399
FXUS63 KFSD 251141
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
641 AM CDT Sat Jul 25 2026

.KEY MESSAGES...

- Areas of fog, locally dense, will impact areas east of Hwy 81
  early this morning. Fog is expected to lift by mid morning.

- Extreme Heat Warning for areas for areas south of I-90 and
  along/west of Hwy 75 this afternoon into Sunday evening.
  Elsewhere a Heat Advisory remains in effect. Heat indices
  will peak in the upper 90s to near 110F each day, hottest in
  the warning area. If confidence in higher heat indices Sunday
  increases, additional upgrades are possible.

- Storm chances and associated risks for damaging wind have
  increased for this evening into the early overnight. Pockets
  of wind gusts exceeding 75 mph are possible if storms become
  sufficiently organized.

- While details are uncertain, 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.

&&

.UPDATE...
Issued at 520 AM CDT Sat Jul 25 2026

A couple of changes for the weekend, one pertaining to the heat
and humidity, and the second with growing storm chances tonight.

HEAT: Confidence has grown that heat indices will top 105F for
many areas south of I-90 today and Sunday, mainly over our SD
counties, but also into the Highway 75 corridor in northwest IA
(roughly Rock Rapids to Sioux City). With little overnight
relief as temperatures/heat indices remain above 70F, these
areas were upgraded to an Extreme Heat Warning from Noon today
through 8 pm Sunday.

Sunday is a little more uncertain over the remaining Heat
Advisory area, particularly in our east as remnants from
tonight`s storms could have an impact on potential warming. For
this reason, opted to leave the Heat Advisory in place for now.
However, if confidence grows that we`ll see heat indices top
105F, we could see additional upgrades to an Extreme Heat
Warning for some locations. At this time, this appears to be
more likely in locations west of Highway 81 (toward the James
River Valley) than in southwest Minnesota and our remaining
northwest Iowa counties.

STORMS: While fine details in timing, track and strength are
still being worked out, confidence is increasing that we could
see a cluster of storms move east out of central South Dakota
this evening. There has been modest agreement among the CAMs in
showing a bowing line push east across our forecast area into the
early overnight. If the storms become well-organized, pockets of
damaging wind, locally in excess of 75 mph, will be possible. The
latest Day 1 SPC outlook expanded the Level 1 of 5 risk across
our entire forecast area, with a Level 2 of 5 risk in our far
west (west of Huron to Lake Andes).

Details are much more uncertain in how storm chances will evolve
through Sunday and Sunday night. Some solutions show isolated
storms developing along a weak boundary pushing into eastern SD
late Sunday afternoon/early evening, while others remain dry
into the evening with a cluster of storms developing in northern
to central Minnesota overnight and diving south. All in all, a
lower confidence severe risk which will be refined in later
forecasts.

&&

.DISCUSSION...
Issued at 1259 PM CDT Fri Jul 24 2026

Heat Concerns:

Heat and humidity build back into the area this weekend, with
afternoon and evening heat indices around a 100 or more for most
locations both Saturday and Sunday. Confidence in higher heat
indices for this weekend compared to last weekend is a higher as dew
points look to climb into the lower to mid 70s, which can feel very
oppressive. One limiting factor may be wildfire smoke, but for now
the expectations are that the smoke will be somewhat limited so the
effect on temperatures will likely not be that great. Will have a
heat advisory area wide for the weekend with some potential for
additional heat headlines next week. As confidence grows, a heat
warning may be needed along the James and Missouri River Valleys
Saturday and Sunday where heat indices could climb to around 110.
Most days next week look to have highs in the 90s, so even without
headlines will still be very warm each day.

Thunderstorm concerns:

The latest models continue to hint at isolated thunderstorm
potential Saturday evening and early overnight. For now capping
looks to be a problem, but a weak wave is expected to move into
central SD late afternoon so development may occur to the west of
the Mo River. As the wave shifts east isolated development will
remain possible. Right now the main concerns look to be quarter
sized hail and wind gusts to 65 mph.

Another piece of energy moves into the area on Sunday and should
bring another chance for some isolated severe storms. The better
shear and instability look to reside over southwest MN and this
should be the higher threat for severe storms. Will also need to
keep an eye out for south central SD where the cap could be broken
and an isolated strong to severe storm could develop. Overall there
may be enough dry air in the low levels to really limit the
instability and them main concern would be wind if something could
develop. Confidence for both Saturday and Sunday are fairly low.

Other concerns:

The only other real concern will be the potential for some fog later
tonight into Saturday morning. The better chances will be in
northwest IA, northeast NE and far southeast SD. For now not looking
like widespread dense fog.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 640 AM CDT Sat Jul 25 2026

LIFR-VLIFR stratus and fog blanket areas east of U.S. Highway 81
early this morning. This is currently expected to slowly erode
with improving conditions from west to east through the morning.
The remainder of the TAF period should see VFR conditions
prevail.

A cluster of thunderstorms may move east across the area during
the evening to early overnight hours (26/02Z-07Z). This cluster
could bring erratic wind gusts in excess of 50kt, with KHON and
KFSD standing the better chances to be impacted.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory from noon today to 8 PM CDT Sunday for
     SDZ038>040-052>062-066-067.
     Extreme Heat Warning from noon today to 8 PM CDT Sunday for
     SDZ050-063>065-068>071.
MN...Heat Advisory from noon today to 8 PM CDT Sunday for MNZ071-
     072-080-081-089-090-097-098.
IA...Heat Advisory from noon today to 8 PM CDT Sunday for
     IAZ001>003-013-014-021-022-032.
     Extreme Heat Warning from noon today to 8 PM CDT Sunday for
     IAZ012-020-031.
NE...Extreme Heat Warning from noon today to 8 PM CDT Sunday for
     NEZ013-014.

&&

$$

UPDATE...JH
DISCUSSION...08
AVIATION...JH