Overnight convection across the central plains moved into Iowa during the early morning hours of June 28th. While storms had diminished in strength, a damaging wind gust did occur.
Every event with a place to put it. Tap one for its entry below.
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.
Overnight convection across the central plains moved into Iowa during the early morning hours of June 28th. While storms had diminished in strength, a damaging wind gust did occur. The precipitation associated with this mesoscale convective vortex continued to weaken through the morning, however, the environment in its wake exhibited high low-level vorticity that supported funnel cloud development later in the day.
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 28, 2:50 AM CST, 1 hour 33 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 350 AM CDT Sun Jun 28 2020 .DISCUSSION.../Today through Saturday/ Issued at 347 AM CDT Sun Jun 28 2020 Summary... After morning showers/storms, renewed potential for strong/severe storms over portions of NW/N Iowa this evening, including potential for large hail, damaging winds, and a tornado or two. Relatively persistent POPs continue through much of the forecast, along with warm/hot and humid conditions. Today and Tonight... Sounding a bit like a broken record, main issues today will revolve around convective initiation, evolution, and timing both this morning and again in the evening. The initial round of showers/storms currently resides in areas of central/southern Nebraska and northern Kansas. Aided by the LLJ and an established cold pool, activity will continue to slide to the E/NE. A number of wind reports have been associated with these storms, as well as some isolated severe hail with cores ahead of the primary line. The activity will continue into the state and CWA around/after 09-10z, but should see a degree of weakening as it enters less supportive thermodynamic and shear environment. The HRRR and RAP have been consistent in recent runs depicting weakening as it progresses into/across the area. That being said, best opportunity for strong/severe will exist in SW/S areas, with main threat for strong/damaging winds. This afternoon/evening will be another opportunity for strong/severe storms as the parent short wave responsible for the showers this morning tracks NE across NE Nebraska, NW Iowa, and S Minnesota. HRRR runs overnight have been consistent in initiating storms around/after 16-17z in NW Iowa, growing upscale while tracking into Minnesota. The 00z and 06z extended HRRR runs have both depicted rapid MCS development tonight as cold pools establish themselves around the Twin Cities area turning/tracking to the SE, riding along the general MUCAPE gradient and/or any lingering weak boundaries and potentially clipping portions of the N/NE CWA. Stepping back a second to initial development this afternoon, with continuing theta-e/moisture advection the environment will be highly unstable around/greater than 5000 J/kg SBCAPE and eventually uncapped. Additionally, around 30 kts 0-3km bulk shear and low level veering with height will help support the potential for organized convection. As a result, all modes of severe weather will be possible prior to anticipated upscale growth later in the event. The current SPC Day 1 Slight Risk is reasonable, especially given some lingering uncertainty in evolution and how the morning activity may influence the area. Monday through Saturday... Not much discernible change from previous forecast iterations here. The large scale pattern continues to call for Omega block look with amplified central US ridging as western US trough digs in and Quebec cut off low slides into New England. The guarantee through the forecast continues to be for warm/hot and humid conditions to prevail, including highs predominantly in the mid 80s to low 90s, lows in the low 70s, and dew points often in the lower 70s. With heat index values into the 90s/near 100 through much of the week, concerns continue for heat related issues for those spending extended periods of time outside or those that have limited or no access to air conditioning. On the precipitation side of the forecast, POPs inevitably continue to be overdone temporally. With POP chances hinging on short waves within this sort of pattern, it is not surprising to see high variance in the synoptic guidance. As has been messaged in previous forecast packages, POP refinement and strong/severe potential will most likely only be within about 24 hours of any given wave/event. && .AVIATION.../For the 06Z TAFS through 06Z Sunday night/ Issued at 1142 PM CDT Sat Jun 27 2020 Any aviation impacts in the current TAF period will be largely limited to conditions in and near thunderstorms. One round of storms may affect some of the terminals later Sunday morning, between about 14-18Z, and have indicated VCTS accordingly with details of timing and impacts still unclear. There is also a possibility of a second round of storms on Sunday evening/night, beginning closest to FOD around 00Z, but with confidence low and in the outer periods of the TAF, have only included VCTS there and at MCW for now and will refine/expand in later issuances. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && DISCUSSION...Curtis AVIATION...Lee
Hazardous Weather Outlook National Weather Service Des Moines IA 310 AM CDT Sun Jun 28 2020 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-290815- 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 AM CDT Sun Jun 28 2020 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Thunderstorms are expected over central and southern Iowa this morning. A few severe storms are possible with the primary threat being quarter sized hail and 60 mph winds. Additional storms are expected later this afternoon and evening mainly over the northern half of the state. Again, a few severe storms are possible with large hail, damaging winds and isolated tornadoes. Locally heavy rainfall may also occur. .DAYS TWO THROUGH SEVEN...Monday through Saturday Periodic thunderstorm chances continue this week though not all locations will have precipitation each day. The threat for severe weather will continue to be assessed during the upcoming week. .SPOTTER INFORMATION STATEMENT... Spotter reports are encouraged if and when severe weather develops.
The Des Moines radar (KDMX), 133 km away, was scanning. The volume nearest the first event began at 10:23 UTC.
1 thunderstorm wind, 1 funnel cloud. Local standard time, as filed.
Emergency manager relayed a report of a 50 foot pine tree knocked over. Event was described as a burst of wind with other objects blown across the yard. Time estimated via radar.
Two funnel clouds spotted with storms northwest of Lake City, Iowa.
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: 898645, 898644.