Alert archive / Virginia / Mesoscale Discussions in 2004

Mesoscale Discussion 793

May 21, 200410 counties in Maryland; 35 counties in Virginia; Jefferson County, West Virginia

The Storm Prediction Center issued this mesoscale discussion at May 21, 2004, 8:34 AM EDT for 10 counties in Maryland; 35 counties in Virginia; Jefferson County, West Virginia. It was in force for 86 min.

The area

The outline as issued.

The facts

Issued: May 21, 2004, 8:34 AM EDT (12:34 UTC)
Expired: May 21, 2004, 10:00 AM EDT
In force: 86 min
Issued by: the Storm Prediction Center

All 46 counties

Anne Arundel County, MD, Baltimore County, MD, Carroll County, MD, Charles County, MD, City of Baltimore, MD, Frederick County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Washington County, MD, Albemarle County, VA, Arlington County, VA, Caroline County, VA, City of Alexandria, VA, City of Charlottesville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Harrisonburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Staunton, VA, City of Waynesboro, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Fluvanna County, VA, Frederick County, VA, Greene County, VA, Hanover County, VA, King George County, VA, Loudoun County, VA, Louisa County, VA, Madison County, VA, Orange County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Rockingham County, VA, Shenandoah County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Jefferson County, WV

The radar

The Sterling radar (KLWX), 52 km from the middle of the area, began a volume at 12:35 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 nearest sounding before it

Roanoke, VA (KRNK), launched 12:00Z, 0.6 hours before the alert went out and 213 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: 532 J/kg
Mixed-layer CIN: -66 J/kg
Mixed-layer LCL: 845 m above ground
0-6 km bulk shear: 8 kt
0-1 km storm-relative helicity: -50 m²/s²
0-3 km storm-relative helicity: 11 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

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
May 21, 12:28 PM EDT	Mesoscale Discussion	SPC	Charles, Saint Mary's	2 hr
May 21, 5:31 PM EDT	Mesoscale Discussion	SPC	Allegany, Frederick, Garrett, Washington	89 min
May 21, 6:35 PM EDT	Severe Thunderstorm Watch	SPC	Allegany, Carroll, Charles, Frederick, Garrett, Howard and 3 more	4 hr
May 21, 1:00 PM EDT	Severe Thunderstorm Watch	SPC	Accomack, Albemarle, Amelia, Amherst, Appomattox, Augusta and 68 more	7 hr
May 21, 4:30 PM EDT	Mesoscale Discussion	SPC	Amelia, Brunswick, Charles City, Charlotte, Chesterfield, Cumberland and 38 more	2 hr
May 21, 2:40 AM EDT	Mesoscale Discussion	SPC	Hancock	65 min
May 21, 4:45 AM EDT	Mesoscale Discussion	SPC	Brooke, Hancock, Marshall, Ohio, Wetzel	60 min
May 21, 2:19 PM EDT	Mesoscale Discussion	SPC	Hancock	116 min
May 21, 3:15 PM EDT	Severe Thunderstorm Watch	SPC	Brooke, Hancock, Ohio	6 hr

Nearby

Mesoscale Discussions in Virginia, 2004 Mesoscale Discussions in Maryland, 2004 Mesoscale Discussions in West Virginia, 2004 Every mesoscale discussion in 2004

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.