088
FXUS63 KFSD 090854
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
354 AM CDT Sun Aug 9 2026

.KEY MESSAGES...

- Thunderstorm risks continue into the morning hours with some
  focus along or north of Highway 14, and northwest Iowa after
  midnight. Marginal hail and 70 mph winds would be the main
  risks any any storm.

- Late Sunday evening into Monday could be a focus point for
  strong to severe convection in western into central South
  Dakota. While uncertain, one or two clusters of severe storms
  may develop.

- Nearly daily precipitation risks will continue well into next
  week, however chances remain low due to the high uncertainty
  in the forecast.

&&

.UPDATE...
Issued at 352 AM CDT Sun Aug 9 2026

Taking a look across the area, our focus continues to sit near the
ND/SD border this morning as a few stronger have developed mainly in
response to a lingering warm front and a weak short wave. Over the
course of the morning, expect this activity to gradually congeal and
dive southeastwards into our area over the next several hours (3am-
8am). As this developing activity becomes more outflow dominant
should see the damaging wind threat increase with the potential for
up to 70 mph wind gusts possible. Until that time, the initial semi-
discrete cells will carry a marginally large hail threat with
up to quarter possible with decent mid-level lapse rates. While
the CAMs continue to struggle with the the evolution of this
activity, current trends continue to favor the HiresW-ARW which
has the most consistent placement with current radar imagery.
With this in mind, current thoughts are things will continue to
follow the 850mb moisture/thermal gradient down a Huron to Sioux
Falls to Storm Lake, IA line with most of the activity
northeast of this line.

Should see most of this activity exit the region by 7am to 8am.
Otherwise, quieter conditions should return to the area afterwards
with highs peaking in the upper 70s to upper 80s by early afternoon.
With more humid conditions expected (60s to low 70s dew points),
heat index values will approach the low to upper 90s in areas along
and south of I-90 with the highest values concentrated along the
Missouri River Valley. While this falls just short of advisory
criteria, make sure to stay hydrated as lighter surface winds won`t
provide much relief from the oppressive conditions. Lastly, with an
active pattern aloft; can`t rule out additional showers and
thunderstorms overnight into Monday morning. Nonetheless, most
guidance continues to handle coverage and evolution poorly so
hopefully future model runs can provide some clarity moving
forward.

&&

.DISCUSSION...
Issued at 123 PM CDT Sat Aug 8 2026

THIS AFTERNOON: We`re continuing to watch a slowly northeastward
advancing mid-lvl cloud deck early this afternoon. This cloud layer
marks the advancing edge of moisture (and instability) advecting
within the 850:700 mb layer. A parcel lifted from this level still
appears to be fighting a bit of inhibition, which will keep only
very low PoPs in the forecast as this moves northeast.  Elsewhere,
wildfire smoke aloft remains quite thick, and may have slight
impacts on high temperatures this afternoon.

TONIGHT: The forecast remains somewhat uncertain this evening and
overnight, though there are at least better signals for where
convection may form after dark today. Latest short term guidance
points to two distinct areas of focus. One near the SD/ND border
into west central Minnesota where current AC field ends up by
sunset.   The initiation of at least a 25 to 35 knot LLJ should be
enough to develop a few storms.  It`s possible that a minor
shortwave could also drop southeast after midnight helping push this
activity towards Highway 14 and SW Minnesota by daybreak. A second
area to watch will be northwest and north central Iowa where
slightly stronger LLJ convergence develops. Any activity that forms
should pass along the far eastern CWA by 12Z.  Realistic MUCAPE
between 1500-2000 J/KG with 20-25 knots of shear may produce a few
stronger storms with large hail.

SUNDAY: A continued uncertain forecast remains for Sunday. Morning
convection should weaken by mid-morning as the LLJ weakens and any
activity pushes east of the CWA.  In it`s wake, there remains no
strong triggering mechanisms for any convection further west and low-
lvl and surface flow may turn more northeasterly by mid-day.
Nevertheless while we may see CAPE values push 2500-3000 J/KG, HREF
probabilities of less than 100 J/KG CIN remain only around 25%,
suggesting that surface based convection may be hard to come by.
Wildfire smoke will again be quite thick on Sunday, and have lowered
temperatures a degree or two. Though the ongoing drought may also
counter act some of those limiting effects.

SUNDAY NIGHT: Slightly increased PoPs arrive late Sunday evening
into Monday as there seems to be some mid-lvl vorticity moving
through the region. While highly uncertain on the track, this could
at least pose some risks for stronger convection forming early in
the evening in western SD/ND on the nose of an increasing LLJ. This
convection will be initially surface based and capable of very
large hail. There are some hints that these storms could congeal
and begin to produce a bit more wind as they reach central SD.
The limiting factor in the eastward progression could be a very
dry sub 600 mb layer as these storms reach the James River
valley.

MONDAY-WEDNESDAY: The first half of the week continues to look very
uncertain given the quasi-zonal or slightly northwest flow pattern
aloft.  It`s certainly possible one or more of these days will
feature a rain chance, but these are all dependent on any weak eddy
in the flow. There continues to be some consistency again today on
one of these waves arriving Monday evening into Tuesday and again
into Wednesday morning. The available instability would suggest
at least a continued low-risk for a severe storm or two, though
wind shear continues to be borderline. Temperatures remain near
their seasonal normals in the lower to middle 80s.

THURSDAY-FRIDAY: No changes in this portion of the forecast,
where mid-lvl flow flattens and becomes westerly. PoPs will be
elevated into Thursday as a cold front may pass through the
region. There continues to be growing signs of a slight cooldown
into the weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1258 AM CDT Sun Aug 9 2026

VFR conditions currently across the region. We are watching north
central South Dakota as strong to severe thunderstorms are moving
southeast. Risks with storms include wind gusts to 70 mph, heavy
rain, and hail up to the size of a quarter. While there remains some
uncertainty in storm evolution and track, storms look to grow
upscale into one or more bowing segments. At which point the main
threat will transition to winds and heavy rain. Storms look most
likely to impact along and northeast of a line from KHON and KFSD
and portions of northwest Iowa. IFR down to LIFR ceilings are
possible under stronger storms.

In addition, strong directional and speed shear are expected as the
surface low pressure tracks southeast with the system. The strongest
storms are expected to be east of the region shortly after 12Z
Sunday. Winds become northeasterly and increase on the backside of
the storms. Gusts of 15-20 kts are expected for areas along and east
of I-29. Lighter winds to the east. More chances for showers and
thunderstorms near the end of the period.

&&

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

&&

$$

UPDATE...05
DISCUSSION...Dux
AVIATION...AJP