Alert archive / Virginia / Mesoscale Discussions in 2018

Mesoscale Discussion 221

April 4, 20184 states

The Storm Prediction Center issued this mesoscale discussion at Apr 4, 2018, 1:27 PM EDT for 4 states. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Apr 4, 2018, 1:27 PM EDT (17:27 UTC)
Expired: Apr 4, 2018, 4:00 PM EDT
In force: 3 hr
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 74 counties

Kent County, DE, Sussex County, DE, Calvert County, MD, Caroline County, MD, Dorchester County, MD, Saint Mary's County, MD, Somerset County, MD, Talbot County, MD, Wicomico County, MD, Worcester County, MD, Beaufort County, NC, Bertie County, NC, Camden County, NC, Chowan County, NC, Currituck County, NC, Dare County, NC, Edgecombe County, NC, Franklin County, NC, Gates County, NC, Greene County, NC, Halifax County, NC, Hertford County, NC, Hyde County, NC, Johnston County, NC, Lenoir County, NC, Martin County, NC, Nash County, NC, Northampton County, NC, Pasquotank County, NC, Perquimans County, NC, Pitt County, NC, Tyrrell County, NC, Warren County, NC, Washington County, NC, Wayne County, NC, Wilson County, NC, Accomack County, VA, Charles City County, VA, City of Chesapeake, VA, City of Colonial Heights, VA, City of Emporia, VA, City of Franklin, VA, City of Hampton, VA, City of Hopewell, VA, City of Newport News, VA, City of Norfolk, VA, City of Petersburg, VA, City of Poquoson, VA, City of Portsmouth, VA, City of Suffolk, VA, City of Virginia Beach, VA, City of Williamsburg, VA, Dinwiddie County, VA, Essex County, VA, Gloucester County, VA, Greensville County, VA, Henrico County, VA, Isle of Wight County, VA, James City County, VA, King and Queen County, VA, King William County, VA, Lancaster County, VA, Mathews County, VA, Middlesex County, VA, New Kent County, VA, Northampton County, VA, Northumberland County, VA, Prince George County, VA, Richmond County, VA, Southampton County, VA, Surry County, VA, Sussex County, VA, Westmoreland County, VA, York County, VA

The radar

The Norfolk radar (KAKQ), 58 km from the middle of the area, began a volume at 17:31 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

Wallops Is Stn, VA (KWAL), launched 12:00Z, 5.5 hours before the alert went out and 128 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: 117 J/kg
Mixed-layer CIN: -288 J/kg
Mixed-layer LCL: 959 m above ground
0-6 km bulk shear: 46 kt
0-1 km storm-relative helicity: 287 m²/s²
0-3 km storm-relative helicity: 257 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 4, 2:00 AM EDT	Mesoscale Discussion	SPC	Buncombe, Cherokee, Clay, Graham, Haywood, Jackson and 5 more	105 min
Apr 3, 9:16 PM EDT	Mesoscale Discussion	SPC	Buchanan, Dickenson, Lee, Russell, Scott, Tazewell and 3 more	89 min
Apr 3, 9:50 PM EDT	Severe Thunderstorm Watch	SPC	Buchanan, Dickenson, Lee, Scott, Wise, City of Norton	5 hr
Apr 3, 11:49 PM EDT	Mesoscale Discussion	SPC	Buchanan, Dickenson, Lee, Russell, Scott, Wise and 1 more	86 min

Nearby

Mesoscale Discussions in Virginia, 2018 Mesoscale Discussions in North Carolina, 2018 Mesoscale Discussions in Maryland, 2018 Every mesoscale discussion in 2018

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.