A descending frontal boundary into northern Iowa interacted with unstable conditions characterized by MLCAPE values around 1000 J/kg, 40+ knots of 0-6km shear, steep low level lapse rates, and DCAPE values between 1000-1400 J/kg. This resulted in a cluster of showers and storms to develop into the afternoon that produced at least one report of wind damage in Worth County.
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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.
A descending frontal boundary into northern Iowa interacted with unstable conditions characterized by MLCAPE values around 1000 J/kg, 40+ knots of 0-6km shear, steep low level lapse rates, and DCAPE values between 1000-1400 J/kg. This resulted in a cluster of showers and storms to develop into the afternoon that produced at least one report of wind damage in Worth County.
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 Jun 12, 11:47 AM CST, 35 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Des Moines IA 1247 PM CDT Wed Jun 12 2024 ...Updated for the 18z Aviation Discussion... .KEY MESSAGES... - Several opportunities for thunderstorms through tomorrow. Most noted this afternoon and evening north, and again Thursday afternoon and evening south. Slight Risk (2/5) of severe weather for both of those windows. - Elevated heat and humidity approaching advisory criteria south half Thursday. Additional heat concerns next week Sun-Tue. - Dry Friday, then intermittent chances for showers & storm Fri night into early next week && .DISCUSSION... Issued at 400 AM CDT Wed Jun 12 2024 A fairly typical summer-like pattern will be in place through this forecast period (into early next week) as IA remains between an active northern CONUS jet and progressive upper level ridging. This will result in seasonal to above normal warmth and humidity and varied thunderstorm chances for an extended period. Our weather was largely inactive early this morning, although our attention will turn toward slowly expanding convection from MT into the Dakotas. This will continue through the day and expand eastward driven by lift and theta-e advection ahead of the US/Canadian border upper trough. Increasing instability across the High Plains is expected to expand into MN ahead of an approaching frontal boundary. The 03Z extended RAP suggests 2-3K J/kg MLCAPEs into MN, but lesser values +/- 1000 J/kg farther south into northern IA. 00Z HREF members are in fairly good agreement with generally elevated convection advecting and/or expanding into northern IA late morning through the afternoon and early evening, with additional storms ignited by low level convergence along the front possibly following close behind. Forecast soundings in the airmass across northern IA depict very summer-like and warm inverted-V soundings with fairly steep low level lapse rates. 0-6km shear of 40+kts with favorable NW-SE orientation, elongated hodographs, and the steep lapse rates with 1000-1400 J/kg DCAPEs all support a risk of damaging wind and large hail in the Slight Risk area, especially if storm become rooted lower and more surface based with time. The heavy rain potential appears to have diminished somewhat from this time yesterday with 00Z HREF 2"+ probabilities much less, now <30%. Temp wise, the NBM was around ~4F too cool yesterday so boosted temps further to higher percentiles today and tomorrow, at or approaching 90th percentile of 00z MOS and deterministic guidance, and there is some concern that may even not be sufficient. There should be a relative lull overnight into early Thursday morning, but lingering mid level forcing in the left entrance region of the jet segment approaching the Great Lake will keep chances for weaker convection into the morning north. By afternoon the associated frontal boundary should be sagging southward through the forecast area with our attention turning to southern IA. The warm sector ahead of the front should see highs in the mid 90s, and with 65-70F dewpoints conditions approaching Heat Advisory criteria will be in place as heat indices reach 100F in a few spots, and Wet Bulb Globe Temperature (WBGT) Risk reaches High and isolated Extreme levels, 3 and 4 of 4 risk levels respectively. 00Z HREF ARW core HRW ARW and HRRR members are quite aggressive developing a strong MCS across southern IA during peak heating tomorrow afternoon. Recent RAP and HRRR extended runs both have been consistent depicting 2-3K J/kg, low inhibition MLCAPEs driven by 65-70F surface dewpoints: higher than today. With 40+kts of deep shear and four figure DCAPEs large hail and damaging winds will again be possible. Although the low level kinematics are weak, an isolated more thermodynamically driven tornado cannot be ruled out considering the degree of instability. 00Z HREF strong wind probabilities are fairly high across southern IA, and 00Z and 06Z HRRR runs have both depicted a small cluster of storms with significant wind potential (gusts 60+kts) somewhere in the vicinity of our far SE corner into DVN's eastern IA counties. Would not be surprised to see SPC raise severe weather probabilities for those areas later today or heading into tomorrow. Any precip potential should exit south and east overnight into Fri morning as the front exits, leading to fair weather and seasonal temperatures for a brief break. It won't last long however with off and on thunderstorm chances starting Friday night and lasting through the remainder of the period into early next week. Lift ahead of a Rockies short wave will start by then, and continue through its passage later in the weekend, and then persistent southwest flow will follow ahead of a northern Plains trough into Tuesday. Iowa should be into the warm sector starting Sunday with highs and heat indices often in the 90s. The WBGT Risk categories seem a bit more tempered in this range however, often no worse than Moderate (2/4) south half, likely due to breezy winds at times. Seasonal to occasional plus climatology moisture parameter space suggests locally heavy rains may be possible at times from the weekend into early next week, with windows of concern over the weekend along and ahead of the aforementioned drifting short wave, and along a slow moving frontal boundary which appears to be late Tuesday at this lead time. There will be some severe weather potential considering the instability driven by a seasonally warm and humid airmass, but weak shear in upper ridging may temper that a bit. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1247 PM CDT Wed Jun 12 2024 Scattered showers and thunderstorms will pass across the area early this afternoon in northern Iowa with impacts to KFOD/KMCW/KALO. Showers are producing stronger gusts around 40-45 kts in additional to background breezy winds gusting 20-30 kts. A secondary line of storms is possible north late tonight, though confidence is much lower. Any impacts would mainly develop at KMCW if this line develops. More robust storms possible tomorrow evening near KOTM. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && DISCUSSION...Small AVIATION...Hagenhoff
Hazardous Weather Outlook National Weather Service Des Moines IA 415 AM CDT Wed Jun 12 2024 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-130915- 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- 415 AM CDT Wed Jun 12 2024 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Strong to severe storms are possible, especially over northern and possibly central Iowa this afternoon to evening. Damaging winds and hail are the main threats, though a tornado or two cannot be ruled out. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday Additional storms are forecast Thursday, with strong to severe storms possible in portions of southern and eastern Iowa in the afternoon to evening. Active weather is expected to continue this weekend and into early next week with multiple chances for showers and storms. More details regarding timing and severe potential will be better known in the coming days. Heat will continue to build today and into the weekend with heat index values in the upper 90s in southern Iowa by Thursday, as well as on Sunday and Monday. Otherwise, outside of Friday, temperatures in the upper 80s to mid 90s are generally expected. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed at various times this week and weekend.
Special Weather Statement National Weather Service Des Moines IA 1235 PM CDT Wed Jun 12 2024 IAZ004>007-015>017-023>025-033>035-044>046-057-058-121915- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas-Humboldt-Wright-Sac-Calhoun-Webster-Crawford-Carroll- Greene-Audubon-Guthrie- Including the cities of Estherville, Algona, Forest City, Lake Mills, Northwood, Manly, Emmetsburg, Garner, Britt, Kanawha, Mason City, Clear Lake, Pocahontas, Laurens, Rolfe, Fonda, Gilmore City, Humboldt, Eagle Grove, Clarion, Belmond, Sac City, Lake View, Odebolt, Wall Lake, Schaller, Early, Rockwell City, Manson, Lake City, Pomeroy, Fort Dodge, Denison, Carroll, Jefferson, Audubon, Exira, Guthrie Center, Panora, Bayard, and Casey 1235 PM CDT Wed Jun 12 2024 ...Gusty Winds up to around 50 mph Possible with High Based Rain Showers and Storms... WHAT...Brief gusty winds up to and in excess of 50 mph may be experienced with high based showers and thunderstorms. WHERE...Much of northern and western Iowa WHEN...Now until 215 PM IMPACTS...Small branches may be damaged and loose objects may be blown around. PREPAREDNESS AND PRECAUTIONARY ACTIONS...If outdoors, consider seeking shelter inside a building. Dodson
The Minneapolis radar (KMPX), 159 km away, was scanning. The volume nearest the first event began at 18:19 UTC.
1 thunderstorm wind. Local standard time, as filed.
Reports of trees and powerlines down in Northwood. Time of occurrence estimated from radar.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2024Every state in 2024This day in weather historyWarnings in Iowa, June 2024
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: 1190288.