FXUS63 KFSD 231938
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
238 PM CDT Sun Aug 23 2026

.KEY MESSAGES...

- Showers and storms should be a bit more widespread tonight 
  (50- 70%). Locally heavy rain and isolated severe storms are 
  possible. Coverage and intensity have been trending down a 
  bit however.

- Monday evening and night could see an isolated severe storm, 
  with the better chances in central SD and also near highway 
  14.

- Otherwise most days through next week will see highs in the
  80s and lows in the upper 50s to mid 60s.

&&

.DISCUSSION...
Issued at 237 PM CDT Sun Aug 23 2026

A pair of waves are affecting the area, or nearby, today. The first 
is moving southeast through Nebraska and is keeping any instability 
to the south and west bottled up. Model soundings not hinting at a 
whole lot of activity this afternoon, with a fairly dry and stable 
air mass in place.

Tonight a second wave will pass by to the north and will swing a 
little bit of mid level moisture into the area. As this moisture 
moves in, some weak elevated instability, likely 500-750 J/kg CAPE 
develops. This will support some scattered shower and isolated 
thunderstorm activity, but for now severe weather looks
unlikely. A few pockets of heavier rain are also possible, but
also trending downward.

Monday will see temperatures warm a bit with humidity likely to 
increase as well. This is in response to strengthening southerly 
flow as a stronger wave moves east along the Canadian border. This 
will increase instability, especially to the northwest of the area, 
and should bring scattered thunderstorms to parts of central SD and 
near the highway 14 corridor. With the potential for about 1000-1500 
J/kg CAPE and decent unidirectional shear, and isolated severe storm 
will be possible in these locations. One area to watch will be near 
northwest IA late Monday afternoon and evening where there are some 
hints the cap could weaken a bit as elevated moisture advection 
bring some instability to that area. Low confidence, but something 
to monitor.

Northwest flow aloft Tuesday into the weekend will keep seasonally 
warm temperatures in place with highs in the 80s and lows from the 
upper 50s to mid 60s. Starting to see a little more consistency on 
the next better chance for showers and thunderstorms on Friday. The 
latest Canadian, GEFS and EC ensembles all indicate about a 30-5- 
percent chance for a tenth of an inch or more of precipitation.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1216 PM CDT Sun Aug 23 2026

The main concern this TAF period will be the chance for showers
and storms. While isolated to scattered, the better chances will
be from about 3z to 12z with the better chances south of I-90.
With any thunderstorms and near any thunderstorms, brief MVFR 
conditions will be possible.

&&

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

&&

$$

DISCUSSION...08
AVIATION...08