Thunderstorms moved out of central South Dakota into the James River Valley late in the evening. While winds were generally from 40 to 50 mph, one stronger cell produced a severe wind gust near Huron.
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The episode as NWS FSD wrote it up.
Thunderstorms moved out of central South Dakota into the James River Valley late in the evening. While winds were generally from 40 to 50 mph, one stronger cell produced a severe wind gust near Huron.
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 May 23, 10:22 PM CST, 27 minutes earlier.
AREA FORECAST DISCUSSION National Weather Service Sioux Falls SD 1122 PM CDT Sun May 23 2021 .SHORT TERM...(This Evening through Monday) Issued at 248 PM CDT Sun May 23 2021 Fairly expansive cumulus field as of mid afternoon with a few showers and thunderstorms. Most focused area of convection is along the Buffalo Ridge where better surface convergence has allowed for greater coverage. RAP mesoanalysis confirms effective deep layer shear is weak however with with MLCAPE values around 1000 J/kg, can't rule out the possibility of a storm or two pulsing to near strong/severe levels. Additionally, given the presence of a boundary, a non-zero (although extremely low) chance of a brief funnel although RAP analyzed surface vorticity is far from impressive. This will continue to progress northeastward thru the late afternoon. As we move through the evening, a pronounced wave ejecting out of the Rockies will continue to allow for expanding thunderstorm coverage across western SD and NE Panhandle with eventual upscale growth owing to a strong boundary parallel component of deep layer shear vectors. Previously mentioned wave pivots northeastward away from our coverage area and, combined with weaker instability and shear parameters with eastward extent, should result in a weakening trend of this convection as it approaches the MO River. This decrease in strength is reflected well in latest HREF guidance. With all of this said, not out of the question that areas west of the James River still stand the risk of borderline severe wind gusts before an eventual transition to more showers/embedded thunderstorms east of the James River late tonight. The eastward extent of overnight convection will have at least some impact on the forecast for Monday via influence on the eastward progression of the surface boundary and remnant outflow boundaries. This will be important as forecast soundings show fairly minimal convective inhibition and thus suspect we will likely see a fairly early agitation to the cumulus field once better solar insolation commences by late morning. Distinct mid/upper level forcing is again tough to come by but weak surface convergence along the main synoptic boundary (as well as any established outflow boundaries) should be enough to tap into the roughly 1500 J/kg of MLCAPE. Perhaps a bit better environment by late afternoon as the region starts to receiving a bit more help to finalize any needed environmental preconditioning as the right entrance region from a departing jet streak enters the picture. All of this to say that current indications are weak radar echos could very well be possible near and just ahead of the surface boundary by as early as late morning Monday with likely more established deep convection by mid to late afternoon. Better deep layer shear is again weighted post-frontal with effective shear in the warm sector generally in the 20-35 kt range. This will likely result in largely multicell clusters with perhaps some borderline supercell characteristics. With this lack of better deep layer shear, the severe threat may remain somewhat tempered although initial suspicion is that at least a couple severe level storms seem possible. Large hail up to ping pong size appears to be the primary threat with any organized cluster also posing a damaging wind threat. These threats are highlighted by a Day 2 Marginal from SPC. Temperatures a few degrees either side of 80 look reasonable for Monday with more sunshine for locations behind the boundary. .LONG TERM...(Monday Night through Sunday) Issued at 248 PM CDT Sun May 23 2021 Surface boundary looks to get pushed into NW IA by midday Tuesday although if Monday's convection is less than progged, this could be a bit slower (the opposite could also be said). This would result in continued shower/storm chances ahead of this boundary for areas toward the Hwy 20 corridor in NW IA although a bit more suitable forcing may be displayed to the south/east of our coverage area. Temperatures again in the upper 70s to mid 80s look reasonable with westerly winds. Brief period of shortwave ridging is expected by Wednesday with northeasterly winds helping to usher in cooler temperatures in the 70s and lower dewpoints. Next shortwave will be quick behind however and looks to provide a fairly good shot at widespread precipitation Wednesday night into Thursday. Better instability continues to look to be be mainly bottled up south of our area so probably more of a shower with embedded lightning setup. This would also keep temperatures rather cool on Thursday with upper 50s to mid 60s. Shortwave ridging returns for Friday and Saturday along with dry conditions and gradually warming temperatures. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 1122 PM CDT Sun May 23 2021 24.04Z regional radars show a line of showers and embedded thunderstorms from KMBG to east of K9V9 to KLBF, moving to the east-northeast around 40 mph. Made some minor adjustments to timing at KHON/KFSD, but still expect some convective activity at both sites overnight. With storms, southerly winds will shift to the west-southwest and could gust as high as 35 to 40 kts. MVFR conditions are looking less likely based on upstream observations. For KSUX, still think majority of activity should be in shower form. Additional aviation challenges exist Monday afternoon/evening with another potential line of showers and thunderstorms along a stalled front cutting across the region. Introduced VCTS at KFSD/KSUX from roughly 24.22Z to 25.02Z to highlight the threat, but adjustments are likely as details are ironed out. KHON is expected to remain dry Monday afternoon. Light southerly breezes tonight will shift to the west-southwest with showers/storms and remain from the southwest through the rest of the period with some afternoon gusts to 25 kts possible. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && SHORT TERM...Kalin LONG TERM...Kalin AVIATION...Rogers
Hazardous Weather Outlook National Weather Service Sioux Falls SD 313 PM CDT Sun May 23 2021 IAZ001>003-012>014-020>022-031-032-MNZ089-090-097-098-NEZ013-014- SDZ040-055-056-061-062-066-067-069>071-242015- Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee- Buena Vista-Woodbury-Ida-Nobles-Jackson-Pipestone-Rock-Dixon-Dakota- Brookings-Lake-Moody-McCook-Minnehaha-Turner-Lincoln-Yankton-Union- 313 PM CDT Sun May 23 2021 This Hazardous Weather Outlook is for northwest Iowa, west central Iowa, southwest Minnesota, northeast Nebraska, east central South Dakota and southeast South Dakota. .DAY ONE...This afternoon and tonight. Isolated thunderstorms are possible this afternoon and evening. Severe weather is unlikely although any stronger storms may produce small hail and gusty winds. A line of thunderstorms moves east overnight and into Monday morning. These storms are expected to weaken by time they reach Interstate 29 However, brief gusty winds to 40 mph and small hail could be possible into early Monday morning. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Scattered thunderstorms may again be possible Monday afternoon. A few strong to severe storms are possible. Additional thunderstorms are likely late Wednesday through Thursday. Severe thunderstorm risks are low. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. SDZ038-039-050-052>054-057>060-063>065-068-242015- Beadle-Kingsbury-Gregory-Jerauld-Sanborn-Miner-Brule-Aurora-Davison- Hanson-Charles Mix-Douglas-Hutchinson-Bon Homme- 313 PM CDT Sun May 23 2021 This Hazardous Weather Outlook is for central South Dakota, east central South Dakota, south central South Dakota and southeast South Dakota. .DAY ONE...This afternoon and tonight. Severe thunderstorms that develop across western South Dakota and Nebraska will track eastward late this evening. These storms may form into a line as they move east, reaching central South Dakota by 10pm and moving into the James River Valley after midnight. While this activity will begin to weaken prior to reaching the outlook area, it may still be capable of producing strong winds up to 60 mph and small hail as it moves through. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Isolated thunderstorms may again be possible Monday afternoon, however the greatest severe weather risk will fall across northwestern Iowa and northeastern Nebraska. Additional thunderstorms are likely late Wednesday through Thursday. Severe thunderstorm risks are low. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. MNZ071-072-080-081-242015- Lincoln-Lyon-Murray-Cottonwood- 313 PM CDT Sun May 23 2021 This Hazardous Weather Outlook is for southwest Minnesota. .DAY ONE...This afternoon and tonight. Scattered thunderstorms will remain possible thru the afternoon. While unlikely, a stronger storm capable of up to quarter size hail is possible along with a very low chance of a funnel cloud. Additional showers and thunderstorms are possible late tonight. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Scattered thunderstorms may again be possible Monday afternoon. A few strong to severe storms are possible. Additional thunderstorms are likely late Wednesday through Thursday. Severe thunderstorm risks are low. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The Aberdeen radar (KABR), 119 km away, was scanning. The volume nearest the first event began at 04:48 UTC.
1 thunderstorm wind. Local standard time, as filed.
Wind gust was measured by automated station KHON.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Dakota in 2021Every state in 2021This day in weather historyWarnings in South Dakota, May 2021
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: 962029.