Alert archive / Virginia / Severe Thunderstorm Watches in 2011

Severe Thunderstorm Watch 305

May 18, 20115 states

The Storm Prediction Center issued this severe thunderstorm watch at May 18, 2011, 12:55 PM EDT for 5 states. It was in force for 8 hr.

The area

The outline as issued.

The facts

Issued: May 18, 2011, 12:55 PM EDT (16:55 UTC)
Expired: May 18, 2011, 8:46 PM EDT
In force: 8 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1.5 in
Strongest gust expected: 60 kt

All 124 counties

Kent County, DE, New Castle County, DE, Sussex County, DE, Allegany County, MD, Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Caroline County, MD, Carroll County, MD, Cecil County, MD, Charles County, MD, City of Baltimore, MD, Dorchester County, MD, Frederick County, MD, Garrett County, MD, Harford 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, Worcester County, MD, Adams County, PA, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Bedford County, PA, Blair County, PA, Butler County, PA, Cambria County, PA, Cumberland County, PA, Fayette County, PA, Franklin County, PA, Fulton County, PA, Greene County, PA, Huntingdon County, PA, Indiana County, PA, Lawrence County, PA, Somerset County, PA, Washington County, PA, Westmoreland County, PA, York County, PA, Accomack County, VA, Albemarle County, VA, Arlington County, VA, Augusta County, VA, Caroline County, VA, City of Alexandria, VA, City of Charlottesville, 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 Staunton, VA, City of Waynesboro, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Fluvanna County, VA, Frederick County, VA, Gloucester County, VA, Greene County, VA, Hanover County, VA, Highland County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Lancaster County, VA, Loudoun County, VA, Louisa County, VA, Madison County, VA, Mathews County, VA, Middlesex County, VA, Nelson County, VA, New Kent 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, Pocahontas County, WV, Preston County, WV, Randolph County, WV, Taylor County, WV, Tucker County, WV, Tyler 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 16:55 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: 30%
One or more gusts of 65 knots or more: 30%
Ten or more severe hail reports: 60%
One or more hailstones of 2 inches or more: 20%
Six or more combined severe hail and wind reports: 80%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
May 18, 1:28 PM EDT	Severe Thunderstorm Warning	RLX	Barbour, Harrison, Randolph, Taylor	41 min
May 18, 1:37 PM EDT	Severe Thunderstorm Warning	PBZ	Greene	53 min
May 18, 1:39 PM EDT	Severe Thunderstorm Warning	RLX	Lewis, Randolph, Upshur, Webster	27 min
May 18, 1:52 PM EDT	Severe Thunderstorm Warning	LWX	Grant, Mineral	21 min
May 18, 1:53 PM EDT	Severe Thunderstorm Warning	LWX	Pendleton	52 min
May 18, 2:08 PM EDT	Flash Flood Warning	LWX	Fauquier, Loudoun, Prince William, City of Manassas, City of Manassas Park	4 hr
May 18, 2:27 PM EDT	Tornado Warning	LWX	Baltimore, Harford	33 min
May 18, 2:27 PM EDT	Severe Thunderstorm Warning	PBZ	Greene, Washington	48 min
May 18, 2:32 PM EDT	Severe Thunderstorm Warning	PBZ	Brooke, Hancock	43 min
May 18, 2:36 PM EDT	Severe Thunderstorm Warning	LWX	Allegany	39 min
May 18, 2:39 PM EDT	Tornado Warning	PHI	Queen Anne's, Talbot	51 min
May 18, 2:45 PM EDT	Flash Flood Warning	LWX	Baltimore, Harford	3 hr
May 18, 2:53 PM EDT	Severe Thunderstorm Warning	PBZ	Washington	52 min
May 18, 2:57 PM EDT	Tornado Warning	LWX	Baltimore, Harford	33 min
May 18, 2:58 PM EDT	Flash Flood Warning	PBZ	Greene	62 min
May 18, 3:11 PM EDT	Severe Thunderstorm Warning	CTP	York	49 min
May 18, 3:12 PM EDT	Severe Thunderstorm Warning	LWX	Frederick, Washington	33 min
May 18, 3:22 PM EDT	Severe Thunderstorm Warning	PHI	Kent, Queen Anne's, Talbot	47 min
May 18, 3:40 PM EDT	Flash Flood Warning	LWX	Fairfax, Loudoun	2 hr
May 18, 3:44 PM EDT	Severe Thunderstorm Warning	LWX	Frederick, Washington	19 min
May 18, 3:50 PM EDT	Severe Thunderstorm Warning	LWX	Loudoun	40 min
May 18, 3:58 PM EDT	Severe Thunderstorm Warning	LWX	Allegany	47 min
May 18, 4:03 PM EDT	Flash Flood Warning	LWX	Allegany	3 hr
May 18, 4:09 PM EDT	Severe Thunderstorm Warning	AKQ	Gloucester, Mathews, Middlesex, York, City of Hampton, City of Newport News and 1 more	51 min
May 18, 4:10 PM EDT	Tornado Warning	LWX	Baltimore, Harford	35 min
May 18, 4:11 PM EDT	Flash Flood Warning	CTP	Somerset	3 hr
May 18, 4:14 PM EDT	Severe Thunderstorm Warning	LWX	Allegany	46 min
May 18, 4:31 PM EDT	Flash Flood Warning	CTP	Adams, Cumberland, Dauphin, Lancaster, Perry, York	4 hr
May 18, 4:33 PM EDT	Severe Thunderstorm Warning	AKQ	Charles City, Hanover, James City, King and Queen, King William, New Kent	42 min
May 18, 5:11 PM EDT	Severe Thunderstorm Warning	CTP	Franklin	64 min
May 18, 5:15 PM EDT	Severe Thunderstorm Warning	LWX	Charles	45 min
May 18, 5:16 PM EDT	Severe Thunderstorm Warning	AKQ	Caroline, Essex, Hanover, King and Queen, King William, New Kent	59 min
May 18, 5:36 PM EDT	Severe Thunderstorm Warning	LWX	Culpeper, Fauquier, Rappahannock, Warren	26 min
May 18, 5:56 PM EDT	Severe Thunderstorm Warning	LWX	Charles	49 min
May 18, 6:44 PM EDT	Severe Thunderstorm Warning	LWX	Fauquier, King George, Prince William, Spotsylvania, Stafford, City of Fredericksburg	46 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

Washington/Dulle, VA (KIAD), launched 12:00Z, 4.9 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

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 18, 3:08 PM EDT	Mesoscale Discussion	SPC	Kent, New Castle, Sussex	67 min
May 18, 6:01 PM EDT	Mesoscale Discussion	SPC	Kent	89 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

Severe Thunderstorm Watches in Virginia, 2011 Severe Thunderstorm Watches in West Virginia, 2011 Severe Thunderstorm Watches in Maryland, 2011 Every severe thunderstorm watch 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.