Alert archive / Virginia / Mesoscale Discussions in 2011

Mesoscale Discussion 645

April 27, 20119 counties in North Carolina; 74 counties in Virginia; 4 counties in West Virginia

The Storm Prediction Center issued this mesoscale discussion at Apr 27, 2011, 10:12 PM EDT for 9 counties in North Carolina; 74 counties in Virginia; 4 counties in West Virginia. It was in force for 63 min.

The area

The outline as issued.

The facts

Issued: Apr 27, 2011, 10:12 PM EDT (02:12 UTC)
Expired: Apr 27, 2011, 11:15 PM EDT
In force: 63 min
Issued by: the Storm Prediction Center

All 87 counties

Alleghany County, NC, Ashe County, NC, Forsyth County, NC, Rockingham County, NC, Stokes County, NC, Surry County, NC, Watauga County, NC, Wilkes County, NC, Yadkin County, NC, Albemarle County, VA, Alleghany County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Arlington County, VA, Augusta County, VA, Bath County, VA, Bedford County, VA, Bland County, VA, Botetourt County, VA, Buckingham County, VA, Campbell County, VA, Caroline County, VA, Carroll County, VA, Charlotte County, VA, Chesterfield County, VA, City of Alexandria, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Covington, VA, City of Danville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Galax, VA, City of Harrisonburg, VA, City of Lexington, VA, City of Lynchburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Martinsville, VA, City of Radford, VA, City of Richmond, VA, City of Roanoke, VA, City of Salem, VA, City of Staunton, VA, City of Waynesboro, VA, Craig County, VA, Culpeper County, VA, Cumberland County, VA, Fairfax County, VA, Fauquier County, VA, Floyd County, VA, Fluvanna County, VA, Franklin County, VA, Giles County, VA, Goochland County, VA, Grayson County, VA, Greene County, VA, Hanover County, VA, Henry County, VA, King George County, VA, Loudoun County, VA, Louisa County, VA, Madison County, VA, Montgomery County, VA, Nelson County, VA, Nottoway County, VA, Orange County, VA, Page County, VA, Patrick County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA, Prince William County, VA, Pulaski County, VA, Rappahannock County, VA, Roanoke County, VA, Rockbridge County, VA, Smyth County, VA, Spotsylvania County, VA, Stafford County, VA, Wythe County, VA, Greenbrier County, WV, Mercer County, WV, Monroe County, WV, Summers County, WV

The radar

The Roanoke radar (KFCX), 97 km from the middle of the area, began a volume at 02:12 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 247Apr 28, 12:40 AM EDT

The nearest sounding before it

Roanoke, VA (KRNK), launched 00:00Z, 2.2 hours before the alert went out and 40 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: 372 J/kg
Mixed-layer CIN: -24 J/kg
Mixed-layer LCL: 1272 m above ground
0-6 km bulk shear: 48 kt
0-1 km storm-relative helicity: 226 m²/s²
0-3 km storm-relative helicity: 335 m²/s²
Significant tornado parameter: 0.4
Supercell composite: 3.0

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 28, 12:09 AM EDT	Mesoscale Discussion	SPC	Alexander, Alleghany, Ashe, Avery, Buncombe, Burke and 25 more	36 min
Apr 28, 12:27 AM EDT	Mesoscale Discussion	SPC	Alamance, Alleghany, Ashe, Caswell, Davidson, Davie and 11 more	63 min
Apr 28, 12:41 AM EDT	Tornado Watch	SPC	Alamance, Alleghany, Ashe, Caswell, Davidson, Forsyth and 10 more	7 hr
Apr 28, 12:56 AM EDT	Tornado Watch	SPC	Alexander, Avery, Buncombe, Burke, Cabarrus, Caldwell and 21 more	4 hr
Apr 28, 3:30 AM EDT	Mesoscale Discussion	SPC	Alexander, Anson, Burke, Cabarrus, Catawba, Cleveland and 10 more	90 min
Apr 28, 4:30 AM EDT	Tornado Watch	SPC	Alamance, Anson, Bladen, Chatham, Cumberland, Davidson and 27 more	10 hr
Apr 28, 7:38 AM EDT	Tornado Watch	SPC	Bertie, Camden, Caswell, Chowan, Currituck, Gates and 9 more	7 hr
Apr 28, 8:05 AM EDT	Mesoscale Discussion	SPC	Anson, Chatham, Cumberland, Durham, Edgecombe, Franklin and 15 more	85 min
Apr 28, 8:48 AM EDT	Tornado Watch	SPC	Beaufort, Bladen, Brunswick, Carteret, Columbus, Craven and 15 more	7 hr
Apr 28, 11:22 AM EDT	Mesoscale Discussion	SPC	Beaufort, Bertie, Bladen, Brunswick, Chowan, Columbus and 29 more	53 min
Apr 28, 2:41 PM EDT	Tornado Watch	SPC	Beaufort, Bertie, Camden, Carteret, Chowan, Craven and 21 more	6 hr
Apr 28, 3:19 PM EDT	Tornado Watch	SPC	Bladen, Brunswick, Columbus, New Hanover, Pender	4 hr
Apr 28, 6:33 PM EDT	Mesoscale Discussion	SPC	Beaufort, Bertie, Camden, Carteret, Chowan, Craven and 20 more	57 min
Apr 27, 9:22 PM EDT	Mesoscale Discussion	SPC	Buchanan, Dickenson, Lee, Russell, Scott, Smyth and 5 more	53 min
Apr 28, 12:34 AM EDT	Mesoscale Discussion	SPC	Buchanan, Dickenson, Lee, Russell, Scott, Tazewell and 3 more	26 min
Apr 28, 10:44 AM EDT	Mesoscale Discussion	SPC	Albemarle, Amelia, Amherst, Appomattox, Arlington, Bedford and 69 more	61 min
Apr 28, 2:00 PM EDT	Mesoscale Discussion	SPC	Accomack, Amelia, Arlington, Brunswick, Caroline, Charles City and 47 more	60 min

Nearby

Mesoscale Discussions in Virginia, 2011 Mesoscale Discussions in North Carolina, 2011 Mesoscale Discussions in West Virginia, 2011 Every mesoscale discussion in 2011

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.