Alert archive / Iowa / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 116, NWS Des Moines, IA

September 20, 20214 counties in Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Sep 20, 2021, 3:38 PM CDT for 4 counties in Iowa. It was in force for 52 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Sep 20, 2021, 3:38 PM CDT (20:38 UTC)
Expired: Sep 20, 2021, 4:30 PM CDT
In force: 52 min
Issued by: NWS Des Moines, IA
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

Counties Clarke County, IA, Madison County, IA, Union County, IA, Warren County, IA

The radar

The Des Moines radar (KDMX), 66 km from the middle of the area, began a volume at 20:37 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.

The watch it was issued in

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

Issued	Product	Office	Lasted
Sep 20, 2:07 PM CDT	Severe Thunderstorm Watch	SPC	7 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 8.6 hours before the alert went out and 201 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: 493 J/kg
Mixed-layer CIN: -291 J/kg
Mixed-layer LCL: 1101 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 414 m²/s²
0-3 km storm-relative helicity: 540 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted.

308 
WUUS53 KDMX 202038
SVRDMX
IAC039-121-175-181-202130-
/O.NEW.KDMX.SV.W.0116.210920T2038Z-210920T2130Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Des Moines IA
338 PM CDT Mon Sep 20 2021

The National Weather Service in Des Moines  has issued a

* Severe Thunderstorm Warning for...
  Eastern Madison County in south central Iowa...
  Northeastern Union County in south central Iowa...
  Northwestern Clarke County in south central Iowa...
  Southwestern Warren County in south central Iowa...

* Until 430 PM CDT.

* At 337 PM CDT, a severe thunderstorm was located 14 miles northeast
  of Creston, moving northeast at 35 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Hail damage to vehicles is expected. Expect wind damage 
           to roofs, siding, and trees.

* Locations impacted include...
  Avenue Of The Saints Event Center.

This includes Interstate 35 between mile markers 40 and 60.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4101 9411 4113 9424 4149 9385 4118 9355
TIME...MOT...LOC 2037Z 229DEG 32KT 4114 9411 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Donavon

3 follow-up statements

233 
WWUS53 KDMX 202052
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
352 PM CDT Mon Sep 20 2021

IAC039-121-175-181-202130-
/O.CON.KDMX.SV.W.0116.000000T0000Z-210920T2130Z/
Madison IA-Union IA-Clarke IA-Warren IA-
352 PM CDT Mon Sep 20 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 430 PM CDT
FOR EASTERN MADISON...NORTHEASTERN UNION...NORTHWESTERN CLARKE AND
SOUTHWESTERN WARREN COUNTIES...

At 351 PM CDT, a severe thunderstorm was located 11 miles northwest
of Lakeside Casino, or 12 miles northwest of Osceola, moving east at
30 mph.

HAZARD...60 mph wind gusts and quarter size hail.

SOURCE...Radar indicated.

IMPACT...Hail damage to vehicles is expected. Expect wind damage to 
         roofs, siding, and trees.

Locations impacted include...
Winterset, Avenue Of The Saints Event Center, St. Charles, New
Virginia, Truro, Martensdale, Lorimor, Patterson, St. Marys, East
Peru, Bevington and Thayer.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 4101 9411 4113 9424 4149 9385 4118 9355
TIME...MOT...LOC 2051Z 251DEG 27KT 4115 9396 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Donavon

384 
WWUS53 KDMX 202113
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
413 PM CDT Mon Sep 20 2021

IAC039-121-175-181-202130-
/O.CON.KDMX.SV.W.0116.000000T0000Z-210920T2130Z/
Madison IA-Union IA-Clarke IA-Warren IA-
413 PM CDT Mon Sep 20 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 430 PM CDT
FOR EASTERN MADISON...NORTHEASTERN UNION...NORTHWESTERN CLARKE AND
SOUTHWESTERN WARREN COUNTIES...

At 412 PM CDT, a severe thunderstorm was located near Avenue Of The
Saints Event Center, or 12 miles north of Osceola, moving northeast
at 30 mph.

HAZARD...60 mph wind gusts and quarter size hail.

SOURCE...Radar indicated.

IMPACT...Hail damage to vehicles is expected. Expect wind damage to 
         roofs, siding, and trees.

Locations impacted include...
Winterset, Avenue Of The Saints Event Center, St. Charles, New
Virginia, Truro, Martensdale, Lorimor, Patterson, St. Marys, East
Peru and Bevington.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 4103 9406 4126 9407 4149 9385 4118 9355
TIME...MOT...LOC 2112Z 244DEG 28KT 4121 9375 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Donavon

219 
WWUS53 KDMX 202126
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
426 PM CDT Mon Sep 20 2021

IAC039-121-175-181-202135-
/O.EXP.KDMX.SV.W.0116.000000T0000Z-210920T2130Z/
Madison IA-Union IA-Clarke IA-Warren IA-
426 PM CDT Mon Sep 20 2021

...THE SEVERE THUNDERSTORM WARNING FOR EASTERN MADISON...NORTHEASTERN
UNION...NORTHWESTERN CLARKE AND SOUTHWESTERN WARREN COUNTIES WILL
EXPIRE AT 430 PM CDT...
        
The storm which prompted the warning has moved out of the area.
Therefore, the warning will be allowed to expire.

A Severe Thunderstorm Watch remains in effect until 1000 PM CDT for
south central Iowa.

Remember, a Severe Thunderstorm Warning still remains in effect for
portions of Warren and Clarke counties until 515 PM CDT.

LAT...LON 4103 9406 4126 9407 4149 9385 4118 9355
TIME...MOT...LOC 2125Z 229DEG 32KT 4128 9364 

$$

Donavon

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 20, 4:23 PM CDT	Severe Thunderstorm Warning	DMX	Clarke, Lucas, Marion, Warren	52 min
Sep 20, 4:57 PM CDT	Severe Thunderstorm Warning	DMX	Lucas, Marion, Monroe, Warren	48 min
Sep 20, 6:34 PM CDT	Severe Thunderstorm Warning	DMX	Appanoose, Davis, Wayne	41 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2021 Every severe thunderstorm warning in 2021

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.