Alert archive / Minnesota / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 471
The Storm Prediction Center issued this severe thunderstorm watch at Aug 28, 2021, 5:59 PM CDT for 17 counties in Minnesota. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 28, 2021, 5:59 PM CDT (22:59 UTC)
- Expired
- Aug 29, 2021, 12:00 AM CDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 75 kt
Counties Blue Earth County, MN, Brown County, MN, Carver County, MN, Faribault County, MN, Freeborn County, MN, Le Sueur County, MN, Martin County, MN, McLeod County, MN, Nicollet County, MN, Redwood County, MN, Renville County, MN, Rice County, MN, Scott County, MN, Sibley County, MN, Steele County, MN, Waseca County, MN, Watonwan County, MN
The radar
The Minneapolis radar (KMPX), 87 km from the middle of the area, began a volume at 23:00 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
- 20%
- Ten or more severe wind reports
- 80%
- One or more gusts of 65 knots or more
- 50%
- Ten or more severe hail reports
- 40%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 95%
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 28, 6:06 PM CDT | Severe Thunderstorm Warning | MPX | Brown, Redwood, Watonwan | 54 min |
| Aug 28, 6:19 PM CDT | Tornado Warning | MPX | Brown, Redwood | 26 min |
| Aug 28, 6:26 PM CDT | Severe Thunderstorm Warning | MPX | Blue Earth, Faribault, Martin, Watonwan | 64 min |
| Aug 28, 6:43 PM CDT | Severe Thunderstorm Warning | MPX | Blue Earth, Brown, Nicollet, Redwood, Renville, Sibley and 1 more | 62 min |
| Aug 28, 6:51 PM CDT | Tornado Warning | MPX | Brown, Nicollet | 24 min |
| Aug 28, 7:13 PM CDT | Severe Thunderstorm Warning | MPX | Blue Earth, Le Sueur, Nicollet, Rice, Sibley | 32 min |
| Aug 28, 7:40 PM CDT | Severe Thunderstorm Warning | MPX | Brown, Redwood | 23 min |
| Aug 28, 9:02 PM CDT | Flash Flood Warning | MPX | Redwood | 6 hr |
| Aug 28, 10:15 PM CDT | Tornado Warning | MPX | Brown | 30 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
Minneapolis, MN (KMPX), launched 12:00Z, 11.0 hours before the alert went out and 85 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
- 1550 J/kg
- Mixed-layer CIN
- -130 J/kg
- Mixed-layer LCL
- 676 m above ground
- 0-6 km bulk shear
- 29 kt
- 0-1 km storm-relative helicity
- 139 m²/s²
- 0-3 km storm-relative helicity
- 193 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 2.3
The text
As transmitted.
953
WWUS20 KWNS 282255
SEL1
SPC WW 282255
MNZ000-290400-
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 471
NWS Storm Prediction Center Norman OK
555 PM CDT Sat Aug 28 2021
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Southern Minnesota
* Effective this Saturday afternoon and evening from 555 PM until
1100 PM CDT.
* Primary threats include...
Widespread damaging winds likely with isolated significant gusts
to 85 mph possible
Scattered large hail events to 1.5 inches in diameter possible
A tornado or two possible
SUMMARY...A well-organized and fast east/northeastward-moving
cluster of storms will pose a severe risk as it progresses across
southern Minnesota through early/mid-evening. Potentially
widespread/intense damaging winds are the primary hazard along with
some potential for isolated large hail and/or a brief tornado risk.
The severe thunderstorm watch area is approximately along and 45
statute miles north and south of a line from 35 miles south of
Redwood Falls MN to 45 miles east of Mankato MN. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU1).
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 469...WW 470...
AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 75 knots. A
few cumulonimbi with maximum tops to 550. Mean storm motion vector
25050.
...GuyerSPC 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, 2:32 AM CDT | Severe Thunderstorm Watch | SPC | Big Stone, Traverse | 5 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, 6:09 PM CDT | Mesoscale Discussion | SPC | Blue Earth, Brown, Cottonwood, Nicollet, Watonwan | 66 min |
Nearby
Severe 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.