Prolonged upslope rain showers with embedded thunderstorms dropped one to three inches of rain across northern Lawrence and southern Butte Counties. Runoff from the heavy rain, combined with saturated soils and locally steep terrain, led to flooding in southern Butte County.
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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 UNR wrote it up.
Prolonged upslope rain showers with embedded thunderstorms dropped one to three inches of rain across northern Lawrence and southern Butte Counties. Runoff from the heavy rain, combined with saturated soils and locally steep terrain, led to flooding in southern Butte County.
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 Rapid City, SD wrote its last area forecast discussion before the first event at May 16, 10:29 AM MST, 46 minutes earlier.
Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 1129 AM MDT Sat May 16 2020 .DISCUSSION...(Today Through Friday) Issued at 151 AM MDT Sat May 16 2020 Water vapor shows upper low over southeast MT with upper ridge over the far western CONUS. Ejecting short wave resulting in showers/isolated thunder over our eastern third of zones early this morning. At the surface, low is centered over the NEB panhandle with inverted trof extending northeast into southwest/south central SD, coinciding well with the most concentrated area of precip. Northeast upslope flow resulting in developing fog especially along the northeastern foothills. Will continue to monitor the development of fog early this morning, which has the potential to be dense around the northern/eastern foothills. Upper low advances slowly southeast across western/central SD today. Morning showers/isolated thunder will be most concentrated over central SD, but steep lapse rates and relatively low MLCAPE will lead to widespread activity across the majority of the area by this afternoon. Best chances for thunder will generally be from around and to the south/east of the Black Hills. Showers end by early evening over central SD, with clearing and chilly conditions by Sunday morning with surface ridge over western SD. Upper low digging along the west coast will allow upper ridge to become highly amplified as it builds through the Rockies into the northern Plains Sunday and Monday. Result will be dry and much warmer temps early next week, with highs into the 80s Monday and especially Tuesday. Ridge shifts east late Tuesday with deep upper trof evolving over the western CONUS. Precip chances will return late Tuesday, and especially Wednesday, as negatively tilted trof swings northeast into the northern plains. At this time, Wednesday has the potential to be a fairly active severe weather day. The pattern then looks to become drier by the tail end of the week as main trof lifts to our north. After a very warm start to the week with temps well above climo, slightly cooler temps expected by late week with temps near to slightly above climo. && .AVIATION...(For the 18Z TAFS Through 18Z Sunday) Issued At 1115 AM MDT Sat May 16 2020 Widespread MVFR conditions in fog, low clouds, and showers will continue this afternoon across much of the CWA, but conditions will gradually improve to VFR towards evening for most of the area. The exception will be south central SD, where precipitation and fog will persist the night. A few isolated thunderstorms will be possible this afternoon. Although aforementioned improvement in conditions is expected this evening for most places, light winds and plenty of moisture may result in fog redevelopment for some locations, mainly the southern and central parts of the western SD plains. Current thinking is that fog will stay out of KRAP and KGCC, but those areas may be on the edge of the fog. Sunday morning, southeasterly winds will begin to increase, especially across northeastern WY and northwestern SD. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && DISCUSSION...Johnson AVIATION...Pojorlie
Hazardous Weather Outlook National Weather Service Rapid City SD 1133 AM MDT Sat May 16 2020 SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-WYZ054>058- 071-171300- Harding-Perkins-Butte-Northern Meade Co Plains-Ziebach- Northern Black Hills-Northern Foot Hills-Rapid City- Southern Foot Hills-Central Black Hills-Southern Black Hills- Custer Co Plains-Pennington Co Plains-Haakon-Fall River- Oglala Lakota-Jackson-Bennett-Mellette-Todd-Tripp- Sturgis/Piedmont Foot Hills-Southern Meade Co Plains- Hermosa Foot Hills-Northern Campbell-Southern Campbell- Western Crook-Wyoming Black Hills-Weston-Northeastern Crook- 1133 AM MDT Sat May 16 2020 /1233 PM CDT Sat May 16 2020/ This Hazardous Weather Outlook is for western South Dakota and northeastern Wyoming. .DAY ONE...This Afternoon and Tonight Scattered showers with isolated thunderstorms are expected throughout the day before ending from west to east this evening. Severe storms are not expected. .DAYS TWO THROUGH SEVEN...Sunday through Friday After drier conditions from late weekend through the start of next week, an active pattern will bring additional chances for thunderstorms beginning Tuesday afternoon, some of which could be strong to severe. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today. && Stay tuned to NOAA weather radio for further updates...or check our web site at weather.gov/rapidcity
The Rapid City radar (KUDX), 91 km away, was scanning. The volume nearest the first event began at 18:13 UTC.
1 flash flood. Local standard time, as filed.
Runoff from heavy rain flooded Crooked Oaks Road just south of Snoma Road. Gravel was washed off the road and the road was impassable for a couple of hours.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Dakota in 2020Every state in 2020This day in weather historyWarnings in South Dakota, May 2020
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: 883001.