A cluster of strong to severe thunderstorms brought some damaging winds and very heavy rain to much of eastern and northeastern Iowa, and northwest Illinois during the late evening of September 5 into the early morning of September 6.
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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 DVN wrote it up.
A cluster of strong to severe thunderstorms brought some damaging winds and very heavy rain to much of eastern and northeastern Iowa, and northwest Illinois during the late evening of September 5 into the early morning of September 6.
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 Quad Cities, IA wrote its last area forecast discussion before the first event at Sep 5, 11:04 PM CST, 54 minutes earlier.
Area Forecast Discussion National Weather Service Quad Cities IA IL 1204 AM CDT Sun Sep 6 2020 ...06z AVIATION UPDATE... .SYNOPSIS... Issued at 204 PM CDT Sat Sep 5 2020 High pressure in control of the weather this afternoon with a few clouds streaming into the area from northern Iowa. High temperatures are generally in the lower to mid 80s. Dewpoints ranged from the mid 40s along the Highway 20 corridor to the upper 50s in far southeast Iowa and far northeast Missouri. && .SHORT TERM...(This Evening through Sunday) ISSUED AT 204 PM CDT Sat Sep 5 2020 The primary focus of the forecast has been the chances of showers and thunderstorms after 06 UTC Sunday. There are slight timing differences between all the models during this period. Quiet weather is expected through midnight as high pressure shifts eastward out of Illinois and into Ohio. This will allow winds to slowly become more southeasterly and begin to draw air slowly northward. Low temperatures by Sunday morning will be in the 60s. A 500 mb shortwave trough currently moving into the Dakotas will move southeastward and into southern Minnesota and Wisconsin by 12 UTC on Sunday. This shortwave in conjunction with a strong 40 to 50 knot low level jet will produce scattered showers and thunderstorms or a mesoscale convective system late Saturday night into early Sunday morning. The best convergence on the nose of the low level jet is expected to be into northern Iowa and southern Minnesota by 06 UTC Sunday which then veers into southern Wisconsin and northern Illinois by 12 UTC on Sunday. Instability will slowly build into the area ahead of this. Modest CAPE of 10000 to 1500 J/KG is expected but 0 to 6 km shear is forecast to be an impressive 55 to 55 knots. So these storms will be very fast moving and potentially capable of producing severe weather. Forecast soundings on the GFS and NAM show a stout inversion above the surface which coincide with the lifting warm front and strengthening low level jet. This indicates that the primary threat will be hail with also a secondary threat for winds. Models and CAMS show a primary threat for showers and storms being in the 08 to 15 UTC time frame but the GFS has it moving in at 06 UTC and lingering to about 18 UTC while the ECWMF is slightly slower. The CAMs learn more toward an 08 to 15 UTC timeframe. For this reason Storm Prediction Center has most of the area in a marginal risk west of the Mississippi River with a slight risk across Benton, Buchanan, and Linn Counties. In addition to the severe threat, increasing moisture and soundings do suggest that heavy rainfall is possible. The heavy rain falling on hard ground due to the drought conditions across the area may produce water running off but the fast storm motion may prevent this from occurring but it will need to be monitored. Models and WPC surface analysis have a warm front lifting northward out of the CWA by 18 UTC on Monday with the area in the warm sector for most of the day. The current high temperature forecast is on the high end of guidance with temperatures in the upper 80s to near 90s. In the wake of the warm front, deep mixing is possible which will mix down some warmer temperatures aloft but also stronger winds. Expect southerly winds through the day of 15 to 25 MPH with some gusts up to 35 MPH or slightly higher. The hot weather and gusty winds along with minimum relative humidities will require monitoring in case there are any fire weather concerns espousal in areas south of Interstate 80 which may miss the morning rainfall. The focus then shifts to an approaching strong cold front that CAMs want to use to force a second line of showers and thunderstorms and move that southeastward with time along and ahead of the front. It appears that the better lift remains out of the area until after 00 UTC on Monday. Weak convergence ahead of the front will not increase until later in the day with the arrival of another piece of shortwave energy. CAPE is forecast to build to around 2000 J/KG with continued 0 to 6 km shear of 50 to 55 knots which mean if storms due form that severe weather will be possible. This would mainly be along and ahead of the cold front which would still be west of Cedar Rapids at this time. The Storm Prediction Center also a slight risk of severe thunderstorms east of a Cedar Rapids to Iowa City line Sunday afternoon and into the evening hours. All modes of severe weather would be possible with hail, damaging winds, and tornadoes possible given the increasing curvature of model hodographs in the late afternoon and evening. .LONG TERM...(Sunday Night through Saturday) ISSUED AT 204 PM CDT Sat Sep 5 2020 Sunday night: A strong cold front will sweep across the upper mid- west bringing with it a chance of thunderstorms, especially over the northern half of the forecast area. Monday through Thursday: Monday morning looks to be mostly dry with drier air building in right behind the cold front, but rain with a chance of thunderstorms are likely by Monday afternoon. A much cooler and wetter will develop next week as a upper level longwave ridge builds over the Gulf of Alaska and northwestern Canada, and an upper level trough digs into the central CONUS. The cold front that crossed the region Monday, will stall just to our southeast, extending from Oklahoma to the Great Lakes. Periods of moisture will advect north from the Gulf of Mexico, riding over and along the stationary front producing periods of rain. Temperatures will be in the mid 70s on Monday but quickly drop to well below normal (10+ degrees) after the front moves through. High temperatures next week will only be in the 50s over the northern half of the region to around 60 across the south. Low temperatures will be in the 40s over the north and 50s over the south. Friday: The chance of continued rain will depend on how fast the closed low forecast to be located over Iowa, moves off to the northeast. There is model uncertainty with the timing, track and strength of this low but the overall forecast still suggests an unsettled and wet pattern. Model ensembles continue to support a widespread soaking rain of at least 1 to 2 inches by the end of week with higher amounts of 3 to 4 inches possible in some locations. The long duration of the rain, along with current drought conditions, will lower the chance of flooding, but this threat will need to be monitored closely. && .AVIATION...(For the 06Z TAFS through 06Z Sunday Night) ISSUED AT 1202 AM CDT Sun Sep 6 2020 While conditions will be mainly VFR, active weather will be found at all terminals during this TAF period. Showers and thunderstorms bringing drops to MVFR and perhaps IFR conditions will move through KDBQ/KCID/KMLI through the early morning, and will be followed by a short period of LLWS before surface winds increase out of the south by midday. Winds will likely gust up to 35 kts at times before an approaching cold front helps winds subside and shift to the northwest by the evening hours. Additional showers and storms may accompany this front, and have included a PROB30 group with this TAF for KDBQ/KCID/KMLI. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && SYNOPSIS...Cousins SHORT TERM...Cousins LONG TERM...Kuhl AVIATION...Speck
Hazardous Weather Outlook National Weather Service Quad Cities IA IL 331 AM CDT Sat Sep 5 2020 IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007- 009-015>018-024>026-034-035-MOZ009-010-060845- Buchanan-Delaware-Dubuque-Benton-Linn-Jones-Jackson-Iowa-Johnson- Cedar-Clinton-Muscatine-Scott-Keokuk-Washington-Louisa-Jefferson- Henry IA-Des Moines-Van Buren-Lee-Jo Daviess-Stephenson-Carroll- Whiteside-Rock Island-Henry IL-Bureau-Putnam-Mercer-Henderson- Warren-Hancock-McDonough-Scotland-Clark- 331 AM CDT Sat Sep 5 2020 This Hazardous Weather Outlook is for portions of north central Illinois...northwest Illinois...west central Illinois...east central Iowa...northeast Iowa...southeast Iowa and northeast Missouri. .DAY ONE...TODAY AND TONIGHT Thunderstorms will be possible across the area late tonight, with some having the potential to become severe. The Storm Prediction Center has a slight risk of severe thunderstorms north of a line from Manchester Iowa to Williamsburg Iowa, with a marginal risk for the rest of eastern Iowa into northwest Illinois. The primary threats with storms, will be damaging wind gusts and large hail. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Southwest winds could gust to 40 mph at times Sunday afternoon. Thunderstorms could redevelop over portions of the area late Sunday afternoon and evening ahead of a cold front. There is some uncertainty regarding how widespread these storms will be, but any storms that are able to form will be capable of producing large hail and damaging winds. Isolated thunderstorms will be possible at times next week. The threat for severe weather appears low. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed late tonight and early Sunday morning. McClure/Speck
The Quad Cities radar (KDVN), 156 km away, was scanning. The volume nearest the first event began at 05:58 UTC.
6 thunderstorm wind, 1 hail. Local standard time, as filed.
Power lines were blown down in Jesup. This report was relayed through broadcast media.
A measured wind gust from a storm spotter.
A strong wind gust was reported by broadcast media.
A strong wind gust was reported by broadcast media.
Several healthy 4 inch diameter tree branches were blown down.
Reported at the Davenport Airport.
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, September 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: 916139, 916138, 916141, 916142, 916143, 916140, 916144.