A mid-level trough across the northern plains allowed for a region of broad ascent to support scattered convection across the area on the morning of June 26th. This activity remained sub-severe with the exception of a suspected microburst on the south side of the Des Moines metro which resulted in significant tree damage and power outages.
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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 mid-level trough across the northern plains allowed for a region of broad ascent to support scattered convection across the area on the morning of June 26th. This activity remained sub-severe with the exception of a suspected microburst on the south side of the Des Moines metro which resulted in significant tree damage and power outages. As the trough pushed east a surface boundary moved across the state later in the day. While this also remained sub-severe, localized pockets of heavy rain did develop.
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 26, 1:53 AM CST, 3 hours 7 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 253 AM CDT Fri Jun 26 2020 .DISCUSSION.../Today through Thursday/ Issued at 253 AM CDT Fri Jun 26 2020 A broad mid-level trough is scooting quickly eastward across the northern High Plains early this morning, with an attendance surface front moving through the Dakotas. The region of broad ascent on the leading flank of the broad trough has supported the development of areas and clusters of thunderstorms across much of the region to our north and west, with a few storms impacting our northern counties overnight. As the trough moves quickly over Minnesota and Wisconsin today the surface front will push into our forecast area, then further southeast into Missouri and Illinois tonight. Though the strongest dynamical forcing associated with the mid-level system will pass to our north during the day, by late afternoon and evening we will still reside beneath sufficient, through certainly modest, flow and shear fields considering the strong instability expected to develop along and south of the surface boundary. This should result in robust updraft development once convective initiation occurs, with strong to severe thunderstorms breaking out along the boundary. At this time short-term trends and CAMs place highest confidence in initiation from our northeastern through central counties around 21-23Z, with storms and the boundary in general showing a progressive east/southeastward motion through the evening and into tonight. Given the very strong instability but unimpressive deep- layer shear or surface flow/convergence tornadoes are unlikely, however isolated large hail and small swaths of damaging wind will be quite possible. This threat will diminish tonight as instability diminishes and the boundary pushes southeastward out of our area. The other threat to consider this afternoon and evening is heavy rainfall. While the surge of low-level moisture today and resulting PWATs by this evening certainly support some intense rainfall rates, these should be spotty due to the scattered nature of the strongest storms, and with the system/storms being pretty progressive will be mitigated further. There is a threat for flash flooding particularly if intense updrafts reside over urban/flood prone areas, or affect areas in our northeastern counties that received very heavy rainfall a few days ago and are still saturated. However, given the conditional and limited nature of this flash flooding threat, have eschewed a watch at this time and will handle with warnings later today if needed. Saturday will be a relatively nice day for most of Iowa, with a weak surface high pressure area sliding by to the north and providing mostly sunny skies and mild temperatures, though surface dewpoints will make for a pretty humid day especially compared with the more pleasant levels experienced for the last several weeks. A possible exception to a quiet Saturday will be in southern Iowa, nearer the surface boundary and beneath the sloped frontal surface aloft, where instability may support development of widely scattered showers and storms in the afternoon and evening. These should be spotty and of little to no impact given the lack of upper-level support or shear, but justify carrying low POPs roughly south of I-80 Saturday afternoon. All in all, however, those wishing to engage in outdoor activities without a high rain/thunderstorm concern would do well to take advantage of the brief respite Saturday. From Sunday onward the forecast is...problematic to say the least. As has been advertised for the last couple days, the synoptic pattern becomes very messy for most or possibly all of next week. A large 500 mb trough will set up over the western U.S. and Rockies on Sunday and Monday, even as a deep-layer ridge builds over the eastern half or two thirds of the country. The resulting blocking pattern will result in no discernible change in large- scale weather patterns through at least next Thursday and possibly beyond. Within this more or less steady-state regime we will see subtle impulses ejected out of the western trough become trapped beneath the developing ridge and wobble around the Midwest erratically and unpredictably. Overall this will allow the old, decayed frontal boundary left over from today/tonight to retreat northward and wobble around Iowa for multiple days, with periodic thunderstorm chances likewise cropping up in various times and areas, but with little to no ability to predict at this range. The result is four days of chance POPs across the entire forecast area, slightly higher in the afternoon and evening hours associated with diurnal peak heating. There will be a non-zero severe weather and heavy rainfall threat with the storms overall, but it should be mitigated by the lack of strong upper-level support or flow fields beneath the large ridging pattern. Aside from the prolonged POPs, next week will also be quite muggy and sweaty given the warm advection associated with the initial development of the ridging pattern and weak flow fields/intermittent rains thereafter. && .AVIATION.../For the 06Z TAFS through 06Z Friday night/ Issued at 1048 PM CDT Thu Jun 25 2020 Low-level jet is developing and is resulting in isolated thunderstorms in northwestern Iowa. Overnight, expecting showers and isolated thunderstorms to move west to east across the northern third of the state. Cloud cover continues to increase, but cloud bases expected to remain at VFR. There may be a brief period with an isolated shower that the CIGs drops to MVFR. More thunderstorms are expected Friday afternoon. Overall busy TAF period with shower and thunderstorm activity. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && DISCUSSION...Lee AVIATION...Krull
Hazardous Weather Outlook National Weather Service Des Moines IA 347 AM CDT Fri Jun 26 2020 IAZ039-270900- Black Hawk- 347 AM CDT Fri Jun 26 2020 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Scattered thunderstorms are expected today with a few severe storms possible with large hail and damaging winds the primary hazards. Locally heavy rainfall may also occur. River Flood Warnings are in effect for portions of Black Hawk Creek, Cedar River, and Iowa River. Please refer weather.gov/desmoines for further details. .DAYS TWO THROUGH SEVEN...Saturday through Thursday River flooding may continue through the week. Periodic chances for thunderstorms are in the forecast through much of the period. A few severe storms may occur. .SPOTTER INFORMATION STATEMENT... Spotter reports may be needed on today. Rainfall reports are always appreciated. IAZ004>007-015>017-023>028-033>038-044>050-057>062-070>075- 081>086-092>097-270900- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun- Webster-Hamilton-Hardin-Grundy-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- 347 AM CDT Fri Jun 26 2020 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Scattered thunderstorms are expected today with a few severe storms possible with large hail and damaging winds the primary hazards. Locally heavy rainfall may also occur. .DAYS TWO THROUGH SEVEN...Saturday through Thursday Periodic chances for thunderstorms are in the forecast through much of the period. A few severe storms may occur. .SPOTTER INFORMATION STATEMENT... Spotter reports may be needed on today. Rainfall reports are always appreciated.
The Des Moines radar (KDMX), 22 km away, was scanning. The volume nearest the first event began at 10:57 UTC.
1 thunderstorm wind, 1 heavy rain. Local standard time, as filed.
Public reports of large tree limbs down across the area, some large enough to fold a chain link fence. Thousands were without power, which was restored by 830a. Radar data indicates likely microburst.
Public report from Albia of 4.37 inches of rain between 745p and 11p with heavy rain still falling at time of report.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2020Every state in 2020This day in weather historyWarnings in Iowa, June 2020
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: 896296, 896297.