290
FXUS63 KFSD 311917
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
217 PM CDT Sun Aug 31 2025

.KEY MESSAGES...

- An unsettled pattern persists through Labor Day. The highest
  overall rain chances remain south of I-90, however isolated to
  scattered afternoon/evening showers and storms will occur
  farther to the north.

- With this activity, widespread heavy rain is not expected,
  but ribbons of heavier rainfall exceeding an inch are possible
  where narrow bands of showers/storms persist for multiple
  hours.

- Severe weather risk is low, but we continue to see a non-
  zero risk for weak funnel clouds with developing air mass
  showers during the afternoon-early evening.

- Chance of showers/storms lingers into Tuesday-Tuesday night.
  The severe weather risk remains low but with a little more
  instability a couple of stronger updrafts will be possible.

- An unseasonably strong upper level low will bring a shot of
  cooler air to parts of the Northern Plains/Upper Midwest mid
  to late week which will continue into the weekend but likely
  moderate a bit.

&&

.DISCUSSION...
Issued at 215 PM CDT Sun Aug 31 2025

Low pressure near the Missouri River will gradually shear and settle
south tonight into Monday. With weak flow and plenty of low to mid
level moisture, relatively tall skinny CAPE is expected this
afternoon into the evening which should result in some spotty shower
and very isolated thunderstorm chances. Because of the weak flow,
low LFC/LCL and fairly high moisture content, isolated funnel clouds
and very localized heavy rain are the main threats. Shortly after
the diurnal cycle comes to a close this evening, roughly 9 pm to 11
pm, the activity should wane and become more isolated. Closer to the
Missouri River late this afternoon through the overnight a more
steady rain will be possible but due to weaker instability heavy
rain is not expected in this area.

This low pressure weakens, shears out and drifts south on Monday
afternoon. A nearly saturated environment with weak instability
should allow for a few showers to develop, but the expectation
is for activity to remain more isolated. A few lightning strikes
will be possible but severe weather is not expected. An
extremely small area could see some brief heavy rain. With
plenty of cloud cover temperatures will not change a whole lot,
with lows tonight about 60 most locations and highs on Monday in
the lower to mid 70s.

Monday night into Tuesday will see the shower and isolated
thunderstorm threat continue as weak warm air advection is expected
ahead of a weak wave which is out ahead of a larger low pressure to
the north. At this time the better chances should be east of I-29.
While for now severe weather looks unlikely, shear does increase a
bit on Tuesday afternoon so will need to monitor the instability for
any upticks which would bring the threat for isolated severe
storms. With this warm advection surface temperatures will also
climb with highs from the upper 70s to lower 80s fairly common.

Unseasonably strong low pressure will deepen over southern Canada
around the Great Lakes and bring much cooler weather to the area
Wednesday into next weekend. Model agreement is fairly high with
this feature, so confidence is fairly high as well with temperatures
likely about 15-20 degrees below normal through this period. Other
than some spotty diurnally driven shower potential this period also
looks mainly dry and likely on the breezier side, especially
Wednesday into Friday when a couple of shots of stronger cold air
advection blow through.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1119 AM CDT Sun Aug 31 2025

The morning dense fog has lifted but some MVFR conditions
remain. IFR conditions will become possible this afternoon into
the overnight hours with the better chances closer to the
Missouri River and the upper level low in northern NE. MVFR
ceilings may redevelop closer to I-90 but confidence is lower on
this occurrence. Late tonight into Monday morning IFR
conditions will likely spread north to near and north of I-90
with lower confidence in occurrence closer to highway 14.

Otherwise, scattered showers and very isolated thunderstorms
are expected this afternoon into the evening. Severe weather is
not expected, but very locally heavy rain and isolated funnel
clouds will be possible. A more steady rain will be possible
closer to the Missouri River into northwest Iowa this afternoon
into the early overnight hours. Rain is expected to be more
isolated on Monday.

&&

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

&&

$$

DISCUSSION...08
AVIATION...08