Alert archive / Iowa / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 129, NWS Des Moines, IA

December 15, 202111 counties in Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Dec 15, 2021, 6:24 PM CST for 11 counties in Iowa. It was in force for 66 min. 12 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: Dec 15, 2021, 6:24 PM CST (00:24 UTC)
Expired: Dec 15, 2021, 7:30 PM CST
In force: 66 min
Issued by: NWS Des Moines, IA
Area: Storm-based polygon
Damage threat: Considerable
Hail: 0.75 in
Wind: 70.0 mph

Counties Clarke County, IA, Dallas County, IA, Jasper County, IA, Lucas County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Monroe County, IA, Polk County, IA, Poweshiek County, IA, Warren County, IA

The radar

The Des Moines radar (KDMX), 58 km from the middle of the area, began a volume at 00:25 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
Dec 15, 6:27 PM CST	TSTM WND GST 61	Des Moines Int Airport, IA
Dec 15, 6:27 PM CST	TSTM WND GST 75	1 Wnw Johnston, IA
Dec 15, 6:28 PM CST	TSTM WND DMG	2 Ne Des Moines Int Air, IA	PHONE POLE DAMAGE AT WAKONDA GOLF COURSE. REPORT FROM BROADCAST MEDIA. TIME ESTIMATED BY RADAR.
Dec 15, 6:35 PM CST	TSTM WND GST 60	3 E Saylorville, IA	AWOS STATION KIKV ANKENY AIRPORT.
Dec 15, 6:36 PM CST	TSTM WND DMG	Indianola, IA	NUMEROUS TREES DOWN BLOCKING 65/69 700 BLK S. JEFFERSON WAY. OTHER TREES DOWN IN INDIANOLA.
Dec 15, 6:37 PM CST	TSTM WND GST 70	Indianola, IA	LOCAL TRAINED SPOTTERS REPORTING NUMEROUS TREES DOWN AND WIND GUSTS 65-70MPH.
Dec 15, 6:55 PM CST	TSTM WND GST 64	3 Ssw Knoxville, IA	AWOS STATION KOXV KNOXVILLE AIRPORT.
Dec 15, 7:03 PM CST	TSTM WND DMG	3 Se Newton, IA	ROOF OFF OF A GARAGE AND AN OUTBUILDING TIPPED ON ITS SIDE. REPORT FROM BROADCAST MEDIA. TIME ESTIMATED VIA RADAR.
Dec 15, 7:05 PM CST	TSTM WND DMG	Pella, IA	LARGE LIMBS DOWN AND METAL ROOF BLOWN OFF. TIME ESTIMATED VIA RADAR.
Dec 15, 7:15 PM CST	TSTM WND GST 60	2 Wsw Pella, IA	PEAK WIND GUST FROM KPEA.
Dec 15, 7:25 PM CST	TSTM WND DMG	5 W Malcom, IA	2 SEMIS OVERTURNED ON I80 WB NEAR THE 185 TO 186 MM, JUST EAST OF GRINNELL.
Dec 15, 7:31 PM CST	TSTM WND GST 64	2 Ssw Prairie City, IA	MESONET STATION NSWI4 NEIL SMITH NWR.

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
Dec 15, 1:23 PM CST	Tornado Watch	SPC	7 hr

The nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 0.4 hours before the alert went out and 225 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: 229 J/kg
Mixed-layer CIN: -358 J/kg
Mixed-layer LCL: 1061 m above ground
0-6 km bulk shear: 56 kt
0-1 km storm-relative helicity: 433 m²/s²
0-3 km storm-relative helicity: 496 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

230 
WUUS53 KDMX 160024
SVRDMX
IAC039-049-099-117-121-123-125-135-153-157-181-160130-
/O.NEW.KDMX.SV.W.0129.211216T0024Z-211216T0130Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Des Moines IA
624 PM CST Wed Dec 15 2021

The National Weather Service in Des Moines  has issued a

* Severe Thunderstorm Warning for...
  Northwestern Monroe County in south central Iowa...
  Northern Lucas County in south central Iowa...
  Western Poweshiek County in central Iowa...
  Polk County in central Iowa...
  Eastern Madison County in south central Iowa...
  Marion County in south central Iowa...
  Western Mahaska County in south central Iowa...
  Jasper County in central Iowa...
  Northern Clarke County in south central Iowa...
  Eastern Dallas County in central Iowa...
  Warren County in south central Iowa...

* Until 730 PM CST.

* At 623 PM CST, severe thunderstorms were located along a line 
  extending from Slater to near New Virginia, moving east at 75 mph.

  HAZARD...70 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Expect considerable tree damage. Damage is likely to 
           mobile homes, roofs, and outbuildings.

* Severe thunderstorms will be near...
  Melcher-Dallas around 640 PM CST.

Other locations in the path of these severe thunderstorms include
Baxter and Rock Creek Lake.

This includes the following highways...
 Interstate 35 between mile markers 39 and 72, and between mile
markers 87 and 101.
 Interstate 80 between mile markers 118 and 189.
 Interstate 235 between mile markers 1 and 14.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

A Tornado Watch remains in effect until 800 PM CST for south central
and central Iowa.

&&

LAT...LON 4108 9281 4110 9395 4186 9382 4186 9254
TIME...MOT...LOC 0023Z 267DEG 66KT 4185 9368 4119 9368 

THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...70 MPH

$$

Martin

2 follow-up statements

446 
WWUS53 KDMX 160048 RRA
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
648 PM CST Wed Dec 15 2021

IAC049-121-160058-
/O.CAN.KDMX.SV.W.0129.000000T0000Z-211216T0130Z/
Madison IA-Dallas IA-
648 PM CST Wed Dec 15 2021

...THE SEVERE THUNDERSTORM WARNING FOR EASTERN MADISON AND EASTERN
DALLAS COUNTIES IS CANCELLED...

The storms which prompted the warning have moved out of the warned 
area. Therefore, the warning has been cancelled.

A Tornado Watch remains in effect until 800 PM CST for south central
and central Iowa.

LAT...LON 4109 9365 4186 9347 4186 9254 4108 9281
TIME...MOT...LOC 0048Z 270DEG 66KT 4187 9308 4121 9309 

$$

IAC039-099-117-123-125-135-153-157-181-160130-
/O.CON.KDMX.SV.W.0129.000000T0000Z-211216T0130Z/
Monroe IA-Lucas IA-Poweshiek IA-Polk IA-Marion IA-Mahaska IA-
Jasper IA-Clarke IA-Warren IA-
648 PM CST Wed Dec 15 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 730 PM CST
FOR NORTHWESTERN MONROE...NORTHERN LUCAS...WESTERN POWESHIEK...
EASTERN POLK...MARION...WESTERN MAHASKA...JASPER...NORTHEASTERN
CLARKE AND EASTERN WARREN COUNTIES...

At 648 PM CST, severe thunderstorms were located along a line
extending from near Baxter to 7 miles south of Knoxville, moving east
at 75 mph.

HAZARD...70 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Expect considerable tree damage. Damage is likely to mobile 
         homes, roofs, and outbuildings.

Locations impacted include...
  Rock Creek Lake.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Tornado Watch remains in effect until 800 PM CST for south central
and central Iowa.

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

&&

LAT...LON 4109 9365 4186 9347 4186 9254 4108 9281
TIME...MOT...LOC 0048Z 270DEG 66KT 4187 9308 4121 9309 

THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...70 MPH

$$

Martin

635 
WWUS53 KDMX 160110
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
710 PM CST Wed Dec 15 2021

IAC039-153-181-160120-
/O.CAN.KDMX.SV.W.0129.000000T0000Z-211216T0130Z/
Polk IA-Clarke IA-Warren IA-
710 PM CST Wed Dec 15 2021

...THE SEVERE THUNDERSTORM WARNING FOR EASTERN POLK...NORTHEASTERN
CLARKE AND EASTERN WARREN COUNTIES IS CANCELLED...

The storms which prompted the warning havemoved out of the warned 
area. Therefore, the warning has been cancelled.

A Tornado Watch remains in effect until 800 PM CST for central and
south central Iowa.

LAT...LON 4109 9331 4185 9315 4186 9254 4108 9281
TIME...MOT...LOC 0110Z 267DEG 66KT 4189 9255 4123 9257 

$$

IAC099-117-123-125-135-157-160130-
/O.CON.KDMX.SV.W.0129.000000T0000Z-211216T0130Z/
Monroe IA-Lucas IA-Poweshiek IA-Marion IA-Mahaska IA-Jasper IA-
710 PM CST Wed Dec 15 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 730 PM CST
FOR NORTHWESTERN MONROE...NORTHEASTERN LUCAS...WESTERN POWESHIEK...
MARION...WESTERN MAHASKA AND JASPER COUNTIES...

At 710 PM CST, severe thunderstorms were located along a line
extending from near Tama to near Oskaloosa, moving east at 75 mph.

HAZARD...70 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Expect considerable tree damage. Damage is likely to mobile 
         homes, roofs, and outbuildings.

Locations impacted include...
Newton, Pella, Grinnell, Knoxville, Monroe, Melcher-Dallas, Baxter,
Iowa Speedway, Knoxville Raceway, Lake Red Rock, Rock Creek Lake,
Sully, Kellogg, Lovilia, Bussey, Lynnville, Harvey, Lambs Grove,
Leighton and Oakland Acres.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Tornado Watch remains in effect until 800 PM CST for central and
south central Iowa.

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

&&

LAT...LON 4109 9331 4185 9315 4186 9254 4108 9281
TIME...MOT...LOC 0110Z 267DEG 66KT 4189 9255 4123 9257 

THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...70 MPH

$$

Martin

The office that day

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

Issued	Product	Office	Counties	Lasted
Dec 15, 6:13 PM CST	Severe Thunderstorm Warning	DMX	Appanoose, Clarke, Decatur, Lucas, Marion, Monroe and 2 more	62 min
Dec 15, 6:19 PM CST	Tornado Warning	DMX	Hancock, Kossuth, Winnebago	41 min
Dec 15, 6:30 PM CST	Severe Thunderstorm Warning Considerable damage threat	DMX	Black Hawk, Bremer, Butler, Cerro Gordo, Franklin, Grundy and 6 more	75 min
Dec 15, 6:37 PM CST	Tornado Warning	DMX	Butler, Cerro Gordo, Franklin	20 min
Dec 15, 6:47 PM CST	Severe Thunderstorm Warning Considerable damage threat	DMX	Grundy, Hardin, Marshall, Story	43 min
Dec 15, 7:09 PM CST	Severe Thunderstorm Warning Considerable damage threat	DMX	Appanoose, Davis, Jasper, Lucas, Mahaska, Marion and 5 more	66 min
Dec 15, 7:44 PM CST	Severe Thunderstorm Warning Considerable damage threat	DMX	Black Hawk, Bremer, Butler, Grundy, Tama	27 min
Dec 15, 11:52 PM CST	Wind Advisory	DMX	Adair, Adams, Appanoose, Audubon, Black Hawk, Boone and 45 more	6 hr

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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.