663
FXUS61 KCTP 211752
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1252 PM EST SAT DEC 21 2024
SYNOPSIS
* SCATTERED LAKE EFFECT & UPSLOPE SNOW SHOWERS LINGER TODAY 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 7 PM THIS EVENING/
THE BASE OF AN UPPER TROUGH IS ROTATING THROUGH CENTRAL PA TODAY
AND GENERATING WIDESPREAD LAKE-ENHANCED STREAMER BANDS
THROUGHOUT THE FORECAST AREA. OCCASIONAL REDUCTIONS IN
VISIBILITY AND A QUICK DUSTING OF SNOW HAVE BEEN OBSERVED ON
SOME OF THE ROAD WEATHER CAMERAS AROUND THE STATE SO FAR.
THESE SNOW SHOWERS WILL GRADUALLY TAPER OFF INTO THE EVENING AS
THE UPPER TROUGH MOVES EAST. LINGERING LAKE- ENHANCED
OROGRAPHIC SNOW SHOWERS MAY LINGER INTO THE OVERNIGHT HOURS
ACROSS THE LAUREL HIGHLANDS AND NORTHERN MOUNTAINS. MAIN AREA OF
CONCERN THROUGH THE AFTERNOON IS A HEFTY BAND WITH A LAKE HURON
TO LAKE ERIE CONNECTION THAT HAS ALREADY BROUGHT A QUICK
ACCUMULATION OF 3+ INCHES NORTH OF PITTSBURGH. THAT BAND IS
POINTING RIGHT TOWARD EXTREME SOUTHWEST SOMERSET COUNTY AND
COULD DROP 2 TO 3 INCHES OF SNOW THERE THROUGH DINNER TIME. AS
SUCH, HAVE ISSUED A SPECIAL WEATHER STATEMENT TO REFLECT THE
REDUCED VISIBILITIES, ACCUMULATING SNOW POTENTIAL, AND RAPIDLY-
CHANGING WEATHER CONDITIONS FOR MOTORISTS.
A DEEPENING SURFACE LOW LIFTING INTO THE CANADIAN MARITIMES
HAS PRODUCED A FAIRLY TIGHT PRESSURE GRADIENT OVER PA TODAY,
WITH 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, ESPECIALLY EAST OF THE ALLEGHENIES. HOWEVER, DIURNAL
HEATING AND COLD TEMPS ALOFT SHOULD RESULT IN CLOUDS FILLING IN
EARLY THIS AFTERNOON, WITH MOSTLY CLOUDY SKIES EVEN ACROSS THE
SUSQ VALLEY AT TIMES.
CLOUD COVER AND LOW LEVEL COLD ADVECTION SHOULD RESULT IN
LITTLE WARMING TODAY. 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 /7 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 GREAT LAKES. 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 /18Z SATURDAY THROUGH THURSDAY/
NORTHWEST FLOW CONTINUES TO GENERATE SCATTERED SNOW SHOWERS
ACROSS CENTRAL PA TODAY, THOUGH VISIBILITY RESTRICTIONS SHOULD
BE INFREQUENT. WINDS WILL SHIFT TO BECOME MORE NORTHERLY INTO
THIS EVENING, WHICH WILL MAINTAIN LAKE EFFECT/UPSLOPE SHOWERS
AND MVFR CEILINGS AT JST AND BFD THROUGH THE OVERNIGHT HOURS.
THE MVFR DECK COULD SCATTER OUT OCCASIONALLY THIS AFTERNOON AT
BOTH SITES, BUT THE MVFR DECK WITH THICKEN UP AGAIN OVERNIGHT.
FARTHER EAST, VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD.
BRIEF MVFR CEILINGS CANNOT BE RULED OUT AT AOO AND UNV OVERNIGHT,
BUT NOT ENOUGH CONFIDENCE TO INCLUDE AT THIS TIME. SURFACE
WINDS WILL BE GUSTY OUT OF THE NORTH TODAY AS WELL, WITH ALL
SITES EXPECTING TO SEE WIND GUSTS 20 TO 30KTS INTO THIS EVENING
WITH SLIGHT WEAKENING OVERNIGHT.
SKIES WILL CLEAR OUT ON SUNDAY AS HIGH PRESSURE BUILDS IN. WINDS
WILL BE LIGHTER AS WELL.
OUTLOOK...
SUN-MON...NO SIG WX.
TUE...SNOW ENTERS W PA AM, OVERSPREADS AREA BY AFTERNOON.
WED...NO SIG WX.
WED NIGHT...PATCHY FREEZING RAIN POSSIBLE.
THU...LIGHT RAIN POSSIBLE SOUTH.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...BANGHOFF
NEAR TERM...FITZGERALD/BANGHOFF
SHORT TERM...FITZGERALD/BANGHOFF
LONG TERM...LAMBERT/BANGHOFF/NPB
AVIATION...BANGHOFF
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