Alert archive / South Dakota / Severe Thunderstorm Watches in 2011
Severe Thunderstorm Watch 700
The Storm Prediction Center issued this severe thunderstorm watch at Jul 29, 2011, 1:54 PM MDT for 4 states. It was in force for 7 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 29, 2011, 1:54 PM MDT (19:54 UTC)
- Expired
- Jul 29, 2011, 9:00 PM MDT
- In force
- 7 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2.5 in
- Strongest gust expected
- 60 kt
All 24 counties
Carter County, MT, Custer County, MT, Fallon County, MT, Powder River County, MT, Banner County, NE, Box Butte County, NE, Dawes County, NE, Morrill County, NE, Scotts Bluff County, NE, Sioux County, NE, Butte County, SD, Custer County, SD, Fall River County, SD, Haakon County, SD, Harding County, SD, Lawrence County, SD, Meade County, SD, Pennington County, SD, Perkins County, SD, Ziebach County, SD, Crook County, WY, Goshen County, WY, Niobrara County, WY, Weston County, WY
The radar
The Rapid City radar (KUDX), 118 km from the middle of the area, began a volume at 19:54 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
- 50%
- Six or more combined severe hail and wind reports
- 80%
Warnings issued inside it
12 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 29, 3:26 PM MDT | Severe Thunderstorm Warning | BYZ | Carter | 64 min |
| Jul 29, 4:07 PM MDT | Severe Thunderstorm Warning | UNR | Butte, Meade | 68 min |
| Jul 29, 4:22 PM MDT | Severe Thunderstorm Warning | UNR | Lawrence, Meade | 53 min |
| Jul 29, 4:37 PM MDT | Severe Thunderstorm Warning | UNR | Butte | 68 min |
| Jul 29, 4:55 PM MDT | Severe Thunderstorm Warning | UNR | Custer, Pennington | 37 min |
| Jul 29, 5:18 PM MDT | Severe Thunderstorm Warning | UNR | Meade | 57 min |
| Jul 29, 5:39 PM MDT | Severe Thunderstorm Warning | BYZ | Fallon | 49 min |
| Jul 29, 5:49 PM MDT | Severe Thunderstorm Warning | UNR | Meade | 56 min |
| Jul 29, 5:54 PM MDT | Severe Thunderstorm Warning | UNR | Meade, Pennington | 51 min |
| Jul 29, 6:11 PM MDT | Severe Thunderstorm Warning | UNR | Perkins | 64 min |
| Jul 29, 6:18 PM MDT | Severe Thunderstorm Warning | UNR | Perkins | 57 min |
| Jul 29, 7:35 PM MDT | Severe Thunderstorm Warning | UNR | 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 12:00Z, 7.9 hours before the alert went out and 111 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
- 1117 J/kg
- Mixed-layer CIN
- -137 J/kg
- Mixed-layer LCL
- 1219 m above ground
- 0-6 km bulk shear
- 23 kt
- 0-1 km storm-relative helicity
- 40 m²/s²
- 0-3 km storm-relative helicity
- 72 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.3
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 29, 12:59 PM MDT | Mesoscale Discussion | SPC | Carter | 91 min |
| Jul 29, 4:46 PM MDT | Mesoscale Discussion | SPC | Carter, Custer, Daniels, Dawson, Fallon, McCone and 5 more | 59 min |
| Jul 29, 5:02 PM MDT | Severe Thunderstorm Watch | SPC | Daniels, Dawson, McCone, Prairie, Richland, Roosevelt and 2 more | 6 hr |
Nearby
Severe Thunderstorm Watches in South Dakota, 2011Severe Thunderstorm Watches in Nebraska, 2011Severe Thunderstorm Watches in Montana, 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.