437
FXUS63 KFSD 202102
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
302 PM CST Thu Nov 20 2025

.KEY MESSAGES...

- Additional fog may develop tonight, especially in south-
  central South Dakota and parts of northwest Iowa. Visibilities
  could drop below 2 miles in fog.

- A warm-up is expected for the weekend, with highs in the 50s
  to possibly lower 60s. This would be a good time to wrap up
  outdoor winter or holiday preparations.

- Much colder air arrives for the Thanksgiving travel period,
  with the chance for below average temperatures increasing by
  Tuesday night.

- Moderate (30-60%) chances for rain early next week (Monday-Tuesday).
  Some uncertainty in timing/location, but higher confidence
  that rain will be the dominant precipitation type.

&&

.DISCUSSION...
Issued at 256 PM CST Thu Nov 20 2025

Fog has lifted and skies are attempting to clear for
most of the area before the sun sets this evening. Highs have
climbed into the 40s this afternoon, making for a seasonal
November day out there! Areas of stratus continue to drift
southward, with some areas potentially seeing some redevelopment
of these low clouds overnight. However, the general trend will
be for these clouds to continue drifting southward through this
evening, before stalling out tonight south of I-90. Areas with
less cloud cover overnight will be primed for quick radiational
cooling as winds turn mainly calm while a high pressure system
drifts over the region. This will lead to a chilly night, with
lows down into the upper-20s especially along and north of I-90,
with some mid-20s possible along the Highway-14 corridor.
Patchy fog looks to develop tonight, especially in south-central
South Dakota and parts of northwest Iowa. With temperatures
marginally freezing in these locations, impact-causing freezing
fog is not expected. However, if fog is able to develop further
north towards the Highway-14 corridor where temperatures will be
colder, then perhaps you could see some light freezing on
elevated surfaces such as trees and bridges/overpasses. Trends
will be monitored overnight.

A quiet day is expected tomorrow as an upper-wave passes to our
south, though the wave will help keep cloud cover in place
especially along the Highway-20 corridor through the day. Southerly
flow returns at the surface as the aforementioned high pressure
system moves off to our east, but still, a seasonal day is in
store once again for Friday, with highs mainly in the 40s. However,
a few spots in central South Dakota could sneak into the
low-50s. Saturday will be a warmer day as there will be ample
sunshine ahead of a weak frontal boundary moving eastward across
the area. Highs will be into the 50s across the area, with some
60s looking increasingly likely over parts of the Missouri
River Valley. The aforementioned frontal boundary will turn
winds more west/northwesterly by late Saturday, but won`t have
rain nor much cooler air behind it. In fact, Sunday will be
another unseasonably warm day with a similar temperature profile
as Saturday (though perhaps a few less 60s along the Missouri
River Valley).

While this enjoyable weekend weather is taking shape, our next storm
system will also be taking shape with an upper-level low set to
eject from the Desert Southwest into the central Plains towards the
end of the weekend. This system approaches our area Sunday night,
bringing some rain chances with it late Sunday night into the day on
Monday. At the same time, another trough and upper-low will move
through the northern Rockies into the northern Plains, supporting
the development of a surface low to our north. Guidance varies with
the placement of this low, with the GFS and Canadian models showing
the low over Ontario, while the EC shows it over the northern Great
Lakes. The solution supported by the EC would mean some wrap-around
moisture gets into our area north of I-90, which could be in the
form of light snow depending on how quickly temperatures cool.
But still, rain is currently looking to be the dominant
precipitation type with this system. Speaking of temperatures,
much cooler air is set to move in for the middle of next week
leading up to Thanksgiving. Currently, we`re looking to see
highs in the 40s on Tuesday and highs in the 30s on Wednesday,
though some machine learning guidance indicates that
temperatures may drop faster than what the NBM shows right now,
with highs potentially in the 30s as early as Tuesday. Did not
stray away from the NBM temperatures at this time due to this
system being a few days out, but be sure to keep up to date with
the latest forecast. Either way, colder air arrives for the
Thanksgiving holiday, with lows in the 20s by Wednesday and lows
in the teens by Thanksgiving day and on Friday.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1144 AM CST Thu Nov 20 2025

IFR to MVFR stratus continues to impact the area this afternoon,
with two distinct decks over us. The southern deck is located south
of I-90, and the leading edge of the second deck is moving across
the Highway-14 corridor and drifting southwards. In between, there
is a mix of clear skies and newly developing low clouds near the I-
29 corridor from KMDS to KFSD. All this will lead to mainly MVFR
conditions across the area through the rest of the afternoon into
the evening, with occasional breaks in the clouds. All these low
clouds will slowly drift southward through the period, clearing KHON
just before sunset, clearing KFSD after midnight, and sticking
around KSUX through the period (though there looks to be a break in
between the two stratus decks for a few hours this evening at KSUX).

Some fog may develop where skies clear out tonight, but confidence
was not high enough to include in the TAFs at this time. Guidance
currently indicates the best chance of fog develops where skies
clear along the Missouri River Valley in south-central South Dakota.
Winds will be mainly out of the northwest this afternoon around 5-10
kts, turning light and variable to calm overnight.

&&

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

&&

$$

DISCUSSION...Samet
AVIATION...Samet