820
FXUS63 KFSD 291140
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
640 AM CDT Thu Oct 29 2026

.KEY MESSAGES...

- Areas of fog have developed this morning, with some dense fog
  mainly near and along river valleys. Watch out for quickly
  changing visibilities on your morning commute. The last of the
  fog should lift between 10 and 11 am.

- Rain chances with some isolated thunderstorms return early
  Friday morning and continue through Saturday and again early
  next week.

&&

.UPDATE...
Issued at 402 AM CDT Thu Oct 29 2026

Patchy fog has developed once again early this morning, especially
in areas surrounding river valleys, with several spots
along/near rivers dropping to a half mile or less. Would want to
see any dense fog to spread out into areas away from rivers and
become a bit more widespread before issuing a dense fog
advisory, but trends will be monitored closely. Either way, be
prepared for some areas of fog on your morning commute! The fog
has also been quite shallow in places as well, so visibilities
may quickly change when going up and down hills. Any fog erodes
entirely by about 10 am or slightly afterwards.

Heading into the daytime hours, mid-level clouds associated
with a weak wave will move across the far western part of the
forecast area this morning and then scrape the Highway-14
corridor in the afternoon. Soundings show some shallow
instability within this cloud layer, but dry air below should
limit any of this precipitation from reaching the ground.
However, can`t rule out a few sprinkles in these areas (<20%
chance). Otherwise, more appreciable rain chances return to the
area on Friday but especially Friday night into Saturday.
Friday morning the focus for rain chances will be along the
Highway 20 corridor and into northwest Iowa as scattered showers
develop with increasing warm air advection. Showers then look
to expand in coverage and spread northward later Friday and
continuing into Saturday morning. Most of this activity will be
on the lighter side (<0.15" totals), though some higher amounts
look to be centered around the Highway 20 corridor into
northwest Iowa where chances of a quarter of an inch or more of
rain have gone up a bit (around a 40-60% chance).

&&

.DISCUSSION...
Issued at 131 PM CDT Wed Oct 28 2026

Over the next couple of hours, showers and storms are expected
to develop over parts of eastern South Dakota and western
Minnesota ahead of a cold front. Cannot entirely rule out the
possibility of strong to severe thunderstorms, although the best
environment will be to the northeast further into Minnesota.
Still, a Marginal Risk clips the northeastern-most part of the
forecast area, and hail is the main potential severe threat.
Strong storms that do develop in that area are expected to exit
the forecast area fairly quickly this afternoon. Further south,
expectations are that showers will remain fairly light, and just
a few hundredths of rain will fall.

Behind the cold frontal passage, a high pressure center will move
into the area overnight tonight. After an initial shift to the
northwest, winds will become light and variable overnight tonight as
the high pressure center moves overhead. There is some signal in
high-resolution guidance for some fog development once again tonight
due to the light winds and clear skies promoting strong radiative
cooling. The main area of concern for fog development is over
southeastern South Dakota, particularly the James River Valley.
Confidence in the areal coverage is still somewhat low at the
moment, but pockets of dense fog may reduce visibility below a mile
at times.

The next chances for rain come on Friday into Saturday. Rainfall
will move in from the south beginning Friday before expanding to
cover the entire forecast area Friday night into Saturday. Generally
light rain rates are expected, but perhaps a quarter of an inch or
more (20-40%) could fall over parts of northwestern Iowa,
northeastern Nebraska, and southeastern South Dakota.

Another low pressure system is set to move into the region early
next week, bringing renewed chances for rain into the region. Monday
through early Wednesday, chances are fairly high (50-70%, increasing
moving from north to south across the forecast area) to see an inch
of rainfall accumulation or more. However, there is still
significant uncertainty with this system in timing, location, and
amounts. 25th/75th spread is generally around two inches for that
same time period, so still a lot to resolve as the system comes into
focus over the next couple of days.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 637 AM CDT Thu Oct 29 2026

Areas of fog will continue to impact the area through about 15-
16Z, with some dense fog mainly confined to areas near and along
river valleys, especially the Missouri River Valley and southern
James River Valley. Fog has also been notably quite shallow and so
it has dissipated and reformed in a sometimes quickly repeating
cycle, and that trend looks to continue.

After fog clears, VFR conditions are expected for the rest of
today and this evening. Heading into tonight, lower MVFR cigs
will begin to creep into the Highway 20 corridor along with a
few showers. Winds will be fairly light through the period out
of the east-southeast.

&&

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

&&

$$

UPDATE...Samet
DISCUSSION...BC
AVIATION...Samet