Alert archive / South Dakota / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 458
The Storm Prediction Center issued this severe thunderstorm watch at Aug 23, 2021, 5:20 PM CDT for 20 counties in South Dakota. It was in force for 8 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 23, 2021, 5:20 PM CDT (22:20 UTC)
- Expired
- Aug 24, 2021, 1:00 AM CDT
- In force
- 8 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 3 in
- Strongest gust expected
- 60 kt
Counties Aurora County, SD, Bon Homme County, SD, Brule County, SD, Buffalo County, SD, Charles Mix County, SD, Davison County, SD, Douglas County, SD, Gregory County, SD, Hanson County, SD, Hughes County, SD, Hutchinson County, SD, Jerauld County, SD, Jones County, SD, Lyman County, SD, Mellette County, SD, Miner County, SD, Sanborn County, SD, Stanley County, SD, Todd County, SD, Tripp County, SD
The radar
The Aberdeen radar (KABR), 202 km from the middle of the area, began a volume at 22:20 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
- 20%
- One or more EF2 to EF5 tornadoes
- 5%
- Ten or more severe wind reports
- 50%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 60%
- One or more hailstones of 2 inches or more
- 60%
- Six or more combined severe hail and wind reports
- 90%
Warnings issued inside it
2 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 23, 5:21 PM CDT | Severe Thunderstorm Warning | UNR | Todd | 29 min |
| Aug 23, 5:55 PM CDT | Severe Thunderstorm Warning | UNR | Mellette | 65 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, 10.3 hours before the alert went out and 153 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
- 2011 m above ground
- 0-6 km bulk shear
- 39 kt
- 0-1 km storm-relative helicity
- 31 m²/s²
- 0-3 km storm-relative helicity
- 21 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
651
WWUS20 KWNS 232218
SEL8
SPC WW 232218
SDZ000-240600-
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 458
NWS Storm Prediction Center Norman OK
520 PM CDT Mon Aug 23 2021
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Southcentral and southeast South Dakota
* Effective this Monday afternoon and Tuesday morning from 520 PM
until 100 AM CDT.
* Primary threats include...
Scattered large hail and isolated very large hail events to 3
inches in diameter likely
Scattered damaging wind gusts to 70 mph possible
A tornado or two possible
SUMMARY...Severe thunderstorms will develop and move east across the
watch area through this evening with a risk for very large hail and
damaging winds.
The severe thunderstorm watch area is approximately along and 40
statute miles north and south of a line from 90 miles west of
Chamberlain SD to 25 miles east of Mitchell SD. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU8).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for 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. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
AVIATION...A few severe thunderstorms with hail surface and aloft to
3 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
25025.
...BuntingSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 22, 8:40 PM CDT | Mesoscale Discussion | SPC | Aurora, Davison, Douglas, Hanson, Hutchinson, Jerauld and 2 more | 65 min |
| Aug 23, 2:56 PM CDT | Mesoscale Discussion | SPC | Aurora, Brule, Buffalo, Charles Mix, Gregory, Jones and 4 more | 2 hr |
Nearby
Severe Thunderstorm Watches in South Dakota, 2021Every severe thunderstorm 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.