Thunderstorms developed along a cold front in a deeply shear-parallel environment with 1000-2000 J/kg MLCAPE and quickly evolved into linear structures with spotty damaging wind gusts.
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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.
Thunderstorms developed along a cold front in a deeply shear-parallel environment with 1000-2000 J/kg MLCAPE and quickly evolved into linear structures with spotty damaging wind gusts.
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 Oct 3, 5:15 PM CST, 2 hours 10 minutes earlier.
AREA FORECAST DISCUSSION National Weather Service Sioux Falls SD 615 PM CDT Tue Oct 3 2023 .SHORT TERM...(This Evening through Wednesday) Issued at 252 PM CDT Tue Oct 3 2023 KEY MESSAGES: 1. Numerous thunderstorms expected this afternoon into the evening hours, with scattered severe storms possible. Damaging winds are the primary threat, but isolated large hail and tornadoes are possible. 2. Pattern transitions Wednesday and brings cooler than normal temperatures, with highs on Friday and Saturday in the 50s. 3. First chances for frost this season overnight Friday into Saturday, and again overnight into Sunday. .................................................................... Afternoon satellite imagery shows partly cloudy skies across the region, with agitated cu forming as positive theta-e advection taps into some of the elevated instability. Scattered showers and thunderstorms are shown on radar, with the aforementioned theta-e advection keeping chances for scattered showers and thunderstorms into the evening hours. Water vapor imagery displays our wave of interest currently ejecting onto the central plains, which will be racing towards the region throughout the afternoon hours. As the wave pushes towards the area, this will send an area of low pressure into southern Canada. The attached cold front will thus be shifting eastwards, currently draped from near northeast SD towards southwest/central South Dakota, with a dry line trying to set up across central South Dakota out ahead of the cold front. The dry line will act as the western extend of the stronger storms, with MUCAPE values of around 1000 J/kg expected to build into the region with the clearing skies overhead. The first round of showers and thunderstorms are currently traversing the NE/SD border, and will need to be monitored for storm mode and severe threat. Given the broad WAA and the 40 to 50 knots of shear (vast majority being speed shear), discrete storms may become supercellular and capable of producing large hail to the size of half dollars. If a supercell were to form near the dry line, 10-20 knots of low level shear and low LCL heights would also add a tornado threat. With strong 500 to 850 mb flow, showers/storms will be quickly moving along between 40 to 50 mph, so stay aware of your surroundings as storms could be approaching your location quickly. After this first push of thunderstorms, additional development is expected across central Nebraska as the main wave catches up, which will transition any discrete cells into linear mode and will be the main show today. With the 500 mb jet max of 50 to 60 knots helping to pull the wave along, storm motion may increase to get near 60 mph. Models have been showing MUCAPE of 1000-2000 J/kg will be brought into the area with these mid/late afternoon storms into the evening hours, and with bulk shear values of up to 55 knots running parallel to the surface cold front, upscale growth is expected to continue into the evening hours. Give the stronger winds aloft running parallel to the storm motion, strong damaging winds are the primary threat with these thunderstorms, though isolated large hail can't be ruled out. An isolated QLCS tornado may also occur, but this will depend on a section of the line orienting itself from northwest to southeast, which would then run perpendicular to the south-southwesterly oriented 0-3km shear. Severe weather threat diminishes by the late evening hours as the boundary layer stabilizes and instability wanes, but scattered showers and thunderstorms may continue into the early overnight period. By Wednesday morning, the cold front will have finished sweeping through, with early morning temperatures in the lower to mid 50s. As a weak high pressure develops at the surface just south of the region, we'll see periods of breezy north-northwesterly winds before the surface high slides eastwards which will bring calmer winds temporarily back to the region. While Wednesday will be much closer to normal temperatures than we have been lately, we will have shifted into temperatures below normal with afternoon highs in the mid to upper 60s whereas normal highs would be in the upper 60s. This will be a sharp contrast to the temperatures we have been experiencing, but will remind all that fall is indeed here. .LONG TERM...(Wednesday Night through Tuesday) Issued at 252 PM CDT Tue Oct 3 2023 Overnight into Thursday, the jet max reinforces the trough aloft, strengthening the winds up again as a new surface low pressure moves into the northern great plains from Saskatchewan/Manitoba, Canada. This will bring our next cold front into the region with afternoon highs a bit lower into the lower to mid 60s, and breezy northwest winds. The cooler air does lag behind the front a bit, but they will be brought in throughout the evening and overnight hours, with stronger winds also developing as a surface high pressure develops off to the west as ridging develops off to the west. Models have come into slightly better agreement that we could see a round of weak showers overnight into the morning hours Friday, though the two clusters with the highest ensemble members show the precipitation splitting the area. Lows overnight in the upper 30s to lower 40s, with wind chills in the upper 20s to lower 30s! Be sure to bundle up before heading out the door on Friday! An even chillier day is expected for Friday as the surface high pressure slides towards the area, with daytime highs in the upper 40s and lower 50s. Similar conditions are expected for Saturday, though ridging builds in the west by the late afternoon hours. Chances for frost return to the area Friday night into Saturday, though that will depend on how breezy we are and when the surface ridge axis slides overhead. Temperatures start to warm up again to become near normal by Sunday/Monday. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening) Issued at 612 PM CDT Tue Oct 3 2023 A line of thunderstorms will move through southeast SD and northeast NE through about 3z, then into northwest IA and southwest MN from about 2z through 5z. A few of these storms may become severe. Outside of any hazards associated with the thunderstorms, mainly VFR conditions are expected. Wind gusts from the west northwest of 20 to 30 mph will be possible on Wednesday. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && SHORT TERM...APT LONG TERM...APT AVIATION...08
Hazardous Weather Outlook National Weather Service Sioux Falls SD 508 AM CDT Tue Oct 3 2023 IAZ001-012-020-031-MNZ071-097-098-NEZ013-014-SDZ038>040-050-052>071- 041015- Lyon-Sioux-Plymouth-Woodbury-Lincoln-Pipestone-Rock-Dixon-Dakota- Beadle-Kingsbury-Brookings-Gregory-Jerauld-Sanborn-Miner-Lake-Moody- Brule-Aurora-Davison-Hanson-McCook-Minnehaha-Charles Mix-Douglas- Hutchinson-Turner-Bon Homme-Yankton-Clay-Union- 508 AM CDT Tue Oct 3 2023 This Hazardous Weather Outlook is for northwest Iowa, west central Iowa, southwest Minnesota, northeast Nebraska, central South Dakota, east central South Dakota, south central South Dakota and southeast South Dakota. .DAY ONE...Today and tonight. Spotty showers or an isolated thunderstorm are possible through midday. The chance for storms will increase by mid-late afternoon and continue into the early evening. Initial storms in the afternoon may be capable of large hail up to half dollar size and perhaps an isolated tornado. As storms evolve into a line in the late afternoon and evening, the primary threat will transition to damaging winds up to 70 mph. Brief heavy rainfall is also possible. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Much cooler air settles into the region late this week, bringing the potential for our first frost by Friday night and/or Saturday night. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. IAZ002-003-013-014-021-022-032-MNZ072-080-081-089-090-041015- Osceola-Dickinson-O'Brien-Clay-Cherokee-Buena Vista-Ida-Lyon-Murray- Cottonwood-Nobles-Jackson- 508 AM CDT Tue Oct 3 2023 This Hazardous Weather Outlook is for northwest Iowa, west central Iowa and southwest Minnesota. .DAY ONE...Today and tonight. Spotty showers or an isolated thunderstorm are possible into the early afternoon. The chance for thunderstorms will increase late afternoon into this evening. Initial storms in the afternoon may be capable of hail up to quarter size, but the greater threat will be damaging winds up to 70 mph as storms evolve into a line. Brief heavy rainfall is also possible. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Much cooler air settles into the region late this week, bringing the potential for our first frost by Friday night and/or Saturday night. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The Omaha radar (KOAX), 128 km away, was scanning. The volume nearest the first event began at 01:22 UTC.
2 thunderstorm wind. Local standard time, as filed.
As a result of thunderstorm wind gusts, a tree fell onto a parked car.
Thunderstorm winds gusts toppled a tree in Sergeant Bluff.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2023Every state in 2023This day in weather historyWarnings in Iowa, October 2023
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: 1145760, 1145761.