Alert archive / Virginia / Severe Thunderstorm Warnings in 2011

Severe Thunderstorm Warning 413, NWS Baltimore/Washington

September 3, 2011Fairfax County, Loudoun County, Virginia; Montgomery County, Maryland

NWS Baltimore/Washington issued this severe thunderstorm warning at Sep 3, 2011, 9:44 AM EDT for Fairfax County, Loudoun County, Virginia; Montgomery County, Maryland. It was in force for 46 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Sep 3, 2011, 9:44 AM EDT (13:44 UTC)
Expired: Sep 3, 2011, 10:30 AM EDT
In force: 46 min
Issued by: NWS Baltimore/Washington
Area: Storm-based polygon

Counties Montgomery County, MD, Fairfax County, VA, Loudoun County, VA

The radar

The Sterling radar (KLWX), 11 km from the middle of the area, began a volume at 13:47 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.

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 1.7 hours before the alert went out and 8 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: 115 J/kg
Mixed-layer CIN: -316 J/kg
Mixed-layer LCL: 585 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: 100 m²/s²
0-3 km storm-relative helicity: 197 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 6.6

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Baltimore/Washington wrote its last area forecast discussion before this severe thunderstorm warning went out at Sep 3, 3:47 AM EDT, 5 hours 57 minutes earlier.

Area forecast discussion, Sep 3, 3:47 AM EDT, 5 hours 57 minutes before

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Hazardous weather outlook, Sep 3, 3:55 AM EDT, 5 hours 49 minutes before

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In the hours before

Special weather statement, Sep 3, 8:43 AM EDT, 1 hour 1 minute before

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Special weather statement, Sep 3, 9:21 AM EDT, 23 minutes before

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The office that day

Everything else NWS Baltimore/Washington issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 3, 9:51 AM EDT	Special Weather Statement	LWX	Loudoun	24 min
Sep 3, 10:25 AM EDT	Special Weather Statement	LWX	Fauquier	35 min
Sep 3, 11:06 AM EDT	Special Weather Statement	LWX	Culpeper, Fauquier	24 min
Sep 3, 11:41 AM EDT	Special Weather Statement	LWX	Culpeper, Orange, Spotsylvania	34 min
Sep 3, 1:32 PM EDT	Special Weather Statement	LWX	City of Waynesboro	28 min
Sep 3, 1:49 PM EDT	Coastal Flood Advisory	LWX	Arlington, Fairfax, King George, Stafford, City of Alexandria, City of Fairfax and 1 more	14 hr
Sep 3, 2:04 PM EDT	Special Weather Statement	LWX	Augusta	56 min
Sep 3, 2:19 PM EDT	Special Weather Statement	LWX	Nelson	56 min
Sep 3, 2:24 PM EDT	Special Weather Statement	LWX	Highland	66 min
Sep 3, 2:33 PM EDT	Severe Thunderstorm Warning	LWX	Highland	24 min
Sep 3, 3:17 PM EDT	Severe Thunderstorm Warning	LWX	Rockingham	24 min
Sep 3, 4:59 PM EDT	Small Craft Advisory	LWX		3 days
Sep 3, 8:43 AM EDT	Special Weather Statement	LWX	Carroll	32 min
Sep 3, 9:21 AM EDT	Special Weather Statement	LWX	Carroll, Frederick, Howard, Montgomery	24 min
Sep 3, 10:29 AM EDT	Special Weather Statement	LWX	Montgomery	31 min
Sep 3, 10:45 AM EDT	Special Weather Statement	LWX	City of Baltimore	30 min
Sep 3, 1:43 PM EDT	Special Weather Statement	LWX	Pendleton	32 min
Sep 3, 2:27 PM EDT	Special Weather Statement	LWX	Pendleton	63 min
Sep 3, 2:45 PM EDT	Severe Thunderstorm Warning	LWX	Pendleton	45 min

Nearby

Severe Thunderstorm Warnings in Virginia, 2011 Severe Thunderstorm Warnings in Maryland, 2011 Every severe thunderstorm warning 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.