623
FXUS61 KCTP 211116
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
616 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/
WATER VAPOR LOOP AT 11Z SHOWS A SHARP UPPER LEVEL TROUGH PUSHING
THROUGH CENTRAL PA. STRONG FORCING AHEAD OF THIS FEATURE WILL
SUPPORT SCATTERED SNOW SHOWERS ACROSS THE SOUTH-CENTRAL MTNS
THROUGH AROUND 13Z. LARGE SCALE SUBSIDENCE BEHIND THIS FEATURE
SHOULD END THE RISK OF SNOW SHOWERS EAST OF THE ALLEGHENIES BY
MID MORNING. LINGERING LAKE-ENHANCED OROGRAPHIC SNOW SHOWERS
WILL CONTINUE TO AFFECT THE LAUREL HIGHLANDS AND THE N MTNS
TODAY. HOWEVER, 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 SURFACE LOW LIFTING INTO THE CANADIAN MARITIMES
WILL RESULT IN A FAIRLY TIGHT PRESSURE GRADIENT OVER PA TODAY,
PRODUCING 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
BY MIDDAY, 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 /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 /11Z SATURDAY THROUGH WEDNESDAY/
A FEW SNOW SHOWERS ARE PROGRESSING ACROSS THE WESTERN AIRFIELDS
THIS MORNING CAUSING MVFR TO IFR VISIBILITIES AND CEILINGS DUE
TO SNOWFALL. THESE UPSLOPE AND LAKE EFFECT STREAMER BANDS OF
SNOW SHOULD GRADUALLY DRIFT FURTHER WEST AS FLOW OVER LAKE ERIE
BECOMES MORE NORTHERLY. HOWEVER LOW CEILINGS ARE LIKELY TO
PERSIST OVER BFD UNTIL TONIGHT, AND UPSLOPE SNOW WILL KEEP JST
IN MVFR CONDITIONS MOST OF THE DAY. A FEW HOURS OF IMPROVED
CONDITIONS SHOULD OCCUR AT THE WESTERN SITES, BUT LOW CLOUDS
WILL LIKELY QUICKLY BUILD BACK IN DURING THE OVERNIGHT PERIOD
TONIGHT.
VFR CONDITIONS WILL BE LIKELY ACROSS THE CENTRAL RIDGE AND
VALLEY REGION AFTER 12Z TAF PACKAGE. SURFACE WINDS WILL BE GUSTY
OUT OF THE NORTH TODAY AS WELL, WITH ALL SITES EXPECTING TO SEE
WIND GUSTS NEAR 25KTS UNTIL NEAR 06Z TONIGHT.
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
LONG TERM...LAMBERT/BANGHOFF/NPB
AVIATION...BOWEN
CLIMATE...STEINBUGL
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