Alert archive / Virginia / Mesoscale Discussions in 2017

Mesoscale Discussion 458

April 6, 20174 counties in Maryland; 38 counties in North Carolina; 73 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Apr 6, 2017, 5:59 AM EDT for 4 counties in Maryland; 38 counties in North Carolina; 73 counties in Virginia. It was in force for 91 min.

The area

The outline as issued.

The facts

Issued: Apr 6, 2017, 5:59 AM EDT (09:59 UTC)
Expired: Apr 6, 2017, 7:30 AM EDT
In force: 91 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 115 counties

Calvert County, MD, Charles County, MD, Dorchester County, MD, Saint Mary's County, MD, Alamance County, NC, Bertie County, NC, Camden County, NC, Caswell County, NC, Chatham County, NC, Chowan County, NC, Cumberland County, NC, Durham County, NC, Edgecombe County, NC, Franklin County, NC, Gates County, NC, Granville County, NC, Greene County, NC, Guilford County, NC, Halifax County, NC, Harnett County, NC, Hertford County, NC, Hoke County, NC, Johnston County, NC, Lee County, NC, Martin County, NC, Montgomery County, NC, Moore County, NC, Nash County, NC, Northampton County, NC, Orange County, NC, Pasquotank County, NC, Perquimans County, NC, Person County, NC, Pitt County, NC, Randolph County, NC, Rockingham County, NC, Sampson County, NC, Vance County, NC, Wake County, NC, Warren County, NC, Wayne County, NC, Wilson County, NC, Albemarle County, VA, Amelia 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 Alexandria, VA, City of Charlottesville, VA, City of Chesapeake, VA, City of Colonial Heights, VA, City of Danville, VA, City of Emporia, VA, City of Fairfax, VA, City of Franklin, VA, City of Fredericksburg, VA, City of Hampton, VA, City of Hopewell, VA, City of Lynchburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Newport News, VA, City of Norfolk, VA, City of Petersburg, VA, City of Poquoson, VA, City of Portsmouth, VA, City of Richmond, VA, City of Suffolk, VA, City of Virginia Beach, VA, City of Williamsburg, VA, Cumberland County, VA, Dinwiddie County, VA, Essex County, VA, Fairfax County, VA, Fluvanna County, VA, Gloucester County, VA, Goochland County, VA, Greensville County, VA, Halifax County, VA, Hanover County, VA, Henrico County, VA, Isle of Wight County, VA, James City County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Lancaster County, VA, Louisa County, VA, Lunenburg County, VA, Mathews County, VA, Mecklenburg County, VA, Middlesex County, VA, Nelson County, VA, New Kent County, VA, Northumberland County, VA, Nottoway County, VA, Orange County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA, Prince George County, VA, Prince William County, VA, Richmond County, VA, Southampton County, VA, Spotsylvania County, VA, Stafford County, VA, Surry County, VA, Sussex County, VA, Westmoreland County, VA, York County, VA

The radar

The Norfolk radar (KAKQ), 104 km from the middle of the area, began a volume at 10:02 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 132Apr 6, 7:05 AM EDT

The nearest sounding before it

Roanoke, VA (KRNK), launched 00:00Z, 10.0 hours before the alert went out and 147 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: 1255 m above ground
0-6 km bulk shear: 72 kt
0-1 km storm-relative helicity: 311 m²/s²
0-3 km storm-relative helicity: 305 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 6, 7:06 AM EDT	Tornado Watch	SPC	Dorchester, Somerset, Wicomico, Worcester	8 hr
Apr 6, 12:18 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Calvert, Caroline, Cecil, Charles, Dorchester and 9 more	57 min
Apr 6, 12:45 PM EDT	Severe Thunderstorm Watch	SPC	Anne Arundel, Baltimore, Calvert, Caroline, Cecil, Charles and 9 more	4 hr
Apr 6, 3:12 PM EDT	Mesoscale Discussion	SPC	Cecil, Kent	63 min
Apr 5, 11:50 PM EDT	Severe Thunderstorm Watch	SPC	Alexander, Cabarrus, Catawba, Cleveland, Davie, Gaston and 5 more	6 hr
Apr 6, 12:51 AM EDT	Mesoscale Discussion	SPC	Alamance, Anson, Caswell, Chatham, Davidson, Durham and 15 more	114 min
Apr 6, 2:54 AM EDT	Mesoscale Discussion	SPC	Alamance, Anson, Cabarrus, Davidson, Guilford, Montgomery and 4 more	96 min
Apr 6, 10:38 AM EDT	Mesoscale Discussion	SPC	Bertie, Chowan, Edgecombe, Gates, Greene, Halifax and 8 more	67 min

Nearby

Mesoscale Discussions in Virginia, 2017 Mesoscale Discussions in North Carolina, 2017 Mesoscale Discussions in Maryland, 2017 Every mesoscale discussion in 2017

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.