803
FXUS63 KFSD 211755
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1255 PM CDT Tue Jul 21 2026

.KEY MESSAGES...

- Temperatures remain below normal for the rest of the work
  week. Departures from normal will average 5 to 8 degrees below
  normal.

- Outside of two light rain chances early Wednesday and
  Thursday night, much of the 7 day forecast is dry.

- Temperatures this weekend into early next week rise well above
  normal with highs well into the 90s in most locations. Heat
  related headlines may be needed at times this weekend.

&&

.DISCUSSION...
Issued at 1252 PM CDT Tue Jul 21 2026

THIS AFTERNOON: Plenty of cool air aloft has poured southward into
the region, with morning strato-cu continuing to slowly mix upwards.
 High temperatures given the cloud cover will remain in the upper
70s to lower 80s. Aloft, the increasing northwesterly flow could
bring high level smoke though the region into the night.

TONIGHT: Surface high pressure drifts into the Midwest and western
Great Lakes region overnight.  Winds turn light and variable which,
may lead to fairly cool overnight lows in areas east of the James
River.  The low-lvl airmass is fairly dry, so fog probabilities will
remain very localized to sheltered valleys and riverways.
Further west, high level clouds increase after midnight as mid-
lvl warm advection focuses over the West River areas and the
Nebraska panhandle. A few sprinkles to light rain showers may
reach the central portions of SD into the James River valley by
daybreak.

WEDNESDAY:  A subtle shortwave drops southeast from the Black Hills
region across central Nebraska during Wednesday. Much of the
CWA will remain under the influence of low-lvl dry air advection
from the northeast during the day. While mid-lvl lift spread
east towards the I-29 corridor, most guidance struggles to
produce more than sprinkles east of I-29, with the best low-lvl
saturation focused along and south of the MO River valley. Any
QPF that falls will be light. The most impact from this system
may be increased cloud cover and temperatures in the 70s and
80s.

THURSDAY: After another night with variable cloud cover, light
winds, and cooler temperatures, Thursday will see surface winds
return back to the South early in the day. We`ll be watching another
slightly stronger wave cross the Rockies during the day on Thursday.
Model guidance has been a bit all over with this wave, with the GFS
and about 40% of it`s ensemble members stubbornly further to the NE
than all of the other major model guidance. The ECMWF/ICON/GEM/UKMET
and to some degree NAM force this wave further southeast bringing
the majority of rain chances to western SD, central and
northern NE and western Iowa. The latest NBM has hedged a bit
more towards the drier solutions as more drier input is
received, and I continue to favor the greatest focus for rain
along the MO River valley. That said, if there is some shift
towards the outlier solutions, moisture convergence could be
enough to at least produce some meaningful rain into Thursday
night.

FRIDAY-MONDAY: A 600 DM ridge builds through the Central Plains
heading into the upcoming weekend.  This ridge, unlike the past
weeks, it a bit more suppressed which may serve to delay the most
intense heat into the second half of the weekend.  Temperatures are
likely to surge into the 90s Saturday and Sunday with initial focus
for the hottest temperatures west of the James River Saturday and
then further east Sunday.  Even with the slightly warm biased NBM,
there is some potential for heat related headlines this weekend.
Convection chances remain low for Saturday, but may rise slightly on
the edge of the EML late Sunday. A very hot Monday is also
possible with a similar setup for weak flow convection on the
edge of the EML in the afternoon evening.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1154 AM CDT Tue Jul 21 2026

Strato-cu gradually lifting this afternoon into VFR levels. A
gusty northerly wind will persist into early evening before
relaxing.

VFR conditions are expected overnight, with a broken to overcast
mid-upr lvl cloud field expected to move east after midnight
and continue into the morning hours. Winds will turn light and
variable in most locations by daybreak and may remain that way
well into the day.

Light rain/sprinkles move into the James River and Missouri
River valley by mid-morning, though any spread northeast will be
minimal.

&&

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

&&

$$

DISCUSSION...Dux
AVIATION...Dux