130
FXUS63 KFSD 090133
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
833 PM CDT Tue Sep 8 2026

.KEY MESSAGES...

- Patchy fog is possible tonight across mainly northwest Iowa.
  Any fog that develops will dissipate during the morning hours.

- Severe weather possible on Friday afternoon and evening.
  Confidence is low due to the potential for a stronger cap.

- Additional very good chances (50-80 percent) for showers and
  thunderstorms return on Sunday.

- Cooler conditions arrive this weekend into early next week.

&&

.UPDATE...
Issued at 831 PM CDT Tue Sep 8 2026

The last of the rain showers have finally pushed southeast of the
forecast area this evening. Dry conditions are expected for the rest
of the night. Weak surface ridging will slide into the area tonight,
allowing for winds to go light and variable. Some residual moisture
looks to remain across mainly northwest Iowa. This looks to lead to
some patchy fog development during the overnight hours tonight. Any
fog that develops will mix out during the morning hours tomorrow.

Wednesday will be a beautiful day with highs warming to the 70s and
low 80s along with marginally breezy northwest winds. With dew
points falling to the 50s to low 60s, humidity will be much lower
than what we have experienced the past few days. High pressure
slides through the area Wednesday night, resulting in southerly
return flow for Thursday. Highs will warm a little bit more, with
all locations pushing into the 80s. The southerly winds will be more
on the breezy side with gusts up to 20-30 mph through the afternoon
hours. Dry conditions are expected for the day as well.

&&

.DISCUSSION...
Issued at 111 PM CDT Tue Sep 8 2026

The right entrance region of the upper level jet will move across
the area this evening, helping increase convergence along the low to
mid level boundary. Much drier air was filtering in behind the
surface front, with 30 and 40 degree dew points in central SD. With
1500-2000 J/kg CAPE ahead of this front and about 40 knots of deeper
layer shear, a few stronger updrafts will be possible later this
afternoon. For now the better chances appear to be from northeast NE
towards Storm Lake and points south. The main severe threat should
exit the area by early evening as cooler and drier air settles in
behind the exiting right entrance region.

Wednesday should prove to be a pleasant day with decreased humidity
and seasonally warm temperatures in the upper 70s to lower 80s.
Northwest winds may gust as high as 25 mph, with lighter winds
across northwest IA. High pressure at the surface will drift across
the area tonight and allow for some cool morning lows, mainly low to
mid 50s but a few lower spots could  see lows as cool as the upper
40s.

Upper level troughing digs across the Northern Rockies Thursday
which will swing lower level winds around to the south, allowing
for slightly warmer temperatures, generally lower to mid 80s.

As this upper level trough spreads onto the Plains Friday, an
environment that potentially supports severe weather will set up.
The challenge that day will be breaking the cap. If the cap can be
broken, 2000-3000 J/kg CAPE along with about 30-40 knots of deep
layer shear would support a few severe updrafts.

Once this front moves through Friday night, much cooler air will
settle into the region. Highs Saturday through Monday will likely be
in the 70s, with some 60s possible on Sunday. Lows each morning
should be roughly 45 to 55.

Sunday into Sunday night will see another fairly strong trough move
through which increases warm air advection and should bring fairly
widespread showers and thunderstorms. For now any sever weather
looks to remain very isolated.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 630 PM CDT Tue Sep 8 2026

Showers continue to push off to the southeast this evening. They
should be fully out of the area over the next hour or two, leaving
dry conditions for the rest of the TAF period. With clearing skies
and light and variable winds expected tonight, fog will be possible,
primarily across northwest Iowa. Any fog that does develop will have
the potential to reduce ceilings and visibilities down to
MVFR/IFR/LIFR levels. For now have only reduced KSUX`s ceilings down
to MVFR thresholds. May go lower if confidence in the fog`s placement
increases. Any fog that does develop will mix out tomorrow morning,
leaving light northwest winds for the rest of the period.

&&

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

&&

$$

UPDATE...Meyers
DISCUSSION...08
AVIATION...Meyers