Alert archive / Iowa / Severe Thunderstorm Warnings in 2023

Severe Thunderstorm Warning 129, NWS Des Moines, IA

July 12, 20234 counties in Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Jul 12, 2023, 1:00 AM CDT for 4 counties in Iowa. It was in force for 45 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jul 12, 2023, 1:00 AM CDT (06:00 UTC)
Expired: Jul 12, 2023, 1:45 AM CDT
In force: 45 min
Issued by: NWS Des Moines, IA
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

Counties Jasper County, IA, Marshall County, IA, Polk County, IA, Story County, IA

The radar

The Des Moines radar (KDMX), 40 km from the middle of the area, began a volume at 06:03 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 nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 6.0 hours before the alert went out and 232 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: 1405 J/kg
Mixed-layer CIN: -19 J/kg
Mixed-layer LCL: 1268 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 29 m²/s²
0-3 km storm-relative helicity: 101 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 2.8

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Des Moines, IA wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 12, 12:29 AM CDT, 31 minutes earlier.

Area forecast discussion, Jul 12, 12:29 AM CDT, 31 minutes before

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Hazardous weather outlook, Jul 11, 3:10 PM CDT, 9 hours 50 minutes before

Hazardous Weather Outlook
National Weather Service Des Moines IA
310 PM CDT Tue Jul 11 2023

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-122015-
Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo-
Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun-
Webster-Hamilton-Hardin-Grundy-Black Hawk-Crawford-Carroll-Greene-
Boone-Story-Marshall-Tama-Audubon-Guthrie-Dallas-Polk-Jasper-
Poweshiek-Cass-Adair-Madison-Warren-Marion-Mahaska-Adams-Union-
Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne-
Appanoose-Davis-
310 PM CDT Tue Jul 11 2023

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

Strong to severe thunderstorms are possible late tonight. The
main hazards will be damaging wind gusts, though hail and locally
heavy rainfall are also possible. A tornado or two cannot be ruled
out in far southern Iowa.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

The threat for severe weather continues into early Wednesday
morning with a continued threat of damaging winds, hail, and
locally heavy rainfall.

Additional storm chances will return late in the week, although
the severe potential will need to be refined in the coming days.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed tonight into Wednesday.

In the hours before

Special weather statement, Jul 12, 12:13 AM CDT, 47 minutes before

Special Weather Statement
National Weather Service Des Moines IA
1213 AM CDT Wed Jul 12 2023

IAZ047-048-059-060-120600-
Story IA-Boone IA-Polk IA-Dallas IA-
1213 AM CDT Wed Jul 12 2023

...A strong thunderstorm will impact portions of northern Polk,
southern Story, southeastern Boone and northeastern Dallas Counties
through 100 AM CDT...

At 1213 AM CDT, Doppler radar was tracking a strong thunderstorm over
Big Creek Lake, or 10 miles north of Johnston, moving east at 25 mph.

HAZARD...Penny size hail.

SOURCE...Radar indicated.

IMPACT...Minor damage to outdoor objects is possible.

Locations impacted include...
Ankeny, Bondurant, Polk City, Huxley, Madrid, Slater, Granger,
Woodward, Big Creek Lake, Saylorville Lake, Maxwell, Cambridge,
Elkhart, Alleman, Sheldahl and Big Creek State Park.

This includes Interstate 35 between mile markers 92 and 107.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4186 9333 4186 9335 4169 9335 4175 9388
      4189 9403 4196 9333
TIME...MOT...LOC 0513Z 272DEG 20KT 4184 9377

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...<30 MPH

Small

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 12, 12:13 AM CDT	Special Weather Statement	DMX	Polk	47 min
Jul 12, 2:46 AM CDT	Special Weather Statement	DMX	Lucas	44 min
Jul 12, 3:05 AM CDT	Severe Thunderstorm Warning	DMX	Lucas, Mahaska, Marion, Monroe	55 min
Jul 12, 5:17 AM CDT	Severe Thunderstorm Warning	DMX	Hancock, Wright	16 min
Jul 12, 5:40 AM CDT	Severe Thunderstorm Warning	DMX	Boone, Dallas, Polk, Story	50 min
Jul 12, 5:55 AM CDT	Flash Flood Warning	DMX	Boone, Greene	6 hr
Jul 12, 6:07 AM CDT	Severe Thunderstorm Warning Considerable damage threat	DMX	Audubon, Carroll, Cass, Crawford, Sac	38 min
Jul 12, 6:41 AM CDT	Severe Thunderstorm Warning Considerable damage threat	DMX	Adair, Adams, Audubon, Cass, Crawford, Guthrie and 3 more	64 min
Jul 12, 7:22 AM CDT	Severe Thunderstorm Warning	DMX	Adair, Clarke, Decatur, Madison, Ringgold, Taylor and 1 more	38 min
Jul 12, 7:41 AM CDT	Severe Thunderstorm Warning	DMX	Adair, Boone, Clarke, Dallas, Madison, Polk and 3 more	39 min
Jul 12, 7:47 AM CDT	Severe Thunderstorm Warning	DMX	Jasper, Mahaska, Poweshiek	43 min
Jul 12, 7:59 AM CDT	Severe Thunderstorm Warning	DMX	Appanoose, Clarke, Decatur, Lucas, Monroe, Ringgold and 1 more	46 min
Jul 12, 8:18 AM CDT	Severe Thunderstorm Warning	DMX	Jasper, Marshall, Polk, Poweshiek, Story, Tama	42 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2023 Every severe thunderstorm warning in 2023

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.