Severe Thunderstorm Warning 232, NWS Sioux Falls, SD

759 
WWUS53 KFSD 180644
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
144 AM CDT Tue Aug 18 2026

SDC003-015-035-073-180700-
/O.CON.KFSD.SV.W.0232.000000T0000Z-260818T0700Z/
Davison SD-Aurora SD-Jerauld SD-Brule SD-
144 AM CDT Tue Aug 18 2026

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 200 AM CDT
FOR NORTHWESTERN DAVISON...AURORA...SOUTH CENTRAL JERAULD AND EASTERN
BRULE COUNTIES...

At 144 AM CDT, severe thunderstorms were located along a line
extending from near Storla to near White Lake to near Grass Ranch
Colony, moving southeast at 45 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.

Locations impacted include...
  Plankinton, Mount Vernon and Loomis.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

To report severe weather contact your nearest law enforcement agency.
They will send your report to the National Weather Service office in
Sioux Falls.

&&

LAT...LON 4381 9922 4398 9873 4388 9833 4385 9833
      4386 9825 4381 9807 4358 9854 4349 9883
      4350 9890
TIME...MOT...LOC 0644Z 308DEG 40KT 4387 9831 4369 9868 4361 9895 

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

$$

Samet

600 
WWUS53 KFSD 180659
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
159 AM CDT Tue Aug 18 2026

SDC003-015-035-073-180709-
/O.EXP.KFSD.SV.W.0232.000000T0000Z-260818T0700Z/
Davison SD-Aurora SD-Jerauld SD-Brule SD-
159 AM CDT Tue Aug 18 2026

...THE SEVERE THUNDERSTORM WARNING FOR NORTHWESTERN DAVISON...
AURORA...SOUTH CENTRAL JERAULD AND EASTERN BRULE COUNTIES WILL EXPIRE
AT 200 AM CDT...

The storms which prompted the warning have weakened below severe
limits, and no longer pose an immediate threat to life or property.
Therefore, the warning will be allowed to expire.  However, gusty
winds up to 55 mph are still possible with these thunderstorms.

To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
Sioux Falls.

&&

LAT...LON 4381 9922 4398 9873 4388 9833 4385 9833
      4386 9825 4381 9807 4358 9854 4349 9883
      4350 9890
TIME...MOT...LOC 0659Z 321DEG 35KT 4377 9820 4359 9857 4351 9884 

$$

Samet

Area Forecast Discussion
National Weather Service Sioux Falls SD
101 AM CDT Tue Aug 18 2026

.KEY MESSAGES...

- Isolated to scattered storms are ongoing this evening, through
  development remains very uncertain. Risks of 1" hail and 60
  mph will be possible.

- Greater storm potential after midnight and through the
  overnight. Initial supercells are capable of producing 1-2"
  hail and wind gusts to 65 mph. Storms gradually grow into
  broken lines with a few bowing segments. Risks become wind
  gusts to 70 mph and marginal hail.

- Lingering rain early Tuesday will push the greatest risk of
  severe storms Tuesday further south. However cooler
  temperatures and clouds may linger deeper into the day.

- Rain chances persist Wednesday and Thursday, though storm
  track leads to lower confidence in where rain may fall.

&&

.UPDATE...
Issued at 918 PM CDT Mon Aug 17 2026

Showers and thunderstorms have moved into the western portion of our
CWA. While the convective environment is largely favorable, the
forcing from the prefrontal trough is weak and mid-level lapse rates
are decreasing. So while there is still potential for an isolated
strong to severe storm, the confidence in severe weather with these
storms is low. Should a severe storm manage to form threats include
hail to the size of a quarter and wind gusts to 60 mph. These storms
will continue to weaken and dissipate as they move southeast through
the late evening.

Another round of potentially strong to severe thunderstorms are
possible through the overnight. An upper shortwave and associated
cold front will push into central South Dakota around midnight. Deep
layer shear remains strong and the LLJ will be increasing. Though
forcing with this round will be stronger, instability, and lapse
rates will be decreasing. What this means is most likely upon
convection initiation strong to severe supercells are possible with
hail 1-2" and wind gusts to 60-65 mph. As the storms progress
southeast they will transition to elevated line segments, some with
bowing structures. The threat will then transition to a wind threat
with gusts of 70 mph possible. For much of the northern part of the
CWA, storms will be clear around 7am. For areas along the southern
Missouri River and northwest Iowa, storms may linger into mid-
morning Tuesday. Lingering clouds through the day and light
northerly winds will keep highs in the upper 70s to low 80s.

&&

.DISCUSSION...
Issued at 132 PM CDT Mon Aug 17 2026

THIS AFTERNOON: Convection risks remain the primary focus in the
upcoming 24 hour period, as there continues to be uncertainty on if
we can advect sufficient moisture northward, and provide enough
focus of lift. Visible satellite this afternoon shows two areas
of interest, one area of ACCAS across northeastern South Dakota
and west central Minnesota, driven by 700 mb winds over the
crest of the Ridge. A second area of ACCAS drifting eastward out
of the Badlands area. At the surface, one concern has been a
slower arrival of boundary layer moisture as surface dewpoints
continue to linger in the upper 50s to lower 60s. Further south,
models continue to overestimate dew points in NE/KS, providing
some doubt on if the lower 70 dewpoints advertised by "high
instability" models can be realized.

The projections into the evening remain slightly uncertain with
several focusing mechanisms available.  A surface trough extending
from NW Minnesota into NE South Dakota and central South Dakota will
provide some minor convergence (focused greater over NW Minnesota
and eastern North Dakota).  A weaker pre-frontal trough in the NE
Panhandle into the Sandhills could also serve as a focal point.
Finally, a few storms may also develop over the Minnesota River
valley downstream of the Buffalo Ridge. Any storm that develops off
of these features will likely produced an increased risk for 1-2"
hail, but also 60-70 mph winds as MLCAPE pushes 2000+ J/KG and
effective shear climbs towards 40 knots.  Gradual east southeast
storm tracks within the mean flow are likely which could put
portions of SW Minnesota and the MO River valley into a higher early
evening risk. However the likely overestimation of surface dew
points, poor focus of convergence, and weak inhibition, may
also work to prohibit convection over a large part of the Tri-
State area into the evening.

Further west, additional isolated to scattered convection may form
over the western High Plains late this afternoon and evening
slightly stronger synoptic lift enters the area.  One or more
clusters of storms could reach the western CWA by mid-late evening,
bringing risks lower risk for hail, but higher risks for a few
stronger wind gusts. There continues to be some agreement in
mesoscale and lower resolution guidance that a subtle wave crossing
the Dakotas could keep scattered convection risks moving through the
CWA until at least 4am.  Weakening instability, and worsening lapse
rates should result in fewer strong to severe storms by daybreak
Tuesday. All this to say, coverage of this activity remains highly
in doubt, which will keep areal PoPs lower in general.

TUESDAY: Latest guidance continues to trend the greatest risks for
severe convection southward on Tuesday.  Overnight convection, along
with the passing shortwave should stabilize the area
considerably by daybreak, with a lingering marginal risks for
some crossover hail risks near 12Z. We may however see quite a
bit of stratus behind this wave, suggesting cooler than normal
temperatures into the afternoon.

WEDNESDAY-THURDAY: Upper troughing moving into Hudson Bay will
sharpen the NW flow over the Plains slightly by mid-week.
EC/GFS indicates vorticity crossing from the Pacific Northwest
through the Northern Rockies early on Wednesday pushing mid-lvl
lift towards the region early Wednesday. Differences on the
track of this wave keep PoPs lower, with GEFS/GFS further
northeast, and the EC leading to more impact through central
Nebraska instead. Another wave, along with a weak frontal
boundary approach Thursday afternoon. Depending on the amount of
inhibition nearby, a few thunderstorms could form along this
boundary late in the day.

FRIDAY-SUNDAY: Mid-lvl heights rise and the ridge sharpens over the
Rockies as we move into next weekend.  This transition of mid-lvl
flow could bring one final risk for elevated showers/TSRA early
Friday, but generally quiet and dry conditions then develop
into the weekend. Temperatures however will fall more under the
influence of Canadian high pressure in the Dakotas, suggesting
highs may stay in the upper 70s to lower 80s.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1259 AM CDT Tue Aug 18 2026

VFR to MVFR conditions expected for this period. Two areas of
showers and thunderstorms are ongoing at issuance. One area along
the southern Missouri River is moving southeast into northwest Iowa.
Short term guidance is in low agreement on thunderstorm evolution
and uncertainty is high. Current mesoanalysis indicates the
southerly storms are becoming elevated, which will reduce the
overall severe threat. Still, wind gusts up to 60 mph and marginally
severe hail remain possible through the next couple hours.

The second is just reaching the western border of the CWA between
Huron and Chamberlain. These storms are showing signs of upscale
growth into broken lines. These will continue to progress southeast
through the overnight hours. Currently these storms are
producing gusts of 45-50 mph. As the LLJ begins to increase
these storms have the potential of increasing in severity.
Should a more organized line with bowing segments form, severe
winds to 70 mph are possible.

All storms should be clear of the region by late morning Tuesday.
The remainder of the period should be dry with light winds. Clouds
will slowly break up through the afternoon.

&&

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

&&

UPDATE...AJP
DISCUSSION...Dux
AVIATION...AJP

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
113 AM CDT Tue Aug 18 2026

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ038>040-050-052>071-190615-
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-
113 AM CDT Tue Aug 18 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...Tonight.

Strong to severe storms are possible overnight tonight. These storms
could produce wind gusts to 70 mph and marginally severe hail.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Scattered thunderstorm risks continue through Wednesday. Tuesday's
risk looks to be along and south of I-90 in the afternoon into the
evening.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed.