Alert archive / Pennsylvania / Severe Thunderstorm Watches in 2017

Severe Thunderstorm Watch 457

August 19, 201711 counties in Ohio; 42 counties in Pennsylvania; 4 counties in West Virginia

The Storm Prediction Center issued this severe thunderstorm watch at Aug 19, 2017, 2:45 PM EDT for 11 counties in Ohio; 42 counties in Pennsylvania; 4 counties in West Virginia. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Aug 19, 2017, 2:45 PM EDT (18:45 UTC)
Expired: Aug 19, 2017, 9:00 PM EDT
In force: 6 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1.5 in
Strongest gust expected: 55 kt

All 57 counties

Belmont County, OH, Carroll County, OH, Columbiana County, OH, Coshocton County, OH, Guernsey County, OH, Harrison County, OH, Jefferson County, OH, Monroe County, OH, Muskingum County, OH, Noble County, OH, Tuscarawas County, OH, Adams County, PA, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Bedford County, PA, Blair 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, Cumberland County, PA, Dauphin County, PA, Elk 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, Lawrence County, PA, Lebanon County, PA, Lycoming County, PA, Mercer County, PA, Mifflin County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Snyder County, PA, Somerset County, PA, Sullivan County, PA, Union County, PA, Venango County, PA, Washington County, PA, Westmoreland County, PA, York County, PA, Brooke County, WV, Hancock County, WV, Marshall County, WV, Ohio County, WV

The radar

The Pittsburgh radar (KPBZ), 6 km from the middle of the area, began a volume at 18:46 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: 5%
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: 40%
One or more hailstones of 2 inches or more: 10%
Six or more combined severe hail and wind reports: 70%

Warnings issued inside it

30 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Aug 19, 3:10 PM EDT	Severe Thunderstorm Warning	PBZ	Carroll, Columbiana, Jefferson, Tuscarawas	50 min
Aug 19, 3:10 PM EDT	Severe Thunderstorm Warning	PBZ	Beaver, Butler, Lawrence	50 min
Aug 19, 3:14 PM EDT	Severe Thunderstorm Warning	PBZ	Beaver, Butler, Lawrence	46 min
Aug 19, 3:16 PM EDT	Severe Thunderstorm Warning	PBZ	Columbiana	44 min
Aug 19, 3:23 PM EDT	Severe Thunderstorm Warning	PBZ	Guernsey, Muskingum	52 min
Aug 19, 3:47 PM EDT	Severe Thunderstorm Warning	PBZ	Armstrong, Butler	28 min
Aug 19, 3:54 PM EDT	Severe Thunderstorm Warning	PBZ	Allegheny, Butler, Westmoreland	51 min
Aug 19, 3:57 PM EDT	Severe Thunderstorm Warning	PBZ	Harrison, Jefferson	48 min
Aug 19, 4:08 PM EDT	Severe Thunderstorm Warning	PBZ	Carroll, Columbiana	39 min
Aug 19, 4:19 PM EDT	Severe Thunderstorm Warning	PBZ	Allegheny, Washington	41 min
Aug 19, 4:32 PM EDT	Severe Thunderstorm Warning	PBZ	Allegheny, Westmoreland	43 min
Aug 19, 4:36 PM EDT	Severe Thunderstorm Warning	PBZ	Armstrong, Indiana	39 min
Aug 19, 4:43 PM EDT	Severe Thunderstorm Warning	PBZ	Indiana, Jefferson	32 min
Aug 19, 4:46 PM EDT	Severe Thunderstorm Warning	PBZ	Indiana, Westmoreland	44 min
Aug 19, 5:04 PM EDT	Severe Thunderstorm Warning	PBZ	Indiana, Westmoreland	28 min
Aug 19, 5:06 PM EDT	Severe Thunderstorm Warning	CTP	Cambria, Clearfield	69 min
Aug 19, 5:07 PM EDT	Severe Thunderstorm Warning	PBZ	Allegheny, Fayette, Westmoreland	53 min
Aug 19, 5:16 PM EDT	Severe Thunderstorm Warning	PBZ	Fayette, Washington, Westmoreland	44 min
Aug 19, 5:29 PM EDT	Severe Thunderstorm Warning	CTP	Blair, Centre, Huntingdon	91 min
Aug 19, 5:30 PM EDT	Severe Thunderstorm Warning	PBZ	Monroe, Noble	45 min
Aug 19, 5:34 PM EDT	Severe Thunderstorm Warning	PBZ	Indiana, Westmoreland	24 min
Aug 19, 5:39 PM EDT	Severe Thunderstorm Warning	CTP	Somerset	81 min
Aug 19, 6:02 PM EDT	Severe Thunderstorm Warning	CTP	Juniata, Mifflin	88 min
Aug 19, 6:18 PM EDT	Severe Thunderstorm Warning	CTP	Bedford	60 min
Aug 19, 6:38 PM EDT	Severe Thunderstorm Warning	CTP	Cumberland, Franklin, Perry	82 min
Aug 19, 6:46 PM EDT	Severe Thunderstorm Warning	CTP	Snyder, Union	74 min
Aug 19, 7:14 PM EDT	Severe Thunderstorm Warning	CTP	Dauphin, Northumberland	63 min
Aug 19, 7:48 PM EDT	Severe Thunderstorm Warning	CTP	Lebanon, Schuylkill	57 min
Aug 19, 7:54 PM EDT	Severe Thunderstorm Warning	CTP	Columbia, Montour, Schuylkill	51 min
Aug 19, 8:07 PM EDT	Severe Thunderstorm Warning	CTP	Lancaster, York	57 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 (KAGC), launched 12:00Z, 6.8 hours before the alert went out and 13 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 4 J/kg
Mixed-layer CIN: -100 J/kg
Mixed-layer LCL: 898 m above ground
0-6 km bulk shear: 46 kt
0-1 km storm-relative helicity: 14 m²/s²
0-3 km storm-relative helicity: 28 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 19, 2:13 PM EDT	Mesoscale Discussion	SPC	Athens, Belmont, Carroll, Columbiana, Coshocton, Fairfield and 19 more	3 hr
Aug 19, 4:43 PM EDT	Mesoscale Discussion	SPC	Belmont, Carroll, Columbiana, Coshocton, Guernsey, Harrison and 5 more	2 hr

Nearby

Severe Thunderstorm Watches in Pennsylvania, 2017 Severe Thunderstorm Watches in Ohio, 2017 Severe Thunderstorm Watches in West Virginia, 2017 Every 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.