Alert archive / Virginia / Mesoscale Discussions in 2021
Mesoscale Discussion 1311
The Storm Prediction Center issued this mesoscale discussion at Jul 17, 2021, 8:03 PM EDT for 29 counties in Virginia. It was in force for 87 min.
The area
The outline as issued.
The facts
- Issued
- Jul 17, 2021, 8:03 PM EDT (00:03 UTC)
- Expired
- Jul 17, 2021, 9:30 PM EDT
- In force
- 87 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
All 29 counties
Brunswick County, VA, Charles City 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 Suffolk, VA, City of Williamsburg, VA, Dinwiddie County, VA, Gloucester County, VA, Henrico County, VA, Isle of Wight County, VA, James City County, VA, King and Queen County, VA, King William County, VA, Mathews County, VA, Middlesex County, VA, New Kent County, VA, Prince George County, VA, Southampton County, VA, Surry County, VA, Sussex County, VA, York County, VA
The radar
The Norfolk radar (KAKQ), 21 km from the middle of the area, began a volume at 00:04 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 00:00Z, 0.1 hours before the alert went out and 161 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.
- Mixed-layer CAPE
- 1997 J/kg
- Mixed-layer CIN
- -29 J/kg
- Mixed-layer LCL
- 1118 m above ground
- 0-6 km bulk shear
- 18 kt
- 0-1 km storm-relative helicity
- 59 m²/s²
- 0-3 km storm-relative helicity
- 74 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
621
ACUS11 KWNS 180003
SWOMCD
SPC MCD 180003
VAZ000-180130-
Mesoscale Discussion 1311
NWS Storm Prediction Center Norman OK
0703 PM CDT Sat Jul 17 2021
Areas affected...portions of eastern and southeastern Virginia
Concerning...Severe potential...Watch unlikely
Valid 180003Z - 180130Z
Probability of Watch Issuance...20 percent
SUMMARY...A couple damaging gusts may accompany the stronger storms
over the next few hours. The overall severe threat is expected to be
relatively brief and isolated.
DISCUSSION...MRMS mosaic and KAKQ radar data show a somewhat
organized line of multicellular storms, with 35 dBZ echoes exceeding
45 kft, roughly from Middlesex to Dinwiddie County VA. These storms
are moving through an airmass characterized by 2000+ J/kg MLCAPE and
7 C/km sfc-3km lapse rates, supportive of occasional wet downbursts.
Nonetheless, with the onset of nocturnal cooling, the severe threat
is expected to only last for a few hours, and given limited area
ahead of the storms, overall severe coverage is expected to remain
localized/sparse.
..Squitieri/Guyer.. 07/18/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...AKQ...
LAT...LON 36797821 37657729 37827686 37757656 37487623 37167612
36877616 36697649 36677737 36797821Nearby
Mesoscale Discussions in Virginia, 2021Every 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.