Alert archive / Virginia / Severe Thunderstorm Watches in 2007

Severe Thunderstorm Watch 556

July 27, 200712 counties in Maryland; 76 counties in Virginia; 12 counties in West Virginia

The Storm Prediction Center issued this severe thunderstorm watch at Jul 27, 2007, 1:26 PM EDT for 12 counties in Maryland; 76 counties in Virginia; 12 counties in West Virginia. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Jul 27, 2007, 1:26 PM EDT (17:26 UTC)
Expired: Jul 27, 2007, 7:15 PM EDT
In force: 6 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1 in
Strongest gust expected: 60 kt

All 100 counties

Allegany County, MD, Anne Arundel County, MD, Baltimore 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, Washington County, MD, Albemarle County, VA, Alleghany County, VA, Amherst County, VA, Appomattox County, VA, Arlington County, VA, Augusta County, VA, Bath County, VA, Bedford County, VA, Bland County, VA, Botetourt County, VA, Buckingham County, VA, Campbell County, VA, Caroline County, VA, Carroll County, VA, Charlotte County, VA, City of Alexandria, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Covington, VA, City of Danville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Galax, VA, City of Harrisonburg, VA, City of Lexington, VA, City of Lynchburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Martinsville, VA, City of Radford, VA, City of Roanoke, VA, City of Salem, VA, City of Staunton, VA, City of Waynesboro, VA, City of Winchester, VA, Clarke County, VA, Craig County, VA, Culpeper County, VA, Cumberland County, VA, Fairfax County, VA, Fauquier County, VA, Floyd County, VA, Fluvanna County, VA, Franklin County, VA, Frederick County, VA, Giles County, VA, Grayson County, VA, Greene County, VA, Halifax County, VA, Henry County, VA, Highland County, VA, King George County, VA, Loudoun County, VA, Louisa County, VA, Madison County, VA, Montgomery County, VA, Nelson County, VA, Orange County, VA, Page County, VA, Patrick County, VA, Pittsylvania County, VA, Prince Edward County, VA, Prince William County, VA, Pulaski County, VA, Rappahannock County, VA, Roanoke County, VA, Rockbridge County, VA, Rockingham County, VA, Shenandoah County, VA, Smyth County, VA, Spotsylvania County, VA, Stafford County, VA, Tazewell County, VA, Warren County, VA, Wythe County, VA, Berkeley County, WV, Grant County, WV, Greenbrier County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Mercer County, WV, Mineral County, WV, Monroe County, WV, Morgan County, WV, Pendleton County, WV, Summers County, WV

The radar

The Sterling radar (KLWX), 129 km from the middle of the area, began a volume at 17:26 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

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

Issued	Product	Office	Counties	Lasted
Jul 27, 1:26 PM EDT	Severe Thunderstorm Warning	RNK	Montgomery, City of Radford	55 min
Jul 27, 1:37 PM EDT	Severe Thunderstorm Warning	RNK	Giles	48 min
Jul 27, 1:42 PM EDT	Severe Thunderstorm Warning	RNK	Patrick	78 min
Jul 27, 2:40 PM EDT	Severe Thunderstorm Warning	RNK	Roanoke, City of Roanoke, City of Salem	47 min
Jul 27, 2:42 PM EDT	Severe Thunderstorm Warning	LWX	Allegany	63 min
Jul 27, 2:47 PM EDT	Severe Thunderstorm Warning	RNK	Franklin	58 min
Jul 27, 2:49 PM EDT	Severe Thunderstorm Warning	LWX	Mineral	41 min
Jul 27, 3:14 PM EDT	Severe Thunderstorm Warning	LWX	Frederick, City of Winchester	25 min
Jul 27, 3:29 PM EDT	Severe Thunderstorm Warning	RNK	Bedford	76 min
Jul 27, 4:37 PM EDT	Severe Thunderstorm Warning	RNK	Pittsylvania, City of Danville	38 min
Jul 27, 4:42 PM EDT	Severe Thunderstorm Warning	RNK	Bath	63 min
Jul 27, 4:50 PM EDT	Severe Thunderstorm Warning	RNK	Halifax	69 min
Jul 27, 5:01 PM EDT	Severe Thunderstorm Warning	RNK	Campbell, Charlotte	62 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, 5.4 hours before the alert went out and 147 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: 1044 J/kg
Mixed-layer CIN: -34 J/kg
Mixed-layer LCL: 758 m above ground
0-6 km bulk shear: 19 kt
0-1 km storm-relative helicity: 74 m²/s²
0-3 km storm-relative helicity: 72 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 27, 12:09 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Baltimore, Carroll, Cecil, Frederick, Harford and 6 more	96 min
Jul 27, 3:37 PM EDT	Mesoscale Discussion	SPC	Allegany, Anne Arundel, Baltimore, Carroll, Charles, Frederick and 8 more	83 min
Jul 27, 2:33 PM EDT	Severe Thunderstorm Watch	SPC	Cabell, Wayne	7 hr

Nearby

Severe Thunderstorm Watches in Virginia, 2007 Severe Thunderstorm Watches in Maryland, 2007 Severe Thunderstorm Watches in West Virginia, 2007 Every severe thunderstorm watch in 2007

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.