Alert archive / Iowa / Severe Thunderstorm Warnings in 2026

Severe Thunderstorm Warning 310, NWS Des Moines, IA

August 7, 2026Black Hawk County, Bremer County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Aug 7, 2026, 3:49 PM CDT for Black Hawk County, Bremer County, Iowa. It was in force for 26 min. 3 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Aug 7, 2026, 3:49 PM CDT (20:49 UTC)
Expired: Aug 7, 2026, 4:15 PM CDT
In force: 26 min
Issued by: NWS Des Moines, IA
Area: Storm-based polygon
Damage threat: Considerable
Hail: 1.0 in
Wind: 70.0 mph

Counties Black Hawk County, IA, Bremer County, IA

The radar

The La Crosse radar (KARX), 152 km from the middle of the area, began a volume at 20:50 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 was reported inside it

Time	Report	Where	Remark
Aug 7, 3:58 PM CDT	HAIL 1.25	5 Se Readlyn, IA	Report from mPING: Half Dollar (1.25 in.).
Aug 7, 3:59 PM CDT	TSTM WND GST 73	5 Sw Tripoli, IA	Measured via Personal Weather Station.
Aug 7, 4:02 PM CDT	HAIL 1.25	5 N Dunkerton, IA	Report via mPING.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Aug 7, 1:40 PM CDT	Severe Thunderstorm Watch	SPC	8 hr

The nearest sounding before it

Minneapolis, MN (KMPX), launched 12:00Z, 8.8 hours before the alert went out and 262 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 506 J/kg
Mixed-layer CIN: -343 J/kg
Mixed-layer LCL: 1332 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 211 m²/s²
0-3 km storm-relative helicity: 250 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

Open this sounding in Storm Lab

The text

As transmitted.

066 
WUUS53 KDMX 072049
SVRDMX
IAC013-017-072115-
/O.NEW.KDMX.SV.W.0310.260807T2049Z-260807T2115Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Des Moines IA
349 PM CDT Fri Aug 7 2026

The National Weather Service in Des Moines has issued a

* Severe Thunderstorm Warning for...
  Northeastern Black Hawk County in northeastern Iowa...
  Eastern Bremer County in northeastern Iowa...

* Until 415 PM CDT.

* At 348 PM CDT, a severe thunderstorm was located near Readlyn, or
  14 miles west of Oelwein, moving east at 40 mph.

  HAZARD...70 mph wind gusts and quarter size hail.

  SOURCE...Emergency management.

  IMPACT...Hail damage to vehicles is expected. Expect considerable 
           tree damage. Wind damage is also likely to mobile homes, 
           roofs, and outbuildings.

* Locations impacted include...
  Sumner, Denver, Tripoli, Dunkerton, and Readlyn.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4261 9240 4287 9234 4288 9208 4255 9208
TIME...MOT...LOC 2048Z 279DEG 34KT 4274 9218 

THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...OBSERVED
MAX WIND GUST...70 MPH

$$

Hagenhoff

The office that day

Everything else NWS Des Moines, IA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 7, 2:52 AM CDT	Dense Fog Advisory	DMX	Adair, Adams, Appanoose, Audubon, Black Hawk, Boone and 44 more	6 hr
Aug 7, 12:46 PM CDT	Severe Thunderstorm Warning	DMX	Winnebago, Worth	29 min
Aug 7, 1:07 PM CDT	Severe Thunderstorm Warning	DMX	Cerro Gordo, Hancock, Winnebago, Worth	23 min
Aug 7, 1:12 PM CDT	Severe Thunderstorm Warning	DMX	Hancock, Wright	48 min
Aug 7, 1:25 PM CDT	Severe Thunderstorm Warning	DMX	Cerro Gordo, Hancock, Winnebago, Worth	50 min
Aug 7, 1:37 PM CDT	Severe Thunderstorm Warning	DMX	Cerro Gordo, Hancock	53 min
Aug 7, 2:52 PM CDT	Severe Thunderstorm Warning	DMX	Bremer, Butler	38 min
Aug 7, 3:53 PM CDT	Tornado Warning Tornado observed	DMX	Black Hawk, Bremer	22 min
Aug 7, 4:16 PM CDT	Severe Thunderstorm Warning	DMX	Black Hawk, Grundy, Tama	59 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2026 Every severe thunderstorm warning 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.