077
FXUS63 KFSD 211841
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
141 PM CDT Fri Aug 21 2026

.KEY MESSAGES...

- Mainly dry weather is expected for the rest of today. Low
  chances (less than 20%) for showers and storms during the
  late afternoon and into tonight along and south of the
  Missouri River. Severe weather risk is low.

- Slightly cooler weather for the weekend. Saturday should
  remain dry with rain chances (40-70%) returning to portions
  of the area by Sunday morning. Rainfall amounts could exceed a
  tenth of an inch.

- Additional chances for rain, and potentially thunderstorms (5-
  15%), are possible through next week. Details are uncertain,
  so continue to check the latest forecast for the most up to
  date information.

&&

.DISCUSSION...
Issued at 139 PM CDT Fri Aug 21 2026

Quiet conditions persist this afternoon as temperatures have warmed
to the 70s and 80s across the area. Quiet conditions are expected to
continue for the rest of the day as the cold front has fully pushed
through the area. This will keep storm chances south and west of the
forecast area. Can`t rule out the low possibility (less than 20%) of
a shower or weak storm passing along and south of the Missouri River
this afternoon, evening, and potentially into the overnight hours.
Should this occur, the chance for a severe storm is low. Surface
ridging will begin to slide into the forecast area tonight,
resulting in light and variable winds with lows falling to the upper
50s to low 60s. Patchy fog is again on the table but with drier air
in place, think that any fog that does develop will once again be
tied to a few river valley`s.

Saturday begins the weekend on the quiet side as high pressure
pushes through the Northern Plains. High temperatures will be a bit
cooler in the upper 70s to low to mid 80s, with a continuation of
light northerly winds. This will make for a wonderful Saturday,
perfect for outdoor activities! Rain chances will increase late
Saturday night through Sunday as a weak shortwave trough rounds the
top of a building upper level ridge. This will result in increasing
chances for rain across the area for the day on Sunday. Cloud cover
with the associated chances for rain will keep high temperatures a
bit cooler in the upper 70s to low 80s. While some showers are
possible during the morning timeframe, the highest chances for rain
will come Sunday evening and night as the main shortwave pushes
through the area. The ensembles show a broad 40-70% chance for
rainfall totals to exceed a tenth of an inch. Soundings show some
elevated instability in place so thunderstorms are possible, though
severe storms are not expected at this time due to weak shear
profiles. With non-severe storms on the table, rainfall amounts
could be locally higher depending on how storms track.

An active pattern continues aloft for next week. Medium range
guidance shows shortwave troughs continuing to push through the
Northern Plains within the northwest flow regime. This will lead to
chances for rain almost every day next week. However, the ensembles
show a large variance in rainfall probabilities due to the
differences in these upper level features. Latest machine learning
(ML) guidance does show low probabilities (5-15%) for severe weather
throughout the week. Details for severe weather remains uncertain so
continue to check the forecast for the most up to date information.
Aside from rain and storm chances, high temperatures look to remain
in the upper 70s and 80s.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1225 PM CDT Fri Aug 21 2026

VFR conditions are expected for the TAF period. High pressure is
resulting in clear skies and light winds across the area. Winds will
remain light and northerly through the rest of the daylight hours
before going light and variable this evening. PAtchy valley fog is
again possible tonight though confidence is too low to include in a
TAF. Light northerly winds will pick up tomorrow morning to end the
TAF period.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...Meyers