Alert archive / Iowa / Tornado Watches in 2026
Tornado Watch 218
The Storm Prediction Center issued this tornado watch at May 17, 2026, 8:07 PM CDT for 35 counties in Iowa; 8 counties in Missouri. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- May 17, 2026, 8:07 PM CDT (01:07 UTC)
- Expired
- May 18, 2026, 1:07 AM CDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 70 kt
All 43 counties
Adair County, IA, Adams County, IA, Audubon County, IA, Black Hawk County, IA, Boone County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Clarke County, IA, Crawford County, IA, Dallas County, IA, Decatur County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hardin County, IA, Jasper County, IA, Lucas County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Monroe County, IA, Polk County, IA, Poweshiek County, IA, Ringgold County, IA, Sac County, IA, Story County, IA, Tama County, IA, Taylor County, IA, Union County, IA, Warren County, IA, Wayne County, IA, Webster County, IA, Andrew County, MO, Atchison County, MO, Gentry County, MO, Harrison County, MO, Holt County, MO, Mercer County, MO, Nodaway County, MO, Worth County, MO
The radar
The Des Moines radar (KDMX), 20 km from the middle of the area, began a volume at 01:08 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
- 40%
- One or more EF2 to EF5 tornadoes
- 20%
- Ten or more severe wind reports
- 70%
- One or more gusts of 65 knots or more
- 60%
- Ten or more severe hail reports
- 30%
- One or more hailstones of 2 inches or more
- 20%
- Six or more combined severe hail and wind reports
- 90%
Warnings issued inside it
16 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 17, 8:19 PM CDT | Severe Thunderstorm Warning | DMX | Calhoun, Palo Alto, Pocahontas, Sac | 56 min |
| May 17, 8:34 PM CDT | Severe Thunderstorm Warning | DMX | Calhoun, Carroll, Crawford, Greene, Sac | 56 min |
| May 17, 8:35 PM CDT | Tornado Warning | DMX | Calhoun, Pocahontas, Sac | 40 min |
| May 17, 9:02 PM CDT | Severe Thunderstorm Warning | DMX | Calhoun, Hamilton, Humboldt, Kossuth, Palo Alto, Pocahontas and 2 more | 43 min |
| May 17, 9:05 PM CDT | Tornado Warning | DMX | Calhoun, Hamilton, Humboldt, Pocahontas, Webster, Wright | 40 min |
| May 17, 9:12 PM CDT | Tornado Warning | DMX | Calhoun, Hamilton, Webster | 48 min |
| May 17, 9:26 PM CDT | Severe Thunderstorm Warning | DMX | Audubon, Boone, Calhoun, Carroll, Crawford, Dallas and 5 more | 79 min |
| May 17, 9:31 PM CDT | Severe Thunderstorm Warning | DMX | Adair, Adams, Cass | 59 min |
| May 17, 9:33 PM CDT | Severe Thunderstorm Warning | EAX | Atchison | 72 min |
| May 17, 9:42 PM CDT | Severe Thunderstorm Warning | DMX | Calhoun, Franklin, Hamilton, Hardin, Humboldt, Webster and 1 more | 63 min |
| May 17, 9:45 PM CDT | Tornado Warning | DMX | Franklin, Hamilton, Hardin, Humboldt, Webster, Wright | 45 min |
| May 17, 9:56 PM CDT | Tornado Warning | DMX | Hamilton, Hardin, Webster | 38 min |
| May 17, 10:19 PM CDT | Severe Thunderstorm Warning | EAX | Atchison, Holt, Nodaway | 56 min |
| May 17, 10:23 PM CDT | Severe Thunderstorm Warning | DMX | Adair, Dallas, Guthrie, Madison, Polk, Warren | 24 min |
| May 17, 10:53 PM CDT | Severe Thunderstorm Warning | EAX | Andrew, Atchison, Gentry, Holt, Nodaway, Worth | 52 min |
| May 17, 11:45 PM CDT | Severe Thunderstorm Warning | EAX | Daviess, Gentry, Grundy, Harrison, Mercer, Worth | 45 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
- Mesoscale Discussion 760 Severe potential...tornado watch likely
- Mesoscale Discussion 761 Tornado watch 213...214
- Mesoscale Discussion 762 Severe potential...tornado watch likely
- Mesoscale Discussion 764 Tornado watch 213...216
- Mesoscale Discussion 765 Tornado watch 216...218
- Mesoscale Discussion 766 Tornado watch 216...218
The nearest sounding before it
Omaha, NE (KOAX), launched 00:00Z, 1.1 hours before the alert went out and 224 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
- 2478 J/kg
- Mixed-layer CIN
- -15 J/kg
- Mixed-layer LCL
- 1258 m above ground
- 0-6 km bulk shear
- 34 kt
- 0-1 km storm-relative helicity
- 178 m²/s²
- 0-3 km storm-relative helicity
- 298 m²/s²
- Significant tornado parameter
- 2.0
- Supercell composite
- 17.9
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 17, 7:40 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Audubon, Boone, Calhoun, Carroll and 29 more | 65 min |
| May 17, 7:49 PM CDT | Mesoscale Discussion | SPC | Cerro Gordo, Emmet, Floyd, Franklin, Hancock, Howard and 7 more | 56 min |
| May 17, 8:18 PM CDT | Mesoscale Discussion | SPC | Buena Vista, Cherokee, Clay, Emmet, Humboldt, Ida and 5 more | 27 min |
| May 17, 9:30 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Audubon, Boone, Butler, Calhoun and 37 more | 90 min |
| May 17, 10:32 PM CDT | Mesoscale Discussion | SPC | Allamakee, Black Hawk, Boone, Bremer, Buchanan, Butler and 14 more | 118 min |
| May 17, 11:10 PM CDT | Severe Thunderstorm Watch | SPC | Allamakee, Appanoose, Benton, Buchanan, Cedar, Clayton and 13 more | 5 hr |
| May 18, 1:24 AM CDT | Mesoscale Discussion | SPC | Appanoose, Cedar, Davis, Dubuque, Henry, Iowa and 12 more | 96 min |
| May 18, 6:51 AM CDT | Mesoscale Discussion | SPC | Des Moines, Henry, Lee | 84 min |
| May 18, 3:29 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Audubon, Cass, Clarke, Decatur and 12 more | 2 hr |
| May 18, 3:49 PM CDT | Tornado Watch | SPC | Adair, Adams, Appanoose, Cass, Clarke, Davis and 21 more | 6 hr |
| May 18, 5:10 PM CDT | Mesoscale Discussion | SPC | Cherokee, Lyon, Monona, O'Brien, Osceola, Plymouth and 2 more | 95 min |
| May 18, 11:59 AM CDT | Mesoscale Discussion | SPC | Holt | 2 hr |
| May 18, 5:45 PM CDT | Mesoscale Discussion | SPC | Andrew, Atchison, Holt, Nodaway | 2 hr |
| May 18, 6:14 PM CDT | Tornado Watch | SPC | Adair, Bates, Caldwell, Carroll, Cass, Chariton and 19 more | 7 hr |
Nearby
Tornado Watches in Iowa, 2026Tornado Watches in Missouri, 2026Every tornado watch in 2026
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.