUESDAY THROUGH SUNDAY/...
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WARMER AIR SURGING IN ON INCREASING SW FLOW WILL BRING A PROLONGED WINTRY MIX/FREEZING RAIN EVENT THIS AFTERNOON THROUGH EARLY WEDNESADY MORNING ACROSS MUCH OF CENTRAL PA. SNOW/SLEET WILL CHANGE TO FREEZING RAIN SOUTH THIS AFTERNOON...AND EVEN PLAIN RAIN ACROSS THE LAUREL HIGHLANDS AND SOUTH CENTRAL MOUNTAINS AND LOWER SUSQUEHANNA RIVER VALLEY BY THIS EVENING. FARTHER NORTH...COLD AIR WILL REMAIN LOCKED OVER THE NORTH CENTRAL MOUNTAINS MAINTAINING FREEZING RAIN THROUGH EARLY WEDNESDAY MORNING. AS A RESULT...WIDESPREAD SIGNIFICANT RESTRICTIONS TO CIGS/VSBYS WILL ACCOMPANY THIS STORM AT ALL TERMINALS FOR AN EXTENDED PERIOD FROM THIS AFTERNOON THROUGH LATE TONIGHT. LLWS WILL ALSO BE PREVALENT 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. SUN...MVFR WITH CHC -SHSN MAINLY NORTH.
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&& .CTP WATCHES/WARNINGS/ADVISORIES...
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WINTER WEATHER ADVISORY UNTIL 7 AM EST WEDNESDAY FOR PAZ004- 010-017-019-024>028-033>036-042-045-046-049>053-056>059- 063>066. WINTER STORM WARNING UNTIL 7 AM EST WEDNESDAY FOR PAZ005-006- 011-012-018-037-041.
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&& $$ SYNOPSIS...DEVOIR NEAR TERM...DEVOIR SHORT TERM...LAMBERT LONG TERM...LAMBERT/STEINBUGL AVIATION...DEVOIR/RXR

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