876
FXUS61 KCTP 221429
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1029 AM EDT TUE SEP 22 2026
WHAT HAS CHANGED
* VERY MINOR CHANGES IN THE NEXT 6-12 HRS TO MATCH RECENT
OBS/SAT/RADAR.
KEY MESSAGES
1) PERIODS OF LIGHT TO MODERATE BENEFICIAL RAIN WILL SLOWLY
DRIFT SOUTH THROUGH WEDNESDAY WITH CLOUDY/DAMP/COOL CONDITIONS.
2) TRENDING DRIER LATER IN THE WEEK AS A COASTAL STORM DEVELOPS
OFFSHORE.
DISCUSSION
KEY MESSAGE 1: PERIODS OF LIGHT TO MODERATE BENEFICIAL RAIN
WILL SLOWLY DRIFT SOUTH THROUGH WEDNESDAY WITH CLOUDY/DAMP/COOL
CONDITIONS.
1030 AM UPDATE...
RADAR LOOP SHOWS A SHEARING/DIFFERENCE IN MOVEMENT BETWEEN THE
AIR MOVING IN FROM THE NE AND THE STABLE, COOL, DAMP AIRMASS
SOUTH OF I-80. CLEARING WILL BE BRIEF IN NORTHERN TIOGA COUNTY
AS THE CU FIELD IS ALREADY FILLING IN THAT HOLE. NO REAL CHANGES
TO TEMPS OR DEWPOINTS OUTSIDE A NORMAL START-WITH-REAL-NUMBERS
UPDATE. BUT, WE HAVE BUMPED SKY COVER UP. SOME TALLER CLOUDS ARE
STARTING TO BUBBLE UP ALONG THE MD BORDER. SO, THUNDER AND VERY
BRIEF HEAVY RAIN STILL CANNOT BE RULED OUT.
PREV...
A QUASI-STATIONARY AREA OF MID-LEVEL FRONTOGENESIS THAT HAS
BEEN THE FOCUS FOR SHOWERS OVERNIGHT ALONG THE I-80 CORRIDOR
WILL MOVE GRADUALLY SOUTH TODAY. NORTH OF THIS BOUNDARY, DRY AIR
WILL GRADUALLY POUR INTO THE AREA AS A SPRAWLING HIGH BUILDS
INTO THE NORTHEAST US. ALONG AND TO THE SOUTH OF THE
AFOREMENTIONED FEATURE, PERIODS OF LIGHT TO MODERATE RAINFALL
WILL CONTINUE THROUGH MUCH OF THE DAY. A COMPACT WAVE OF ENERGY
DRIFTING ACROSS THE LAUREL HIGHLANDS COULD GENERATE AN ISOLATED
RUMBLE OF THUNDER OR TWO. ALTHOUGH A ROGUE STORM COULD PRODUCE
SOME HEAVIER RAINFALL, RATES ARE EXPECTED TO REMAIN LOW ENOUGH
TO PRECLUDE FLASH FLOODING TODAY. PONDING IN LOW-LYING OR POOR
DRAINAGE AREAS CANNOT BE RULED OUT, BUT MOST OF THE RAIN WILL BE
BENEFICIAL.
TEMPERATURES WILL HOLD STEADY IF NOT DROP A BIT TODAY THANKS TO
PERSISTENT EASTERLY FLOW AND A COLD AIR DAMMING PATTERN. HIGHS
THIS AFTERNOON WILL BE SOME -10 TO -15F BELOW AVERAGE FOR THIS
TIME OF YEAR, GENERALLY NOT MAKING IT OUT OF THE 50S. OVERNIGHT,
RAIN WILL CONTINUE TO SHIFT SOUTHWEST AND WE COULD EVEN SEE
RAIN-FREE CONDITIONS FOR MUCH OF THE NIGHT. FOG/LOW CLOUDS ARE A
GOOD BET AGAIN TONIGHT, ESPECIALLY ALONG AND SOUTH OF THE
MOISTURE GRADIENT THAT WILL SET UP ACROSS THE COMMONWEALTH.
BY WEDNESDAY MORNING, DEWPOINTS IN THE LOW 40S AND PERHAPS UPPER
30S WILL POUR INTO NORTHEAST PA AND SIGNAL THE ARRIVAL OF FALL
RIGHT ON TIME.
ON WEDNESDAY, SHOWERS AND LOW CLOUDS WILL LINGER ACROSS
SOUTHWEST PA, WHILE LOCATIONS FARTHER NORTH WILL SEE IMPROVING
CONDITIONS - ALBEIT GRADUALLY. EASTERLY WINDS WILL AGAIN SPELL
COOLER-THAN-NORMAL TEMPERATURES AND STUBBORN CLOUDS. WEDNESDAY
WILL BE ANOTHER COOL DAY WITH TEMPERATURES ONLY A FEW DEGREES
WARMER COMPARED TO TUESDAY AND HIGHS IN THE UPPER 50S TO LOW
60S.
-------------------------------------------------------------
KEY MESSAGE 2: TRENDING DRIER LATER IN THE WEEK AS A COASTAL
STORM DEVELOPS OFFSHORE.
NORTHEAST FLOW WEDNESDAY INTO THURSDAY BETWEEN 1038 MB HIGH IN
QUEBEC AND A DEVELOPING COASTAL LOW WILL ADVECT IN DEWPOINTS IN
THE 40S AND PERHAPS EVEN THE 30S AT THE SFC WED-THU, WITH EVEN
DRIER AIR IN THE 500-850 MB LAYER. THIS SHOULD BRING AN END TO
THE RAINFALL FOR AT LEAST A COUPLE OF DAYS. THE NEXT FEATURE TO
MONITOR WILL BE THE COASTAL STORM, WHICH MAY MEANDER OFF THE NEW
ENGLAND AND MID ATLANTIC COAST INTO THE EARLY PART OF NEXT WEEK
WITH THIS BLOCKING HIGH TO ITS NORTH. SUCH BLOCKY PATTERNS
ARE NOTORIOUSLY DIFFICULT TO PREDICT WITH RESPECT TO SFC
FEATURES AND PRECIP POTENTIAL/PLACEMENT/TIMING. DEPENDING ON THE
SIZE OF THE COASTAL STORM AND HOW MUCH IT RETROGRADES, RAIN WILL
BE POSSIBLE IN AT LEAST EAST CENTRAL PA BETWEEN FRI AND EARLY
NEXT WEEK, BUT CONFIDENCE IS LOW. HIGHER CONFIDENCE IN WIND
GUSTS OF 15-25 MPH AND BELOW NORMAL TEMPS THROUGH THE END OF THE
WEEK.
IF THE CURRENT FORECAST HOLDS TRUE, EASTERN PA COULD BE
RATHER CLOUDY (MAINLY HIGH CLOUDS) WHILE WESTERN PA IS SUNNY AT
LEAST FOR THE FIRST HALF OF THE WEEKEND. THE WESTERN PERIPHERY
OF THE COASTAL STORM'S CIRRUS DECK COULD MAKE FOR SOME VIBRANT
SUNSETS. TEMPERATURES WILL GRADUALLY INCREASE INTO THE WEEKEND,
RETURNING TO NEAR NORMAL CONDITIONS BY SATURDAY AND SUNDAY.
AVIATION /14Z TUESDAY THROUGH SATURDAY/
PERIODS OF RAIN AND SHOWERS WILL CONTINUE PRIMARILY ACROSS THE
SOUTHERN 2/3RDS OF THE COMMONWEALTH THROUGH TUESDAY NIGHT, WITH
AREAS OF -RA/RA THIS MORNING TRENDING TOWARDS -SHRA IN THE
AFTERNOON/EVENING AS HIGH PRESSURE GRADUALLY BUILDS IN ACROSS
THE NORTHEASTERN US.
A PERIOD OF PREVAILING MVFR RESTRICTIONS IS
LIKELY ACROSS ALL TERMINALS, ESPECIALLY THROUGH 18Z TUESDAY, AS 925
MB RH VALUES APPROACH 100% ALONG A NW-SE GRADIENT. PERIODS OF
IFR TO BRIEFLY LIFR ARE MOST FAVORED ACROSS THE SOUTH-CENTRAL
MOUNTAINS (KJST/KAOO/KUNV) WHERE EASTERLY SFC FLOW ACROSS
TERRAIN + STEADIEST RAINFALL LOOK TO OVERLAP.
THE QUICKEST IMPROVEMENTS TO VFR ARE MOST LIKELY AT KIPT AROUND
18Z TUESDAY AS DRIER AIR FILTERS IN FROM THE NORTHEAST, WITH
IMPROVEMENTS TO VFR OCCURRING ELSEWHERE TUESDAY NIGHT AND
PERHAPS INTO WEDNESDAY MORNING (MAINLY KJST/KAOO, FARTHEST FROM
THE MOISTURE GRADIENT, AND PERHAPS KMDT/KLNS AS WELL).
OUTLOOK...
WED-THU...TRENDING VFR ACROSS CENTRAL PA, WITH SLOWER
IMPROVEMENTS POSSIBLE OVER THE LAURELS AND LOWER SUSQUEHANNA
VALLEY WHERE -SHRA/BR AND LOW CLOUD CEILINGS MAY LINGER.
FRI-SAT...VFR FAVORED AS A DEVELOPING COASTAL LOW LOOKS TO
BRING SUBSIDENCE OVERHEAD, THOUGH -RA AND LOWER CLOUD CEILINGS
ASSOCIATED WITH THIS SYSTEM MAY REACH OUR EASTERN TERMINALS.
CLIMATE
ASTRONOMICAL FALL BEGINS TODAY, SEPTEMBER 22, 2026, AT 8:04PM
EDT. THIS MARKS THE TIME OF THE AUTUMNAL EQUINOX WHEN THE SUN IS
DIRECTLY ABOVE EARTH'S EQUATOR.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
WHAT HAS CHANGED...DANGELO/BANGHOFF
KEY MESSAGES...BANGHOFF
DISCUSSION...LAMBERT/DANGELO/BANGHOFF
AVIATION...TEARE
CLIMATE...BANGHOFF
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