Alert archive / Virginia / Mesoscale Discussions in 2021
Mesoscale Discussion 720
The Storm Prediction Center issued this mesoscale discussion at May 24, 2021, 1:57 PM EDT for 9 counties in North Carolina; 29 counties in Virginia; Pendleton County, West Virginia. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 24, 2021, 1:57 PM EDT (17:57 UTC)
- Expired
- May 24, 2021, 4:00 PM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
All 39 counties
Caswell County, NC, Durham County, NC, Franklin County, NC, Granville County, NC, Orange County, NC, Person County, NC, Vance County, NC, Wake County, NC, Warren County, NC, Albemarle County, VA, Amherst County, VA, Appomattox County, VA, Augusta County, VA, Bedford County, VA, Buckingham County, VA, Campbell County, VA, Charlotte County, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Danville, VA, City of Harrisonburg, VA, City of Lexington, VA, City of Lynchburg, VA, City of Staunton, VA, City of Waynesboro, VA, Cumberland County, VA, Fluvanna County, VA, Greene County, VA, Halifax County, VA, Highland County, VA, Lunenburg County, VA, Mecklenburg County, VA, Nelson County, VA, Nottoway County, VA, Pittsylvania County, VA, Prince Edward County, VA, Rockbridge County, VA, Rockingham County, VA, Pendleton County, WV
The radar
The Roanoke radar (KFCX), 129 km from the middle of the area, began a volume at 17:57 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
Roanoke, VA (KRNK), launched 12:00Z, 6.0 hours before the alert went out and 58 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
- 3 J/kg
- Mixed-layer CIN
- -105 J/kg
- Mixed-layer LCL
- 1348 m above ground
- 0-6 km bulk shear
- 22 kt
- 0-1 km storm-relative helicity
- 0 m²/s²
- 0-3 km storm-relative helicity
- 48 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
465
ACUS11 KWNS 241757
SWOMCD
SPC MCD 241757
VAZ000-NCZ000-WVZ000-242000-
Mesoscale Discussion 0720
NWS Storm Prediction Center Norman OK
1257 PM CDT Mon May 24 2021
Areas affected...portions of extreme eastern WV...central/southern
VA and north-central NC
Concerning...Severe potential...Watch unlikely
Valid 241757Z - 242000Z
Probability of Watch Issuance...20 percent
SUMMARY...A few thunderstorms are expected to develop this afternoon
and move southeast through early evening. A couple of storms may
produce strong/possibly damaging wind gusts. A watch is not
anticipated given the expected sparse coverage of the severe risk,
however trends in storm coverage will be monitored.
DISCUSSION...A west/southwest moving back door cold front extended
from a weak surface low over southwest PA southward across
central/southern VA and eastern NC at 17z. Despite mid/high-level
clouds, temperatures to the west of the front have warmed into the
80s over southern VA/northern NC. Although mid-level lapse rates
are poor, the presence of surface dew points generally in the mid
60s will contribute to MLCAPE of 500-750 J/kg. Widely scattered
thunderstorms are expected to develop during the early/mid afternoon
time frame over the higher terrain, with storms subsequently moving
southeast in the vicinity of the front. Modest northwesterly
mid-level flow will contribute to 25-30 kts of deep-layer shear in
the vicinity of the front, supporting some degree of storm
organization. Steep low-level lapse rates and an appreciable
sub-cloud temperature-dew point spread will result in a risk for
strong/possibly damaging winds with a couple of stronger storms.
The overall severe risk should remain isolated and a watch is not
expected, however convective trends will be monitored.
..Bunting/Guyer.. 05/24/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...AKQ...LWX...RAH...RNK...
LAT...LON 36307799 35767842 35727915 36657959 37437971 38007965
38397958 38687948 38837910 38757872 38417835 37427807
36307799Nearby
Mesoscale Discussions in Virginia, 2021Mesoscale Discussions in North Carolina, 2021Mesoscale Discussions in West 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.