Alert archive / Virginia / Severe Thunderstorm Watches in 2011
Severe Thunderstorm Watch 807
The Storm Prediction Center issued this severe thunderstorm watch at Aug 25, 2011, 3:23 PM EDT for 9 counties in Maryland; 67 counties in Virginia. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 25, 2011, 3:23 PM EDT (19:23 UTC)
- Expired
- Aug 25, 2011, 8:04 PM EDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
All 76 counties
Anne Arundel County, MD, Calvert County, MD, Charles County, MD, Dorchester County, MD, Prince George's County, MD, Saint Mary's County, MD, Somerset County, MD, Wicomico County, MD, Worcester County, MD, Accomack County, VA, Albemarle County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Arlington County, VA, Bedford County, VA, Brunswick County, VA, Buckingham County, VA, Campbell County, VA, Caroline County, VA, Charles City County, VA, Chesterfield County, VA, City of Alexandria, VA, City of Charlottesville, VA, City of Colonial Heights, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Hopewell, VA, City of Lynchburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Petersburg, VA, City of Richmond, VA, City of Williamsburg, VA, Culpeper County, VA, Cumberland County, VA, Dinwiddie County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Fluvanna County, VA, Franklin County, VA, Gloucester County, VA, Goochland County, VA, Greene County, VA, Greensville County, VA, Hanover County, VA, Henrico 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, Northumberland County, VA, Nottoway County, VA, Orange County, VA, Powhatan County, VA, Prince Edward County, VA, Prince George County, VA, Prince William County, VA, Richmond 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), 141 km from the middle of the area, began a volume at 19:24 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
- 10%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 10%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
14 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 25, 4:05 PM EDT | Severe Thunderstorm Warning | LWX | Culpeper, Fauquier, King George, Orange, Spotsylvania, Stafford and 1 more | 40 min |
| Aug 25, 4:23 PM EDT | Severe Thunderstorm Warning | RNK | Bedford, Campbell, Pittsylvania | 67 min |
| Aug 25, 4:42 PM EDT | Severe Thunderstorm Warning | LWX | Charles | 48 min |
| Aug 25, 4:51 PM EDT | Severe Thunderstorm Warning | RNK | Bedford, Franklin, Pittsylvania | 39 min |
| Aug 25, 5:00 PM EDT | Severe Thunderstorm Warning | RNK | Appomattox, Buckingham | 30 min |
| Aug 25, 5:07 PM EDT | Severe Thunderstorm Warning | AKQ | Caroline, Essex | 38 min |
| Aug 25, 5:17 PM EDT | Severe Thunderstorm Warning | AKQ | Amelia, Cumberland, Nottoway, Powhatan, Prince Edward | 43 min |
| Aug 25, 5:20 PM EDT | Severe Thunderstorm Warning | LWX | Charles, Saint Mary's | 40 min |
| Aug 25, 5:47 PM EDT | Flash Flood Warning | LWX | Calvert, Charles, Saint Mary's | 97 min |
| Aug 25, 5:54 PM EDT | Severe Thunderstorm Warning | AKQ | Caroline, Essex, King and Queen, King William, Lancaster, Northumberland and 2 more | 51 min |
| Aug 25, 5:54 PM EDT | Severe Thunderstorm Warning | AKQ | Amelia, Chesterfield, Dinwiddie, Goochland, Hanover, Henrico and 5 more | 51 min |
| Aug 25, 5:59 PM EDT | Tornado Warning | LWX | Calvert, Saint Mary's | 31 min |
| Aug 25, 6:36 PM EDT | Severe Thunderstorm Warning | AKQ | Charles City, Chesterfield, Dinwiddie, Henrico, James City, New Kent and 7 more | 24 min |
| Aug 25, 6:44 PM EDT | Severe Thunderstorm Warning | RNK | Bedford, Campbell, Pittsylvania | 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
Roanoke, VA (KRNK), launched 12:00Z, 7.4 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.
- Mixed-layer CAPE
- 459 J/kg
- Mixed-layer CIN
- -147 J/kg
- Mixed-layer LCL
- 1055 m above ground
- 0-6 km bulk shear
- 22 kt
- 0-1 km storm-relative helicity
- 124 m²/s²
- 0-3 km storm-relative helicity
- 77 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 25, 6:24 PM EDT | Mesoscale Discussion | SPC | Saint Mary's, Somerset, Worcester | 96 min |
| Aug 25, 2:47 PM EDT | Mesoscale Discussion | SPC | Albemarle, Amelia, Amherst, Appomattox, Bedford, Botetourt and 50 more | 58 min |
Nearby
Severe Thunderstorm Watches in Virginia, 2011Severe Thunderstorm Watches in Maryland, 2011Every 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.