Alert archive / Virginia / Mesoscale Discussions in 2011

Mesoscale Discussion 633

April 27, 201115 counties in Maryland; 11 counties in North Carolina; 60 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Apr 27, 2011, 6:00 PM EDT for 15 counties in Maryland; 11 counties in North Carolina; 60 counties in Virginia. It was in force for 60 min.

The area

The outline as issued.

The facts

Issued: Apr 27, 2011, 6:00 PM EDT (22:00 UTC)
Expired: Apr 27, 2011, 7:00 PM EDT
In force: 60 min
Issued by: the Storm Prediction Center

All 86 counties

Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Carroll County, MD, Charles County, MD, City of Baltimore, MD, Frederick County, MD, Harford 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, Alamance County, NC, Caswell County, NC, Durham County, NC, Franklin County, NC, Granville County, NC, Guilford County, NC, Orange County, NC, Person County, NC, Rockingham County, NC, Vance County, NC, Warren County, NC, Albemarle County, VA, Amelia County, VA, Appomattox County, VA, Arlington 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 Colonial Heights, VA, City of Danville, VA, City of Emporia, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Hopewell, VA, City of Manassas, VA, City of Manassas Park, VA, City of Petersburg, VA, City of Richmond, VA, Culpeper County, VA, Cumberland County, VA, Dinwiddie County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Fluvanna County, VA, Goochland County, VA, Greene County, VA, Greensville County, VA, Halifax County, VA, Hanover County, VA, Henrico County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Loudoun County, VA, Louisa County, VA, Lunenburg County, VA, Madison County, VA, Mecklenburg County, VA, Nelson County, VA, New Kent 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, Rappahannock County, VA, Richmond County, VA, Spotsylvania County, VA, Stafford County, VA, Sussex County, VA, Westmoreland County, VA

The radar

The Norfolk radar (KAKQ), 109 km from the middle of the area, began a volume at 22:00 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.

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 10.0 hours before the alert went out and 122 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: 215 J/kg
Mixed-layer CIN: -75 J/kg
Mixed-layer LCL: 636 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 123 m²/s²
0-3 km storm-relative helicity: 150 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 0.8

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 27, 1:23 PM EDT	Tornado Watch	SPC	Allegany, Anne Arundel, Baltimore, Calvert, Carroll, Charles and 8 more	5 hr
Apr 27, 1:24 PM EDT	Mesoscale Discussion	SPC	Allegany, Garrett	96 min
Apr 27, 3:10 PM EDT	Tornado Watch	SPC	Garrett	7 hr
Apr 27, 3:55 PM EDT	Mesoscale Discussion	SPC	Caroline, Cecil, Dorchester, Harford, Kent, Queen Anne's and 3 more	65 min
Apr 27, 4:39 PM EDT	Mesoscale Discussion	SPC	Allegany, Anne Arundel, Baltimore, Calvert, Carroll, Charles and 10 more	66 min
Apr 27, 6:15 PM EDT	Tornado Watch	SPC	Allegany, Anne Arundel, Baltimore, Calvert, Carroll, Charles and 8 more	6 hr
Apr 27, 6:50 PM EDT	Mesoscale Discussion	SPC	Carroll, Harford, Washington	55 min
Apr 27, 7:55 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Baltimore, Calvert, Carroll, Charles, Harford and 8 more	65 min
Apr 27, 8:34 AM EDT	Tornado Watch	SPC	Cherokee, Clay	4 hr
Apr 27, 11:27 AM EDT	Tornado Watch	SPC	Cherokee, Clay	6 hr
Apr 27, 12:39 PM EDT	Mesoscale Discussion	SPC	Cherokee	66 min
Apr 27, 12:51 PM EDT	Mesoscale Discussion	SPC	Alamance, Anson, Bertie, Bladen, Cabarrus, Caswell and 47 more	84 min
Apr 27, 2:03 PM EDT	Mesoscale Discussion	SPC	Cherokee, Clay, Graham	57 min
Apr 27, 3:22 PM EDT	Mesoscale Discussion	SPC	Alleghany, Ashe, Avery, Buncombe, Caldwell, Haywood and 6 more	83 min
Apr 27, 4:36 PM EDT	Tornado Watch PDS	SPC	Cherokee, Clay	8 hr
Apr 27, 6:41 PM EDT	Mesoscale Discussion	SPC	Alexander, Avery, Buncombe, Burke, Caldwell, Catawba and 16 more	34 min
Apr 27, 6:52 PM EDT	Tornado Watch PDS	SPC	Alexander, Avery, Buncombe, Burke, Caldwell, Catawba and 19 more	9 hr
Apr 27, 5:38 PM EDT	Mesoscale Discussion	SPC	Buchanan, Dickenson, Lee, Russell, Scott, Wise and 1 more	37 min
Apr 27, 5:44 PM EDT	Tornado Watch	SPC	Buchanan, Dickenson, Lee, Russell, Scott, Smyth and 5 more	7 hr

Nearby

Mesoscale Discussions in Virginia, 2011 Mesoscale Discussions in Maryland, 2011 Mesoscale Discussions in North Carolina, 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.