Alert archive / Virginia / Mesoscale Discussions in 2017

Mesoscale Discussion 460

April 6, 201714 counties in North Carolina; 43 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Apr 6, 2017, 10:38 AM EDT for 14 counties in North Carolina; 43 counties in Virginia. It was in force for 67 min.

The area

The outline as issued.

The facts

Issued
Apr 6, 2017, 10:38 AM EDT (14:38 UTC)
Expired
Apr 6, 2017, 11:45 AM EDT
In force
67 min
Issued by
the Storm Prediction Center
All 57 counties

Bertie County, NC, Chowan County, NC, Edgecombe County, NC, Gates County, NC, Greene County, NC, Halifax County, NC, Hertford County, NC, Lenoir County, NC, Martin County, NC, Nash County, NC, Northampton County, NC, Pitt County, NC, Warren County, NC, Wilson County, NC, Amelia County, VA, Brunswick County, VA, Caroline County, VA, Charles City County, VA, Chesterfield 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 Richmond, VA, City of Suffolk, VA, City of Williamsburg, VA, Dinwiddie County, VA, Essex County, VA, Gloucester County, VA, Goochland 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, Mathews County, VA, Middlesex County, VA, New Kent County, VA, Northumberland County, VA, Nottoway County, VA, Powhatan County, VA, Prince George County, VA, Richmond County, VA, Southampton County, VA, Surry County, VA, Sussex County, VA, York County, VA

The radar

The Norfolk radar (KAKQ), 26 km from the middle of the area, began a volume at 14:39 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, 2.6 hours before the alert went out and 200 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-pSkew-T log-p diagram, Wallops Is Stn, VA at 12:00Z on 2017-04-06Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 61 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Wallops Is Stn, VA at 12:00Z on 2017-04-06The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -23 square meters per square second.1939587897117Sfc1 km3 km6 km9 kmRMLM
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
61 J/kg
Mixed-layer CIN
-145 J/kg
Mixed-layer LCL
1205 m above ground
0-6 km bulk shear
46 kt
0-1 km storm-relative helicity
-23 m²/s²
0-3 km storm-relative helicity
70 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.

IssuedProductOfficeCountiesLasted
Apr 5, 11:50 PM EDTSevere Thunderstorm WatchSPCAlexander, Cabarrus, Catawba, Cleveland, Davie, Gaston and 5 more6 hr
Apr 6, 12:51 AM EDTMesoscale DiscussionSPCAlamance, Anson, Caswell, Chatham, Davidson, Durham and 15 more114 min
Apr 6, 2:54 AM EDTMesoscale DiscussionSPCAlamance, Anson, Cabarrus, Davidson, Guilford, Montgomery and 4 more96 min
Apr 6, 5:59 AM EDTMesoscale DiscussionSPCAlamance, Bertie, Camden, Caswell, Chatham, Chowan and 32 more91 min
Apr 6, 7:06 AM EDTTornado WatchSPCAlamance, Bertie, Camden, Chatham, Chowan, Cumberland and 31 more8 hr
Apr 6, 12:18 PM EDTMesoscale DiscussionSPCArlington, Caroline, Charles City, Chesterfield, Essex, Fairfax and 28 more57 min
Apr 6, 12:45 PM EDTSevere Thunderstorm WatchSPCArlington, Culpeper, Fairfax, Fauquier, King George, Loudoun and 10 more4 hr

Nearby

Mesoscale Discussions in Virginia, 2017Mesoscale Discussions in North Carolina, 2017Every mesoscale discussion in 2017

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.