Severe Thunderstorm Warning 17, NWS Sioux Falls, SD

Area Forecast Discussion
National Weather Service Sioux Falls SD
641 PM CDT Mon Apr 13 2026

.KEY MESSAGES...

- Thunderstorms return this afternoon and evening. Scattered
  strong to severe storms expected - greatest risk for
  southwestern Minnesota into adjacent areas of South Dakota and
  northwest Iowa. Timing of greatest concern is 4 to 9 PM.

- Main hazards are large hail greater than 2 inches in diameter
  and wind gusts to 70 mph. A tornado or two are also possible.
  Have a severe weather plan and multiple ways to receive
  warnings.

- Periodic chances (20-60%) for showers and thunderstorms
  continue this week. Details remain uncertain at this time.

&&

.DISCUSSION...
Issued at 238 PM CDT Mon Apr 13 2026

Scattered thunderstorms are set to develop over the next
few hours, bringing the potential for a few severe storms with large
hail, damaging winds, and perhaps a tornado or two. As of 2 pm,
a surface low is located over northern Nebraska with a warm
front extending northeast of it across far southeastern South
Dakota into northwest Iowa. Dew points in the 60s have been
gradually spreading northward, and these higher dew points are
expected to reach the I-90 corridor over the next couple of
hours. This boundary will be the focus of initial storm
development, with these storms having access to 35-50 kts of
effective bulk shear and 1500-2000 J/kg of MLCAPE. There are
questions though on how much some high clouds have limited the
area from reaching full heating potential, but if a storm can
get going then steep mid level lapse rates of 7.5-8.5 degrees
C/km and mostly straight, elongated hodographs will favor large
hail to around 2 inches in diameter or larger. The secondary
threat will be damaging wind gusts up to 70 mph. If a storm can
get rooted to the aforementioned surface warm front, then a
tornado or two will also be possible. Can't rule out a strong
tornado either, primarily over southwest Minnesota. As the low
pressure system drift across the area, a few additional showers
and storms look to develop farther south across northwest Iowa
(down to about IA Highway-3, or just north of US Highway-20)
within the warm sector around sunset. These storms could also be
on the strong to severe side, with an isolated instance of
quarter sized hail and 60 mph as the threats.

Showers and storms will exit off to our east by the mid
evening hours, leaving mostly quiet conditions in its wake. A few
showers may develop in central South Dakota prior to daybreak
Tuesday, but dry air should win out and prevent most if not all of
this from reaching the ground. Patchy fog will also be possible
by early Tuesday morning across portions of northwest Iowa and
southwest Minnesota as winds turn light and variable overnight
and ample moisture remains in place. Temperatures tonight drop
mainly in the 40s, though some 50s are possible in our
easternmost areas. Low chances for showers continue into the day
on Tuesday, but activity is expected to remain spotty at best
as rain continues to battle a dry sub cloud layer. Highs will
range from the 60s northwest to 70s southeast. Rain chances look
to increase Tuesday night into Wednesday as two shortwave
troughs impact our area. The best chances of rain and storms
look to be over northwest Iowa and adjacent areas of Nebraska,
South Dakota, and Minnesota. At this time, severe weather looks
unlikely with this system as the better instability looks to be
off to our south and east.

Rain and storms exit off to our east by Wednesday night, leading to
a dry Thursday. Winds look to increase on Thursday especially west
of I-29 closer to a deepening surface low, and winds may take on a
southwesterly component especially in south central South Dakota.
This could lead to another day with higher fire danger as
temperatures will be warm and relative humidity values drop to 25%
or below mainly along and west of the James River. Still some
uncertainty into how breezy the winds will be, so keep up to date
with the latest forecast. Not too much time to look into the
extended forecast given the near term severe weather threat, but
guidance is in fairly good agreement that the western trough
will begin to move into our area by the end of the work
week/early weekend. This could bring more rain and storms to our
area on Friday and then colder weather into Saturday as
guidance indicates a stronger push of cold air advection behind
this system.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 641 PM CDT Mon Apr 13 2026

VFR conditions are expected for the majority of the period.
Thunderstorms, some severe producing 2+ inch hail, are ongoing east
of I-29 in northwest Iowa and southwest Minnesota. These storms will
continue to track northeast through about 14.03Z.

Some patchy dense fog is possible near daybreak east of I-29. This
should burn off by mid morning. A few light rain showers are
possible again Wednesday afternoon but confidence is too low to
include in the TAFs at this time.

&&

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

&&

DISCUSSION...Samet
AVIATION...AJP

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
356 PM CDT Mon Apr 13 2026

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ038>040-050-052>071-142100-
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-
356 PM CDT Mon Apr 13 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...This afternoon and tonight.

Scattered strong to severe thunderstorms expected Monday afternoon
and evening. Some storms may produce large hail 2 inches in diameter
and damaging wind gusts up to 70 mph. A tornado or two cannot be
ruled out. Greatest risk of storms is north of I-90 between 4 and 10
PM.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

More widespread chances for showers and thunderstorms exists for
Tuesday afternoon into Wednesday. This more active pattern continues
into the weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
733 PM CDT Mon Apr 13 2026

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

0630 PM     Hail             8 SE Ocheyedan          43.33N 95.45W
04/13/2026  E1.00 Inch       Osceola            IA   Public

            Social media report with a coin for
            reference. Time estimated by radar.

&&

AJP

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