115
FXUS63 KFSD 291130
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
630 AM CDT Fri Aug 29 2025

.KEY MESSAGES...

- Unsettled wetter pattern will prevail through at least the
  first half of the holiday weekend. Severe weather risks are
  low, but non-zero risks for a few weak funnel clouds with
  developing afternoon showers today (south-central SD) and
  Saturday (northern through eastern portions of the area).

- Areas of heavier rainfall are possible tonight into Sunday.
  Moderate (40-50%) chance of exceeding 1 inch focused south of
  I-90 and especially toward the Missouri River Valley.

- Scattered showers/storm chances linger early next week. Severe
  weather risks generally remain low, but may have to monitor
  Tuesday for a few stronger storms.

- Brief shot of colder air pushes into parts of the northern
  Plains/Upper Midwest mid-late next week. Uncertainty is high
  regarding how far west the coldest air will track.

&&

.DISCUSSION...
Issued at 340 AM CDT Fri Aug 29 2025

TODAY: Most of the forecast area will remain dry today with
attention focused toward a broad upper wave currently located
over southeast Montana. Decent model consensus this morning
shows this wave evolving into a weak closed low over western
South Dakota by late this afternoon with ample mid-upper level
moisture and weak lift resulting in increasing clouds through
the morning. In areas east of the James River Valley, moisture
looks to be confined above 12-15kft AGL, so rainfall would be
tough to come by. West of the James River, though, more robust
moisture below 10kft AGL may be enough for scattered showers.
Instability is weak with near-moist adiabatic lapse rates, but
may be enough for a few isolated thunderstorms.

Weak shear and limited instability should preclude any severe
weather risks in our area. However, the latest RAP does show
elevated values for Enhanced Stretching Potential in south
central SD, so cannot rule out a weak funnel in the developing
stage of showers this afternoon.

TONIGHT-SATURDAY NIGHT: The upper low slowly tracks southeast
and while models still vary on its eventual location, broad
consensus places it somewhere in the south-central South Dakota
to north-central/northeast Nebraska vicinity by Saturday into
Saturday night. Exact track of this feature and its associated
surface low will dictate where pockets of heavier rain could
occur over the next 48 hours or so. However, hi-res ensembles
(HREF/REFS) currently place higher chances (40-50%) of 24-hour
totals exceeding 1 inch over portions of south-central South
Dakota by daybreak Saturday, then expanding east down the
Missouri River Valley through Saturday night.

Northeast of this heavier rain potential, rainfall amounts could
drop off sharply with a drier east-southeast flow more prevalent
around a surface high in northern Minnesota. That will not mean
zero rain chances as weak instability could produce scattered
afternoon showers or storms. Similar to today, a zone of higher
Enhanced Stretching Potential indicates a non-zero risk for a
few funnels with developing showers, with the current focus for
this across northern through eastern portions of our forecast
area. Exact location of this risk will similarly depend on the
eventual placement of the upper low and northeastward extent of
more widespread rain activity.

SUNDAY-TUESDAY: The weak upper low continues to slowly meander
southeastward during the latter half of the Labor Day weekend,
but it`s proximity will keep a moderate (40-60%) chance of
showers and scattered storms around into Sunday, with lesser
chances lingering into Labor Day itself. Again, a lack of shear
and instability will keep severe risks at bay.

By Tuesday, we`ll be looking northward at an approaching trough
and associated cold front. While both features will likely still
be north of our area late Tuesday, some solutions are showing an
increase in mid-upper level winds across the Dakotas, which could
bring some increase in deep layer shear by the late afternoon
and evening. With model agreement lacking, difficult to say
whether we will have a risk of severe storms, but this period
does present to greatest (albeit still low) potential over the
next several days.

WEDNESDAY-THURSDAY: Aforementioned cold front pushes southward
through Minnesota, though some solutions drag the axis of the
colder air farther west into the eastern Dakotas. Discrepancies
are resulting in a wide range of potential temperatures by the
end of this forecast period with a 10th-90th percentile spread
exceeding 10-13 degrees in the NBM by Wednesday and Thursday.
Colder solutions keep highs in the 50s for some areas both days,
while the warmer end of the spectrum supports widespread 70s.
Needless to say, confidence in mid-late week temperatures is
low, with higher confidence that we will return to a drier
pattern through the latter half of next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 630 AM CDT Fri Aug 29 2025

Areas of fog with LIFR-VLIFR visiliby through portions of the
Missouri River Valley and Highway 20 corridor to start this TAF
period. Conditions are expected to improve rapidly by 14Z, with
VFR conditions then expected to dominate through the remainder
of the period.

Locations mainly west of US Highway 81 could see scattered -SHRA
off and on through the period with isolated thunder possible.
While the -SHRA could briefly drop visibility to MVFR range,
confidence in thunder and/or reduced visibility is too low to
include in KHON TAF at this time.

&&

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

&&

$$

DISCUSSION...JH
AVIATION...JH