311
FXUS61 KCTP 172352
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
652 PM EST TUE DEC 17 2024
SYNOPSIS
* PRECIPITATION WEDNESDAY AFTERNOON AND EVENING WITH RAIN
LIKELY SOUTH OF I-80 AND SNOW OR A WINTRY MIX ACROSS THE
NORTHERN MOUNTAINS
* LAKE EFFECT SNOW SHOWERS WEDNESDAY NIGHT AND THURSDAY
* A CLIPPER WILL BRING LIGHT SNOW ON FRIDAY
* CONSIDERABLY COLDER FOR THE WEEKEND.
NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/
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 TUESDAY/
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 /23Z TUESDAY THROUGH SUNDAY/
VFR EVERYWHERE WILL CONTINUE FOR MOST OF THE NIGHT AT PERHAPS
ALL BUT BFD AND IPT. LOW CLOUDS WILL WORK DOWN FROM THE NW AND
DIP BFD INTO MVFR EARLY TONIGHT AND THEN TO IFC AROUND OR
SHORTLY AFTER MIDNIGHT/05Z. IPT HAS HIGH MOISTURE LINGERING AT
THE SFC AND THE CALM AIR MAY ALLOW FOG TO FORM AND EVENTUALLY
TAKE THEM INTO IFC LATE TONIGHT. MDT AND LNS, TOO, HAVE HIGHER
MSTR, AND COULD GET FOGGY BEFORE SUNRISE. 50% CHC THAT THOSE 2
SERN TERMINALS WILL GET INTO IFC, BUT 80% AT IPT.
LOW PRESSURE PASSING ACROSS SRN PA WEDNESDAY WILL BRING RAIN TO
ALL TERMINALS EXCEPT BFD - WHERE THE PREDOMINANT PRECIP TYPE
WILL BE SNOW. HOWEVER, THIS WILL BE A QUICK SHOT OF PRECIP (6
HRS). THE VISBY WILL DROP TO IFC QUICKLY, BUT COULD POP BACK UP
TO MVFR AS THE PRECIP TAPERS OFF AROUND 23-01Z. THE WIND JUST
ALOFT (2-3KFT) GETS UP TO 35KT IN THE S AND THE LIGHT SFC WIND
WILL NECESSITATE A MENTION OF LLWS FOR THE LAST 6HRS OF THIS TAF
PKG (18Z WED-00Z THURS) FOR ALL BUT BFD AND IPT.
LAKE EFFECT CLOUDS AND SNOW SHOWERS THEN START FOR BFD AS THIS
SYSTEM DEPARTS WED NIGHT AND LINGER INTO THURSDAY. IFR IS
POSSIBLE THERE AND JST IN THE UPSLOPE FLOW, BUT CLOUDS AND ANY
FLURRIES ELSEWHERE WILL ONLY BE GOOD FOR MVFR CIGS/VSBYS.
A CLIPPER SYSTEM ROLLS OVERHEAD ON FRIDAY, PRODUCING WIDESPREAD
IFC IN SNOW/CIGS. THE SE (MDT AND LNS) MAY BE WARM ENOUGH FOR
RAIN.
OUTLOOK...
FRI...IFR POSSIBLE IN SNOW NW & RAIN SE.
SAT-SUN...MVFR CIGS IN SHSN @ BFD/JST. MAINLY VFR ELSEWHERE.
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...DANGELO
CLIMATE...STEINBUGL
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