Alert archive / Virginia / Mesoscale Discussions in 2013

Mesoscale Discussion 542

April 19, 20134 states

The Storm Prediction Center issued this mesoscale discussion at Apr 19, 2013, 6:54 PM EDT for 4 states. It was in force for 66 min.

The area

The outline as issued.

The facts

Issued: Apr 19, 2013, 6:54 PM EDT (22:54 UTC)
Expired: Apr 19, 2013, 8:00 PM EDT
In force: 66 min
Issued by: the Storm Prediction Center

All 69 counties

Anne Arundel County, MD, Calvert County, MD, Caroline County, MD, Charles County, MD, City of Baltimore, MD, Dorchester County, MD, Howard County, MD, Kent County, MD, Montgomery County, MD, Prince George's County, MD, Queen Anne's County, MD, Saint Mary's County, MD, Talbot County, MD, Bladen County, NC, Cumberland County, NC, Edgecombe County, NC, Franklin County, NC, Greene County, NC, Halifax County, NC, Harnett County, NC, Johnston County, NC, Nash County, NC, Northampton County, NC, Robeson County, NC, Sampson County, NC, Vance County, NC, Wake County, NC, Warren County, NC, Wayne County, NC, Wilson County, NC, Dillon County, SC, Arlington County, VA, Brunswick County, VA, Caroline County, VA, Charles City County, VA, Chesterfield County, VA, City of Alexandria, VA, City of Colonial Heights, VA, City of Emporia, VA, City of Fairfax, VA, City of Falls Church, VA, City of Franklin, VA, City of Fredericksburg, VA, City of Hopewell, VA, City of Petersburg, VA, City of Richmond, VA, City of Williamsburg, VA, Dinwiddie County, VA, Essex County, VA, Fairfax County, VA, Gloucester County, VA, Greensville County, VA, Hanover County, VA, Henrico County, VA, James City County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Lancaster County, VA, Middlesex County, VA, New Kent County, VA, Northumberland County, VA, Prince George County, VA, Richmond County, VA, Southampton County, VA, Stafford County, VA, Surry County, VA, Sussex County, VA, Westmoreland County, VA

The radar

The Norfolk radar (KAKQ), 54 km from the middle of the area, began a volume at 22:55 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 135Apr 19, 8:10 PM EDT

The nearest sounding before it

Roanoke, VA (KRNK), launched 12:00Z, 10.9 hours before the alert went out and 181 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: 105 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 491 m above ground
0-6 km bulk shear: 35 kt
0-1 km storm-relative helicity: 250 m²/s²
0-3 km storm-relative helicity: 333 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 0.5

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, 1:27 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles and 11 more	63 min
Apr 19, 2:31 PM EDT	Tornado Watch	SPC	Anne Arundel, Baltimore, Calvert, Caroline, Carroll, Cecil and 13 more	7 hr
Apr 19, 4:36 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles and 9 more	114 min
Apr 19, 6:27 PM EDT	Severe Thunderstorm Watch	SPC	Somerset, Wicomico, Worcester	4 hr
Apr 19, 12:35 PM EDT	Mesoscale Discussion	SPC	Alamance, Alexander, Anson, Burke, Cabarrus, Caswell and 29 more	115 min
Apr 19, 2:00 PM EDT	Tornado Watch	SPC	Alamance, Alexander, Anson, Cabarrus, Catawba, Chatham and 31 more	7 hr
Apr 19, 4:48 PM EDT	Mesoscale Discussion	SPC	Alamance, Anson, Beaufort, Bertie, Bladen, Brunswick and 58 more	57 min
Apr 19, 12:37 PM EDT	Severe Thunderstorm Watch	SPC	Aiken, Bamberg, Barnwell, Calhoun, Clarendon, Edgefield and 6 more	6 hr
Apr 19, 1:57 PM EDT	Mesoscale Discussion	SPC	Aiken, Allendale, Bamberg, Barnwell, Beaufort, Berkeley and 12 more	2 hr
Apr 19, 2:36 PM EDT	Severe Thunderstorm Watch	SPC	Allendale, Beaufort, Berkeley, Charleston, Colleton, Dorchester and 2 more	7 hr
Apr 19, 4:29 PM EDT	Mesoscale Discussion	SPC	Aiken, Allendale, Bamberg, Barnwell, Beaufort, Berkeley and 9 more	2 hr
Apr 19, 6:37 PM EDT	Mesoscale Discussion	SPC	Beaufort, Berkeley, Charleston, Clarendon, Colleton, Dorchester	113 min

Nearby

Mesoscale Discussions in Virginia, 2013 Mesoscale Discussions in North Carolina, 2013 Mesoscale Discussions in Maryland, 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.