799
FXUS61 KCTP 200645
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
245 AM EDT WED MAY 20 2026
WHAT HAS CHANGED
* LOW/MARGINAL SEVERE STORM RISK AREA NOW CONFINED TO THE
SOUTHERN TIER OF CPA THIS AFTERNOON INTO EARLY EVENING
* REITERATING BEARISH TREND FOR MAX TEMPS FRIDAY AND SATURDAY
KEY MESSAGES
1) A FEW STORMS WITH ISOLATED SEVERE WIND GUSTS AND HAIL WILL
BE POSSIBLE OVER THE SOUTHERN TIER OF CPA THIS AFTERNOON/EVENING
2) MAJOR COOLDOWN TO CLOSE OUT THE WEEK AND START MEMORIAL DAY
WEEKEND WITH WIDESPREAD SOAKING RAINFALL OVER 1 INCH FRIDAY AND
SATURDAY
DISCUSSION
KEY MESSAGE 1:
A FEW STORMS WITH ISOLATED SEVERE WIND GUSTS AND HAIL WILL BE
POSSIBLE OVER THE SOUTHERN TIER OF CPA THIS AFTERNOON/EVENING
SFC COLD FRONT CROSSING WESTERN LAKE ERIE AT 06Z WILL ADVANCE
SOUTH AND EAST ACROSS CPA TODAY BEFORE STALLING OUT TO THE SOUTH
OF THE MD LINE TONIGHT INTO THURSDAY. MOIST AND UNSTABLE AIR
AHEAD OF THE COLD FRONT COMBINED WITH INCREASING LOW LEVEL
CONVERGENCE WILL LEAD TO SCT THUNDERSTORM DEVELOPMENT BY THE
AFTERNOON ACROSS THE SOUTHEAST 1/2 TO 1/3 OF THE FCST AREA. THE
INSTABILITY ALONG WITH SUFFICIENT 0-6KM SHEAR AND STEEP LOW
LEVEL LAPSE RATES SHOULD SUPPORT A FEW STRONGER STORMS WITH
POTENTIAL FOR ISOLATED SEVERE WIND GUSTS. SPC ROLLED OVER THE D2
MRGL RISK (LEVEL 1 OUT OF 5) TO D1 WITH A SLIGHT SOUTH/EAST
SHIFT IN THE OUTLOOK AREA. HREF/REFS ALSO INDICATE POTENTIAL FOR
LOCALLY HEAVY RAINFALL >1" NEAR THE MD LINE AS SHOWERS AND
STORMS LIKELY PERSIST THROUGH THE EVENING INTO THE OVERNIGHT
PERIOD ACROSS THE SOUTHERN TIER OF CPA.
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KEY MESSAGE 2:
MAJOR COOLDOWN TO CLOSE OUT THE WEEK AND START MEMORIAL DAY
WEEKEND WITH WIDESPREAD SOAKING RAINFALL OVER 1 INCH FRIDAY AND
SATURDAY
RELIEF FROM THE EARLY SEASON HEAT WAVE ARRIVES IN EARNEST ON
THURSDAY WITH MAX TEMPS 20-30 DEGREES LOWER VS. WEDNESDAY ACROSS
THE LSV. STRONG HIGH PRESSURE SLIDES FROM THE LOWER GREAT LAKES
TO OFF THE NEW ENGLAND COAST TO CLOSE OUT THE WEEK. MODEL DATA
SHOWS THE HIGH CHANNELING SOUTHWARD DOWN THE EAST-SIDE OF THE
APPALACHIANS, SETTING UP A COLD AIR DAMMING (CAD) EVENT HEADING
INTO MEMORIAL DAY WEEKEND.
INCREASING CAD SIGNAL STRENGTH ENHANCED BY MODERATELY STRONG
EAST/SOUTHEAST LOW LEVEL FLOW AND SOAKING RAINFALL HAS PROMPTED
A CONSIDERABLE BEARISH/LOWER ADJUSTMENT TO MAX TEMPS FRIDAY AND
SATURDAY. IN FACT, HIGHS ON SATURDAY ARE NEAR DAILY RECORD LOWS
AT SEVERAL LOCATIONS (MINI/MAX). GUIDANCE MAY BE TOO OPTIMISTIC
IN REBOUNDING TEMPS SUNDAY INTO MONDAY, BUT OPTED TO KEEP
BASELINE NBM FOR NOW. THAT SAID, THE TREND WILL BE TO MODERATE
WARMER WITH STEADIER RAIN GIVING WAY TO MORE SHOWERY CONDITIONS
FOR THE UNOFFICIAL START OF SUMMER.
NBM/WPC QPF CONTINUES TO SHOW WIDESPREAD 48HR RAINFALL TOTALS
IN THE 1-2 INCH RANGE FRIDAY-SATURDAY. THE COOL/STABLE AIR WILL
CAP RATES WITH LONGER DURATION HELPING TO MITIGATE FLOODING
RISK IN MOST AREAS. THE FORECAST RAINFALL IS MUCH NEEDED OVER
THE FAR SOUTH CENTRAL/SOUTHEASTERN COUNTIES WHO REMAIN UNDER
D1-D2 MODERATE TO SEVERE DROUGHT CONDITIONS.
AVIATION /06Z WEDNESDAY THROUGH SUNDAY/
WIDESPREAD VFR CONDITIONS PREVAIL AS OF 01Z WEDNESDAY, WITH
THESE CONDITIONS LIKELY (80-90% CONFIDENCE) TO CONTINUE AT ALL
AIRFIELDS OUTSIDE OF BFD THROUGH ~12Z WEDNESDAY. IN THIS
TIMEFRAME, APPROACHING A LINE OF SHRA WITH EMBEDDED TSRA WILL
APPROACH NW PA CLOSER TO THE ~03/04Z TIMEFRAME. THIS WILL LIKELY
BRING LOW-END VFR TO HIGH-END MVFR CEILINGS WHICH WILL PERSIST
THROUGHOUT THE ENTIRE OVERNIGHT PERIOD AND THROUGHOUT MUCH OF
THE EVENING HOURS ON WEDNESDAY (~22/23Z WEDNESDAY). CLOSER TO
THE 12Z TIMEFRAME, INCREASING SIGNALS FOR IFR AT BFD BASED ON A
CONSENSUS OF HREF ENSEMBLE MEMBERS AND MULTIPLE CYCLES OF GLAMP
MODEL GUIDANCE, SO HAVE DECIDED TO INCLUDE THESE IN THE TAFS
WITH MODERATE (~40-50%) CONFIDENCE ON TIMING. A BRIEF PERIOD OF
LOWER CEILINGS TRENDING TOWARDS LIFR WILL BE POSSIBLE; HOWEVER,
CONFIDENCE REMAINS TOO LOW FOR INCLUSION IN THE 00Z TAFS.
ELSEWHERE, THE AFOREMENTIONED LINE OF SHRA/TSRA IS EXPECTED TO
DIMINISH IN INTENSITY/COVERAGE OVERNIGHT, LEADING MANY AIRFIELDS
UNLIKELY TO RECEIVE ANY SHRA IN THE 00Z-12Z WEDNESDAY
TIMEFRAME. RECENT HREF RUNS HAVE BEEN FAIRLY CONSISTENT WITH THE
PROGRESSION OF A LOW-LEVEL CLOUD DECK ACROSS ALL OF CENTRAL
PENNSYLVANIA, SO HAVE INCLUDED THESE MENTIONS AND SLIGHTLY
ADJUSTED TIMING BASED ON RECENT HREF/NBM/GLAMP MODEL GUIDANCE IN
ORDER TO OUTLINE INITIAL ONSET OF MVFR RESTRICTIONS. THERE IS
HIGH (~70-80%) CONFIDENCE ON SHRA/TSRA REFORMING DURING THE LATE
MORNING TO EARLY AFTERNOON HOURS (MAINLY AFTER 16Z) WITH
INCREASING COVERAGE INTO THE EVENING HOURS. CURRENT SHRA
MENTIONS HAVE BEEN INCLUDED AT ALL TERMINALS ACROSS CENTRAL
PENNSYLVANIA BASED ON RECENT FORECAST/HREF/GLAMP MODEL GUIDANCE
WITH MOST UNCERTAINTY WITH RESPECT TO TIMING. IN TERMS OF TSRA
COVERAGE, THE HIGHEST POTENTIAL AT THIS TIME IS OUTLINED ACROSS
SE PA (MDT/LNS) WHERE ENOUGH INSTABILITY WILL BE PRESENT IN
ORDER FOR SOME MENTIONS IN THE TAF. AT THIS TIME, HAVE TRENDED
TOWARDS PROB30S; HOWEVER, IF THE COLD FRONTAL PASSAGE TRENDS
QUICKER THAN FORECAST, COULD SEE MENTIONS REMOVED AT MDT/LNS IN
FUTURE TAF PACKAGES.
OUTLOOK...
THU...LINGERING SHOWERS ACROSS S PA, RESTRICTIONS POSSIBLE.
FRI...RESTRICTIONS LIKELY WITH RAIN MOVING IN FROM SOUTH TO
NORTH, LASTING INTO FRI NIGHT.
SAT-SUN...RESTRICTIONS LIKELY WITH RAIN.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
WHAT HAS CHANGED...STEINBUGL
KEY MESSAGES...STEINBUGL
DISCUSSION...STEINBUGL
AVIATION...BEATY
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