A line of showers and thunderstorms developed in a moderately unstable airmass over south-central Pennsylvania, just ahead of an approaching cold front. This line of storms produced several reports wind damage from Franklin County eastward to Lancaster County, as well as a couple of severe hail reports in Lancaster 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.
A line of showers and thunderstorms developed in a moderately unstable airmass over south-central Pennsylvania, just ahead of an approaching cold front. This line of storms produced several reports wind damage from Franklin County eastward to Lancaster County, as well as a couple of severe hail reports in Lancaster 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 Sep 5, 9:51 AM EST, 4 hours 44 minutes earlier.
Area Forecast Discussion National Weather Service State College PA 1051 AM EDT Tue Sep 5 2017 .SYNOPSIS... A cold front will progress very slowly across the state during the day today, bringing showers and some strong thunderstorms. A deepening upper level trough will march east across the commonwealth Wednesday into Thursday, leading to cooler than normal temperatures and scattered showers. That will be followed by a dry but cool weekend. && .NEAR TERM /UNTIL 7 PM THIS EVENING/... More showers developing along the cold front which has not yet passed through KBFD. Tough to pick out short wave/vort max moving overhead on sat pics, but models do have some spin and good lift is flaring up convection over the SW. Current sunshine and good heating in the SE are all in line with going fcst. have only tweaked the POPs and wx grids slightly. Temps seem pretty solid as well. Dewpoints were too low in the NW where the front has yet to pass. Storms still expected to get worst in the SE, as RAP Prev... Remnants of earlier convection sliding off to the NE early this morning. But additional convection continues off to the west and SW ahead of slowly approaching cold front. This front will continue to be the focus for showers/thunderstorms today - with convection strengthening midday over central and southern mountains and becoming strong to severe as it shifts to the Susq Valley. Trough digging over the Great Lakes/Ohio Valley will keep strongest mid-level flow (~70kts) aligned over the front. Best deep-layer shear and heating begins in a corridor over the Susq Valley stretching to the NE, which looks to be enough to strengthen convection enough to justify a Slight Risk there. && .SHORT TERM /7 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... The upper flow gradually backs to the southwest on Wednesday helping to slow the cold front to a crawl with an area of anafrontal rain blossoming and moving NE across the southeast part of the region Tuesday night into Wednesday - gradually shifting eastward Wed night. The clouds and rain showers will keep temps below normal during this period. && .LONG TERM /THURSDAY THROUGH MONDAY/... Would expect most of the showers and storms to be out of the area Thursday, but still some chance of a shower across the north into Friday morning as the upper level trough finally swings across. Large high builds into the area for next weekend. Weather looks to be dry but temps will remain on the cool side. After that, heading into early next week, interaction between the departing high pressure area and Hurricane Irma will determine the track it will take as it approaches the U.S East Coast. Still quite a wide variation of solutions forecast by longer term guidance after it slides by the northern Bahamas, so stay tuned for now. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... STill some thunder lingering over BFD as the cold front has not yet passed there - wind still from the SW dewpoint 63F. SHRA/TSRA already flaring up over SWrn PA and zipping very quickly to the ENE - these should begin to affect JST/AOO/UNV within the next hour or two and IPT not long after that. MDT/LNS have sfc-based cu already developing as the temps are getting into the m70s. High clouds should keep the heating rather slow - but cu will likely become TSRA around or shortly after 18Z in the SE. Will add some timing for TS in the TAFs, but still keep it rather broadbrushed for now - esp with the speed of the cells being so quick. Prev.. Ceiling reductions are mainly at BFD as the progression of the southern end of the line of showers has stalled. However as of the 12Z radar showers continue to spread slowly into central PA. Expect some SHRA at JST and then at AOO and UNV by mid morning. These showers will make there way east and will encompass much of NW half of CWA. These spread into central and SE portions on Tue as numerous showers and scattered thunderstorms impact those regions as the front stalls nearby. The line will strengthen through the SE this afternoon bringing SHRA and TSRA to the Eastern TAF sites between 18Z and 00Z. Have left TSRA out of the TAFS due to timing however MDT and LNS could see periods of IFR from TSRA late this afternoon. After frontal passage some showers should linger this evening into the overnight hours. .Outlook... Wed...Reductions poss in SHRA - mainly NW mtns and east of Susq River. Thu/Fri...Widespread MVFR north. VFR elsewhere. Sct showers mainly north. Sat...No sig wx. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && SYNOPSIS...RXR NEAR TERM...Dangelo/RXR SHORT TERM...RXR LONG TERM...Gartner/RXR AVIATION...Dangelo/Ceru
Hazardous Weather Outlook National Weather Service State College PA 326 PM EDT Tue Sep 5 2017 PAZ004>006-010>012-017>019-024>028-033>035-037-041-042-045-046- 049>053-061930- Warren-McKean-Potter-Elk-Cameron-Northern Clinton-Clearfield- Northern Centre-Southern Centre-Cambria-Blair-Huntingdon-Mifflin- Juniata-Somerset-Bedford-Fulton-Tioga-Northern Lycoming-Sullivan- Southern Clinton-Southern Lycoming-Union-Snyder-Montour- Northumberland-Columbia- 326 PM EDT Tue Sep 5 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...Wednesday through Monday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. PAZ036-056>059-063>066-061930- Franklin-Perry-Dauphin-Schuylkill-Lebanon-Cumberland-Adams-York- Lancaster- 326 PM EDT Tue Sep 5 2017 ...SEVERE THUNDERSTORM WATCH 480 IN EFFECT UNTIL 9 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. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotters are asked to report any significant weather or damage to the NWS through normal reporting methods.
Special Weather Statement National Weather Service State College PA 252 PM EDT TUE SEP 5 2017 PAZ026>028-034>036-056-063-064-051930- Perry PA-Bedford PA-Fulton PA-Adams PA-Franklin PA-Cumberland PA- Juniata PA-Huntingdon PA-Mifflin PA- 252 PM EDT TUE SEP 5 2017 ...STRONG THUNDERSTORMS WILL AFFECT PARTS OF BEDFORD...ADAMS... HUNTINGDON...FRANKLIN...MIFFLIN...JUNIATA...FULTON...CUMBERLAND...AND PERRY COUNTIES UNTIL 330 PM EDT... At 252 PM EDT, Doppler radar indicated strong thunderstorms along a line extending from Doylesburg to Berkeley Springs. Movement was northeast at 45 mph. Winds in excess of 40 mph are possible. Locations impacted include... Chambersburg, Waynesboro, Shippensburg, Greencastle, Carlisle, St. Thomas, Plainfield, Wayne Heights, Ickesburg, Fort Loudon, Locust Grove, Barnes Gap, Mercersburg, New Bloomfield, Guilford, Willow Hill, Big Cove Tannery, Rockhill Furnace, Big Spring State Park and Spruce Hill. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with these storms, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. Frequent cloud to ground lightning is occurring with these storms. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. && LAT...LON 3972 7849 4051 7766 4058 7706 3972 7744 TIME...MOT...LOC 1852Z 239DEG 41KT 4023 7771 3962 7824 CR
The Sterling radar (KLWX), 92 km away, was scanning. The volume nearest the first event began at 19:35 UTC.
12 thunderstorm wind, 2 hail. Local standard time, as filed.
A severe thunderstorm producing winds estimated near 60 mph knocked down trees onto Leitersburg Road in Greencastle.
A wind gust of 65 mph was measured in Greencastle.
A severe thunderstorm producing winds estimated near 60 mph knocked down large trees onto Marsh Road.
A severe thunderstorm producing winds estimated near 60 mph knocked down trees near Cashtown.
A wind gust of 70 mph was measured near Cashtown in Adams County.
A severe thunderstorm producing straight-line winds estimated near 80 mph snapped several trees and knocked down eight poles in York and West York.
A severe thunderstorm producing winds estimated near 60 mph knocked down trees and wires near Parkville.
A severe thunderstorm producing winds estimated near 70 mph knocked down numerous trees and wires in Columbia.
A severe thunderstorm producing winds estimated near 60 mph knocked down trees adn wires in North Palmyra.
A severe thunderstorm producing winds estimated near 60 mph knocked down a tree across Iron Bridge Road north of Columbia.
A severe thunderstorm produced quarter-sized hail near Landisville.
A severe thunderstorm producing winds estimated near 60 mph knocked down large trees in East Lancaster.
A severe thunderstorm producing winds estimated near 60 mph knocked down a large tree onto a townhouse in Lancaster.
A severe thunderstorm produced golf ball sized hail in Lancaster.
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, September 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: 715518, 715520, 714979, 714980, 715523, 715506, 715507, 715508, 715510, 715512, 714977, 715515, 715516, 714978.