Alert archive / Virginia / Mesoscale Discussions in 2013

Mesoscale Discussion 458

April 12, 201340 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Apr 12, 2013, 5:05 AM EDT for 40 counties in Virginia. It was in force for 85 min.

The area

The outline as issued.

The facts

Issued: Apr 12, 2013, 5:05 AM EDT (09:05 UTC)
Expired: Apr 12, 2013, 6:30 AM EDT
In force: 85 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 40 counties

Albemarle County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Brunswick County, VA, Buckingham County, VA, Campbell County, VA, Caroline County, VA, Charles City County, VA, Charlotte County, VA, Chesterfield County, VA, City of Charlottesville, VA, City of Colonial Heights, VA, City of Emporia, VA, City of Hopewell, VA, City of Lynchburg, VA, City of Petersburg, VA, City of Richmond, VA, Cumberland County, VA, Dinwiddie County, VA, Fluvanna County, VA, Goochland County, VA, Greensville County, VA, Halifax County, VA, Hanover County, VA, Henrico County, VA, King and Queen County, VA, King William County, VA, Louisa County, VA, Lunenburg County, VA, Mecklenburg County, VA, Nelson County, VA, New Kent County, VA, Nottoway County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA, Prince George County, VA, Surry County, VA, Sussex County, VA

The radar

The Norfolk radar (KAKQ), 120 km from the middle of the area, began a volume at 09:07 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.

Tornado Watch 104Apr 12, 5:20 AM EDT

The nearest sounding before it

Roanoke, VA (KRNK), launched 00:00Z, 9.1 hours before the alert went out and 104 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1699 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 81 m²/s²
0-3 km storm-relative helicity: 85 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
Apr 12, 1:58 AM EDT	Mesoscale Discussion	SPC	Amelia, Appomattox, Brunswick, Buckingham, Campbell, Charlotte and 24 more	92 min
Apr 12, 5:21 AM EDT	Tornado Watch	SPC	Amelia, Brunswick, Chesterfield, Cumberland, Dinwiddie, Fluvanna and 19 more	3 hr
Apr 12, 7:25 AM EDT	Mesoscale Discussion	SPC	Brunswick, Charles City, Chesterfield, Dinwiddie, Greensville, Henrico and 10 more	65 min
Apr 12, 2:34 PM EDT	Mesoscale Discussion	SPC	Gloucester, Isle of Wight, Lancaster, Mathews, Middlesex, Northampton and 11 more	116 min

Nearby

Mesoscale Discussions in Virginia, 2013 Every mesoscale discussion in 2013

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.