462
FXUS63 KFSD 140557
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1257 AM CDT Fri Aug 14 2026

.KEY MESSAGES...

- Areas of low stratus will spread from south to north through
  Friday morning, with low confidence on how quickly this erodes
  into Friday afternoon. This may be a recurring theme through
  the weekend.

- Patchy fog is possible mainly over the higher elevations of
  southwest Minnesota and adjacent areas of east-central South
  Dakota through early this morning Locally dense fog can`t be
  ruled out (20-40% chance).

- Scattered showers and thunderstorms will be possible early
  this morning. The better chances will be in northeast NE and
  northwest IA. The main threat will be locally heavy rain.

- Near to below normal temperatures through most of next week.
  Periodic showers and storms expected. Humidity lingers.

&&

.UPDATE...
Issued at 924 PM CDT Thu Aug 13 2026

No major changes to the forecast for tonight and tomorrow. An
upper wave moving in from the southwest will help kick off some
showers and elevated thunderstorms into the Highway 20 corridor
after about 3 am. Heavy rain continues to be the main concern
with this activity given the tall and relatively skinny CAPE
profiles and sufficiently deep warm cloud layers. Most areas
that see these showers and storms will see up to a half an inch
of rain, but areas that see a couple of storms move through
could pick up isolated pockets of 1-2 inches, with maybe a spot
or two reaching up to 3 inches. This activity should quickly
weaken as it moves north-northeast across the area as storms run
into less and less instability.

Looking across other areas tonight, patchy fog is possible
mainly in the higher elevations of the Buffalo Ridge and Coteau
des Prairies, with about a 30-50% chance of locally dense fog
especially where winds go calm to very light. Temperatures
across the area should stay in the 60s for the most part by
sunrise Friday. A cloudy day is expected on Friday, keeping high
temperatures in the 70s across the area. A weak surface low
looks to move across the region and this could help induce
additional showers in the afternoon and depending on the degree
of clearing we can get from the low clouds, perhaps a
thunderstorm or two. Once again CAPE profiles and weak shear
would suggest heavy rain is the main concern if these
thunderstorms develop as opposed to severe weather. The better
chances for thunderstorms will be east of I-29 and especially
into northwest Iowa.

&&

.DISCUSSION...
Issued at 118 PM CDT Thu Aug 13 2026

Upper level flow becomes a bit more southwesterly tonight into
Friday, which will allow a weak wave to drift north into the area.
With an elevated 1000-1500 J/kg CAPE, a freezing level around 14 kft
and weak shear, locally heavy rain with slow moving storms will be
the main concern. This weak mid to upper level support lingers
into the afternoon and early evening, especially across parts of
northwest IA, and may allow for additional showers and isolated
thunderstorms. One note, the LLJ and 850 mb boundary looks to
remain just south of the area so the pockets of heavier rain may
stay just south as well. To the northwest of northwest IA weak
capping may keep the activity more limited. For now severe
weather very unlikely and flash flooding threats also look low.

Additional weak mid and upper level support moves through the area
later Friday night into Saturday and may bring additional showers
and isolated thunderstorms. Severe weather and flash flooding appear
very unlikely.

One common theme for Friday into the weekend will be persistent and
potentially difficult to dissipate stratus and patchy fog. Weak low
level flow and some residual boundary layer moisture from the latest
rainfall may help keep this stratus potential in place until a bit
stronger push of drier air can move into the area. Sunday does look
like the day with the lowest threat for any showers and storms.

Monday will see a west northwest jet max sag south into the area
which should allow for heating ahead with a weak cool front
trailing Monday night. This cool front could spark a few
thunderstorms Monday night with isolated severe storms possible. The
EC and Canadian are slower with this front than the GFS, so will
need to watch trends and for now low confidence on any storms.

West northwest flow aloft remains in place Tuesday through Thursday
with periodic weak waves expected to move through. This should keep
shower and thunderstorm chances in place during this time with near
to below normal temperatures.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1251 AM CDT Fri Aug 14 2026

MVFR stratus has begun to develop south of US Highway 18 and
will continue to spread north through the early morning hours
and gradually lower to IFR and possibly LIFR in a some spots.
Patchy fog also remains possible mainly over the higher
elevations of southwest Minnesota and adjacent east-central
South Dakota through about 13z. Scattered showers and
thunderstorms will begin to move towards the Highway 20 corridor
early this morning and continue lifting north and weakening
through the daytime morning hours with northward extent.

Low stratus looks to linger through much of the daytime hours,
if not the whole day especially south of Highway 14. At the
same time, additional showers will develop through the afternoon
hours, along with a couple of thunderstorms if skies can clear.
Due to that uncertainty a PROB30 group for -TSRA this afternoon
for KSUX seems sufficient at this time. Any areas of stratus
that erode or lift through the day today will likely see it
expand again into Friday night.

Winds will be around 8-12 kts through the period, turning more
to the southeast throughout the day today. Winds then become
light and variable heading into Friday night.

&&

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

&&

$$

UPDATE...Samet
DISCUSSION...08
AVIATION...Samet