501
FXUS63 KFSD 310207
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
907 PM CDT Sun Aug 30 2026

.KEY MESSAGES...

- Low chances (<= 20%) for showers will persist into Monday.
  Chances for rain increase up to a 50-80% chance for Tuesday.
  Severe storms could accompany this chance for rain though
  details remain uncertain. Please continue to monitor the
  latest forecast.

- Near to above normal temperatures look to continue through the
  entirety of this week. Chances (20-40%) are possible on
  Wednesday and Thursday before decreasing for the rest of the
  week.

&&

.UPDATE...
Issued at 858 PM CDT Sun Aug 30 2026

A trough is ejecting out of the northern Plains and into southern
Canada this evening, which is going to help send a cool front
through most of the area tonight. A line of strong storms
associated with this system is moving across central North
Dakota and far north-central South Dakota, but is expected to
remain north of the area tonight. Further development of strong
thunderstorms southward into our area is not expected given the
best upper support is displaced to our north. However, with
some weak PVA moving into the area from the southwest through
tonight, can`t rule out some showers developing as the frontal
system moves into the area late tonight into early tomorrow
morning. Dry low-level air should prevent most of this activity
from reaching the ground though, so only light showers to
sprinkles would be expected if this activity develops.

Also, a few stronger wind gusts look to occur immediately
behind the frontal passage mainly in south-central South Dakota
tonight, where gusts could be as high as around 35 mph. Did
blend in some of the NBM90th in the forecast to account for
this. Any of these higher winds will diminish fairly quickly
after they begin.

&&

.DISCUSSION...
Issued at 231 PM CDT Sun Aug 30 2026

Hot and humid conditions continue this afternoon as high
temperatures have warmed to the 80s and 90s with dew points in the
60s and 70s. This is resulting in heat indices up to upper 80s and
90s with a few locations touching 100F. A shortwave trough continues
to take on a negative tilt over eastern Montana/western North
Dakota. This will keep the majority of strong to severe storms in
this area. This wave will also be responsible for a cold front that
remains on track to push into the forecast area late tonight. Latest
hi-res guidance shows little to no rain developing along this
boundary due to large capping in place ahead of the boundary. At the
same time, cloud cover will increase aloft. Despite the front
pushing through the area, low temperatures look to stay quite warm
overnight with lows only falling to the 60s and 70s. In fact, some
locations will come within 3 degrees of their record warm lows. With
dew points remaining in the 60s overnight, tonight will continue the
muggy conditions we have experienced this weekend.

Monday will be similar to the weekend though a touch cooler as the
thermal ridge gets pushed off to the south and east thanks to the
previously mentioned front. That said, high temperatures still look
to remain in the 80s to potentially reaching 90F in a few locations.
The previously mentioned cold front will fully push through the
forecast area by Monday afternoon, resulting in most likely another
dry and hot day. Dew points will lower to the 50s and 60s, keeping
humidity values lower than what we saw this weekend. If rain were to
develop along the front, thunderstorms may be possible though this
is unlikely (<= 10% chance) to happen. Low temperatures will remain
warm though a bit cooler than Sunday`s lows, with temperatures
bottoming out in the 60s.

A shortwave trough will eject out from the Rockies and into the
Northern Plains on Tuesday. The mass response from this wave will
return the previously mentioned front northwards, but this time as a
warm front. Latest guidance still varies on how far north this front
will return. A few of the hi-res models show the front returning
well into the forecast area. But the ensembles as well as the
machine learning (ML) guidance keeps the front just south of highway-
20 down to around I-80. Tough to say how far north the front will
return but the ensembles continue to show moderate to high
probabilities (50-80%) for rainfall amounts to exceed a tenth of an
inch of rain across the area, signaling at least elevated showers
and storms are on the table north of the front. Instability values
will also depend on where the front sets up. Thus, severe weather
remains possible as supported by the latest ML guidance showing a 5-
15% chance for strong to severe storms.

Chances (20-40%) for rain will remain in the forecast for the rest
of the week and next weekend. The highest probabilities look to come
on Wednesday and Thursday as a more active pattern continues aloft.
Medium range guidance is becoming more consistent with upper level
ridging building over the central CONUS towards the end of next week
and next weekend. This would result in warmer temperatures,
potentially back into the 90s, and most likely drier conditions. In
fact, this pattern is shaping up to be an omega block pattern.
Pattern recognition and forecast experience suggests that this
pattern may retrograde west over the coming days. The ensembles are
also in favor of this as their trends have already been amplifying
the ridge as well as pushing the ridge axis further west as well.
Surface features are more uncertain, so questions remain regarding
surface moisture and resulting humidity. Will be keeping an eye on
how this pattern evolves over the course of the week.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 642 PM CDT Sun Aug 30 2026

VFR conditions expected through the period. Can`t rule out some
low stratus developing behind a cool front around daybreak, but
chances for this are low (<=20%). This eastward moving front will
turn southwesterly winds to the north-northeast late tonight through
early tomorrow morning. There looks to be a slight uptick in winds
immediately following the frontal passage in south-central
South Dakota, but will likely see sustained winds only pick up
to around 10-15 kts during that time. Though a few showers are
possible ahead of the front, thunderstorms look unlikely
through the period.

&&

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

&&

$$

UPDATE...Samet
DISCUSSION...Meyers
AVIATION...Samet