Alert archive / Virginia / Mesoscale Discussions in 2015

Mesoscale Discussion 405

April 20, 201522 counties in North Carolina; 56 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Apr 20, 2015, 6:27 PM EDT for 22 counties in North Carolina; 56 counties in Virginia. It was in force for 93 min.

The area

The outline as issued.

The facts

Issued: Apr 20, 2015, 6:27 PM EDT (22:27 UTC)
Expired: Apr 20, 2015, 8:00 PM EDT
In force: 93 min
Issued by: the Storm Prediction Center

All 78 counties

Alamance County, NC, Alleghany County, NC, Caswell County, NC, Chatham County, NC, Durham County, NC, Forsyth County, NC, Gates County, NC, Granville County, NC, Guilford County, NC, Hertford County, NC, Lee County, NC, Montgomery County, NC, Moore County, NC, Northampton County, NC, Orange County, NC, Person County, NC, Randolph County, NC, Rockingham County, NC, Stokes County, NC, Surry County, NC, Vance County, NC, Warren County, NC, Amelia County, VA, Appomattox County, VA, Bedford County, VA, Brunswick County, VA, Buckingham County, VA, Campbell County, VA, Carroll County, VA, Charles City County, VA, Charlotte County, VA, Chesterfield County, VA, City of Chesapeake, VA, City of Colonial Heights, VA, City of Danville, VA, City of Emporia, VA, City of Franklin, VA, City of Galax, VA, City of Hopewell, VA, City of Lynchburg, VA, City of Martinsville, VA, City of Newport News, VA, City of Petersburg, VA, City of Portsmouth, VA, City of Radford, VA, City of Richmond, VA, City of Roanoke, VA, City of Salem, VA, City of Suffolk, VA, City of Williamsburg, VA, Cumberland County, VA, Dinwiddie County, VA, Floyd County, VA, Franklin County, VA, Gloucester County, VA, Greensville County, VA, Halifax County, VA, Henrico County, VA, Henry County, VA, Isle of Wight County, VA, James City County, VA, King and Queen County, VA, King William County, VA, Lunenburg County, VA, Mecklenburg County, VA, Montgomery County, VA, New Kent County, VA, Nottoway County, VA, Patrick County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA, Prince George County, VA, Pulaski County, VA, Roanoke County, VA, Southampton County, VA, Surry County, VA, Sussex County, VA

The radar

The Raleigh/Durham radar (KRAX), 85 km from the middle of the area, began a volume at 22:30 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

Greensboro/Hi Pt, NC (KGSO), launched 12:00Z, 10.5 hours before the alert went out and 86 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: 17 J/kg
Mixed-layer CIN: -48 J/kg
Mixed-layer LCL: 654 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 59 m²/s²
0-3 km storm-relative helicity: 77 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.4

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 19, 9:06 PM EDT	Mesoscale Discussion	SPC	Bladen, Brunswick, Duplin, Durham, Edgecombe, Franklin and 13 more	54 min
Apr 20, 2:25 AM EDT	Mesoscale Discussion	SPC	Beaufort, Bertie, Camden, Chowan, Craven, Currituck and 16 more	95 min
Apr 20, 1:03 PM EDT	Mesoscale Discussion	SPC	Alexander, Anson, Buncombe, Burke, Cabarrus, Caldwell and 20 more	57 min
Apr 20, 1:23 PM EDT	Tornado Watch	SPC	Alexander, Avery, Buncombe, Burke, Cabarrus, Caldwell and 20 more	7 hr
Apr 20, 1:54 PM EDT	Mesoscale Discussion	SPC	Alleghany, Stokes, Surry	3 hr
Apr 20, 2:55 PM EDT	Severe Thunderstorm Watch	SPC	Alamance, Alleghany, Anson, Ashe, Bertie, Caswell and 33 more	7 hr
Apr 20, 4:18 PM EDT	Mesoscale Discussion	SPC	Alexander, Buncombe, Burke, Cabarrus, Caldwell, Catawba and 12 more	57 min
Apr 20, 6:45 PM EDT	Mesoscale Discussion	SPC	Alexander, Anson, Avery, Buncombe, Burke, Caldwell and 15 more	60 min
Apr 20, 3:08 PM EDT	Tornado Watch	SPC	Albemarle, Arlington, Augusta, Clarke, Culpeper, Fairfax and 27 more	9 hr
Apr 20, 5:01 PM EDT	Mesoscale Discussion	SPC	Albemarle, Arlington, Augusta, Caroline, Clarke, Culpeper and 30 more	119 min

Nearby

Mesoscale Discussions in Virginia, 2015 Mesoscale Discussions in North Carolina, 2015 Every mesoscale discussion in 2015

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.