096
FXUS63 KFSD 081141
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
641 AM 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 ping pong
  ball 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.

- Tuesday looks to bring the greater severe threat of the next 3
  days, with a large hail threat toward central South Dakota and
  Nebraska early evening transitioning to damaging wind farther
  east mid to late evening. 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.

&&

.UPDATE...
Issued at 515 AM CDT Mon Jun 8 2026

Near term we have see stratus become more widespread along and
east of Highway 81 in far eastern South Dakota, and areas farther
to the east should see stratus fill in from the south over the
next 1-2 hours. With stratus extending all the way into northeast
Kansas and northern Missouri, difficult to tell how quickly this
will erode and allow temperatures to sufficiently warm enough to
support storm development this afternoon. Farther west, seeing
additional stratus/cooler air spill southward through northern
South Dakota and think temperatures in our far west may struggle
to reach highs in the mid 80s projected by the NBM. Adjusted our
highs a bit lower than the NBM today as a result, especially in
our far west where some areas may struggle to top 80F. As such,
confidence in storm development this afternoon remains low, but
if a storm can develop (more favored north of I-90 near Hwy 81
to I-29 in recent CAMs), isolated stronger storms may produce
hail up ping pong ball size or brief gusts to 60 mph.

No significant change to the heat/humidity on Tuesday, but for
storm threats Tuesday night, CAMs appear to be locking on to an
idea that we will be watching for storm development in central
Nebraska late Tuesday afternoon which could then evolve into one
or more linear clusters which could bring a damaging wind threat
to our area during the mid evening to early overnight. Storm
track still varies wildly between the various model solutions,
but general transformation and depiction of northeastward-moving
bowing segments is fairly consistent.

The only other notable change in the next few days is the
continued eastward shift in the severe threat for Wednesday
afternoon. While timing of the cold front/residual boundaries
and associated location of storm development is uncertain,
the severe outlook for Wednesday has shifted the risk area in
our CWA eastward, with a Level 2 of 5 primarily east of Highway
59 and Level 1 of 5 east of the I-29 corridor. The risk in our
area should be fairly short-lived, with only a few hours between
peak heating/storm development and the cold front pushing east
of Highway 71 before sunset.

&&

.DISCUSSION...
Issued at 247 PM CDT Sun Jun 7 2026

A weak upper level low has pushed into the area this afternoon. This
low is encountering a less stable environment characterized by
instability values around 1000 J/kg of MLCAPE. Deep layer shear will
be quite weak on the order of 10-15 knots. Thus, severe storms are
not expected. Lightning, brief heavy rain, small hail, and gusty
winds up to 30-40 mph are the main hazards. Should see storm chances
diminish this evening as the boundary layer stabilizes. A second
round of showers and some storms remains possible late this evening
an night. These storms will be from a weakening MCS and could clip
locations near and north of highway-14. Should these storms make it
into the forecast area, they will be elevated and not severe given
weak vertical shear in the area.

The previously mentioned weak upper level wave will push northeast
of the forecast area on Monday. This will promote subsidence on its
back side. The morning hours look to be dry while high temperatures
warm to the upper 80s to low 90s by the afternoon. A cold front will
be pushing into the area from the west. This front looks to push
into locations west of the James River tomorrow. This front looks to
serve as a potential trigger for thunderstorms. Questions remain
about this potential though due to capping. Mid level lapse rates
look to exceed 8.0 C/km aloft while forcing for ascent remains weak
to . This will result in a cap right over the front. Latest
REFS shows an ensemble average about about a -60J/kg cap right over
the front. Individual members of the REFS show a variable cap with
some members showing a stronger cap and others showing little to no
cap. Latest HRRR, RRFS, and some of the newer MPAS models do show
convection developing along the front. Thus, confidence is higher in
convection developing than not at this time. Storms look to fire
along the front west of I-29. If the front can progress eastwards
enough, locations west of I-29 but along and east of the James River
may be where most of the storms develop. As of now, these storms
look to be isolated in coverage in an environment characterized by
2,000+ J/kg and effective shear values up to 35-40 knots. This looks
to support multi-cells to potentially supercells capable of large
hail up to golf ball size and damaging winds to 65 mph. Hodographs
are generally straight which would support splitting storms. Larger
hail can be achieved in a left split storm. Some disagreement
remains about an MCS that looks to develop across western Nebraska.
Tough to say how this MCS may track as the latest hi-res guidance is
split on whether this MCS pushes into the forecast area or stays
south along I-80. Will keep an eye on this potential.

Severe storm chances persist through the middle of the week,
beginning on Tuesday. A stronger upper level wave will begin to
eject into the Northern Plains on Tuesday, sending shortwave troughs
out ahead of it. Before storm chances occur, Tuesday will be a hot
day with high temperatures soaring to the 90s to up to about
100F.The ensembles continue to support this as they show a 40-90%
chance for high temperatures to exceed 90F. Dew points will remain
moist in the 60s to even 70s will result decently humid conditions.
A Heat Advisory may be needed for Tuesday as heat indices rise to
near to just above 100F. A second cold front will be working its way
through the Northern Plains on Tuesday, serving as the trigger for
convection. The best forcing for ascent looks to be to the north and
west of the forecast area with the previously mentioned shortwaves.
This seems to be somewhat supported by the RRFS, MPAS-RN model, and
the NAM12km as they show the bulk of the convection in this area.
Despite this, the cold front will be draped across a large portion
of the Northern and Central Plains. So convection may still develop
in or near the forecast area. Tough to say at this time but the
environment supports severe storms should they develop.

Wednesday will also see another chance for strong to severe storms.
The main wave and associated exit region of an upper level jet will
push into the Northern Plains. Despite these favorable features
being in place, questions remain regarding how quickly the
previously mentioned cold front will progress. If the front were to
progress at a faster rate of speed, then severe storm chances could
be lowered if the front is able to push east of the forecast area
before convection develops. If the fronts speed is slower, then
convection could develop on the front in the forecast area. Latest
medium range guidance and ML guidance is in agreement in the front
pushing through the area more quickly. While these trends are
looking better, can`t say for sure that they will continue. If the
front were to slow down and allow convection to develop in the area,
then a line of storm could develop before racing east of the area.
Will keep an eye on the front`s trends over the coming days. Aside
from storm chances, Wednesday will be another hot, although slightly
cooler day with highs warming to the mid 80s to 90s, warmest along
and east of the James River. Similar probabilities remain in the
ensembles of a 40-80% chance for highs to exceed 90F. Slightly lower
dew points look to keep heat indices a little lower, down to the
90s. That said, both Tuesday and Wednesday will see moderate to
major heat risk.

The rest of the week and weekend looks to see a return to near to
slightly above seasonable temperatures with highs lowering to the
70s and 80s. Broad troughing over the northern CONUS could keep rain
chances (20-30%) in the forecast for this period of time. Latest AI
guidance suggests that any chance for severe storms will remain at
15% or less into early next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 640 AM CDT Mon Jun 8 2026

Widespread IFR-MVFR ceilings persist through much of the morning
with gradual improvement to low-end MVFR through the afternoon.
There is a low chance of showers/storms developing 20Z-02Z, but
confidence is too low to include a mention in TAFs at this time.

&&

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

&&

$$

UPDATE...JH
DISCUSSION...Meyers
AVIATION...JH