Alert archive / Iowa / Severe Thunderstorm Watches in 2012
Severe Thunderstorm Watch 242
The Storm Prediction Center issued this severe thunderstorm watch at May 4, 2012, 6:01 PM CDT for 28 counties in Iowa. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- May 4, 2012, 6:01 PM CDT (23:01 UTC)
- Expired
- May 4, 2012, 9:00 PM CDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 28 counties
Benton County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Buchanan County, IA, Butler County, IA, Cedar County, IA, Chickasaw County, IA, Clayton County, IA, Delaware County, IA, Dubuque County, IA, Fayette County, IA, Floyd County, IA, Greene County, IA, Grundy County, IA, Hardin County, IA, Howard County, IA, Iowa County, IA, Jasper County, IA, Johnson County, IA, Jones County, IA, Linn County, IA, Marshall County, IA, Mitchell County, IA, Poweshiek County, IA, Story County, IA, Tama County, IA, Winneshiek County, IA
The radar
The La Crosse radar (KARX), 155 km from the middle of the area, began a volume at 23:01 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
- 40%
- 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
- 80%
Warnings issued inside it
2 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 4, 6:20 PM CDT | Severe Thunderstorm Warning | ARX | Floyd, Mitchell | 55 min |
| May 4, 7:15 PM CDT | Severe Thunderstorm Warning | ARX | Chickasaw, Floyd, Howard | 45 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
Davenport, (KDVN), launched 12:00Z, 11.0 hours before the alert went out and 168 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
- 16 J/kg
- Mixed-layer CIN
- -274 J/kg
- Mixed-layer LCL
- 717 m above ground
- 0-6 km bulk shear
- 26 kt
- 0-1 km storm-relative helicity
- 17 m²/s²
- 0-3 km storm-relative helicity
- 15 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 |
|---|---|---|---|---|
| May 3, 7:09 PM CDT | Tornado Watch | SPC | Adair, Adams, Appanoose, Cass, Cedar, Clarke and 23 more | 6 hr |
| May 3, 11:18 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Appanoose, Cass, Cedar, Clarke and 23 more | 27 min |
| May 4, 12:53 AM CDT | Severe Thunderstorm Watch | SPC | Des Moines, Henry, Jefferson, Lee, Van Buren | 4 hr |
| May 4, 2:16 AM CDT | Mesoscale Discussion | SPC | Appanoose, Davis, Decatur, Des Moines, Henry, Jefferson and 9 more | 119 min |
| May 4, 1:50 PM CDT | Mesoscale Discussion | SPC | Buena Vista, Cherokee, Clay, Dickinson, Emmet, Ida and 7 more | 25 min |
| May 4, 2:00 PM CDT | Severe Thunderstorm Watch | SPC | Buena Vista, Calhoun, Carroll, Cerro Gordo, Cherokee, Clay and 23 more | 9 hr |
| May 4, 3:52 PM CDT | Mesoscale Discussion | SPC | Buena Vista, Cerro Gordo, Cherokee, Clay, Dickinson, Emmet and 17 more | 53 min |
| May 4, 5:31 PM CDT | Mesoscale Discussion | SPC | Audubon, Benton, Black Hawk, Boone, Bremer, Buchanan and 66 more | 29 min |
| May 4, 5:52 PM CDT | Severe Thunderstorm Watch | SPC | Fremont, Harrison, Mills, Monona, Montgomery, Page and 2 more | 5 hr |
Nearby
Severe Thunderstorm Watches in Iowa, 2012Every severe thunderstorm watch in 2012
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.