A mesoscale convective vortex (MCV) pushed across northwestern Pennsylvania and into New York state during the morning and afternoon hours of September 9, 2023. A broken line of showers and storms developed by late morning over the western highlands, and progressed eastward through the afternoon hours.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS CTP wrote it up.
A mesoscale convective vortex (MCV) pushed across northwestern Pennsylvania and into New York state during the morning and afternoon hours of September 9, 2023. A broken line of showers and storms developed by late morning over the western highlands, and progressed eastward through the afternoon hours. Additional storms developed ahead of this broken line. This activity resulted in locally heavy rain and isolated wind damage.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS State College, PA wrote its last area forecast discussion before the first event at Sep 9, 9:50 AM EST, 1 hour 55 minutes earlier.
Area Forecast Discussion National Weather Service State College PA 1050 AM EDT Sat Sep 9 2023 .SYNOPSIS... A cold front will become nearly stationary over Northern and Western PA today into Sunday. Daily showers and thunderstorms will form along and to the east of the front, with the bulk of the convection occurring in the late afternoon and evening hours. Temperatures will settle back close to normal for Sunday into Monday. && .NEAR TERM /THROUGH TONIGHT/... Lightning associated with earlier convection over the western and northern mountains has moved north of the forecast area at this time. A steady rain continues to fall along the Route 219 corridor then eastward along Route 6. SPC guidance now at Slight for the eastern half of the forecast area for the afternoon and evening hours. Excessive rainfall outlook also places us in a slight risk this afternoon. ...Previous discussion... All guidance points to widespread convection developing this afternoon in response to modest heating of the the high- pwat airmass south of a stationary front draped across Northwest PA. Deep layer shear is not that impressive, but locally damaging downbursts are possible with progged capes in the 1000-2000 J/kg range. The moderate instability, combined with pwats around 1.5 inches, should support locally heavy downpours. Latest CAMs indicate the potential of localized 3 inch amounts, mainly over the southeast counties, which could result in minor flooding issues in those locations. Mostly cloudy skies and afternoon convection should hold temperatures down today, especially over the northwest mountains. GEFS 2m temp anomalies indicate highs will be a few degrees below average over the northwest counties and a few above across the Lower Susq Valley, where skies should be a bit brighter. Evening convection should fade overnight, as the boundary layer cools/stabilizes. && .SHORT TERM /SUNDAY THROUGH MONDAY/... Most guidance tracks a remnant upper low over the Tennessee Valley northeast toward PA on Sunday. Increasing large scale forcing and surging pwats ahead of this feature should support a good chance of showers/tsra during the PM hours, as ensemble plumes depict. The combination of high pwats and moderate instability should once again support locally heavy downpours during the afternoon and evening hours, which could result in isolated flooding concerns. The remnant upper low/shortwave and plume of deepest moisture is progged to slide east of the area late Sunday night, causing showers to taper off. Large scale subsidence behind this feature should result in drier weather Monday. However, lingering low level moisture and diurnal heating could support an afternoon shower or thunderstorm in some spots. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... The upper-level trough is likely to remain in place for much of next week and we can expect this to bring daily rounds of scattered showers and thunderstorms. This is supported by ensemble guidance showing agreement with the progressive pattern. Temperatures in the extended period are progged to be much cooler than the hot summer like temperatures we experienced this week. With the upper-level flow of cooler Canadian air pushing into the region, our temps will be near seasonal to slightly below average. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... A few pockets of showers and thunderstorms continue to linger late tonight, moving south to north. Expect fog and low ceilings to again develop overnight with LIFR conditions likely at most sites. Conditions look to be slow to improve Saturday morning, but VFR to MVFR cigs with mainly VFR vsbys should occur after 17Z Sat. Showers and thunderstorms are expected to become widespread across the airspace Saturday afternoon and persist into the evening hours. Outlook... Sun-Mon...Scattered mainly afternoon and early evening showers and storms. Patchy fog to start both days. Tue...AM patchy fog. Otherwise mainly dry with VFR conditions. Showers could return Tuesday night. Wed...VFR with periods of IFR in SHRA/TSRA and areas of morning fog. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && SYNOPSIS...Lambert NEAR TERM...Tyburski SHORT TERM...Fitzgerald LONG TERM...Bauco/Tyburski AVIATION...Gartner/Bauco
Hazardous Weather Outlook National Weather Service State College PA 438 AM EDT Sat Sep 9 2023 PAZ004-100845- Warren- 438 AM EDT Sat Sep 9 2023 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and tonight. The probability for widespread hazardous weather is low. .DAYS TWO THROUGH SEVEN...Sunday through Friday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. PAZ005-006-010>012-017>019-024>028-033>036-045-056-063-064-100845- McKean-Potter-Elk-Cameron-Northern Clinton-Clearfield- Northern Centre-Southern Centre-Cambria-Blair-Huntingdon-Mifflin- Juniata-Somerset-Bedford-Fulton-Franklin-Southern Clinton-Perry- Cumberland-Adams- 438 AM EDT Sat Sep 9 2023 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and tonight. Thunderstorms will affect most of the area this afternoon or evening. Some of the storms could become strong enough to produce damaging wind gusts or flooding rain in a few isolated locations. .DAYS TWO THROUGH SEVEN...Sunday through Friday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. PAZ037-041-042-046-049>053-057>059-065-066-100845- Tioga-Northern Lycoming-Sullivan-Southern Lycoming-Union-Snyder- Montour-Northumberland-Columbia-Dauphin-Schuylkill-Lebanon-York- Lancaster- 438 AM EDT Sat Sep 9 2023 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and tonight. Thunderstorms will affect most of the area this afternoon or evening. Some of the storms could become strong enough to produce damaging wind gusts or flooding rain in a few isolated locations. .DAYS TWO THROUGH SEVEN...Sunday through Friday. Afternoon and evening thunderstorms could produce isolated flooding on Sunday. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The State College radar (KCCX), 38 km away, was scanning. The volume nearest the first event began at 16:46 UTC.
3 thunderstorm wind, 2 flood. Local standard time, as filed.
Multiple rounds of downpours caused Muddy Run to leave it's banks in the vicinity of Smoke Run in Bigler Township, flooding one home.
A severe thunderstorm producing winds estimated near 60 mph knocked down multiple trees across Jacksonville Road east-northeast of Bellefonte.
A severe thunderstorm producing winds estimated near 60 mph knocked down trees and wires across Klump Road northeast of Balls Mills.
Flooding of a small stream pushed water across a section of Beauty's Run Road.
A severe thunderstorm producing winds estimated near 70 mph knocked down multiple trees along with snapping off multiple large limbs with debris thrown around the area in Port Trevorton.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2023Every state in 2023This day in weather historyWarnings in Pennsylvania, September 2023
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1129038, 1128995, 1128996, 1129040, 1128997.