Severe Thunderstorm Warning 238, NWS Sioux Falls, SD

Area Forecast Discussion
National Weather Service Sioux Falls SD
654 AM CDT Tue Jul 29 2025

.KEY MESSAGES...

- More isolated to scattered thunderstorms are expected this
  evening and overnight mainly along and south of I-90. A few
  storms could become severe with large hail and damaging winds
  being the primary threats. Locally heavy rainfall will be a
  secondary threat.

- Next shower and thunderstorm chances likely occur over the
  weekend. However, uncertainty remains in the coverage and
  severity of developing activity.

- Temperatures will trend below normal headed into the weekend
  with highs mainly in the 70s and low 80s.

&&

.DISCUSSION...
Issued at 350 AM CDT Tue Jul 29 2025

TODAY & TONIGHT: A slightly cooler day ahead! Taking a look at
satellite imagery, mostly clear conditions have returned to the area
with a few lingering areas of stratus west of the James River. While
we could see this area of stratus expand into areas north of I-90
through daybreak, should see most areas break free closer to mid-
morning. From here, slightly cooler temperatures are ahead as a
combination of northerly to northeasterly surface winds and
lingering areas of wildfire smoke aloft keep our temperatures in the
80s to low 90s with the warmest conditions south of U.S. Highway-18.
With this and dewpoints in the upper 60s to mid 70s this evening,
the stage is set for our next precipitation chances (30%-70%).

Looking aloft, isolated showers and thunderstorms likely start
across central SD by late afternoon as a mid-level wave traverses
the state. As this wave intersects a southward progressing 925-850
mb boundary in the warm sector, should see coverage rapidly expand
mainly across areas along and south of I-90 during the evening
hours. This developing activity will likely progress to the east-
southeast with the boundary and inverted trough during the overnight
hours before exiting our area by Wednesday morning. Shifting to the
severe risk, while the better shear will be slightly offset from the
better instability; there should be just enough co-location along
and south of I-90 for a few isolated to scattered strong storms to
develop. With plenty of instability (2000-3000 J/kg) and lapse rates
closer to 7-8 degrees C/km, any initial semi-discrete storms will be
capable of producing up to ping-pong ball sized hail (1.5").

As coverage expands and things grow more upscale overnight, should
see the threat transition to strong winds with gusts up to 65 mph
possible. Lastly, 10-12 kft warm cloud depths and PWATs between
1.5 to 2 inches (90th percentile) at times will lead to pockets
of moderate to heavy rainfall developing mainly across areas
south of Highway-18. With this in mind, if "training" occurs
across the same areas over prolonged periods of time, there
could be some flash flooding concerns.

WEDNESDAY ONWARDS: Heading into the midweek, any lingering shower
activity will likely persist through the morning hours of Wednesday
before pushing to our southeast. From here, fall-like temperatures
are ahead as lingering cold air advection (CAA) and easterly to
northeasterly winds keep our temperatures locked into the 70s
through Thursday. As upper-level ridging builds into the northern
plains by Friday, our precipitation chances west of Highway-281 will
increase over the weekend as a stationary boundary gradually
progresses into our area. While the severity of this activity
remains uncertain at this time, decided to leave the default NBM
pops in for this period. Lastly, we'll likely see the cooler string
of temperatures continue through at least Sunday with highs mainly
in the 70s to low 80s

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 640 AM CDT Tue Jul 29 2025

VFR conditions with occasional MVFR to IFR conditions will be
possible this TAF period. Taking a look at satellite imagery,
MVFR to IFR stratus continues to fill in along a Gregory, SD to
Marshall, MN line this morning with pockets showers and
thundershowers. Expect this developing activity to persist
through the mid to late morning before dissipating. From here,
we'll likely see the shower and thunderstorm chances increase
from the late afternoon through the overnight hours which will
promote MVFR to IFR ceilings/vsbys at times. Otherwise, light
northeasterly winds will continue across the area today to end
the TAF period.

&&

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

&&

DISCUSSION...05
AVIATION...05

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
402 AM CDT Tue Jul 29 2025

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ038>040-050-052>071-300915-
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-
402 AM CDT Tue Jul 29 2025

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...Today and tonight.

Isolated to scattered thunderstorm will develop along and south of
I-90 from the late afternoon through the overnight hours. A few
stronger storms will be possible with the main concerns being up to
ping-pong ball (1.5") sized hail and damaging winds up to 65 mph.
Pockets of locally heavy rainfall will be a secondary threat.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.