Severe Thunderstorm Warning 110, NWS Sioux Falls, SD

Area Forecast Discussion
National Weather Service Sioux Falls SD
858 PM CDT Tue Jun 9 2026

.KEY MESSAGES...

- A potentially significant severe weather threat is currently
  developing. Initial storms bring a large hail threat toward
  central South Dakota and Nebraska in the evening,
  transitioning to damaging winds potentially in excess of 80
  mph farther east into the night. Isolated tornadoes are
  possible.

- The main timing for strong to severe storms is between 9 pm
  and 3 am tonight. The peak window for 80+ mph wind gusts is 10
  pm to 2 am. These kinds of winds could produce tornado-like
  damage, so make sure to have multiple ways of receiving
  weather alerts that can also wake you up in the middle of the
  night!

- The threat for severe weather continues to trend east of the
  area Wednesday afternoon. However, can't rule out a stronger
  storm near and south of Highway 20 early Thursday morning,
  though uncertainty of severe potential remains high.

&&

.UPDATE...
Issued at 856 PM CDT Tue Jun 9 2026

Thunderstorms have developed across southern Nebraska, western into
central South Dakota, and central North dakota. These storms are
beginning to grow upscale, mainly across the Dakotas this evening.
Am expecting this line of storms to continue to push east/northeast
as the storms should follow close to the mean wind and storm motion
vectors. Another round of storms has developed across southern and
central Nebraska. These storms are more discrete than the storms in
the Dakotas but pone storm in southern Nebraska has produced very
strong winds with it, with a peak gust up to about 85 mph. This
storm has produced an outflow boundary that new convection is
developing on. Think the new convection that can be generated on the
outflow boundary could merge into the western line of storms. Thus,
it still looks like a line of storms will move through the area
tonight. If cells can remain semi-discrete perhaps on the southern
end of the line or a new cell develops just ahead of the line, then
large hail up to 2 inches or larger is possible. 0-7km theta-e
difference values down to about -25K and 0-10 km shear values up to
45 to 50 knots will support a severe line of storms with damaging
winds up to 80+ mph winds. The low level jet (LLJ) is expected to
strengthen up to about 40 knots this evening and night. The LLJ will
expand low level hodographs and increase low level shear profiles. 0-
3 km shear will strengthen up to about 30 knots and be oriented
mainly perpendicularly to the line, thus supporting the chance for a
few tornadoes. These storms will push through the area beginning
after 02z and persist through 07z to 08z before they finally push
through the area.

The cold front responsible for these storms remains on track to
quickly race eastwards through the area tomorrow. The bulk of any
new severe storms that develop on or ahead of this boundary look to
be to the east of our area. A few elevated storms are possible
behind this boundary Wednesday afternoon and evening though these
storms are not expected to be severe. Wednesday will remain a hot
day despite the front coming through with highs warming to the 80s
and 90s, hottest east of I-29. There could be another round of
strong to severe storms late Wednesday night into Thursday morning.
Where these storms may form is a bit uncertain but for now it's
looking to be near or south of highway-20. Pattern recognition
suggests that these storms could develop due to gravity waves. Since
these storms will be elevated large hail and damaging winds will be
the primary hazard.

&&

.DISCUSSION...
Issued at 315 PM CDT Tue Jun 9 2026

A hot and humid day continues across the area as temperatures have
soared into the 90s with heat indices in the middle 90s so far,
though starting to see some spots into the upper 90s to around
100 in parts of northwest Iowa. The Heat Advisory remains in
effect until 9 pm for areas near and south of I-90, so continue
to stay hydrated out there! Seeing some areas of CU develop
across the area this afternoon, and with plenty of instability
in place and the heat eroding the cap, can't rule out a stray
shower or thunderstorm through the afternoon. The 09.12Z REFS
ensemble is the most excited about this as it shows 20-40%
chance of hourly measurable precipitation this afternoon over
southwest Minnesota, but this remains an outlier and so the
official forecast calls for a less than 15% chance of rain as
there won't be much upper level support to get storms going. But
if a storm is able to develop, then large hail up to ping pong
ball in size will be possible given steep mid level lapse rates
and effective bulk shear on the order of 40-45 kts.

A potentially significant severe weather threat is in store for the
area tonight. A negatively tilted trough will move into the northern
Plains tonight as a cool front approaches the area. Ahead of this, a
highly unstable atmosphere will be in place, with guidance showing
2,500-3,500 J/kg of CAPE available despite the loss of daytime
heating. Two areas of storms look to develop late this afternoon,
one over western South Dakota and one over central Nebraska. The
first area will lift mainly northeast of the area through this
evening, but could clip the Highway-14 corridor near and west of the
James River. Most of the 09.12Z guidance kept the greater chances
north of the area, though some of the latest HRRR runs have trended
a bit farther south. If this were to clip our area, look for this to
happen between 10 pm and 1 am. Damaging winds to 70 mph would be the
main threat with this activity, though large hail up to golf ball in
size will be possible as well. Can't rule out a tornado given the
low level curvature of the hodographs, but storms will likely be
becoming more elevated with time through the evening, diminishing
the tornado threat, but not reducing it to zero as storms move
through.

The second area to watch that develops over central
Nebraska has the better chance of becoming the "main show" so to
speak regarding the severe weather threat. Storms that develop in
this area will quickly lift north-northeast and form into a line or
a couple of linear clusters as they quickly swing through the area.
This activity will likely cross the Missouri River around 10 to 11
pm, move across the I-90 corridor around midnight, and exits out of
our southwest Minnesota and northern Iowa counties by 2 to 3 am.
Guidance continues to be consistent in bringing in the strongest
winds with this activity, likely owing to the greater instability.
This is where we could see gusts as high as 80 mph or slightly
higher, bringing the potential for destructive straight-line winds.
Not expecting widespread 80+ mph gusts given the weaker shear, but
widespread 40-60 mph winds look likely depending on how many
individual clusters end up developing. Mid level lapse rates
will be around 7.5-8 C/km and large CAPE profiles will also
promote hail potentially to the size of 2 inches or slightly
larger as the storms cross the Missouri and are more isolated,
and then up to golf ball in size as storms turn more linear.
Guidance shows the better south- southwesterly low level jet of
up to 40-45 kts developing south of I- 90 and into northwest
Iowa and far northeast Nebraska, so will have to watch for a
tornado or two, though the elevated nature of the storms will
tend to limit this threat overall.

Some limiting factors other then the weaker bulk shear than compared
to areas to our north, will be the fact that some soundings,
particularly the 09.12Z NAM, show a warm layer around 750 mb that
could limit some storms from forming. The warm layer is fairly
shallow though, but still could put a stop to at least some of the
storms developing. Even with this, that warm layer does erode on
that NAM run over northwest Iowa, so storms still go off there
if this run ends up coming to fruition. But still, if that warm
layer ends up being stronger than expected, this could put a
dent into thunderstorm chances. Either way, be sure to remain
weather aware tonight and make sure to have multiple ways of
receiving alerts that can also wake you up in the middle of the
night. Also keep in mind that if any storm produces 80+ mph
straight line winds, this could do similar damage to tornadoes,
so know where your tornado safe place is even though the tornado
threat is low.

Not much time to look into the forecast after tonight's event, but
the severe weather threat continues to trend farther east for
Wednesday afternoon due most guidance moving the cool front east of
the area by peak daytime heating. Will have to watch early Thursday
morning as the main wave moves through as around 50-60+ kts of bulk
shear develops with this. Current indications is that the best
instability will be pushed south of the area as this wave moves
through, but folks near and south of Highway 20 will need to stay up
to date with the latest forecast in case greater instability trends
north. Otherwise, look for generally cooler temperatures heading
into early next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 620 PM CDT Tue Jun 9 2026

Mainly VFR conditions with occasional MVFR to IFR conditions
will be possible this TAF period. Taking a look at satellite
imagery, mostly clear conditions continue this evening as a
"Cue" field begins to build across the Missouri River Valley.
Should see the quieter conditions continue over the next few
hours before scattered showers and thunderstorms progress across
the area this evening. Decided to continue the trend of adding
TEMPO groups in for both KFSD & KHON since that is where we're
most confident. However, decided to also add in PROB30 group
into KSUX with the potential for lingering showers to move
through that area. Otherwise, breezy southerly winds will
continue well into the overnight hours before westerly winds
return by late Wednesday morning

&&

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

&&

UPDATE...Meyers
DISCUSSION...Samet
AVIATION...05

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
358 AM CDT Tue Jun 9 2026

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ038>040-050-052>071-100900-
Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee-
Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson-
Pipestone-Rock-Dixon-Dakota-Beadle-Kingsbury-Brookings-Gregory-
Jerauld-Sanborn-Miner-Lake-Moody-Brule-Aurora-Davison-Hanson-McCook-
Minnehaha-Charles Mix-Douglas-Hutchinson-Turner-Bon Homme-Yankton-
Union-
358 AM CDT Tue Jun 9 2026

This Hazardous Weather Outlook is for northwest Iowa, west central
Iowa, southwest Minnesota, northeast Nebraska, central South
Dakota, east central South Dakota, south central South Dakota and
southeast South Dakota.

.DAY ONE...Today and tonight.

Temperatures climb into the 90s to near 100 degrees today, with heat
indices peaking from 95 to 105 degrees. Stay in air-conditioning and
out of the sun if possible, drink plenty of water and take breaks in
a cool location if working outdoors.

Scattered strong to severe storms develop toward central South Dakota
and Nebraska by late afternoon to early evening. These storms will
evolve into clusters as they track eastward this evening and
overnight. All severe weather hazards are possible tonight. Stay
weather aware and be prepared to seek shelter when storms approach.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Isolated stronger storms may impact portions of northwest Iowa
Wednesday afternoon, though the exact location of storm development
will depend on timing of a cold front moving through the region.
Large hail and damaging winds would be the primary threats.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed tonight from
7 pm to midnight for southeast South Dakota, and from
11 pm to 3 am for southwest Minnesota and northwest Iowa.

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Preliminary Local Storm Report
National Weather Service Sioux Falls SD
1115 PM CDT Tue Jun 9 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1106 PM     Tstm Wnd Gst     7 W Armour              43.32N 98.48W
06/09/2026  M73 MPH          Douglas            SD   Public

            A personal weather station near Armour
            reported a 73 mph wind gust.

&&

IG