Alert archive / South Dakota / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 459
The Storm Prediction Center issued this severe thunderstorm watch at Aug 23, 2021, 10:11 PM CDT for 9 counties in North Dakota; 21 counties in South Dakota. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 23, 2021, 10:11 PM CDT (03:11 UTC)
- Expired
- Aug 24, 2021, 3:00 AM CDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 30 counties
Dickey County, ND, Emmons County, ND, LaMoure County, ND, Logan County, ND, McIntosh County, ND, Ransom County, ND, Richland County, ND, Sargent County, ND, Sioux County, ND, Brown County, SD, Campbell County, SD, Clark County, SD, Codington County, SD, Corson County, SD, Day County, SD, Deuel County, SD, Dewey County, SD, Edmunds County, SD, Faulk County, SD, Grant County, SD, Hamlin County, SD, Hand County, SD, Hyde County, SD, Marshall County, SD, McPherson County, SD, Potter County, SD, Roberts County, SD, Spink County, SD, Sully County, SD, Walworth County, SD
The radar
The Aberdeen radar (KABR), 70 km from the middle of the area, began a volume at 03:13 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
- 10%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 10%
- 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
9 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 23, 10:17 PM CDT | Severe Thunderstorm Warning | ABR | Dewey, Potter, Walworth | 43 min |
| Aug 23, 10:56 PM CDT | Severe Thunderstorm Warning | ABR | Dewey, Potter, Walworth | 64 min |
| Aug 23, 11:51 PM CDT | Severe Thunderstorm Warning | ABR | Faulk, Potter | 54 min |
| Aug 24, 12:01 AM CDT | Severe Thunderstorm Warning | ABR | Brown, Edmunds, McPherson | 59 min |
| Aug 24, 12:45 AM CDT | Severe Thunderstorm Warning | BIS | Dickey | 30 min |
| Aug 24, 12:56 AM CDT | Severe Thunderstorm Warning | ABR | Brown, Day, Marshall | 64 min |
| Aug 24, 1:05 AM CDT | Severe Thunderstorm Warning | ABR | Brown, Edmunds, Faulk, Hand, Spink | 55 min |
| Aug 24, 1:12 AM CDT | Severe Thunderstorm Warning | FGF | Richland, Sargent | 63 min |
| Aug 24, 2:14 AM CDT | Severe Thunderstorm Warning | FGF | Ransom, Richland, Sargent | 46 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 00:00Z, 3.2 hours before the alert went out and 113 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
- 142 J/kg
- Mixed-layer CIN
- -222 J/kg
- Mixed-layer LCL
- 2124 m above ground
- 0-6 km bulk shear
- 46 kt
- 0-1 km storm-relative helicity
- 173 m²/s²
- 0-3 km storm-relative helicity
- 342 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.1
The text
As transmitted.
385 WWUS20 KWNS 240308 SEL9 SPC WW 240308 NDZ000-SDZ000-240800- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 459 NWS Storm Prediction Center Norman OK 1010 PM CDT Mon Aug 23 2021 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Southeast North Dakota Northcentral and northeast South Dakota * Effective this Monday night and Tuesday morning from 1010 PM until 300 AM CDT. * Primary threats include... Isolated very large hail events to 2 inches in diameter possible Isolated damaging wind gusts to 70 mph possible SUMMARY...Thunderstorms will move east through the early morning hours and pose a threat for large hail and damaging wind gusts. The severe thunderstorm watch area is approximately along and 60 statute miles north and south of a line from 20 miles west northwest of Mobridge SD to 40 miles north northeast of Watertown SD. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU9). 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. && OTHER WATCH INFORMATION...CONTINUE...WW 458... AVIATION...A few severe thunderstorms with hail surface and aloft to 2 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 25030. ...Bunting
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 23, 7:38 PM CDT | Mesoscale Discussion | SPC | Emmons, Grant, Logan, McIntosh, Sioux | 2 hr |
| Aug 23, 9:37 PM CDT | Mesoscale Discussion | SPC | Sioux | 113 min |
| Aug 23, 11:32 PM CDT | Mesoscale Discussion | SPC | Dickey, Emmons, McIntosh, Richland, Sargent | 118 min |
Nearby
Severe Thunderstorm Watches in South Dakota, 2021Severe Thunderstorm Watches in North 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.