Alert archive / Virginia / Severe Thunderstorm Watches in 2011

Severe Thunderstorm Watch 355

May 24, 20117 counties in Maryland; 26 counties in North Carolina; 72 counties in Virginia

The Storm Prediction Center issued this severe thunderstorm watch at May 24, 2011, 12:42 PM EDT for 7 counties in Maryland; 26 counties in North Carolina; 72 counties in Virginia. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued: May 24, 2011, 12:42 PM EDT (16:42 UTC)
Expired: May 24, 2011, 5:27 PM EDT
In force: 5 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1.5 in
Strongest gust expected: 60 kt

All 105 counties

Calvert County, MD, Charles County, MD, Dorchester County, MD, Saint Mary's County, MD, Somerset County, MD, Wicomico County, MD, Worcester County, MD, Alamance County, NC, Bertie County, NC, Camden County, NC, Chowan County, NC, Currituck County, NC, Durham County, NC, Edgecombe County, NC, Forsyth County, NC, Franklin County, NC, Gates County, NC, Granville County, NC, Guilford County, NC, Halifax County, NC, Hertford County, NC, Johnston County, NC, Nash County, NC, Northampton County, NC, Orange County, NC, Pasquotank County, NC, Perquimans County, NC, Person County, NC, Vance County, NC, Wake County, NC, Warren County, NC, Wayne County, NC, Wilson County, NC, Accomack County, VA, Albemarle County, VA, Amelia County, VA, Augusta County, VA, Brunswick County, VA, Caroline County, VA, Charles City County, VA, Chesterfield County, VA, City of Charlottesville, VA, City of Chesapeake, VA, City of Colonial Heights, VA, City of Emporia, VA, City of Franklin, VA, City of Fredericksburg, VA, City of Hampton, VA, City of Harrisonburg, VA, City of Hopewell, VA, City of Newport News, VA, City of Norfolk, VA, City of Petersburg, VA, City of Poquoson, VA, City of Portsmouth, VA, City of Richmond, VA, City of Staunton, VA, City of Suffolk, VA, City of Virginia Beach, VA, City of Waynesboro, VA, City of Williamsburg, VA, Culpeper County, VA, Cumberland County, VA, Dinwiddie County, VA, Essex County, VA, Fluvanna County, VA, Gloucester County, VA, Goochland County, VA, Greene County, VA, Greensville County, VA, Hanover County, VA, Henrico County, VA, Highland County, VA, Isle of Wight County, VA, James City County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Lancaster County, VA, Louisa County, VA, Lunenburg County, VA, Madison County, VA, Mathews County, VA, Mecklenburg County, VA, Middlesex County, VA, Nelson County, VA, New Kent County, VA, Northampton County, VA, Northumberland County, VA, Nottoway County, VA, Orange County, VA, Page County, VA, Powhatan County, VA, Prince Edward County, VA, Prince George County, VA, Rappahannock County, VA, Richmond County, VA, Rockingham County, VA, Southampton County, VA, Spotsylvania County, VA, Stafford County, VA, Surry County, VA, Sussex County, VA, Westmoreland County, VA, York County, VA

The radar

The Norfolk radar (KAKQ), 82 km from the middle of the area, began a volume at 16:45 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: 70%
One or more gusts of 65 knots or more: 40%
Ten or more severe hail reports: 30%
One or more hailstones of 2 inches or more: 20%
Six or more combined severe hail and wind reports: 80%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
May 24, 1:39 PM EDT	Severe Thunderstorm Warning	RAH	Granville, Person	34 min
May 24, 3:23 PM EDT	Severe Thunderstorm Warning	AKQ	Gates, Hertford, Northampton	52 min
May 24, 3:51 PM EDT	Severe Thunderstorm Warning	AKQ	Isle of Wight, Surry, City of Chesapeake, City of Hampton, City of Newport News, City of Norfolk and 3 more	54 min
May 24, 4:36 PM EDT	Severe Thunderstorm Warning	RAH	Forsyth	39 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

Roanoke, VA (KRNK), launched 12:00Z, 4.7 hours before the alert went out and 152 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: 354 J/kg
Mixed-layer CIN: -64 J/kg
Mixed-layer LCL: 922 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 148 m²/s²
0-3 km storm-relative helicity: 210 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.9

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 24, 8:34 AM EDT	Mesoscale Discussion	SPC	Alamance, Alexander, Alleghany, Ashe, Avery, Caldwell and 13 more	116 min
May 24, 10:00 AM EDT	Severe Thunderstorm Watch	SPC	Alleghany, Ashe, Caswell, Rockingham, Stokes, Surry and 3 more	7 hr
May 24, 12:15 PM EDT	Mesoscale Discussion	SPC	Alamance, Bertie, Camden, Caswell, Chowan, Durham and 24 more	90 min
May 24, 3:33 PM EDT	Mesoscale Discussion	SPC	Alamance, Alexander, Alleghany, Ashe, Avery, Bertie and 30 more	87 min
May 24, 4:43 PM EDT	Tornado Watch	SPC	Alamance, Alleghany, Ashe, Caswell, Forsyth, Guilford and 8 more	5 hr
May 24, 7:33 PM EDT	Mesoscale Discussion	SPC	Alamance, Alleghany, Ashe, Caswell, Durham, Forsyth and 11 more	57 min
May 24, 7:01 AM EDT	Severe Thunderstorm Watch	SPC	Lee, Russell, Scott, Washington, Wise, City of Bristol and 1 more	8 hr
May 24, 12:55 PM EDT	Mesoscale Discussion	SPC	Lee, Scott, Wise, City of Norton	65 min
May 24, 1:57 PM EDT	Severe Thunderstorm Watch	SPC	Buchanan, Dickenson, Lee, Russell, Scott, Washington and 3 more	6 hr
May 24, 4:27 PM EDT	Mesoscale Discussion	SPC	Buchanan, Dickenson, Lee, Russell, Scott, Tazewell and 4 more	63 min
May 24, 7:46 PM EDT	Mesoscale Discussion	SPC	Lee, Russell, Scott, Washington, Wise, City of Bristol and 1 more	59 min

Nearby

Severe Thunderstorm Watches in Virginia, 2011 Severe Thunderstorm Watches in North Carolina, 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.