Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 250526 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1226 AM EST TUE NOV 25 2014 .SYNOPSIS...
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A COLD FRONT WILL PUSH EAST OF THE AREA OVERNIGHT. HIGH PRESSURE WILL BUILD NORTHEAST FROM THE OHIO RIVER VALLEY TUESDAY WITH FAIR AND COOLER CONDITIONS. AN AREA OF LOW PRESSURE WILL MOVE NORTHWARD ALONG THE EAST COAST...BRINGING A CHANCE OF SIGNIFICANT SNOW TO THE EASTERN HALF OF PENNSYLVANIA ON WEDNESDAY. ANOTHER SHOT OF COLD AIR WILL FOLLOW FOR NEXT WEEKEND.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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THE COLD FRONT HAS CLEARED ALL BUT THE EXTREME SERN PORTION OF MY CWA AS OF MIDNIGHT. THE LARGER PICTURE SHOWS A SHIELD OF HIGH CLOUDS STREAMING NNE UP THE EASTERN SEABOARD IN RESPONSE TO A SHEARING OUT SHORTWAVE EMBEDDED IN THE FAST SWLY FLOW ALOFT. IT`S STILL PRETTY GUSTY FOR THIS HOUR OF THE NIGHT...BUT THE PRESSURE GRADIENT WILL GRADUALLY SLACKEN OVERNIGHT SO THE WIND WILL BEGIN TO ABATE. FROM EARLIER... FAIRLY STRONG SFC-850 MB CAA /CURRENTLY PUSHING ACROSS THE ALLEGHENY PLATEAU OF WRN PENN/ WILL SPREAD ACROSS THE EASTERN TWO THIRDS OF THE CWA LATE TONIGHT...HELPING TO DROP TEMPS THROUGH THE 50S AND 40S. MODEL CONSENSUS-ALL BLEND INDICATES LOW TEMPS OF 30-32F ACROSS THE NW MTNS AND LAUREL HIGHLANDS...WITH UPPER 30S AND LOWER 40S ACROSS THE SUSQ VALLEY. THE LEADING EDGE OF AN AREA OF EXTENSIVE /BUT QUITE SHALLOW/ DECK OF STRATO CU WILL SPREAD OVER THE WESTERN MTNS BETWEEN 04-06Z TUESDAY...FOLLOWED BY SOME FLURRIES AND ISOLATED SNOW SHOWERS THROUGH THE MORNING HOURS TUESDAY. THE CLOUD DECK SHOULD BE SCT-OCNLY BKN ACROSS THE CENTRAL MTNS LATE TONIGHT...WHILE MAINLY CLEAR SKIES WILL PERSIST ACROSS MUCH OF THE SOUTHERN TIER.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... STRONG CAA ON TUESDAY AS A MINOR HIGH PRESSURE BUILDS IN FROM THE W/SW. CLOUDS AND SCT SHSN IN THE FAR NW WILL KEEP TEMPS VERY COOL...AND THEY MAY NOT RISE AT ALL IN THE NW. BUT THE REST OF THE STATE WILL HAVE MORE SUNSHINE AND THE SE WILL GET SOME DOWNSLOPING. EVEN SO...DIURNAL RANGES OF 10F ARE ABOUT ALL THAT THE SE WILL MANAGE ON TUESDAY. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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POTENTIAL FOR SIG WINTER IMPACTS FROM LOW PRESSURE MOVING UP THE EAST COAST ON WED/WED NIGHT. WILL CONTINUE TO INJECT INTERPRETATION OF THE LATEST MODEL GUIDANCE WITH EACH 3-HOURLY UPDATE TO GUIDE DECISION SUPPORT LEADING UP TO THE PRIME TRAVEL PERIOD FOR THE THANKSGIVING HOLIDAY. FOCUS IN LONG TERM CONTINUES TO BE POTENTIAL FOR SIG IMPACTS FROM A LOW PRESSURE SYSTEM QUICKLY DEEPENING AND SLIDING UP THE EAST COAST ON WED. TROUGH SLIDING THROUGH CENTRAL U.S. TODAY WILL SWING TOWARD THE EAST COAST AS A WAVE OF LOW PRESSURE IS BORN OVER FLORIDA ON TUES. THE LOW WILL DEEPEN AS IT TRACKS NORTHWARD JUST OFF THE EASTERN SEABOARD...PASSING BY THE NJ COAST BY 00Z THU AS A STILL DEEPENING 998MB LOW. FORECAST CONFIDENCE IN DEVELOPMENT OF THIS LOW REMAINS VERY HIGH...WITH FAIR AMOUNT OF UNCERTAINTY PERSISTING IN EXACT TRACK OF THE LOW WHICH WILL IMPACT ASSOCIATED SNOW/RAIN AMOUNTS. THE TAKEAWAY FROM THE 12Z MODEL SUITE IS THAT THE WESTWARD DRIFT OF THE TRACK EVIDENT IN DATA OVER THE PAST SEVERAL DAYS HAS STOPPED...WITH ECMWF CONTINUING TO FORECAST THE TRACK WEST OF THE GFS/GEFS. VARIATIONS IN QPF FIELDS CONTINUE...BUT SETTLING IN ON AROUND A QUARTER INCH FROM KJST-KIPT TO CLOSER TO 0.75 IN THE LOWER SUSQ VALLEY. PRECIP SHOULD SLIDE IN FROM THE SOUTH BEFORE SUNRISE ON WED AS WEAK HIGH PRESSURE LIFTS NORTHWARD AS STORM APPROACHES. NORTHERLY FLOW OVER CENTRAL PA NOT PARTICULARLY STRONG IN ANY MODEL...BUT A SHORTWAVE LOOKS POISED TO SLIDE IN FROM THE GREAT LAKES ON WED TO ADD SOME SYNOPTIC LIFT TO THE RAPIDLY DEEPENING AND FAST MOVING SURFACE LOW. AIR MAY BE WARM ENOUGH AT ONSET IN FAR SE COUNTIES TO BEGIN PRECIP AS RAIN OR A MIX OF RAIN/SNOW. BUT COOLING OF THE COLUMN WILL CHANGE PRECIP OVER TO ALL SNOW...WITH HIGHEST TOTALS MOST LIKELY EAST OF A KAOO-KUNV-KIPT LINE WHICH LOOKS TO INCLUDE THE HARRISBURG METRO AREA. ENOUGH CONFIDENCE AT THIS POINT FOR A HIGH IMPACT EVENT /ON THE BUSIEST TRAVEL DAY OF THE YEAR/ TO ISSUE A WATCH FOR SE HALF OF CWA. BIGGEST IMPACTS WILL BE POTENTIAL FOR A SEVERAL HOUR PERIOD OF HEAVY ACCUMULATING SNOW DURING THE DAY WED. BUT AGAIN...SMALL CHANGES IN THE ULTIMATE TRACK COULD LEAD TO MODIFICATIONS OF SNOWFALL FORECASTS. THE TAKE AWAY...THOUGH THE DETAILS REMAIN FLUID...THERE WILL BE SIG IMPACTS TO TRAVEL ALONG THE U.S. EAST COAST ON ONE OF THE BUSIEST DAYS OF THE YEAR /WED/. PLAN ACCORDINGLY. COLDER AIR REMAINS IN PLACE LATE IN THE WEEK AS SCT SNOW SHOWERS RETURN TO THE WESTERN HIGHER TERRAIN. TEMPS LOOK TO GRADUALLY MODIFY STARTING THIS WEEKEND HEADING INTO NEXT WEEK AS MID LEVEL FLOW FLATTENS AND THEN BROAD RIDGE DEVELOPS OVER EASTERN 2/3 OF U.S. WE COULD BE BRUSHED BY A COUPLE WEAK SYSTEMS...BUT NO ADDITIONAL BIG STORM SYSTEMS EXPECTED AFTER THANKSGIVING.
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&& .AVIATION /05Z TUESDAY THROUGH SATURDAY/... GUSTY WINDS OF EARLY THIS EVENING HAVE DIMINISHED...AS LOW PRES OVR SOUTHERN QUEBEC MOVES AWAY FROM THE REGION. SATL LOOP SHOWS STRATOCU APPROACHING NW PA AT 03Z. CAN/T RULE OUT A PERIOD OF MVFR CIGS AT KBFD LATE TONIGHT AND EARLY TUE AM. HOWEVER...MDL SOUNDINGS NOT MAKING A CONVINCING CASE FOR IT. HIGH CONFIDENCE IN WIDESPREAD VFR CONDS HOLDING THRU TUESDAY...AS A RIDGE OF HIGH PRES AND DRY AIR WORK IN FROM THE OHIO VALLEY. ONLY POSS EXCEPTION WOULD BE KBFD...WHERE OROGRAPHIC LIFT COULD CONCEIVABLY SUPPORT OCNL MVFR CIGS. OUTLOOK... WED...SNOW/LOW VSBYS SOUTHEAST HALF OF PA. THU...AM FOG POSS SOUTH. EVENING -SHSN/REDUCED VSBYS POSS W MTNS. FRI-SAT...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES...
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WINTER STORM WATCH FROM LATE TONIGHT THROUGH WEDNESDAY EVENING FOR PAZ025>028-034>036-056>059-063>066. WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY NIGHT FOR PAZ019-042-045-046-049>053.
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&& $$ SYNOPSIS...DANGELO/LA CORTE/LAMBERT NEAR TERM...LA CORTE/LAMBERT SHORT TERM...DANGELO LONG TERM...RXR AVIATION...FITZGERALD

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