189
FXUS61 KCTP 210143
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
843 PM EST FRI DEC 20 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 BRINGS POTENTIAL FOR SOME WINTRY PRECIP
WHILE TEMPERATURES CONTINUE TO MODERATE THROUGH THE END OF
THE WEEK.
NEAR TERM /THROUGH SATURDAY/
HEAVIEST SNOWFALL HAS NOW PIVOTED EAST OF THE REGION WITH STEADY
SHOWERS NOW PRIMARILY EAST OF US-15. AS DISCUSSED EARLIER
TODAY, A HEAVIER BAND OF SNOWFALL MOVED SLOWLY THROUGH
SOUTHEAST PA EARLIER THIS EVENING AND PRODUCED A QUICK INCH OF
SNOW, HELPING PUSH TOTALS IN LANCASTER COUNTY UP TOWARD 2". A
WIDESPREAD 1-2" OF SNOW WAS OBSERVED ACROSS THE FORECAST AREA.
AS THE SURFACE LOW DRIFTS OFF THE NEW ENGLAND COAST OVERNIGHT,
WRAP AROUND FLOW WILL HELP SUPPORT THE POTENTIAL FOR A BIT MORE
SNOW ACROSS THE POCONOS AND ENDLESS MOUNTAINS REGION WHILE LAKE
EFFECT/UPSLOPE SNOW DEVELOPS. CAN ALREADY SEE SOME STREAMERS
EXTENDING SOUTHEAST OF THE I-80/I-99 CORRIDOR TONIGHT, THOUGH
ACCUMULATIONS SHOULD GENERALLY BE CONFINED TO THE TYPICAL LAKE
EFFECT AND UPSLOPE SNOW REGIONS. AN ADDITIONAL INCH OR TWO OF
SNOW IS EXPECTED THROUGH THE DAY ON SATURDAY.
THE SYSTEM OFF THE COAST WILL DEEPEN CONSIDERABLY OVERNIGHT AND
RESULT IN A TIGHTENING PRESSURE GRADIENT. AS SUCH, GUSTY
NORTHWEST WINDS ARE EXPECTED TO DEVELOP AFTER MIDNIGHT AND
CONTINUE INTO THE DAY ON SATURDAY. BUFKIT SOUNDINGS SUGGEST 20
TO 30KT WINDS ARE LIKELY FOR MOST OF THE AREA. LOWS ON SATURDAY
MORNING WILL BE RIGHT AROUND NORMAL FOR THIS TIME OF YEAR,
RANGING FROM THE TEENS IN THE NORTH TO NEAR 30 IN THE SOUTH. BUT
A BRISK WIND WILL MAKE WIND CHILLS FEEL ABOUT 15 DEGREES COLDER.
SATURDAY WILL BE A CLASSIC NORTHWEST FLOW PATTERN WITH PLENTY OF
STRATOCUMULUS, BLUSTERY NORTHWEST WINDS, AND PERHAPS A FEW SNOW
FLAKES FLYING AROUND. MAXIMUM WIND CHILLS ON SATURDAY AFTERNOON
WILL STAY IN THE SINGLE DIGITS NORTH OF US-6, TEENS ALONG THE
I-80 CORRIDOR, AND LOWER 20S ALONG THE I-76 CORRIDOR. ANYONE
WITH OUTDOOR PLANS SHOULD WEAR PLENTY OF LAYERS AND LIMIT
EXPOSURE TO THE COLD TEMPERATURES AND GUSTY WINDS.
SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/
LAKE EFFECT AND UPSLOPE WILL CONTINUE SATURDAY NIGHT AS WINDS
TAPER OFF A BIT AND DRIER/COLDER AIR FILTERS IN. MINIMUM TEMPS
IN THE +SINGLE DIGITS TO UPPER TEENS WITH MINIMUM WIND CHILLS
FROM -10F TO +10F ARE EXPECTED INTO EARLY SUNDAY MORNING.
HIGH PRESSURE BUILDS OVER THE NORTHEAST ON SUNDAY, WHICH WILL
SUPPORT CLEARING SKIES, LIGHTER WINDS, AND PERSISTENT BELOW-
AVERAGE TEMPERATURES. EVEN THOUGH HIGHS IN THE LOW TEENS TO MID
20S WILL BE SEVERAL DEGREES COOLER THAN 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. 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
TO 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.
A STALLED OUT FRONTAL BOUNDARY TO OUR SOUTH COULD LIFT INTO
SOUTHERN PA AND BRING A LOW PROBABILITY FOR A LIGHT WINTRY MIX
LATER CHRISTMAS DAY INTO THURSDAY.
THE MAIN CHANGE FROM THE PREVIOUS FORECAST PACKAGES WAS TO TRIM
POPS BY ABOUT 20 PERCENT ACROSS THE BOARD WHERE MODELS SHOW A
FAIRLY EXPANSIVE SFC HIGH FROM NRN NEW ENGLAND TO THE CENTRAL
APPALACHIANS.
AVIATION /01Z SATURDAY THROUGH WEDNESDAY/
PERIODS OF LIGHT SNOW WITH WIDESPREAD IFR TO LOW END MVFR
CONDITIONS TO CONTINUE THROUGH THIS EVENING WITH SLOW
IMPROVEMENT AS WE HEAD INTO EARLY SATURDAY.
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.
CLIMATE
ASTRONOMICAL WINTER (SOLSTICE) BEGINS ON SATURDAY, DECEMBER 21ST
AT 4:19 A.M. EST.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...
NEAR TERM...BANGHOFF
SHORT TERM...BANGHOFF
LONG TERM...LAMBERT/NPB
AVIATION...LAMBERT/NPB/BOWEN
CLIMATE...STEINBUGL
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