756
FXUS63 KFSD 251121
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
621 AM CDT Sun Oct 25 2026

.KEY MESSAGES...

- Rain will continue off an on today into Monday night. The
  ensemble output, backed by the latest individual models
  indicates a 75-100% chance for 1" or more of rainfall from
  about I-29 west with about a 30-60% chance for more than
  2" from south central SD into the James Valley.

- An active pattern aloft will lead to additional rain chances
  from Tuesday night into Wednesday.

&&

.UPDATE...
Issued at 238 AM CDT Sun Oct 25 2026

Late tonight through early this morning the area will mostly be
between two waves, the weaker one exiting to the east and the
somewhat stronger wave moving in from the southwest. As this wave
lifts north today, the main focus will be on warm/moist advection
and a general lack of instability. This lack of instability
suggests that areas that lose saturation in the dgz will struggle to
produce precipitation. A quick walk through the model soundings
indicates that northwest IA will likely see the best chance to
remain dry for the bulk of the day while areas near and west of
highway 81 see the highest probability to remain saturated through
the day with off an on rainfall.

A well agreed upon increase in warm advection in the 850-750mb layer
occurs tonight, then gradually lifts north on Monday. Rainfall
should be more widespread on Monday with the stronger forcing near
and west of I-29. Northwest IA still looks to struggle a bit with
saturation in the dgz, but this time it appears there may be some
weak instability based around 850-900mb that may drive some showery
activity.

Monday night will see the bulk of the strong forcing lift northeast,
bringing a loss of saturation aloft, but some remaining in the lower
levels, hinting that some drizzle could linger into the overnight
hours. Some very weak instability could allow for isolated to
scattered showers on Tuesday, but amounts will be pretty light.

As for rainfall, the higher amounts still look to be focused west of
I-29. Some of the higher res data does shift the higher amounts
closer to highway 81, but the bulk of the models and ensemble output
continue to hint at the higher amount, 1-2.5", near and west of the
James River, north towards De Smet and Brookings.

&&

.DISCUSSION...
Issued at 200 PM CDT Sat Oct 24 2026

Currents & Tonight: Another dreary day continues! Taking a look
across the area, a brief break continues this afternoon as drier and
cooler air filters in behind a cold front. This along with breezy
northwesterly surface winds with gust between 25-35 mph has led to
quite the chilly feel this afternoon with highs sitting in the upper
40s to mid 50s west of I-29 and the 60s to low 70s east of I-29.
Expect temperature to continue their gradual decline from here.
Otherwise, the intermittent showers resume from late afternoon
onwards as southwest flow aloft helps additional pieces of energy
lift through areas mainly west of I-29 through Sunday morning with
mainly light accumulations. Lastly, given the increased cloud cover
overnight thinking temperatures won`t decrease as fast nor as far as
the NBM thinks (mid 30s to low 40s). With this in mind, decided
blend in some CONSshort into our MinTs slightly nudge up overnight
temperatures into the low to upper 40s

Sunday-Monday: Looking into Sunday, another wet and dreary day is
ahead as a subtle 850mb front stalls across our area roughly along a
Wagner to Sioux Falls to Windom, MN line. With broad southwesterly
flow firmly in place aloft, additional pieces of lift (dPVA) will
stream into the warm air advective (WAA) regime along and northwest
of this near-surface feature spurring intermittent showers
throughout the day within the left exit region of the coupled jet.
While mostly light accumulation are expected during this period,
should see an uptick in coverage from late Sunday evening into
Monday as additional lift arrives and WAA strengthen ahead of the
inverted trough axis. Looking aloft, most guidance has the base of
the mid-level trough gradually lifting into the Nebraska Pan handle
by Monday morning then central and eastern SD by Monday afternoon/evening.
While there some questions remains on where the heaviest accumulations
set up, its worth nothing that NBM QPF has taken a noticeable
northwest shift towards the better dynamics which are west of
I-29.

As such, still thinking most areas receive accumulating rainfall
through Monday. However, currently thinking the axis of 1+ inches
sets up somewhere west of a Yankton to Sioux Falls to Slayton, MN
line with the heaviest accumulations west of Highway 281. Everywhere
east of this line could be affected by a bit more dry air leading to
accumulations of a 0.50" of an inch or less. While not a drought
buster, this system will provide beneficial rainfall for parts of
the area over a 24-36 hour period. With this in mind, the flood
concerns are minimal though some ponding will be possible in some
urban and low lying areas. Lastly, expect the cooler conditions to
persist for both days given the increasing rain chances with daily
highs sitting in the mid 40s to mid 50s north of I-90 and low 50s to
low 60s south of I-90.

Tuesday Onwards: Heading into the extended period, quieter
conditions will temporarily return for the first half of Tuesday.
However, additional showers could develop by Tuesday afternoon along
and east of I-29 as a cold front swings through. From here, the
quieter conditions should persist through at least Friday as
solutions in long-range guidance begins to diverge. Lastly, expect
daily highs to remain mainly in the 60s to low 70s with the warmest
conditions across northwestern IA.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 619 AM CDT Sun Oct 25 2026

While much of northwest IA will remain mostly dry after a few
hit and miss showers early this morning, rain will gradually
become more persistent through the day west of I-29. By tonight
this steady rain will shift farther east to I-29 and into parts
of northwest IA. MVFR conditions are likely within the rain,
decreasing to IFR later tonight.

&&

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

&&

$$

UPDATE...08
DISCUSSION...05
AVIATION...08