Wessington, South Dakota Weather Forecast Discussion

502
FXUS63 KFSD 080742
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
242 AM CDT Mon Sep 8 2025
.KEY MESSAGES...
- Low chances (around 30%) for isolated to scattered
  thunderstorms Monday late afternoon into Tuesday morning.
  Some could be strong to severe.
- Temperatures will be around average to slightly above average this
  week, in the upper 70s to 80s.
- Canadian wildfire smoke begins to drift into the region today
  and continues through at least mid-week.
- Additional chances for thunderstorms in the latter half of the
  week. Details are uncertain at this time.
&&
.DISCUSSION...
Issued at 241 AM CDT Mon Sep 8 2025
TODAY AND TONIGHT: Canadian wildfire smoke will begin to drift back
into the region today. The thickest near surface smoke looks to stay
west of the Missouri River, but some degradation in air quality
may still be possible. Tuesday the thicker smoke looks to begin
pushing east. Sensitive populations may need to take
precautions over the next few days to limit exposure.
Clouds continue to build in as a weak mid-upper waves moves slowly
east from Wyoming. Strong WAA on southerly winds ahead of the wave
bring moisture into the region. Weak instability develops and lapse
rates steepen as a result. Temperatures in the 850 mb layer increase
to 16-20 degrees C. Mixing this down to the surface will result in
high temperatures in the upper 70s to 80s. Average high temperature
for September 9 is 78-80 degrees F. This average to slightly above
average trend looks to continue through the rest of the week.
Winds will become breezy this afternoon as the SPG tightens ahead of
the approaching wave. Southerly wind gusts of 20-25 mph are expected
for areas along and east of the James River Valley, with a few 30
mph gusts possible east of the Highway 60 corridor. Winds are
expected to remain breezy through the evening and first part of the
night. As the system begins to move east in the late afternoon there
is a low chance (around 30%) that showers and thunderstorms develop.
Continued moisture advection through the day will work to further
destabilize the atmosphere (1500-2000 J/kg CAPE) and lapse
rates continue to increase (7.5-8 C/km). However, deep layer
shear is lacking at only 20-25 kts. With a very strong cap in
place, it is highly uncertain that storms will be able to
initialize considering the very weak convergence along the
surface boundary. There are two scenarios that may play out
Monday late afternoon into the overnight. The most likely
scenario is that we do not break the cap, and no storms form, or
only very isolated storms form. Then as the main mid-level wave
moves through later Monday night into early Tuesday morning we
get some elevated showers and thunderstorms (around 30% chance)
that form roughly along and east of I-29 then move east. The
second, less likely scenario is we manage to break the cap in
the late afternoon, and isolated to scattered thunderstorms
develop along the James River and move east. In either scenario,
with the marginally favorable thermodynamic profile in place,
some storms could be strong to severe with the greatest threats
being one inch hail and 60 mph wind gusts.
TUESDAY - THURSDAY: Showers should be clear of the region by mid-
Tuesday morning as an upper ridge pushes in from the west. The rest
of the day should be dry. An impulse will work through the upper
pattern that may bring another round of storms Tuesday afternoon
into Wednesday morning. But confidence is low due to wide
variance in model guidance. Have left NBM PoPs for now, less
than 30%, focused over southwestern Minnesota. Wednesday and
Thursday both look to be dry as the ridge slowly meanders east.
Highs for all three days will be near to slightly above average,
in the upper 70s to 80s.
FRIDAY AND THE WEEKEND: Thursday afternoon the ridge begins to
weaken as a strong trough digs over the western United States. A
ridge rider wave will work through the area Friday, bringing chances
for storms Friday afternoon and evening. Saturday looks to be dry in
the afternoon before the strong closed upper low begins to pivot
into the region. As it does so storm chances will increase Saturday
evening and through the day Sunday. High temperatures will continue
to be near to above average in the 80s Friday and Saturday, and in
the 70s to 80s Sunday.
&&
.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1014 PM CDT Sun Sep 7 2025
A band of mid-lvl clouds continues to develop late this evening
and will develop further into the overnight hours. Focus
continues to appear along and east of I-29 into daybreak where a
few sprinkles to even small thunderstorms may develop. Weak LLWS
will also develop through mid-morning as the LLJ increases
upwards of 35-40 knots.
Variable VFR cloud cover expected through the day on Monday,
with potential for afternoon CU field to develop as low-lvl
moisture increases. Southwest surface winds increase through the
day, gusting to 30 knots at times.  A front will focus
convection potential in central SD by early evening, likely
keeping much of the area dry through the evening.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...AJP
AVIATION...Dux

NWS FSD Office Area Forecast Discussion