467
FXUS63 KFSD 270850
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
350 AM CDT Tue Oct 27 2026

.KEY MESSAGES...

- Patchy fog will likely continue through mid morning especially
  along the higher elevations of southwest Minnesota and
  adjacent areas of eastern South Dakota. There is a medium
  (40-60%) chance of visibilities less than 1 mile in these
  areas.

- An active pattern leads to additional rain chances on Wednesday
  and over the weekend. Monitor your local forecast if you have
  any outdoor plans, especially Wednesday afternoon as isolated
  thunderstorms will be possible.

- Near to above normal temperatures return from Wednesday onward
  with highs in the 60s to lower 70s.

&&

.UPDATE...
Issued at 341 AM CDT Tue Oct 27 2026

The last of the showers are moving off to our north and east
early this morning, leaving patchy fog and drizzle in its wake.
Thus far, visibilities have largely remained above 2 miles in
fog and drizzle, but any fog may thicken up a bit heading
towards daybreak mainly over the higher elevations of the Coteau
des Prairies and nearby areas, with a 40-60% chance of
visibilities dropping below 1 mile there. Use extra caution on
the roads during your morning commute. Any fog should lift by 10
am. Look for low stratus to linger across much of the area
through the day today. With some very weak instability in place,
could see a few sprinkles or spits of drizzle in spots. However,
most of us will stay dry during the daytime hours today. Stratus
will likely be thin enough in spots for the sun to break through
at times during the afternoon, with the best chance of this
occurring over south-central South Dakota. With that, this is
also the area that will have the best chance of reaching the
lower 60s for highs this afternoon. Elsewhere, look for highs to
remain mostly in the 50s today.

Guidance is indicating another potential for fog late tonight and
into Wednesday morning, with the 27.00Z HREF showing a 40-70% chance
of visibilities less than a half a mile mainly focused north of
I-90. This will be dependent on if the previously mentioned
stratus can erode overnight and if winds can go light enough, so
there is still some lingering uncertainty. As of now, would say
a few patches of fog are likely Wednesday morning mainly north
of I-90, but how widespread and how dense any fog will be
remains a question.

A low pressure system will bring along a cold front through the
area on Wednesday, bringing our next chance of showers. With
temperatures warming well into the 60s to even some lower 70s,
guidance is indicating the potential for 500-1,000 J/kg of
SBCAPE developing mainly east of I-29 Wednesday afternoon. This
could result in a few thunderstorms to develop along with the
showers. Will have to watch this potential as there may be
enough overlap with shear and instability that a stronger storm
can`t be ruled out.

&&

.DISCUSSION...
Issued at 306 PM CDT Mon Oct 26 2026

Light, periodic rain showers will continue through the remainder of
this afternoon and into the overnight, gradually dissipating
from southwest to northeast. A period of light drizzle is
possible as moisture wraps around the low in the early morning
hours of Tuesday. There is potential for fog to develop
overnight along river valleys and low areas. There is
approximately a 20-30% probability that visibility may briefly
fall to 2 miles or less. All shower activity should be northeast
of the CWA by around sunrise, and fog should burn off shortly
after. Overnight lows will dip into the upper 30s to mid 40s.
Thick, low stratus clouds linger into early Tuesday afternoon
before being swept away by a second shortwave moving through
western North Dakota. Winds become southerly and increase in
response to the tightened SPG. Gusts of 20-30 mph are possible
along and west of the James River Valley, with gusts generally
less than 20 mph to the east. Shallow mixing will tap into
strong WAA in the 925-850 mb layer. At the surface we can expect
highs to warm nicely into the low 50s to low 60s. The warmest
temperatures are expected over central South Dakota and
northeastern Iowa.

Wednesday morning lows will be warm for late October, in the 40s to
low 50s. Average lows this time of year are in the lower 30s.
Another day of light to breezy southerly winds and strong WAA will
warm our afternoon highs in the 60s and 70s. Similar to the lows, we
are quite warm for this time of year when average highs are
generally in the mid 50s. Around mid-morning a broad upper wave and
weak surface low will take shape over central Canada. An associated
cold front will drape from there southwest through central South
Dakota into southeast Wyoming. Light rain is expected to develop
along the front, mainly west of the James River late in the morning.
As the wave and frontal system move southeast rain will move into
the I-29 corridor and into western Minnesota and Iowa. Rain is
expected to be spotty in nature with little accumulation. Only a few
hundredths to a tenth or two. Showers clear out to the east after
midnight. Behind the front winds become northwesterly and light.
This will allow for good radiational cooling and lows will drop into
the mid 30s over central South Dakota to the upper 40s east of I-29.

Thursday winds aloft will become zonal to south-southwest. At the
surface high pressure builds in from the northwest. Winds will turn
southeasterly as that high scoots off to the east, but remain light.
Dry and mostly sunny conditions with highs in the low to mid 60s.
The majority of the day Friday will be dry with highs in the 60s.
Friday late afternoon and into Saturday another shortwave system
moves through bringing additional chances for rain. While currently
rainfall looks to be spotty and light, this could impact outdoor
Halloween plans. A brief break on Sunday before a much more
pronounced upper trough brings wide spread chances for
accumulating rainfall to the area Monday into late Tuesday.
While uncertainty is very high at this juncture, long term
ensemble guidance indicates the potential for widespread 0.5 to
1 inch. Stay tuned as we monitor the trends with this system and
details emerge.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1038 PM CDT Mon Oct 26 2026

Rain continues to lift north through the overnight hours. Seeing
some patchy drizzle as well, which is leading to some locally
reduced visibility. Additionally, fog may develop overnight,
which could lead to other areas of reduced visibility. Thus far,
stratus is keeping ceilings for most of the area MVFR to IFR,
with more localized LIFR conditions west of I-29. Further east,
ceilings for northwestern IA remain lower VFR, but are expected
to drop overnight. Visibility is generally MVFR to IFR with rain
and drizzle, and IFR conditions may develop with fog.
Precipitation ends by early Tuesday morning, and any fog should
lift through mid morning.

Guidance continues to be low with improvements to ceilings
Tuesday, so maintained a more pessimistic forecast - especially
for KFSD and KSUX. Some locations may see VFR conditions toward
the end of the period, but think MVFR stratus linger through
much of tomorrow evening.

Winds through the period will vary in direction before becoming
southerly through the day Tuesday. Gusts west of the James River
around 20 to 25 knots expected in the afternoon and evening.
Winds become light once again Tuesday night, which could lead to
more fog development across the area.

&&

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

&&

$$

UPDATE...Samet
DISCUSSION...AJP
AVIATION...SG