732
FXUS63 KFSD 201751
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1151 AM CST Thu Nov 20 2025

.KEY MESSAGES...

- Areas of fog may impact this morning`s commute, but general
  improvement is expected from northwest to southeast through
  mid-morning. Lingering clouds will limit high temperatures to
  the 40s for many areas today.

- 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.

- Low-moderate (20-40%) chances for light rain early next week
  (Monday-Tuesday). Some uncertainty in timing/location, but
  high confidence that rain will be the dominant precipitation
  type.

&&

.UPDATE...
Issued at 1144 AM CST Thu Nov 20 2025

The Dense Fog Advisory will be allowed to expire at the top of
the hour (12 PM CST) as conditions continue to improve.
Visibilities may still be locally down to around one mile for
next hour mainly over Buena Vista County and Ida County, IA.

&&

.DISCUSSION...
Issued at 331 AM CST Thu Nov 20 2025

Light winds and an area of clear skies ahead of a cool front
has led to areas of fog early this morning. While pockets of
dense fog have been observed, a relatively short-lived duration
of lowest visibility along with expected improving conditions
with the passage of the front preclude issuance of a Dense Fog
Advisory. Have issued a Special Weather Statement to highlight
the potential for changing visibility which could linger into
the morning commute for portions of northwest Iowa.

While the lowest stratus currently over the area may thin/clear,
a broad area of somewhat higher stratus is poised upstream and
expect this to sag southeast into the area today. As we have
seen the past couple of days, NBM temperature forecast has been
overly-optimistic in areas of more persistent clouds and have
again trended toward cooler end of guidance for highs today.

Moving into tonight and Friday, a surface ridge will provide
limited mixing. May see areas of fog and/or stratus linger into
the morning. However, models do generally show a thinning of
the low-level moisture, so modest optimism for more sunshine and
will stick closer to NBM high temperatures in the mid 40s-near
50.

The weekend ahead will feature warmer temperatures building
into the northern Plains ahead of a southern stream trough that
may bring chances of rain to parts of the northern Plains early
next week. Saturday should be the warmer day of the weekend and
the better chance to see highs in the 60s for some areas south
of I-90, though both Saturday and Sunday will see temperatures
10-20F above normal and dry conditions. If you have remaining
outdoor yard work or holiday decorating, this weekend would be
a great time to finish up those tasks as a sharp cool-down is
coming by the middle of next week.

The aforementioned southern stream trough has trended northward
in its trek through the Plains early next week compared to this
time yesterday, bringing low-moderate (20-40%) chances for rain
to parts of the forecast area sometime in the Monday-Tuesday
timeframe. While there is still low confidence in the exact
track and timing of this system, confidence is currently much
higher that temperatures will remain warm enough for rain to be
the dominant precipitation type.

Big changes on the way by the end of this forecast period with
regard to temperatures, as our extended stretch of mild weather
comes to an abrupt end. Timing of a stronger northern stream
wave and associated arctic cold front varies more in the latest
model solutions. Some now bring the front through as early as
Tuesday morning, while others hold off until later Tuesday into
Tuesday night. This is leading to low confidence in highs for
Tuesday, with a 10th-90th percentile spread in the NBM of over
15F. In either case, temperatures take a sharp downward turn
by Wednesday with even the warmest guidance indicating highs
in the lower-mid 30s. Increased northwest winds will accompany
the arctic blast, so those with holiday travel plans should be
prepared for the cold and wind.

While confidence is high that below normal temperatures will
dominate the latter half of the holiday week (highs only in the
20s and 30s and nighttime lows in the teens), there is still
uncertainty in whether wintry precipitation could further
impact holiday travel.

&&

.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...Dense Fog Advisory until noon CST today for IAZ014-021-022-032.
NE...None.

&&

$$

UPDATE...Samet
DISCUSSION...JH
AVIATION...Samet