Alert archive / South Dakota / Severe Thunderstorm Watches in 2021

Severe Thunderstorm Watch 249

June 8, 20218 counties in South Dakota

The Storm Prediction Center issued this severe thunderstorm watch at Jun 8, 2021, 7:00 PM MDT for 8 counties in South Dakota. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued: Jun 8, 2021, 7:00 PM MDT (01:00 UTC)
Expired: Jun 9, 2021, 12:00 AM MDT
In force: 5 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1.5 in
Strongest gust expected: 60 kt

Counties Butte County, SD, Custer County, SD, Fall River County, SD, Harding County, SD, Lawrence County, SD, Meade County, SD, Pennington County, SD, Perkins County, SD

The radar

The Rapid City radar (KUDX), 94 km from the middle of the area, began a volume at 01:03 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: 40%
One or more gusts of 65 knots or more: 20%
Ten or more severe hail reports: 40%
One or more hailstones of 2 inches or more: 20%
Six or more combined severe hail and wind reports: 70%

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
Jun 8, 7:46 PM MDT	Severe Thunderstorm Warning	UNR	Custer, Fall River, Pennington	59 min
Jun 8, 7:48 PM MDT	Severe Thunderstorm Warning	UNR	Butte, Lawrence, Meade	57 min
Jun 8, 8:20 PM MDT	Severe Thunderstorm Warning	UNR	Perkins	55 min
Jun 8, 8:41 PM MDT	Severe Thunderstorm Warning	UNR	Custer, Pennington	64 min
Jun 8, 8:44 PM MDT	Severe Thunderstorm Warning	UNR	Butte, Lawrence, Meade	61 min
Jun 8, 9:10 PM MDT	Severe Thunderstorm Warning	UNR	Perkins	29 min
Jun 8, 10:50 PM MDT	Severe Thunderstorm Warning	UNR	Haakon, Meade, Perkins, Ziebach	55 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

Rapid City, SD (KUNR), launched 00:00Z, 1.0 hours before the alert went out and 100 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: 2269 J/kg
Mixed-layer CIN: -7 J/kg
Mixed-layer LCL: 2498 m above ground
0-6 km bulk shear: 26 kt
0-1 km storm-relative helicity: 49 m²/s²
0-3 km storm-relative helicity: 162 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 9.2

Open this sounding in Storm Lab

The text

As transmitted.

725 
WWUS20 KWNS 090057
SEL9  
SPC WW 090057
SDZ000-090600-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 249
NWS Storm Prediction Center Norman OK
700 PM MDT Tue Jun 8 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Western South Dakota

* Effective this Tuesday night from 700 PM until Midnight MDT.

* Primary threats include...
  Scattered damaging wind gusts to 70 mph possible
  Scattered large hail events to 1.5 inches in diameter possible

SUMMARY...High-based thunderstorms now forming in Wyoming will
spread into western South Dakota with some intensification possible
this evening.  The stronger storms in a broken band may produce
occasional damaging gusts and large hail.

The severe thunderstorm watch area is approximately along and 50
statute miles east and west of a line from 35 miles northeast of
Buffalo SD to 35 miles south of Rapid City 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 247...WW 248...

AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 550. Mean storm motion vector
24020.

...Thompson

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 8, 6:37 PM MDT	Mesoscale Discussion	SPC	Butte, Custer, Fall River, Lawrence, Meade, Pennington	83 min
Jun 8, 8:50 PM MDT	Mesoscale Discussion	SPC	Butte, Custer, Harding, Lawrence, Meade, Pennington and 1 more	85 min
Jun 8, 10:41 PM MDT	Mesoscale Discussion	SPC	Corson, Dewey, Haakon, Jackson, Oglala Lakota, Ziebach	94 min

Nearby

Severe Thunderstorm Watches in South Dakota, 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.