Alert archive / Virginia / Mesoscale Discussions in 2011

Mesoscale Discussion 805

May 18, 20115 states

The Storm Prediction Center issued this mesoscale discussion at May 18, 2011, 6:01 PM EDT for 5 states. It was in force for 89 min.

The area

The outline as issued.

The facts

Issued: May 18, 2011, 6:01 PM EDT (22:01 UTC)
Expired: May 18, 2011, 7:30 PM EDT
In force: 89 min
Issued by: the Storm Prediction Center

All 98 counties

Kent County, DE, Allegany County, MD, Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Caroline County, MD, Carroll County, MD, Charles County, MD, City of Baltimore, MD, Dorchester County, MD, Frederick County, MD, Garrett County, MD, Howard County, MD, Kent County, MD, Montgomery County, MD, Prince George's County, MD, Queen Anne's County, MD, Saint Mary's County, MD, Somerset County, MD, Talbot County, MD, Washington County, MD, Wicomico County, MD, Adams County, PA, Allegheny County, PA, Beaver County, PA, Bedford County, PA, Butler County, PA, Fayette County, PA, Franklin County, PA, Fulton County, PA, Greene County, PA, Lawrence County, PA, Somerset County, PA, Washington County, PA, Westmoreland County, PA, Accomack County, VA, Arlington County, VA, Caroline County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Harrisonburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, Greene County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Lancaster County, VA, Loudoun County, VA, Madison County, VA, Mathews County, VA, Middlesex County, VA, Northampton County, VA, Northumberland County, VA, Orange County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Richmond County, VA, Rockingham County, VA, Shenandoah County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Westmoreland County, VA, Barbour County, WV, Berkeley County, WV, Brooke County, WV, Doddridge County, WV, Grant County, WV, Hampshire County, WV, Hancock County, WV, Hardy County, WV, Harrison County, WV, Jefferson County, WV, Lewis County, WV, Marion County, WV, Marshall County, WV, Mineral County, WV, Monongalia County, WV, Morgan County, WV, Ohio County, WV, Pendleton County, WV, Preston County, WV, Randolph County, WV, Taylor County, WV, Tucker County, WV, Upshur County, WV, Wetzel County, WV

The radar

The Sterling radar (KLWX), 115 km from the middle of the area, began a volume at 22:02 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, 10.0 hours before the alert went out and 123 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: 256 J/kg
Mixed-layer CIN: -3 J/kg
Mixed-layer LCL: 585 m above ground
0-6 km bulk shear: 51 kt
0-1 km storm-relative helicity: 83 m²/s²
0-3 km storm-relative helicity: 106 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 1.1

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
May 18, 12:55 PM EDT	Severe Thunderstorm Watch	SPC	Kent, New Castle, Sussex	8 hr
May 18, 3:08 PM EDT	Mesoscale Discussion	SPC	Kent, New Castle, Sussex	67 min
May 18, 11:55 AM EDT	Mesoscale Discussion	SPC	Allegany, Anne Arundel, Calvert, Carroll, Charles, Frederick and 6 more	65 min
May 18, 2:34 PM EDT	Mesoscale Discussion	SPC	Berks, Bucks, Carbon, Columbia, Lackawanna, Lebanon and 12 more	56 min

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.