Severe Thunderstorm Warning 207, NWS Sioux Falls, SD

Area Forecast Discussion
National Weather Service Sioux Falls SD
622 PM CDT Sat Jul 25 2026

.KEY MESSAGES...

- Increased confidence in severe storm chances this evening and
  early overnight. Damaging winds to 75 to 85 mph are possible.
  Hail will be a secondary threat, possibly to the size of
  quarters.

- Extreme Heat Warning through Sunday. Heat index values as high
  as 115 degrees

- While details are uncertain and confidence remains low, if
  storms develop Sunday evening into Sunday night, some may be
  strong to severe with damaging winds, isolated large hail and
  locally heavy rain possible.

- Still a good chance for highs in the 90s next week in most
  locations. Additional heat headlines are possible.

&&

.DISCUSSION...
Issued at 117 PM CDT Sat Jul 25 2026

Heat:

Not much change as dew points in the upper 60s to mid 70s provide
the area with an oppressive environment. As temperatures rise into
the 90s today and Sunday, heat indices will jump to between 100-110
degrees in most locations. The hottest conditions continue to look
to be along the James and Missouri River valleys.

For now Monday through Wednesday should see highs generally in the
90s but with a bit less humidity. This will keep the heat index in
the 90s as well. Will have to keep an eye on the dew points trends
as a few more degrees of moisture will push heat indices above 100.

A wave moving through on Wednesday will likely bring slightly cooler
air into the area so the second half of the week may not be quite as
hot.

Thunderstorms:

Overall a capping inversion will be in place for the area through
the afternoon, so development is not expected. One exception may be
in and around Gregory/Charles Mix counties where model soundings
hint at possibly breaking the cap. If this can happen, an isolated
storm with the potential for wind gusts around 70 mph are possible.
CAPE values only running about 500-1500 J/kg with fairly weak shear,
but with a very dry subcloud layer. Otherwise, development should
take place west of the area and move in after about 6-8 pm. This
cluster of storms will likely be a bit pulsy, but with better
instability and still a fairly significant sub cloud dry layer wind
gusts to 75 mph will be likely with the potential for a cold pool to
develop. Hail to the size of quarters will also be possible, but
wind will be the main threat. Many of the latest 12z models are
jumping on this wind threat and the HRRR has been very consistent
bringing this wind threat right down I-90 this evening.

Some lingering showers are possible from midnight into early Sunday
morning, but are not expected to be severe and may even have trouble
reaching the ground with a significant dry layer below. Still a lot
of question marks regarding the severe threat tomorrow afternoon and
tomorrow night. For now a significant amount of dry air in the low
to mid levels should provide enough capping to avoid afternoon
thunderstorm development. If a storm could develop, 2000 J/kg CAPE,
30-40 knots of deep layer shear and a significant dry layer in the
lower levels would support wind gusts to 75 mph and hail to the size
of half dollars. Otherwise during the later evening and overnight
hours the models are really backing off on any potential for the
area and keeping the isolated to scattered activity to the northeast.

A wave will move through the area Wednesday into Thursday morning
and be the next chance for showers and thunderstorms. This will be
the next threat for possible severe storms. The main threat for
showers and thunderstorms should come on Thursday.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 616 PM CDT Sat Jul 25 2026

Scattered convection will continue to develop and move east this
evening. High winds will pose the greatest risks, with potential
for 60+ mph winds moving through the area.

This convection will likely arrive into Huron by 00Z, with
potential for convection to reach FSD around 02Z. MVFR ceilings
are expected in convection, though there remains a high degrees
of uncertainty on if storms will reach the airport.

Sioux City poses even more uncertainty, with most guidance
suggesting convection weakens by time it arrives. At a minimum,
shower activity may continue into Sunday morning.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Extreme Heat Warning until 8 PM CDT Sunday for SDZ038>040-050-
     052>071.
MN...Extreme Heat Warning until 8 PM CDT Sunday for MNZ071-072-080-
     081-089-090-097-098.
IA...Extreme Heat Warning until 8 PM CDT Sunday for IAZ001>003-
     012>014-020>022-031-032.
NE...Extreme Heat Warning until 8 PM CDT Sunday for NEZ013-014.

&&

DISCUSSION...08
AVIATION...Dux

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
525 PM CDT Sat Jul 25 2026

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ071-262230-
Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee-
Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson-
Pipestone-Rock-Dixon-Dakota-Union-
525 PM CDT Sat Jul 25 2026

This Hazardous Weather Outlook is for northwest Iowa, west central
Iowa, southwest Minnesota, northeast Nebraska and southeast South
Dakota.

.DAY ONE...Tonight.

Heat index values between 100 and 110 will continue this evening.

Scattered thunderstorms may approach after dark. These storms may be
in a weakening phase, but could still bring 60 to 70 mph winds as
they move through.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Heat index readings will again climb between 100 to 110 degrees
Sunday afternoon and evening.

While uncertain, isolated to scattered thunderstorms may redevelop
Sunday late afternoon and evening. Large hail and 70 mph winds may be
possible.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed after 10pm.

SDZ038>040-050-052>070-262230-
Beadle-Kingsbury-Brookings-Gregory-Jerauld-Sanborn-Miner-Lake-Moody-
Brule-Aurora-Davison-Hanson-McCook-Minnehaha-Charles Mix-Douglas-
Hutchinson-Turner-Lincoln-Bon Homme-Yankton-Clay-
525 PM CDT Sat Jul 25 2026

This Hazardous Weather Outlook is for central South Dakota, east
central South Dakota, south central South Dakota and southeast
South Dakota.

.DAY ONE...Tonight.

Scattered severe storms will try to develop and move eastward this
evening and into the early overnight hours. Hail risks of ping pong
ball size, and straight line winds of 75 mph or greater will be
possible.

Heat index values as high as 110 degrees will continue this evening.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Heat index readings will again climb between 100 to 110 degrees
Sunday afternoon and evening.

While uncertain, isolated to scattered thunderstorms may redevelop
Sunday late afternoon and evening. Large hail and 70 mph winds may be
possible.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will be needed through 12am.

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