041
FXUS63 KFSD 141149
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
649 AM CDT Sun Sep 14 2025

.KEY MESSAGES...

- Isolated strong to severe storms are possible this afternoon
  and evening, with damaging winds up to 60 mph and marginally
  severe hail the main threats.

- Temperatures remain well above normal into early next week.

- A cold front brings another chance of rain and storms late
  Tuesday into Wednesday, and then ushers in cooler, more
  seasonal temperatures starting Wednesday.

&&

.DISCUSSION...
Issued at 339 AM CDT Sun Sep 14 2025

It`s a warm and muggy start to our day especially for
mid-September standards, with temperatures in the 60s to low-70s.
Another unseasonably warm day is in store for today with highs
ranging from the low-80s west (where cloud cover will be thickest
through the day) to the mid-to-upper-80s east. Did blend in a bit of
the NBM 25th percentile to highs for today due to the cloud cover
forecasted. The main story for today will be the chance for rain and
storms, with the potential for isolated severe storms as a
negatively tilted trough ejects over the region. At the surface, a
low pressure system located over western Nebraska will lift north
through western South Dakota through the day into tonight. Mid-level
lapse rates are expected to remain fairly weak through the day
today, around 6-6.5 C/km and the tall, skinny nature of the
CAPE profiles will likely make sustained updrafts hard to come
by. However, any updraft that can be maintained will have
around 35-45 kts of bulk shear to work with and so can`t rule
out isolated severe storms. Skies are expected to be mostly
cloudy across the area today, and this will help to limit some
daytime heating and thus limit the amount of instability that
develops. However, anywhere that sees longer periods of sunshine
in the afternoon will have a greater potential for seeing a
stronger storm and so trends will need to be watched closely
through the day. The main threat will be damaging wind gusts up
to 60 mph and marginally severe hail. A tornado cannot be
entirely ruled out closer to the surface low, but by peak
daytime heating the low should be moving north of the area and
thus limiting the tornado threat locally. Any showers and storms
will generally move south to north as they develop in tandem
with the surface low, but will also be gradually shifting
eastward with the push from the upper-level wave into tonight.
Storms should exit the area to the east after 2-3 am, though
wrap-around light showers around the low pressure system may
clip the Highway-14 corridor through sunrise tomorrow.

Skies will clear out tomorrow as the low moves into southern Canada,
and with continued southerly flow this will allow for another
unseasonably warm day with highs mainly in the mid-80s. Another
trough moving across the northern Rockies will push towards our area
tomorrow night, sending a weak wave across south-central South
Dakota by daybreak Tuesday. This may help fire off a few showers
along and just ahead of a cold front for areas west of the James
River Tuesday morning, but the better chances of rain will arrive
late Tuesday into Wednesday as the trough arrives and pushes the
front across the area. The atmosphere will be unstable ahead of the
front, so thunderstorms are likely with this activity. Shear may be
lacking, but can`t entirely rule out a strong to marginally severe
storm Tuesday afternoon. With most of the area expected to be ahead
of the west-to-east moving front on Tuesday, another warm day is in
store with highs well into the 80s, potentially reaching 90
over parts of northwest Iowa where the front moves through last.


Most guidance shows an upper-level low moving out of southern Canada
right behind the late-Tuesday into Wednesday trough, and this could
keep general cloudiness along with sporadic rain chances through the
remainder of the work week as it hangs around the region. Due to the
clouds and the aforementioned frontal passage, it`s looking likely
we`ll see cooler temperatures starting Wednesday, with highs
returning to the 70s and lows in the 50s. The upper-low finally
pushes east of the area by the start of next weekend, which could
bring the return of mostly sunny skies unless another trough follows
behind it. But as of now, keeping next Saturday dry.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 646 AM CDT Sun Sep 14 2025

Lingering fog in and around KHON will dissipate over the next hour
or so as southeasterly winds pick up. These winds will continue
picking up into the afternoon gusting up to 25 kts along and west of
I-29. Could see some gusts locally as high as 30 kts into south-
central South Dakota this afternoon.

A challenging thunderstorm forecast ahead as guidance shows a
couple of quick moving bands of rain and storms moving through
the area from southwest to northeast this afternoon and evening,
all moving through at various times and various intensities.
Higher confidence for a more widespread band of storms to
develop early this evening and thus added TEMPO groups to all
sites mainly between 0 and 3z, though timing will likely to be
refined in future updates. We`ll call that the "main band" for
simplicity. There is also a chance of a band of storms impacting
the TAF sites before the main band, but this one would likely
be more scattered and quick moving and so PROB30 groups are
sufficient for that threat. After the main band, guidance hints
at a third one moving through mainly east of the James, but
because instability will be waning overnight, left
-SHRA in the PROB30 group for KFSD and KSUX though isolated
thunder can`t be entirely ruled out.

Any showers and storms should exit the region by 7-9z, though
lingering showers are possible in KHON at the end of the period
depending on the position of a low-pressure system that`ll be moving
through the western Dakotas. Low confidence for any impacts to KHON
at this time with that activity, but it could bring lower clouds and
misty conditions if it impacts the area.

&&

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

&&

$$

DISCUSSION...Samet
AVIATION...Samet