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-- Discussion containing changed information from previous version are highlighted. --
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/...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.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