Severe Thunderstorm Warning 179, NWS Sioux Falls, SD

Area Forecast Discussion
National Weather Service Sioux Falls SD
237 AM CDT Sat Jul 19 2025

.KEY MESSAGES...

- Today looks mainly dry once the early morning activity moves
  south of the area. Some spotty showers will be possible. A few
  storms will be possible near the Missouri River towards
  highway 20 in northwest IA late tonight.

- Late Sunday night into Monday morning a few thunderstorms
  could develop, some of which could be strong to severe.
  Confidence is fairly low.

- An active pattern persists aloft Monday through Friday next
  week which looks to bring daily chances for showers and
  storms. A few of the days could see isolated severe storms.

- Seasonally warm conditions are expected next week with
  afternoon heat indices into the 90s each day. Tuesday could
  see heat indices in a few locations push 100 degrees.

&&

.DISCUSSION...
Issued at 236 AM CDT Sat Jul 19 2025

The late night and early morning activity will continue to drift
south taking the deeper instability to the south as well. This will
bring a lower chance for showers and thunderstorms to the area today
into this evening. A weak wave will move into the area this
afternoon and could bring some spotty showers, but model soundings
suggest that moisture could be a problem so for now this will be a
low impact concern. Otherwise some lower morning clouds should
gradually scour out with less clouds in the afternoon and likely
based in the mid levels. Temperatures should be on the mild side
with northeast flow and highs in the 70s.

A weak low level jet will focus near I-90 into parts of northwest IA
later tonight into early Sunday morning and could bring some spotty
thunderstorms. Instability and shear on the lower end so the
potential for severe weather is very low.

While there will be some lower chances for showers and thunderstorms
on Sunday, some weak mid and upper level ridging may aid in keeping
this activity at bay. Enough instability and mid to upper level
shear to support isolated severe storms but a more widespread
outbreak is not expected.

The area remains on the northern fringes of an upper level ridge
which supports seasonally warm and humid conditions for the week
ahead with highs in the 80s to lower 90s and lows in the mid 60s to
lower 70s. Periodic chances for showers and thunderstorms are also
expected but confidence on timing any given day is very low.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 542 PM CDT Fri Jul 18 2025

No significant changes from the previous TAFs. A mix of VFR and
MVFR ceilings remain in place this afternoon. Isolated to
scattered showers continue across the area late this afternoon.
Beginning to see convection fire near and north of US Hwy 14
(with the strongest cell at the time of this discussion near
KATY). Expect convection to continue to develop this evening and
move southeast, with additional development near I-90 later
tonight. Confidence in timing/spread of convection remains low
as CAMs continue to handle current development poorly. Storms
could be strong to severe with all modes possible.

Otherwise, guidance continues to show stratus and/or fog
developing after storms roll through tonight, leading to MVFR to
IFR or lower conditions. Improvement is expected through the
late morning and early afternoon hours.

Isolated to scattered showers and storms may develop once again
tomorrow afternoon, with the greatest chances south of I-90 and
toward US Hwy 20. Will omit from KSUX for now given low chances
and low confidence.

&&

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

&&

DISCUSSION...08
AVIATION...SG

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
410 PM CDT Fri Jul 18 2025

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ038>040-050-052>071-192115-
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-
410 PM CDT Fri Jul 18 2025

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...Tonight.

Strong to severe storms return to the area this evening and tonight.
Storms look to develop along and north of US Highway 14 and push
southeastward during this period of time. Additional storms are
expected to develop near I-90 late this evening. Large hail up to 2
inches in diameter, damaging winds to 70 mph, a brief tornado, and
locally heavy rainfall are all possible.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Additional chances for showers and storms are possible over the
weekend with the highest chances (30-40%) coming Saturday night and
again Sunday night.

No break in shower and storm chances through the entirety of next
week. Details remain uncertain so continue to check the latest
forecast for the most up to date information.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
929 PM CDT Fri Jul 18 2025

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

0926 PM     Flash Flood      Marshall                44.45N 95.79W
07/18/2025                   Lyon               MN   Emergency Mngr

            Report of numerous roads flooding around
            Marshall.

&&

KW

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
1023 PM CDT Fri Jul 18 2025

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

0848 PM     Hail             Marshall                44.45N 95.78W
07/18/2025  M0.88 Inch       Lyon               MN   Trained Spotter

&&

SG