Rainfall and additional runoff from melting snow from March 23-24, pushed the lower portions of the Big Sioux River into minor flood stage at the end of the month. Waters mainly impacted agricultural lowlands.
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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.
Rainfall and additional runoff from melting snow from March 23-24, pushed the lower portions of the Big Sioux River into minor flood stage at the end of the month. Waters mainly impacted agricultural lowlands.
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 Mar 29, 4:58 AM CST, 3 hours 2 minutes earlier.
Area Forecast Discussion National Weather Service Sioux Falls SD 558 AM CDT Thu Mar 29 2018 .SHORT TERM...(Today and Tonight) Issued at 335 AM CDT Thu Mar 29 2018 High pressure dominates the northern plains at this time. A stratus deck continues to stubbornly linger over much of the forecast area at this time, but latest satellite trends do finally showing it eroding in our western zones. This trend should continue this morning with the stratus gradually dissipating from northwest to southeast, but will be replaced by plenty of mid and upper level cloud cover moving in from the west with the next short wave. This wave is clearly shown in the mid level QG forcing from 700-500mb and moves eastward across the CWA. Its greatest impact will likely be across the southwest zones where some moisture exists up to 1km. Toward midday, south central SD may see some light rain and snow, with light rain this afternoon. With the cloud cover today, temperatures will be below normal with highs generally ranging the upper 30s to mid 40s. In addition, increased wind speeds east of Interstate 29 as those locations are still on the east side of the surface ridge giving a breezy day. Lighter winds will prevail elsewhere. Tonight, another strong mid level short wave will dive southeastward down the flow. Precipitation develops along the lower level baroclinic zone from 925-850mb, firmly placed between todays high pressure system shifting to the central plains, and a cold high moving southeastward from south central Canada. Light precipitation may scrape our far northern zones near highway 14 but any snow accumulation would be extremely minor, and likely will not collect on pavement anyway due to insufficient snow rates. .LONG TERM...(Friday through Wednesday) Issued at 335 AM CDT Thu Mar 29 2018 Clouds and winds will be on the increase on Friday, especially in the afternoon hours ahead of a strong cold front moving through the area. Have the warmest forecast highs across central South Dakota, where 925 hpa temps warm to near 10C. Further to the east across southwest Minnesota, remaining snow cover and temperatures of 3-5 C will keep highs cooler. Strong cold front will move through the region Friday night. Still appears the bulk of the precipitation will be ahead of the front as rain. As the front moves through, 925 hpa temps come crashing down and drop 10-15 C in 6 hours. In addition, winds at 925 hpa are 35- 40 knots. With the strong cold air advection coupled with strong momentum, have raised winds to near advisory criteria. Strong pressure rises behind the front die off Saturday morning and expect winds to decrease throughout the day. With the cooler air moving in, expect only a small recovery in temperatures. Very cold night night on Saturday night with mostly clear skies and light winds. Current forecast lows are about 10 degrees away from record levels. Will see temperatures moderate on Sunday into Monday ahead of a strong wave moving through the area Monday night into Tuesday. This system does not appear to be as moisture starved as the others, and appears to bring rain transitioning to snow. In addition, winds will be brisk on the backside of this disturbance, but at this juncture, do not appear to be as strong as Saturday. Additional disturbances are expected to pass through the region in northwest flow aloft Wednesday into Thursday. Timing and trajectory differences exist amongst the various solutions, so left blended pops as is for the time being. && .AVIATION...(For the 12Z TAFS through 12Z Friday morning) Issued at 556 AM CDT Thu Mar 29 2018 MVFR ceilings are exiting the forecast area at this time. They will linger at KSUX until mid morning, then scatter out of that location too as the stratus heads southward. Mid and high level cloud cover is encroaching in from the west with the next short wave. However those clouds are expected to remain VFR in this CWA. Late tonight, there are small chances for light snow in our extreme northern zones possibly sneaking into KHON between 06Z and 12Z Friday. However the more organized precip will be north of the FSD forecast area therefore the snow chance was left out of KHON at this time. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && SHORT TERM...MJ LONG TERM...BT AVIATION...MJ
Hazardous Weather Outlook National Weather Service Sioux Falls SD 412 AM CDT Thu Mar 29 2018 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ038>040-050-052>071-300915- 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-Beadle-Kingsbury- Brookings-Gregory-Jerauld-Sanborn-Miner-Lake-Moody-Brule-Aurora- Davison-Hanson-McCook-Minnehaha-Charles Mix-Douglas-Hutchinson- Turner-Lincoln SD-Bon Homme-Yankton-Clay SD-Union- 412 AM CDT Thu Mar 29 2018 This Hazardous Weather Outlook is for portions of 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 Minor flooding is occurring on several local rivers and streams because of recent rainfall and melting snow. .DAYS TWO THROUGH SEVEN...Friday through Wednesday A strong cold front is expected to move through the region Friday night. Rain may transition to snow but any accumulations are currently expected to be minimal. However, strong northwest winds of 25 to 40 mph can be expected early Saturday morning. Minor river flooding currently occurring on several local rivers may continue through the week. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
Runoff from rainfall and snow melt caused minor flooding of lowland agricultural areas along lower portions of the Big Sioux River. The river reached as high as 2.5 feet above flood stage near Akron (gage site AKRI4) by the end of the month.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Dakota in 2018Every state in 2018This day in weather historyWarnings in South Dakota, March 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: 760264.