Alert archive / Virginia / Severe Thunderstorm Watches in 2011
Severe Thunderstorm Watch 631
The Storm Prediction Center issued this severe thunderstorm watch at Jul 11, 2011, 5:47 PM EDT for 4 states. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 11, 2011, 5:47 PM EDT (21:47 UTC)
- Expired
- Jul 11, 2011, 10:42 PM EDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
All 64 counties
Allegany County, MD, Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Carroll County, MD, Charles County, MD, City of Baltimore, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Saint Mary's County, MD, Washington County, MD, Bedford County, PA, Blair County, PA, Cambria County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Mifflin County, PA, Somerset County, PA, Albemarle County, VA, Arlington County, VA, Augusta 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, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, Greene County, VA, Highland County, VA, King George County, VA, Loudoun County, VA, Madison County, VA, Nelson County, VA, Orange County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Rockingham County, VA, Shenandoah County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Berkeley County, WV, Grant County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Mineral County, WV, Morgan County, WV, Pendleton County, WV
The radar
The Sterling radar (KLWX), 133 km from the middle of the area, began a volume at 21:50 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
- 30%
- One or more hailstones of 2 inches or more
- 20%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
16 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 11, 5:52 PM EDT | Severe Thunderstorm Warning | CTP | Bedford, Blair, Cambria, Somerset | 53 min |
| Jul 11, 6:40 PM EDT | Severe Thunderstorm Warning | LWX | Washington | 35 min |
| Jul 11, 6:48 PM EDT | Severe Thunderstorm Warning | CTP | Bedford, Blair, Cambria, Fulton, Huntingdon, Somerset | 57 min |
| Jul 11, 6:54 PM EDT | Severe Thunderstorm Warning | LWX | Allegany | 37 min |
| Jul 11, 7:05 PM EDT | Severe Thunderstorm Warning | LWX | Carroll, Frederick, Washington | 40 min |
| Jul 11, 7:10 PM EDT | Severe Thunderstorm Warning | LWX | Frederick, Montgomery, Washington | 35 min |
| Jul 11, 7:34 PM EDT | Severe Thunderstorm Warning | LWX | Baltimore, Carroll, Frederick | 41 min |
| Jul 11, 7:42 PM EDT | Severe Thunderstorm Warning | LWX | Frederick, Howard, Montgomery | 48 min |
| Jul 11, 7:57 PM EDT | Severe Thunderstorm Warning | LWX | Culpeper, Fauquier, Prince William, Spotsylvania, Stafford, City of Fredericksburg | 48 min |
| Jul 11, 8:06 PM EDT | Severe Thunderstorm Warning | LWX | Anne Arundel, Howard, Montgomery, Prince George's | 39 min |
| Jul 11, 8:15 PM EDT | Severe Thunderstorm Warning | LWX | Anne Arundel, Baltimore, Carroll, Harford, Howard, Montgomery and 1 more | 45 min |
| Jul 11, 8:34 PM EDT | Severe Thunderstorm Warning | LWX | Fairfax, Loudoun, Prince William, City of Fairfax, City of Manassas, City of Manassas Park | 26 min |
| Jul 11, 8:46 PM EDT | Severe Thunderstorm Warning | LWX | Anne Arundel, Calvert, Charles, Howard, Montgomery, Prince George's | 44 min |
| Jul 11, 8:56 PM EDT | Severe Thunderstorm Warning | LWX | Anne Arundel, Baltimore, Harford, Howard, City of Baltimore | 34 min |
| Jul 11, 9:17 PM EDT | Tornado Warning | LWX | Harford | 19 min |
| Jul 11, 9:26 PM EDT | Severe Thunderstorm Warning | LWX | Anne Arundel, Calvert, Charles, Prince George's, Saint Mary's | 64 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, 9.8 hours before the alert went out and 141 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
- 6 J/kg
- Mixed-layer CIN
- -140 J/kg
- Mixed-layer LCL
- 1061 m above ground
- 0-6 km bulk shear
- 22 kt
- 0-1 km storm-relative helicity
- 130 m²/s²
- 0-3 km storm-relative helicity
- 135 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 |
|---|---|---|---|---|
| Jul 11, 5:54 PM EDT | Mesoscale Discussion | SPC | Allegany, Garrett | 96 min |
| Jul 11, 7:44 PM EDT | Mesoscale Discussion | SPC | Allegany, Anne Arundel, Baltimore, Calvert, Carroll, Cecil and 12 more | 61 min |
| Jul 11, 1:42 PM EDT | Mesoscale Discussion | SPC | Allegheny, Beaver, Fayette, Greene, Lawrence, Washington | 93 min |
| Jul 11, 2:16 PM EDT | Severe Thunderstorm Watch | SPC | Allegheny, Beaver, Fayette, Greene, Washington, Westmoreland | 6 hr |
| Jul 11, 3:43 PM EDT | Mesoscale Discussion | SPC | Allegheny, Armstrong, Beaver, Butler, Crawford, Fayette and 6 more | 92 min |
Nearby
Severe Thunderstorm Watches in Virginia, 2011Severe Thunderstorm Watches in Maryland, 2011Severe Thunderstorm Watches in Pennsylvania, 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.