An atmosphere with strong potential instability of 2500-3000 J/kg along with deep-layer shear of 40 to 50 knots led to the development of scattered nocturnal storms in the warm advection zone ahead of an eastward moving shortwave along the Nebraska and South Dakota border.
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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 FSD wrote it up.
An atmosphere with strong potential instability of 2500-3000 J/kg along with deep-layer shear of 40 to 50 knots led to the development of scattered nocturnal storms in the warm advection zone ahead of an eastward moving shortwave along the Nebraska and South Dakota border.
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 Aug 19, 9:41 PM CST, 3 hours 51 minutes earlier.
AREA FORECAST DISCUSSION National Weather Service Sioux Falls SD 1041 PM CDT Mon Aug 19 2019 .SHORT TERM...(This Evening through Tuesday) Issued at 350 PM CDT Mon Aug 19 2019 Area of stratus across central South Dakota highlighting an area of low level moisture working north ahead of a short wave moving east along the South Dakota/Nebraska border. With strong 850 hpa warm air advection ahead of this wave, expect thunderstorms to develop this evening once warm air is able to work around the elevated mixed layer around 700 mb. Atmosphere is unstable with steep mid level lapse rates leading to 2500-3000 J/kg of CAPE. With 0-6 km bulk shear near 50 knots along the I-90 corridor (with greater shear values to the north), expect some storms to be severe. With the freezing level embedded in the steep mid level lapse rates, expect hail to be a possibility, along with strong damaging winds with a wealth of dry air aloft. 12Z sounding out of TOP indicated nearly 1.70" of precipitable water, which is near the 90 percent moving average. Dew points have climbed to near 70 F south of I-90, indicative of moist airmass working into the region. Training of storms may lead to very heavy rainfall overnight. .LONG TERM...(Tuesday Night through Monday) Issued at 350 PM CDT Mon Aug 19 2019 More tranquil conditions are expected Tuesday into Wednesday as high pressure builds into the Northern Plains. Disturbance moving across Nebraska Tuesday night into Wednesday may lead to some light rainfall along the South Dakota/Nebraska border. Flow becomes more active late this week as dirty zonal flow ushers a series of disturbances in the Northern Plains. This will result in potential for unsettled weather for the weekend into the early part of next week. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1038 PM CDT Mon Aug 19 2019 Isolated to scattered thunderstorms are expected to develop generally east of the Interstate 29 corridor after 07Z, then track eastward across the area overnight. A few of these storms could produce large hail and strong wind gusts, especially over northwest IA. MVFR/IFR stratus will develop across much of the area behind the convection, then slowly lift during the day on Tuesday. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && SHORT TERM...BT LONG TERM...BT AVIATION...JM
Hazardous Weather Outlook National Weather Service Sioux Falls SD 809 PM CDT Mon Aug 19 2019 MNZ071-072-080-081-089-090-097-098-NEZ013-014-SDZ038>040-052>056- 058>062-064>067-069>071-210115- Lincoln-Lyon-Murray-Cottonwood-Nobles-Jackson-Pipestone-Rock-Dixon- Dakota-Beadle-Kingsbury-Brookings-Jerauld-Sanborn-Miner-Lake-Moody- Aurora-Davison-Hanson-McCook-Minnehaha-Douglas-Hutchinson-Turner- Yankton-Clay-Union- 809 PM CDT Mon Aug 19 2019 This Hazardous Weather Outlook is for southwest Minnesota, northeast Nebraska, central South Dakota, east central South Dakota, south central South Dakota and southeast South Dakota. .DAY ONE...Tonight. There is a chance of thunderstorms from late evening into the overnight hours with the better chances east of I-29. A couple storms may approach the strong to severe category with large hail to size of ping pong balls the primary risk and damaging wind a secondary risk. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Hazardous weather is not expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed. IAZ001>003-012>014-020>022-031-032-210115- Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee- Buena Vista-Woodbury-Ida- 809 PM CDT Mon Aug 19 2019 This Hazardous Weather Outlook is for northwest Iowa and west central Iowa. .DAY ONE...Tonight. There is a chance of thunderstorms this evening and overnight. A few storms may approach the strong to severe category with large hail to the size of ping pong balls the primary risk and damaging wind a secondary risk. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Hazardous weather is not expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed. SDZ050-057-063-068-210115- Gregory-Brule-Charles Mix-Bon Homme- 809 PM CDT Mon Aug 19 2019 This Hazardous Weather Outlook is for south central South Dakota and southeast South Dakota. .DAY ONE...Tonight. No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed.
The Omaha radar (KOAX), 139 km away, was scanning. The volume nearest the first event began at 07:34 UTC.
5 thunderstorm wind, 1 hail. Local standard time, as filed.
Numerous large branches removed by thunderstorm winds.
Considerable tree damage from thunderstorm winds was reported throughout Ida Grove.
Thunderstorm winds snapped a 25 inch diameter tree near the base.
Winds took down numerous tree branches, several in excess of 3 inches diameter.
A couple of trees were taken down by thunderstorm winds, along with flattening of corn.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2019Every state in 2019This day in weather historyWarnings in Iowa, August 2019
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: 851946, 851947, 851949, 851950, 851951, 851944.