141
FXUS61 KCTP 181937
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
237 PM EST MON NOV 18 2024
SYNOPSIS
HIGH PRESSURE WILL KEEP THINGS FAIR TONIGHT. A WARM FRONT WILL
LIFT NORTHEAST ACROSS THE REGION WITH CLOUDS AND SCATTERED
SHOWERS INTO EARLY WEDNESDAY. A DEEP, ANOMALOUSLY COLD CUT-OFF
UPPER LOW WILL TRACK ACROSS FROM THE GREAT LAKES INTO
PENNSYLVANIA LATE THIS WEEK, PRECEDED BY AN OCCLUDED FRONT
PASSAGE WEDNESDAY NIGHT.
NEAR TERM /THROUGH TONIGHT/
DRIER AIR CONTINUES TO MOVE IN FROM THE NORTH BEHIND A COLD
FRONT THIS AFTERNOON WITH DEWPOINTS IN THE LOWER 40S AND
DROPPING ACROSS THE NORTHER TIER. AS DRIER AIR MOVES IN, THE
DECK OF STRATOCUMULUS ACROSS THE SOUTHWEST PART OF THE
COMMONWEALTH CONTINUES TO SLOWLY BUT SURELY ERODE THERE WHILE
MOSTLY SUNNY SKIES PERSIST FOR THE NORTHWEST, NORTHEAST, AND
SOUTHEAST QUADRANTS OF PA.
ANOTHER VERY MILD DAY IS UNDERWAY WITH HIGHS IN THE MIDDLE 50S
TO MIDDLE 60S (+10-15 DEGREES ABOVE THE HISTORICAL AVERAGE).
LOWER DEWPOINTS AND MOSTLY CLEAR SKIES WILL ALLOW FOR
TEMPERATURES OVERNIGHT TO FALL INTO THE 30S FOR MOST OF THE
AREA. THE COOLEST READINGS WILL BE ACROSS THE NORTHERN MOUNTAINS
WHERE A FEW SPOTS COULD GET TO FREEZING. PATCHY VALLEY FOG IS
POSSIBLE AS WELL.
SHORT TERM /TUESDAY THROUGH WEDNESDAY/
UPPER LEVEL RIDGING OVER THE AREA SHOULD PROVIDE CENTRAL PA
WITH MILD AND RAIN-FREE CONDITIONS FOR MOST OF TUESDAY. A
SLIGHTLY COOLER AIRMASS WILL SUPPORT HIGH TEMPERATURES ABOUT 5
TO 7 DEGREES LOWER ON TUESDAY COMPARED TO TODAY. WARM ADVECTION
ASSOCIATED WITH A WEAKENING SHORTWAVE LIFTING INTO THE GRT LKS
SHOULD LEAD TO INCREASING CLOUDS LATE TUESDAY/TUESDAY NIGHT WITH
THE CHANCE OF A FEW SHOWERS, MAINLY OVER THE W MTNS. SHOWERS
SHOULD DECREASE IN COVERAGE AND INTENSITY OVERNIGHT. RAINFALL
AMOUNTS COULD APPROACH A TENTH OF AN INCH ACROSS THE LAUREL
HIGHLANDS, WITH LESSER AMOUNTS FARTHER EAST.
FOCUS THEN SHIFTS TO A CUT-OFF UPPER LOW DROPPING INTO THE
MIDWEST. MODEL SOUNDINGS INDICATE AN EASTERLY FLOW OFF OF THE
ATLANTIC WILL LIKELY YIELD STRATUS OVER PARTS OF THE AREA WED,
ESPECIALLY OVER THE CENTRAL MTNS. FALLING HEIGHTS AND SURGING
PWATS ALONG A SOUTHERLY LOW LEVEL JET SHOULD THEN BRING
THICKENING CLOUDS AND AN INCREASING CHANCE OF SHOWERS ACROSS THE
ENTIRE AREA BY LATE WEDNESDAY OR WED EVENING. WE MAY NEED TO
EVENTUALLY UNDERCUT NBM MAX TEMPS WED, DUE ITS WARM BIAS IN
EASTERLY FLOW/CAD SCENARIOS.REGARDLESS, WEDNESDAY WILL BE THE
LAST MILD DAY FOR AWHILE A COOLER, MORE SEASONABLE AIR ARRIVES
BY THURSDAY.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
A VERY MATURE CYCLONE WILL INTERACT WITH THE GREAT LAKES AND
PLENTY OF MOISTURE AVAILABLE THERE (WITH NO ICE FLOATING AROUND
YET). THE OCCLUDED/COLD FRONT WILL LIKELY PUSH ACROSS PA ON WED
DURING THE DAYLIGHT TO EARLY EVENING HOURS. THE TRIPLE POINT MAY
RUN W-E ACROSS PA OR JUST TO THE SOUTH OF THE STATE. I HAD
INITIALLY PUT IN SCHC THUNDER FOR LATER WED FOR THE SE, BUT
WITHDREW IT WITHOUT SUPPORT FROM OTHER FORECASTERS. THE COLD AIR
ADVECTION IS STRONGEST FROM THE WSW BUT LAGS A BIT BEHIND THE
INITIAL DRY SLOT/OCCLUSION.
THE PATTERN IN FIRST 48HRS OF THE LONG TERM IS THE MOST
INTERESTING OF THE SEASON THUS FAR, AND HAS THE MOST
SPREAD AND THEREFORE LOWEST CONFIDENCE. STILL, EVEN WITH THE
MASS FIELDS DIFFERING AMONGST GUIDANCE, THE END RESULT IS GOING
TO BE THE FIRST SNOWFALL OF THE SEASON FOR THE MOUNTAINS. THE
LAURELS (SPECIFICALLY SOMERSET CO WHICH ARE THE VERY HIGHEST
ELEVS OF PA) COULD PICK UP SIGNIFICANT AMOUNTS OF SNOW THANKS TO
A PERSISTENT UPSLOPE FLOW CARRYING GREAT LAKES (AND MAYBE
HUDSON BAY) MOISTURE IN FROM THE N/NW. COLLABORATION WITH
NEIGHBORING OFFICES AND WPC HAS RESULTED IN US NOT ISSUING A
WATCH AT THIS POINT. THERE MAY BE A COUPLE WAVES/PERIODS OF BEST
CONDITIONS FROM THURS-SAT INSTEAD OF A SINGULAR PERIOD/EVENT.
PROBABILISTIC GUIDANCE USING NBM FOR BASIS HAS <40% CHC OF
WARNING CRITERIA (6+") SNOW OCCURRING. BUT, THE EVENT COULD LAST
48+ HRS. THUS, EVEN THOUGH WE ARE STILL 4+ DAYS FROM THE PEAK
OF THE SNOWFALL INTENSITY/ACCUMS, THERE WAS SERIOUS
CONSIDERATION TOWARD STARTING A WATCH WITH THIS PKG. IN THE END,
THE COLLAB EFFORT SETTLED ON US NEEDING A BIT MORE CONFIDENCE
IN THOSE HIGHER AMOUNTS TO POST WATCHES IN PA (INCL SOMERSET
CO). IN ADDITION, THE HIGHER ELEVS OF THE POCONOS COULD ALSO
SEE ACCUMS AS THE COLD AIR COMES IN NEAR THE END OF THE INITIAL
PUSH OF PRECIP (WED PM-THURS AM). BUT, THE QPF POSSIBLE THERE
IS MUCH LOWER THAN ENOUGH TO WORRY FOR A WATCH.
A NORTHWEST FLOW PATTERN REMAINS (READ:LAKE EFFECT/UPSLOPE SHSN)
UNTIL SUNDAY WHEN HIGH PRESSURE STARTS TO SLIDE TO THE SOUTH
OF PA. BUT, WE CAN'T TOTALLY REMOVE THE CHC/SCHC POPS FROM THE
NW AT THIS POINT WITH SO MUCH UNCERTAINTY. COOLER THAN NORMAL
WEATHER WITH BLUSTERY WIND IS ANTICIPATED FOR THURS- SAT, AND
ONLY A MODEST WARM UP LATE IN THE WEEKEND/FIRST PART OF NEXT
WEEK.
AVIATION /19Z MONDAY THROUGH SATURDAY/
STRATOCUMULUS CONTINUE TO SLOWLY BUT SURELY ERODE ACROSS THE
LAUREL HIGHLANDS (JST/AOO) THIS AFTERNOON AS DRIER AIR WORKS IN.
MVFR CEILINGS WILL PERSIST AT JST THROUGH ABOUT 00Z BEFORE
SCATTERING OUT. LAST FEW OBS AT JST HAVE HAD IFR CEILINGS AND
VARIABLE MVFR/IFR REMARKS, BUT WILL PREVAIL MVFR AT THIS POINT.
ELSEWHERE, VFR WILL PERSIST OVERNIGHT AND INTO TUESDAY
AFTERNOON. PATCHY FOG IS POSSIBLE ACROSS THE NORTHWEST MOUNTAINS
AND LAURELS BY TUESDAY MORNING. NOT ENOUGH CONFIDENCE TO INCLUDE
FOG AT ANY TAF SITES AT THIS POINT (HIGHEST PROBABILITY AT
JST/BFD, POSSIBLE AT IPT, UNV, AND AOO).
CLOUDS WILL BEGIN TO INCREASE TOMORROW AHEAD OF A WARM FRONT
THAT WILL BRING LIGHT SHOWERS TO WESTERN AIRFIELDS TUESDAY
AFTERNOON. RESTRICTIONS SHOULD HOLD OFF UNTIL AFTER 21Z IN THE
WEST WITH IFR CONDITIONS DEVELOPING OVERNIGHT.
OUTLOOK...
TUE NIGHT...RESTRICTIONS LIKELY WEST
WED...RESTRICTIONS LIKELY, MAINLY NW. MORE WIDESPREAD
RESTRICTIONS WITH RAIN AND LLWS WED NIGHT.
THU-FRI...RESTRICTIONS LIKELY WITH RAIN AND SNOW SHOWERS, MAINLY
ACROSS THE MOUNTAINS. WINDY.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...LAMBERT/FITZGERALD
NEAR TERM...LAMBERT/BANGHOFF
SHORT TERM...LAMBERT/BANGHOFF
LONG TERM...FITZGERALD/DANGELO
AVIATION...BANGHOFF
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