Alert archive / Virginia / Mesoscale Discussions in 2008

Mesoscale Discussion 478

March 19, 20085 counties in North Carolina; 24 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Mar 19, 2008, 11:28 PM EDT for 5 counties in North Carolina; 24 counties in Virginia. It was in force for 62 min.

The area

The outline as issued.

The facts

Issued: Mar 19, 2008, 11:28 PM EDT (03:28 UTC)
Expired: Mar 20, 2008, 12:30 AM EDT
In force: 62 min
Issued by: the Storm Prediction Center

All 29 counties

Alamance County, NC, Caswell County, NC, Guilford County, NC, Person County, NC, Rockingham County, NC, Albemarle County, VA, Appomattox County, VA, Buckingham County, VA, Campbell County, VA, Charlotte County, VA, City of Charlottesville, VA, City of Danville, VA, City of Lynchburg, VA, City of Martinsville, VA, Culpeper County, VA, Cumberland County, VA, Fluvanna County, VA, Goochland County, VA, Greene County, VA, Halifax County, VA, Henry County, VA, Louisa County, VA, Madison County, VA, Nelson County, VA, Orange County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA, Spotsylvania County, VA

The radar

The Roanoke radar (KFCX), 125 km from the middle of the area, began a volume at 03:31 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 137Mar 20, 12:00 AM EDT

The nearest sounding before it

Roanoke, VA (KRNK), launched 00:00Z, 3.5 hours before the alert went out and 57 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: 186 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 606 m above ground
0-6 km bulk shear: 114 kt
0-1 km storm-relative helicity: 640 m²/s²
0-3 km storm-relative helicity: 689 m²/s²
Significant tornado parameter: 0.8
Supercell composite: 3.2

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
Mar 20, 12:01 AM EDT	Severe Thunderstorm Watch	SPC	Arlington, Fairfax, King George, Prince William, Spotsylvania, Stafford and 6 more	3 hr

Nearby

Mesoscale Discussions in Virginia, 2008 Mesoscale Discussions in North Carolina, 2008 Every mesoscale discussion in 2008

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.