Storms developed head of an approaching cold front in a moderate CAPE / high shear environment, producing sporadic wind damage across Tioga County during the afternoon of July 20, 2017.
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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.
Storms developed head of an approaching cold front in a moderate CAPE / high shear environment, producing sporadic wind damage across Tioga County during the afternoon of July 20, 2017.
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 Jul 20, 1:21 PM EST, 52 minutes earlier.
Area Forecast Discussion National Weather Service State College PA 221 PM EDT Thu Jul 20 2017 .SYNOPSIS... Pennsylvania will be on the northern periphery of a subtropical ridge passing across the southern states through the weekend. A slow moving cold front will push through the area early next week. && .NEAR TERM /UNTIL 8 PM THIS EVENING/... Shortwave energy/weak defined cold front moving across the eastern Great lakes is helping to force strong to severe convection east of Lake Ontario. Broken line of weaker showers/storms is trying to develop over northwest PA. Both areas are moving E/SE and will have potential impact on parts of central PA later this afternoon and evening. Severe Thunderstorm Watch #424 included Tioga and Sullivan counties until 8PM. Elsewhere, isolated showers/storms remain possible into this evening, but most places will be rain free today. Hot and very humid weather will continue across the CWA at least today and tomorrow. Across the Lower Susq Valley, combination of heat and humidity will likely push heat indices above 100F for at least a couple of hours later this afternoon. Thus have issued a Heat Advisory til 8PM for of the lower susq counties and as far west as Fulton County. && .SHORT TERM /8 PM THIS EVENING THROUGH 6 PM FRIDAY/... Both SPC SSEO and NCAR ensemble suggest a dwindling band of convection will push southeast across the region overnight, as best forcing ahead of shortwave shifts into New England and trailing low level jet sags south across Pa. Large scale subsidence and arrival of much lower PWATs progged for Friday, resulting in a mostly sunny day for most if not all of the forecast area. Have maintained just a slight chance of a lingering shower across Somerset county, which will remain on northern edge of ring of fire. GEFS mean 850 temps still around 17C-18C Friday, which should translate to max temps from the low 80s over the northern mountains, to the low 90s in the Susq Valley. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... The Day 2 MRGL risk extends into west-central PA on the eastern extent of upstream organized convective zone. Over the weekend, pcpn pattern looks to reach a relative peak with max POPs based on multi-model blend. Exact timing and location of pcpn will depend on details not well resolved until the very short term time frame. Therefore the later periods will keep a 40-60 percent POP given lack of confidence in highlighting any specific areas/timeframe with concentrated pcpn potential. Medium range models generally agree that a continued/gradual weakening and east-southeast shift of the persistent central U.S. upper ridge can be expected with time, as shortwave troughing shifts slowly southeast out of the Canadian Prairie across the northeast quarter of the country by early next week. The associated cold front is progged by med range guidance to push slowing southeast through the forecast area early next week. Above average temperatures (+5-10 degree max T departures) should trend toward mid to late July climo numbers by next Tue-Wed. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... A weak cold front moving across the eastern Great lakes is helping to force strong to severe convection/thunderstorms east of Lake Ontario. Broken line of weaker showers/storms is trying to develop over northwest PA. Both areas are moving E/SE and will have potential impact on parts of the airspace, mainly northern TAF sites, this afternoon and evening. Severe Thunderstorm Watch #424, including Tioga and Sullivan counties, is in effect until 8PM. Elsewhere, isolated showers/storms remain possible into this evening, but confidence remains too low to include at other TAF sites with most air fields will be rain free today. Tonight, scattered convection over central mtns will be diminishing. Areas of valley fog will again become likely, with CIG restrictions poss over the NW. Isolated TSRA poss on Fri, with VFR otherwise. TSRA become likely again for Sat and Sun as humid airmass remains in place. .OUTLOOK... Fri...AM valley fog. Cig restrictions likely NW half. Isolated TSRA. Sat-Sun...AM valley fog poss. TSRA likely. Mon and Tue...AM valley fog poss. Scattered TSRA. && .CTP WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM EDT this evening for PAZ035-036-056- 057-059-063>066. && SYNOPSIS...Fitzgerald/Gartner NEAR TERM...Fitzgerald/Gartner SHORT TERM...Fitzgerald/Gartner LONG TERM...Fitzgerald/Steinbugl AVIATION...DeVoir/Gartner
Hazardous Weather Outlook National Weather Service State College PA 113 PM EDT Thu Jul 20 2017 PAZ026>028-033-034-050-211715- Huntingdon-Mifflin-Juniata-Somerset-Bedford-Snyder- 113 PM EDT Thu Jul 20 2017 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...This Afternoon and Tonight. The probability for widespread hazardous weather is low. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. Severe thunderstorms with damaging winds 60 mph or greater and large hail exceeding 1 inch in diameter are possible Saturday afternoon or evening. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. PAZ035-036-056-057-059-063>066-211715- Fulton-Franklin-Perry-Dauphin-Lebanon-Cumberland-Adams-York- Lancaster- 113 PM EDT Thu Jul 20 2017 ...HEAT ADVISORY IN EFFECT UNTIL 8 PM EDT THIS EVENING... This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...This Afternoon and Tonight. Please listen to NOAA Weather Radio or go to weather.gov/StateCollege on the internet for more information about the following hazards. Heat Advisory. Dangerous heat conditions are possible this afternoon with maximum heat index values approaching 100 degrees. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. Severe thunderstorms with damaging winds 60 mph or greater and large hail exceeding 1 inch in diameter are possible Saturday afternoon or evening. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. PAZ037-042-211715- Tioga-Sullivan- 113 PM EDT Thu Jul 20 2017 ...SEVERE THUNDERSTORM WATCH 424 IN EFFECT UNTIL 8 PM EDT THIS EVENING... This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...This Afternoon and Tonight. Please listen to NOAA Weather Radio or go to weather.gov/StateCollege on the internet for more information about the following hazards. Severe Thunderstorm Watch. Severe thunderstorms with damaging winds 60 mph or greater and large hail exceeding 1 inch in diameter are possible this afternoon or evening. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. PAZ004>006-010>012-041-045-046-211715- Warren-McKean-Potter-Elk-Cameron-Northern Clinton-Northern Lycoming- Southern Clinton-Southern Lycoming- 113 PM EDT Thu Jul 20 2017 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...This Afternoon and Tonight. Severe thunderstorms with damaging winds 60 mph or greater and large hail exceeding 1 inch in diameter are possible this afternoon or evening. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. PAZ049-051>053-058-211715- Union-Montour-Northumberland-Columbia-Schuylkill- 113 PM EDT Thu Jul 20 2017 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...This Afternoon and Tonight. The probability for widespread hazardous weather is low. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. PAZ017>019-024-025-211715- Clearfield-Northern Centre-Southern Centre-Cambria-Blair- 113 PM EDT Thu Jul 20 2017 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...This Afternoon and Tonight. Severe thunderstorms with damaging winds 60 mph or greater and large hail exceeding 1 inch in diameter are possible this evening. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. Severe thunderstorms with damaging winds 60 mph or greater and large hail exceeding 1 inch in diameter are possible Saturday afternoon or evening. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The Binghamton radar (KBGM), 97 km away, was scanning. The volume nearest the first event began at 19:13 UTC.
5 thunderstorm wind. Local standard time, as filed.
A severe thunderstorm producing winds estimated near 60 mph tore a portion of a roof off of a house on Ryon Circle in Lawrenceville.
A severe thunderstorm producing winds estimated near 60 mph knocked down trees and wires across Route 287 at School Road.
A severe thunderstorm producing winds estimated near 60 mph knocked down wires across East Lawrence Road.
A severe thunderstorm producing winds estimated near 60 mph knocked down numerous large trees in Lawrenceville.
A severe thunderstorm producing winds estimated near 60 mph knocked down multiple large trees and wires in Mansfield.
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, July 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: 705638, 705639, 705640, 705641, 705642.