Alert archive / Virginia / Mesoscale Discussions in 2011

Mesoscale Discussion 1977

August 14, 2011Allegany County, Frederick County, Washington County, Maryland; 35 counties in Virginia; 10 counties in West Virginia

The Storm Prediction Center issued this mesoscale discussion at Aug 14, 2011, 3:47 PM EDT for Allegany County, Frederick County, Washington County, Maryland; 35 counties in Virginia; 10 counties in West Virginia. It was in force for 58 min.

The area

The outline as issued.

The facts

Issued: Aug 14, 2011, 3:47 PM EDT (19:47 UTC)
Expired: Aug 14, 2011, 4:45 PM EDT
In force: 58 min
Issued by: the Storm Prediction Center

All 48 counties

Allegany County, MD, Frederick County, MD, Washington County, MD, Albemarle County, VA, Alleghany County, VA, Amherst County, VA, Augusta County, VA, Bath County, VA, Buckingham County, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Covington, VA, City of Harrisonburg, VA, City of Lexington, VA, City of Manassas, VA, City of Manassas Park, VA, City of Staunton, VA, City of Waynesboro, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Fauquier County, VA, Fluvanna County, VA, Frederick County, VA, Greene County, VA, Highland County, VA, Loudoun County, VA, Louisa County, VA, Madison County, VA, Nelson County, VA, Orange County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Rockbridge County, VA, Rockingham County, VA, Shenandoah County, VA, Warren County, VA, Berkeley County, WV, Grant County, WV, Greenbrier County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Mineral County, WV, Morgan County, WV, Pendleton County, WV, Pocahontas County, WV

The radar

The Sterling radar (KLWX), 129 km from the middle of the area, began a volume at 19:48 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 nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 7.8 hours before the alert went out and 135 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: 618 J/kg
Mixed-layer CIN: -2 J/kg
Mixed-layer LCL: 493 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 71 m²/s²
0-3 km storm-relative helicity: 156 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 2.5

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 14, 6:37 PM EDT	Mesoscale Discussion	SPC	Charles	53 min
Aug 14, 1:50 PM EDT	Mesoscale Discussion	SPC	Albemarle, Alleghany, Amelia, Amherst, Appomattox, Augusta and 61 more	55 min
Aug 14, 2:07 PM EDT	Severe Thunderstorm Watch	SPC	Alleghany, Amherst, Appomattox, Bath, Bedford, Bland and 35 more	7 hr

Nearby

Mesoscale Discussions in Virginia, 2011 Mesoscale Discussions in West Virginia, 2011 Mesoscale Discussions in Maryland, 2011 Every mesoscale discussion in 2011

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.