610
FXUS63 KFSD 071142
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
642 AM CDT Sun Jun 7 2026

.KEY MESSAGES...

- Scattered non-severe storms are expected near and east of I-29
  today.

- Conditional severe risks west of Highway 281 late tonight and
  west of I-29 Monday afternoon. Confidence in storm development
  is low (20-30%), but if storms develop, damaging winds and
  large hail would be the primary threats.

- Temperatures heat up through mid-week. There is a moderate
  chance (40-90%) of highs exceeding 90F Tuesday and Wednesday,
  with the highest probabilities coming on Tuesday. Be prepared
  to enact any heat related safety measures.

- Severe storm chances look to make a return to the region on
  Tuesday and Wednesday. Details remain uncertain so continue
  to keep up to date with the latest forecast for the most up to
  date information.

&&

.UPDATE...
Issued at 510 AM CDT Sun Jun 7 2026

An isolated shower/weak storm has developed at the leading edge
of strong Theta-E/moisture advection early this morning, with
low chances lingering mainly in southwest Minnesota until
shortly after sunrise. Expect greater coverage of showers/storms
to develop near and east of I-29 this afternoon/evening as a mid
to upper level wave slides north across the area. Increasing
cloud cover will limit instability and storms will have very
little shear to support organized development, so severe weather
is not expected.

Will still have to watch storms which develop well to our west
later today, as still a low (20-30%) chance that this activity
could drift into our far western zones after midnight tonight.
These storms should be weakening as they progress east into a
less unstable air mass, but will need to monitor trends as more
aggressive CAMs do still indicate an isolated strong to severe
potential.

Monday should generally see storm potential suppressed with
rising mid-upper level heights in the wake of the early morning
wave. However, a low level thermal ridge noses into our South
Dakota counties by afternoon and if temperatures should warm
enough to break through a capping inversion, steep mid-level
lapse rates could support an isolated large hail threat in the
late afternoon-evening.

A more potent mid-upper level trough swings through the northern
Plains Tuesday-Wednesday, but as alluded to in the previous
discussion, the greater threats for severe weather appear to be
focused to our north Tuesday-Tuesday night, and to our east on
Wednesday. This is supported by the latest Day 3/4 SPC outlooks
which have introduced an Enhanced (Level 3 of 5) risk in North
Dakota/north-central South Dakota on Tuesday, with a 30% Day 4
risk farther east in the Upper Mississippi Valley for Wednesday.
Details for our area are still rather low confidence. The heat
dome that is expected to build into the area on Tuesday should
limit daytime development, but a wave sliding northeast by late
afternoon/early evening could trigger development. Instability
and shear would be supportive of strong to severe storms, it`s
mainly timing/coverage of development that is lower confidence
at this time.

For Wednesday, there is still some disagreement in regard to
timing of the cold front, but some models have trended slightly
faster with the cold front. Not only would this bring greater
relief from the heat/humidity across our western counties, but
it could also shift the severe risk farther east as indicated in
the latest SPC outlook. Again, this leads to lower confidence in
potential severe timing and coverage for Wednesday afternoon,
but even the slower models would push the risk of storms east of
our CWA by early evening.

&&

.DISCUSSION...
Issued at 204 PM CDT Sat Jun 6 2026

Quiet conditions persist this afternoon along with high temperatures
that have warmed to 80s to low 90s. A weak upper level low currently
spinning over the southern Plains will begin to advect northwards
this afternoon. The main forcing from this wave will remain south of
the forecast area today but could see an isolated shower or storm
develop near and south of highway-20 this afternoon and evening.
Deep layer shear will be weak at 10 knots or less so severe storms
are not expected. Low temperatures will fall to the 60s overnight.
Moistening dew points overnight could result in some patchy fog
across the area, most likely in river valley`s.

The weak upper level wave will advect northwards on Sunday. This
wave will result in an increase in cloud cover and slightly cooler
high temperatures across the area. High temperatures look to warm to
the 80s to touching 90F toward central South Dakota. Depending on
how thick the cloud cover gets and the timing of rain with it, some
locations may see high temperatures remain in the upper 70s. Chances
(20-60%) for showers and storms will return with this wave tomorrow
afternoon and evening. As of now, the bulk of the showers and storms
look to track northwards for locations along and east of I-29.
Instability will be sufficient at or above 1,000 J/kg. However, deep
layer shear will remain weak at 10 knots or less. Thus, severe
weather is not expected. Given the more scattered nature of the
storms, rainfall amounts are not expected to be much with most
locations receiving a a few hundredths to a tenth or two of an inch.
Isolated higher amounts are possible where storms track over the
same area. Chances for rain will be waning through the evening hours
as the boundary layer begins to stabilize, preventing and deeper
mixing from initiating new storms. There could be a second round of
storms that may track eastwards into the area from the western
Dakota`s Sunday night. As of now, think that this second round of
storms will mainly stay off to the north and west of the forecast
area where the better vertical shear will lie. If these storms were
to hold together as they push into the area, they will likely be on
a weakening trend due to the weak vertical shear in place. Perhaps
gusty winds could accompany the storms before they completely die
out.

Monday looks to be quiet during the daylight hours as the wave
responsible for Sunday`s storms lifts into Canada. There could be
another round of showers and storms Monday evening but this will be
dependent on if the cap can be broken. Latest ensembles show
relatively high probabilities between 40-80% that the cap remains
stronger (more negative) than -25 J/kg. Tough to say if temperatures
could warm enough to overcome the cap let alone reach convective
temperatures. If the cap could be broken, then low end severe storms
would be possible as vertical shear begins to strengthen aloft. If
the cap remains strong, then no storms and little rain would be on
the table. Something to keep an eye on going forward.

Attention then turns to Tuesday and Wednesday of next week. Medium
range guidance is in agreement in a strong, longer-wave upper level
trough digging into the Northern Plains during this period of time.
Before diving into storm chances, high temperatures look to be hot
across the area with highs warming into the 90s and potentially
touching 100F to 101F on Tuesday. The ensembles support this as they
show moderate to high probabilities (50-90%) for high temperatures
to exceed 90F on Tuesday. These same probabilities drop a bit
to a 40- 70% chance on Wednesday. These hot temperatures will
coincide with more humid conditions as dew points moisten to the
60s and 70s. The hot and humid conditions will result in areas
of moderate to major heat risk. If you will be out and about on
either of these days, please follow the necessary safety precautions
to stay safe in the heat.

Thunderstorms look to persist across the area as the upper level
wave begins to eject into the Northern Plains on Tuesday. With
southwest flow over the Rockies, lee cyclogenesis will occur,
tightening low level pressure gradients and strengthening the low
level jet (LLJ). This will increase vertical shear profiles across
the region. Instability will be more than sufficient with the
previously mentioned hot and humid conditions in place. Thus, strong
to severe storms will be possible. As of now, Tuesday evening and
night looks to be the main time period for severe weather due to the
strengthening LLJ. The main wave finally ejects on Wednesday,
continuing severe storm chances. If current model trends hold,
Wednesday could see the strongest storms between both days as an
exit region of an upper jet looks to push into the Northern Plains.
While the deterministic models, ensembles, and clusters support this
exit region, details about how this wave tracks remain a bit
uncertain. Mesoscale details are also much more uncertain this far
out. Especially considering that Wednesday`s storm potential will be
dependent on how Tuesday`s storms pan out. Latest machine learning
(ML) models give a little bit more clarity into this potential.
Currently, the bulk of the ML models have the highest chances for
severe storms in North Dakota on Tuesday and then across parts of
Minnesota, Wisconsin, and Iowa on Wednesday. Details can still
change over the next couple of days but continue to monitor the
latest forecast for the most up to date information.

Chances for rain could persist through the rest of the week but this
will depend on how the upper level wave evolves and if low level
moisture gets pushed south of the area. High temperatures look to
fall back closer to seasonable in the upper 70s to 80s.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 637 AM CDT Sun Jun 7 2026

VFR conditions to start the period will deteriorate from south
to north, especially along and east of the I-29 corridor as
areas of light rain with embedded thunderstorms lift north out
of Iowa. Confidence is slightly higher that KSUX could see an
occasional thunderstorm in the late afternoon/early evening so
will continue a TSRA mention there. Lower confidence at KFSD at
this time, so have shifted this back to -SHRA for now. Cannot
rule out brief thunder, but feel most of the period should be
thunder-free.

MVFR-IFR ceilings are expected to persist near/east of I-29
through the latter half of the TAF period while areas west of
I-29 favor VFR conditions. A low chance that showers/storms
could reach KHON late in the period, but again, confidence is
too low to include TS in the KHON TAF at this time.

&&

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

&&

$$

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