008
FXUS61 KCTP 210849
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
349 AM EST SAT DEC 21 2024
SYNOPSIS
* SCATTERED LAKE EFFECT & UPSLOPE SNOW SHOWERS LINGER INTO
SATURDAY AS GUSTY NORTHWEST WINDS BUILD IN
* COLDEST AIRMASS OF THE SEASON SO FAR BRINGS SINGLE DIGIT LOW
TEMPERATURES BY MONDAY MORNING
* CHRISTMAS EVE SYSTEM WITH MIXED PRECIP IMPACTS TRAVEL WHILE
TEMPERATURES CONTINUE TO MODERATE THROUGH THE END OF THE WEEK.
NEAR TERM /UNTIL 6 PM THIS EVENING/
STRATIFORM LIGHT SNOW ASSOCIATED WITH AN INVERTED SURFACE TROUGH
OVER NJ HAS LARGELY EXITED THE EASTERN EDGE OF THE FORECAST
AREA AS OF 08Z. LINGERING LAKE-ENHANCED OROGRAPHIC SNOW SHOWERS
WILL CONTINUE TO AFFECT THE LAUREL HIGHLANDS AND THE N MTNS
TODAY. HOWEVER, LARGE SCALE SUBSIDENCE AND FALLING INVERSION
HEIGHTS BEHIND THE EXITING UPPER LEVEL TROUGH WILL RESULT IN
ONLY MINIMAL ADDITIONAL ACCUMULATIONS, WITH PERHAPS UP TO AN
INCH ALONG THE LAUREL RIDGE OR IN THE SNOWBELT OF NORTHWEST
WARREN COUNTY.
A DEEPENING LOW LIFTING INTO THE CANADIAN MARITIMES WILL RESULT
IN A FAIRLY TIGHT PRESSURE GRADIENT OVER PA TODAY, PRODUCING
IN GUSTY NORTHWEST WINDS. BUFKIT SOUNDINGS SUGGEST 20 TO 30KT
GUSTS ARE LIKELY, MAINLY DURING THE AFTERNOON HOURS. EARLY
MORNING SATELLITE IMAGERY IS SHOWING DEVELOPING BREAKS IN THE
STRATOCU EAST OF THE ALLEGHENIES. HOWEVER, DIURNAL HEATING AND
COLD TEMPS ALOFT SHOULD RESULT IN CLOUDS FILLING IN BY
AFTERNOON, WITH MOSTLY CLOUDY SKIES EVEN ACROSS THE SUSQ VALLEY
AT TIMES.
TEMPERATURES ARE ON TRACK TO BOTTOM OUT AT DAWN FROM THE UPPER
TEENS OVER THE NW MTNS, TO THE UPPER 20S IN THE LOWER SUSQ
VALLEY. CLOUD COVER AND LOW LEVEL COLD ADVECTION SHOULD RESULT
IN LITTLE WARMING THE REST OF THE DAY. MIXING DOWN MODEL 850MB
TEMPS OF -14C TO -16C YIELDS EXPECTED HIGHS FROM ONLY AROUND
20F ACROSS THE N MTNS, TO THE LOW 30S IN THE LOWER SUSQ VALLEY.
THE GUSTY NORTHWEST WIND SHOULD RESULT IN MIDDAY WIND CHILLS IN
THE SINGLE DIGITS OVER THE N MTNS AND TEENS MOST OTHER
LOCATIONS.
SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/
DWINDLING LAKE EFFECT SNOW SHOWERS/FLURRIES OVER THE NW
MTNS/LAUREL HIGHLANDS ARE EXPECTED TONIGHT, AS HIGH PRESSURE
APPROACHES FROM THE GRT LKS. THE COLD WILL BE THE MAIN STORY,
WITH MIN TEMPS IN THE SINGLE DIGITS OVER THE N MTNS TO MID TEENS
IN THE SOUTHEAST COUNTIES. ALTHOUGH WINDS ARE EXPECTED TO
DIMINISH TONIGHT, RADIATIONAL COOLING WILL NOT BE IDEAL DUE TO
A LINGERING BREEZE OVER THE EASTERN COUNTIES AND LINGERING
LAKE EFFECT STRATOCU OVER THE LAURELS AND NW MTNS.
MOSTLY SUNNY AND COLD WEATHER WITH LIGHT WINDS ARE EXPECTED
SUNDAY, AS HIGH PRESSURE BUILDS OVER THE STATE. GEFS 2M TEMP
ANOMALIES ARE 10-15 DEGREES BELOW AVERAGE, TRANSLATING TO HIGHS
RANGING FROM THE MID TO UPPER TEENS OVER THE N MTNS, TO THE MID
AND UPPER 20S IN THE VALLEYS OF SOUTHERN PA. EVEN THOUGH HIGHS
WILL BE SEVERAL DEGREES BELOW THOSE OF SATURDAY, THE
COMBINATION OF SUNSHINE AND LIGHTER WINDS MAY ACTUALLY MAKE IT
SLIGHTLY MORE PLEASANT TO BE OUTSIDE ON SUNDAY AFTERNOON.
WITH HIGH PRESSURE OVERNIGHT SUNDAY NIGHT, IDEAL CONDITIONS FOR
RADIATIONAL COOLING WILL UNDOUBTEDLY LEAD TO THE COLDEST LOW
TEMPERATURES YET THIS WINTER BY MONDAY MORNING. LOWS WILL
GENERALLY BE IN THE SINGLE DIGITS WITH BELOW ZERO TEMPERATURES
FAVORED IN NORTHEAST PA.
RETURN SOUTHERLY FLOW BEHIND THE DEPARTING HIGH WILL HELP
TEMPERATURES REBOUND SOME ON MONDAY AS HIGH CLOUDS STREAM IN
AHEAD OF THE NEXT SYSTEM. CURRENT MEDIUM RANGE GUIDANCE
INDICATES MOST OF THE DAY WILL BE DRY, BUT PRECIPITATION COULD
ARRIVE IN NORTHWEST PA BY MONDAY EVENING.
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
A FAIRLY FAST MOVING, NORTHERN STREAM SHORTWAVE WILL CROSS PA
LATE MONDAY INTO TUESDAY AND BRING SOME LIGHT SNOW TO THE AREA.
BEST CHANCE FOR -SN AND A LIGHT ACCUM OF A COATING TO 2 INCHES
WILL BE ACROSS THE NORTHERN MTNS OF THE STATE. SOME TRAVEL
DISRUPTIONS ARE POSSIBLE FOR I-80, BUT SIGNIFICANT ACCUMULATIONS
APPEAR UNLIKELY AT THIS POINT. GFS AND ITS ENSEMBLES ARE
FURTHER NORTH WITH THE TRACK OF THE MID AND UPPER LEVEL TROUGH,
BUT QPF ALONG THE TRAILING COLD FRONT LEADS TO A SIMILAR OUTCOME
TO THE EC WITH RESPECT TO SNOW PROBS/AMOUNTS.
MORE OF A BLOCKY/SPLIT FLOW PATTERN DEVELOPS ACROSS THE ENTIRE
CONUS AS WE HEAD THROUGH CHRISTMAS EVE AND CHRISTMAS DAY. MODELS
INDICATE A GENERAL DRY AND CHILLY CHRISTMAS DAY WITH MAX TEMPS
RANGING FROM THE LOW TO MID 30S NE TO THE LOW 40S IN THE METRO
AREAS OF SOUTHERN PA. WITH SIMILAR TEMPERATURES ON TUESDAY
ACROSS THE REGION, PROSPECTS OF A WHITE CHRISTMAS ARE LOOKING
RATHER BLEAK FOR ALL BUT THE NORTHERN TIER OF PA.
LATER IN THE WEEK, PREDICTABILITY DROPS OFF QUITE A BIT WITH
FAIRLY WEAK FORCING AND A VERY WIGGLY 500MB PATTERN. WITH HIGH
PRESSURE TO THE NORTHEAST, IT APPEARS PRECIPITATION CHANCES WILL
BE HIGHER IN SOUTHERN PA. RELATIVELY LOW MOISTURE/PWATS INDICATE
THAT QPF SHOULD BE LOW, BUT PERSISTENT EASTERLY FLOW COULD
CREATE SOME RISK FOR A WINTRY MIX AND SOME FREEZING RAIN WITH
ANY ORGANIZED PRECIPITATION. HAVE KEPT PRECIP AS ALL RAIN OR
SNOW AT THIS POINT, BUT WILL CONTINUE TO MONITOR THE THREAT.
AVIATION /08Z SATURDAY THROUGH WEDNESDAY/
ANY LINGERING LIGHT SNOW WITH WIDESPREAD IFR TO LOW END MVFR
CONDITIONS WILL DIMINISH OVERNIGHT WITH SLOW IMPROVEMENT IN
CIGS AS WE HEAD INTO EARLY SATURDAY MORNING.
CONDITIONS FOR MOST SITES AFTER 05Z SATURDAY WILL BE
BORDERLINE MVFR. A FEW LINGERING SNOW SHOWERS ARE POSSIBLE,
ESPECIALLY AT BFD WHERE SOME LAKE EFFECT SNOW COULD OCCUR.
VFR CONDITIONS WILL BE LIKELY ACROSS THE CENTRAL RIDGE AND
VALLEY REGION AFTER 11Z SAT, WHILE PA WESTERN MTN AIRFIELDS
SHOULD STAY MVFR TO HIGH END IFR IN OCCASIONAL SNOW SHOWERS IN
BANDS STREAMING SE OFF THE GREAT LAKES.
OUTLOOK...
SAT...LINGERING SHSN NW/SW PA; GUSTY WINDS ~25-30KTS ACROSS THE
HIGHER ELEVATIONS DURING THE LATE AM/PM HOURS.
SUN...SHSN FAR NW PA; OTHERWISE, NO SIG WX.
MON...NO SIG WX.
TUE...SNOW ENTERS W PA AM, OVERSPREADS AREA BY AFTERNOON.
WED...RESIDUAL SHOWERS EARLY. BECOMING VFR.
CLIMATE
ASTRONOMICAL WINTER (SOLSTICE) BEGINS ON SATURDAY, DECEMBER 21ST
AT 4:19 A.M. EST.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...BANGHOFF
NEAR TERM...FITZGERALD
SHORT TERM...FITZGERALD/BANGHOFF
LONG TERM...LAMBERT/BANGHOFF/NPB
AVIATION...GARTNER
CLIMATE...STEINBUGL
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