902
FXUS61 KCTP 192214
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
514 PM EST THU DEC 19 2024
SYNOPSIS
* WIDESPREAD LIGHT SNOW ACCUMULATION PROBABLE FRIDAY-FRIDAY
NIGHT BEFORE ANOTHER ARCTIC COLD SNAP ARRIVES THIS WEEKEND
* CHILLY AND DRY START NEXT WEEK FOLLOWED BY A GRADUAL WARMUP
AND MIXED PRECIPITATION POTENTIAL CHRISTMAS EVE AND CHRISTMAS
DAY
NEAR TERM /UNTIL 6 AM FRIDAY MORNING/
CLOUDS ALOFT ARE ALREADY SPREADING OVER THE ALLEGHENIES, ONLY
FURTHERING THE CLOUDY NARRATIVE FOR TONIGHT. BREAKS ARE POSSIBLE
IN THE S-CENT COUNTIES. DEVELOPING EASTERLY FLOW WILL CONTINUE
TO VEER OVERNIGHT, AND DRAW MOISTURE IN FROM THE SOUTH AS THE
STORM APPROACHES. BROAD-SCALE LIFT OVER PA AND SEEDING OF LOWER
CLOUD LAYER SHOULD RESULT IN LIGHT SNOW BEGINNING LATE
TONIGHT/BEFORE SUNRISE OVER THE CENTRAL MTNS AND ALLEGHENIES.
THE TEMPS SHOULD BE ABLE TO CREEP INTO THE M20S FOR MOST OF THE
AREA OVERNIGHT. TEMP/MOISTURE PROFILE ALOFT IS FAVORABLE FOR
OK BUT NOT GIANT, FLUFFY DENDRITES N OF I-80, AND SLRS ARE
PROGGED TO BE VERY CLOSE TO CLIMATOLOGY (10:1 S AND 15:1 N).
THIS IS A LITTLE LOWER THAN MOST CLIPPERS. SO, IF ANYWAY, THE
SLRS MAY GO UPWARD.
SHORT TERM /6 AM FRIDAY MORNING 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
DEVELOPMENT 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 THURSDAY/
NORTHWESTERLY FLOW CONTINUES INTO THE BEGINNING OF THE LONG
TERM, WITH LINGERING LAKE EFFECT SNOW SHOWERS ACROSS NW PA
FINALLY TAPERING OFF ON SUNDAY. IT WILL BE ANOTHER COLD DAY,
HOWEVER, WITH HIGHS ACROSS CENTRAL PA RUNNING WELL BELOW
AVERAGE (MID TEENS NORTH TO UPPER 20S SOUTH).
THE SFC HIGH IS PROGGED TO DRIFT OF THE EAST COAST SUNDAY NIGHT
INTO MONDAY, WITH A LIGHT SOUTHEASTERLY FLOW DEVELOPING. AFTER
A VERY CHILLY START TO THE DAY, MONDAY AFTERNOON WILL BE A FEW
DEGREES MILDER THAN SUNDAY BUT STILL CHILLY.
CLOUDS WILL BE ON THE INCREASE MONDAY NIGHT, WITH OUR NEXT
WEATHER MAKER BRINGING LIGHT SNOW OR A RAIN/SNOW MIX INTO THE
REGION LATE MONDAY NIGHT INTO TUESDAY. THE WEATHER WILL REMAIN
A BIT UNSETTLED THROUGH THE MIDDLE OF NEXT WEEK, ALTHOUGH WE
SHOULD CONTINUE TO SEE A TREND TOWARDS SLIGHTLY MILDER
TEMPERATURES AS THE WEEK PROGRESSES.
AVIATION /22Z 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/STEINBUGL
NEAR TERM...DEVOIR/STEINBUGL
SHORT TERM...DEVOIR/STEINBUGL
LONG TERM...EVANEGO/NPB
AVIATION...GUSEMAN/DEVOIR/FITZGERALD
CLIMATE...STEINBUGL
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