172
FXUS61 KCTP 281840
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
240 PM EDT TUE APR 28 2026
WHAT HAS CHANGED
* SLIGHT ADJUSTMENTS TO RAINFALL FORECAST ON WEDNESDAY, MAINLY
ACROSS SOUTHEASTERN PENNSYLVANIA.
* BUILT OUT SLIGHTLY MORE DETAILS ON THE SEVERE THREAT FOR
WEDNESDAY AFTERNOON/EVENING.
* TEMPERATURES TRENDED SLIGHTLY COLDER FOR LATE WEEK AND
THROUGHOUT THE WEEKEND, INCREASING FREEZE THREAT.
KEY MESSAGES
1) BENEFICIAL RAINFALL THROUGH THE MIDDLE OF THE WEEK, SEVERE
THUNDERSTORMS POSSIBLE ON WEDNESDAY.
2) COOL PATTERN LATE THIS WEEK AND INTO THE WEEKEND BRINGS
RENEWED FROST/FREEZE CONCERNS TO CENTRAL PENNSYLVANIA.
DISCUSSION
1) BENEFICIAL RAINFALL THROUGH THE MIDDLE OF THE WEEK, SEVERE
THUNDERSTORMS POSSIBLE ON WEDNESDAY.
THE BULK OF WIDESPREAD PRECIPITATION EXPECTED ACROSS CENTRAL
PENNSYLVANIA TODAY HAS SHIFTED EAST OF THE AREA; HOWEVER, HI-RES
MODEL GUIDANCE CONTINUES TO HIGHLIGHT SOME (LIGHT) RAIN SHOWERS
ACROSS MAINLY THE NORTHERN HALF OF COMMONWEALTH THROUGH THE
AFTERNOON HOURS. GENERALLY DRIER CONDITIONS ARE EXPECTED
OVERNIGHT, WITH AMPLE LOW-LEVEL MOISTURE LIKELY ALLOWING FOR FOG
SHROUDING THE RIDGETOPS INTO WEDNESDAY MORNING. THIS COULD LEAD
TO SOME HAZARDOUS TRAVEL OVERNIGHT SO ANY MOTORISTS EXPECTED TO
BE ON ROADWAYS THAT TRAVERSE HIGHER ELEVATIONS SHOULD BE READY
FOR RAPIDLY CHANGING CONDITIONS OVER SHORT DISTANCES.
A WIDESPREAD SOAKING RAINFALL IS FORECAST ACROSS ALL OF CENTRAL
PENNSYLVANIA, WITH PRECIPITATIONS LARGELY INCREASING LATE
WEDNESDAY MORNING (WESTERN HALF) INTO WEDNESDAY AFTERNOON
(EASTERN HALF) AND CONTINUE INTO THURSDAY MORNING. CURRENT
FORECAST CONTINUES TO OUTLINE A WIDESPREAD 0.75" TO 1.00" ACROSS
MUCH OF THE AREA WITH FAR SOUTHEASTERN PENNSYLVANIA POTENTIALLY
TRENDING SLIGHTLY LOWER IN RECENT MODEL GUIDANCE. SOME
THUNDERSTORM DEVELOPMENT COULD LEAD TO LOCALLY HIGHER TOTALS
BETWEEN 1.00" AND 1.25" MAINLY ACROSS NORTHWESTERN PENNSYLVANIA
WHERE SOLID REMAIN THE MOST MOIST. DESPITE THIS, FLOODING RISK
ACROSS THE ENTIRE FORECAST AREA REMAINS LOW ON WEDNESDAY.
THE STORM PREDICTION CENTER HAS RETAINED THE DAY 2 MARGINAL
RISK FOR SEVERE THUNDERSTORMS ACROSS PORTIONS OF SW PA, MAINLY
ALONG AND SOUTH OF THE I-99/US-22 CORRIDOR. WITH REGARDS TO THE
SEVERE THREAT, THERE REMAINS CONSIDERABLE UNCERTAINTY MAINLY IN
THE FORM OF INSTABILITY. MEAN CAPE VALUES FROM THE MOST RECENT
12Z HREF RUN OUTLINE CAPE VALUES ~200 J/KG WHICH IS GENERALLY
NOT FAVORABLE FOR SEVERE THUNDERSTORM POTENTIAL; HOWEVER,
SPREADS BETWEEN THE 10TH-90TH PERCENTILES OUTLINE A SPREAD OF
NEAR ~500 J/KG. THIS SPREAD IS MAINLY DRIVEN BY POTENTIAL CLOUD
COVER, WHICH LOOKS TO BE FAIRLY EXPANSIVE ACROSS THE REGION
THROUGHOUT MUCH OF THE DAY ON WEDNESDAY. IT IS OF NOTE THAT MOST
RECENT HREF GUIDANCE HAS HAD A SLIGHT UPTICK IN CAPE VALUES;
HOWEVER, WILL NEED TO HAVE SOME ABILITY TO DESTABILIZE IN ORDER
FOR THIS SEVERE POTENTIAL TO MATERIALIZE. AT THIS TIME, DAMAGING
WINDS WILL BE THE MAIN CONCERN; HOWEVER, GIVEN AMPLE LOW-LEVEL
SHEAR WILL ALSO NEED TO KEEP AN EYE ON ANY ROTATING STORMS.
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KEY MESSAGE 2: COOL PATTERN LATE THIS WEEK AND INTO THE WEEKEND
BRINGS RENEWED FROST/FREEZE CONCERNS TO CENTRAL PENNSYLVANIA.
COOL CYCLONIC FLOW PATTERN ALOFT SETS UP OVER THE EASTERN
UNITED STATES FOR THE LATE WEEK PERIOD WITH GUIDANCE INDICATING
A CLOSED 500 MB LOW ROTATING OVER THE NORTHERN GREAT LAKES INTO
SOUTHEASTERN CANADA. THIS ALLOWS FOR CONTINUED HIGH CONFIDENCE
IN TEMPERATURES 5-15 DEGREES BELOW THE HISTORICAL AVERAGE
THURSDAY THROUGH SUNDAY. BREEZY CONDITIONS DUE A SLIGHT PRESSURE
GRADIENT SET UP OVER PENNSYLVANIA ON THURSDAY COULD ALLOW FOR
WIND GUSTS BETWEEN 25 AND 35 MPH, WHICH WILL ADD TO THE RELATIVE
CHILL FACTOR.
FROST RISK IS NON-ZERO GIVEN THE COLDER NIGHTTIME TEMPERATURES
ESPECIALLY LATER IN THE WEEKEND, BUT IT APPEARS MORE LIKELY TO
SEE AN ADVECTIVE FREEZE OR NOTHING SCENARIO GIVEN THE PERSISTENT
CLOUD COVER AND SUSTAINED NORTHWESTERLY WIND. GUIDANCE HAS
TRENDED SLIGHTLY COOLER FOR THE WEEKEND PERIOD, WITH SUB-
FREEZING TEMPERATURES EXPECTED ACROSS THE NORTHERN TIER
BEGINNING THURSDAY NIGHT INTO FRIDAY MORNING, WITH MULTIPLE
OVERNIGHT PERIODS OF SUB-FREEZING TEMPERATURES POSSIBLE THROUGH
SUNDAY MORNING. THE COLDEST OF THESE TIMEFRAMES BASED ON RECENT
NBM GUIDANCE WILL BE SATURDAY NIGHT INTO SUNDAY MORNING, WHERE
RECENT FORECAST BRINGS SUB- FREEZING TEMPERATURES TO MUCH OF THE
AREA ALONG AND NORTH/WEST OF THE I-80/I-99 CORRIDOR.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
SCATTERED SHOWERS ACROSS THE EASTERN AIRFIELDS WILL TAPER OFF BY
DINNER TIME AND THEN SOME ADDITIONAL POCKETS OF RAIN WILL
REDEVELOP OVERNIGHT, BRINGING OCCASIONAL REDUCTIONS IN
VISIBILITY ACROSS THE REGION. NO THUNDER IS EXPECTED WITH THESE
SHOWERS.
CEILINGS WILL GRADUALLY DETERIORATE AREAWIDE TONIGHT INTO
WEDNESDAY, WITH IFR/LIFR LIKELY EVERYWHERE ACROSS WEST AND
CENTRAL PA (BFD, JST, AOO, UNV) AND MVFR FAVORED AT IPT, MDT,
AND LNS. THERE IS SOME UNCERTAINTY IN THE ONSET OF CEILING
RESTRICTIONS ACROSS THE REGION, AND LOWER CEILINGS MAY WORK INTO
THE SOUTHEAST EARLIER THAN CURRENTLY CONVEYED IN THE TAF
PACKAGE. THERE IS ALSO SOME POTENTIAL FOR REDUCED VISIBILITY IN
LOW CLOUDS/FOG, ESPECIALLY ACROSS THE WEST. WHETHER THIS WILL
MANIFEST IN SIMPLY LOW CEILINGS OR IN REDUCED VISIBILITY REMAINS
A BIT UNCLEAR. BUT IFR/LIFR RESTRICTIONS ARE EXPECTED
REGARDLESS.
MORE WIDESPREAD SHOWERS, AND PERHAPS SOME THUNDERSTORMS, WILL
OVERSPREAD THE AREA ON WEDNESDAY FROM SOUTHWEST TO NORTHEAST.
VISIBILITY RESTRICTIONS ARE LIKELY (MVFR/IFR) AS CEILINGS REMAIN
LOW. THE BEST CHANCE FOR THUNDER WILL BE IN SOUTHERN PA, FIRST
AFFECTING JST AND THEN POTENTIALLY EXTENDING EAST TOWARD MDT AND
LNS LATER IN THE AFTERNOON/EVENING.
OUTLOOK...
WED...MVFR/IFR FAVORED DUE TO LOW CLOUD CEILINGS & RAIN
OVERSPREADING THE REGION. -TSRA POSSIBLE SOUTH.
THU...VFR/MVFR IN THE MORNING AS RAIN ENDS WEST TO EAST,
BECOMING VFR IN THE AFTERNOON.
FRI-SAT...MAINLY VFR WITH BRIEF RESTRICTIONS POSSIBLE IN
SHOWERS.
SUN...RESTRICTIONS POSSIBLE NORTHWEST IN -RA AND POSSIBLY SOME
-SN.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
WHAT HAS CHANGED...BEATY
KEY MESSAGES...BEATY
DISCUSSION...BEATY
AVIATION...BANGHOFF/LAMBRECH
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