809
FXUS63 KFSD 272319 AAA
AFDFSD

Area Forecast Discussion...UPDATED
National Weather Service Sioux Falls SD
619 PM CDT Wed Aug 27 2025

.KEY MESSAGES...

- Scattered showers and storms are expected to develop this
  evening, mainly in southwestern Minnesota. An isolated strong
  to severe thunderstorm or two cannot be ruled out through mid
  evening.

- Temperatures return near seasonal averages for today and
  Thursday, with a slightly cooler day Friday and through the
  weekend.

- More widespread rain chances and cooler conditions return by
  Friday night through the upcoming holiday weekend. Details
  remain uncertain heading into the weekend so continue to
  monitor the latest forecast.

&&

.DISCUSSION...
Issued at 239 PM CDT Wed Aug 27 2025

TODAY AND TONIGHT: Warmer temperatures today as slightly breezy
southerly winds bring northward a warmer air mass. Temperatures in
the 850 mb layer will increase to 16-22 degrees C. At the surface
that translates into highs in the upper 70s and mid 80s. Lows
tonight will be mild, in the upper 50s.

Looking aloft, a weak northwest to southeast orientated jet streak
right entrance will be situated over our region. A weak mid-level
wave and surface low pressure trough axis will work together to
trigger a round of showers and possibly weak thunderstorms this
afternoon into the early morning Thursday. Mid-level lapse rates are
weak at 6.5 deg C/km or less. Instability is around 1200-1500 J/kg
of long and skinny CAPE. This thermal profile does not lend itself
to strong storms. However, 0-6 km Bulk shear is 30-40 kts, which
could support a few isolated stronger updrafts. These stronger
updrafts could produce hail up to the size of a quarter and wind
gusts up to 60 mph. The area most likely to see any stronger storms
is along I-90 from Mitchell, SD east to Jackson, MN and north. This
matches well with the SPC Day 1 Marginal (level 1 of 5) Outlook. As
far as rain totals are concerned, a quick few hundredths up to
around a quarter of an inch is expected. Due to the isolated to
scattered nature of these storms, not everyone will see rain, with
the most likely area being southwest Minnesota.

One final consideration for tonight into early Thursday morning is
patchy dense fog development. Overnight winds will become light and
variable as the boundary layer approaches saturation. As a result,
patchy fog may develop over central South Dakota and along and north
of I-90. Please use caution during your morning commutes.

THURSDAY AND THE WEEKEND: An upper level ridge keeps conditions
seasonably warm for Thursday. Highs will be in the upper 70s to mid
80s with lows in the mid 50s to low 60s.  Winds will be light out of
the east. A very low chance (<20%) for light showers Thursday
morning over northwestern Iowa as a weak boundary tries to take
advantage of what little moisture is available. However, a dry
subcloud layer will likely evaporate any moisture before it reaches
the ground.

Friday we see a mid-level short wave and surface low pressure begin
to move into the region. There remains high uncertainty in this
system due to low model agreement. The GFS and NAM have WAA showers
beginning a full 6-9 hours earlier than the arrival of the main
wave. Models come into better consensus as the main waves moves
through Saturday. However, track of the surface low varies
between all four mid-range models. What they do agree on is the
slow eastward progression of the entire system. What this means
is the weekend is looking rather soggy and dreary. Confidence in
rain totals is low due to the aforementioned uncertainty.
However, the GFS and EC long term guidance indicate 1-2 inches
could be possible through Monday morning, especially for areas
of southwestern Minnesota. All metrics used to determine
severity are low, suggesting these should remain light to
moderate showers, with an occasional rumble of thunder
possible. Please continue to monitor the forecast for updates as
details become clear. Highs for Friday through Sunday will be
in the upper 60s to 70s with lows in the 50s.

NEXT WEEK: Long term guidance for next week is in very low
agreement. They do indicate multiple waves will pass through
bringing rain chances periodically through at least mid-week. But
other than that details at this time are sparse. Highs are expected
to remain seasonable for this time of year, in the upper 70s to low
80s.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 614 PM CDT Wed Aug 27 2025

Satellite images at 28.00z show scattered thunderstorms along a
boundary from near Brookings SD to New Ulm MN early this
evening, tracking slowly south. Storms may produce small hail,
frequent lightning, and gusty erratic winds. While isolated
storms cannot be ruled out further west near KFSD to KMHE, this
seems unlikely.

Outside of this activity through mid evening, expect VFR
conditions to prevail across most of the region through at least
09z. Model guidance shows potential for fog, dense at times, to
develop in portions of southwest MN, central SD, and perhaps
also near KSUX from 10-14z. Confidence in fog development at the
TAF sites is fairly low but will continue to monitor potential
overnight. Light easterly or southeasterly winds and VFR
conditions will prevail during the day Thursday.


&&

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

&&

$$

DISCUSSION...AJP
AVIATION...BP