Alert archive / Virginia / Severe Thunderstorm Watches in 2011

Severe Thunderstorm Watch 338

May 23, 20114 states

The Storm Prediction Center issued this severe thunderstorm watch at May 23, 2011, 10:48 AM EDT for 4 states. It was in force for 9 hr.

The area

The outline as issued.

The facts

Issued: May 23, 2011, 10:48 AM EDT (14:48 UTC)
Expired: May 23, 2011, 8:00 PM EDT
In force: 9 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1.5 in
Strongest gust expected: 60 kt

All 77 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, Adams County, PA, Bedford County, PA, Blair County, PA, Centre County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Juniata County, PA, Lancaster County, PA, Lebanon County, PA, Mifflin County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Schuylkill County, PA, Snyder County, PA, Union County, PA, York 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), 107 km from the middle of the area, began a volume at 14:50 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
May 23, 3:42 PM EDT	Severe Thunderstorm Warning	LWX	Frederick	31 min
May 23, 4:09 PM EDT	Severe Thunderstorm Warning	CTP	Centre, Huntingdon, Juniata, Mifflin, Snyder, Union	66 min
May 23, 4:13 PM EDT	Tornado Warning	CTP	Huntingdon, Juniata, Mifflin	32 min
May 23, 4:24 PM EDT	Severe Thunderstorm Warning	LWX	Clarke, Frederick, Loudoun	51 min
May 23, 4:45 PM EDT	Severe Thunderstorm Warning	LWX	Culpeper, Madison, Orange	45 min
May 23, 4:53 PM EDT	Severe Thunderstorm Warning	CTP	Centre, Clinton, Columbia, Lycoming, Montour, Northumberland and 3 more	52 min
May 23, 5:06 PM EDT	Severe Thunderstorm Warning	CTP	Dauphin, Juniata, Northumberland, Perry, Schuylkill, Snyder	54 min
May 23, 5:12 PM EDT	Severe Thunderstorm Warning	LWX	Frederick, Montgomery	48 min
May 23, 5:15 PM EDT	Tornado Warning	CTP	Juniata, Northumberland, Snyder	30 min
May 23, 5:49 PM EDT	Tornado Warning	CTP	Dauphin, Northumberland, Schuylkill	41 min
May 23, 6:02 PM EDT	Severe Thunderstorm Warning	CTP	Columbia, Lycoming, Montour, Northumberland, Schuylkill, Sullivan	58 min
May 23, 6:13 PM EDT	Severe Thunderstorm Warning	LWX	Howard, Montgomery, Prince George's	47 min
May 23, 6:15 PM EDT	Severe Thunderstorm Warning	CTP	Dauphin, Northumberland, Schuylkill, Snyder	60 min
May 23, 6:27 PM EDT	Severe Thunderstorm Warning	CTP	Lancaster, York	34 min
May 23, 6:32 PM EDT	Severe Thunderstorm Warning	CTP	Schuylkill	48 min
May 23, 6:45 PM EDT	Severe Thunderstorm Warning	LWX	Nelson	45 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, 2.8 hours before the alert went out and 111 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: 22 J/kg
Mixed-layer CIN: -131 J/kg
Mixed-layer LCL: 581 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: 152 m²/s²
0-3 km storm-relative helicity: 177 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 23, 10:33 AM EDT	Mesoscale Discussion	SPC	Allegany, Baltimore, Carroll, Frederick, Garrett, Howard and 4 more	87 min
May 23, 2:33 PM EDT	Mesoscale Discussion	SPC	Allegany, Carroll, Charles, Frederick, Howard, Montgomery and 1 more	87 min
May 23, 4:40 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles and 9 more	95 min
May 23, 8:25 AM EDT	Mesoscale Discussion	SPC	Crawford, Erie	65 min
May 22, 9:02 PM EDT	Mesoscale Discussion	SPC	Carroll, Craig, Floyd, Giles, Montgomery, Patrick and 5 more	58 min
May 23, 3:16 PM EDT	Severe Thunderstorm Watch	SPC	Alleghany, Amelia, Amherst, Appomattox, Bath, Bedford and 78 more	7 hr
May 23, 7:02 PM EDT	Mesoscale Discussion	SPC	Amelia, Appomattox, Brunswick, Buckingham, Campbell, Charles City and 40 more	58 min
May 23, 7:20 PM EDT	Mesoscale Discussion	SPC	Boone, Brooke, Cabell, Calhoun, Doddridge, Jackson and 16 more	85 min

Nearby

Severe Thunderstorm Watches in Virginia, 2011 Severe Thunderstorm Watches in Pennsylvania, 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.