Alert archive / Virginia / Mesoscale Discussions in 2020

Mesoscale Discussion 381

April 13, 20206 states

The Storm Prediction Center issued this mesoscale discussion at Apr 13, 2020, 10:34 AM EDT for 6 states. It was in force for 86 min.

The area

The outline as issued.

The facts

Issued: Apr 13, 2020, 10:34 AM EDT (14:34 UTC)
Expired: Apr 13, 2020, 12:00 PM EDT
In force: 86 min
Issued by: the Storm Prediction Center
Chance of a watch: 80%

All 80 counties

New Castle County, DE, Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Carroll County, MD, Cecil 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, Talbot County, MD, Washington County, MD, Salem County, NJ, Adams County, PA, Berks County, PA, Bucks County, PA, Chester County, PA, Cumberland County, PA, Dauphin County, PA, Delaware County, PA, Franklin County, PA, Fulton County, PA, Juniata County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Mifflin County, PA, Montgomery County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Philadelphia County, PA, Schuylkill County, PA, Snyder County, PA, Union County, PA, York County, PA, 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 Manassas, VA, City of Manassas Park, VA, City of Richmond, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Essex County, VA, Fairfax County, VA, Fauquier 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, Orange County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Shenandoah County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Westmoreland County, VA, Berkeley County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Morgan County, WV

The radar

The Sterling radar (KLWX), 64 km from the middle of the area, began a volume at 14:34 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 119Apr 13, 11:30 AM EDT

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 2.6 hours before the alert went out and 65 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 712 m above ground
0-6 km bulk shear: 75 kt
0-1 km storm-relative helicity: 487 m²/s²
0-3 km storm-relative helicity: 684 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
Apr 13, 11:33 AM EDT	Tornado Watch	SPC	Kent, New Castle, Sussex	5 hr
Apr 13, 1:20 PM EDT	Mesoscale Discussion	SPC	Kent, New Castle, Sussex	85 min
Apr 13, 3:03 PM EDT	Mesoscale Discussion	SPC	Kent, New Castle	87 min
Apr 13, 6:46 AM EDT	Mesoscale Discussion	SPC	Somerset	89 min
Apr 13, 2:42 PM EDT	Mesoscale Discussion	SPC	Bergen, Passaic, Sussex	93 min
Apr 13, 4:40 AM EDT	Mesoscale Discussion	SPC	Amelia, Brunswick, Buckingham, Charles City, Charlotte, Chesterfield and 42 more	95 min
Apr 13, 5:01 AM EDT	Tornado Watch	SPC	Amelia, Appomattox, Brunswick, Buckingham, Campbell, Charles City and 36 more	7 hr

Nearby

Mesoscale Discussions in Virginia, 2020 Mesoscale Discussions in Pennsylvania, 2020 Mesoscale Discussions in Maryland, 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.