275
FXUS63 KFSD 212307
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
507 PM CST Fri Nov 21 2025

.KEY MESSAGES...

- Warm conditions are expected this weekend, with highs mainly
  in the 50s. Some spots could reach the low-60s each afternoon,
  especially along the Missouri River Valley.

- There is a moderate (50-80%) chance of rain Monday into Monday
  night. There is a low-to-moderate (20-40%) chance of rainfall
  amounts greater than a quarter of an inch east of I-29 through
  Monday night.

- Colder temperatures are set to move in next week, with single
  digit wind chills possible by Wednesday morning especially
  north of I-90. Thanksgiving is looking chilly as well, with
  more single digit wind chills possible Thanksgiving morning.

&&

.DISCUSSION...
Issued at 300 PM CST Fri Nov 21 2025

It`s another seasonal day out there with highs mainly in the 40s
across the area! A surface high pressure system is drifting across
the region, helping to keep winds light this afternoon. As this high
shifts east of the area tonight, winds will turn more southerly and
allow for a milder night. Lows tonight will stay mainly in the 30s.
Some patchy fog will be possible tonight, but winds will be slightly
elevated compared to last night and so widespread issues are not
expected. A weak frontal boundary moves into the area heading into
tomorrow, but not expecting precipitation with it. Instead, winds
will just turn more westerly to northwesterly with time through the
day tomorrow. With mostly sunny skies in the forecast tomorrow,
should be a pleasantly mild day with highs in the 50s. A couple of
spots along the Missouri River Valley could potentially sneak up to
60 degrees.

Sunday will be our last both mild and quiet weather day for quite
some time as a more active pattern starts to set-up over the region.
But first, Sunday will feature mainly sunny skies with highs well
into the 50s, with some 60s possible especially in south-central
South Dakota. Currently thinking Sunday will be the warmer weekend
day as guidance shows some cold air advection at 850 mb on Saturday,
and that won`t be an issue for Sunday. Also, southerly winds will
return to the area on Sunday. The only thing that could limit
warming on Sunday would be if clouds from our next storm system
arrive earlier than expected along the Missouri River Valley. But
right now, that doesn`t look to occur until Sunday night. Speaking
of our next storm system, let`s discuss what`s going on with
that in the next couple of paragraphs

On Sunday, an upper-level low will begin to eject out of the Desert
Southwest into southern Colorado. While this is happening, a trough
will start digging into the Pacific Northwest. As the upper-level
low continues lifting northeastward into the central Plains on
Monday, it will be absorbed into the upper-level flow of the Pacific
Northwest trough that will be barreling eastward into the northern
Plains. Before the upper-level low gets absorbed, a surface low
looks to develop near the Colorado and Kansas border Sunday night
and lift northeastwards through the day on Monday. This will result
in rain moving into the Missouri River Valley starting Sunday night,
with rain chances lifting northeastwards into the day on Monday. The
greatest chance of rain on Monday will be along and east of I-29,
where there is currently a 50-80% chance of rain. Ensembles show a
roughly a 50-75% chance of over a tenth of an inch of rain in these
areas Monday into Monday night, falling off to less than a 40%
chance of over a quarter of an inch of rain.

After the upper-low gets absorbed into the trough that came from the
Pacific Northwest, guidance diverges and uncertainty in the forecast
grows. The GFS has the trough close off into a new upper-level low
and swings it into South Dakota on Tuesday, while the EC and
Canadian keep it more of an open wave and not closing it off into an
upper-low until it gets into southern Ontario Tuesday night. The
Canadian and EC solution would mean precipitation chances would
leave our area faster on Tuesday morning as the associated surface
low also moves into Canada. Meanwhile, if the GFS solution were to
come to fruition, then a new surface low would develop over the
northern Plains and keep precipitation chances in the forecast for
Tuesday and even into Wednesday as well. With much colder
temperatures in place, that would mean better snow chances. However,
ensemble probabilities for a least a tenth of an inch of snow are
only 25-45% for the Tuesday to Wednesday time frame, so a lot of
uncertainty remains and trends will be monitored. Either way,
much colder temperatures are set to move into the area
especially by Tuesday night as wind chills may drop into the
single digits especially along and north of I-90. On Wednesday,
wind chills will struggle to get out of the teens and then
Wednesday night into Thanksgiving morning, we`ll see more wind
chills likely in the single digits. Thanksgiving day itself is
looking dry as of now, but chilly with highs only in the
upper-20s to mid-30s.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 505 PM CST Fri Nov 21 2025

VFR conditions with light winds expected through the overnight
hours as well as through Saturday. We`ll continue to see a
scattered mid-lvl and broken to overcast upper level cloud field
through the night. Winds turn southerly after midnight and will
remain southerly through Saturday morning.

By Saturday afternoon, a weak frontal boundary moves through the
region, pushing surface winds towards the west and northwest,
with occasional gusts to 20 knots at times.


&&

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

&&

$$

DISCUSSION...Samet
AVIATION...Dux