Alert archive / North Carolina / Mesoscale Discussions in 2008

Mesoscale Discussion 671

April 20, 200848 counties in North Carolina; 25 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Apr 20, 2008, 4:20 PM EDT for 48 counties in North Carolina; 25 counties in Virginia. It was in force for 85 min.

The area

The outline as issued.

The facts

Issued: Apr 20, 2008, 4:20 PM EDT (20:20 UTC)
Expired: Apr 20, 2008, 5:45 PM EDT
In force: 85 min
Issued by: the Storm Prediction Center

All 73 counties

Alamance County, NC, Beaufort County, NC, Bertie County, NC, Camden County, NC, Carteret County, NC, Caswell County, NC, Chatham County, NC, Chowan County, NC, Craven County, NC, Cumberland County, NC, Currituck County, NC, Dare County, NC, Duplin 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, Hyde County, NC, Johnston County, NC, Jones County, NC, Lee County, NC, Lenoir County, NC, Martin County, NC, Moore County, NC, Nash County, NC, Northampton County, NC, Orange County, NC, Pamlico County, NC, Pasquotank County, NC, Perquimans County, NC, Person County, NC, Pitt County, NC, Randolph County, NC, Rockingham County, NC, Tyrrell County, NC, Vance County, NC, Wake County, NC, Warren County, NC, Washington County, NC, Wayne County, NC, Wilson County, NC, Brunswick County, VA, City of Chesapeake, VA, City of Danville, VA, City of Emporia, VA, City of Franklin, VA, City of Hampton, VA, City of Martinsville, VA, City of Newport News, VA, City of Norfolk, VA, City of Petersburg, VA, City of Poquoson, VA, City of Portsmouth, VA, City of Suffolk, VA, City of Virginia Beach, VA, City of Williamsburg, VA, Dinwiddie County, VA, Greensville County, VA, Halifax County, VA, Isle of Wight County, VA, Lunenburg County, VA, Mecklenburg County, VA, Prince George County, VA, Southampton County, VA, Surry County, VA, Sussex County, VA

The radar

The Raleigh/Durham radar (KRAX), 68 km from the middle of the area, began a volume at 20:21 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 210Apr 20, 8:00 PM EDT

The nearest sounding before it

Newport, NC (KMHX), launched 12:00Z, 8.3 hours before the alert went out and 132 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: 457 J/kg
Mixed-layer CIN: -104 J/kg
Mixed-layer LCL: 793 m above ground
0-6 km bulk shear: 28 kt
0-1 km storm-relative helicity: 303 m²/s²
0-3 km storm-relative helicity: 426 m²/s²
Significant tornado parameter: 0.4
Supercell composite: 1.3

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, 9:00 PM EDT	Mesoscale Discussion	SPC	Alamance, Alexander, Anson, Cabarrus, Caswell, Catawba and 24 more	60 min
Apr 20, 1:14 PM EDT	Mesoscale Discussion	SPC	Alamance, Anson, Beaufort, Bertie, Cabarrus, Caswell and 44 more	2 hr
Apr 20, 1:47 PM EDT	Severe Thunderstorm Watch	SPC	Alamance, Beaufort, Bertie, Camden, Carteret, Caswell and 48 more	8 hr
Apr 20, 7:14 PM EDT	Mesoscale Discussion	SPC	Beaufort, Bertie, Camden, Carteret, Chowan, Craven and 28 more	61 min
Apr 20, 11:20 AM EDT	Mesoscale Discussion	SPC	Chesterfield, Dinwiddie, Greensville, Hanover, City of Colonial Heights, City of Emporia and 3 more	2 hr
Apr 20, 6:44 PM EDT	Mesoscale Discussion	SPC	Caroline, Charles City, Essex, Hanover, Henrico, James City and 15 more	61 min

Nearby

Mesoscale Discussions in North Carolina, 2008 Mesoscale Discussions in Virginia, 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.