Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 032144 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 444 PM EST TUE MAR 3 2015 .SYNOPSIS... 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. && .NEAR TERM /UNTIL 10 PM THIS EVENING/... 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 VACILLATED 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 ENSEMBLES 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. && .SHORT TERM /10 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... 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. && .LONG TERM /WEDNESDAY 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 /22Z TUESDAY THROUGH SUNDAY/...
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A LARGE AREA OF SLEET AND FREEZING RAIN OVER THE AREA AS OF LATE AFT. MINOR ADJUSTMENTS MADE TO 21Z TAFS. EARLIER DISCUSSION BELOW. WARMER AIR SURGING IN ON INCREASING SW FLOW WILL BRING A PROLONGED WINTRY MIX/FREEZING RAIN EVENT THIS AFTERNOON THROUGH EARLY WEDNESDAY 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... 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 WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY EVENING FOR PAZ024>028-033>036-056>059-063>066. WINTER STORM WARNING UNTIL 7 AM EST WEDNESDAY FOR PAZ005-006- 011-012-018-037-041. && $$ SYNOPSIS...DEVOIR NEAR TERM...DEVOIR SHORT TERM...DEVOIR LONG TERM...STEINBUGL AVIATION...DEVOIR/MARTIN/RXR

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