A cold front moved across eastern Iowa on the evening of August 1 with scattered showers and thunderstorms developing north of Interstate 80. Storms along the Highway 20 corridor became severe and produced damaging winds and torrential rains as they moved through Buchanan and Dubuque Counties.
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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 cold front moved across eastern Iowa on the evening of August 1 with scattered showers and thunderstorms developing north of Interstate 80. Storms along the Highway 20 corridor became severe and produced damaging winds and torrential rains as they moved through Buchanan and Dubuque Counties.
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 Aug 1, 5:01 PM CST, 2 hours 39 minutes earlier.
Area Forecast Discussion National Weather Service Quad Cities IA IL 601 PM CDT Wed Aug 1 2018 ...AVIATION UPDATE... .SYNOPSIS... Issued at 311 PM CDT Wed Aug 1 2018 18Z surface data has a weak low near KMSP. A cold front ran southwest from the low into northwest Iowa and then across Nebraska. Dew points ahead of the front were in the 60s with 50s across the northern Plains and northern Minnesota. && .SHORT TERM...(This Evening through Thursday) ISSUED AT 311 PM CDT Wed Aug 1 2018 Although there is a chance of rain this afternoon and tonight, many areas will probably not see any rain. A lack of forcing is causing any diurnal convection that develops to dissipate within a short time frame this afternoon. Thus through sunset isolated showers/sprinkles and possibly a thunderstorm will be seen. This evening the cold front will approach the area. The better forcing is still along the IA/MN border and into Wisconsin. Further south across eastern Iowa the forcing is expected to remain weak. Thus isolated to potentially scattered showers and some thunderstorms should be seen along/ahead of the front across the northwest half of the area. Late tonight and Thursday morning the cold front moves through the area. The loss of daytime heating and overall weak forcing suggests that areal coverage of showers and storms will decrease overnight. Areas generally north of I-80 have a slightly better chance of seeing some spotty rainfall late tonight. Thursday afternoon the question becomes whether or not any additional diurnal convection will develop. Based on the cloud cover and temperatures behind the front in the northern Plains today, it appears that the area will remain dry Thursday afternoon. .LONG TERM...(Thursday Night through Wednesday) ISSUED AT 311 PM CDT Wed Aug 1 2018 A change to a more zonal upper level flow will provide a return to warmer, more humid weather for the weekend into early next week. Unfortunately, for those looking for relief from the building drought stricken areas, there looks to be few opportunities for widespread rainfall. Thursday night into Friday: High pressure over southern WI and northern IL will provide clear and relatively cool conditions with overnight lows in the upper 50s to lower 60s. As the high continues eastward, the surface boundary stalled just south of the forecast area will retreat northward, possibly triggering some isolated showers or thunderstorms around or shortly after sunrise, especially along the IA highway 34 corridor. Both the GFS and ECMWF indicate this potential, which will be watched closely, but for now will keep pops just below 15 percent. Warm advection from the surface through 850 mb then commences Friday, likely sending highs into the lower 90s in the far southwest, while the northeast may only reach the lower 80s, depending on the timing of the passage of the 850 mb ridge axis. The heat then builds Saturday through Monday under a developing westerly flow aloft and warm advection low level southwest flow. Guidance temperatures continue to edge slightly upward from run to run, with upper 80s to lower 90s likely Saturday and Sunday. Dewpoints returning at least into the mid and upper 60s would drive max heat index readings into the mid 90s. The primary MCS track over the weekend will likely be well north of forecast area until a stronger shortwave, progged for roughly Sunday night into Monday drives an active frontal boundary southward toward the region. Thunderstorm chances look greatest across the north from Sunday night into Monday as the boundary begins edging southeast into the region. Model timing differences lend low confidence in details this period, impacting precipiation chances and forecast highs. Temperatures could again be into the lower 90s depending on the timing of the cold frontal passage Monday. Low level moisture convergence may drive dewpoints as high as the 70s for heat index readings well into the 90s. The early week shortwave is shown digging into a longwave trough to our east through midweek. The resulting upper level northwest flow, combined with high pressure at the surface should lead to a return of at least slightly cooler temperatures and dry weather late Tuesday into Wednesday. && .AVIATION...(For the 00Z TAFS through 00Z Thursday Evening) ISSUED AT 549 PM CDT Wed Aug 1 2018 Scattered showers and thunderstorms are possible tonight, mainly at KDBQ/KCID between 04-07Z/Thursday. Gusty winds and heavy downpours would be the primary impacts, which could result in brief MVFR/IFR. Late tonight into Thursday morning, there is a chance for MVFR stratus clouds developing, and advecting in from Minnesota. Confidence at this lead time is low on whether or not the clouds make it this far south, kept coverage at SCT for now. Uttech && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && SYNOPSIS...08 SHORT TERM...08 LONG TERM...Sheets AVIATION...Uttech
Hazardous Weather Outlook National Weather Service Quad Cities IA IL 430 AM CDT Wed Aug 1 2018 IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007- 009-015>018-024>026-034-035-MOZ009-010-021000- 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- 430 AM CDT Wed Aug 1 2018 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 There is a chance of thunderstorms, mainly this evening along and northwest of a line from Freeport, Illinois to Iowa City, Iowa. The main threats will be lightning and wind gusts to 40 MPH. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY There will be occasional chances for thunderstorms from Saturday night through Tuesday. It is too early to determine the severe weather potential during this period. Hot and more humid conditions are likely Friday through Sunday, with afternoon heat indices peaking in the middle 90s. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated today and tonight. 05/12
Special Weather Statement National Weather Service Quad Cities IA/IL 818 PM CDT WED AUG 1 2018 IAC019-020145- Buchanan- 818 PM CDT WED AUG 1 2018 ...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NORTHWESTERN BUCHANAN COUNTY UNTIL 845 PM CDT... At 818 PM CDT, radar indicated strong thunderstorms were located along a line extending from 7 miles south of Sumner to 7 miles north of Elk Run Heights. Movement was east at 40 mph. Winds in excess of 40 mph and half inch hail are possible with these storms. Locations impacted include... Fairbank, Hazleton, Stanley, Otterville, Fontana County Park, Fontana Park and Littleton. Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. LAT...LON 4264 9178 4250 9185 4250 9208 4264 9208 TIME...MOT...LOC 0118Z 274DEG 33KT 4274 9212 4256 9220 Uttech
The La Crosse radar (KARX), 146 km away, was scanning. The volume nearest the first event began at 01:41 UTC.
4 thunderstorm wind. Local standard time, as filed.
A trained spotter reported that an empty corn dryer was blown over and a pine tree was broken off about half way up. No other visible damage was noted on the property.
A COOP observer reported three 1 to 2 inch tree limbs were broken off.
A trained spotter reported down power lines.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2018Every state in 2018This day in weather historyWarnings in Iowa, August 2018
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: 781532, 781533, 781534, 782418.