442
FXUS63 KFSD 011141
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
641 AM CDT Mon Jun 1 2026

.KEY MESSAGES...

- A conditional Level 1 of 5 risk for severe storms covers the
  forecast area Monday afternoon. Chances are low (less than
  30%), but if a storm can form, large hail up to quarter size
  and isolated damaging winds could occur.

- Far western portions of the forecast area toward central SD
  could see an isolated strong to severe storm Tuesday evening.
  The main threats would be localized damaging wind and large
  hail if storms progress far enough east before weakening.

- High chances (50-80%) for rain return mid-late week. Timing
  and location of a late-day severe risk on Wednesday will
  depend on how quickly any early day storms clear the area.
  However, most of eastern South Dakota is covered by a Level 1
  or 2 out of 5 severe storm risk, higher around and north of
  Huron.

&&

.UPDATE...
Issued at 540 AM CDT Mon Jun 1 2026

Areas of fog have developed along/east of the Buffalo Ridge in
southwest Minnesota and is also scattered along Highway 14 in
east-central South Dakota. Dense fog is not expected, but early
morning commuters will see areas of reduced visibility.

Storm chances today and Tuesday are sparse and generally low
confidence. Much of today should be dry as surface and mid-level
ridging move slowly east across the area. That said, a wedge of
moderate instability is projected by mid-late afternoon in
response to steep 800-600mb lapse rates, mainly along and east
of I-29. With large scale forcing lacking, confidence in storm
development is rather low. However, if surface temperatures are
able to reach convective temp and overcome the cap, large hail
and localized damaging winds would be possible.

Unsettled conditions continue through the bulk of the week,
mainly to our west on Tuesday, but gradually shifting east into
our area Wednesday and Thursday. Details regarding the severe
risks in the SPC Days 2 and 3 outlooks are uncertain, with the
better chances looking to remain west of our area Tuesday and
to our north on Wednesday where more favorable shear profiles
reside.

&&

.DISCUSSION...
Issued at 1235 PM CDT Sun May 31 2026

An active pattern is expected over the next several days, although
severe weather appears to remain a minor threat. Patchy heavy rain
may play the bigger role with each event.

For this afternoon and tonight, a small corridor of low level
convergence and lift will focus near and just east of the James
Valley. Clouds have cleared through early afternoon and temperatures
have risen a touch. Along with this temperature rise is a turn in
the surface winds to a more south to southwest direction vs.
southeast. This is what is aiding in this low level convergence. The
latest model soundings indicate something around 1500-2000 J/kg CAPE
but weak, disorganized shear. This suggests severe weather should
remain limited, but maybe a cell merger or two could produce a
couple of updrafts strong enough to support hail to half dollar
and wind gusts to 60 mph. Stronger storms will likely drift
east or northeast at about 15 mph, so fairly slow moving. With
this slower storm motion in mind, will need to keep an eye on
the locally heavy rain potential. A handful of the latest hi-res
models are showing small areas of 1-3" of rain with this
development. One area to keep a closer eye on will be parts of
Western Lake county, Northeast McCook and western Minnehaha
where 1-3" of rain fell late last night.

The question becomes what will drive development; will it be diurnal
heating, which would allow updrafts to start developing around 19-
21z, or will it be the weak wave which moves into the area closer to
0-3z this evening. The latest HRRR and Nam output agree with the
later start times, with the Nam indicating a stronger cap and less
development, while the RRFS and RAP kick off development a little
sooner with weaker capping. With the clearing that we are seeing in
central SD towards the James Valley we may see some development by
mid to late afternoon as destabilization is more likely. Suspect
some development between about 5-6pm.

One last thing to watch out for, if we can get mid to late afternoon
development, the LFC are marginally low and a weak convergent
boundary should be in parts of south central and southeast SD, so an
isolated funnel or two will be possible.

While a marginal risk for severe weather is in place for Monday,
confidence in the chances of development are very low. A capping
inversion may win out and for now CAPE values only running around
1000 J/kg with continued weak shear, albeit a little bit better than
today.

Another wave moves through Tuesday but weak shear and weak
instability suggest if anything can develop severe weather is very
unlikely.

Wednesday into Thursday looks like the better chance for more clouds
and better rainfall chances. Broad southerly warm advection looks to
bring in some weak elevated instability as low pressure tracks east
through ND. For now not anticipating all day rainfall but should see
off and on chances Wednesday and Thursday as this low tracks by to
the north.

Friday into Sunday will see periodic weaker waves move through the
area with a continuation of relatively weak flow aloft. This
continued weaker shear environment should keep severe weather
threats very limited.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 640 AM CDT Mon Jun 1 2026

Areas of fog across southwest Minnesota and east central South
Dakota reducing visibility IFR or lower at the start of the TAF
period. This is not expected to impact TAF sites aside from some
shallow MVFR fog around KSUX early.

After fog dissipates, VFR conditions are expected to prevail
with variable winds generally 12kt or less.

&&

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

&&

$$

UPDATE...JH
DISCUSSION...08
AVIATION...JH