Alert archive / Minnesota / Severe Thunderstorm Watches in 2021

Severe Thunderstorm Watch 515

October 9, 202120 counties in Minnesota

The Storm Prediction Center issued this severe thunderstorm watch at Oct 9, 2021, 6:34 PM CDT for 20 counties in Minnesota. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued: Oct 9, 2021, 6:34 PM CDT (23:34 UTC)
Expired: Oct 10, 2021, 2:00 AM CDT
In force: 7 hr
Issued by: the Storm Prediction Center
Largest hail expected: 2 in
Strongest gust expected: 65 kt

Counties Becker County, MN, Cass County, MN, Chippewa County, MN, Crow Wing County, MN, Douglas County, MN, Grant County, MN, Hubbard County, MN, Kandiyohi County, MN, Lac qui Parle County, MN, Meeker County, MN, Morrison County, MN, Otter Tail County, MN, Pope County, MN, Renville County, MN, Stearns County, MN, Stevens County, MN, Swift County, MN, Todd County, MN, Wadena County, MN, Yellow Medicine County, MN

The radar

The Minneapolis radar (KMPX), 164 km from the middle of the area, began a volume at 23:37 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: 60%
One or more gusts of 65 knots or more: 30%
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: 80%

Warnings issued inside it

7 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Oct 9, 7:19 PM CDT	Severe Thunderstorm Warning	MPX	Stevens, Swift	41 min
Oct 9, 7:26 PM CDT	Severe Thunderstorm Warning Considerable damage threat	FGF	Grant, Otter Tail, Wilkin	64 min
Oct 9, 7:35 PM CDT	Severe Thunderstorm Warning	MPX	Lac qui Parle	25 min
Oct 9, 7:56 PM CDT	Severe Thunderstorm Warning	MPX	Stevens, Swift	49 min
Oct 9, 7:58 PM CDT	Severe Thunderstorm Warning	MPX	Lac qui Parle	47 min
Oct 9, 8:06 PM CDT	Severe Thunderstorm Warning	FGF	Clay, Grant, Otter Tail, Wilkin	41 min
Oct 9, 8:15 PM CDT	Severe Thunderstorm Warning	MPX	Douglas, Pope	45 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, 11.6 hours before the alert went out and 162 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 261 J/kg
Mixed-layer CIN: -163 J/kg
Mixed-layer LCL: 1242 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 70 m²/s²
0-3 km storm-relative helicity: 97 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

085 
WWUS20 KWNS 092332
SEL5  
SPC WW 092332
MNZ000-100700-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 515
NWS Storm Prediction Center Norman OK
635 PM CDT Sat Oct 9 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Central Minnesota

* Effective this Saturday night and Sunday morning from 635 PM
  until 200 AM CDT.

* Primary threats include...
  Scattered damaging winds likely with isolated significant gusts
    to 75 mph possible
  Scattered large hail and isolated very large hail events to 2
    inches in diameter possible
  A tornado or two possible

SUMMARY...A line of severe thunderstorms will continue moving
northeast across the watch area this evening and overnight with a
risk for damaging winds and isolated large hail. A tornado or two
will also be possible.

The severe thunderstorm watch area is approximately along and 55
statute miles east and west of a line from 50 miles northwest of
Brainerd MN to 65 miles southeast of Ortonville MN. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU5).

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 514...

AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 65 knots. A
few cumulonimbi with maximum tops to 450. Mean storm motion vector
24035.

...Bunting

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 9, 12:04 PM CDT	Mesoscale Discussion	SPC	Lincoln	2 hr
Oct 9, 2:56 PM CDT	Severe Thunderstorm Watch	SPC	Big Stone, Traverse, Wilkin	7 hr
Oct 9, 6:00 PM CDT	Mesoscale Discussion	SPC	Big Stone, Chippewa, Douglas, Grant, Kandiyohi, Lac qui Parle and 9 more	90 min

Nearby

Severe Thunderstorm Watches in Minnesota, 2021 Every 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.