Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 250726
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
226 AM EST THU DEC 25 2014

.SYNOPSIS...
INTENSE LOW PRESSURE WILL MOVE ACROSS SOUTHERN ONTARIO THIS
MORNING AND PUSH ITS SOUTHWARD TRAILING COLD FRONT EAST OF THE
AREA BY DAYBREAK. BANDS OF SHOWERS WILL OCCUR ALONG AND AHEAD OF
THE FRONT...FOLLOWED BY DRIER BUT WINDY CONDITIONS FOR THE REST OF
TODAY. A LARGE AREA OF HIGH PRESSURE WILL BUILD NORTHEAST FROM THE
GULF COAST REGION BRINGING FAIR WEATHER WITH LIGHTER WIND FOR
TONIGHT AND FRIDAY. A WEAK COLD FRONT WILL DRIFT ACROSS THE STATE
SATURDAY...FOLLOWED BY A WEAK WAVE OF LOW PRESSURE RIDING
NORTHEAST ALONG IT BRINGING A FEW PERIODS OF RAIN SATURDAY NIGHT
AND SUNDAY.
&&

.NEAR TERM /UNTIL 8 AM THIS MORNING/...
SHARP COLD FRONT HAS PUSHED JUST EAST OF THE SUSQ MAINSTEM ATTM.
AREA OF LIGHT TO MDT SHOWERS WITH GUSTY WEST WINDS BETWEEN 40-50
MPH WAS OCCURRING ALONG AND JUST IN THE WAKE OF THE SFC CFRONT.

THERE WILL BE A FEW TO SVRL HOUR LULL IN THE WIND /AND PRECIP
ACROSS THE WRN MTNS/ THROUGH THE MID MORNING HOURS AS A WEAK RIDGE
OF HIGH PRESSURE FOLLOWS THE FRONT. TEMPS EARLY TODAY WILL DROP
THROUGH THE 40S ACROSS THE EASTERN ZONES...AND THROUGH THE 30S
ACROSS THE WESTERN MTNS.

&&

.SHORT TERM /8 AM THIS MORNING THROUGH 6 PM FRIDAY/...
THIS CHRISTMAS DAY WILL BRING A TRANSITION INTO A PRETTY TYPICAL
POST FRONTAL COOL SEASON PATTERN...WITH CLOUDS AND BLUSTERY GUSTY
WESTERLY WINDS. HIGHER ELEVATIONS WILL LIKELY SEE GUSTS AS HIGH AS
40-45 MPH...WHILE BUKFIT DATA IMPLIES TOP WIND GUSTS IN THE
35-40MPH RANGE FOR THE REST OF US.

COLDER AIR ALOFT AND SLIGHTLY CYCLONIC FLOW AT THE SFC WILL LEAD
TO SOME SNOW SHOWERS ACROSS THE WESTERN MTNS BETWEEN 12-19Z AS THE
BASE OF THE SUBSIDENCE INVERSION RISES TO 4-6 KFT AGL. THE HEIGHT
OF THIS INVERSION BASE CRASHES TO BETWEEN 2-3 KFT AGL BY 00Z
FRIDAY...CUTTING OFF THE SNOW SHOWERS AND HELPING TO TRIM THE
WINDS /AND PEAK GUSTS/ BY 10 KTS OR MORE.

THE CENTRAL RIDGE-VALLEY REGION WILL EXPERIENCE LITTLE MORE THAN
A PASSING LIGHT RAIN OR SNOW SHOWER TODAY. AGAIN...THE FALLING
INVERSION HGTS WITH APPROACH OF SFC RIDGING FROM THE SOUTHWEST
LATER TODAY SHOULD CAUSE ANY MTN SNOW SHOWERS TO TAPER OFF DURING
THE AFTN AND RESULT IN SOME BREAKS IN THE CLOUD COVER...ESP ACROSS
THE LOWER SUSQ VALLEY.

WITH SFC TEMPS EXPECTED TO BE ABV FREEZING EVERYWHERE /AND ONLY IN
THE MID TO UPPER 30S ACROSS THE WESTERN MTNS/...THE LIGHT SNOW
SHOWERS ARE NOT EXPECTED TO ACCUMULATE...EXCEPT FOR PERHAPS A
DUSTING OVR THE HIGHEST RIDGETOPS.

ENS MEAN 925/850 TEMPS SUPPORT HIGH TEMPS TODAY RANGING FROM THE
M30S OVR THE ALLEGHENY MTNS...TO THE U40S ACROSS THE LOWER SUSQ
VALLEY.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
POTENT LONGWAVE UPPER TROF EXITING THE EAST COAST AT THE START OF
THE PERIOD WILL BE REPLACED BY UPPER RIDGING INTO THE WEEKEND. AS
LONGWAVE UPPER TROFFING IS FORECAST TO DEVELOP OVER THE WRN US
STARTING EARLY IN THE PD AND NRN STREAM ENERGY RETREATS INTO
EASTERN CANADA...MDT TO STRONG SWRLY FLOW ALOFT IS THEN FORECAST
TO DOMINATE THE EASTERN CONUS FROM LATE IN THE WEEKEND THROUGH THE
REMAINDER OF THE YEAR.

MEDIUM RANGE GUIDANCE IS FAIRLY CONSISTENT ESPECIALLY EARLY IN
THE PERIOD...BUT THEN SOME DIFFERENCES ARISE IN 500MB FLOW
PATTERN AFTER MONDAY AS THE ECMWF MOVES ENERGY EAST FASTER...WHILE
THE GFS CLOSES OFF AN UPPER LOW OVER THE DESERT SW.

A NORTHERN STREAM WAVE IS FORECAST TO SUPPORT A COLD FRONT MOVING
EAST ACROSS THE STATE LATE IN THE WEEKEND...POSSIBLY STALLING
NEAR THE MASON DIXON LINE INTO MONDAY AS IT ENCOUNTERS RESISTANCE
FROM THE BUILDING UPPER FLOW. THIS FRONT LOOKS TO BE THE MAIN
FOCUS FOR PCPN IN THE LONG TERM PERIOD. WITH SNOW TO THE NORTH AND
WEST...AND A MIX TO RAIN ACROSS THE SOUTH.

WITH RIDGING OR SWRLY FLOW ALOFT MUCH OF THE PERIOD WILL FEATURE
ABOVE NORMAL TEMPS...WITH A COOL DOWN TOWARD NORMAL BY NEW YEARS
EVE.

&&

.AVIATION /07Z THURSDAY THROUGH MONDAY/...
03Z TAFS SENT.

STRONG DRY PUNCH AND WIND FIELDS HAVE RESULTED IN 49 KNOT
GUST AT DUJ. GUSTY WINDS WILL BE THE MAIN ISSUE OVERNIGHT.

LOW CIGS STILL ACROSS MUCH OF THE AREA...WITH LLWS.

WINDS WILL SLOWLY DIE DOWN DURING THE DAY ON THU.

LOW CIGS WILL PERSIST THE FIRST PART OF CRHISTMAS ACROSS THE
AREA. EXPECT CONDITIONS TO BECOME VFR LATER IN THE DAY.

NOT LOOKING BAD INTO FRIDAY AND SAT.

OUTLOOK...

FRI...MAINLY VFR.

SAT...VFR.

SUN-MON...MVFR TO IFR WITH SCATTERED RAIN AND SNOW SHOWERS.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY UNTIL NOON EST TODAY FOR PAZ004>006-010>012-017-
018-024-033.

&&

$$
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT/FITZGERALD
LONG TERM...LAMBERT/GARTNER
AVIATION...MARTIN



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