Alert archive / Iowa / Severe Thunderstorm Warnings in 2023

Severe Thunderstorm Warning 137, NWS Des Moines, IA

July 12, 2023Jasper County, Mahaska County, Poweshiek County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Jul 12, 2023, 7:47 AM CDT for Jasper County, Mahaska County, Poweshiek County, Iowa. It was in force for 43 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, 7:47 AM CDT (12:47 UTC)
Expired: Jul 12, 2023, 8:30 AM CDT
In force: 43 min
Issued by: NWS Des Moines, IA
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

Counties Jasper County, IA, Mahaska County, IA, Poweshiek County, IA

The radar

The Des Moines radar (KDMX), 83 km from the middle of the area, began a volume at 12:46 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
Jul 12, 5:15 AM CDT	Severe Thunderstorm Watch	SPC	6 hr

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 0.8 hours before the alert went out and 187 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: 9 J/kg
Mixed-layer CIN: -301 J/kg
Mixed-layer LCL: 936 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 48 m²/s²
0-3 km storm-relative helicity: 252 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.4

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, 6:24 AM CDT, 1 hour 23 minutes earlier.

Area forecast discussion, Jul 12, 6:24 AM CDT, 1 hour 23 minutes before

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Hazardous weather outlook, Jul 12, 3:04 AM CDT, 4 hours 43 minutes before

Hazardous Weather Outlook
National Weather Service Des Moines IA
304 AM CDT Wed Jul 12 2023

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-130815-
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-
304 AM CDT Wed Jul 12 2023

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and Tonight

Strong to severe thunderstorms are possible early this morning.
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...Thursday through Monday

Additional storm chances will continue on and off for the
remainder of the work week with the next best chance on Friday. The
severe potential will need to be refined in the coming days.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this morning.

In the hours before

Special weather statement, Jul 12, 2:46 AM CDT, 5 hours 1 minute before

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

IAZ073-074-084-085-120830-
Marion IA-Lucas IA-Monroe IA-Warren IA-
246 AM CDT Wed Jul 12 2023

...A strong thunderstorm will impact portions of northeastern Lucas,
northwestern Monroe, southern Marion and southeastern Warren Counties
through 330 AM CDT...

At 245 AM CDT, Doppler radar was tracking a strong thunderstorm near
Melcher-Dallas, or 13 miles southwest of Knoxville, moving east at 30
mph.

HAZARD...Winds in excess of 30 mph and penny size hail and
         additional rainfall up to one inch.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible. Ponding of water on roadways, low visibilities,
         and rises in small streams and creeks.

This strong thunderstorm will be near...
  Melcher-Dallas around 255 AM CDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4120 9348 4130 9345 4127 9296 4107 9302
TIME...MOT...LOC 0745Z 281DEG 26KT 4122 9333

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

REV

Special weather statement, Jul 12, 4:59 AM CDT, 2 hours 48 minutes before

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

IAZ046>049-058>061-121200-
Greene-Boone-Story-Marshall-Guthrie-Dallas-Polk-Jasper-
Including the cities of Jefferson, Boone, Ames, Marshalltown,
Guthrie Center, Panora, Bayard, Casey, Perry, Waukee, Adel,
Des Moines, and Newton
459 AM CDT Wed Jul 12 2023

...Thunderstorms With Heavy Rainfall and Gusty Winds...

An area of thunderstorms with moderate to heavy rainfall up to 1
to 2 inches will be moving into central Iowa over the next 2 to 3
hours. This area of thunderstorms will impact the Highway 30
corridor as well as the Interstate 35 corridor between Ames and
Des Moines from now until 7 am. As it sags south across the
region, it will also affect the I80 corridor between 6 and 8 am.

Persons traveling this morning should be alert to rapidly changing
visibility in locally heavy rainfall as well as ponding of water
on roadways which may lead to difficulty traveling during the
rush hour period of 5 to 8 am. Wind gusts of 35 to 40 mph may also
occur with this area of thunderstorms.

Additionally, another area of strong thunderstorms is expected to
move into western to central Iowa between 7 and 11 am this
morning.

REV

Local storm report, Jul 12, 6:45 AM CDT, 1 hour 2 minutes before

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Local storm report, Jul 12, 7:04 AM CDT, 43 minutes before

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Local storm report, Jul 12, 7:19 AM CDT, 28 minutes before

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Local storm report, Jul 12, 7:22 AM CDT, 25 minutes before

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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, 1:00 AM CDT	Severe Thunderstorm Warning	DMX	Jasper, Marshall, Polk, Story	45 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, 7:59 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.