Chancellor, South Dakota Weather Forecast Discussion

216
FXUS63 KFSD 081142
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
642 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.
However, dry conditions are short lived as a weak impulse works
through the upper pattern. As it does so another round of
storms are possible late 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 /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 633 AM CDT Mon Sep 8 2025
Breezy southerly winds today with gusts 20-27 kts, with the highest
gusts along the I-29 corridor and east of Highway 60. Winds slowly
decrease during the overnight hours to 15 kts or less by the end of
the period. LLWS of 35 kts at 2000 ft AGL is possible through 08.14Z
at KSUX.
Clouds are moving in ahead of a weak wave expected to bring isolated
showers and possibly thunderstorms to the area late this afternoon
into early Tuesday morning. Confidence in placement of afternoon storms
and their occurrence is low, so have opted to leave them out of
the TAF at this time. VFR conditions are expected through the
period unless a storm is present, where MVFR ceilings and
visibility may occur.
Confidence increases after midnight for KFSD. There is
potential for some of these to become strong to severe, though
confidence in severity is low. Should stronger storms form
threats include one inch hail and 60 mph wind gusts.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...AJP
AVIATION...AJP

NWS FSD Office Area Forecast Discussion