529
FXUS63 KFSD 082252
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
552 PM CDT Mon Jun 8 2026

.KEY MESSAGES...

- If storms can develop this afternoon to early evening, an
  isolated severe storm could produce large hail up to half
  dollar size and damaging winds to 60 mph.

- Moderate to Major Heat Risk Tuesday (all areas) and Wednesday
  (southeast) indicates a potential for heat-related illness for
  those without adequate cooling and hydration. Protect yourself
  against the heat and check on more vulnerable individuals such
  as the elderly, children and those with chronic illnesses.

- A Heat Advisory has been issued for most areas near and south
  of I-90 from 1 pm to 9 pm Tuesday as heat indices climb above
  100 degrees.

- Tuesday looks to bring the greater severe threat of the next 3
  days, with a large hail threat toward central South Dakota and
  Nebraska in the evening transitioning to damaging winds up to
  75 mph farther east late evening into the night. Isolated
  tornadoes are possible.

- The cold front triggering storms on Wednesday is trending
  faster, with the associated severe storm threat shifting east
  into mainly Minnesota and Iowa.

&&

.DISCUSSION...
Issued at 254 PM CDT Mon Jun 8 2026

Low stratus has helped split our area temperature wise, with
temperatures mainly in the 70s west of I-29; meanwhile near and east
of I-29, we`re in the 80s where less cloud cover has been
today. These areas that have cleared out the stratus could see
an isolated thunderstorm through the early evening where
1,500-2,000 J/kg of MLCAPE has developed. The better shear is
west of this area, so severe weather chances look quite low
through this evening. But if an updraft could maintain itself,
60 mph winds and half dollar sized hail would be the main
threats. These storms should mostly be diurnally driven, so
expect a weakening trend after the sunsets. Can`t rule out some
patchy fog tonight; but overall, a quiet night is ahead for us.
A more active Tuesday night is expected, more on that below.

Rain-wise, most of the daytime hours Tuesday should be quiet. The
main story will be the building heat and humidity. Any morning fog
or low stratus should erode quickly, allowing for daytime heating to
take off quickly into the afternoon. Look for highs to be in the 90s
for the majority of the area, with dew points into the 70s over
northwest Iowa, far northeast Nebraska, and adjacent areas of
southeastern South Dakota. This will bring heat indices into the
triple digits for areas especially near and south of I-90. For
this reason, did go ahead and issue a heat advisory for portions
of our area from 1 pm to 9 pm Tuesday. The best overlap of hot
temperatures and higher dew points will be in the Sioux City
metro where heat indices could be briefly as high as 105
degrees. Make sure to stay hydrated out there and take frequent
breaks if you have to work outdoors or if you have any outdoor
activities planned.

The heat and humidity will also prime the atmosphere for strong
to severe storms heading into Tuesday night. An upper trough
will begin to dig in from the Canadian Rockies and send waves of
vorticity our way Tuesday into Tuesday night. Can`t rule out a
stray thunderstorm in the afternoon, but the better chances
arrive in the evening as storms likely develop off to our west
and then move through our area into the night. There will be
plenty of instability even as we lose daytime heating Tuesday
night, on the order of 2,000-3,000+ J/kg of CAPE. Bulk shear
values won`t be as impressive, around 30 kts or so, but this
should be sufficient to maintain strong to severe storms. With
the highly unstable atmosphere and soundings show some mid-
level dry air, damaging winds look to be the main threat and
could be as strong as 75 mph. Mid-level lapse rates up to 8.5
C/km and large CAPE profiles will lead to a secondary threat of
large hail to the size of a hen egg (2 inches) or slightly
larger. Lastly, tornadoes will also be possible especially in
the evening as hodographs show some decent low level curvature
in place and storms have a better chance at being rooted to the
surface. The tornado threat will be maintained overnight as
strengthening low level jet spreads into the area. With all
modes of severe weather possible during the overnight hours, be
sure to have a way for warning alerts to wake you up at night!

Storms look to push east of the area as a cold front starts moving
into our area. Most guidance now pushes this cold front mostly east
of the area by peak daytime heating, so the threat for severe
weather continues to trend eastward for Wednesday. Will have to
watch late Wednesday night/early Thursday morning as the main wave
moves through the area as this could help develop some storms
mainly near and south of Highway-20. Instability will be the
limiting factor, but the potential for shear pushing towards 60
kts will mean any storms will be worth watching if one could
even get going early Thursday morning. Looking ahead, cooler
temperatures and continued broad, low-end rain chances will be
maintained heading into the weekend as general troughiness
remains in place. Instability looks fairly weak during this time
frame, so severe weather chances look low. We will likely see
cooler temperatures especially into early next week when highs
in the 70s may start to become more widespread.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 550 PM CDT Mon Jun 8 2026

Mainly VFR conditions with occasional MVFR conditions will
persist this TAF period. Taking a look across the area, quieter
conditions persist this afternoon with potential for a few
isolated showers and thunderstorms mainly along and east of
I-29. With this in mind, decided to keep a PROB30 group for KSUX
since we`re already starting to see some development. Otherwise,
lighter winds are expected overnight to end the TAF period.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory from 1 PM to 9 PM CDT Tuesday for SDZ059>071.
MN...None.
IA...Heat Advisory from 1 PM to 9 PM CDT Tuesday for IAZ001-002-
     012>014-020>022-031-032.
NE...Heat Advisory from 1 PM to 9 PM CDT Tuesday for NEZ013-014.

&&

$$

DISCUSSION...Samet
AVIATION...05