Alert archive / Virginia / Mesoscale Discussions in 2016

Mesoscale Discussion 1420

July 28, 201642 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Jul 28, 2016, 2:57 PM EDT for 42 counties in Virginia. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Jul 28, 2016, 2:57 PM EDT (18:57 UTC)
Expired: Jul 28, 2016, 5:30 PM EDT
In force: 3 hr
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 42 counties

Accomack County, VA, Amelia County, VA, Brunswick County, VA, Charles City County, VA, Chesterfield County, 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 Richmond, VA, City of Suffolk, VA, City of Virginia Beach, VA, City of Williamsburg, VA, Dinwiddie County, VA, Gloucester County, VA, Greensville County, VA, Hanover 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, Lunenburg County, VA, Mathews County, VA, Mecklenburg County, VA, Middlesex County, VA, New Kent County, VA, Northampton County, VA, Northumberland County, VA, Nottoway County, VA, Prince George County, VA, Southampton County, VA, Surry County, VA, Sussex County, VA, York County, VA

The radar

The Norfolk radar (KAKQ), 24 km from the middle of the area, began a volume at 18:56 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, 7.0 hours before the alert went out and 163 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: 1169 J/kg
Mixed-layer CIN: -50 J/kg
Mixed-layer LCL: 1097 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 24 m²/s²
0-3 km storm-relative helicity: 90 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 3.0

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
Jul 28, 12:58 PM EDT	Mesoscale Discussion	SPC	Albemarle, Arlington, Caroline, Clarke, Culpeper, Essex and 35 more	2 hr
Jul 28, 1:27 PM EDT	Severe Thunderstorm Watch	SPC	Albemarle, Arlington, Augusta, Clarke, Culpeper, Fairfax and 28 more	11 hr
Jul 28, 1:28 PM EDT	Mesoscale Discussion	SPC	Alleghany, Bedford, Bland, Botetourt, Craig, Floyd and 12 more	3 hr
Jul 28, 2:08 PM EDT	Severe Thunderstorm Watch	SPC	Alleghany, Amherst, Appomattox, Bath, Bedford, Bland and 29 more	10 hr
Jul 28, 4:10 PM EDT	Mesoscale Discussion	SPC	Albemarle, Alleghany, Amherst, Arlington, Augusta, Bath and 50 more	95 min
Jul 28, 6:52 PM EDT	Mesoscale Discussion	SPC	Albemarle, Alleghany, Amherst, Appomattox, Arlington, Augusta and 63 more	83 min

Nearby

Mesoscale Discussions in Virginia, 2016 Every mesoscale discussion in 2016

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.