687
FXUS63 KFSD 221914
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
214 PM CDT Tue Sep 22 2026

.KEY MESSAGES...

- Mostly cloudy conditions for the remainder of today with some
  peaks of sun possible. Overnight scattered light sprinkles to
  showers are possible. Breezy conditions expected to develop
  overnight.

- Wednesday late afternoon and evening a more organized line of
  showers and thunderstorms are expected to move through the
  region. While severe weather is not anticipated, storms could
  produce brief periods of heavy rain. Rain pushes east of the
  region by Thursday afternoon.

- The active weather pattern continues bringing a high chance
  (>60%) of additional rain Friday night into Saturday.

- Temperatures will rebound to near-normal highs in the upper
  60s to lower 70s starting Thursday and lasting through the
  weekend.

&&

.DISCUSSION...
Issued at 203 PM CDT Tue Sep 22 2026

Drizzle and sprinkles are expected to end this afternoon as a
weak ridge continues to build in over the northern Plains.
Soundings indicate some thinning of the stratus deck in the mid
afternoon, which may allow a few peaks of sunshine. But for the
most part cloudy conditions will prevail through the weekend.
Winds this afternoon will be slightly breezy out of the east-
southeast, with gusts of 15 mph up to 20 mph over central South
Dakota. Highs will be 10-15 degrees cooler than average for this
time of year, in the upper 50s to low 60s. (Average is mid
70s.)

Looking aloft and to the west, we see an upper trough lifting
northeast out of the central Rockies through the day. As it
ejects out onto the northern Plains this afternoon a lee trough
will form from Montana down to Colorado. As this wave system
pushes slowly east the SPG will tighten, strengthening the LLJ.
Winds from the surface through 850 mb will be south-
southeasterly, advecting in warmer and moist air. CAMs have
begun to key on some light showers developing along a band of
vorticity advection over central South Dakota in the late
afternoon today. These will be light and scattered in nature,
driven by both the increasing WAA and LLJ. These will slowly
advect east through the overnight and into the day Wednesday.
Meanwhile, breezy winds will expand slowly east through the
overnight and much of the day Wednesday. Gusts of 20-30 mph are
expected along and west of I-29, with gusts up to 40 mph
possible over central South Dakota Wednesday afternoon. Areas
east of I-29 will see lighter gusts between 15-20 mph. Highs for
Wednesday will be slightly warmer thanks to the enhanced WAA,
in the 60s.

By Wednesday afternoon the previously mentioned wave system will be
drifting over central North and South Dakota. Increasing
positive vorticity advection from both the northern wave and a
secondary band moving in from the southwest ahead of a
subtropical wave will result in stronger forcing for ascent.
Coupled with continued WAA and strong LLJ a more organized line
of storms will form with the potential for pockets of moderate
to heavy rain. We do not anticipate severe weather at this time,
however localized ponding is possible. Storms are expected to
form over central South Dakota by Wednesday afternoon and slowly
move east through the evening and overnight. By sunrise
Thursday storms should be approaching the I-29 corridor and
continue east through the remainder of the morning.

Thursday late afternoon to early evening showers let up briefly as
the LLJ and WAA decrease. The previously mentioned subtropical wave
begins to accelerate northeast out of the southern Rockies through
the overnight hours of Thursday into Friday. The LLJ and WAA once
again increase with the wave`s approach and showers and
thunderstorms reintensify along and south of Highway 20. These
will push slowly north-northeast with the wave through Friday
evening. Hot on the heels of the first wave, a second shortwave
will push through overnight Friday into Saturday. This round
also has the potential for brief periods of heavy rainfall.
These will gradually push east and rain will cease from west to
east through Saturday afternoon before exiting east of the CWA
Saturday night.

In total from 7pm tonight until 7pm Saturday ensemble guidance
indicates a high probability (> 80%) of widespread 0.25 inches of
rain. A narrow corridor from Yankton northeast to Marshall, MN also
has a high probability (> 80%) of seeing 0.50 inches. With a small
bullseye from Yankton to Sioux Falls with about a 75% probability of
an inch or more. We finally get a break from all the rain on Sunday,
with hopes for sunshine Sunday afternoon. Highs during the remainder
of the week will be in the 60s to low 70s thanks to the southerly
winds and strong WAA in the mid-levels. Sunday, however, the sun
should warm us nicely into the low to mid 70s. Unfortunately our
break is short, as an active pattern returns Monday through the
first half of next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1246 PM CDT Tue Sep 22 2026

Low stratus will hang around through the end of the period. Ceilings
are a mix of VFR over southwest Minnesota where clouds have thinned,
down to IFR for the remainder of the region. Some further thinning
of the stratus is possible through the middle of the period, but for
the most part ceilings are expected to remain MVFR or less.
Overnight, some patchy fog is possible for areas along and south of
Highway 18.

Late this afternoon to early evening showers begin to form over
central South Dakota. These should be light and scattered, slowly
working east through the late morning Wednesday before tapering off
after the end of the period. This afternoon, slightly breezy winds
will be gusting 15-20 kts out of the south-southeast. Mainly along
and west of the James River Valley. Winds increase through Wednesday
morning with gusts of 20-30 kts that will push east through the
day.

&&

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

&&

$$

DISCUSSION...AJP
AVIATION...AJP