Alert archive / Pennsylvania / Severe Thunderstorm Watches in 2020
Severe Thunderstorm Watch 459
The Storm Prediction Center issued this severe thunderstorm watch at Aug 27, 2020, 5:32 PM EDT for 34 counties in Pennsylvania. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 27, 2020, 5:32 PM EDT (21:32 UTC)
- Expired
- Aug 27, 2020, 9:30 PM EDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 60 kt
All 34 counties
Adams County, PA, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Bedford County, PA, Blair County, PA, Butler County, PA, Cambria County, PA, Centre County, PA, Clearfield County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Fayette 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, Lebanon County, PA, Mifflin County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Schuylkill County, PA, Snyder County, PA, Somerset County, PA, Union County, PA, Washington County, PA, Westmoreland County, PA, York County, PA
The radar
The State College radar (KCCX), 86 km from the middle of the area, began a volume at 21:35 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
- 20%
- One or more EF2 to EF5 tornadoes
- 5%
- Ten or more severe wind reports
- 50%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 20%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
18 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 27, 5:33 PM EDT | Severe Thunderstorm Warning | PBZ | Beaver, Lawrence | 42 min |
| Aug 27, 5:40 PM EDT | Severe Thunderstorm Warning | PBZ | Armstrong, Indiana, Jefferson | 50 min |
| Aug 27, 6:08 PM EDT | Severe Thunderstorm Warning | PBZ | Allegheny, Beaver, Washington | 52 min |
| Aug 27, 6:09 PM EDT | Severe Thunderstorm Warning | CTP | Cameron, Clearfield, Clinton | 32 min |
| Aug 27, 6:11 PM EDT | Severe Thunderstorm Warning | PBZ | Beaver, Washington | 49 min |
| Aug 27, 6:15 PM EDT | Severe Thunderstorm Warning | CTP | Blair, Cambria, Centre, Huntingdon | 75 min |
| Aug 27, 6:38 PM EDT | Severe Thunderstorm Warning | CTP | Centre, Clinton, Union | 43 min |
| Aug 27, 6:41 PM EDT | Severe Thunderstorm Warning | PBZ | Allegheny, Fayette, Washington, Westmoreland | 64 min |
| Aug 27, 6:47 PM EDT | Severe Thunderstorm Warning | CTP | Somerset | 58 min |
| Aug 27, 6:52 PM EDT | Severe Thunderstorm Warning | CTP | Snyder | 39 min |
| Aug 27, 7:09 PM EDT | Severe Thunderstorm Warning | CTP | Bedford, Somerset | 66 min |
| Aug 27, 7:10 PM EDT | Severe Thunderstorm Warning | PBZ | Washington | 50 min |
| Aug 27, 7:12 PM EDT | Severe Thunderstorm Warning | CTP | Montour, Northumberland | 34 min |
| Aug 27, 7:29 PM EDT | Severe Thunderstorm Warning | CTP | Franklin, Fulton, Huntingdon | 44 min |
| Aug 27, 7:29 PM EDT | Severe Thunderstorm Warning | CTP | Columbia, Schuylkill | 47 min |
| Aug 27, 7:40 PM EDT | Severe Thunderstorm Warning | PBZ | Fayette, Greene, Washington, Westmoreland | 65 min |
| Aug 27, 8:05 PM EDT | Severe Thunderstorm Warning | CTP | Somerset | 70 min |
| Aug 27, 8:42 PM EDT | Severe Thunderstorm Warning | PBZ | Fayette, Greene | 48 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
Pittsburgh, PA (KPIT), launched 12:00Z, 9.5 hours before the alert went out and 101 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
- 277 J/kg
- Mixed-layer CIN
- -54 J/kg
- Mixed-layer LCL
- 931 m above ground
- 0-6 km bulk shear
- 32 kt
- 0-1 km storm-relative helicity
- 127 m²/s²
- 0-3 km storm-relative helicity
- 127 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 2.8
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 27, 12:38 PM EDT | Mesoscale Discussion | SPC | Susquehanna, Wayne | 3 hr |
| Aug 27, 1:22 PM EDT | Tornado Watch | SPC | Pike, Susquehanna, Wayne | 7 hr |
| Aug 27, 2:14 PM EDT | Mesoscale Discussion | SPC | Adams, Bedford, Blair, Cambria, Cumberland, Fayette and 6 more | 2 hr |
| Aug 27, 2:49 PM EDT | Severe Thunderstorm Watch | SPC | Bradford, Cameron, Clinton, Elk, Lackawanna, Luzerne and 7 more | 5 hr |
| Aug 27, 4:34 PM EDT | Mesoscale Discussion | SPC | Allegheny, Armstrong, Beaver, Blair, Butler, Cambria and 9 more | 86 min |
| Aug 27, 6:35 PM EDT | Mesoscale Discussion | SPC | Adams, Bedford, Berks, Blair, Bucks, Chester and 24 more | 115 min |
Nearby
Severe Thunderstorm Watches in Pennsylvania, 2020Every severe thunderstorm watch in 2020
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.