Alert archive / Virginia / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 12, NWS Blacksburg, VA

April 20, 2009Appomattox County, Buckingham County, Virginia

NWS Blacksburg, VA issued this severe thunderstorm warning at Apr 20, 2009, 5:03 PM EDT for Appomattox County, Buckingham County, Virginia. It was in force for 56 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: Apr 20, 2009, 5:03 PM EDT (21:03 UTC)
Expired: Apr 20, 2009, 5:59 PM EDT
In force: 56 min
Issued by: NWS Blacksburg, VA
Area: Storm-based polygon

Counties Appomattox County, VA, Buckingham County, VA

The radar

The Roanoke radar (KFCX), 150 km from the middle of the area, began a volume at 21:04 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 watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Apr 20, 2:50 PM EDT	Tornado Watch	SPC	7 hr

The nearest sounding before it

Roanoke, VA (KRNK), launched 12:00Z, 9.1 hours before the alert went out and 79 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: 23 J/kg
Mixed-layer CIN: -38 J/kg
Mixed-layer LCL: 526 m above ground
0-6 km bulk shear: 59 kt
0-1 km storm-relative helicity: 185 m²/s²
0-3 km storm-relative helicity: 217 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

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 Blacksburg, VA wrote its last area forecast discussion before this severe thunderstorm warning went out at Apr 20, 4:57 PM EDT, 6 minutes earlier.

Area forecast discussion, Apr 20, 4:57 PM EDT, 6 minutes before

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Hazardous weather outlook, Apr 20, 3:37 PM EDT, 1 hour 26 minutes before

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In the hours before

Local storm report, Apr 20, 4:06 PM EDT, 57 minutes before

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Local storm report, Apr 20, 4:09 PM EDT, 54 minutes before

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Special weather statement, Apr 20, 4:09 PM EDT, 54 minutes before

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Special weather statement, Apr 20, 4:26 PM EDT, 37 minutes before

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Special weather statement, Apr 20, 4:39 PM EDT, 24 minutes before

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Local storm report, Apr 20, 4:50 PM EDT, 13 minutes before

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The office that day

Everything else NWS Blacksburg, VA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 20, 3:01 PM EDT	Severe Thunderstorm Warning	RNK	Carroll, Floyd, Patrick	48 min
Apr 20, 3:23 PM EDT	Severe Thunderstorm Warning	RNK	Amherst, Bedford	82 min
Apr 20, 3:31 PM EDT	Severe Thunderstorm Warning	RNK	Bedford, Campbell, Franklin, Pittsylvania	56 min
Apr 20, 4:09 PM EDT	Special Weather Statement	RNK	City of Lynchburg	66 min
Apr 20, 4:26 PM EDT	Special Weather Statement	RNK	Appomattox	64 min
Apr 20, 4:39 PM EDT	Special Weather Statement	RNK	Charlotte	66 min
Apr 20, 4:53 PM EDT	Severe Thunderstorm Warning	RNK	Charlotte, Halifax	32 min

Nearby

Severe Thunderstorm Warnings in Virginia, 2009 Every severe thunderstorm warning in 2009

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.