Alert archive / Virginia / Mesoscale Discussions in 2020

Mesoscale Discussion 814

June 4, 20204 states

The Storm Prediction Center issued this mesoscale discussion at Jun 4, 2020, 2:02 PM EDT for 4 states. It was in force for 118 min.

The area

The outline as issued.

The facts

Issued: Jun 4, 2020, 2:02 PM EDT (18:02 UTC)
Expired: Jun 4, 2020, 4:00 PM EDT
In force: 118 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...severe thunderstorm watch likely
Chance of a watch: 80%

All 73 counties

Baltimore County, MD, Carroll County, MD, Charles County, MD, Frederick County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Washington County, MD, Adams County, PA, Cumberland County, PA, Franklin County, PA, Fulton County, PA, Perry County, PA, York County, PA, Albemarle County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Arlington County, VA, Augusta County, VA, Bedford County, VA, Buckingham County, VA, Campbell County, VA, Caroline County, VA, Chesterfield County, VA, City of Alexandria, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Harrisonburg, VA, City of Lexington, VA, City of Lynchburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Richmond, VA, City of Staunton, VA, City of Waynesboro, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Cumberland County, VA, Fairfax County, VA, Fauquier County, VA, Fluvanna County, VA, Frederick County, VA, Goochland County, VA, Greene County, VA, Hanover County, VA, King George County, VA, Loudoun County, VA, Louisa County, VA, Madison County, VA, Nelson County, VA, Nottoway County, VA, Orange County, VA, Page County, VA, Powhatan County, VA, Prince Edward County, VA, Prince William County, VA, Rappahannock County, VA, Rockbridge County, VA, Rockingham County, VA, Shenandoah County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Berkeley County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Morgan County, WV

The radar

The Sterling radar (KLWX), 51 km from the middle of the area, began a volume at 18:04 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 250Jun 4, 2:30 PM EDT

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 6.0 hours before the alert went out and 59 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: 139 J/kg
Mixed-layer CIN: -204 J/kg
Mixed-layer LCL: 1499 m above ground
0-6 km bulk shear: 41 kt
0-1 km storm-relative helicity: -64 m²/s²
0-3 km storm-relative helicity: 54 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 4, 2:29 PM EDT	Severe Thunderstorm Watch	SPC	Allegany, Anne Arundel, Baltimore, Carroll, Frederick, Harford and 5 more	8 hr
Jun 4, 4:41 PM EDT	Mesoscale Discussion	SPC	Allegany, Baltimore, Carroll, Frederick, Garrett, Howard and 3 more	94 min
Jun 4, 12:45 PM EDT	Mesoscale Discussion	SPC	Allegheny, Armstrong, Beaver, Butler, Clarion, Fayette and 5 more	90 min
Jun 4, 12:55 PM EDT	Severe Thunderstorm Watch	SPC	Allegheny, Armstrong, Beaver, Butler, Clarion, Fayette and 6 more	6 hr
Jun 4, 2:14 PM EDT	Mesoscale Discussion	SPC	Beaver, Lawrence, Washington	61 min
Jun 4, 4:00 PM EDT	Mesoscale Discussion	SPC	Allegheny, Armstrong, Beaver, Butler, Clarion, Greene and 4 more	90 min
Jun 4, 6:44 PM EDT	Mesoscale Discussion	SPC	Adams, Bedford, Berks, Blair, Centre, Chester and 19 more	91 min

Nearby

Mesoscale Discussions in Virginia, 2020 Mesoscale Discussions in Maryland, 2020 Mesoscale Discussions in Pennsylvania, 2020 Every mesoscale discussion in 2020

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.