Alert archive / South Dakota / Tornado Watches in 2021
Tornado Watch 457
The Storm Prediction Center issued this tornado watch at Aug 22, 2021, 6:31 PM CDT for 10 counties in South Dakota. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 22, 2021, 6:31 PM CDT (23:31 UTC)
- Expired
- Aug 22, 2021, 9:29 PM CDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2.5 in
- Strongest gust expected
- 65 kt
Counties Aurora County, SD, Davison County, SD, Douglas County, SD, Hanson County, SD, Hutchinson County, SD, Jerauld County, SD, McCook County, SD, Miner County, SD, Sanborn County, SD, Turner County, SD
The radar
The Sioux Falls radar (KFSD), 99 km from the middle of the area, began a volume at 23:32 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.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 30%
- One or more EF2 to EF5 tornadoes
- 20%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 30%
- Ten or more severe hail reports
- 30%
- One or more hailstones of 2 inches or more
- 30%
- Six or more combined severe hail and wind reports
- 60%
Warnings issued inside it
6 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 22, 6:47 PM CDT | Tornado Warning | FSD | Aurora, Davison, Sanborn | 32 min |
| Aug 22, 7:15 PM CDT | Severe Thunderstorm Warning | FSD | Davison, Hanson, Miner, Sanborn | 30 min |
| Aug 22, 7:21 PM CDT | Severe Thunderstorm Warning | FSD | Aurora | 24 min |
| Aug 22, 7:31 PM CDT | Severe Thunderstorm Warning | FSD | Davison, Sanborn | 44 min |
| Aug 22, 8:06 PM CDT | Severe Thunderstorm Warning | FSD | Davison, Hanson, Miner, Sanborn | 39 min |
| Aug 22, 8:32 PM CDT | Severe Thunderstorm Warning | FSD | Hanson, McCook | 43 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Aberdeen, SD (KABR), launched 12:00Z, 11.5 hours before the alert went out and 129 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1388 m above ground
- 0-6 km bulk shear
- 33 kt
- 0-1 km storm-relative helicity
- 135 m²/s²
- 0-3 km storm-relative helicity
- 261 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
013
WWUS20 KWNS 222328
SEL7
SPC WW 222328
SDZ000-230300-
URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 457
NWS Storm Prediction Center Norman OK
630 PM CDT Sun Aug 22 2021
The NWS Storm Prediction Center has issued a
* Tornado Watch for portions of
Southeast South Dakota
* Effective this Sunday evening from 630 PM until 1000 PM CDT.
* Primary threats include...
A couple tornadoes possible
Isolated significant damaging wind gusts to 75 mph possible
Isolated very large hail events to 2.5 inches in diameter
possible
SUMMARY...A lone discrete supercell may persist for the next few
hours across southeast South Dakota.
The tornado watch area is approximately along and 30 statute miles
east and west of a line from 30 miles north northwest of Mitchell SD
to 40 miles south southeast of Mitchell SD. For a complete depiction
of the watch see the associated watch outline update (WOUS64 KWNS
WOU7).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and severe thunderstorms in and close to the watch
area. Persons in these areas should be on the lookout for
threatening weather conditions and listen for later statements
and possible warnings.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 455...WW 456...
AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 2.5 inches. Extreme turbulence and surface wind
gusts to 65 knots. A few cumulonimbi with maximum tops to 550. Mean
storm motion vector 29020.
...GramsSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 22, 2:21 PM CDT | Mesoscale Discussion | SPC | Beadle, Brown, Buffalo, Campbell, Edmunds, Faulk and 8 more | 2 hr |
| Aug 22, 3:36 PM CDT | Severe Thunderstorm Watch | SPC | Aurora, Beadle, Brookings, Brown, Brule, Buffalo and 24 more | 5 hr |
| Aug 22, 3:38 PM CDT | Mesoscale Discussion | SPC | Gregory, Tripp | 97 min |
| Aug 22, 5:59 PM CDT | Mesoscale Discussion | SPC | Beadle, Brookings, Brown, Campbell, Clark, Codington and 11 more | 91 min |
Nearby
Tornado Watches in South Dakota, 2021Every tornado watch 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.