603
FXUS63 KFSD 250147
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
847 PM CDT Thu Sep 24 2026

.KEY MESSAGES...

- Scattered showers and areas of drizzle remain possible tonight
  through tomorrow. Rain won`t be as widespread Friday as what
  we saw today, but be prepared for occasional pockets of light
  rain.

- The active weather pattern continues bringing a high chance
  (>90%+) of additional rain late Friday into Saturday and
  again later Monday into Tuesday (>50%).

- Daytime temperatures remain below normal, but should climb
  closer to normal Saturday into Monday.

&&

.UPDATE...
Issued at 843 PM CDT Thu Sep 24 2026

TONIGHT: We`re continuing to see very light drizzle to sprinkles
develop in the Tri-State area as weak 925:850 mb warm advection
persists. Widespread stratus will continue to settle downward
through the night and could result in some visibilities below 4
miles at times. Increased southeasterly winds may prevent any
significant drops at this point.

FRIDAY-FRIDAY NIGHT: Expect a very cloudy, dreary day on Friday as
we`ll remain under a widespread stratus deck.  Latest guidance
continues to hint at areas of drizzle or light rain showers during
the morning with some patchy fog as well. Better focus for light to
moderate rain is expected near Highway 20 under both deeper moisture
and a mid-lvl area of vorticity.  This strung out area of vorticity
along the MO river will begin to advance northward by the afternoon
bringing an increasing risk for showers by late afternoon and
through the evening.  While evening activity may remain more
scattered, the development of the LLJ and more expansive dPVA
overnight should bring a much more concentrated and focused rain
chance into Saturday morning.  No major changes expected to the
forecast into Saturday morning, but PoPs will certainly be near
100%. Total QPF through Saturday evening may average between 0.25-
1.0", with some focus for the higher amounts in NW Iowa.

&&

.DISCUSSION...
Issued at 242 PM CDT Thu Sep 24 2026

An area of steady light to locally moderate rainfall
extends from around a Slayton to Yankton line and points east.
This area of rain will gradually push east through the remainder
of the afternoon and start to fall apart this evening over
northwest Iowa. However, patchy drizzle will be possible after
this rain departs especially along and east of I-29. A bit drier
in the low-levels over parts of northwest Iowa tonight, so it
may take a bit longer for drizzle to develop there. Farther
west, especially into south-central South Dakota, we will see
some breaks in the clouds which will allow temperatures to warm
into the middle 70s. Some instability (around 500-750 J/kg) will
be present along and ahead of a weak front over south-central
South Dakota where this heating is occurring, but plenty of dry
mid-level air should prevent scattered showers and storms from
developing in these locations. In the off chance (<10%) we get a
storm, severe weather is not expected as weak effective shear
looks to be place.

Heading into tonight, a few showers will continue to be possible
mainly along the Highway 20 corridor. Low stratus looks to spread
back west through the night, but before it spreads back into south-
central South Dakota, patchy fog can`t be ruled out there. Drizzle
will begin to become more likely heading into early tomorrow morning
as cloud ceilings continue to fall, so keep the rain gear handy for
your Friday morning commute. Scattered light showers will develop
throughout the day, with chances gradually lifting northward through
the afternoon due to strengthening warm air advection at 850 mb.
These will be more of the hit or miss variety unlike what we
saw today, so keep that umbrella nearby but rain totals will
only be a few hundredths to a tenth of an inch during the day on
Friday, except for locally higher amounts along the Highway 20
corridor Friday morning. Lowered the high temperatures a bit
from the NBM for Friday given the cloud cover and drizzle, with
highs mostly in the lower 60s. If some peaks of sun can be
realized, a few middle to upper 60s for highs will be possible.

Rain chances will increase Friday night into Saturday morning as the
main upper wave pivots through the area. The highest rainfall totals
during this time frame will generally be over northwest Iowa and
adjacent areas of southeast South Dakota and far northeast Nebraska,
where around a half an inch to an inch of rain can be expected. A
few pockets of 1-1.5" of rain (15-25% chance) can`t be ruled out
mainly along and southeast of a Spencer to Sioux City line. This
rain should be spread out long enough where flash flooding concerns
will be low where these highest amounts occur, but still be prepared
for wet roads if traveling especially early Saturday morning.

Showers and very isolated storms will gradually push east through
the afternoon, though once again some patchy drizzle will remain
possible after any of the rain showers end at least through the
early evening Saturday. Drizzle details will be refined as we
get closer to the Saturday afternoon. Though some very patchy
drizzle will be possible into Sunday morning, should mostly see
dry weather for the day. This should allow for some of the
warmest temperatures that we`ve see over the past few days, with
highs in the upper 60s to middle 70s. Ultimately, these
temperatures will be dependent on how quickly we can scatter out
any morning clouds, so expect changes to the forecasted
temperatures as we approach Sunday.

Rain chances do look to return once again on Monday, but especially
Monday night into Tuesday. This will be as the West Coast longwave
trough finally swings into the area. Will have to watch for any
heavy rain once again with this activity, especially on top of the
rainfall we`ve seen the past week. LREF probabilities show around a
30-40% chance of at least an inch of rainfall Monday night through
Tuesday night, focused over northwestern Iowa. Trends will continue
to be monitored as we get closer to next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 603 PM CDT Thu Sep 24 2026

Widespread stratus will begin to spread back westward after
sunset, with gradual lowering back to IFR and even LIFR levels
at times into Friday morning. Just enough lift in the lowest
levels to lead to occasional periods of drizzle or sprinkles
deep into Friday morning. Visibilities may fall below 4 miles at
times, though I wouldn`t be surprised to see visibility fall
below 2 miles in higher elevation areas.

Minimal improvement is expected Friday, with occasional drizzle
or showers. Ceilings may gradually mix up to MVFR levels in the
afternoon once again. Winds remain south to southeasterly.

&&

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

&&

$$

UPDATE...Dux
DISCUSSION...Samet
AVIATION...Dux