Alert archive / South Dakota / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 466
The Storm Prediction Center issued this severe thunderstorm watch at Aug 28, 2021, 2:32 AM CDT for Big Stone County, Traverse County, Minnesota; 16 counties in South Dakota. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 28, 2021, 2:32 AM CDT (07:32 UTC)
- Expired
- Aug 28, 2021, 7:08 AM CDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
Counties Big Stone County, MN, Traverse County, MN, Brown County, SD, Campbell County, SD, Clark County, SD, Codington County, SD, Corson County, SD, Day County, SD, Dewey County, SD, Edmunds County, SD, Faulk County, SD, Grant County, SD, Marshall County, SD, McPherson County, SD, Potter County, SD, Roberts County, SD, Spink County, SD, Walworth County, SD
The radar
The Aberdeen radar (KABR), 29 km from the middle of the area, began a volume at 07:35 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
- 5%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 20%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 40%
- One or more hailstones of 2 inches or more
- 30%
- Six or more combined severe hail and wind reports
- 60%
Warnings issued inside it
10 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 28, 2:39 AM CDT | Severe Thunderstorm Warning | ABR | Edmunds, Walworth | 66 min |
| Aug 28, 3:19 AM CDT | Severe Thunderstorm Warning | ABR | Brown, Edmunds, McPherson | 26 min |
| Aug 28, 3:42 AM CDT | Severe Thunderstorm Warning | ABR | Edmunds | 47 min |
| Aug 28, 4:12 AM CDT | Severe Thunderstorm Warning | ABR | Brown, Spink | 63 min |
| Aug 28, 4:51 AM CDT | Severe Thunderstorm Warning | ABR | Dewey | 39 min |
| Aug 28, 5:10 AM CDT | Severe Thunderstorm Warning | ABR | Brown, Clark, Codington, Day, Spink | 65 min |
| Aug 28, 6:08 AM CDT | Severe Thunderstorm Warning | ABR | Edmunds, Potter, Walworth | 37 min |
| Aug 28, 6:15 AM CDT | Severe Thunderstorm Warning | ABR | Codington, Day, Grant | 60 min |
| Aug 28, 6:55 AM CDT | Severe Thunderstorm Warning | ABR | Edmunds, Faulk | 35 min |
| Aug 28, 7:01 AM CDT | Severe Thunderstorm Warning | ABR | Grant | 44 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, 7.5 hours before the alert went out and 77 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
- 650 J/kg
- Mixed-layer CIN
- -128 J/kg
- Mixed-layer LCL
- 1212 m above ground
- 0-6 km bulk shear
- 54 kt
- 0-1 km storm-relative helicity
- 74 m²/s²
- 0-3 km storm-relative helicity
- 186 m²/s²
- Significant tornado parameter
- 0.2
- Supercell composite
- 4.1
The text
As transmitted.
232
WWUS20 KWNS 280729
SEL6
SPC WW 280729
MNZ000-SDZ000-281300-
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 466
NWS Storm Prediction Center Norman OK
230 AM CDT Sat Aug 28 2021
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Extreme west central Minnesota
North central and northeast South Dakota
* Effective this Saturday morning from 230 AM until 800 AM CDT.
* Primary threats include...
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Isolated damaging wind gusts to 70 mph possible
SUMMARY...Clusters of elevated supercells will likely persist
through the morning and spread eastward from north central toward
northeast South Dakota and adjacent west central Minnesota. Large
hail will be the primary threat, though isolated severe gusts could
still reach the ground with the elevated storms.
The severe thunderstorm watch area is approximately along and 35
statute miles north and south of a line from 95 miles west of
Aberdeen SD to 10 miles north northeast of Ortonville MN. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU6).
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
2 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
27035.
...ThompsonSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 27, 9:57 PM CDT | Mesoscale Discussion | SPC | Fillmore, Houston | 93 min |
| Aug 28, 2:17 AM CDT | Mesoscale Discussion | SPC | Big Stone, Stevens, Swift, Traverse | 2 hr |
| Aug 28, 5:42 AM CDT | Mesoscale Discussion | SPC | Benton, Big Stone, Chippewa, Douglas, Grant, Kandiyohi and 11 more | 2 hr |
| Aug 28, 7:08 AM CDT | Severe Thunderstorm Watch | SPC | Big Stone, Chippewa, Douglas, Grant, Kandiyohi, Lac qui Parle and 13 more | 5 hr |
| Aug 28, 9:39 AM CDT | Mesoscale Discussion | SPC | Anoka, Benton, Chisago, Douglas, Grant, Isanti and 12 more | 2 hr |
| Aug 28, 10:34 AM CDT | Tornado Watch | SPC | Aitkin, Anoka, Benton, Carlton, Carver, Chisago and 14 more | 4 hr |
| Aug 28, 1:13 PM CDT | Mesoscale Discussion | SPC | Anoka, Chisago, Isanti, Kanabec, Pine | 2 hr |
| Aug 28, 2:43 PM CDT | Mesoscale Discussion | SPC | Murray, Nobles, Pipestone, Rock | 3 hr |
| Aug 28, 3:44 PM CDT | Tornado Watch | SPC | Cottonwood, Jackson, Lincoln, Lyon, Murray, Nobles and 2 more | 5 hr |
| Aug 28, 3:57 PM CDT | Severe Thunderstorm Watch | SPC | Cottonwood, Jackson, Murray, Nobles, Rock | 7 hr |
| Aug 28, 5:27 PM CDT | Mesoscale Discussion | SPC | Blue Earth, Brown, Carver, Cottonwood, Dakota, Dodge and 22 more | 63 min |
| Aug 28, 5:59 PM CDT | Severe Thunderstorm Watch | SPC | Blue Earth, Brown, Carver, Faribault, Freeborn, Le Sueur and 11 more | 6 hr |
| Aug 28, 6:09 PM CDT | Mesoscale Discussion | SPC | Blue Earth, Brown, Cottonwood, Nicollet, Watonwan | 66 min |
Nearby
Severe Thunderstorm Watches in South Dakota, 2021Severe Thunderstorm Watches in Minnesota, 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.