641
FXUS61 KCTP 021810
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
210 PM EDT WED SEP 2 2026
WHAT HAS CHANGED
* ADDED THUNDER MENTIONS THROUGHOUT MUCH OF THE AVIATION
FORECAST PERIOD
* DROPPED SVR WATCH AS STORMS MOVED OFF TO THE SOUTH.
* WESTERN ZONES WILL LIKELY DESTABILIZE AGAIN LATER TODAY AND
THIS EVENING.
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: LATE SUMMER SURGE OF HEAT AND HUMIDITY BRINGS
MULTI-DAY SEVERE THUNDERSTORM AND EXCESSIVE RAINFALL THREAT TO
KICKOFF SEPTEMBER
A SERIES OF MID LEVEL IMPULSES TRACKING EASTWARD ALONG THE
NORTHERN PERIPHERY OF AN EXPANSIVE 500MB RIDGE WILL CONTINUE TO
INTERACT WITH ANOMALOUS MOISTURE/INSTABILITY AND STRONG WNW FLOW
ALOFT TO PROMOTE SEVERE STORM AND EXCESSIVE RAIN RISK TODAY AND
TOMORROW.
THE FIRST CLUSTER OF STORMS IS ALREADY POISED TO MOVE OFF OF
LAKE ERIE INTO OUR NW ZONES BETWEEN 7 AND 8 AM. THIS CLUSTER HAS
NEAR CONTINUOUS LIGHTNING AND WAS SEVERE WARNED ALONG THE LAKE
SHORE BY THE CLEVELAND WFO. INLAND FROM THE LAKE SHORE, THE SFC
BOUNDARY LAYER IS STILL RATHER STABLE THIS MORNING WITH NEAR
150 J/KG OF SBCIN, SO THIS WILL AT LEAST SOMEWHAT OFFSET THE
SEVERE WIND POTENTIAL ACROSS OUR NW ZONES. HOWEVER THE WIND
THREAT COULD INCREASE TO THE SOUTH AND EAST IF THE CLUSTER IS
MAINTAINED UNTIL MID-MORNING, BY WHICH TIME MORNING SUNSHINE
WILL HAVE ERODED THE SFC STABLE LAYER. CLIMATOLOGICALLY,
HOWEVER, THESE MORNING MCSS RARELY SURVIVE THE NOCTURNAL TO
DIURNAL TRANSITION, AND SEVERAL CAMS DO SHOW IT FALLING APART
BEFORE THE BOUNDARY LAYER DESTABILIZES.
THE MESOSCALE SEVERE WEATHER SETUP WILL BE COMPLEX THIS
AFTERNOON INTO THIS EVENING, WITH KEY PLAYERS BEING THE PRESENCE
OF A NORTH-SOUTH STATIONARY FRONT / BACKDOOR COLD FRONT ACROSS
THE EASTERN ZONES, AND WHATEVER REMAINS OF THE COLD POOL FROM
THE MORNING MCS. THESE BOUNDARIES WILL LIKELY BE THE FOCUS FOR
NEW CONVECTION INITIATION THIS AFTERNOON. FORECAST VERTICAL SOUNDINGS
DEPICT LARGE, CLOCKWISE TURNING HODOGRAPHS ASSOCIATED WITH A
STRONGLY VEERED WIND PROFILE, WITH 0-3 KM SRH ON THE ORDER OF
200-350 M2/S2 AND 0-3KM WIND SHEAR APPROACHING 40 KTS. COMBINED
WITH MLCAPE ON THE ORDER OF 1500-3000 J/KG, THIS SETUP WILL
LIKELY YIELD BOTH SUPERCELLS AND BOWING LINE SEGMENTS. IF
SUPERCELLS OR SOUTHEAST-BULGING BOW ECHOS REMAIN ON THE UNSTABLE
SIDE OF THE STATIONARY BOUNDARY AND INGEST THIS HIGHLY SHEARED
INFLOW, A COUPLE STRONGER TORNADOES AND LARGE HAIL STORMS CAN
NOT BE RULED OUT THIS AFTERNOON INTO THIS EVENING. THERE WILL BE
A LARGE CAPE GRADIENT ACROSS THE STATIONARY FRONT, WITH LIMITED
SEVERE POTENTIAL TO ITS EAST.
INCREASED SOUTHWEST TO WESTERLY FLOW ON THURSDAY WILL PUSH THE
BACKDOOR COLD FRONT OUT OF THE REGION, USHERING IN HIGHER
TEMPERATURES AND DEWPOINTS. THE HEAT INDEX WILL MAKE ANOTHER RUN
AT 100-104F ACROSS THE SOUTHERN ZONES, SIMILAR TO WHAT WE SAW ON
TUESDAY. WE ISSUED A HEAT ADVISORY VALID 11A-8P THU FOR THIS
LIKELY THREAT.
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 ADDITIONAL SHOWERS AND STORMS
ON FRIDAY, BUT FORTUNATELY THE LABOR DAY WEEKEND IS TRENDING
DRIER. THE UPPER RIDGE IS FORECAST TO RETROGRADE BY THE END OF
THE WEEK WHICH ALLOWS FOR A RETURN TO MORE SEASONAL TEMPERATURES.
AVIATION /18Z WEDNESDAY THROUGH MONDAY/
SOME OF THE LEAST CERTAIN TERMINAL FORECASTS I HAVE EVER MADE,
EVEN DURING LAKE EFFECT SNOWS. THE POSSIBILITY, BUT NOT
CERTAINTY, OF CONVECTION EXISTS THROUGHOUT THE ENTIRE TAF
PERIOD FOR ALMOST ALL SITES. POINTING OUT A FEW MORE-LIKELY
TIMES ARE THE BEST I COULD DO AT THIS POINT. AFTER A PATCH OF
SHRA/TSRA AFFECTS IPT THIS AFTN, IT COULD SLIDE S INTO MDT/LNS,
BUT IT IS NOT MORE THAN A 40% CHC OF GETTING TO THOSE TWO SITES.
MOST GUIDANCE THEN DEVELOPS CONVECTION OVER WESTERN PA AND
SLIDING INTO THE AIRSPACE OVER CENTRAL PA BEFORE 22Z. THAT
POSSIBLE AREA OF SHRA/TSRA COULD (50%) LAST INTO THE LATE
EVENING WHILE INCHING EASTWARD. A SIGNIFICANT PUSH OF FORCING
MOVES IN FROM NY TOWARD 03Z. THE BATCH OF CONVECTION IT WILL
FIRE UP HAS BEEN FAIRLY CONSISTENT WITH PREVIOUS GUIDANCE AND
WOULD DROP INTO A POOL OF VERY LOW STABILITY AND HIGH MOISTURE.
THESE SHRA/TSRA WOULD CERTAINLY DROP INTO BFD AND THEN IPT-UNV.
THEY COULD SURVIVE INTO THE SOUTHERN HALF OF THE AIRSPACE FOR
THE POST- SUNRISE HOURS. I WOULD HAVE PUT MORE/LOWER VISBY FOG
INTO THE TERMINALS IF I THOUGHT IT WOULD CLEAR OUT AFTER THE SUN
SETS. STILL MENTIONED A PERIOD OF FOG FOR THE WESTERN TERMINALS
LATER TONIGHT.
OUTLOOK...
THU...SCATTERED-NUMEROUS SHRA/TSRA WITH BRIEF RESTRICTIONS
POSSIBLE; MORNING FOG.
FRI...SCATTERED SHRA/TSRA SW. VFR ELSEWHERE AFTER MORNING FOG.
SAT-MON...VFR FAVORED; MORNING FOG POSSIBLE.
CTP WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY FROM 11 AM TO 8 PM EDT THURSDAY FOR PAZ026>028-
035-036-056-057-059-063>066.
WHAT HAS CHANGED...DANGELO/COLBERT
KEY MESSAGES...STEINBUGL/COLBERT
DISCUSSION...STEINBUGL/COLBERT
AVIATION...DANGELO
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