062
FXUS63 KFSD 110533
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1233 AM CDT Thu Jun 11 2026

.KEY MESSAGES...

- Late tonight into early Thursday morning showers and
  thunderstorms are expected to develop across the region.
  Storms will move east through early afternoon Thursday.

- A few strong to severe storms may develop early Thursday
  morning (5-9 am). Wind gusts to 65 mph and hail up to ping
  pong ball size would be the main threats. These storms look to
  mainly track along I-80 but there remains the possibility
  that they could push up to and near the highway-20 corridor.

- Friday through the first half of next week will see cooler
  highs in the 70s to 80s and lower relative humidity values.

- Saturday will see a chance of thunderstorms over mainly
  northwest Iowa. At this time severe risk appears to be low.

&&

.UPDATE...
Issued at 924 PM CDT Wed Jun 10 2026

Quiet conditions continue across the area this evening. Convection
has developed on a cold front stretching all the way from northern
Minnesota down through Iowa, southeast Nebraska, and Kansas. This
current convection will push off to the east over the coming hours.
This boundary is not done yet though as another shortwave trough
currently over Wyoming will dive to the southeast. This mass
response to this wave will strengthen the low level jet (LLJ) and
begin to retreat this boundary northwards. This boundary will bring
much greater moisture and instability along and north of I-80 and
potentially reaching up to about highway-20 or so. Latest CAMs show
convection developing just ahead of this surface front initially.
With broad southwest to northeast flow in place, these new storms
will push off to the northeast while the front continues to return
northwards, allowing for a transition from elevated storms to
surface based storms to take place. A mesoscale convective system
(MCS) is possible. This environment will be characterized by large
buoyancy with instability values up to around 3,000 J/kg and
effective shear values potentially up to about 80 knots. This
environment will be conducive for large hail up to ping pong ball
size and damaging winds to 65 mph. The main uncertainty regarding
these storms is precisely where they will track. Latest hi-res
guidance is in decent agreement that these storms will track near I-
80. However, there remains the potential that these storms could
reach up to about highway-20 late tonight into early tomorrow
morning, roughly between 5 am to 9 am. Do think that the hi-res
models are in the right ball park with the severe storms staying
just south of the forecast area. Trends will be monitored through
the night as a shift back to the north is possible.

Thursday will be a cooler day with high temperatures remaining in
the 70s as stratiform rain will overspread the area for most of the
morning hours before exiting the forecast area during the afternoon
timeframe. A stray shower or two is possible for the rest of the
afternoon timeframe. Rainfall amounts look to be light with amounts
between a few hundredths to a tenth or two. Rainfall amounts that
could exceed a quarter of an inch will be associated with weak
thundershowers that may develop within the overall stratiform rain
area. Winds remain on track to strengthen behind the departing
system with gusts up to 30-40 mph. The strongest winds look to occur
west of I-29, especially over central and south central South Dakota.

Friday continues to look dry with highs warming back to the 80s to
low 90s. The next chance for showers and storms looks to return on
Saturday, with the highest chances (20-40%) across parts of northwest
Iowa.

&&

.DISCUSSION...
Issued at 147 PM CDT Wed Jun 10 2026

A cold front draped from central Canada south through the central
Plains will gradually make its way east through the afternoon today.
To the east of the front an influx of moisture advection will work
to destabilize the atmosphere. As the upper wave passes over the
cold front it will work as a focus for shower and thunderstorm
initiation. Short term guidance is in fairly good agreement that any
stronger storms will be well east of the region into central Iowa
this afternoon and evening, where the better dynamic setup is. One
thing to watch this afternoon is a band of vorticity advection and
enhanced stretching potential that could result in brief funnels
late this afternoon for areas along and east of Highway 60. If any
funnels form they should be weak and short lived.

Late Wednesday night into early Thursday morning an area of weak WWA
coupled with an increasing LLJ swings through central South Dakota.
This may trigger showers and thunderstorms. These storms will
progress northeast through early Thursday afternoon. Instability is
low, less than 500 J/kg, but could be enough for a few lightning
strikes. For areas north of Highway 18, severe weather is not
anticipated, however a few brief, heavy downpours are possible.
Around daybreak a surface low will move northeast out of central
Nebraska. Instability will rapidly increase ahead of the low as 0-6
km Bulk shear ramps up 70-75 kts. In addition, synoptic support in
the form of a jet streak right entrance region, a mid-level trough
axis, and continued intensification of the LLJ may work to focus
storms into a more organized area of supercells. These will
then quickly grow upscale into a mesoscale convective system
(MCS). There remains some uncertainty in the track of the low,
with most guidance keeping the initial stronger supercells just
to the south of our CWA. However, a few bring isolated strong
to severe supercells into our northeast Nebraska counties and
into northwest Iowa, mostly east of Highway 60. These stronger
storms will be capable of producing hail to ping-pong balls and
wind gusts of 65 mph. As the strongest storms are expected
during the morning commute, roughly 6 - 9 am, we will need to
monitor the trends. Any lingering showers and thunderstorms
should be east of the CWA by the early afternoon. Highs
Thursday afternoon will be cooler thanks to CAA behind the wave,
in the 70s.

Mostly zonal flow aloft and dry conditions are expected for Friday.
At the surface west winds become southerly through the day. A strong
push of WAA will warm afternoon highs in to the 80s and 90s. Friday
overnight a weak cold front pushes through the region, brining low
chances (<25%) of rain to areas along and north of Highway 14. As
the front progresses to the southeast there will be additional low
to medium chances (<40%) for light rain over portions of southeast
South Dakota, northeast Nebraska, and northwest Iowa from roughly
daybreak through the afternoon. Highs Saturday will be slightly
cooler in the upper 70s to mid-80s. Northwesterly flow in the mid-
levels keep cooler temperatures in the forecast for Sunday as well,
with highs in the low to mid 70s. This trend of 70s for highs
continues into the first half of next week. Dew points during this
time will also be lower, in the 40s to low 50s. If you have any
outdoor projects, this would be a great time to work on them without
the heat and humidity.

Monday night into Tuesday a strong upper wave will work through the
region bringing chances of rain to the area. Details on instability
and potential for strong storms are uncertain at this time.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1233 AM CDT Thu Jun 11 2026

VFR conditions begin the TAF period. Latest satellite shows mid and
upper level clouds beginning to expand into the area from the west.
The low levels remain dry but radar is beginning to pick up some
returns. Expect to see rain develop and become more widespread
through the overnight hours. Thunderstorms remain possible along and
south of highway-20 late tonight into tomorrow morning. Confidence
is still not high enough to include mention in KSUX`s TAF but trends
will be monitored. Rain will persist through the morning hours
before pushing east of the area by the mid afternoon timeframe.
Ceilings look to remain mainly VFR with visibilities dropping to
MVFR levels. Once the rain pushes east of the area, VFR conditions
will return to the area with winds strengthening out of the
northwest. Gusts up to 20-35 knots is expected for the back half of
the afternoon hours, strongest towards south central South Dakota.
The northwest winds will be weakening tomorrow evening to end the
TAF period.

&&

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

&&

$$

UPDATE...Meyers
DISCUSSION...AJP
AVIATION...Meyers