100
FXUS61 KCTP 221657
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1157 AM EST SUN DEC 22 2024
SYNOPSIS
HIGH PRESSURE OVER ONTARIO CANADA JUST TO THE EAST OF GEORGIAN
BAY WILL DRIFT TO THE EAST ACROSS THE ADIRONDACKS TONIGHT.
A WEAK AREA OF LOW PRESSURE AT THE SURFACE AND ALOFT WILL TRACK
NORTH OF THE STATE MONDAY NIGHT INTO EARLY CHRISTMAS EVE. A
PAIR OF WEAKENING SHORTWAVES ARE LIKELY TO RIDE THE NORTHERN
PERIPHERY OF A BUILDING RIDGE OVER PA THE SECOND HALF OF NEXT
WEEK, AS A LARGE SURFACE HIGH REMAINS ANCHORED NORTH OF NEW
ENGLAND.
NEAR TERM /THROUGH TONIGHT/
AREA OF SHALLOW LAKE EFFECT AND UPSLOPE STRATOCU CLOUDS HAS
BECOME CONFINED MAINLY ACROSS THE LAUREL HIGHLANDS LATE THIS
MORNING WITH JUST SOME FLURRIES THERE AND ALSO TO THE WEST OF
ROUTE 219 IN NW PA.
ELSEWHERE, SKIES THIS AFTERNOON INTO TONIGHT WILL BE MAINLY
CLEAR.
MODEL SOUNDINGS BECOME MIXED THIS AFTERNOON TO 900MB, WHERE
TEMPS AROUND -14C SUPPORT HIGHS RANGING FROM THE MID TEENS OVER
THE MTNS NORTH OF KIPT, TO THE UPPER 20S IN THE LOWER ELEVATIONS
ALONG THE MASON DIXON LINE.
ALTHOUGH HIGHS WILL BE SEVERAL DEGREES BELOW THOSE OF SATURDAY,
THE COMBINATION OF SUNSHINE AND LIGHTER WINDS WILL MAKE IT
SLIGHTLY MORE PLEASANT TO BE OUTSIDE.
SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/
HIGH PRESSURE IS PROGGED TO BUILD OVER PA TONIGHT, PROVIDING
NEARLY IDEAL CONDITIONS FOR RADIATIONAL COOLING WITH CLEAR
SKIES, A CALM WIND AND A FRESH SNOWCOVER OVER PARTS OF THE AREA.
HAVE THEREFORE UNDERCUT NBM MIN TEMPS BY A FEW DEGREES. TONIGHT
SHOULD UNDOUBTEDLY BE THE COLDEST YET THIS WINTER, WITH DAYBREAK
READINGS LIKELY RANGING FROM THE SINGLE DIGITS BELOW ZERO IN THE
COLDEST HOLLOWS NORTH OF KIPT, TO AROUND 10 ABOVE OVER THE
SOUTHERN TIER COUNTIES.
A RETURN SOUTHERLY FLOW BEHIND THE DEPARTING SURFACE HIGH WILL
HELP TEMPERATURES REBOUND SLIGHTLY ON MONDAY AS HIGH CLOUDS
STREAM IN AHEAD OF AN UPSTREAM SHORTWAVE OVER THE W GRT LKS.
GEFS 2M TEMPS INDICATE MAX TEMPS WILL REMAIN SEVERAL DEGREES
BELOW AVERAGE.
THE UPSTREAM SHORTWAVE IS PROGGED TO PASS JUST NORTH OF PA
MONDAY NIGHT INTO EARLY TUESDAY. THE STRONGEST FORCING WITH THIS
FEATURE SHOULD REMAIN NORTH OF THE AREA AND MOISTURE RETURN
ALONG THE ATTENDANT LOW LEVEL JET IS UNIMPRESSIVE. THEREFORE,
EXPECT ONLY SOME VERY LIGHT OVERRUNNING SNOW OR FLURRIES MONDAY
NIGHT INTO EARLY TUESDAY. THE 00Z EPS INDICATES THE NW MTNS ARE
BEST SITUATED TO SEE AN INCH OR SO OF ACCUMULATION DUE TO
PROXIMITY TO THE SHORTWAVE AND OROGRAPHIC FORCING FROM AN
UPSLOPING SSW FLOW. MODEL SOUNDINGS INDICATE THERE IS SOME RISK
FOR A BIT OF VERY LIGHT FREEZING RAIN OVER THE LOWER SUSQ VALLEY
AROUND 12Z TUESDAY, BUT IT IS UNCERTAIN WHETHER MEASURABLE PRECIP
EVEN REACHES THAT FAR SOUTH.
THE BEST FORCING AND DEEPEST MOISTURE SHOULD HAVE PASSED PA BY
LATE TUESDAY MORNING. HOWEVER, RESIDUAL LOW LEVEL MOISTURE
ASCENDING THE ALLEGHENIES COULD RESULT IN SPOTTY VERY LIGHT
SNOW/DRIZZLE INTO THE AFTERNOON OVER THE WESTERN PART OF THE
FORECAST AREA.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
ON THE LARGE-SCALE, THE AMPLIFIED, COLD EASTERN
CANADIAN/NORTHEASTERN CONUS UPPER TROUGH DOMINATING AT THE
PRESENT TIME SHOULD BE A THING OF THE PAST BY CHRISTMAS DAY, AS
THIS FEATURE LIFTS OUT INTO THE NORTHERN ATLANTIC. IT WILL
REPLACED BY BUILDING HEIGHTS AND A GENERALLY MORE ZONAL FLOW
PATTERN ALOFT. THIS TRANSLATES INTO MORE SEASONABLE TEMPERATURES
FOR LATE DECEMBER ACROSS PA, EVEN TRENDING ABOVE CLIMO TOWARDS
NEXT WEEKEND.
AS FOR THE SENSIBLE WEATHER, THERE IS INCREASING CONFIDENCE THAT
SURFACE HIGH PRESSURE FROM SOUTHEASTERN CANADA DOWN INTO THE
NORTHEASTERN U.S. WILL KEEP THE WEATHER DRY FOR THE COMMONWEALTH
FROM CHRISTMAS DAY INTO AT LEAST THURSDAY.
UNCERTAINTY GROWS LATER IN THE WEEK, AS LOW-LEVEL EASTERLY FLOW
AND THE APPROACH OF WEAK SHORT-WAVE ENERGY FROM THE MIDWEST
COULD BRING BOUTS OF LIGHT PRECIPITATION, ESPECIALLY FOR
SOUTHERN AND WESTERN SECTIONS OF THE STATE. AT THIS EARLY
JUNCTURE, LIGHT RAIN APPEARS TO BE THE MOST PROBABLE
PRECIPITATION TYPE, BUT POCKETS OF LIGHT WINTRY MIX ARE NOT BY
ANY MEANS OFF THE TABLE.
AVIATION /18Z SUNDAY THROUGH FRIDAY/
MVFR LAKE EFFECT AND OROGRAPHIC, SHALLOW STRATOCU WITH JUST
SOME P6SM FLURRIES WILL BE FOCUSED OVER THE LAUREL HIGHLANDS
THROUGH THIS AFTERNOON BEFORE DIMINISHING LATE TODAY/EARLY
TONIGHT AS LLVL WINDS VEER ABOUT 40 DEG TO THE NORTH WITH
SPEEDS DECREASING TO UNDER 6 KTS.
ALL OTHER SITES WILL WILL EXPERIENCE MAINLY CLEAR SKIES THROUGH
THE REST OF THE 15Z TAF PERIOD.
LIGHT WINDS AND CLEAR SKIES ARE EXPECTED FOR TONIGHT INTO THE
FIRST PART OF MONDAY.
MAIN ISSUE FOR THE AREA AFTER MONDAY WOULD BE FOR LOWER
CIGS AND EVEN SOME MIXED PRECIPITATION FROM TIME TO TIME,
MAINLY AFTER EARLY MONDAY EVENING, AS A MILDER AND HIGHER
DEWPOINT AIRMASS WORKS INTO THE AREA.
OUTLOOK...
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...LAMBERT/FITZGERALD
NEAR TERM...LAMBERT/FITZGERALD
SHORT TERM...FITZGERALD
LONG TERM...JUREWICZ
AVIATION...LAMBERT/BOWEN
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