Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 101203 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 703 AM EST WED FEB 10 2010 .SYNOPSIS... LOW PRESSURE WILL RAPIDLY INTENSIFY AS IT LIFTS NORTHEAST ALONG THE MIDDLE ATLANTIC COAST TODAY. THIS SYSTEM WILL PRODUCE MODERATE TO HEAVY SNOW OVER MUCH OF CENTRAL PENNSYLVANIA BEFORE TAPERING OFF TONIGHT. COLD AND BLUSTERY CONDITIONS WITH MOUNTAIN SNOW SHOWERS CAN BE EXPECTED IN THE WAKE OF THIS SYSTEM...WHICH WILL PERSIST THROUGH THE END OF THE WORK WEEK. TEMPERATURES WILL REMAIN BELOW NORMAL INTO EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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LATEST STLT ANAL AND PRECIP TRENDS /SPENES/ HAS NOTED SEVERAL INTERESTING FEATURES THAT WILL LIKELY RESULT IN AN INCREASE IN SNOWFALL RATES OVER THE NEXT 3-6 HOURS. THIS FIRST IS A TROWEL IN THE BLENDED TPW IMAGERY INDICATING ATLC MOISTURE BEING PULLED NW ON THE ERN SIDE OF THE UPPER LOW OVR OH/WV. IR STLT CONTINUES TO SHOW EXPANSION OF COOLING CLOUD TOPS OVER WESTERN AND CENTRAL PENN SUGGESTING SNOWFALL RATES MAY BE ON THE INCREASE. THIS MATCHES UP WELL WITH A SPOTTER REPORT FROM CAMBRIA COUNTY WHO OBSERVED 1" IN THE LAST HOUR. PREVIOUS DISCUSSION FOLLOWS. MOISTURE CHANNEL IMAGERY SHOWS POTENT UPPER LOW CROSSING INTO THE CENTRAL APPLCHNS EARLY THIS MORNING...WITH RESPONDING -6MB SFC 3HR PRES FALLS OBSERVED OVR THE DELMARVA AND NJ COAST. AS THE ENERGY ASSOC WITH THE WEAKENING/PRIMARY LOW OVR NW PA TRANSFERS TO THE COAST...EXPECT THE DEVELOPING LOW LEVEL CIRCULATION TO UNDERGO RAPID INTENSIFICATION AND EVENTUALLY DEEPEN TO SUB 980MB /-4 TO -5SD BELOW NORMAL MSLP/ BY 11/00Z. REGIONAL VWP/S INITIALLY SHOWED SLY LLVL FLOW PULLING MSTR NWD INTO THE COLD SECTOR AHEAD OF THE COMPLEX AREA OF LOW PRESSURE EVOLVING OVER THE MIDDLE ATLANTIC STATES. AS OF 10Z...THESE DATA SHOW THE 850MB CIRCULATION BEGINNING TO FORM OVR CHESAPEAKE BAY WHILE WINDS VEER AROUND TO THE WEST/SOUTHWEST ACRS WESTERN PENN. A SURGE OF ARCTIC AIR AND LLVL CAA HAS OVERSPREAD THE UPPER OH VLY IN THE WAKE OF THIS SYS AND IS MOVING INTO SW PA AND THE WV/MD PNHDLS. LOOK FOR TEMPERATURES AND DEWPTS IN THIS AREA TO FALL INTO THE TEENS AND SINGLE DIGITS THIS MORNING WITH WIND CHILLS BRIEFLY DIPPING TO NEAR ZERO. INCREASING LARGE SCALE VERTICAL LIFT AND LOW/MID LVL FGEN ASSOC WITH APPROACHING H5 LOW IS PRODUCING A BROAD AREA OF DEFORMATION SNOWS ACROSS MUCH OF CENTRAL PENN...WHICH HAS INCREASED IN AREAL COVERAGE AND INTENSITY OVER THE LAST SEVERAL HOURS PER REGIONAL RADAR. THE STEADY LIGHT TO MODERATE SNOW WILL CONTINUE THROUGH THE DAYLIGHT HOURS. THE MAIN FOCUS TODAY WILL BE ON THE EXPLOSIVE COASTAL CYCLOGENESIS AND POSSIBLE BLIZZARD CONDITIONS DEVELOPING OVER PORTIONS OF THE LWR SUSQ VLY. ALL MDL GUID IS IN AGREEMENT IN DEVELOPING MODERATE TO HEAVY SNOWS WITHIN COMMAHEAD BAND WRAPPING NWWD OF THE DEEPENING SFC LOW. MEANWHILE...A TIGHTENING PRES GRAD WILL RESULT IN A STEADY INCREASE IN NW WINDS INTO THE AFTN. IF THE INTENSE BANDING CAN REMAIN IN TACT LONG ENOUGH FOR THE WINDS TO KICK IN...THE POTENTIAL EXISTS FOR BLIZZARD CONDITIONS OVR THE LWR SUSQ VLY GIVEN FREQUENT GUSTS TO 35 MPH AND THE HEAVY BANDED SNOWS. AFTER COORDINATION WITH PHI AND LWX...WE HAVE DECIDED TO COVER THIS POTENTIAL HAZARD WITHIN THE BODY OF THE WSW...SPECIFICALLY NOTING THAT NEAR-BLIZZARD/WHITEOUT CONDITIONS ARE POSSIBLE. ELSEWHERE...HAVE ADDED MENTION OF AREAS OF BLOWING (DRIFTING IMPLIED) SNOW TO ACCOUNT FOR THE GUSTY WINDS LATER TDY. ADDITIONAL SNOW ACCUMULATIONS COMPRISED OF A MEAN BLEND OF MDL/HPC QPF AND 12-14:1 SLR/S WILL RANGE FROM 4-8 INCHES OVR THE ENTIRE SUSQ VLY...TO 2-4/3-5 INCHES FURTHER WEST ACROSS THE CENTRAL MOUNTAINS AND LAUREL HIGHLANDS. AS THE DEEP LOW BEGINS TO PULL AWAY FROM THE EASTERN SEABOARD TONIGHT...BRISK AND COLD CYC FLOW WILL KEEP OROGRAPHIC SNOWS GOING OVER THE WESTERN MOUNTAINS. AN ADDITIONAL INCH OR SO OF ACCUMULATION CAN BE EXPECTED MAINLY OVER THE SW MTNS/LAURELS. SNOW WILL TAPER OFF EAST OF THE ALLEGHENIES WITH IMPROVING CONDITIONS TOWARD DAYBREAK THURSDAY.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... PERSISTENT COLD CYC FLOW WILL KEEP OCNL MTN SNOW SHOWERS GOING THIS PERIOD...WHILE AREAS EAST OF THE ALLEGHENY FRONT WILL ONLY SEE A FLURRY OR TWO. HIGHS VERY SIMILAR BOTH THUR AND FRI RANGING FROM THE LOW 20S OVR THE ALLEGHENIES TO THE LOW 30S ACRS THE MID AND LWR SUSQ VLY. THIS IS ABOUT 5 TO 10 DEGREES BELOW EARLY FEB CLIMO. && .LONG TERM /SATURDAY THROUGH TUESDAY/... MDLS ARE IN FAIRLY GOOD AGREEMENT ON THE LONGWAVE PATTERN THIS PD. A MEAN TROUGH IS FCST IN THE EAST WITH SEVERAL UPPER LOWS ROTATING AROUND THE BROAD UPPER VORTEX OVR ERN CANADA. THE CURRENT SYSTEM OFF THE COAST IS FCST TO RETROGRADE WWD BACK ACROSS THE MARITIMES...WHILE A RELATIVELY SMALL BUT STRONG MID LVL CIRC DROPS THROUGH THE UPPER MIDWEST/OH VLY SUN-MON. THE SRN STREAM SYS FOR SAT WILL REMAIN SUPPRESSED AFFECTING THE SOUTHEAST STATES WITH SOME WINTRY WEATHER. THE KEY TO THIS FCST WILL BE UNLOCKING THE COMPLEX PATTERN OVER CANADA AND UPSTREAM. CONFIDENCE IS HIGH IN A PROLONGED COLD SPELL AS ENSEMBLE DATA SHOWS ANOMALOUS 850MB TEMPS COVERING MUCH OF THE ERN CONUS INTO EARLY NEXT WEEK. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... STRONG HEIGHT FALLS WILL RESULT IN A VERY DEEP STORM JUST OFF THE MID ATLANTIC COAST EARLY THIS MORNING. WIDESPREAD IFR CONDITIONS WILL PREVAIL TODAY. BANDS OF HEAVY SNOW HAVE BEEN DEVELOPING AND WILL CONTINUE TO DEVELOP AND LIFT NORTHWARD THIS MORNING. THE SNOW WILL BECOME LIGHTER IN NATURE LATER THIS AFTERNOON...BUT STRONG WINDS WILL DEVELOP BY LATE MORNING...AS COASTAL STORM DEEPENS. GUSTY WINDS WILL LINGER INTO THU. WIND GUSTS THIS AFTERNOON AND EVENING COULD BE IN THE 30 TO 40 MPH RANGE...ESPECIALLY AT MDT. ALREADY BREEZY AT JST. MOST OF THE PERIOD THU INTO SUNDAY WILL BE VFR...GIVEN THAT FLOW WILL BE FROM THE NORTH...BUT SOME UPSLOPE SC WILL BE POSSIBLE AT JST AND BFD. OUTLOOK... THU-SUN...VFR CENTRAL/EAST. MVFR AND SCT -SHSN WEST. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR PAZ010>012-017>019-024>028-033>036-041-042-045-046-049>053- 056>059-063>066. WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR PAZ004>006-037. && $$ SYNOPSIS...STEINBUGL NEAR TERM...STEINBUGL SHORT TERM...STEINBUGL LONG TERM...STEINBUGL AVIATION...MARTIN

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