Tornadoes made an October appearance along with other strong storms and heavy rainfall as a number of conditions came together. A frontal boundary stalled out across Iowa, situated from southwest to northeast, roughly cutting the state in half.
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.
Tornadoes made an October appearance along with other strong storms and heavy rainfall as a number of conditions came together. A frontal boundary stalled out across Iowa, situated from southwest to northeast, roughly cutting the state in half. Dew points were on the high side given the time of the year, in the upper 60s to low 70s, yielding low lifted condensation levels. In addition, low level turning resulted in 0-1km SRH values of 100-200+ m2/s2 within an environment of 1000+ J/kg SBCAPE. With all of that in play, a pair of tornadoes were confirmed during the evening hours, before giving way to predominantly sub-severe storms and heavy rainfall. Heavy rainfall conditions were bolstered by strong 850mb/moisture flow throughout the event with precipitable water values approaching 1.5 to 1.75 inches.
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 Oct 8, 4:53 AM CST, 1 hour earlier.
Area Forecast Discussion National Weather Service Des Moines IA 553 AM CDT Mon Oct 8 2018 .SHORT TERM.../Today through Tonight/ Issued at 353 AM CDT Mon Oct 8 2018 Trying to pin down POP trends and QPF is the primary forecast challenge today and tonight. Currently a cluster of intense thunderstorms is moving across our southeastern and eastern counties, while further west light rain blankets most of the rest of the forecast area. As a surface low pressure center gradually develops over the southern High Plains today and tonight, an inverted surface trough/cold front will steadily sharpen extending from eastern Kansas up across western Iowa. This will focus most of the rainfall later today and tonight into our western/northwestern half or so, with the rain in the east/southeast diminishing after late morning. Have continued to trend POPs this way, but maintained at least chance POPs in the east/southeast due to the ease with which precipitation can be generated in this very moist and generally unstable regime. We could also end up with quite a temperature gradient today as our northwestern counties up by Estherville will remain on the cool side of the developing front in clouds and rain, while our southeast down by Ottumwa may see a respite from the rain and significant warm air/moisture advection pushing temperatures up toward 80 degrees. Given the degree of warming and associated increase in instability, if thunderstorms do redevelop east of the front this afternoon/evening there may be a low risk of severe weather in the form of strong wind gusts, however this threat is conditional and marginal. Of greater concern is the continued and increasing potential for areal and river flooding, which is covered by the watch going into effect for nearly the entire forecast area. .LONG TERM.../Tuesday through Sunday/ Issued at 353 AM CDT Mon Oct 8 2018 From Tuesday through Wednesday the large western U.S. 500 mb trough that has been parked over the Rockies for the last several days will finally eject eastward across the Midwest. This will mercifully bring an end to the persistently wet weather and threat of heavy rain/flooding by Wednesday. However, before that occurs Tuesday and Tuesday night will continue to be exceptionally wet. The cold front/surface trough discussed in the short term section above will gradually shift eastward across our forecast area on Tuesday into Tuesday night, resulting in a shift and expansion of the flooding threat eventually affecting the entire area. As the surface low over the High Plains ejects northeastward along the frontal boundary in advance of the mid-level trough, it will provide increased forcing for vertical ascent coincident with peak heating on Tuesday afternoon/evening. Along and east of the front where instability is maximized, this will lead to a threat of severe weather, primarily strong winds, in addition to the flooding threat. This will make for an active and hazardous weather period on Tuesday into Tuesday night, with multiple threats possible. Have maintained high POPs and robust QPF through this period but primary message is the widespread flooding threat and slight risk of severe weather. The cold front will sweep across Iowa from west to east late Tuesday night and Wednesday morning, finally scouring out the rain and warm/humid airmass and bringing a notable change in sensible weather as autumn truly takes hold for the remainder of the long term forecast period. Temperatures will be significantly cooler from late Wednesday onward, with daily highs in the 40s and 50s and overnight lows in the 30s through the weekend. Frost and freezing temperatures will be likely on several of these mornings, especially across northern Iowa. Rain chances will also return to the forecast at times, mainly on Friday and perhaps Saturday, but contrary to the early week inundation any rain that does fall late in the week will be light and of little to no consequence. && .AVIATION.../For the 12Z TAFS through 12Z Tuesday morning/ Issued at 550 AM CDT Mon Oct 8 2018 Northwestern IA, including FOD/MCW, will remain socked in with IFR or lower MVFR ceilings through the TAF period. Further southeast OTM will break out with VFR conditions by 18Z and thereafter for the remainder of the TAF period. In between, DSM/ALO will be on the proverbial edge with IFR ceilings this morning likely rising to MVFR by around midday. Meanwhile widespread showers and isolated thunderstorms will move across the area at times, mainly this morning and again tonight. Have handled with prevailing -SHRA or VCSH but updates/amendments may be necessary as areas of heavier rain move through the area, reducing visibility to below 4SM at times. && .HYDROLOGY... Issued at 353 AM CDT Mon Oct 8 2018 Intense thunderstorms are moving across southeastern/eastern Iowa early this morning and additional rainfall is expected in this area today, before the heaviest rain axis shifts more to northwestern Iowa by tonight, then back eastward across the forecast area on Tuesday and Tuesday night. Widespread heavy rainfall of 2 to 4 inches is expected across most of the area over the next 48 hours or so, excepting the far southeast. Given that most areas are already saturated and seeing areal flooding, ponding, and/or river/stream rises, the additional rainfall will lead to increasingly widespread areal/river flooding issues. In light of this, and especially with Poweshiek/Mahaska/Marion having taken heavy rainfall a day or two ago and getting another round at the current time, have expanded the flood watch into those areas as well as our south central and southwestern counties. There is also a flash flooding threat over the next couple days, but it appears more localized and dependent on the location of heavier thunderstorm cores where rainfall rates will be maximized. For most of the area the high total rainfall amounts will generally be long-duration and more of a threat for gradual inundation than flash flooding. && .DMX WATCHES/WARNINGS/ADVISORIES... Flood Watch through Wednesday morning for IAZ004>007-015>017- 023>028-033>039-044>050-057>062-070>075-081>084-092>094. && SHORT TERM...Lee LONG TERM...Lee AVIATION...Lee HYDROLOGY...Lee
Hazardous Weather Outlook National Weather Service Des Moines IA 421 AM CDT Mon Oct 8 2018 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>084-092>094-090930- 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-Taylor-Ringgold-Decatur- 421 AM CDT Mon Oct 8 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Areas of heavy rainfall are possible today and tonight. Reference the Flood Watch for additional details. In additional, isolated severe storms are possible this afternoon and evening. Damaging wind gusts are the primary threat. A Flood Watch is in effect for the area in addition to other localized River Flood Watches. Please refer to the National Weather Service website at weather.gov/desmoines for further details. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday Heavy rainfall will remain possible through Tuesday night. A slight risk for severe weather is forecast for Tuesday afternoon and evening. Damaging wind gusts are the primary threat. A Flood Watch remains in effect for the area through Tuesday night in addition to other localized River Flood Watches. Please refer to the National Weather Service website at weather.gov/desmoines for further details. .SPOTTER INFORMATION STATEMENT... Spotters may be needed for flooding and heavy rain reports through Tuesday night. IAZ085-086-095>097-090930- Monroe-Wapello-Wayne-Appanoose-Davis- 421 AM CDT Mon Oct 8 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Showers and thunderstorms are possible today and tonight. Locally heavy rainfall and and isolated severe storm are possible. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday Periodic showers and a few thunderstorms are forecast through early Wednesday. The primary threat is locally heavy rainfall which may lead to overland flooding, ponding water and even localized flash flooding. There is a Slight Risk of severe storms Tuesday afternoon and evening with the primary threat being damaging wind gusts. .SPOTTER INFORMATION STATEMENT... Spotters may be needed for flooding and heavy rain reports and possible severe weather late Tuesday.
The Des Moines radar (KDMX), 123 km away, was scanning. The volume nearest the first event began at 11:51 UTC.
10 heavy rain, 7 flood, 2 tornado, 2 thunderstorm wind. Local standard time, as filed.
Lamoni Municipal Airport ASOS recorded heavy rainfall of 2.65 inches over the last 24 hours.
Chariton Municipal Airport recorded heavy rainfall of 2.72 inches over the last 24 hours.
Trained spotter reported heavy rainfall of 2 inches from 6 am to 1030 pm local time.
Coop observer recorded heavy rainfall of 3.40 inches over the last 24 hours.
Coop observer recorded heavy rainfall of 2.88 inches over the last 24 hours.
Coop observer recorded heavy rainfall of 4.25 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 2.89 inches over the last 24 hours.
Lake Red Rock mesonet station recorded heavy rainfall of 3.06 inches over the last 24 hours.
Mesonet station southeast of Knoxville recorded heavy rainfall of 3.01 inches over the last 24 hours.
Mesonet station just north-northwest of Pella recorded heavy rainfall of 2.76 inches over the last 24 hours.
Iowa DOT reported Highway 92 closed due to brief flooding near Muchakinock Creek.
QLCS tornado developed along the leading edge of the convection in northeast rural Guthrie County. The tornado remained in cropland for its entire path producing plenty of crop damage along with topping trees in a few different groves. The path was initially narrow but broadened as it continued northeast. Only toward the end of the track did it narrow once more. Damage path was also visible on high resolution satellite imagery.
Iowa DOT passed along a report of a tree blocking one lane along Highway 69 south of Osceola. The tree was too big to move by hand. This is a delayed report.
The tornado developed south of McComb Street between 330th Avenue and 305th Avenue. The tornado moved northeast across cropland and timberland producing EF1 damage at a old farmstead at the west end of Norman Street. Additional crop damage was noted near the intersection of Pacific Street and 330th Avenue. North of Pacific Street along 330th Avenue, extensive EF1 damage was noted to trees and a mobile home which had the midsection of the structure crushed by a falling tree branch. Additional tree and outbuilding damage was noted to a farmstead just to the north. The remainder of the path was in rural areas with little additional damage.
Six to 10 inches branches down from a tree in town. An off-duty NWS employee was traveling through town the day after the storm and say the branches down.
Emergency manager reported two roads closed across the county due to culvert failure and approximately 10 culverts damaged from flooding.
Iowa DOT reported US 65 closed due to flooding between County Road H50 and US 34.
Iowa DOT reported Highway 5 closed in both directions due to water over the road from English Creek, southeast of Knoxville.
Emergency manager reported water over a few gravel roads near Grinnell north of Interstate 80 and other county roads closed near Searsboro due to flooding.
Emergency manager reported a couple of roads with water over then near Sully.
Emergency manager reported multiple gravel roads remain closed due to water over them or washed out throughout the county.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2018Every state in 2018This day in weather historyThe tornado archive for Iowa, 2018Warnings in Iowa, October 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: 787233, 787234, 787232, 787235, 787236, 787237, 787238, 787239, 787240, 787241, 787230, 784987, 787231, 784991, 789916, 789912, 787242, 787243, 789935, 789937, 789940.