Alert archive / Iowa / Severe Thunderstorm Watches in 2020
Severe Thunderstorm Watch 424
The Storm Prediction Center issued this severe thunderstorm watch at Aug 10, 2020, 6:06 AM CDT for 12 counties in Iowa; 9 counties in Nebraska; 7 counties in South Dakota. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 10, 2020, 6:06 AM CDT (11:06 UTC)
- Expired
- Aug 10, 2020, 11:00 AM CDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 65 kt
All 28 counties
Buena Vista County, IA, Cherokee County, IA, Clay County, IA, Dickinson County, IA, Ida County, IA, Lyon County, IA, Monona County, IA, O'Brien County, IA, Osceola County, IA, Plymouth County, IA, Sioux County, IA, Woodbury County, IA, Burt County, NE, Cedar County, NE, Cuming County, NE, Dakota County, NE, Dixon County, NE, Knox County, NE, Pierce County, NE, Thurston County, NE, Wayne County, NE, Bon Homme County, SD, Clay County, SD, Hutchinson County, SD, Lincoln County, SD, Turner County, SD, Union County, SD, Yankton County, SD
The radar
The Sioux Falls radar (KFSD), 69 km from the middle of the area, began a volume at 11:10 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
- 5%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 60%
- One or more gusts of 65 knots or more
- 30%
- Ten or more severe hail reports
- 40%
- One or more hailstones of 2 inches or more
- 30%
- Six or more combined severe hail and wind reports
- 90%
Warnings issued inside it
6 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 10, 6:32 AM CDT | Severe Thunderstorm Warning | FSD | Bon Homme, Clay, Hutchinson, Turner, Yankton | 58 min |
| Aug 10, 6:38 AM CDT | Severe Thunderstorm Warning | OAX | Cedar, Knox | 52 min |
| Aug 10, 6:57 AM CDT | Severe Thunderstorm Warning | OAX | Cedar | 48 min |
| Aug 10, 8:46 AM CDT | Severe Thunderstorm Warning | OAX | Harrison, Monona, Shelby | 29 min |
| Aug 10, 8:49 AM CDT | Severe Thunderstorm Warning | FSD | Ida, Woodbury | 41 min |
| Aug 10, 9:26 AM CDT | Severe Thunderstorm Warning | FSD | Buena Vista, Ida | 34 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, 11.1 hours before the alert went out and 242 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
- 93 J/kg
- Mixed-layer CIN
- -321 J/kg
- Mixed-layer LCL
- 1751 m above ground
- 0-6 km bulk shear
- 42 kt
- 0-1 km storm-relative helicity
- -60 m²/s²
- 0-3 km storm-relative helicity
- 174 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -5.3
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 9, 10:59 PM CDT | Mesoscale Discussion | SPC | Allamakee, Bremer, Buena Vista, Butler, Calhoun, Carroll and 32 more | 3 hr |
| Aug 10, 3:19 AM CDT | Mesoscale Discussion | SPC | Lyon, O'Brien, Osceola, Plymouth, Sioux, Woodbury | 116 min |
| Aug 10, 7:46 AM CDT | Mesoscale Discussion | SPC | Ida, Monona, Plymouth, Woodbury | 89 min |
| Aug 10, 8:40 AM CDT | Mesoscale Discussion | SPC | Adair, Adams, Appanoose, Audubon, Boone, Calhoun and 39 more | 65 min |
| Aug 10, 8:56 AM CDT | Severe Thunderstorm Watch | SPC | Adair, Audubon, Black Hawk, Boone, Bremer, Butler and 30 more | 5 hr |
| Aug 10, 9:45 AM CDT | Mesoscale Discussion | SPC | Adair, Audubon, Boone, Calhoun, Carroll, Cass and 17 more | 90 min |
| Aug 10, 10:42 AM CDT | Mesoscale Discussion | SPC | Allamakee, Buchanan, Cedar, Chickasaw, Clayton, Clinton and 18 more | 93 min |
| Aug 10, 11:00 AM CDT | Mesoscale Discussion | SPC | Boone, Dallas, Jasper, Mahaska, Marion, Marshall and 5 more | 60 min |
| Aug 10, 11:26 AM CDT | Severe Thunderstorm Watch | SPC | Benton, Buchanan, Cedar, Clayton, Clinton, Delaware and 17 more | 7 hr |
| Aug 10, 12:14 PM CDT | Mesoscale Discussion | SPC | Benton, Cedar, Clinton, Iowa, Jackson, Johnson and 10 more | 91 min |
| Aug 10, 1:36 PM CDT | Mesoscale Discussion | SPC | Clinton, Jackson, Scott | 114 min |
| Aug 9, 7:38 PM CDT | Mesoscale Discussion | SPC | Antelope, Arthur, Blaine, Brown, Custer, Garfield and 10 more | 97 min |
Nearby
Severe Thunderstorm Watches in Iowa, 2020Severe Thunderstorm Watches in Nebraska, 2020Severe Thunderstorm Watches in South Dakota, 2020Every severe thunderstorm watch in 2020
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.