Alert archive / Virginia / Mesoscale Discussions in 2021
Mesoscale Discussion 1665
The Storm Prediction Center issued this mesoscale discussion at Aug 31, 2021, 11:01 PM EDT for 21 counties in Virginia. It was in force for 89 min.
The area
The outline as issued.
The facts
- Issued
- Aug 31, 2021, 11:01 PM EDT (03:01 UTC)
- Expired
- Sep 1, 2021, 12:30 AM EDT
- In force
- 89 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 480
All 21 counties
Albemarle County, VA, Amherst County, VA, Augusta County, VA, Bath County, VA, Botetourt County, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Harrisonburg, VA, City of Lexington, VA, City of Lynchburg, VA, City of Staunton, VA, City of Waynesboro, VA, Culpeper County, VA, Fluvanna County, VA, Greene County, VA, Madison County, VA, Nelson County, VA, Orange County, VA, Page County, VA, Rockbridge County, VA, Rockingham County, VA
The radar
The Sterling radar (KLWX), 160 km from the middle of the area, began a volume at 02:59 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 00:00Z, 3.0 hours before the alert went out and 106 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
- 319 J/kg
- Mixed-layer CIN
- -23 J/kg
- Mixed-layer LCL
- 782 m above ground
- 0-6 km bulk shear
- 34 kt
- 0-1 km storm-relative helicity
- 122 m²/s²
- 0-3 km storm-relative helicity
- 133 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 1.9
The text
As transmitted.
610
ACUS11 KWNS 010302
SWOMCD
SPC MCD 010301
VAZ000-010430-
Mesoscale Discussion 1665
NWS Storm Prediction Center Norman OK
1001 PM CDT Tue Aug 31 2021
Areas affected...portions of western VA
Concerning...Tornado Watch 480...
Valid 010301Z - 010430Z
The severe weather threat for Tornado Watch 480 continues.
SUMMARY...A threat for brief tornadoes continues across Tornado
Watch 480.
DISCUSSION...Several cells near Rockbridge to Albemarle counties in
western/central VA have intensified over the past hour or so. These
cells continue to exhibit periods of weak low-level rotation as they
shift north/northeast. This activity is occurring in the vicinity of
a surface boundary draped across the region and within a corridor of
stronger low-level instability (0-3 km MLCAPE around 100-125 m2/s2).
Low-level shear is somewhat less favorable with northeast extent
compared to earlier this evening, but still sufficient to support
rotating cells capable of brief tornadoes.
..Leitman.. 09/01/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...AKQ...LWX...RNK...
LAT...LON 37997799 37647840 37437884 37367933 37407970 37617989
37987986 38277956 38557894 38697835 38587796 38347787
37997799SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 1, 12:19 AM EDT | Mesoscale Discussion | SPC | Arlington, Culpeper, Fairfax, Fauquier, King George, Loudoun and 8 more | 86 min |
| Sep 1, 12:56 AM EDT | Tornado Watch | SPC | Arlington, Fairfax, Fauquier, Loudoun, Prince William, Stafford and 6 more | 6 hr |
| Sep 1, 11:03 AM EDT | Mesoscale Discussion | SPC | Accomack, Arlington, Caroline, Charles City, Clarke, Culpeper and 32 more | 2 hr |
| Sep 1, 11:46 AM EDT | Tornado Watch | SPC | Accomack, Amelia, Arlington, Caroline, Charles City, Chesterfield and 57 more | 9 hr |
| Sep 1, 1:32 PM EDT | Mesoscale Discussion | SPC | Arlington, Essex, King George, Richmond, Westmoreland, City of Alexandria and 1 more | 118 min |
Nearby
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.