Alert archive / West Virginia / Mesoscale Discussions in 2018

Mesoscale Discussion 1334

August 21, 20184 states

The Storm Prediction Center issued this mesoscale discussion at Aug 21, 2018, 2:16 PM EDT for 4 states. It was in force for 119 min.

The area

The outline as issued.

The facts

Issued: Aug 21, 2018, 2:16 PM EDT (18:16 UTC)
Expired: Aug 21, 2018, 4:15 PM EDT
In force: 119 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 42 counties

Allegany County, MD, Garrett County, MD, Allegheny County, PA, Armstrong County, PA, Bedford County, PA, Blair County, PA, Cambria County, PA, Clarion County, PA, Clearfield County, PA, Fayette County, PA, Greene County, PA, Indiana County, PA, Jefferson County, PA, Somerset County, PA, Westmoreland County, PA, Highland County, VA, Barbour County, WV, Braxton County, WV, Clay County, WV, Doddridge County, WV, Fayette County, WV, Gilmer County, WV, Grant County, WV, Greenbrier County, WV, Hampshire County, WV, Hardy County, WV, Harrison County, WV, Lewis County, WV, Marion County, WV, Mineral County, WV, Monongalia County, WV, Nicholas County, WV, Pendleton County, WV, Pocahontas County, WV, Preston County, WV, Raleigh County, WV, Randolph County, WV, Summers County, WV, Taylor County, WV, Tucker County, WV, Upshur County, WV, Webster County, WV

The radar

The Pittsburgh radar (KPBZ), 118 km from the middle of the area, began a volume at 18:16 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.

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 346Aug 21, 2:40 PM EDT

The nearest sounding before it

Pittsburgh, PA (KAGC), launched 12:00Z, 6.3 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.

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: 340 J/kg
Mixed-layer CIN: -43 J/kg
Mixed-layer LCL: 811 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: 211 m²/s²
0-3 km storm-relative helicity: 223 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 2.5

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 21, 2:41 PM EDT	Severe Thunderstorm Watch	SPC	Allegany, Carroll, Frederick, Garrett, Washington	7 hr
Aug 21, 4:56 PM EDT	Mesoscale Discussion	SPC	Allegany, Carroll, Frederick, Garrett, Montgomery, Washington	2 hr
Aug 21, 5:03 PM EDT	Mesoscale Discussion	SPC	Charles, Saint Mary's	117 min
Aug 21, 7:06 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Baltimore, Carroll, Cecil, Frederick, Harford and 7 more	84 min
Aug 21, 12:45 PM EDT	Mesoscale Discussion	SPC	Fayette, Greene, Washington, Westmoreland	3 hr

Nearby

Mesoscale Discussions in West Virginia, 2018 Mesoscale Discussions in Pennsylvania, 2018 Mesoscale Discussions in Maryland, 2018 Every mesoscale discussion in 2018

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.