An isolated thunderstorm developed across northeast South Dakota during the overnight, progressing southeast along the mid-level thermal gradient into northwest Iowa by late morning. Increased shear due to the deviant motion allowed a greater longevity to the storm, which made use of modest elevated instability to produce large hail and damaging wind.
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 FSD wrote it up.
An isolated thunderstorm developed across northeast South Dakota during the overnight, progressing southeast along the mid-level thermal gradient into northwest Iowa by late morning. Increased shear due to the deviant motion allowed a greater longevity to the storm, which made use of modest elevated instability to produce large hail and damaging wind.
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 Sioux Falls, SD wrote its last area forecast discussion before the first event at Jul 10, 6:06 AM CST, 3 hours 34 minutes earlier.
Area Forecast Discussion National Weather Service Sioux Falls SD 706 AM CDT Tue Jul 10 2018 .SHORT TERM...(Today and Tonight) Issued at 326 AM CDT Tue Jul 10 2018 A quiet and warm morning across the area. A jet max was moving across the Canadian border with a right entrance region moving through northern SD. A band of showers and thunderstorms were developing along and just ahead of about the 850mb moisture discontinuity as the upper level support moved across. If the thunderstorms continue to develop southward along this boundary parts of southwest MN could see an isolated or scattered thunderstorm from about 10z through 15z. However getting farther south is also getting away from some of the better upper support so only small chances will be in during this time. Instability and shear are both marginal and with the freezing level around 13500 feet severe thunderstorms look to be isolated at best. More than likely lightning and brief heavy rain would be the main threats. As this threat exits high pressure at the surface will be shifting east through the day, which will allow southerly flow to increase. This will bring warmer and more humid air back into the area. Afternoon heat indices will not quite get to advisory levels, but most locations can expect mid to upper 90s. The strong southerly flow will keep temperatures warm tonight and lows should only drop into the 70 to 75 degree range. This strong flow is in response to a wave moving into ND and a weak cold front expected to move into central SD by Wednesday morning. Any thunderstorm chances tonight should be isolated to scattered and north of the area. .LONG TERM...(Wednesday through Monday) Issued at 326 AM CDT Tue Jul 10 2018 Wednesday will be a very warm day with dew points in the 70s and temperatures in the upper 80s to mid 90s. This will lead to afternoon heat indices of about 97 to 102 in most locations. A heat advisory will likely need to be issued unless confidence in lower dew points occurs. Wednesday night still poses the best chance for severe thunderstorms this week. Expect CAPE values of 2000 to 2500 J/kg with fairly weak shear, some of the strongest winds in the lowest 1-2 km. This should lead to an event not too different from a couple of days ago to the north of the area, but with the boundary a little closer areas north of Interstate 29 will have a better chance this time around. Low temperatures will again be in the 70s. The front that settles into the area on Wednesday night will likely try to lift north Thursday afternoon and night as a bit of a stronger wave moves through ND into MN. The models this time around are a little more bullish with instability but shear is still marginal. With freezing levels running about 13000 to 14000 feet, heavy rain may become a problem if storms can get going. Not buying into the higher instability forecast just yet, but that will be something to watch out for. Thursday night may end up being the evening with the most weather problems. Beyond this things become much more muddled as the thunderstorms that may or may not develop really determine boundary locations and instability. But overall the pattern remains favorable through the weekend into early next week. Another fairly strong wave should spread onto the Plains Saturday night. && .AVIATION...(For the 12Z TAFS through 12Z Wednesday morning) Issued at 705 AM CDT Tue Jul 10 2018 Large convective complex over northeast SD will drive an outflow boundary through KHON early in the period, with winds likely becoming gusty for a brief time before synoptic gradient becomes reestablished during the latter morning hours. Conditions should remain VFR through the remainder of the period, outside a small chance that 12z-14z could see a brief trip into MVFR visibility for KSUX. Stronger gradient overnight aloft will bring low-level wind shear conditions to KHON after 06z. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && SHORT TERM...08 LONG TERM...08 AVIATION...Chapman
Hazardous Weather Outlook National Weather Service Sioux Falls SD 349 AM CDT Tue Jul 10 2018 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ040-056-062-067-070-071-110900- Lyon IA-Osceola-Dickinson-Sioux-O'Brien-Clay IA-Plymouth-Cherokee- Buena Vista-Woodbury-Ida-Lincoln MN-Lyon MN-Murray-Cottonwood- Nobles-Jackson-Pipestone-Rock-Dixon-Dakota-Brookings-Moody- Minnehaha-Lincoln SD-Clay SD-Union- 349 AM CDT Tue Jul 10 2018 This Hazardous Weather Outlook is for portions of northwest Iowa, west central Iowa, southwest Minnesota, northeast Nebraska, east central South Dakota, and southeast South Dakota. .DAY ONE...Today and Tonight Flooding continues on several rivers. For specific river details, visit https://water.weather.gov. Afternoon heat index values will climb into the mid 90s. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Heat index values will climb into the mid 90s on Wednesday afternoon. Thunderstorms will be possible on Wednesday evening. A few of the storms may become severe. The better chances will be north of Interstate 90. Thunderstorms will again be possible Thursday night. Isolated severe storms will be possible along with a threat for heavy rainfall. The better chances should be along and south of Interstate 90. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed tonight. SDZ038-039-050-052>055-057>061-063>066-068-069-110900- Beadle-Kingsbury-Gregory-Jerauld-Sanborn-Miner-Lake-Brule-Aurora- Davison-Hanson-McCook-Charles Mix-Douglas-Hutchinson-Turner- Bon Homme-Yankton- 349 AM CDT Tue Jul 10 2018 This Hazardous Weather Outlook is for portions of central South Dakota, east central South Dakota, south central South Dakota, and southeast South Dakota. .DAY ONE...Today and Tonight Afternoon heat index values will climb into the mid and upper 90s. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Heat index values will climb to 95 to 100 on Wednesday afternoon. Thunderstorms will be possible on Wednesday evening. A few of the storms may become severe. The better chances will be north of Interstate 90. Thunderstorms will again be possible Thursday night. Isolated severe storms will be possible along with a threat for heavy rainfall. The better chances should be along and south of Interstate 90. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed tonight.
The Sioux Falls radar (KFSD), 131 km away, was scanning. The volume nearest the first event began at 15:39 UTC.
3 hail, 2 thunderstorm wind. Local standard time, as filed.
Wind removed tree limbs up to 6 inches in diameter. Report from social media.
Hail up to half dollar size along with strong winds broke windows in a home and stripped leaves from trees. Branches up to an estimated inch in diameter also broken from trees.
Trees down up to 2 feet in diameter.
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, July 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: 773141, 773137, 773138, 773142, 773143.