403
FXUS63 KFSD 231729
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1229 PM CDT Fri Oct 23 2026

.KEY MESSAGES...

- HIGH FIRE DANGER TODAY: Strong wind gusts of 30 to 45 mph
  combined with warm temperatures will create high fire danger.
  Agricultural harvest activities will have the greatest risks
  into the evening.

- COOLER WITH SCATTERED WEEKEND RAIN: A slow-moving front will
  bring increased clouds and occasional rain this weekend.
  Temperatures will be notably cooler (40s/50s) by Sunday.

- SIGNIFICANT RAINFALL LIKELY MONDAY-TUESDAY: A large multi-day
  system will bring widespread rain to start the new work week.
  Confidence in amounts over 1" through Tuesday morning remain
  high.

- ACTIVE WEATHER CONTINUES: A second fast moving system may
  bring rain chances back by Tuesday Night and Wednesday, with
  temperatures near seasonal normals.

&&

.DISCUSSION...
Issued at 1218 PM CDT Fri Oct 23 2026

THIS AFTERNOON: Winds continue to increase early this afternoon with
observed gusts between 30 and 45 mph.  Temperatures continue to warm
into the 70s, and potential for some highs in the 80s remain
possible along and west of the James River valley.  However, a
persistent mid-upr cloud deck may limit the climb this afternoon.
Out in western South Dakota, we`re beginning to see the first signs
of a frontal boundary forming that will gradually move eastward
overnight. The fire danger remains very high this afternoon,
especially for agricultural areas, please see separate discussion.

TONIGHT: An elongated upper trough stretching across the Rockies and
into southern California will begin to stretch and split in two
overnight.  Northern energy tracking eastward across southern Canada
will be strong enough to nudge the aforementioned surface boundary
into the I-29 corridor by mid-mornign Saturday.  Ahead of this
boundary, convergence on a 40 knot LLJ and the arrival of a mid-lvl
vorticity maxima should be enough to allow isolated to scattered
showers to develop and and ahead of this boundary.  MUCAPE may be as
high as 300 J/KG after 3am, so have increased PotThunder to at least
suggest isolated lightning strikes into mid-morning.

SATURDAY-SUNDAY: While northern stream energy moves eastward across
Canada, a large upper trough will remain over the Four Corners
region through the weekend. Overhead and closer to home, the
aforementioned surface boundary will linger across the Tri-State
area this weekend.  This front, stacked on top by a low-lvl frontal
zone, as well as somewhat persistent divergence from the right
entrance region of an upper jet, will keep scattered rain chances
and quite a bit of cloud cover through the area during the weekend.
Now the degree of rain coverage is still up in the air, given
somewhat diffuse and transient lift at times, but also some sub
cloud dry air that could linger. So will continue to advertise
a narrow stripe of low to mid-range PoPs that will fluctuate
north and south with the movement of the low-lvl baroclinic
zone.

Temperatures will be quite tricky on Saturday as the front bisecting
the CWA could lead to a large temperature discrepancy from
Huron to Storm Lake. 12Z guidance has trended downwards with
highs slightly, so blended in short term guidance to account for
trends the NBM may not have caught onto yet. There seems to be
much more consistency in guidance that cooler air may sink
further south behind the front for Sunday. With a persistent and
cool northeast surface flow in the CWA, highs may struggle to
break the 50s in portions of the CWA with the warmest highs near
Highway 20.

MONDAY-TUESDAY:  Slight discrepancies in medium range guidance on
Thursday have resolved somewhat this morning.  The large upper
trough in the Four Corner begins to eject northeast late Sunday
into Monday, and will begin to enhanced warm advection
northward and increase the intensity of the low-lvl frontal zone
through the CWA by Monday morning. We`ll have to watch for any
potential instability arrival, but fairly widespread moderate
rain may begin to form Monday morning and gradually retreat
northward as the upper trough enters the Plains.

Latest GFS guidance has shifted the track of the upper low slightly
further northwest from the Nebraska Panhandle into central South
Dakota by Monday night, closely resembling the latest ECMWF runs. AI
based models are also very similar in their track of this upper wave
(perhaps a bit further south than deterministic runs), suggesting
widespread rain will continue into Tuesday morning as the synoptic
trough passes.

All-in-all, this multi-day rain event is expected to bring rain
to nearly the entire region, and in some cases, meaningful
rainfall totals. The latest probabilities from the ECE/GEFS for
>0.50" are all near 100% by Tuesday morning, with 1.0"
probabilities >80%, and probabilities for 2-3" of rain around
30%. The location may change, but the area with the greatest
potential for the highest totals may fall between I-90 and the
Missouri River west of I-29.

Monday`s high temperatures will be highly depending on the track of
the upper low and associated surface cyclogenesis and low track.
Areas stuck under moderate rain may be in the 40s, with areas where
rain lifts north could rise into the 50s.

WEDNESDAY-THURSDAY: It appears a second system may race through the
Northern US on the heels of Monday/Tuesday upper trough by Tuesday
night and Wednesday.  We`ll see how quickly moisture can work it`s
way back northward, but this second system also poses a reasonable
risk for rainfall in the middle of the week along with a slight
upwards bump in temperatures towards normal.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1155 AM CDT Fri Oct 23 2026

VFR conditions with strong gusty southeast winds will continue
through the afternoon and evening hours. Eventually, we`ll see a
lower cloud deck near 10K ft AGL begin to develop after
midnight. Scattered showers and isolated thunderstorms may
develop into mid-morning Saturday, but in most cases VFR
conditions can be expected.

A frontal boundary slides from west to east Saturday
morning, reaching I-29 by mid-late morning and turning winds
more to the west northwest.

&&

.FIRE WEATHER...
Issued at 1220 PM CDT FRI Oct 23 2026

Strong southeast wind gusts between 30 and 45 mph will continue
this afternoon. Temperatures are a bit slower to rise today in
response to cloud cover overhead. However highs still well into
the 70s will be likely, with RH values dropping between 35 and
45% by peak heating this afternoon. Very high GFDI conditions
will continue into early evening. While grassland moisture
levels and RH remain high enough to prevent widespread red flag
warnings this afternoon, AG related fire danger will be near
critical into early evening. Harvest activities may want to
postpone until winds subside and local partners need to remain
vigilant into the evening.

A front moves from west to east early Saturday turning winds
west northwesterly and bringing increased rain chances through
the weekend. A widespread wetting rain is likely early in the
work week.

&&

.CLIMATE...
Issued at 1218 PM CDT Fri Oct 23 2026

A very warm day will still bring the potential for record high
minimum temperatures on Friday. Sioux City and Sioux Falls have
already dropped lower than their record for the date, however Huron
dropped to 62, so potential for tying or breaking this record
remains possible.

October 23:
KFSD: 60/1963
KSUX: 65/1899
KHON: 52/1963

&&

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

&&

$$

DISCUSSION...Dux
AVIATION...Dux
FIRE WEATHER...Dux
CLIMATE...Dux