Area Forecast Discussion
Issued by NWS State College, PA

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000
FXUS61 KCTP 231650
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1150 AM EST FRI JAN 23 2015

.SYNOPSIS...
LOW PRESSURE OVER THE GULF OF MEXICO THIS MORNING WILL TRACK
QUICKLY NORTHEAST ALONG THE EAST COAST TONIGHT...PASSING EAST OF
NEW ENGLAND BY SATURDAY NIGHT. AN ALBERTA CLIPPER WILL TRACK SOUTH
OF PENNSYLVANIA SUNDAY NIGHT. AN UPPER LVL TROUGH WILL REMAIN OVER
THE NORTHEAST CONUS THRU THE REST OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
LATE MORNING VIS SAT LOOP SHOWING SOME SLIGHT EROSION AND NRN
DRIFT TO THE SOUTHERN EDGE OF THE LOW STRATUS/STRATO CU CLOUD DECK
JUST NORTH OF THE I-76 CORRIDOR.

THE SUN ACROSS SRN AND PERHAPS CENTRAL PENN WILL BE QUICKLY HIDDEN
THIS AFTERNOON BY A THICKENING MID/HIGH CLOUD SHIELD FROM THE
SOUTHWEST.

EXPECT THE CLOUD BASES TO LOWER TO 7-10 KFT AGL BY LATE AFTERNOON
ACROSS THE SOUTH...AND THE EVENING HOURS NORTH OF INTERSTATE 80...
IN ADVANCE OF THE RAPIDLY APPROACHING SFC LOW OVR THE SOUTHEAST
CONUS.

WINDS WILL BE LIGHT FROM THE SOUTH TO SW AS SFC HIGH PRESSURE
SLIDES OFF THE DELMARVA COAST.

ENS MEAN 925MB TEMPS ARE SUPPORTIVE OF MAX TEMPS FROM THE U20S OVR
THE NW MTNS...TO THE M/U30S ACROSS THE LOWER SUSQ VALLEY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...

FAST-MOVING LOW WILL TRACK UP THE E COAST LATER TONIGHT...PASSING
JUST EAST OF THE DELMARVA ARND 12Z SAT.

09Z SREF AND 12Z OP MODEL CONSENSUS POINTS TWD A SWATH OF MORE
SIGNIFICANT SNOWFALL OCCURRING NEAR AND A FEW LAYERS OF COUNTIES
TO THE NORTHWEST OF I-81 TONIGHT AND SAT MORNING AS THE SFC LOW
TRACK HAS SHIFTED WESTWARD OVER THE LAST 24HRS DUE TO THE LACK OF
A NOTABLE BLOCKING HIGH TO THE NE AND THE STRENGTH OF THE SRN
STREAM UPPER TROUGH. THEREFORE...HAVE INCREASED POPS AND SNOW AMTS
ACROSS THE REGION TONIGHT. AN ADVISORY TYPE SNOWFALL NOW APPEARS
VERY LIKELY TONIGHT INTO EARLY SAT JUST TO THE SE OF THE ALLEGHENY
FRONT IN CENTRAL PENN /AND ACROSS THE FAR SE/ WHILE LOW END
WINTER STORM WARNING AMOUNTS OF 6-8 INCHES SHOULD FALL ACROSS THE
BULK OF THE REGION BETWEEN I-81 AND THE I99/ROUTE 22O CORRIDOR.
EXPANDED THE PREVIOUS WINT WEATHER ADVISORY NWWD BY A FEW
COUNTIES...AND ISSUED A WINTER STORM WARNING FOR THIS EVENING
THROUGH SAT MORNING FOR THE SCENT MTNS...AND PORTIONS OF THE LWR-
MID SUSQ VALLEY...ALONG WITH THE WRN POCONOS.

LITTLE MDL SPREAD NOTED W/RESPECT TO TIMING OR TRACK...ALL OF
WHICH POINTS TOWARD SNOW ARRIVING ACROSS THE S TIER ARND 00Z AND
REACHING IT/S FURTHEST WESTWARD EXTENT ACROSS THE NW MTNS BY ARND
MIDNIGHT. MDL BLENDED QPF /AND MEDIAN VALUES ON THE 09Z SREF/
RANGES FROM NOTHING OVR WARREN CO...TO PERHAPS 0.75 INCHES OVR
LANCASTER CO. PASSAGE OF SOUTHERLY LL JET LATE TONIGHT WILL DRAW
MILDER AIR INTO SE PA...LIKELY CHANGING PTYPE TO EITHER RAIN OR
FZRA FROM ARND KMDT SOUTH AND EASTWARD. STILL...EXPECT SEVERAL
INCHES OF ACCUM BEFORE ANY CHANGEOVER ACROSS THE SE. FURTHER
NORTH...SNOW/WATER RATIOS ARND 12/1...TYPICAL FOR COASTAL
STORMS...SHOULD TRANSLATE TO SNOW ACCUMS IN THE 2-4 INCH RANGE OVR
THE SOUTHERN HALF OF THE CWA.

BY DAWN SATURDAY...LL JET AND BEST ISENTROPIC LIFT SHOULD HAVE
SHIFTED EAST OF THE REGION. HOWEVER...LIGHTER SNOW ASSOC WITH MID
LVL SHORTWAVE IS LIKELY TO LAST THRU ARND MIDDAY...AND PERHAPS A
BIT LONGER OVR THE SE COUNTIES.

NW FLOW IN WAKE OF THIS SYSTEM SHOULD BRING PARTIAL CLEARING LATE
TO EASTERN PA. HOWEVER...A FAST MOVING AND WEAK CLIPPER TYPE
SHORTWAVE WILL BE DIVING INTO THE REGION FROM THE GRT LKS TOWARD
EVENING...LIKELY PRODUCING -SHSN ACROSS THE ALLEGHENY PLATEAU SAT
EVENING.

THE AIR MASS BEHIND TONIGHT/S LOW IS NOT PARTICULARLY COLD AND
ENS MEAN 925 TEMPS SUPPORT HIGHS IN THE M/U30S OVR MUCH OF THE
AREA...WHICH SHOULD RESULT IN MUCH IMPROVED ROAD CONDS BY SAT AFTN.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
HAVE INCREASED CHC OF SNOW LATE SUNDAY/EARLY MONDAY...AS MED RANGE
MDLS ALL TRACKING POTENT ALBERTA CLIPPER JUST SOUTH OF PA SUN
NIGHT. BLEND OF MED RANGE GUIDANCE SUPPORTS QPF IN THE 0.25 TO
0.50 INCH RANGE...IMPLYING A LIGHT TO MODERATE SNOWFALL. HIGHEST
TOTALS LIKELY TO BE ACROSS SOUTHERN PA BASED ON CURRENT TRACK.
PLENTY OF COLD AIR AVAILABLE AND EXPECT NO PRECIP TYPE ISSUES WITH
THIS EVENT.

AS THE LOW INTENSIFIES OFF THE THE ATLANTIC COAST ON MONDAY...WE
COULD SEE LIGHT SNOW/SHOWERS CONTINUING THROUGH THE DAY WITH
TEMPERATURES REMAINING STEADY OR SLOWLY FALLING THROUGH THE 20S.

COLDEST AIR OF THE WEEK DIVES IN BEHIND THE DEPARTING SYSTEM ON
TUESDAY WITH STATEWIDE HIGHS A FEW DEGREES EITHER SIDE OF 20F.
SUB-ZERO LOWS POSSIBLE ACROSS A GOOD PART OF CENTRAL PA TUESDAY...AS
SFC HIGH BUILDS OVR THE AREA. CLEARING SKIES...A CALM WIND AND
FRESH SNOW COVER COULD RESULT IN AN IDEAL RADIATIONAL COOLING
SCENARIO.

MODERATING CHILL IS IN STORE FOR THE MID TO LATE WEEK...AS
RIDGING AT THE SURFACE AND ALOFT MOVES IN AHEAD OF NEXT IN SERIES
OF ALBERTA CLIPPERS.

&&

.AVIATION /16Z FRIDAY THROUGH TUESDAY/...
LOW PRESSURE OVER THE WESTERN FLORIDA PANHANDLE LATE THIS MORNING
WILL TRACK QUICKLY NORTHEAST ALONG THE EAST COAST TONIGHT...PASSING
EAST OF NEW ENGLAND BY SATURDAY NIGHT. AN ALBERTA CLIPPER WILL
TRACK SOUTH OF PENNSYLVANIA SUNDAY NIGHT.

STUBBORN LAYER OF SHALLOW...LOWER CLOUDS ACROSS CENTRAL AND NRN
PENN LATE THIS MORNING WILL ERODE GRADUALLY NWD DURING THE
AFTERNOON HOURS AS A DECK OF THICKENING HIGH CLOUDS ADVANCES
QUICKLY NE ABOVE THE LOWER LAYER.

MVFR WILL GRADUALLY IMPROVE TO VFR FROM SOUTH TO NORTH.

THE BETTER FLYING CONDITIONS WILL BE SHORT-LIVED THOUGH AS CLOUDS
QUICKLY LOWER AND THICKEN THIS EVENING.

SNOW WILL SPREAD INTO THE SOUTHERN MTNS SHORTLY AFTER 00Z AND
OVERSPREAD REMAINDER OF THE AREA BY LATE EVENING. THE SNOW WILL BE
ACCOMPANIED BY LOWERING CIGS/VSBYS WITH MAJORITY OF TERMINALS
DROPPING TO IFR BY MID EVENING AND LINGERING THROUGH MUCH OF THE
OVERNIGHT. SOME FREEZING RAIN LIKELY WORKS INTO THE SOUTHERN MTNS
AND LOWER SUSQ AFTER MIDNIGHT...WHICH COULD BRING ICING ISSUES.

OUTLOOK...

SAT...REDUCTIONS ARAEWIDE EARLY AS STORM EXITS THE REGION. THEN
IMPROVING CONDITIONS EAST...WITH REDUCTIONS CONTINUING WEST.
BECOMING BREEZY.

SUN...VFR INTO THE AFTERNOON...THEN SNOW DEVELOPING ACROSS THE
WEST IN THE AFTERNOON OR EVENING...AND OVERSPREADING ALL OF
CENTRAL PENN AND THE SUSQ VALLEY AT NIGHT.

MON...AM SNOW WITH WIDESPREAD MVFR TO IFR LIKELY.

TUE...NO SIG WEATHER EXPECTED.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 1 PM EST
SATURDAY FOR PAZ019-024-025-033-042-045-046-064>066.
WINTER STORM WARNING FROM 7 PM THIS EVENING TO 1 PM EST
SATURDAY FOR PAZ026>028-034>036-049>053-056>059-063.

&&

$$
SYNOPSIS...FITZGERALD/LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT/FITZGERALD
LONG TERM...DANGELO/FITZGERALD
AVIATION...LAMBERT/RXR



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