Severe Thunderstorm Warning 48, NWS Sioux Falls, SD

324 
WWUS53 KFSD 180034
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
734 PM CDT Sun May 17 2026

IAC141-180044-
/O.CAN.KFSD.SV.W.0048.000000T0000Z-260518T0100Z/
O'Brien IA-
734 PM CDT Sun May 17 2026

...THE SEVERE THUNDERSTORM WARNING FOR NORTHWESTERN O'BRIEN COUNTY IS
CANCELLED...

The severe thunderstorm which prompted the warning has moved out of 
the warned area. Therefore, the warning has been cancelled.

A Tornado Watch remains in effect until 1000 PM CDT for northwestern
Iowa.

&&

LAT...LON 4325 9558 4326 9564 4333 9571 4346 9557
      4331 9541 4330 9541
TIME...MOT...LOC 0034Z 234DEG 28KT 4332 9562 

$$

IAC143-180100-
/O.CON.KFSD.SV.W.0048.000000T0000Z-260518T0100Z/
Osceola IA-
734 PM CDT Sun May 17 2026

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 800 PM CDT
FOR EASTERN OSCEOLA COUNTY...

At 734 PM CDT, a severe thunderstorm was located over Melvin, or 8
miles southeast of Sibley, moving northeast at 30 mph.

HAZARD...60 mph wind gusts and quarter size hail.

SOURCE...Radar indicated.

IMPACT...Hail damage to vehicles is expected. Expect wind damage to 
         roofs, siding, and trees.

This severe storm will be near...
  Ocheyedan around 740 PM CDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Tornado Watch remains in effect until 1000 PM CDT for northwestern
Iowa.

Remain alert for a possible tornado! Tornadoes can develop quickly
from severe thunderstorms. If you spot a tornado go at once into the
basement or small central room in a sturdy structure.

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4325 9558 4326 9564 4333 9571 4346 9557
      4331 9541 4330 9541
TIME...MOT...LOC 0034Z 234DEG 28KT 4332 9562 

TORNADO...POSSIBLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Meyers

038 
WWUS53 KFSD 180046
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
746 PM CDT Sun May 17 2026

IAC143-180056-
/O.CAN.KFSD.SV.W.0048.000000T0000Z-260518T0100Z/
Osceola IA-
746 PM CDT Sun May 17 2026

...THE SEVERE THUNDERSTORM WARNING FOR EASTERN OSCEOLA COUNTY IS
CANCELLED...

The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning has been cancelled.  However, small hail and
gusty winds are still possible with this thunderstorm.

A Tornado Watch remains in effect until 1000 PM CDT for northwestern
Iowa.

&&

LAT...LON 4325 9558 4326 9564 4333 9571 4346 9557
      4331 9541 4330 9541
TIME...MOT...LOC 0046Z 233DEG 22KT 4337 9554 

$$

Meyers

Area Forecast Discussion
National Weather Service Sioux Falls SD
Issued by National Weather Service Rapid City SD
653 PM CDT Sun May 17 2026

.KEY MESSAGES...

- There is high confidence that severe thunderstorms will
  develop this afternoon and evening, producing large hail,
  destructive straight-line winds, and a few tornadoes. An
  Enhanced Risk (level 3 of 5) of severe storms is in place.

- A transitioning storm mode will shift hazards from large hail
  and tornadoes initially, to widespread wind damage as an
  intense line of storms tracks east of Interstate 29 this
  evening.

- A lower risk of severe weather exists late Monday afternoon
  and evening, mainly over northwest IA, before quieter weather
  moves in for the mid-week period.

&&

.DISCUSSION...
Issued at 120 PM CDT Sun May 17 2026

The short-term convective outlook presents a highly volatile
spring severe weather setup. Latest surface analysis shows a
complex pattern, anchored by a strong 994 mb low over northwest
KS. An inverted trough extended north of the low through
central SD, while a well-defined warm front stretched northeast
of the low into east central NE. A weaker low was also noted in
north central NE. Visible satellite imagery revealed stable
wave clouds advancing northeast over far northeast NE and
extreme SE SD, ahead of the advancing warm front. Regional
radar imagery showed a complex of strong to severe storms over
north central NE. This storm complex is forecast by short range
guidance to continue tracking east this afternoon, intensifying
as interacts with the richer low- level moisture pool near and
south of the warm front.

Moderate to strong instability will be in place over the
southern to eastern CWA by late afternoon with MLCAPE nearing
3000 J/kg. In addition, deep layer shear will increase to around
50 kt, coincident with a mid level speed max ejecting from the
deep upper trough to our west. As the system evolves over the
next several hours, it appears the ingredients for a significant
severe weather event will be most favored over the southern to
eastern CWA. Ahead of the main convective line, some CAMs show
supercell development along the northward advancing warm front.
These storms would present a risk of very large hail (2"+) and
tornadoes. Given the amount of low level SRH/curved hodographs
present, a couple strong tornadoes are possible. The convective
cluster currently entering our far southwest CWA should
strengthen as it shifts east, with an initial hail and tornado
threat transitioning to a damaging straight line wind threat
(70+ MPH) as it grows upscale into a squall line/QLCS. Some
line-embedded QLCS tornadoes are possible, especially for any
line segments that become oriented north/south or
northwest/southeast, given southwesterly 0-3 km shear vectors.
Timing from latest high-res guidance suggests this activity
exits to the east of our CWA late this evening.

Precipitation amounts will vary significantly based on convective
tracks, though NBM guidance and HREF probability match mean
fields project a widespread 0.50 to 1.50 inches of rainfall,
particularly across northwest Iowa and southwest Minnesota. On
Monday, the cold front finally pushes into the area. Instability
and shear are forecast to be much lower than today, however,
there will be a conditional risk of severe storms over the
eastern CWA during the late afternoon to evening, if the airmass
can destabilize sufficiently ahead of the front. SPC's Day 2
outlook indicates as Marginal Risk (level 1 of 5), for our MN
and IA counties.

Behind the departing upper wave, quasi-zonal flow sets up for
Tuesday and Wednesday, yielding quiet conditions and seasonally
cool high temperatures moderating from the upper 50s Tuesday to
mid-upper 60s Wednesday.

The next upper wave moves in for the Thursday to Friday period,
however Gulf moisture remains cutoff ahead of this system.
Evaluating the ECMWF Extreme Forecast Index (EFI) reveals no
significant climatological anomalies for precipitation or wind
across the upper Midwest during this period, reinforcing the
the idea of a low-impact system for our area. The current
forecast sticks closely to the NBM consensus, maintaining broad
20-30 percent probabilities for light rain for late Thursday
into Saturday.

By late this week and especially this weekend, temperatures
will embark on a steady upward trajectory, as the mid level flow
backs west, then southwest. The Climate Prediction Center (CPC)
6-10 day outlook favors above-normal temperatures across the
Northern Plains and Upper Midwest, which supports blended
guidance high temperatures reaching well into the 80s on
Sunday.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 650 PM CDT Sun May 17 2026

Showers and storms will continue to move eastward into MN through
the evening hours, the forecast area should be largely clear of
shower/storm activity after ~05z. Intermittent MVFR/IFR conditions
in heavy rainfall as well as hail and strong winds will accompany
the strongest storms. Widespread MVFR/IFR cigs will set in overnight
and persist through much of Monday.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.

&&

DISCUSSION...ILX/25
AVIATION...Wong

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
Issued by National Weather Service Lincoln IL
129 PM CDT Sun May 17 2026

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ038>040-050-052>071-181830-
Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee-
Buena Vista-Woodbury-Ida-Lincoln-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-Bon Homme-Yankton-
Union-
129 PM CDT Sun May 17 2026

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...This afternoon and tonight.

A significant severe weather event is possible this afternoon and
evening. Very large hail, damaging wind gusts, and tornadoes are all
possible. If you have outdoor plans know where your nearest shelter
is located. Please ensure you have multiple ways to receive warnings.
Have a plan to take shelter and act immediately if your area comes
under a severe weather warning.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Strong to severe storms are possible again Monday afternoon and
evening, particularly over northwest Iowa and southwest Minnesota.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed this afternoon and evening.

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
641 PM CDT Sun May 17 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0626 PM     Tstm Wnd Gst     2 NNE Worthington       43.65N 95.59W
05/17/2026  M59 MPH          Nobles             MN   Public

            Via personal weather station. Exact time
            estimated via radar.

&&

ak

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
642 PM CDT Sun May 17 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0626 PM     Tstm Wnd Gst     2 ENE Worthington       43.63N 95.57W
05/17/2026  M55 MPH          Nobles             MN   AWOS

            AWOS station KOTG Worthington Airport.

&&

ak

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
643 PM CDT Sun May 17 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0337 PM     Tstm Wnd Dmg     6 E Menno               43.24N 97.45W
05/17/2026                   Hutchinson         SD   Emergency Mngr

            Large garage door on outbuilding bowed in.
            Time estimated from radar.

&&

PR

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
654 PM CDT Sun May 17 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0601 PM     Hail             Wilmont                 43.76N 95.83W
05/17/2026  M1.25 Inch       Nobles             MN   Public

            mPING: Half Dollar (1.25 in.). Time
            estimated via radar.

&&

ak

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
659 PM CDT Sun May 17 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0636 PM     Hail             Sibley                  43.41N 95.75W
05/17/2026  E0.75 Inch       Osceola            IA   Public

            Report from mPING: Dime (0.75 in.). Time
            estimated via radar.

&&

ak

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
716 PM CDT Sun May 17 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0650 PM     Hail             Craig                   42.90N 96.31W
05/17/2026  E1.25 Inch       Plymouth           IA   Public

            Photo via social media. Time estimated by
            radar.

&&

ak