Alert archive / South Dakota / Severe Thunderstorm Watches in 2011
Severe Thunderstorm Watch 768
The Storm Prediction Center issued this severe thunderstorm watch at Aug 11, 2011, 6:16 PM MDT for 4 counties in North Dakota; 6 counties in South Dakota; Campbell County, Crook County, Wyoming. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 11, 2011, 6:16 PM MDT (00:16 UTC)
- Expired
- Aug 11, 2011, 9:52 PM MDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
Counties Adams County, ND, Bowman County, ND, Hettinger County, ND, Slope County, ND, Butte County, SD, Harding County, SD, Lawrence County, SD, Meade County, SD, Perkins County, SD, Ziebach County, SD, Campbell County, WY, Crook County, WY
The radar
The Rapid City radar (KUDX), 157 km from the middle of the area, began a volume at 00:20 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
- 30%
- One or more gusts of 65 knots or more
- 30%
- Ten or more severe hail reports
- 30%
- One or more hailstones of 2 inches or more
- 20%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
5 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 11, 6:55 PM MDT | Severe Thunderstorm Warning | UNR | Campbell, Crook | 65 min |
| Aug 11, 7:06 PM MDT | Severe Thunderstorm Warning | UNR | Harding | 54 min |
| Aug 11, 7:52 PM MDT | Severe Thunderstorm Warning | UNR | Butte, Harding | 68 min |
| Aug 11, 8:00 PM MDT | Severe Thunderstorm Warning | UNR | Harding | 60 min |
| Aug 11, 8:56 PM MDT | Severe Thunderstorm Warning | UNR | Butte, Harding, Meade, Perkins | 64 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, 0.3 hours before the alert went out and 159 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
- 1555 J/kg
- Mixed-layer CIN
- -108 J/kg
- Mixed-layer LCL
- 1592 m above ground
- 0-6 km bulk shear
- 46 kt
- 0-1 km storm-relative helicity
- -74 m²/s²
- 0-3 km storm-relative helicity
- 65 m²/s²
- Significant tornado parameter
- -0.2
- Supercell composite
- -4.1
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 11, 8:55 PM MDT | Mesoscale Discussion | SPC | Adams, Bowman, Hettinger, Slope | 65 min |
| Aug 12, 12:18 PM MDT | Mesoscale Discussion | SPC | Barnes, Cass, Dickey, Eddy, Foster, Grand Forks and 13 more | 57 min |
| Aug 12, 12:47 PM MDT | Severe Thunderstorm Watch | SPC | Barnes, Benson, Cass, Dickey, Eddy, Foster and 13 more | 6 hr |
| Aug 12, 2:44 PM MDT | Mesoscale Discussion | SPC | Barnes, Benson, Cass, Dickey, Eddy, Foster and 16 more | 91 min |
| Aug 11, 6:19 PM MDT | Severe Thunderstorm Watch | SPC | Bon Homme, Brookings, Charles Mix, Clay, Davison, Douglas and 13 more | 5 hr |
| Aug 11, 8:42 PM MDT | Mesoscale Discussion | SPC | Beadle, Bon Homme, Brookings, Clay, Davison, Douglas and 13 more | 63 min |
Nearby
Severe Thunderstorm Watches in South Dakota, 2011Severe Thunderstorm Watches in North Dakota, 2011Severe Thunderstorm Watches in Wyoming, 2011Every severe thunderstorm watch in 2011
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.