373
FXUS61 KCTP 011131
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
731 AM EDT TUE SEP 1 2026
WHAT HAS CHANGED
* ADDED MORE DETAIL ABOUT POTENTIAL SEVERE WEATHER TODAY AND ON
WEDNESDAY.
KEY MESSAGES
1) LATE SUMMER SURGE OF HEAT AND HUMIDITY BRINGS MULTI-DAY
SEVERE THUNDERSTORM AND EXCESSIVE RAINFALL THREAT TO KICKOFF
SEPTEMBER
DISCUSSION
KEY MESSAGE 1:
A SERIES OF MID LEVEL IMPULSES TRACKING EASTWARD ALONG THE
NORTHERN PERIPHERY OF AN EXPANSIVE 500MB RIDGE WILL INTERACT
WITH ANOMALOUS MOISTURE/INSTABILITY AND STRONG WNW FLOW ALOFT
TO PROMOTE A MULTI-DAY SEVERE STORM AND EXCESSIVE RAIN RISK
ACROSS PORTIONS OF CPA TODAY THROUGH THURSDAY.
A SURGE OF LATE SUMMER HEAT (MAX TEMPS 80-90F RANGE) WITH
DEWPOINTS IN UPPER 60S TO MID 70S WILL RESULT IN A VERY MOIST
BOUNDARY LAYER WITH IMPRESSIVE MLCAPE VALUES IN THE NEIGHBORHOOD
OF 1500-3000 J/KG GIVEN MID LEVEL LAPSE RATES AROUND 7 C/KM.
FORECAST SOUNDINGS ALSO SHOW ROBUST DEEP LAYER/EFFECTIVE SHEAR
VALUES AND APPRECIABLY CURVED LOW LEVEL HODOGRAPHS. AS SUCH, A
COUPLE OF SUPERCELLS WILL BE POSSIBLE. FROM A LARGE SCALE LIFT
PERSPECTIVE, RISING MOTION MAY BE AT LEAST PARTIALLY SUPPRESSED
BY THE RIGHT EXIT REGION OF AN UPPER LEVEL JET MAX THROUGH MUCH
OF TODAY UNTIL AT LEAST MID AFTERNOON. CONVECTION INITIATION IS
MORE LIKELY IN THE 4PM-9PM TIME FRAME AS THE BOUNDARY LAYER RH
INCREASES AND THE RIGHT ENTRANCE REGION OF THE JET MAX
APPROACHES.
INCREASING MUCAPE VALUES LATE TONIGHT THROUGH WED MORNING
SUGGEST STORMS/SEVERE RISK LIKELY WON'T BE TIED TO THE TYPICAL
DIURNAL CYCLE. ANY PREEXISTING MCS UPSTREAM COULD BE MAINTAINED
BY THE UNSTABLE ATMOSPHERE WITH US WEDNESDAY MORNING. HIRES
MODEL GUIDANCE ALSO SHOWS AN EASTERLY FLOW ACROSS OUR EASTERN
ZONES ASSOCIATED WITH A BACK DOOR COLD FRONT. ALONG THAT
BOUNDARY, MODELS DEPICT VERY LARGE HODOGRAPHS ASSOCIATED WITH A
STRONGLY VEERED WIND PROFILE, WITH 0-3 KM SRH ON THE ORDER OF
350 M2/S2 AND 0-3KM WIND SHEAR APPROACHING 40 KTS. IF SUPERCELLS
CAN RIDE SOUTHEASTWARD ON THE UNSTABLE SIDE OF THE BOUNDARY AND
INGEST THIS HIGHLY SHEARED INFLOW, A COUPLE STRONGER TORNADOES
CAN NOT BE RULED OUT WED AFTERNOON INTO WED EVENING.
THE SEVERE RISK WILL BE FOCUSED MORE ACROSS THE SOUTHERN TIER OF
CENTRAL PA BY THURSDAY, AND SOUTH OF THE PA-MD BORDER ON FRIDAY.
AN UPPER TROUGH PASSAGE SUGGESTS SOME LINGERING SHOWER ACTIVITY
INTO THE WEEKEND, OTHERWISE IT LOOKS MOSTLY DRY.
THE LATE SUMMER HEAT IS FORECAST TO PEAK TODAY AND WEDNESDAY
WITH VERY WARM NIGHTS +10-20F ABOVE THE HISTORICAL AVERAGE AND
MAX HEAT INDEX VALUES JUST SHORT OF HEAT ADVISORY CRITERIA
(100F). THE EXCEPTION WILL BE ACROSS THE EASTERN ZONES WED WHEN
THE BACK DOOR COLD FRONT COULD HOLD MAX TS DOWN A FEW TO SEVERAL
DEGREES. THE UPPER RIDGE IS FORECAST TO RETROGRADE BY THE END
OF THE WEEK WHICH ALLOWS FOR INCREASED TROUGHING AND A RETURN TO
MORE SEASONAL TEMPERATURES.
AVIATION /12Z TUESDAY THROUGH SATURDAY/
WARM FRONTAL BOUNDARY EXTENDING FROM THE EASTERN FINGER LAKES
REGION, SOUTH THROUGH THE WESTERN POCONOS AND SE PA WILL MEANDER
A BIT TO THE SOUTH AND WEST OVER THE NEXT 24 TO 48 HOURS. THIS
AIRMASS BOUNDARY WILL PROVIDE AN AVENUE TO A FEW ROUNDS OF
SHOWERS AND AFTERNOON/EVENING THUNDERSTORMS TO TRACK SOUTHEAST
ALONG.
THE MOST LIKELY PLACES TO SEE FOG/LOW CIGS THROUGH THE MID
MORNING HOURS TODAY WILL BE AT IPT AND TO A LESSER DEGREE AT
MDT/LNS.
BFD COULD SEE BRIEF PERIODS OF MVFR CEILINGS EARLY TODAY, BUT
IFR SEEMS UNLIKELY.
ANY FOG OR STRATUS WILL QUICKLY MIX OUT IN THE 12-13Z PERIOD.
ATTENTION WILL THEN TURN TOWARDS AFTERNOON CONVECTION.
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED
FOR THE MID AFTERNOON TO EARLY EVENING HOUR TODAY, BUT THERE
REMAINS UNCERTAINTY AS TO THE EXACT TIMING AND PLACEMENT GIVEN
THE LACK OF ANY LARGER-SCALE, DEEP-LAYER FORCING AND THE
PRESENCE OF THE SUBSIDING, THERMALLY INDIRECT BRANCH (RIGHT EXIT
REGION) OF A 40-50 KT MID/UPPER LEVEL JET MAX EMBEDDED IN THE
NW FLOW.
SOME GUIDANCE WOULD SUGGEST STORMS IN THE NORTHWEST AS EARLY AS
15Z AND OTHERS SUGGEST CONVECTION MAY NOT ARRIVE UNTIL 23Z.
OVERALL, EXPECT THE POTENTIAL FOR BRIEF PERIODS OF ACTIVE
CONVECTION AT ALL TERMINALS ACROSS CENTRAL PA THIS
AFTERNOON/EVENING, WITH A HEDGE TOWARD THE AIRFIELDS ACROSS THE
EASTERN THIRD OF PA. BRIEF REDUCTIONS TO VISIBILITIES AND
CEILINGS TO LOW END MVFR OR IFR ARE POSSIBLE IN THE 18Z TUE-02Z
WED PERIOD.
OUTLOOK...
TUE-FRI...SCATTERED SHRA/TSRA WITH BRIEF RESTRICTIONS POSSIBLE;
MORNING FOG POSSIBLE.
SAT...SHRA/TSRA TRENDING LESS LIKELY AS COLD FRONT MOVES
SOUTHWARD ACROSS THE COMMONWEALTH; MORNING FOG POSSIBLE.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
WHAT HAS CHANGED...COLBERT
KEY MESSAGES...STEINBUGL/COLBERT
DISCUSSION...STEINBUGL/COLBERT
AVIATION...LAMBERT/BOWEN
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