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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 100132
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
832 PM EST TUE FEB 9 2010

.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL SLIDE TOWARD THE REGION TONIGHT AND
RAPIDLY REDEVELOP AND INTENSIFY JUST OFF THE MIDDLE ATLANTIC
COAST BY WEDNESDAY MORNING. THIS SYSTEM WILL PRODUCE MODERATE TO
HEAVY SNOW OVER MUCH OF CENTRAL PENNSYLVANIA BEFORE TAPERING OFF
WEDNESDAY NIGHT. COLD AND BRISK CONDITIONS WITH MOUNTAIN SNOW
SHOWERS CAN BE EXPECTED IN THE WAKE OF THIS SYSTEM...WHICH WILL
LIKELY PERSIST INTO THE UPCOMING WEEKEND.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
-- Changed Discussion --
OUR LATEST WINTER STORM IS SOLIDLY IN TRANSITION AS SECONDARY
DEVELOPMENT IS REALLY TAKING OFF JUST EAST OF THE CAPE HATERAS
AREA WHERE 3-HOUR PRESSURE FALLS ARE EXCEEDING 5 MB. INITIAL SURGE
OF WARM ADVECTION SNOWFALL HAS PRODUCED A RESPECTABLE SWATH OF 3
TO 6 INCH SNOWS THIS EVENING ACROSS THE SOUTHERN TIER WITH SOMERSET...
FRANKLIN...ADAMS AND YORK COUNTIES ALL GETTING INTO THE ACT THIS
EVENING.

5H LOW IS NOW PROGRESSING THROUGH THE LOWER OHIO VALLEY...WITH WV
IMAGERY INDICATING ENHANCEMENT AND INCREASED UPWARD VERTICAL
MOTION OVER SOUTHEAST OH...WV AND FAR SOUTHWEST PA. THIS TREND
WILL CONTINUE THROUGH THE OVERNIGHT...WITH STRONG DEFORMATION
DEVELOPING ACROSS CENTRAL AND SOUTH CENTRAL PA AND A LARGE SNOW
SHIELD SUBSEQUENTLY DEVELOPING AFTER 06Z AS THE COASTAL CONTINUES
TO ORGANIZE AND LIFT NORTHWARD TOWARDS THE DEL MARVA. AS THIS
OCCURS...CENTRAL PA SHOULD SEE SEVERAL HOURS OF MODERATE TO HEAVY
SNOWFALL ACCOUNTING FOR MUCH OR MOST OF THE ACCUMULATION NORTH OF
THE SOUTHERN TIER COUNTIES.

MOST DIFFICULT PART OF THE EVENING IS PATIENTLY WATCHING THIS ALL
EVOLVE AS WE EXPECT IT WILL. NOT MAKING MANY CHANGES AT PRESENT
BUT WILL BE MONITORING THE EVOLUTION CLOSELY THROUGH THE LATE
EVENING.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH 6 PM WEDNESDAY/...
POTENT STORM SYSTEM BEGINNING TO AFFECT PENNSYLVANIA LATE THIS
AFTERNOON AS STRONG UPPER ENERGY SLIDES IN FROM THE WEST. THIS
ENERGY WILL BEGIN TO SHIFT TO THE COAST AND RAPIDLY DEEPEN A
COASTAL LOW TONIGHT WHICH WILL BRING A HIGH IMPACT SNOW EVENT TO
EASTERN PA...MAINLY TO LOCATIONS ALONG AND SE OF I-81...AND
SLIGHTLY LESSER AMOUNTS TO CENTRAL AND WEST. THE POTENTIAL
BULLSEYE OF HIGHEST AMOUNTS FROM NEAR HARRISBURG EAST TO NEAR
PHILLY AND ALLENTOWN.

INCREASING ATLC/ELY INFLOW /WHICH IS FCST TO STRENGTHEN TO +4SD
ABOVE NORMAL/ COMBINED WITH STRONG DYNAMICS ASSOC WITH THE
APPROACHING MID/UPPER LOW WILL SUPPORT MOD TO HVY SNOW ACROSS THE
REGION WED MORNING INTO THE AFTN. AS THE 850MB CIRCULATION
TIGHTENS UP OVER CHESAPEAKE BAY AND THE DELMARVA...IT WILL BE
ACCOMPANIED BY AN INTENSE CONVERGENCE/DIVERGENCE COUPLET SFC AND
ALOFT WITHIN THE EXIT REGION OF A 170KT JET MAX ROUNDING THE BASE
OF THE CLOSED MID LVL LOW CENTER TAKING ON A SLGT NEG TILT AS IT
MOVES OFFSHORE. DEEP LYRD WAA AND FGEN FORCING WILL FAVOR STRONG
UVM IN A 5-6 KM LAPSE RATE ENVIRONMENT...WITH THE HIER RES NAM AND
WRF MDLS SUGGESTING SNOWFALL RATES UP TO 2" AN HOUR OVR PARTS OF
THE MID AND LWR SUSQ VLY BTWN 12-18Z IN ONE OR MORE PIVOTING NE-SW
ORIENTED MESOSCALE BANDING STRUCTURES.

SREF/GEFS ENSEMBLE PLUMES ARE IN LINE WITH GRIDDED STORM TOTAL
SNOWFALL AMOUNTS...WITH AN INCREASING TREND NOTED IN THE LAST FEW
RUNS. IN GENERAL...A BLEND OF MDL QPFS YIELDS 24HR /18ZTUE-18ZWED/
LIQUID EQUIVALENTS OF OVER AN INCH IN THE FAR SE TO ROUGHLY 0.50"
ACROSS THE NW MTNS. FINAL SNOWFALL AMOUNTS WERE COMPRISED OF AN
AVERAGE OF 10-14:1 SLR/S RESULTING IN MAX AMOUNTS OVER A FOOT
/12-18"/ ALONG AND SE OF INTERSTATE 81. HOWEVER...MAXIMIZED
LIFT/OMEGAS VIA BUFKIT APPEAR TO BE LOCATED JUST BELOW THE FAVORED
DGZ. THIS SUGGESTS SOME AGGREGATION WHICH MAY LEAD TO A WETTER
SNOW AND COULD CUT DOWN SLIGHTLY ON ACCUMS. AS THE LOW CONTINUES
TO DEEPEN AS IT MOVES AWAY FROM LI...XPC NORTH TO NORTHWEST GRAD
WINDS TO INC TO 15-25MPH WITH HIGHER GUSTS...LKLY LEADING TO
BLOWING AND DRIFTING OF THE SNOW.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
POTENT WINTER STORM WILL BE HEADED AWAY FROM PA BY WED
NIGHT...LEAVING A MESS BEHIND. BIGGEST STORY FOR WED NIGHT INTO
THU WILL BE STIFF AND GUSTY NORTHWEST WINDS CREATING BLOWING SNOW
AND CHILLY CONDITIONS. TEMPS WON/T SEE A BIG DROP OFF BEHIND THE
STORM...BUT WINDS WILL BRING WIND CHILLS INTO THE SINGLE DIGITS
WED NIGHT INTO THU. MUCH OF THE REGION WILL BEGIN A PERIOD OF
PRECIPITATION-FREE WEATHER WITH PERSISTENT NORTHWEST FLOW...BUT
THE HIGHER ELEVATIONS OF THE WEST AND NORTH WILL SEE MAINLY LIGHT
SNOW SHOWERS DUE TO UPSLOPE FLOW. AN OCCASIONAL SNOW SHOWER COULD
SLIP INTO THE CENTRAL MOUNTAINS DURING THIS TIME...BUT MUCH OF THE
TIME WILL BE DRY.

TEMPS WILL SEE LITTLE CHANGE AS WE PROGRESS THROUGH THE
WEEK...WITH TEMPS GENERALLY AVERAGING A COUPLE OF DEGREES BELOW
NORMAL. POTENTIAL FOR SOME LIGHT SNOW EARLY NEXT WEEK...SO EDGED
POPS UP ABOVE NORMAL FOR THAT TIME FRAME.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
A STORM APPROACHING FROM THE OHIO VALLEY...WILL REDEVELOP ALONG
THE MID ATL COAST AND BRING WIDESPREAD MODERATE TO HEAVY SNOWS
ALONG WITH IFR CONDITIONS. FOR THE OVERNIGHT EXPECT CEILINGS TO
DETERIORATE TO BETWEEN 500-1500` WITH VISIBILITIES AVERAGING AROUND
A MILE...FREQUENTLY DOWN TO 1/4-1/2 MILE IN HEAVIER SNOW BANDS. THE
LOW CONDITIONS WILL LAST WELL INTO WED BEFORE CONDITIONS BEGIN TO
IMPROVE LATE IN THE DAY AND EVENING.

WEDNESDAY WILL ALSO SEE INCREASING WIND GUSTS OUT OF THE NW...TO
BETWEEN 20 AND 30 MPH BY AFTERNOON WHICH WILL LIKELY CAUSE BLOWING
AND DRIFTING SNOW...KEEPING REDUCED VISIBILITIES A PROBLEM INTO
WED NIGHT.

OUTLOOK...
WED...MAINLY IFR...WITH PERIODS OF LIFR IN SN.
THUR- SAT...MVFR TO VFR CENTRAL/EAST. MVFR AND SCT -SHSN WEST.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 7 PM EST WEDNESDAY 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 WEDNESDAY FOR
PAZ004>006-037.

&&

$$
SYNOPSIS...BEACHLER/STEINBUGL
NEAR TERM...DEVOIR/GARTNER
SHORT TERM...RXR
LONG TERM...RXR
AVIATION...LA CORTE