Alert archive / South Dakota / Severe Thunderstorm Watches in 2011
Severe Thunderstorm Watch 769
The Storm Prediction Center issued this severe thunderstorm watch at Aug 11, 2011, 7:19 PM CDT for 4 states. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 11, 2011, 7:19 PM CDT (00:19 UTC)
- Expired
- Aug 11, 2011, 11:55 PM CDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 60 kt
All 44 counties
Cherokee County, IA, Ida County, IA, Lyon County, IA, O'Brien County, IA, Osceola County, IA, Plymouth County, IA, Sioux County, IA, Woodbury County, IA, Pipestone County, MN, Rock County, MN, Antelope County, NE, Boone County, NE, Burt County, NE, Cedar County, NE, Colfax County, NE, Cuming County, NE, Dakota County, NE, Dixon County, NE, Knox County, NE, Madison County, NE, Pierce County, NE, Platte County, NE, Stanton County, NE, Thurston County, NE, Wayne County, NE, Bon Homme County, SD, Brookings County, SD, Charles Mix County, SD, Clay County, SD, Davison County, SD, Douglas County, SD, Gregory County, SD, Hanson County, SD, Hutchinson County, SD, Kingsbury County, SD, Lake County, SD, Lincoln County, SD, McCook County, SD, Miner County, SD, Minnehaha County, SD, Moody County, SD, Turner County, SD, Union County, SD, Yankton County, SD
The radar
The Sioux Falls radar (KFSD), 71 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
- 10%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
4 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 11, 7:29 PM CDT | Severe Thunderstorm Warning | FSD | Bon Homme, Charles Mix, Davison, Douglas, Gregory, Hanson and 2 more | 46 min |
| Aug 11, 8:01 PM CDT | Severe Thunderstorm Warning | FSD | Bon Homme, Clay, Hutchinson, Turner, Yankton | 44 min |
| Aug 11, 8:03 PM CDT | Severe Thunderstorm Warning | OAX | Cedar, Knox | 42 min |
| Aug 11, 8:46 PM CDT | Severe Thunderstorm Warning | OAX | Antelope, Cedar, Knox, Pierce, Wayne | 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, 0.3 hours before the alert went out and 196 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
- 1500 J/kg
- Mixed-layer CIN
- -15 J/kg
- Mixed-layer LCL
- 1257 m above ground
- 0-6 km bulk shear
- 38 kt
- 0-1 km storm-relative helicity
- 3 m²/s²
- 0-3 km storm-relative helicity
- 45 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 0.7
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 11, 9:42 PM CDT | Mesoscale Discussion | SPC | Cherokee, Ida, Lyon, O'Brien, Osceola, Plymouth and 2 more | 63 min |
| Aug 12, 1:18 PM CDT | Mesoscale Discussion | SPC | Becker, Big Stone, Chippewa, Clay, Douglas, Grant and 11 more | 57 min |
| Aug 12, 3:44 PM CDT | Mesoscale Discussion | SPC | Becker, Beltrami, Big Stone, Cass, Chippewa, Clay and 26 more | 91 min |
| Aug 11, 9:22 PM CDT | Mesoscale Discussion | SPC | Blaine, Boyd, Brown, Cherry, Garfield, Grant and 8 more | 53 min |
| Aug 11, 10:16 PM CDT | Severe Thunderstorm Watch | SPC | Adams, Buffalo, Clay, Dawson, Fillmore, Gosper and 12 more | 6 hr |
| Aug 12, 1:45 AM CDT | Mesoscale Discussion | SPC | Adams, Blaine, Buffalo, Cherry, Clay, Custer and 27 more | 2 hr |
| Aug 11, 7:16 PM CDT | Severe Thunderstorm Watch | SPC | Butte, Harding, Lawrence, Meade, Perkins, Ziebach | 4 hr |
| Aug 11, 9:55 PM CDT | Mesoscale Discussion | SPC | Butte, Harding, Lawrence, Meade, Perkins, Ziebach | 65 min |
| Aug 12, 1:47 PM CDT | Severe Thunderstorm Watch | SPC | Brown, Clark, Codington, Day, Deuel, Edmunds and 7 more | 6 hr |
Nearby
Severe Thunderstorm Watches in South Dakota, 2011Severe Thunderstorm Watches in Nebraska, 2011Severe Thunderstorm Watches in Iowa, 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.