Thunderstorms developed during the early evening hours of March 23rd ahead of an approaching low pressure system. The overall severe threat was low and conditional based on whether clearing of cloud cover would occur and allow for generation of instability in conjunction with increasing warm air advection across southern Iowa.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS DMX wrote it up.
Thunderstorms developed during the early evening hours of March 23rd ahead of an approaching low pressure system. The overall severe threat was low and conditional based on whether clearing of cloud cover would occur and allow for generation of instability in conjunction with increasing warm air advection across southern Iowa. Thunderstorms developed along the warm front and displayed broad rotation, however no tornadoes occurred. The only damage occurred with a storm in Wapello county associated with brief strong wind gusts.
The local office's own words before the first event, 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 the first event at Mar 23, 5:45 PM CST, 1 minute earlier.
Area Forecast Discussion National Weather Service Des Moines IA 645 PM CDT Tue Mar 23 2021 ...Updated for 00z Aviation... .DISCUSSION.../Tonight through Tuesday/ Issued at 251 PM CDT Tue Mar 23 2021 Forecast highlights: -Marginal Risk south today -Breezy Wednesday -Peppered rain chances late in the week into the weekend This afternoon and tonight...a short window for any storms and thus severe potential across southern Iowa. Some breaks in the clouds have allowed for some instability to build across southern Iowa and as of 245 PM, there is a weak area of convection moving north in from Missouri. MUCAPE values have increased to around 500 J/kg as well as surface based CAPE. The low level shear remains decent with 0-1km and 0-3km bulk shear at 20-25 knots and 20-30 knot respectively. The 0-1km helicity ranges from 100-150 m2/s2 along and south of Highway 34 with LCL heights of 500-750m. Certainly with the decent shear across the south and some buoyancy trying to develop as this ribbon of convection moves northward this afternoon, can't completely rule out the potential for a brief tornado and possibly some hail to develop if an updraft gets going. However, any severe and even storm threat is completely sunshine dependent and expect the threat to cease by 00z or even sooner. Wednesday into Saturday...CAA develops by Wednesday morning and continues throughout the day providing a fairly brisk March day as low cloud cover sticks around as well. Winds look to gust to 25-30 knots throughout the day and with the stubborn cloud cover, temperatures should remain generally in the 40s north and lower 50s south. Although the lower 50s seem slightly too warm in the south given the cloud cover and decent CAA. Another shortwave will track across the Ozarks Thursday into Friday but the latest ECMWF and GFS suggest any precipitation chances to remain in the southeast. Yet another shortwave brings rain chances late Friday night into Saturday morning and models have come into a bit better agreement with timing and placement of QPF. The ECMWF is still further south than GFS, but confidence is increasing with at least some lighter rain by the overnight hours Friday night into Saturday morning. Sunday through Tuesday...High pressure builds into the region and provides a fairly quiet period of weather. The ECMWF is a bit more intense with the WAA developing on Monday, but the signal is there for good warm and breezy day and possibly some storms over the west as a surface low pressure and upper trough dig into the central plains Monday into Tuesday. Something to monitor for severe weather potential if the timing is right. && .AVIATION.../For the 00Z TAFS through 00Z Wednesday evening/ Issued at 644 PM CDT Tue Mar 23 2021 MVFR cigs to localized IFR pockets across the state this evening with a large precipitation shield expanding from the south. Visibility within precipitation may drop to around 3 miles. Rain will taper off by early morning with gusty south winds through much of the afternoon. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && DISCUSSION...Podrazik AVIATION...Hagenhoff
Hazardous Weather Outlook National Weather Service Des Moines IA 315 PM CDT Tue Mar 23 2021 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-242015- 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- 315 PM CDT Tue Mar 23 2021 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...This afternoon and tonight Scattered thunderstorms are passing or will pass over south central Iowa this afternoon and early this evening. A few of the storms could become severe with hail up to nickel size and possibly a brief tornado. .DAYS TWO THROUGH SEVEN...Wednesday through Monday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotters activation is possible in southern Iowa this afternoon. Ansorge
Special Weather Statement
National Weather Service Des Moines IA
641 PM CDT Tue Mar 23 2021
IAZ062-075-240045-
Poweshiek IA-Mahaska IA-
641 PM CDT Tue Mar 23 2021
...Strong Winds Possible over East Central Iowa Early this Evening...
At 639 PM CDT, Doppler radar was tracking showers and a few
thunderstorms with strong winds 8 miles east of New Sharon, or 9
miles south of Montezuma, moving north at 25 mph.
Wind gusts up to 55 mph will be possible with this storm. At 615 pm,
a 51 mph gust was reported at Oskaloosa.
Locations impacted include...
Grinnell, Montezuma, Brooklyn, New Sharon, Victor, Holiday Lake,
Malcom, Deep River, Barnes City, Searsboro, Hartwick, Guernsey and
Grinnell Regional Airport.
LAT...LON 4151 9241 4138 9241 4143 9278 4151 9278
4151 9276 4160 9276 4160 9277 4186 9276
4186 9230 4151 9230
TIME...MOT...LOC 2339Z 183DEG 23KT 4144 9250
SmallThe Des Moines radar (KDMX), 123 km away, was scanning. The volume nearest the first event began at 23:49 UTC.
1 thunderstorm wind. Local standard time, as filed.
County Emergency Manager reported damage to out buildings and minor house damage along 160th Street north of Ottumwa.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2021Every state in 2021This day in weather historyWarnings in Iowa, March 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 948189.