633
FXUS63 KFSD 140844
AFDFSD

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

.KEY MESSAGES...

- Scattered showers and thunderstorms continue this morning over
  northeastern Nebraska into northwestern Iowa. Shower/storm
  chances expand north today/tonight, but better chances remain
  across northeastern Nebraska and northwestern Iowa. The main
  threat is locally heavy rain.

- Patchy fog continues mainly over the higher elevations of
  southwest Minnesota and adjacent areas of eastern South Dakota
  this morning. Moderate (40-55%) chances of locally dense fog
  by daybreak.

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

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

.UPDATE...
Issued at 343 AM CDT Fri Aug 14 2026

Patchy fog lingers through mid morning near the Buffalo Ridge.
Probability of visibility below 1/4 mile has increased for this area
as well, so be prepared for changing conditions.

Showers/storms continue to bloom this morning near and south of US
Highway 20, where mesoanalysis indicates some WAA and increasing
vorticity with an elevated boundary, somewhere between 850mb and
700mb. CAMs remain too slow with the development of this activity
based on trends over the last hour. Development remains focused just
south of our area, but expect this to lift north through the morning
hours. Also some isolated showers north of I-90. Scattered showers
and storms continue today into tonight with the mid level wave and
as the surface low lifts north out of KS.

Severe weather is not expected with soundings showing a deep warm
layer, relatively weak shear, and tall/skinny CAPE. Main threat
remains locally heavy rain through mid to late morning; activity so
far seems fairly progressive, so concern would be training storms
over areas near US Hwy 20 that received heavier rainfall yesterday.
Locally heavy rain remains the main threat later today as well,
especially over those aforementioned areas. Severe weather remains
unlikely later today into tonight with continued long/skinny CAPE
profiles and a deep warm layer, precluding hail threat and limiting
wind potential.

May see a break in the more widespread precipitation overnight
Friday into Saturday between waves. Confidence in precip
timing/coverage remains low for this time. Fog and stratus are
expected to develop once again.

&&

.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...SG
DISCUSSION...08
AVIATION...Samet