Alert archive / Virginia / Mesoscale Discussions in 2021

Mesoscale Discussion 1713

September 8, 202112 counties in North Carolina; 39 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Sep 8, 2021, 1:16 PM EDT for 12 counties in North Carolina; 39 counties in Virginia. It was in force for 89 min.

The area

The outline as issued.

The facts

Issued: Sep 8, 2021, 1:16 PM EDT (17:16 UTC)
Expired: Sep 8, 2021, 2:45 PM EDT
In force: 89 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

All 51 counties

Bertie County, NC, Camden County, NC, Chowan County, NC, Edgecombe County, NC, Gates County, NC, Hertford County, NC, Martin County, NC, Northampton County, NC, Pasquotank County, NC, Perquimans County, NC, Pitt County, NC, Washington County, NC, 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 Virginia Beach, VA, City of Williamsburg, VA, Dinwiddie County, VA, Essex 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, Mathews County, VA, Middlesex County, VA, New Kent County, VA, Northumberland 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), 38 km from the middle of the area, began a volume at 17:19 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, 5.3 hours before the alert went out and 204 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: 145 J/kg
Mixed-layer CIN: -150 J/kg
Mixed-layer LCL: 1075 m above ground
0-6 km bulk shear: 17 kt
0-1 km storm-relative helicity: 47 m²/s²
0-3 km storm-relative helicity: 90 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

629 
ACUS11 KWNS 081716
SWOMCD
SPC MCD 081716 
NCZ000-VAZ000-081845-

Mesoscale Discussion 1713
NWS Storm Prediction Center Norman OK
1216 PM CDT Wed Sep 08 2021

Areas affected...Southeast VA and northeast NC

Concerning...Severe potential...Watch unlikely 

Valid 081716Z - 081845Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated wind damage and hail near 1 inch diameter will be
possible this afternoon from southeast Virginia into northeast North
Carolina, but a watch is unlikely.

DISCUSSION...A remnant MCV is moving east-northeastward near the
NC/VA border as of 17z.  Temperatures have warmed into the mid-upper
80s with dewpoints in the low 70s ahead of the MCV, which is
contributing to MLCAPE of 1500-2500 J/kg.  Downdraft potential
appears to be greater into southeast VA as evidenced by DCAPE over
1000 J/kg, while there is a narrow zone of somewhat enhanced
midlevel flow and vertical shear farther south into north
central/northeast NC on the eastern periphery of the MCV.  Isolated
wind damage will be possible across southeast VA with storm clusters
preceding the MCV, and there will be some potential for marginal
supercells in the zone of 30+ kt effective bulk shear across
northeast NC.  The overall severe threat is expected to remain
rather marginal/isolated, and a watch is not anticipated.

..Thompson/Hart.. 09/08/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...AKQ...MHX...RAH...

LAT...LON   36647594 36227604 35927633 35567682 35457731 35657766
            35917775 36387754 36897759 37117786 37527797 37907776
            38067708 37857622 36647594

Nearby

Mesoscale Discussions in Virginia, 2021 Mesoscale Discussions in North Carolina, 2021 Every mesoscale discussion in 2021

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.