034
FXUS61 KCTP 171621
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1121 AM EST TUE DEC 17 2024
SYNOPSIS
* SUNSHINE THROUGH TODAY WITH MILD TEMPERATURES AND GUSTY WEST
TO SOUTHWEST WINDS
* MORE PRECIPITATION WEDNESDAY AFTERNOON INTO THURSDAY MORNING
WITH RAIN LIKELY SOUTH OF I-80 AND SNOW OR A WINTRY MIX NORTH
* A CLIPPER WILL BRING MORE LIGHT SNOW ON FRIDAY AND LEAVE
BEHIND A CONSIDERABLY COLDER STRETCH OF WEATHER FOR THE
WEEKEND.
NEAR TERM /THROUGH TONIGHT/
WEAK SURFACE COLD FRONT 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 WAS RESULTING IN ABUNDANT SUNSHINE ACROSS MUCH OF
CENTRAL AND NW PA WITH JUST SOME THIN CIRRUS IN SPOTS.
AS WINDS FRESHEN AND SHIFT TO THE WEST-SOUTHWEST ACROSS CENTRAL
PA THIS AFTERNOON, A MILD DAY IS IN STORE AREAWIDE AS NEUTRAL
TEMP ADVECTION IS PRESENT ALOFT (IN THE 925-850 MB LAYER) ACROSS
WESTERN PA AND OHIO.
AFTERNOON HIGHS COULD MAKE A RUN AT 60F IN SE PA WHILE HIGHS IN
THE LOW TO MID 40S ACROSS THE NORTHERN TIER AND LAURELS WILL
STILL BE ABOUT 5 TO 10 DEGREES ABOVE NORMAL. A GUSTY WEST WIND
WILL TEMPER THE COMFORT LEVEL A BIT, BUT STILL A PLEASANT DAY
OVERALL.
PREVIOUS
ANOTHER WELCOME CHANGE WILL BE SIGNIFICANTLY LESS CLOUD COVER
LATER THIS AFTERNOON. ALTHOUGH CLOUDS MAY BE STUBBORN FOR MUCH
OF THE MORNING, BUILDING RIDGING WILL SUPPORT MOSTLY SUNNY SKIES
FOR LOCATIONS SOUTH OF I-80 THIS AFTERNOON AND AT LEAST SOME
BREAKS IN THE CLOUDS FARTHER NORTH. 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 VALLEYS IN THE LOWER
SUSQUEHANNA VALLEY. LOWS BY WEDNESDAY MORNING WILL GENERALLY BE
AROUND 30 DEGREES.
SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/
ON WEDNESDAY, A SYSTEM OF LOW PRESSURE WILL MOVE INTO THE OHIO
VALLEY REGION AND BRING WIDESPREAD PRECIPITATION TO PENNSYLVANIA
WEDNESDAY AFTERNOON INTO THURSDAY MORNING. THERMAL PROFILES
SUPPORT RAIN FOR LOCATIONS SOUTH OF I-80 AND POTENTIAL FOR SNOW
AND/OR A WINTRY MIX OF PRECIPITATION FARTHER NORTH. QPF SHOULD
RANGE FROM A QUARTER OF AN INCH ACROSS THE NORTHERN TIER TO
AROUND HALF AN INCH IN THE SOUTH. THIS WILL CORRESPOND TO A
COUPLE INCHES OF SNOW NORTH OF US-6.
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 ON 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 MOVES 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 /16Z TUESDAY THROUGH SATURDAY/
LOW CIGS WITH IFR/LIFR CONDITIONS WILL CONTINUE THROUGH 17-18Z
ACROSS MUCH OF THE MIDDLE AND LOWER SUSQUEHANNA VALLEY AS A
DEEP LAYER OF SFC MOISTURE RESIDES JUST AHEAD OF A WEAK SFC COLD
FRONT AND BENEATH A FAIRLY STRONG LOW LEVEL INVERSION.
THESE LOW CIGS ARE EXPECTED TO IMPROVE QUICKLY TO VFR DURING THE
EARLY TO MID AFTERNOON AS DRIER AIR SURGES IN BEHIND THE FRONT
ON A MODERATELY GUSTY WESTERLY WIND.
MVFR CIGS ARE LIKELY TO MOVE BACK INTO THE BFD AREA DURING THE
MID TO LATE AFTERNOON HOURS (60% CHANCE) AS THEY'RE CURRENTLY
RIGHT ON THE SOUTHEAST EDGE OF A LARGE AREA OF STRATOCU
COVERING THE GREAT LAKES REGION.
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. PRECIP WILL MOSTLY BE IN THE FORM OF RAIN, WITH SOME
SNOW MIXING IN ACROSS THE NORTH. 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/BANGHOFF
NEAR TERM...LAMBERT/BANGHOFF
SHORT TERM...LAMBERT/BANGHOFF
LONG TERM...LAMBERT/DEVOIR/DANGELO/BAUCO
AVIATION...LAMBERT/DANGELO/COLBERT
CLIMATE...STEINBUGL
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page