For the second day in a row, pulse storms developed over the higher terrain of western Pennsylvania during the late afternoon and early evening of August 29, 2021 in a moderate CAPE, low shear environment. One of the storms produced wind damage in northwestern Clearfield County.
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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.
For the second day in a row, pulse storms developed over the higher terrain of western Pennsylvania during the late afternoon and early evening of August 29, 2021 in a moderate CAPE, low shear environment. One of the storms produced wind damage in northwestern Clearfield County.
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 Aug 29, 1:53 PM EST, 1 hour 41 minutes earlier.
Area Forecast Discussion National Weather Service State College PA 253 PM EDT Sun Aug 29 2021 .SYNOPSIS... Humid and unsettled conditions will continue through the end of August with locally heavy downpours possible. Confidence is increasing in the potential for significant heavy rainfall and flooding impacts Wednesday into Thursday as Ida tracks to the south of PA and interacts with a slow moving front. && .NEAR TERM /THROUGH TONIGHT/... Extensive (although thinning) stratus remains entrenched east of the Alleghenies at mid afternoon, with partly to mostly sunny conditions helping to fire scattered convection along and west of the Alleghenies. Some erosion of the stratus is expected through late afternoon and early evening, boosting hourly temps in some areas and impacting convective evolution into the central mountain areas. The slow-moving, terrain-induced, diurnally-driven and generally sub-severe convection will last into mid evening over the western third to half of central PA. Localized rainfall amounts of 1-2 inches are possible and may locally lead to minor flooding issues. Hires models continue to depict showers/storms persisting through the overnight as a prefrontal trough crosses central and southeast areas ahead of a cold front that reaches the lower Great Lakes by 12Z. It will be yet another warm and muggy night, par for the course this August, with fog pockets likely into early Monday morning mainly over the southeast 1/2 of the area. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... Aforementioned cold front will move through the region Monday, leading to scattered showers and thunderstorms. Central PA is still currently not outlooked by SPC for severe weather risk. Highs will range from the upper 70s north to upper 80s southeast Convection should fizzle out by Monday night with cooler/drier air working into the northern tier. 24hrMinT deltas of up to -10 degrees are forecast over this area, but even lows in the upper 50s are still +5-10F above climo to put the recent streak of very warm/muggy nights into perspective. && .LONG TERM /TUESDAY THROUGH SATURDAY/... *Ida Heavy Rainfall/Flooding Threat Wednesday-Thursday* Lingering showers from the frontal passage will diminish by early Tuesday morning. There will likely be a lull in activity before moisture from Ida arrives Tuesday evening to overnight Tuesday into Wednesday. Moderate to heavy rainfall is expected all of Wednesday. Between 3 and 5 inches are forecast for the south-central tier of Pennsylvania, with locally higher amounts possible. Flooding is becoming a growing concern for the south- central tier. The northern tier of Pennsylvania will see moderate rainfall, but there is less of a chance of flooding. Model trends have been bringing the rain farther northward, so this will be something to watch in the coming days. By Thursday afternoon and evening, any residual moisture from Ida will be on the way out. High pressure and associated dry air mass will build in, bringing fair and seasonable weather with much lower humidity Friday and Saturday. Refreshingly cool low temperatures are expected for Friday morning. Expect clear and dry conditions for Friday and Saturday. Guidance hints at some scattered rain showers for Sunday afternoon. && .AVIATION /19Z SUNDAY THROUGH FRIDAY/... 18z outlook... Scattered showers and thunderstorms will dot central PA again this afternoon and early evening. Hit and miss coverage of such precludes strict mention in the terminals at this time. TEMPO groups will be inserted, as storms approach/threaten individual TAF sites. We actually have a TEMPO group inserted from the outset at KBFD, as a cluster of thunderstorms is just to their west. Outside of convection, largely VFR/unrestricted conditions are foreseen, as residual stratus clouds tend to thin out by 18-19z. Later tonight/early Monday, some guidance is suggesting the redevelopment of lower stratus clouds. However, uncertain positioning of a weak surface boundary makes this development more tricky/less certain. The highest confidence of lower cloud formation is over the Susquehanna Valley, so we did bring some MVFR-fuel alternate restrictions in after 07-08z. After lower clouds burn off by late morning Monday, expect mainly VFR once again. Early indications are that diurnal convection on Monday may be more isolated in nature. Outlook... Tue...Low clouds and fog possible in the morning, with isolated-scattered thunderstorms in the afternoon/early evening. Wed...More widespread rainfall/embedded thunderstorms are looking increasingly likely. Thu...Improving weather is foreseen with time. Fri...Mainly VFR. && .CLIMATE... Meteorological Summer (June-July-August 2021) is tracking in the top 10 at both Harrisburg and Williamsport. Very warm nights (avg. minT) are contributing more than hot days (avg. maxT) with both sites currently running in the top-5 warmest on record for average minimum temperature. August is also likely to go down as a top-5 warmest month at both sites. Here are the updated rankings with 3 days left in the month: Harrisburg average temperature (JJA) 1. 2020 77.9F 2. 1966 77.6F 3. 2016 77.3F 4. 2021 77.2F 5. 2010 76.9F Harrisburg average minimum temperature (JJA) 1. 2020 68.2F 2. 2021 68.0F 3. 2016 67.9F 4. 2010 67.6F 5. 2005 67.3F Harrisburg average maximum temperature (JJA) 1. 1966 90.2F 2. 1999 87.7F 3. 2020/1991 87.6F 5. 1943 86.8F 6. 2016 86.7F 7. 1988/1944 86.5F 9. 2021 86.2F Harrisburg average temperature (Aug) 1. 2016 79.1F 2. 2021 78.4F Williamsport average temperature (JJA) 1. 2020/2016 74.4F 3. 1949/1901 74.3F 5. 1900 74.2F 6. 1995/1955 74.0F 8. 2005 73.9F 9. 2021 73.7F 10. 1991 73.6F Williamsport average minimum temperature (JJA) 1. 1901 66.2F 2. 1899 64.0F 3. 2005 63.1F 4. 2021 63.0F 5. 2016 62.8F Williamsport average temperature (Aug) 1. 2016 76.1F 2. 1995 75.9F 3. 2021 75.6F && .CTP WATCHES/WARNINGS/ADVISORIES... None. && SYNOPSIS...DeVoir/Steinbugl NEAR TERM...DeVoir/Steinbugl SHORT TERM...DeVoir/Steinbugl LONG TERM...Gutierrez AVIATION...Jurewicz CLIMATE...
Hazardous Weather Outlook National Weather Service State College PA 458 AM EDT Sun Aug 29 2021 PAZ028-036-042-046-049>053-056>059-063>066-300900- Juniata-Franklin-Sullivan-Southern Lycoming-Union-Snyder-Montour- Northumberland-Columbia-Perry-Dauphin-Schuylkill-Lebanon-Cumberland- Adams-York-Lancaster- 458 AM EDT Sun Aug 29 2021 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and tonight. No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Monday through Saturday. We are continuing to monitor the potential for heavy rain and flooding impacts Wednesday into Thursday in association with Ida. The greatest risk appears to be over the southern part of central Pennsylvania. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. PAZ004>006-010>012-017>019-024>027-033>035-037-041-045-300900- Warren-McKean-Potter-Elk-Cameron-Northern Clinton-Clearfield- Northern Centre-Southern Centre-Cambria-Blair-Huntingdon-Mifflin- Somerset-Bedford-Fulton-Tioga-Northern Lycoming-Southern Clinton- 458 AM EDT Sun Aug 29 2021 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and tonight. Slow-moving thunderstorms with locally heavy downpours could lead to isolated minor flooding issues this afternoon and evening. .DAYS TWO THROUGH SEVEN...Monday through Saturday. We are continuing to monitor the potential for heavy rain and flooding impacts Wednesday into Thursday in association with Ida. The greatest risk appears to be over the southern part of central Pennsylvania. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. MRS
Special Weather Statement
National Weather Service State College PA
424 PM EDT Sun Aug 29 2021
PAZ017-292045-
Clearfield PA-
424 PM EDT Sun Aug 29 2021
...A strong thunderstorm will impact portions of northwestern
Clearfield County through 445 PM EDT...
At 424 PM EDT, Doppler radar was tracking a strong thunderstorm near
DuBois, moving east at 30 mph.
HAZARD...Wind gusts up to 50 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
DuBois, Sandy, Rockton, Falls Creek, Treasure Lake and Penn State
Dubois.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Very heavy rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 4120 7877 4120 7871 4122 7866 4121 7865
4120 7865 4122 7863 4118 7857 4104 7862
4110 7880 4114 7880
TIME...MOT...LOC 2024Z 282DEG 25KT 4118 7878
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH
KFThe State College radar (KCCX), 66 km away, was scanning. The volume nearest the first event began at 20:34 UTC.
1 thunderstorm wind. Local standard time, as filed.
A severe thunderstorm producing winds estimated near 60 mph knocked down multiple trees and wires in Treasure Lake.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2021Every state in 2021This day in weather historyWarnings in Pennsylvania, August 2021
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: 972984.