Alert archive / South Dakota / Severe Thunderstorm Watches in 2011
Severe Thunderstorm Watch 266
The Storm Prediction Center issued this severe thunderstorm watch at May 9, 2011, 2:26 PM MDT for 5 counties in Nebraska; 5 counties in South Dakota; 6 counties in Wyoming. It was in force for 7 hr.
The area
The outline as issued.
The facts
- Issued
- May 9, 2011, 2:26 PM MDT (20:26 UTC)
- Expired
- May 9, 2011, 9:00 PM MDT
- In force
- 7 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
Counties Box Butte County, NE, Dawes County, NE, Scotts Bluff County, NE, Sheridan County, NE, Sioux County, NE, Custer County, SD, Fall River County, SD, Lawrence County, SD, Meade County, SD, Pennington County, SD, Converse County, WY, Crook County, WY, Goshen County, WY, Niobrara County, WY, Platte County, WY, Weston County, WY
The radar
The Rapid City radar (KUDX), 179 km from the middle of the area, began a volume at 20:28 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
- 50%
- One or more hailstones of 2 inches or more
- 20%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
26 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 9, 4:23 PM MDT | Severe Thunderstorm Warning | CYS | Platte | 37 min |
| May 9, 4:57 PM MDT | Severe Thunderstorm Warning | CYS | Converse, Goshen, Niobrara, Platte | 48 min |
| May 9, 4:59 PM MDT | Severe Thunderstorm Warning | CYS | Converse, Goshen, Niobrara, Platte | 46 min |
| May 9, 5:42 PM MDT | Severe Thunderstorm Warning | UNR | Weston | 63 min |
| May 9, 5:43 PM MDT | Severe Thunderstorm Warning | CYS | Goshen, Niobrara | 43 min |
| May 9, 5:53 PM MDT | Flash Flood Warning | UNR | Weston | 5 hr |
| May 9, 6:03 PM MDT | Severe Thunderstorm Warning | CYS | Sioux | 57 min |
| May 9, 6:11 PM MDT | Severe Thunderstorm Warning | UNR | Weston | 79 min |
| May 9, 6:49 PM MDT | Flash Flood Warning | UNR | Custer, Fall River | 4 hr |
| May 9, 6:52 PM MDT | Severe Thunderstorm Warning | UNR | Campbell, Crook | 68 min |
| May 9, 6:55 PM MDT | Tornado Warning | CYS | Dawes, Sioux | 35 min |
| May 9, 6:58 PM MDT | Severe Thunderstorm Warning | UNR | Fall River | 62 min |
| May 9, 7:21 PM MDT | Severe Thunderstorm Warning | UNR | Meade | 54 min |
| May 9, 7:32 PM MDT | Tornado Warning | CYS | Dawes, Sioux | 43 min |
| May 9, 7:34 PM MDT | Severe Thunderstorm Warning | UNR | Meade, Perkins | 56 min |
| May 9, 7:51 PM MDT | Severe Thunderstorm Warning | UNR | Haakon, Pennington | 42 min |
| May 9, 7:53 PM MDT | Tornado Warning | CYS | Box Butte, Dawes, Sioux | 28 min |
| May 9, 7:56 PM MDT | Severe Thunderstorm Warning | UNR | Meade | 64 min |
| May 9, 8:04 PM MDT | Tornado Warning | UNR | Fall River | 56 min |
| May 9, 8:13 PM MDT | Severe Thunderstorm Warning | UNR | Haakon, Meade, Pennington, Ziebach | 62 min |
| May 9, 8:17 PM MDT | Tornado Warning | CYS | Box Butte, Dawes | 30 min |
| May 9, 8:19 PM MDT | Flash Flood Warning | UNR | Meade, Perkins, Ziebach | 6 hr |
| May 9, 8:24 PM MDT | Severe Thunderstorm Warning | UNR | Meade, Perkins | 66 min |
| May 9, 8:32 PM MDT | Tornado Warning | LBF | Sheridan | 28 min |
| May 9, 8:35 PM MDT | Severe Thunderstorm Warning | UNR | Meade | 46 min |
| May 9, 8:57 PM MDT | Severe Thunderstorm Warning | UNR | Custer, Pennington | 78 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 12:00Z, 8.4 hours before the alert went out and 172 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
- 90 J/kg
- Mixed-layer CIN
- -588 J/kg
- Mixed-layer LCL
- 782 m above ground
- 0-6 km bulk shear
- 39 kt
- 0-1 km storm-relative helicity
- 95 m²/s²
- 0-3 km storm-relative helicity
- 108 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.0
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 8, 7:47 PM MDT | Mesoscale Discussion | SPC | Antelope, Boone, Boyd, Brown, Garfield, Holt and 4 more | 58 min |
| May 9, 4:57 PM MDT | Mesoscale Discussion | SPC | Box Butte, Dawes, Morrill, Scotts Bluff, Sioux | 93 min |
| May 9, 1:17 PM MDT | Mesoscale Discussion | SPC | Campbell, Converse, Crook, Fremont, Hot Springs, Johnson and 4 more | 58 min |
Nearby
Severe Thunderstorm Watches in South Dakota, 2011Severe Thunderstorm Watches in Wyoming, 2011Severe Thunderstorm Watches in Nebraska, 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.