632
FXUS63 KFSD 110835
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
335 AM CDT Fri Sep 11 2026

.KEY MESSAGES...

- Breezy to strong southerly winds are expected today with
  gusts between 30-40 mph expected for most areas. Slightly
  stronger winds will be possible across the Buffalo Ridge in
  southwestern MN.

- A conditional chance for stronger storms is expected this
  afternoon and evening mainly east of I-29. While all hazards
  remain possible, 2 inch hail and damaging winds up to 70 mph
  will be the primary threats.

- A pattern shift will lead to cooler conditions over the
  weekend with highs mainly in upper 60s to 70s. Periodic rain
  chances will continue into the new week.

&&

.UPDATE...
Issued at 330 AM CDT Fri Sep 11 2026

Not many significant changes on the weather front with the main
focus being on the breezy to strong winds today and the potential
for severe weather this afternoon/evening. Starting with the winds,
southerly surface winds should increase just after daybreak as the
surface pressure gradient tightens ahead of an approaching cold
front. This will lead to wind gusts recurringly in the 30-40 mph
range for most areas throughout the day. Still thinking that a
pocket of stronger winds (40-50 mph) will develop along the eastern
side of Coteau Des Prairies as mixing deepens and the 850mb to 925mb
LLJ strengthens. With this being further agreed upon by short-range
guidance, decided to pull the trigger on a Wind Advisory from 7 am
to 7 pm on the Buffalo Ridge in southwestern MN. Should see surface
winds gradually weaken after the front progresses through the area
this evening.

Otherwise, the focus continues to be on the severe weather chances
for the second half of the day. Still thinking our chances for
anything stronger will be conditionally dependent on if we can break
through the weakening cap. With diurnal heating, the best chances
will likely occur be between 5pm to 10pm mainly east of I-29. IF
this occurs, isolated to scattered updrafts could quickly become
severe with access to between 1500-2000 J/kg of CAPE and 30-40 kts
of bulk shear. While all hazards will be possible, steep mid-level
lapse rates and inverted "V" sounding profiles will favor up to 2
inch hail and damaging wind gusts up to 70 mph. Though confidence is
low, if a discrete supercell can anchor to the surface front; an
isolated tornado can`t rule out. Lastly, should see most of this
activity exit our area around midnight with the cold frontal
passage.

&&

.DISCUSSION...
Issued at 145 PM CDT Thu Sep 10 2026

This afternoon will be dry and breezy with gusts 25-35 mph, mostly
clear skies, and highs in the upper 70s to 80s. Dew points will be
lower this afternoon at around 60 or less. Overall a pleasant day is
in store. Overnight lows will be in the mid to upper 60s with the
breezy winds continuing into Friday.

Friday will be another warm day with highs in the 80s for most of
the CWA, and the low 90s west of the James River Valley. Throughout
the day a narrow plume of Theta-E air will advect in from the south,
along and east of Highway 81. Instability will increase along and
east of the plume with MUCAPE values climbing to 1500-2000 J/kg.
Modest mid-level lapse rates around 7+ deg C/km will align well with
the plume of instability. Bulk shear will be 35-40 kts. With
clockwise curved hodographs this set up is marginal to slightly
favorable for all modes of severe weather. This is also outlined in
the SPC Day 2 outlook with a Slight Risk (level 2 of 5) for severe
weather. However, a few items of uncertainty keep confidence in
convection initiation and coverage low. Probably the most important
factor is despite the moisture advection model soundings remain
dry through most of the column for areas west of I-29. Forcing
is on the strong side in the form of the upper trough and
surface low/cold front, but without moisture not much is going
to happen besides some cumulus clouds. East of I-29 moisture
return flow is better, however the environment will be strongly
capped. As the whole system progresses east through the evening
and into the overnight the airmass slowly saturates. But by
this point the forcing should be along our eastern CWA border
if not into central Iowa. In this scenario we will get very
little if any convection. This is the most likely scenario at
this time.

The other scenario is the better moisture return drifts farther
west. Then as the system passes through we could see saturation
occur sooner, and thus convection begin earlier east of Highway 81
between 4 and 7 pm, and along and east of the I-29 corridor
roughly between 7 pm and 10 pm. Storms would track east and be
out of the CWA roughly between midnight and 3 am Saturday. The
final scenario is we are able to lift off the 850-700 mb layer
and scattered strong to severe storms could develop. All this to
say a very conditional environment will be in place with risks
for large hail and damaging wind gusts. Though the risk is low, a
tornado cannot be ruled out.

Behind the cold front overnight lows will cool into the 50s and low
60s over northwest Iowa. Through the morning hours a few
isolated elevated showers are possible. Winds will become
northerly and light during the day. Mid-level temperatures will
fall into the teens C and at the surface highs will be slightly
below average for this time of year, in the low 70s north of
I-90 and the mid to upper 70s to the south. Much drier air will
advect in from the north bringing dew points down to the 40s to
mid 50s. Saturday will be a pleasant taste of fall.

Early Sunday morning the flow aloft becomes mostly zonal and high
pressure builds in at the surface. Modest moisture return on
southeast winds and WAA ahead of an approaching low amplitude wave
may be enough to trigger light scattered showers and thunderstorms
by the late morning to early afternoon. These are not expected to be
severe but could bring rain to a larger portion of the region.
Sunday evening into the overnight a strong upper trough swings
through northwest of the region. An associated surface low ejects
out of Colorado onto the central Plains and accelerates northeast
into our CWA. Though many details are unclear at this time, some
storms could be strong to severe Sunday night into Monday morning.
Storms may linger into the afternoon.

Northwest flow aloft is expected for the first half of next week. At
the surface highs will be closer to seasonal averages, in the 70s.
Another round of storms is possible mid-week.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1037 PM CDT Thu Sep 10 2026

VFR through the period. Breezy southerly winds through the
period with some gusts of 35 to 40 mph likely during the day
Friday. A few early morning ACCAS showers will be possible
Friday morning, but confidence is low. A strong to severe storm
will be possible after about 22z Friday, but confidence is low
and any storms that may develop should remain very isolated. The
better chances will be near and east of I-29.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...Wind Advisory from 7 AM this morning to 7 PM CDT this evening
     for MNZ071-072-080-081-089-090-097.
IA...None.
NE...None.

&&

$$

UPDATE...05
DISCUSSION...AJP
AVIATION...08