Thunderstorms moved across portions of northeast Iowa on October 1st. These storms dropped between 2 and 4 inches of rain most of Clayton County.
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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 ARX wrote it up.
Thunderstorms moved across portions of northeast Iowa on October 1st. These storms dropped between 2 and 4 inches of rain most of Clayton County. With already saturated ground from rain in late September, the runoff caused river flooding to occur along the Turkey River at both Elkader and Garber. Flooding along Peck Creek sent water over a road west of Millville and creeks in North Buena Vista also went out of their banks.
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 La Crosse, WI wrote its last area forecast discussion before the first event at Oct 1, 10:30 AM CST, 2 hours earlier.
Area Forecast Discussion National Weather Service La Crosse WI 1130 AM CDT Mon Oct 1 2018 .SHORT TERM...(Today and tonight) Issued at 323 AM CDT Mon Oct 1 2018 Main forecast concerns are on the potential for locally heavy rainfall today. Showers and scattered thunderstorms will become widespread across the area by late morning. Showers and storms are expected to increase across northeast Iowa and southwest Wisconsin in the 13Z to 15Z timeframe as 850 mb moisture transport ramps up as a shortwave trough moves in from the west. The most concentrated area of showers and storms today will stretch from northeast Iowa into southwest and central Wisconsin, since this is where the bulk of the instability/CAPE resides. The warm sector will stay southeast of the area today as surface low pressure tracks from southcentral Iowa into northern Illinois. So the thunderstorms will be rooted above the boundary layer. Precipitable water values increase into the 1.4 to 1.7 inch range over northeast through southwest and central Wisconsin today and warm cloud depths increase to 3500-4000 meters. In this environment the thunderstorms will be efficient rain producers. Rainfall amounts of 1 to locally 3 inches are possible which will likely lead to river rises and possible flooding in poor drainage areas. MUCAPE will range from 500 to 900 J/kg over these areas with a slight increase to 1100 J/kg over portions of Clayton and Grant counties this afternoon. With the warm sector displaced to the southeast of the forecast area we are not expecting more than an isolated threat for a strong thunderstorm or two. However, the 00Z NAM suggests the warm sector gets into far southern Grant County but this is an outlier. HREF suggests surface based CAPE stays about a county south of Grant County. Cannot rule out isolated large hail closer to higher MUCAPE values over extreme northeast Iowa into far southwest Wisconsin. If the warm sector can edge north like the NAM suggests there could be a 1-2 hour window for severe storms mainly in the 21Z to 00Z timeframe. 0-3 KM Bulk Shear values increase to around 40 kts so this would favor a threat for damaging winds. There would also be an isolated tornado threat in the warm sector but that looks to stay just southeast of the forecast area. .LONG TERM...(Tuesday through Sunday) Issued at 323 AM CDT Mon Oct 1 2018 Main forecast concerns in the long term are on strong southerly winds on Wednesday and the potential for severe thunderstorms Wednesday afternoon and evening, if storms develop. A warm front lifts north across the area Tuesday night into Wednesday morning bringing chances for showers and thunderstorms to the area. Then as low pressure deepens and tracks from eastern South Dakota toward the Arrowhead of Minnesota, strong southerly winds are expected across the region. Plan on wind speeds of 15 to 25 mph with gusts of 30 to 40 mph, possibly gusting as high as 45 mph in open unsheltered areas. A wind advisory may be needed for portions of northeast Iowa and southeast Minnesota. Wednesday will also be on the warm side with high temperatures expected to climb into the mid 70s and possibly into the lower 80s along and south of Interstate 90. The low then tracks northeast into central Ontario Wednesday afternoon into Wednesday evening pulling a cold front across the area. 0-3 KM Bulk Shear Values are expected to climb to around 35 kts with 0-6 KM Bulk Shear values ranging from 30 kts over northeast Iowa to around 50 kts across north-central Wisconsin. Surface based CAPE values look to climb to around 2000 J/kg based on the NAM 12. However, the NAM appears to have dew point values that are too high, into the lower 70s. Upper 60s seems more realistic. Another negative will be an elevated mixed layer centered around 775 mb, creating a Cap. If the CIN can be overcome, severe thunderstorms would be possible with a threat for damaging winds if storm form into a line. Given the stronger shear along and north Interstate 90 and CAPE, there is the potential for Supercells if storms develop during the mid afternoon and early evening hours. Considering the curvature of the hodographs, right movers would be favored with all severe weather threats possible including damaging winds, large hail, and perhaps tornadoes. Storms should then organize into a line or line segments as they progress eastward. A lot of uncertainty regarding how much CAPE can build and if the CIN can be overcome. Will have to keep a very close eye on model trends as we draw closer to Wednesday. High pressure builds in Wednesday night into Thursday with cool and quiet weather expected. Southwest flow aloft then sets up across the region Thursday night into weekend with several rounds of showers and thunderstorms expected. The first wave of rain looks to move in Thursday night into Friday as low pressure move out of the central plain into the Upper Midwest. After a brief break Saturday night into early Sunday then additional rounds of rain are possible from late in the weekend into early next week with the potential for flooding concerns. A lot of uncertainty but this timeframe will need to be watched very closely. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1130 AM CDT Mon Oct 1 2018 Upper level shortwave trough going to be bring shra with a few storms for the afternoon into early evening. Low clouds already in place and should stay that way well into Wed. Cigs: mostly ifr expected through Tue morning, with ifr/mvfr likely then into Wed. Models holding onto low saturation into Wed, with better shot for some clearing Wed afternoon - more likely overnight Wed as high pressure briefly builds in. WX/vsby: mostly mvfr restrictions with shra, although some dip into ifr possible with any moderate/heavy shower. An isold storm possible this afternoon, and will continue to tempo that potential. Also with hold with the mvfr br tonight with moist boundary layer and relatively light winds. Winds: holding east through the period, with some decrease for the night time hours. && .HYDROLOGY...Today Issued at 323 AM CDT Mon Oct 1 2018 Locally heavy rainfall remains a concern today across portions of northeast Iowa into southwest and possibly central Wisconsin. Thunderstorms could produce 1 to locally 3 inches of rainfall. This will lead to rises on area rivers and the potential for some flooding depending on where the heaviest rain falls. Ponding of water can be expected in poor drainage areas. If you have interest along rivers or are in a poor drainage area prone to flooding, be sure to monitor river levels closely and be ready to move to higher ground if heavy rain develops. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && SHORT TERM...Wetenkamp LONG TERM....Wetenkamp AVIATION.....Rieck HYDROLOGY....Wetenkamp
Hazardous Weather Outlook National Weather Service La Crosse WI 418 AM CDT Mon Oct 1 2018 IAZ008-009-018-MNZ079-086>088-094>096-WIZ017-029-032>034-041>044- 021200- Mitchell-Howard-Floyd-Wabasha-Dodge-Olmsted-Winona-Mower-Fillmore- Houston-Taylor-Clark-Buffalo-Trempealeau-Jackson-La Crosse-Monroe- Juneau-Adams- 418 AM CDT Mon Oct 1 2018 This Hazardous Weather Outlook is for southeast Minnesota, portions of northeast Iowa, and western into central Wisconsin. .DAY ONE...Today and Tonight Isolated thunderstorms are expected today, mainly along and south of Interstate 90. The main threat from any storms will be lightning and brief heavy downpours. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday Isolated thunderstorms are possible Tuesday night into Wednesday morning. The main threat from these storms will be lightning. Strong south winds could gust to around 45 mph at times in open areas west of the Mississippi River late Wednesday morning into Wednesday afternoon. Thunderstorms are possible across much of the area Wednesday afternoon into early Wednesday evening and a few could be severe. If storms develop during this time, severe weather threats would include damaging winds and large hail. There is a slight chances of thunderstorms Friday afternoon. Severe weather is not expected at this time. .SPOTTER INFORMATION STATEMENT... No action needed at this time. .EMERGENCY MANAGEMENT COORDINATION... No webinar is scheduled. IAZ010-011-019-029-030-WIZ053>055-061-021200- Winneshiek-Allamakee-Chickasaw-Fayette-Clayton-Vernon-Crawford- Richland-Grant- 418 AM CDT Mon Oct 1 2018 This Hazardous Weather Outlook is for portions of northeast Iowa and southwest Wisconsin. .DAY ONE...Today and Tonight Scattered thunderstorms are expected across the area today. The main threat from storms will be locally heavy rainfall which may lead to localized flooding and rising river levels. A few storms could also produce hail and strong winds this afternoon. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday Isolated thunderstorms are possible Tuesday night into Wednesday morning. The main threat from these storms will be lightning. Strong south winds could gust to around 45 mph at times in open areas west of the Mississippi River late Wednesday morning into Wednesday afternoon. Thunderstorms are possible across much of the area Wednesday afternoon into early Wednesday evening and a few could be severe. If storms develop during this time, severe weather threats would include damaging winds and large hail. There is a slight chances of thunderstorms Friday afternoon. Severe weather is not expected at this time. .SPOTTER INFORMATION STATEMENT... Rainfall reports would be appreciated today. .EMERGENCY MANAGEMENT COORDINATION... No webinar is scheduled. Wetenkamp
The national radar mosaic for the moment the first event began.
3 flood. Local standard time, as filed.
Runoff from heavy rains pushed the Turkey River out of its banks in Garber. The river crested over six feet above the flood stage at 23.7 feet on October 1st.
Runoff from heavy rains produced some flooding across the southern portions of Clayton County. Water from Peck Creek went over Millville Road west of Millville and creeks went out of their banks in North Buena Vista.
Runoff from heavy rains pushed the Turkey River out of its banks in Elkader. The river crested less than a foot above the flood stage at 12.67 feet on October 1st.
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, 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 2026-10-01. Each event’s entry at NCEI: 788686, 789089, 788684.