977
FXUS61 KCTP 191856
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
156 PM EST THU DEC 19 2024
SYNOPSIS
MOSTLY CLOUDY CONDITIONS WILL PREVAIL TONIGHT INTO FRIDAY. AN
ALBERTA CLIPPER WILL BRING WIDESPREAD LIGHT SNOW ACCUMULATION
FRIDAY AND FRIDAY NIGHT BEFORE ANOTHER ARCTIC COLD SNAP ARRIVES
THIS WEEKEND. CHILLY CONDITIONS PREVAIL INTO THE START OF NEXT
WEEK, FOLLOWED BY A GRADUAL WARMUP AND MIXED PRECIPITATION
POTENTIAL CHRISTMAS EVE AND CHRISTMAS DAY.
NEAR TERM /THROUGH TONIGHT/
INVERSION HEIGHTS LOWERING A FEW THOUSAND FEET THIS MORNING
INTO EARLY AFTERNOON ALLOWED EARLIER LINGERING SNOW FLURRIES TO
DISSIPATE OVER THE ALLEGHENIES. SOME BREAKS IN THE CLOUDS MAY
TRY TO GROW OVER THE LOWER SUSQ VALLEY AS HIGH CLOUDS PEEL OFF
TO THE EAST, BUT MOST AREAS REMAIN BKN-OVC.
CLOUDS WILL HANG TOUGH TONIGHT WITH SEASONABLE TEMPERATURES, AND
LOW TEMPS IN THE 25-30F RANGE. CONSENSUS OF NEAR TERM MODELS AND
CAMS DEPICTS LIGHT SNOW POSSIBLY BREAKING OUT TOWARD OR JUST
PAST DAYBREAK OVER THE WESTERN ALLEGHENIES.
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/
AS FORCING CONTINUES TO INCREASE FROM THE APPROACHING CLIPPER
SYSTEM, COVERAGE OF LIGHT SNOW WILL EXPAND ACROSS CENTRAL PA BY
MID TO LATE MORNING. PARENT TROUGH FEEDS SIGNIFICANT SECONDARY
DEVELPOMENT OFF OF THE MID ATLANTIC COAST LATE FRIDAY AS THE
UPPER TROUGH TAKES ON A NEGATIVE TILT. FOCUS BY THIS TIME WILL
HINGE ON STRENGTH OF LLVL EASTERLY FLOW AND CONVERGENCE AXIS
PROGGED TO SETUP BENEATH THE LEFT EXIT REGION OF A MID/UPPER
LEVEL JET STREAK. POTENTIAL INTERACTION OF THESE FEATURES
COULD ALLOW FOR A SLOWLY PIVOTING NNW-SSE ORIENTED BAND OF
DEFORMATION SNOW (NORLUN TROUGH) TO ORGANIZE OVER THE FAR
EASTERN PART OF THE FORECAST AREA FRIDAY AFTERNOON THROUGH
FRIDAY NIGHT, POTENTIALLY FAVORING HIGHER SNOWFALL TOTALS, BUT
CERTAINTY FOR THIS REMAINS ON THE LOWER SIDE AND WILL NEED
FURTHER EVALUATION THIS EVENING AND OVERNIGHT.
FOR NOW WE'RE STAYING CLOSE TO NBM/WPC QPF/SNOW OUTPUT AND SLRS
WITH OVERALL AMOUNTS RANGING FROM 1-3" IN THE WESTERN AND
NORTHERN MTNS TO A COATING-1" FOR MOST AREAS ALONG AND TO THE
SOUTHEAST OF THE I99/I80 CORRIDOR FROM THE SOUTH CENTRAL
ALLEGHENIES THROUGH THE MID AND LOWER SUSQUEHANNA VALLEY.
INCREASINGLY COLDER NWLY UPSLOPE FLOW ON THE BACKSIDE OF THE
SYSTEM MAY ALSO ENHANCE SNOW TOTALS OVER THE LAUREL HIGHLANDS
THROUGH FRIDAY NIGHT. WPC PROBS ARE SLIGHTLY BETTER THAN 50/50
FOR >4" OF SNOW IN THE TYPICALLY FAVORED WINDWARD SLOPES, SKI
AREAS, AND SUMMITS ABOVE 2000FT PARTICULARLY IN WESTERN SOMERSET
COUNTY NEAR INTERSECTION OF WESTMORELAND/FAYETTE LINE. SOME
DISCUSSION ABOUT POTENTIAL HEADLINES FOR THIS WITH NEIGHBORS FOR
LATER FRIDAY, BUT CONSENSUS WAS TO HOLD OFF AND SPS THE MORNING
ARRIVAL OF SNOWFALL IF NECESSARY FRIDAY MORNING.
THE PATTERN TURNS BRISK AND MUCH COLDER TO START WEEKEND WITH
LAKE EFFECT SNOW SHOWERS AND FLURRIES INTO SATURDAY NIGHT.
MODELS SHOW A POTENTIAL HURON CONNECTION OVER THE WESTERN MTNS
WITH AN ADDITIONAL INCH OR SO POSSIBLE IN THE HIGHER TERRAIN.
HIGHS ON SATURDAY WILL BE 10 TO 15 DEGREES BELOW THE HISTORICAL
AVERAGE WITH MAX TEMPS IN THE 20-30F RANGE. A BRISK AND GUSTY
NW WIND WILL MAKE IT FEEL LIKE THE SINGLE DIGITS/TEENS TO
AROUND 20F. SATURDAY NIGHT WILL BE QUITE COLD WITH MIN TEMPS IN
THE +SINGLE DIGITS TO UPPER TEENS WITH MINIMUM WIND CHILLS FROM
-5F TO +10F INTO EARLY SUNDAY MORNING.
LONG TERM /SUNDAY THROUGH WEDNESDAY/
NORTHWESTERLY FLOW CONTINUES INTO THE BEGINNING STAGES OF THE
LONG-TERM WITH LINGERING LAKE EFFECT SNOW SHOWERS INTO PORTIONS
OF NW PA THROUGH SUNDAY MORNING. NBM POPS DURING THIS TIME SEEM
UNDERDONE, SO HAVE UPPED POPS COMPARED TO PREVIOUS FORECAST
CYCLES WITH A MULTITUDE OF ENSEMBLE GUIDANCE INDICATING SOME
SNOW SHOWERS ACROSS WARREN/MCKEAN/POTTER COUNTIES. NW'LY FLOW
ACROSS PORTIONS OF THE LAUREL HIGHLANDS WILL SUPPORT SOME
MENTIONS OF SNOW SHOWERS; HOWEVER, MUCH LESS CONFIDENCE ON
COVERAGE THIS FAR SOUTH, SO HAVE CAPPED MENTIONS TO A SCHC
MAINLY AHEAD OF SUNRISE SUNDAY. MODEL GUIDANCE DOES CONTINUE TO
INDICATE TEMPERATURES WELL BELOW SEASONAL AVERAGES WITH THE
COLDEST WIND CHILLS ACROSS NE PA BY DAYBREAK SUNDAY. THIS
FORECAST CYCLE CONTINUES TO OUTLINE -5 TO -10 DEGREE WIND CHILLS
ACROSS PORTIONS OF POTTER/TIOGA/SULLIVAN COUNTIES WITH SOME
SIGNALS FOR WIND CHILLS DIPPING BELOW THE -10 DEGREE MARK AT
HIGHER ELEVATIONS OF POTTER COUNTY. NO PLANS ON ANY HEADLINES AT
THIS TIME DUE TO LOWER CONFIDENCE IN TEMPERATURES REACHING
BELOW THRESHOLDS; HOWEVER, WANT TO STRESS THAT IT WILL BE COLD
ACROSS PORTIONS OF NE PA SUNDAY MORNING.
SURFACE HIGH PRESSURE WILL KEEP CONDITIONS DRY WITH
TEMPERATURES SLOWLY MODERATING INTO MONDAY EVENING. MODEL
GUIDANCE BEGINS TO DIVERGE ON TUESDAY WITH RESPECT TO THE NEXT
WEATHER SYSTEM, WITH ECMWF TRENDING DRY THROUGH THE END OF THE
LONG-TERM PERIOD OUTSIDE OF SOME SNOWFALL CHANCES ACROSS THE
NORTHERN TIER WITH THE GFS OUTLINING A MORE ACTIVE PERIOD WITH
RAIN/SNOW ACROSS THE FORECAST AREA ON WEDNESDAY WITH SOME
POTENTIAL FOR DRIER CONDITIONS INTO THURSDAY/FRIDAY. THIS
FORECAST CYCLE STICKS FAIRLY CLOSE TO NBM GUIDANCE GIVEN THIS
SPREAD; HOWEVER, HAVE TAKEN OUT ANY MENTIONS OF FREEZING RAIN AS
CONFIDENCE REMAINS TOO LOW ON TIMING/TRACK TO MENTION ANYTHING
OUTSIDE OF A RAIN/SNOW MIX.
AVIATION /19Z THURSDAY THROUGH TUESDAY/
STILL SOME LINGERING FLURRIES OVER THE LAUREL HIGHLANDS AT MID
MORNING, BUT THESE SHOULD DWINDLE INTO EARLY AFTERNOON AS
INVERSION HEIGHTS SLOWLY LOWER. CEILINGS ACROSS THE ALLEGHENIES
(BFD/JST) WILL GRADUALLY IMPROVE TO HIGH-END MVFR/LOW-END VFR
CRITERIA BY EARLY AFTERNOON AS DRIER/SINKING AIR MOVES IN.
CLOUDS WILL BEGIN TO INCREASE AND LOWER AGAIN THIS EVENING AND
OVERNIGHT AS A CLIPPER SYSTEM APPROACHES TONIGHT INTO FRIDAY,
BRINGING LIGHT SNOW TO THE CENTRAL PA AIRSPACE FRIDAY. BFD/JST
WILL STAND THE BEST CHANCE OF DEGRADING CEILINGS BETWEEN 06-12Z
FRIDAY.
OUTLOOK...
FRI...LIGHT SNOW/LOW CIGS LIKELY, MAINLY N AND W MTNS.
SAT...NW WINDS GUSTING TO AROUND 25KTS. AM SNOW SHOWERS
POSSIBLE N AND W MTNS.
SUN-MON...NO SIG WX EXPECTED.
CLIMATE
ASTRONOMICAL WINTER (SOLSTICE) BEGINS ON SATURDAY, DECEMBER 21ST
AT 4:19 A.M. EST.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...DEVOIR
NEAR TERM...DEVOIR
SHORT TERM...DEVOIR/STEINBUGL
LONG TERM...NPB
AVIATION...GUSEMAN/DEVOIR/FITZGERALD
CLIMATE...STEINBUGL
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