An isolated severe thunderstorm developed over the Allegheny Plateau in the early afternoon of August 21, 2017 and knocked down a couple of trees in 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.
An isolated severe thunderstorm developed over the Allegheny Plateau in the early afternoon of August 21, 2017 and knocked down a couple of trees in 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 21, 10:01 AM EST, 1 hour 59 minutes earlier.
Area Forecast Discussion National Weather Service State College PA 1101 AM EDT Mon Aug 21 2017 .SYNOPSIS... High pressure moving off the Mid Atlantic coast will bring a warm and increasingly humid southerly flow to the region into Tuesday. A strong cold front will move through the region late Tuesday and Tuesday night. Cooler and drier conditions will return for the second half of the week. && .NEAR TERM /THROUGH TONIGHT/... Today is picky your model for clouds and see which one gets eclipsed. The HRRR is only partly cloud but has more intense clouds where each run develops thunderstorms. So for clouds simply blended the NBM clouds with hourly mesoscale models. Made it blotchy where these models indicated thunderstorms or showers. But lowered amounts verse most of the larger scale models with convective parameterizations would create. Most of the mesoscale guidance implies chance POPS and better and slightly more organized showers/thunderstorms in eastern areas this afternoon. The HREF-V2 and NCAR-3km show this and CAMS are your best forecast. But successive HRRR runs are not as robust. Message is POP showers this afternoon and weak organization in east. So a warmer day more humid than yesterday. && .SHORT TERM /TUESDAY/... Nudged these grids with newer guidance and tried to show increased chance as the sun gets higher in the sky. NCAR EFS and NCEP HREF are at odds for convection timing. NCAR is far faster. Big news is a warm humid day good chance of thunderstorms and strong thunderstorms. And the front will usher in a cool trend. Previous: The big weather maker still looks to be a potent late summer cold front that will pass through the region Tuesday evening into early Wednesday. Consensus model timing shows the front just entering NWRN PA by 8PM Tuesday/00Z Wednesday. Models develop just some modest CAPE east of the front over much of central and western PA. The exception is over eastern PA in what appears to be a lee side surface trough feature. The ECMWF/GFS and the ensembles all develop a finger of moderate to strong instability over SERN areas along the coastal plain. Deep level shear is also progged to increase and exceed 35kt. Interesting to note that the GEFS shows very little unstable air from the cold front into central PA and the SREF which paints more CAPE overall, has a distinct minimum of instability over our area during the day into the evening. This suggests there could be a fair amount of pre-frontal cloudiness hindering heating. The whole region is painted under a Slight Risk which seems based more on expected impressive wind fields than model generated instability. Highs are still expected to rise into the 80s, to around 90 over southern areas before the clouds increase ahead of the front. A very humid airmass will make it feel warmer. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... After our surge of heat and humidity, the strong front will bring a noticeably cooler and drier airmass to the region starting midweek and lasting through the end of the week into the weekend. Interesting to note that the deterministic models show 850 temps as cold as 2-3C just north of the Canadian border behind the cold front, a reminder the change in seasons is not all that far away. Chilliest readings look to be the mornings of Fri/Sat/Sun with high centered overhead, dipping lows into the 40s over the Northern Mountains (and deeper valleys of the Central Mountains) and solidly into the 50s elsewhere. && .AVIATION /15Z MONDAY THROUGH FRIDAY/... Some low clouds still burning off in the southeast. A few showers popping up to our west. First shower of the day in Huntingdon County fizzled. Models suggest we should see showers and storms scattered about this afternoon. Most CAM guidance says after 18Z we should see evolving showers and storms. Warm overnight with patchy fog possible. .OUTLOOK... Tue...Patchy AM fog poss. Late day/evening tsra impacts poss. Wed...Early AM low cigs poss BFD/JST. Thu-Fri...No sig wx expected. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && SYNOPSIS...La Corte NEAR TERM...Grumm SHORT TERM...Grumm/La Corte LONG TERM...La Corte AVIATION...Grumm/Martin
Hazardous Weather Outlook National Weather Service State College PA 409 AM EDT Mon Aug 21 2017 PAZ028-036-042-046-049>053-056>059-063>066-220815- Juniata-Franklin-Sullivan-Southern Lycoming-Union-Snyder-Montour- Northumberland-Columbia-Perry-Dauphin-Schuylkill-Lebanon-Cumberland- Adams-York-Lancaster- 409 AM EDT Mon Aug 21 2017 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and Tonight. There will be a Marginal Risk of severe thunderstorms this afternoon and evening. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. There will be a Slight Risk of severe thunderstorms Tuesday afternoon and evening. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. PAZ004>006-010>012-017>019-024>027-033>035-037-041-045-220815- Warren-McKean-Potter-Elk-Cameron-Northern Clinton-Clearfield- Northern Centre-Southern Centre-Cambria-Blair-Huntingdon-Mifflin- Somerset-Bedford-Fulton-Tioga-Northern Lycoming-Southern Clinton- 409 AM EDT Mon Aug 21 2017 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and Tonight. The probability of widespread severe weather will be low. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. There will be a Slight Risk of severe thunderstorms Tuesday afternoon and evening. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
Special Weather Statement National Weather Service State College PA 1246 PM EDT MON AUG 21 2017 PAZ017>019-211730- Northern Centre PA-Clearfield PA-Southern Centre PA- 1246 PM EDT MON AUG 21 2017 ...SPECIAL WEATHER STATEMENT... At 1246 PM EDT, Doppler radar indicated a strong thunderstorm near Hyde, moving east at 25 mph. Pea size hail and winds in excess of 30 mph are possible. Locations impacted include... Clearfield, Black Moshannon State Park, Curwensville, Plymptonville, Jeffries, North Philipsburg, Osceola Mills, Moshannon, Clarence, Woodland, Hyde, South Philipsburg, Snow Shoe, Philipsburg, Chester Hill, Julian, West Decatur, Kylertown, Grassflat and Wallaceton. LAT...LON 4085 7854 4103 7854 4109 7788 4082 7787 TIME...MOT...LOC 1646Z 268DEG 27KT 4095 7845 Grumm
The State College radar (KCCX), 38 km away, was scanning. The volume nearest the first event began at 17:02 UTC.
1 thunderstorm wind. Local standard time, as filed.
A severe thunderstorm producing winds estimated near 60 mph knocked down two trees in Clearfield Borough.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2017Every state in 2017This day in weather historyWarnings in Pennsylvania, August 2017
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: 712600.