Alert archive / South Dakota / Severe Thunderstorm Warnings in 2026

Severe Thunderstorm Warning 35, NWS Sioux Falls, SD

May 17, 2026Gregory County, South Dakota

NWS Sioux Falls, SD issued this severe thunderstorm warning at May 17, 2026, 1:09 PM CDT for Gregory County, South Dakota. It was in force for 51 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: May 17, 2026, 1:09 PM CDT (18:09 UTC)
Expired: May 17, 2026, 2:00 PM CDT
In force: 51 min
Issued by: NWS Sioux Falls, SD
Area: Storm-based polygon
Hail: 1.25 in
Wind: 60.0 mph

County Gregory County, SD

The radar

The North Platte radar (KLNX), 178 km from the middle of the area, began a volume at 18:12 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Aberdeen, SD (KABR), launched 12:00Z, 6.2 hours before the alert went out and 200 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 2103 m above ground
0-6 km bulk shear: 54 kt
0-1 km storm-relative helicity: 372 m²/s²
0-3 km storm-relative helicity: 379 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, 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 this severe thunderstorm warning went out at May 17, 6:08 AM CDT, 7 hours 1 minute earlier.

Area forecast discussion, May 17, 6:08 AM CDT, 7 hours 1 minute before

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Hazardous weather outlook, May 17, 4:11 AM CDT, 8 hours 58 minutes before

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The office that day

Everything else NWS Sioux Falls, SD issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 17, 1:10 AM CDT	Flash Flood Warning	FSD	Union	4 hr
May 17, 2:10 PM CDT	Severe Thunderstorm Warning	FSD	Charles Mix, Gregory	50 min
May 17, 2:15 PM CDT	Severe Thunderstorm Warning Considerable damage threat	FSD	Aurora, Brule, Charles Mix, Douglas	45 min
May 17, 2:49 PM CDT	Severe Thunderstorm Warning Considerable damage threat	FSD	Bon Homme, Hutchinson, Yankton	41 min
May 17, 2:50 PM CDT	Tornado Warning	FSD	Bon Homme, Charles Mix, Hutchinson	40 min
May 17, 3:23 PM CDT	Tornado Warning	FSD	Hutchinson, Turner, Yankton	52 min
May 17, 3:28 PM CDT	Severe Thunderstorm Warning Destructive damage threat	FSD	Bon Homme, Clay, Hutchinson, Turner, Yankton	47 min
May 17, 3:35 PM CDT	Tornado Warning	FSD	Hutchinson, Turner	28 min
May 17, 3:59 PM CDT	Severe Thunderstorm Warning Destructive damage threat	FSD	Lincoln, Turner	46 min
May 17, 4:18 PM CDT	Severe Thunderstorm Warning Considerable damage threat	FSD	Lincoln, Minnehaha, Turner	42 min
May 17, 4:27 PM CDT	Tornado Warning	FSD	Lincoln, Minnehaha	48 min
May 17, 4:56 PM CDT	Severe Thunderstorm Warning Considerable damage threat	FSD	Minnehaha	49 min
May 16, 11:14 PM CDT	Severe Thunderstorm Warning	FSD	Clay, O'Brien	16 min
May 17, 5:43 PM CDT	Severe Thunderstorm Warning Considerable damage threat	FSD	Lyon, Osceola	62 min
May 17, 5:56 PM CDT	Severe Thunderstorm Warning	FSD	Lyon, O'Brien, Osceola, Sioux	27 min
May 17, 6:30 PM CDT	Severe Thunderstorm Warning Considerable damage threat	FSD	Dickinson, Osceola	75 min
May 17, 6:33 PM CDT	Severe Thunderstorm Warning	FSD	Plymouth, Sioux	57 min
May 17, 5:33 PM CDT	Tornado Warning	FSD	Nobles, Rock	42 min
May 17, 6:12 PM CDT	Tornado Warning	FSD	Jackson, Nobles	48 min
May 17, 6:57 PM CDT	Tornado Warning	FSD	Cottonwood, Jackson	48 min

Nearby

Severe Thunderstorm Warnings in South Dakota, 2026 Every severe thunderstorm warning in 2026

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.