Runoff from snowmelt in late April worked down the Mississippi River and caused some northeast Iowa river flooding to occur over the first half of May.
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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.
Runoff from snowmelt in late April worked down the Mississippi River and caused some northeast Iowa river flooding to occur over the first half of May.
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 May 1, 5:31 AM CST, 1 hour 29 minutes earlier.
Area Forecast Discussion National Weather Service La Crosse WI 631 AM CDT Tue May 1 2018 .SHORT TERM...(Today and tonight) Issued at 350 AM CDT Tue May 1 2018 At 3 AM, showers and scattered storms were found across western Minnesota and western Iowa. This activity is in response to the lift associated with the right entrance region of a 90-knot 250 mb jet max. The 01.00z models are in good agreement that this jet will lift north northeast into western Ontario by sunrise. As this occurs, this precipitation will gradually dissipate. Meanwhile, 850 mb moisture transport will move into parts of northeast Iowa and southern Wisconsin from mid morning into early afternoon. This will result in some elevated showers and maybe an isolated storm. From late afternoon into the evening, a surface low will be moving through the region. Many of the models are generating surface based CAPES 2-3 K J/kg ahead of this surface wave. These CAPES are based upon surface dew points climbing into the lower and mid 60s. Based on the dew points downstream, a bit concerned that these dew points may be 5 to 10F too high and this would greatly limit the surface based CAPES and the ability for these storms to become surface based. With 0-3 km shear up to 40 knots, there may be the potential for some isolated wind damage. This is assuming that these storms are able to become surface based. Otherwise the severe weather threat would be isolated large hail from elevated storms. As this low moves off to the northeast during the overnight, our precipitation will gradually wane. .LONG TERM...(Wednesday through Monday) Issued at 350 AM CDT Tue May 1 2018 On Wednesday, the main question is how far will the cold front sag south tonight. Many of the CAMs suggest that this boundary will move through much of the area and as a result the next round of showers and storms ends up mainly south of the forecast area for the afternoon and evening. Even the ECMWF suggests this possibility. Due to this, there is concern that our current forecast is too far north with its rain chances for Wednesday and Wednesday night and it may end up being mainly south of Interstate 90. Any severe weather chances look to be south and southeast of our area. On Thursday and Thursday night, the third and final low pressure system moves through the region. The highest chances of showers and storms look to be across northeast Iowa, and southwest and central Wisconsin. With limited instability, not anticipated any severe storms. && .AVIATION...(For the 12Z TAFS through 12Z Wednesday morning) Issued at 631 AM CDT Tue May 1 2018 Diminishing batch of showers (and a few lightning strikes) will skirt RST through 14Z but likely decay before reaching LSE, though a few additional showers could develop around that site through 16Z or so. The majority of the afternoon should feature VFR conditions along with dry weather, before showers and thunderstorms develop quickly late afternoon and into the evening along an approaching cold front. Exact timing is still somewhat questionable, but a period of MVFR to maybe briefly IFR is likely during those storms, before showers dwindle after 06Z as lower MVFR stratus develops being the departing rainfall. && .HYDROLOGY... Issued at 350 AM CDT Tue May 1 2018 Flood warnings continue along stretches of the Mississippi River. While several rounds of rainfall are possible through this week, the amounts will not be high enough to produce additional widespread flooding concerns. At this time, the flooding looks to be minor. See water.weather.gov for the specifics. && .CLIMATE... Issued at 350 AM CDT Tue May 1 2018 There were numerous monthly records on the April cold and snow. For more details consult RERRST and RERLSE. We also have a summary slide of all of the daily and monthly records either tied or broken on our Facebook page. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && SHORT TERM...Boyne LONG TERM...Boyne AVIATION...Lawrence HYDROLOGY...Boyne CLIMATE...Boyne
Hazardous Weather Outlook National Weather Service La Crosse WI 410 AM CDT Tue May 1 2018 IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029- 032>034-041>044-053>055-061-021200- Mitchell-Howard-Winneshiek-Allamakee-Floyd-Chickasaw-Fayette- Clayton-Wabasha-Dodge-Olmsted-Winona-Mower-Fillmore-Houston- Taylor-Clark-Buffalo-Trempealeau-Jackson-La Crosse-Monroe-Juneau- Adams-Vernon-Crawford-Richland-Grant- 410 AM CDT Tue May 1 2018 This Hazardous Weather Outlook is for portions of southeast Minnesota, northeast Iowa, and southwest into central Wisconsin. .DAY ONE...Today and Tonight There will be a chance of thunderstorms through the day. A few of these storms may produce isolated damaging wind gusts and large hail late this afternoon and evening. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Thunderstorms are possible at times across much of the area from Wednesday through Thursday night and again Saturday night. At this time, there is a small risk of severe storms south of Interstate 90 on Wednesday afternoon and evening. Water levels will continue to rise along the Mississippi River through the weekend, with minor flooding expected in some areas. Please visit water.weather.gov for the latest river forecast information. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to relay any storm reports this afternoon and evening. .EMERGENCY MANAGEMENT COORDINATION... No webinar is scheduled. Boyne
The national radar mosaic for the moment the first event began.
2 flood. Local standard time, as filed.
Runoff from snowmelt that occurred in late April worked downstream through the Mississippi River and caused some flooding at McGregor. The river crested over two feet above the flood stage at 18.34 feet on the 6th.
Runoff from snowmelt that occurred in late April worked downstream through the Mississippi River and caused some flooding at Guttenberg. The river crested almost two feet above the flood stage at 16.93 feet on the 6th.
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, May 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: 756995, 756996.