Alert archive / Pennsylvania / Severe Thunderstorm Watches in 2017
Severe Thunderstorm Watch 439
The Storm Prediction Center issued this severe thunderstorm watch at Aug 4, 2017, 1:25 PM EDT for 4 states. It was in force for 8 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 4, 2017, 1:25 PM EDT (17:25 UTC)
- Expired
- Aug 4, 2017, 9:00 PM EDT
- In force
- 8 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 55 kt
All 114 counties
Allegany County, NY, Broome County, NY, Cattaraugus County, NY, Cayuga County, NY, Chautauqua County, NY, Chemung County, NY, Chenango County, NY, Cortland County, NY, Erie County, NY, Genesee County, NY, Jefferson County, NY, Lewis County, NY, Livingston County, NY, Madison County, NY, Monroe County, NY, Niagara County, NY, Oneida County, NY, Onondaga County, NY, Ontario County, NY, Orleans County, NY, Oswego County, NY, Schuyler County, NY, Seneca County, NY, Steuben County, NY, Tioga County, NY, Tompkins County, NY, Wayne County, NY, Wyoming County, NY, Yates County, NY, Ashland County, OH, Ashtabula County, OH, Belmont County, OH, Carroll County, OH, Columbiana County, OH, Coshocton County, OH, Cuyahoga County, OH, Geauga County, OH, Guernsey County, OH, Harrison County, OH, Holmes County, OH, Jefferson County, OH, Knox County, OH, Lake County, OH, Lorain County, OH, Mahoning County, OH, Medina County, OH, Monroe County, OH, Muskingum County, OH, Noble County, OH, Portage County, OH, Stark County, OH, Summit County, OH, Trumbull County, OH, Tuscarawas County, OH, Wayne County, OH, Adams County, PA, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Bedford County, PA, Blair County, PA, Bradford County, PA, Butler County, PA, Cambria County, PA, Cameron County, PA, Centre County, PA, Clarion County, PA, Clearfield County, PA, Clinton County, PA, Columbia County, PA, Crawford County, PA, Cumberland County, PA, Dauphin County, PA, Elk County, PA, Erie County, PA, Fayette County, PA, Forest County, PA, Franklin County, PA, Fulton County, PA, Greene County, PA, Huntingdon County, PA, Indiana County, PA, Jefferson County, PA, Juniata County, PA, Lancaster County, PA, Lawrence County, PA, Lebanon County, PA, Lycoming County, PA, McKean County, PA, Mercer County, PA, Mifflin County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Potter County, PA, Schuylkill County, PA, Snyder County, PA, Somerset County, PA, Sullivan County, PA, Tioga County, PA, Union County, PA, Venango County, PA, Warren County, PA, Washington County, PA, Westmoreland County, PA, York County, PA, Brooke County, WV, Hancock County, WV, Marion County, WV, Marshall County, WV, Monongalia County, WV, Ohio County, WV, Preston County, WV, Wetzel County, WV
The radar
The Buffalo radar (KBUF), 105 km from the middle of the area, began a volume at 17:28 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 10%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 50%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 60%
Warnings issued inside it
70 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 4, 1:26 PM EDT | Severe Thunderstorm Warning | PBZ | Belmont | 49 min |
| Aug 4, 1:34 PM EDT | Severe Thunderstorm Warning | PBZ | Greene, Washington | 26 min |
| Aug 4, 1:41 PM EDT | Severe Thunderstorm Warning | BUF | Erie, Genesee, Wyoming | 49 min |
| Aug 4, 2:01 PM EDT | Severe Thunderstorm Warning | PBZ | Columbiana | 44 min |
| Aug 4, 2:36 PM EDT | Severe Thunderstorm Warning | CTP | Warren | 54 min |
| Aug 4, 2:42 PM EDT | Severe Thunderstorm Warning | PBZ | Butler | 33 min |
| Aug 4, 2:56 PM EDT | Severe Thunderstorm Warning | PBZ | Allegheny, Armstrong, Butler, Indiana, Westmoreland | 34 min |
| Aug 4, 2:58 PM EDT | Severe Thunderstorm Warning | CLE | Ashtabula | 77 min |
| Aug 4, 3:00 PM EDT | Severe Thunderstorm Warning | BUF | Jefferson, Lewis, Oswego | 45 min |
| Aug 4, 3:11 PM EDT | Severe Thunderstorm Warning | CLE | Ashtabula, Geauga, Mahoning, Portage, Trumbull | 64 min |
| Aug 4, 3:12 PM EDT | Severe Thunderstorm Warning | PBZ | Clarion, Forest, Venango | 33 min |
| Aug 4, 3:14 PM EDT | Severe Thunderstorm Warning | CTP | Lycoming, Northumberland, Sullivan, Union | 61 min |
| Aug 4, 3:15 PM EDT | Severe Thunderstorm Warning | PBZ | Venango | 30 min |
| Aug 4, 3:26 PM EDT | Severe Thunderstorm Warning | CTP | Warren | 79 min |
| Aug 4, 3:38 PM EDT | Severe Thunderstorm Warning | BUF | Jefferson | 57 min |
| Aug 4, 3:42 PM EDT | Severe Thunderstorm Warning | CTP | Columbia, Schuylkill | 82 min |
| Aug 4, 3:45 PM EDT | Severe Thunderstorm Warning | PBZ | Clarion, Forest, Jefferson | 45 min |
| Aug 4, 3:50 PM EDT | Severe Thunderstorm Warning | PBZ | Preston | 40 min |
| Aug 4, 3:58 PM EDT | Severe Thunderstorm Warning | CTP | Columbia, Lycoming, Sullivan | 47 min |
| Aug 4, 4:02 PM EDT | Severe Thunderstorm Warning | PBZ | Carroll, Tuscarawas | 28 min |
| Aug 4, 4:04 PM EDT | Severe Thunderstorm Warning | CTP | Somerset | 56 min |
| Aug 4, 4:12 PM EDT | Severe Thunderstorm Warning | CLE | Crawford, Erie | 34 min |
| Aug 4, 4:14 PM EDT | Severe Thunderstorm Warning | CTP | Blair, Cambria | 46 min |
| Aug 4, 4:25 PM EDT | Severe Thunderstorm Warning | PBZ | Carroll, Columbiana | 50 min |
| Aug 4, 4:27 PM EDT | Severe Thunderstorm Warning | BUF | Jefferson, Oswego | 33 min |
| Aug 4, 4:30 PM EDT | Severe Thunderstorm Warning | CTP | Centre, Huntingdon, Mifflin | 75 min |
| Aug 4, 4:42 PM EDT | Tornado Warning | CLE | Stark | 36 min |
| Aug 4, 4:42 PM EDT | Severe Thunderstorm Warning | CTP | Bedford, Blair, Cambria | 33 min |
| Aug 4, 4:47 PM EDT | Severe Thunderstorm Warning | BGM | Bradford, Susquehanna | 28 min |
| Aug 4, 4:47 PM EDT | Severe Thunderstorm Warning | CTP | Blair, Cambria, Centre, Clearfield | 43 min |
| Aug 4, 4:59 PM EDT | Severe Thunderstorm Warning | PBZ | Columbiana | 31 min |
| Aug 4, 5:00 PM EDT | Severe Thunderstorm Warning | BUF | Erie, Genesee, Niagara | 45 min |
| Aug 4, 5:01 PM EDT | Severe Thunderstorm Warning | BGM | Broome, Tioga | 29 min |
| Aug 4, 5:04 PM EDT | Severe Thunderstorm Warning | BUF | Cayuga, Oswego | 41 min |
| Aug 4, 5:15 PM EDT | Severe Thunderstorm Warning | CTP | Blair, Cambria | 37 min |
| Aug 4, 5:23 PM EDT | Severe Thunderstorm Warning | BUF | Allegany, Livingston | 67 min |
| Aug 4, 5:24 PM EDT | Severe Thunderstorm Warning | PBZ | Carroll, Columbiana, Jefferson | 22 min |
| Aug 4, 5:24 PM EDT | Severe Thunderstorm Warning | CTP | Cameron, Centre, Clearfield, Clinton | 51 min |
| Aug 4, 5:28 PM EDT | Severe Thunderstorm Warning | CTP | Bedford, Fulton | 62 min |
| Aug 4, 5:35 PM EDT | Severe Thunderstorm Warning | BGM | Chenango, Cortland | 25 min |
| Aug 4, 5:36 PM EDT | Tornado Warning | CTP | Fulton | 39 min |
| Aug 4, 5:51 PM EDT | Severe Thunderstorm Warning | BUF | Jefferson, Lewis, Oswego | 54 min |
| Aug 4, 5:56 PM EDT | Severe Thunderstorm Warning | PBZ | Beaver, Butler, Lawrence, Mercer, Venango | 49 min |
| Aug 4, 5:58 PM EDT | Severe Thunderstorm Warning | BGM | Chenango, Madison, Otsego | 32 min |
| Aug 4, 5:59 PM EDT | Severe Thunderstorm Warning | CTP | Clinton, Lycoming, Potter, Tioga | 61 min |
| Aug 4, 6:14 PM EDT | Severe Thunderstorm Warning | BGM | Steuben | 46 min |
| Aug 4, 6:18 PM EDT | Severe Thunderstorm Warning | CTP | Franklin, Fulton, Huntingdon | 57 min |
| Aug 4, 6:19 PM EDT | Severe Thunderstorm Warning | PBZ | Fayette, Greene | 26 min |
| Aug 4, 6:27 PM EDT | Severe Thunderstorm Warning | BGM | Schuyler, Steuben | 48 min |
| Aug 4, 6:38 PM EDT | Severe Thunderstorm Warning | BUF | Jefferson, Lewis | 52 min |
| Aug 4, 6:44 PM EDT | Severe Thunderstorm Warning | CTP | Lycoming, Tioga | 61 min |
| Aug 4, 6:46 PM EDT | Severe Thunderstorm Warning | PBZ | Armstrong, Butler, Clarion, Venango | 59 min |
| Aug 4, 6:50 PM EDT | Severe Thunderstorm Warning | CTP | Clinton, Lycoming | 40 min |
| Aug 4, 6:53 PM EDT | Severe Thunderstorm Warning | BGM | Chemung, Steuben | 37 min |
| Aug 4, 7:08 PM EDT | Severe Thunderstorm Warning | CTP | Cumberland, Juniata, Perry | 67 min |
| Aug 4, 7:09 PM EDT | Severe Thunderstorm Warning | BUF | Jefferson, Lewis, Oswego | 66 min |
| Aug 4, 7:15 PM EDT | Severe Thunderstorm Warning | BUF | Cayuga, Ontario, Oswego, Wayne | 60 min |
| Aug 4, 7:17 PM EDT | Severe Thunderstorm Warning | CTP | Franklin | 43 min |
| Aug 4, 7:22 PM EDT | Severe Thunderstorm Warning | BGM | Cayuga, Seneca, Yates | 23 min |
| Aug 4, 7:30 PM EDT | Severe Thunderstorm Warning | PBZ | Clarion, Forest, Jefferson | 45 min |
| Aug 4, 7:36 PM EDT | Severe Thunderstorm Warning | CTP | Lycoming | 54 min |
| Aug 4, 7:45 PM EDT | Severe Thunderstorm Warning | BGM | Cayuga, Onondaga, Seneca | 30 min |
| Aug 4, 7:51 PM EDT | Severe Thunderstorm Warning | BGM | Bradford | 54 min |
| Aug 4, 7:51 PM EDT | Severe Thunderstorm Warning | PBZ | Armstrong, Clarion, Jefferson | 54 min |
| Aug 4, 7:55 PM EDT | Severe Thunderstorm Warning | CTP | Cameron, Clearfield, Elk | 80 min |
| Aug 4, 8:12 PM EDT | Severe Thunderstorm Warning | CTP | Cumberland, Dauphin, Lebanon, Northumberland, Perry, Schuylkill and 3 more | 78 min |
| Aug 4, 8:16 PM EDT | Severe Thunderstorm Warning | CTP | Columbia, Lycoming, Montour, Northumberland, Sullivan, Union | 74 min |
| Aug 4, 8:36 PM EDT | Severe Thunderstorm Warning | CTP | Cumberland | 54 min |
| Aug 4, 8:55 PM EDT | Severe Thunderstorm Warning | CTP | Adams, Cumberland | 50 min |
| Aug 4, 8:57 PM EDT | Severe Thunderstorm Warning | CTP | Columbia | 33 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Buffalo Intl Airport, NY (KBUF), launched 12:00Z, 5.4 hours before the alert went out and 103 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 243 J/kg
- Mixed-layer CIN
- -61 J/kg
- Mixed-layer LCL
- 895 m above ground
- 0-6 km bulk shear
- 35 kt
- 0-1 km storm-relative helicity
- 179 m²/s²
- 0-3 km storm-relative helicity
- 190 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 1.0
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 4, 11:38 AM EDT | Mesoscale Discussion | SPC | Cattaraugus, Chautauqua, Erie | 2 hr |
| Aug 4, 3:46 PM EDT | Mesoscale Discussion | SPC | Allegany, Broome, Cattaraugus, Cayuga, Chautauqua, Chemung and 27 more | 119 min |
| Aug 4, 5:53 PM EDT | Mesoscale Discussion | SPC | Clinton, Essex, Franklin, Warren | 3 hr |
| Aug 4, 7:41 PM EDT | Mesoscale Discussion | SPC | Allegany, Broome, Cattaraugus, Cayuga, Chemung, Chenango and 18 more | 2 hr |
Nearby
Severe Thunderstorm Watches in Pennsylvania, 2017Severe Thunderstorm Watches in New York, 2017Severe Thunderstorm Watches in Ohio, 2017Every severe thunderstorm watch in 2017
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.