Alert archive / Iowa / Severe Thunderstorm Watches in 2018
Severe Thunderstorm Watch 60
The Storm Prediction Center issued this severe thunderstorm watch at May 1, 2018, 5:47 PM CDT for 50 counties in Iowa; 7 counties in Minnesota; 6 counties in Wisconsin. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- May 1, 2018, 5:47 PM CDT (22:47 UTC)
- Expired
- May 1, 2018, 11:26 PM CDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 63 counties
Adair County, IA, Allamakee County, IA, Audubon County, IA, Benton County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Buchanan County, IA, Butler County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Cerro Gordo County, IA, Chickasaw County, IA, Clayton County, IA, Crawford County, IA, Dallas County, IA, Delaware County, IA, Emmet County, IA, Fayette County, IA, Floyd County, IA, Franklin County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hancock County, IA, Hardin County, IA, Howard County, IA, Humboldt County, IA, Jasper County, IA, Kossuth County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Mitchell County, IA, Palo Alto County, IA, Pocahontas County, IA, Polk County, IA, Poweshiek County, IA, Sac County, IA, Story County, IA, Tama County, IA, Warren County, IA, Webster County, IA, Winnebago County, IA, Winneshiek County, IA, Worth County, IA, Wright County, IA, Dodge County, MN, Fillmore County, MN, Freeborn County, MN, Houston County, MN, Mower County, MN, Olmsted County, MN, Winona County, MN, Crawford County, WI, Grant County, WI, La Crosse County, WI, Monroe County, WI, Richland County, WI, Vernon County, WI
The radar
The Des Moines radar (KDMX), 57 km from the middle of the area, began a volume at 22:50 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
- 50%
- One or more gusts of 65 knots or more
- 10%
- 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
- 80%
Warnings issued inside it
7 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 1, 5:54 PM CDT | Severe Thunderstorm Warning | DMX | Marshall, Story | 36 min |
| May 1, 6:05 PM CDT | Severe Thunderstorm Warning | DMX | Humboldt, Kossuth, Palo Alto, Pocahontas | 40 min |
| May 1, 6:24 PM CDT | Severe Thunderstorm Warning | DMX | Marshall, Tama | 36 min |
| May 1, 6:40 PM CDT | Severe Thunderstorm Warning | DMX | Hancock, Humboldt, Kossuth, Wright | 50 min |
| May 1, 7:47 PM CDT | Severe Thunderstorm Warning | DMX | Audubon, Cass, Guthrie | 43 min |
| May 1, 8:17 PM CDT | Severe Thunderstorm Warning | DMX | Boone, Dallas, Greene, Guthrie | 43 min |
| May 1, 8:25 PM CDT | Severe Thunderstorm Warning | DVN | Delaware | 35 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
Omaha, NE (KOAX), launched 12:00Z, 10.8 hours before the alert went out and 255 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
- 787 J/kg
- Mixed-layer CIN
- -48 J/kg
- Mixed-layer LCL
- 955 m above ground
- 0-6 km bulk shear
- 53 kt
- 0-1 km storm-relative helicity
- 74 m²/s²
- 0-3 km storm-relative helicity
- 57 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 2.2
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 1, 10:24 AM CDT | Mesoscale Discussion | SPC | Appanoose, Clarke, Decatur, Jasper, Lucas, Madison and 10 more | 3 hr |
| May 1, 2:47 PM CDT | Tornado Watch | SPC | Harrison, Monona, Pottawattamie, Shelby | 9 hr |
| May 1, 3:16 PM CDT | Mesoscale Discussion | SPC | Audubon, Black Hawk, Boone, Bremer, Buena Vista, Butler and 24 more | 89 min |
| May 1, 5:00 PM CDT | Mesoscale Discussion | SPC | Cass, Fremont, Mills, Montgomery, Page, Pottawattamie | 2 hr |
Nearby
Severe Thunderstorm Watches in Iowa, 2018Severe Thunderstorm Watches in Minnesota, 2018Severe Thunderstorm Watches in Wisconsin, 2018Every severe thunderstorm watch in 2018
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.