A relatively stationary frontal boundary remained over Iowa on the 9th, a day after the same boundary produced a couple of tornadoes, strong storms, and heavy rainfall. In similar fashion, the environment was conducive for rotating storms.
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.
A relatively stationary frontal boundary remained over Iowa on the 9th, a day after the same boundary produced a couple of tornadoes, strong storms, and heavy rainfall. In similar fashion, the environment was conducive for rotating storms. Running down the list of conducive features, LCLs were under 1000m, SBCAPE values were in the 1000-2000 J/kg range, effective bulk shear was in excess of 40kts, and effective storm relative helicity was in excess of 200 m2/s2. All in all, it was not going to take much for storms to rotate and have the potential to product funnel clouds and at least brief tornadoes. Scattered showers and storms were persistent through the afternoon and early evening, with a number producing brief tornadoes.
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 9, 12:17 PM CST, 2 hours 7 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 117 PM CDT Tue Oct 9 2018 ...Updated for 18z Aviation Discussion... .SHORT TERM.../Today through Tonight/ Issued at 430 AM CDT Tue Oct 9 2018 Deep southerly flow will persist into the state through tonight as upper system finally begins to eject from the intermountain southwest. The deep flow of moisture and instability will continue during this period with the surface front stretching southwest to northeast through the center of the state although it will meander some. Large area of showers and embedded thunderstorms are expected to move north into the western half of the state this morning with a round of moderate to heavy rainfall. Meanwhile, the east should see more of a break by early afternoon. This will allow for modest destabilization into the afternoon along with a veering wind profile as the surface low begins to deepen. This should lead to another late afternoon/early evening round of strong to severe storms across the southeast half of the forecast area. Given the low LCLs, veering profile and some modest CAPE in the low levels, a few tornadoes seem possible once again in the slight risk area of storms. This threat will persist into the evening and maybe even longer than Monday evening given the increasing synoptic forcing and surface low moving toward the state. The convection will persist into the overnight with the surface low approaching and entering Iowa. The rainfall concerns will persist and are highlighted below in the Hydrology section. Temperatures today will move very little in the northwest behind the boundary with low status and periods of rain. Farther southeast in the warm sector, temperatures are likely to climb to near 80 by mid afternoon prior to convective development. .LONG TERM.../Wednesday through Monday/ Issued at 430 AM CDT Tue Oct 9 2018 Surface low will be near Des Moines at the beginning of this period along with ongoing pcpn over much of northern and eastern Iowa. However, subsidence will be increasing across the southwest during the morning along with strengthening cold advection. This will bring a halt to the showers across the south and west during the morning and elsewhere by early to mid afternoon. Highs in the east will likely be in the morning on Wednesday with strong cold advection developing during the day behind the cold front. Otherwise, breezy conditions are expected through the day into Wednesday evening as the cold advection continues. Much needed quiet weather is expected on Thursday as large Canadian surface ridge approaches the state. This will have some implications for frost/freeze on Thursday night with light winds and initially clear skies across the area. Frost is expected across the north and possibly central Iowa during the night as temperatures drop into the low to mid 30s. The limiting factor for frost farther south with be an increase in clouds overnight which will likely hamper radiational cooling and the frost potential. Both GFS and Euro have a weak shortwave approaching from the northwest late Thursday night into Friday with increasing clouds and some decent isentropic lift. However, moisture will be limited and the threat of precipitation will remain low. However, another shortwave will drop quickly southeast into the central United State by the weekend. This will have some interaction with Hurricane Sergio from the eastern Pacific and while the bulk of moisture from Sergio will remain to the south, it will help deepen the system. This will produce additional rain into Iowa from late Saturday into Sunday with highest amounts in the south. Both models are hinting at deformation precipitation crossing the state on Sunday night which would be a very cold rain with even the possibility of a few snow flakes on the northwest side of the precipitation area. Drier but cool conditions are then expected into early next week as broad northwest flow develops across the central United States. && .AVIATION.../For the 18Z TAFS through 18Z Wednesday afternoon/ Issued at 114 PM CDT Tue Oct 9 2018 Messy TAF forecast continues. Expecting Thunder at all sites this afternoon through early tonight...timing dependent upon site. Vsbys will likely be 1 mile or less during heavy downpours. Given the speed of storms, periods of highly reduced vsbys would less than 1 hour. Precip to eventually move east of TAF sites by tomorrow afternoon. && .HYDROLOGY... Issued at 430 AM CDT Tue Oct 9 2018 Continued deep moist southerly flow into the state through tonight. PWATs will remain impressive and near the climatological max for this time of year. Western Iowa will be the focus into today for the heavier QPF but some translation slightly eastward is expected by afternoon closer to the instability axis where storms are forecast to fire. These storms will have higher precipitation rates and are expected to persist through the evening and into the overnight, albeit not as strong. Main concern here is that flash flooding may be more of a danger later today into tonight that has occurred with this system to this point given the heavy rainfall already received and the higher rates expected later today into this evening. Otherwise, widespread areal and river flooding continue to look likely through tonight into early Wednesday before the precipitation subsides. Thereafter, river flooding is expected to linger for quiet some time as the water gradually routes through the streams and rivers. The Flood Watch has been expanded to include the rest of the forecast after some moderate to heavy rains in those areas along with collaboration from surrounding sites. && .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>086-092>097. && SHORT TERM...Cogil LONG TERM...Cogil AVIATION...Kotenberg HYDROLOGY...Cogil
Hazardous Weather Outlook National Weather Service Des Moines IA 352 AM CDT Tue Oct 9 2018 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-101100- 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- 352 AM CDT Tue Oct 9 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Isolated thunderstorms are forecast this morning, becoming more scattered to widespread at times from this afternoon through tonight. From mid-afternoon into early tonight severe weather will be possible across about the southeast half of Iowa. Damaging winds, locally heavy rain and flash flooding, and a few tornadoes will all be possible. 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...Wednesday through Monday River flooding will continue across much of Iowa for the remainder of the week. Frost and freezing temperatures will also be possible on some mornings from Thursday onward, especially in northern Iowa. .SPOTTER INFORMATION STATEMENT... Spotters may be needed at times today and tonight for flooding and severe weather. Lee
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
942 AM CDT TUE OCT 9 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0800 AM HEAVY RAIN 2 W KNOXVILLE 41.32N 93.13W
10/09/2018 M4.25 INCH MARION IA CO-OP OBSERVER
CO-OP OBSERVER STATION KNXI4, KNOXVILLE.
0700 AM HEAVY RAIN 6 SE MELCHER-DALLAS 41.18N 93.15W
10/09/2018 M3.40 INCH MARION IA CO-OP OBSERVER
CO-OP OBSERVER STATION CMBI4, COLUMBIA.
0900 AM HEAVY RAIN 4 SW PELLA 41.37N 92.98W
10/09/2018 M3.06 INCH MARION IA MESONET
MESONET STATION RRMI4, LAKE RED ROCK.
0915 AM HEAVY RAIN 3 ESE KNOXVILLE 41.30N 93.05W
10/09/2018 M3.01 INCH MARION IA MESONET
MESONET STATION KECI4, 3 ESE KNOXVILLE.
0900 AM HEAVY RAIN 1 NW GRINNELL 41.75N 92.73W
10/09/2018 M2.89 INCH POWESHIEK IA COCORAHS
COCORAHS STATION IA-PW-4, GRINNELL 0.6 NW.
0700 AM HEAVY RAIN 1 WNW LAMONI 40.62N 93.95W
10/09/2018 M2.88 INCH DECATUR IA CO-OP OBSERVER
CO-OP OBSERVER STATION 3OI, LAMONI.
0926 AM HEAVY RAIN 1 NNW PELLA 41.43N 92.93W
10/09/2018 M2.76 INCH MARION IA MESONET
MESONET STATION AU190, 1 NNW PELLA.
0655 AM HEAVY RAIN 3 W CHARITON 41.02N 93.36W
10/09/2018 M2.72 INCH LUCAS IA AWOS
AWOS STATION CNC, CHARITON AIRPORT.
0653 AM HEAVY RAIN 2 ENE LAMONI 40.63N 93.90W
10/09/2018 M2.65 INCH DECATUR IA ASOS
ASOS STATION LWD, LAMONI MUNI AIRPORT.
&&PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1021 AM CDT TUE OCT 9 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0800 PM TSTM WND DMG 1 SSE OSCEOLA 41.02N 93.76W
10/08/2018 CLARKE IA DEPT OF HIGHWAYS
IDOT PASSED ON REPORT OF TREE BLOCKING ONE
LANE ALONG HIGHWAY 69 SOUTH OF OSCEOLA. TREE
WAS TOO BIG TO MOVE BY HAND. DELAYED REPORT.
&&
BSSThe Des Moines radar (KDMX), 135 km away, was scanning. The volume nearest the first event began at 20:27 UTC.
12 tornado, 1 funnel cloud. Local standard time, as filed.
The tornado developed near the Centerville Municipal Airport with one of the hangars sustaining EF0 damage. The tornado proceeded through cropland up to the southwest outskirts of Centerville before dissipating.
Brief tornado reported by a storm chaser south of Rathbun. This tornado stayed in rural crop and grazing land with little to no damage.
Tornado developed west of the hamlet of Ewart and moved due north. Tornado remained in rural agricultural land with little damage.
Numerous spotters reported a tornado north of Brooklyn. The tornado traveled north for a brief distance across cropland in Poweshiek County before entering Tama County. Only minor crop damage occurred in Poweshiek County.
Numerous spotter reported this tornado as it moved from Poweshiek into Tama County. This tornado remained in open cropland with little if any damage.
Tornado developed in rural western Ringgold county and moved almost due north across open cropland. Little damage was noted. Tornado was found using high resolution satellite imagery.
Emergency manager relayed public reports of two funnel clouds in the area.
This tornado developed between Creston and Cromwell in western Union county and traveled on a somewhat unusual northwest path. Tornado was mostly in open rural cropland for nearly two miles producing only crop damage. However, the tornado encountered farmsteads along Clover Avenue about one half mile south of 170th Street. A garage was destroyed on the west side of the road and was rated EF1 damage given generally poor construction. Additional EF1 damage was observed with the nearby house with a portion of the roof and truss structure removed. Tree damage was observed across the road at an adjacent house. Additional minor damage was found about one quarter mile farther up the road with the last damage noted north of 170th Street on the west side of the road where a few roof panels were blown off an old metal shed.
Tornado developed in far northern Black Hawk County and moved due north through open cropland. The tornado encountered a house along West Gresham Road just east of Leversee Road and produced EF0 damage to trees and shingles. The tornado then moved north into open cropland and was captured on video for the remainder of its path, crossing into Bremer County before dissipating.
Tornado moved into Bremer County from Black Hawk County. The tornado remained over open cropland before dissipating with little if any damage.
Tornado was determined by a tornadic debris signature on radar and subsequently found via high resolution satellite imagery. Any damage was to crops as the tornado remained across rural agricultural land east of Orient.
Tornado developed just south of the hamlet of Arbor Hill and produced minor tree damage along the Stuart Road. The tornado moved northeast and remained over cropland with little damage noted. Portions of the path were observed using high resolution satellite imagery.
Tornado developed just east of the Stuart Road in open cropland. The tornado moved on a slightly unusual northwest track eventually crossing the Stuart Road about one half mile south of 150th Street. The tornado produced EF1 damage to outbuildings and trees at a farmstead on the southwest intersection of 150th & Stuart Road. The tornado then moved back into cropland with only some minor tree and crop damage noted until it dissipated.
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: 785018, 785019, 785020, 785021, 785022, 785128, 787244, 785130, 785133, 785145, 785146, 785147, 785148.