124
FXUS61 KCTP 172025
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
325 PM EST TUE DEC 17 2024
SYNOPSIS
* SUNSHINE AND MILD FOR THE REST OF TODAY THEN A CLEAR EVENING
FOLLOWED BY INCREASING CLOUDS LATE TONIGHT
* MORE PRECIPITATION WEDNESDAY AFTERNOON INTO THURSDAY MORNING
WITH RAIN LIKELY SOUTH OF I-80 AND SNOW OR A WINTRY MIX ACROSS
THE NORTHERN MOUNTAINS
* A CLIPPER WILL BRING MORE LIGHT SNOW ON FRIDAY AND LEAVE
BEHIND A CONSIDERABLY COLDER STRETCH OF WEATHER FOR THE
WEEKEND.
NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/
DEEP LAYER DRY ADVECTION BEHIND A WEAK SURFACE COLD FRONT FRONT
MOVING INTO EASTERN PA HAS FINALLY HELP TO CLEAR OUT THE
STUBBORN FOG AND STRATUS DECK TRAPPED BENEATH A RELATIVELY
STRONG INVERSION ACROSS THE SUSQ VALLEY.
PUSHING WILL BE
PUSHING THROUGH THE LOWER AND MID SUSQ VALLEY SHORTLY AND WILL
HELP TO IMPROVE THE LOW, IFR- LIFR CIGS AND VSBYS THERE OVER THE
NEXT 2 HOURS.
ELSEWHERE, WEAK RIDGING FROM THE OHIO VALLEY AND SUBSIDENCE
BENEATH THE LEFT ENTRANCE REGION OF A JETLET MOVING OVER THE
PA/MD BORDER WILL HELP TO MAINTAIN MAINLY CLEAR SKIES THIS
EVENING FOLLOWED BY GRADUALLY INCREASING/THICKENING HIGH CLOUDS
LATER TONIGHT.
HIGH PRESSURE MOVING OVERHEAD TONIGHT WILL SUPPORT LIGHT WINDS
AND EVEN SOME FOG DEVELOPMENT. HIGHEST PROBABILITIES FOR FOG ARE
ON THE RIDGETOPS ACROSS THE NORTHERN TIER AND IN THE SUSQ
VALLEY.
LOWS BY WEDNESDAY MORNING WILL GENERALLY BE WITHIN A FEW DEGREES
OF 30F.
SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/
A BROAD AND WELL-DEFINED JET ENTRANCE REGION WILL SUPPORT THE
ENE MOVEMENT OF A RATHER WEAK SFC LOW FROM THE LOWER OHIO RIVER
VALLEY TO NEAR THE MASON/DIXON LINE WEDNESDAY AFTERNOON.
RELATIVELY SHALLOW COLD AIR TO THE NORTH OF THE LOW TRACK WILL
SUPPORT A FEW PERIODS OF STEADY COLD RAIN ACROSS THE SOUTHERN
1/2 TO 1/3 OF THE STATE, WHILE SOME GLOPPY SNOWFLAKES WILL
LIKELY BE MIXED IN WITH THE RAIN AND REACH THE GROUND NEAR THE
I-80 CORRIDOR AS WET BULB ZERO C HEIGHTS WILL BE RIGHT AROUND
1KFT AGL.
LOW SNOW/LIQUID RATIOS ACROSS THE NORTHERN MTNS WILL LEAD TO A
SLUSHY INCH OR TWO ACROSS THE HIGHER TERRAIN, WHILE VALLEY FLOOR
TEMPS IN THE MID TO UPPER 30S WILL LEAD TO MINIMAL ACCUMS.
QPF SHOULD RANGE FROM A QUARTER OF AN INCH ACROSS THE NORTHERN
TIER TO AROUND HALF AN INCH IN THE SOUTH.
THE ARRIVAL OF PRECIPITATION ON WEDNESDAY MORNING WILL BE AN
IMPORTANT DETAIL TO MONITOR AS AN EARLIER ONSET COULD GENERATE A
RISK FOR SOME FREEZING RAIN. WARMER AIR MOVING IN OVER TOP OF
COOLER VALLEYS IN CENTRAL PA WOULD LEAD TO THE POTENTIAL FOR
SLICK SPOTS ON UNTREATED AND ELEVATED SURFACES. AT THIS POINT,
IT APPEARS PRECIPITATION WILL OVERSPREAD LATER IN THE DAY AND
LEAD TO A LESSER RISK FOR FREEZING RAIN, BUT IT IS WORTH
MONITORING.
HIGHS WEDNESDAY AFTERNOON WILL GENERALLY RANGE FROM THE UPPER
30S TO MID 40S WITH SOME DOWNSIDE POTENTIAL IN A COLD AIR
DAMMING SCENARIO.
AFTER THE LOW SCOOTS EAST OF THE REGION, WINDS WILL SHIFT TO
NORTHWESTERLY OVERNIGHT WEDNESDAY AND GENERATE POTENTIAL FOR
SOME LAKE EFFECT/UPSLOPE SNOW INTO THE DAY ON THURSDAY. SNOW
ACCUMULATION WILL BE LIGHT AND CONFINED PRIMARILY TO THE TYPICAL
SNOW BELT AND UPSLOPE SNOW REGIONS.
LONG TERM /THURSDAY THROUGH MONDAY/
THE WINDOW FOR LAKE EFFECT SNOW SHOWERS OVER NW PA EXTENDS INTO
MIDDAY THURSDAY WITH GENERALLY LIGHT ACCUMS EXPECTED. A MOISTURE
CHALLENGED CLIPPER SYSTEM DROPPING THROUGH THE UPPER MIDWEST
THURSDAY AND THURSDAY NIGHT WILL INITIATE WAA BY LATER THURSDAY
SHUTTING OFF THE LAKE EFFECT, BUT BRINGING A POTENTIAL PERIOD
OF LIGHT SNOW OR SNOW SHOWERS OVER WESTERN AND CENTRAL PARTS OF
PA ON FRIDAY. THIS FEATURE LOSES ITS SURFACE REFLECTION LATE
FRIDAY AS ITS PARENT UPPER TROUGH PHASES OFF THE MID ATLANTIC
SHORE TO STRENGTHEN AN OCEAN STORM THAT RACES SOUTHEAST OF NEW
ENGLAND FRI NIGHT AND SATURDAY. RESIDUAL DEFORMATION ZONE FLURRIES
OR SNOW SHOWERS APPEAR LIKELY FRIDAY NIGHT INTO EARLY SATURDAY
OVER MAINLY THE ALLEGHENIES AND N CENTRAL MOUNTAINS, FOLLOWED BY
SOME LAKE EFFECT SNOW SHOWERS INTO THE NW MOUNTAINS FOR THE
REMAINDER OF SATURDAY AND INTO SUNDAY. ACCUMS WITH THE CLIPPER
FRIDAY APPEAR LIGHT, GENERALLY A COATING ACROSS CENTRAL AREAS
AND A COATING TO PERHAPS A FEW INCHES OVER THE HIGHER WESTERN
AND NORTHERN TERRAIN, WITH ADDITIONAL LIGHT LAKE EFFECT ACCUMS
CONFINED TO THE NW MOUNTAINS. EVEN COLDER CONDITIONS ARRIVE FOR
SUNDAY AS THE ARCTIC HIGH BUILDS OVER NW PA SUNDAY NIGHT
PRODUCING WIDESPREAD MINS IN THE SINGLE DIGITS ABOVE ZERO MONDAY
MORNING.
AVIATION /20Z TUESDAY THROUGH SUNDAY/
VFR EXPECTED AT ALL TAFS SITES EXCEPT FOR KBFD WHERE SLIGHT
VEERING OF THE SFC-CLOUD BEARING LAYER THROUGH EARLY THIS
EVENING SHOULD HELP TO ADVECT THE EXTENSIVE AREA OF STRATO CU
RESIDING OVER THE LOWER GREAT LAKES AND POINTS JUST INLAND NEAR
THE I-90 CORRIDOR.
WITH A SMALL RIDGE OF HIGH PRESSURE MOVING OVER THE AREA
TONIGHT, LIGHT WINDS WILL ALLOW FOR THE DEVELOPMENT OF SOME FOG,
MAINLY ACROSS VALLEYS OF THE NORTH AND EAST. THERE IS AT LEAST A
40 PERCENT CHANCE OF IFR CONDITIONS AT IPT, MDT, AND LNS FROM
10Z-12Z WED. BFD MAY ALSO SEE LOWERING CIGS, WITH A 40% CHC OF
LIFR CIGS FROM 06-12Z WED.
PRECIP WILL OVERSPREAD CENTRAL PA FROM SW TO NE BETWEEN 12Z AND
16Z WED. SKY/VSBY WILL LOWER TO MVFR WITH AREAS OF IFR POSSIBLE.
PTYPE WILL MOSTLY BE IN THE FORM OF RAIN, WITH SOME WET SNOW
MIXING IN NEAR AND JUST NORTH OF THE I-80 CORRIDOR. THE NORTHERN
MTNS (KBFD- KELM) SHOULD BE COLD ENOUGH FOR THE BULK OF THE
PRECIP TO FALL AS ALL WET SNOW (AFTER PERHAPS A VERY BRIEF
PERIOD OF MIXED RAIN AND SNOW MIDDAY WEDNESDAY.
LAKE EFFECT SNOW SHOWERS ARE LIKELY ACROSS BFD AND JST AS THIS
SYSTEM DEPARTS WED NIGHT.
OUTLOOK...
THU...RESTRICTIONS LIKELY FOR NORTHERN AND WESTERN AIRFIELDS. CHC
OF LINGERING SHSN ACROSS THE LAKE EFFECT/UPSLOPE SNOW BELT,
MOSTLY IN THE AM
FRI...IFR POSSIBLE IN SNOW NW & RAIN SE.
SAT...MVFR CIGS NW.
CLIMATE
ASTRONOMICAL WINTER (SOLSTICE) BEGINS ON SATURDAY, DECEMBER 21ST
AT 4:19 A.M. EST.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT
LONG TERM...LAMBERT/DEVOIR/DANGELO/BAUCO
AVIATION...LAMBERT
CLIMATE...STEINBUGL
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