Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 252334 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 634 PM EST TUE NOV 25 2014 .SYNOPSIS... HIGH PRESSURE WILL RETREAT TO THE NORTHEAST TONIGHT. LOW PRESSURE FORMING OFF THE SOUTHEAST COAST WILL DEEPEN SIGNIFICANTLY AS IT MOVES NORTHEASTWARD ALONG THE EAST COAST ON WEDNESDAY...BRINGING SIGNIFICANT SNOW TO MUCH OF CENTRAL PENNSYLVANIA. ANOTHER SHOT OF COLDER AIR WILL FOLLOW FOR THE END OF THE WEEK...BEFORE TEMPERATURES MODERATE OVER THE WEEKEND AND INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... HIGH CLOUDS THINNING OUT THIS AFTERNOON ABOVE WEAK RIDGE OF HIGH PRESSURE WHILE STRATOCU PERSIST OVER NW MTNS BACK TOWARD THE COLDER AIR OVER THE GREAT LAKES. OVERALL NOT A BAD DAY FOR LATE NOVEMBER IN CENTRAL PA AS TEMPS PEAKED SEVERAL DEGREES ABOVE NORMAL /THOUGH NOTABLY COOLER THAN MON/...WITH A BREEZY W/SW WIND. WINDS WILL DECREASE QUICKLY HEADING INTO THIS EVENING AS PRESSURE GRADIENT CONTINUES TO WEAKEN. LIMITED CLOUDS EARLY WILL ALLOW TEMPS TO SLIP INTO THE 20S BEFORE LEVELING OUT OVERNIGHT. OVER PAST 24H...MODEL GUIDANCE HAS COME INTO GOOD AGREEMENT ON EVOLUTION OF DEVELOPING LOW PRESSURE AREA BEING BORN ALONG THE GA/SC COAST IN RESPONSE TO A POTENT SHORTWAVE APPROACHING FROM THE MISSISSIPPI VALLEY. THE GFS/GEFS HAS TRENDED WESTWARD WHILE THE EC LOOKED TO TAKE JUST A SLIGHT LEAN EASTWARD...WITH THE RESULT NOW BEING A GOOD CONSENSUS ON LIKELY SURFACE LOW TRACK. THE SYSTEM ALOFT TAKES ON A NEG TILT AS IT MOVES UP THE EASTERN SEABOARD...WITH THE SURFACE LOW MADE TO TRACK ALONG THEN JUST OFFSHORE OF THE EAST COAST WEDNESDAY. FOR THE OVERNIGHT...PRECIP OVERSPREADING THE SOUTHERN TIER COUNTIES QUICKLY AFTER 08Z...WITH QPF APPROACHING A TENTH OF AN INCH BY 12Z. TEMPS ALOFT AND ON THE SURFACE SUGGEST THAT PRECIP STARTING OVER SOUTHERN /ESPECIALLY SE/ AREAS LATE TONIGHT WILL LIKELY BE AT LEAST A MIX OF RAIN AND SNOW WITH LIGHT SNOW ON THE NORTHERN EDGE. SIMPLY...PRECIP WILL MOVE INTO SOUTHERN HALF OF CWA BEFORE SUNRISE AND WILL BE LIGHT...BUT QUICKLY INTENSIFY DURING THE MORNING RUSH HOUR ACROSS THE SOUTH. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... WINTER STORM WARNINGS/ADVISORIES NOW IN EFFECT. A LOW PRESSURE SYSTEM DEVELOPS AND INTENSIFIES AS IT TRACKS FROM THE CAROLINA COAST AT 12Z WED TO OFF THE NJ COAST BY 00Z THU... BRINGING BIGGEST IMPACTS TO CENTRAL PA DURING THE DAY WED. CONFIDENCE IS GROWING IN THE STORM TRACK WITH GFS COMING IN LINE WITH THE ECMWF CLOSER TO THE COAST...WHICH WILL PUSH THE QPF SHIELD A BIT FURTHER WEST. PRECIP WILL BE ONGOING IN THE SOUTH BY SUNRISE...AND SPREADING QUICKLY INTO THE CENTRAL AND NORTHEAST BY MID MORNING. ANY RAIN WILL QUICKLY CHANGE TO SNOW IN THE SE AS COLUMN COOLS. PERIOD OF HEAVIEST INTENSITY PRECIP WILL BE WED MORNING THROUGH MID AFTERNOON...WHERE SNOW RATES COULD BE 1-2 INCHES PER HOUR IN THE WARNING AREA. LATEST WWD GRAPHICS CONTINUE TO SHOW A SWATH OF 6-8 SNOWS OVER THE SERN 1/3 OR SO OF MY FCST AREA. CONFIDENCE FOR SIG SNOWS UP INTO CENTRAL/NW PA NOT AS HIGH GIVEN THE LACK OF A SIG EASTERLY LOW LEVEL WIND ANOMALY IN THE ENSEMBLES...AND A SHORTWAVE SLIDING IN FROM THE WEST WHICH MAY SHARPEN GRADIENT OF SNOW. BUT FOR A COUPLE INCHES OF SNOW AND IMPACTS ON THE BUSIEST TRAVEL DAY OF THE YEAR WE STRUNG AN ADVISORY OVER THE NORTHERN EDGE OF THE WARNING AREA. SNOW SHOULD TAPER OFF QUICKLY BY LATE WED AFT/WED EVE AS STORM QUICKLY MOVES INTO NEW ENGLAND. FLOW TRANSITIONS BACK TO A NW FETCH ACROSS THE LAKES...WITH LIGHT SCT SNOW SHOWERS POSS BY THU MORNING IN THE UPSLOPE OF THE WESTERN HIGHER TERRAIN. && .LONG TERM /THURSDAY THROUGH TUESDAY/... UPPER TROFFING OVER THE EASTERN THIRD OF THE COUNTRY AT THE START OF THE LONG TERM PERIOD IS FORECAST TO FLATTEN OUT INTO AN EXTENSIVE WEST TO EAST ZONAL FLOW PATTERN COVERING MUCH OF NORTH AMERICA. HEIGHTS OVER THE NORTHEASTERN U.S. ARE THEN FORECAST TO RISE FROM LATE IN THE WEEKEND ONWARD AS THE CABOOSE IN THE CURRENT SHORTWAVE TRAIN EXITS THE EAST COAST ON FRIDAY AND ENERGY APPROACHING THE PACIFIC COAST CLOSES OFF AND BUILDS HEIGHTS OVER THE WESTERN AND CENTRAL U.S. A SHOT OF COLD AIR WILL MOVE INTO THE REGION FOR THURSDAY AND FRIDAY BEHIND THE AFOREMENTIONED CABOOSE SHORTWAVE. THIS WAVE MAY ALSO SUPPORT AN AREA OF PCPN MOVING WEST TO EAST ACROSS THE STATE THANKSGIVING DAY. ADDITIONALLY...THIS PUSH OF ENERGY/COLD AIR SHOULD GENERATE THE USUAL POST FRONTAL LAKE AND OROGRAPHICALLY ENHANCED SNOW SHOWERS IN THE WAKE OF THE DEPARTING STORM SYSTEM WITH WESTERN AND NORTHERN AREAS SEEING THE BEST CHANCE OF SCATTERED LIGHT SNOWS...WHILE THE REST OF THE REGION SEES LITTLE OR NO SNOW SHOWER ACTIVITY AT ALL. A BROAD WSW FLOW ALOFT ASSOCIATED WITH THE RISING HEIGHTS WILL MAKE THIS COLD SHOT TEMPORARY WITH WARMER AIR BEGINNING TO MAKE A RETURN BY SATURDAY. HIGHS WILL RETURN TO NEAR OR EVEN A TICK ABOVE NORMAL BY THE WEEKEND BEFORE COOLER AIR APPROACHES AGAIN FOR EARLY NEXT WEEK. A FRONTAL SYSTEM IN ADVANCE OF THE WARM AIR WILL MOVE ACROSS THE STATE ON SUNDAY...BRINGING THE BEST CHANCE OF PCPN DURING THE PERIOD. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... LOW PRESSURE DEVELOPING OFF THE SOUTHEAST COAST LATE TONIGHT WILL STRENGTHEN AS IT LIFTS NWD JUST OFF THE EAST COAST THROUGH WED NGT. EXPECT RAPIDLY DETERIORATING CONDS FROM SOUTH TO NORTH DURING THE PREDAWN AND EARLY MORNING HOURS AS SNOW OVERSPREADS THE AIRSPACE. PCPN WILL LKLY BEGIN AS A MIX IN THE MDT/LNS AREA BEFORE CHANGING TO ALL SNOW. MOST INTENSE SNOWFALL RATES AND REDUCED VSBYS WILL BE OVER THE SERN AIRSPACE WITH RATES UP TO 2"/HR WITH FLGT CATS AOB AIRFIELD MINS. HIGH CONFIDENCE IN WIDESPREAD IFR CONDS DUSK-DAWN BEFORE SNOW ENDS FROM SW TO NE BY WED NGT. LOW CIGS SHOULD PERSIST OVER THE WRN 1/3 OF THE AREA WED NGT WITH MARGINAL IMPROVEMENT ELSEWHERE. OUTLOOK... THU...IFR/MVFR WITH OCNL -SHSN WRN 1/3. VFR TO MVFR CIGS CNTRL/EAST. FRI...AM MVFR/-SHSN NW...OTHERWISE BCMG VFR. SAT-SUN...MAINLY VFR. -SHRA PSBL. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER STORM WARNING FROM 3 AM WEDNESDAY TO 4 AM EST THURSDAY FOR PAZ019-042-045-046-049>053. WINTER WEATHER ADVISORY FROM 3 AM WEDNESDAY TO 4 AM EST THURSDAY FOR PAZ012-017-018-037-041. WINTER STORM WARNING FROM 3 AM WEDNESDAY TO MIDNIGHT EST WEDNESDAY NIGHT FOR PAZ024>028-033>036-056>059-063>066. && $$ SYNOPSIS...RXR/STEINBUGL NEAR TERM...RXR SHORT TERM...RXR LONG TERM...LA CORTE/GARTNER AVIATION...STEINBUGL

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