089
FXUS63 KFSD 201247
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
647 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 645 AM CST Thu Nov 20 2025

An area of dense fog continues to advance southeast along the
leading edge of low stratus, with improvement from the northwest
as previously anticipated. Have adjusted the area covered by a
Dense Fog Advisory accordingly.

Issued at 438 AM CST Thu Nov 20 2025

Web cam imagery showing more expansive coverage to the dense fog
within the advancing low stratus across the Tri-State area as of
4 AM. Though improvement from northwest to southeast is still
expected over the next 3-4 hours, given potential impacts to the
morning commute, have issued a Dense Fog Advisory for southern
portions of the Highway 81, I-29 & Hwy 75 corridors through 9AM.
Will monitor surface obs and web cams closely and further adjust
the coverage of the advisory as needed.

&&

.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 /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 547 AM CST Thu Nov 20 2025

LIFR ceilings/visibility again blanket portions of the forecast
area at the start of this TAF period. An advancing front should
bring improving conditions through 15Z, however, MVFR ceilings
will remain prevalent into this afternoon.

Lower confidence in redevelopment of stratus and/or fog during
the latter half of the period as models show thinning of this
persistent low level moisture. Remained optimistic in showing
VFR conditions after sunset for now, though be aware that this
may change with later updates if confidence in redevelopment
increases.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Dense Fog Advisory until 9 AM CST this morning for SDZ067-070-
     071.
MN...Dense Fog Advisory until 9 AM CST this morning for MNZ081-089-
     090.
IA...Dense Fog Advisory until 9 AM CST this morning for IAZ001>003-
     012>014-020>022-031-032.
NE...Dense Fog Advisory until 9 AM CST this morning for NEZ013-014.

&&

$$

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