Severe Thunderstorm Warning 54, NWS Sioux Falls, SD

Area Forecast Discussion
National Weather Service Sioux Falls SD
101 PM CDT Mon May 18 2026

.KEY MESSAGES...

- Showers and isolated thunderstorms return to the area this
  afternoon this evening into tonight.

- A few storms along and southeast of a Wayne to Sheldon to
  Windom line may be strong to severe late this afternoon into
  this evening. The main threat would be hail to half dollar
  size but storms this strong should remain very isolated and
  likely closer to near and east of Highway 60.

- Areas of frost or freeze will be possible on Wednesday
  morning, with the better chances north of I-90.

- Cool conditions prevail this week. Dry weather expected mid
  week. Another round of storms is possible Thursday through
  Friday.

&&

.DISCUSSION...
Issued at 1258 PM CDT Mon May 18 2026

Early this afternoon the surface to 925 mb front was across southern
NE into southern IA. Given the marginal strength of the incoming
wave, this boundary should not lift far enough north and west
by late afternoon to get into the area. This should limit any
wind and tornado threats and keep them off to the southeast.
However, some elevated hailers will remain possible across
mainly northwest IA as elevated CAPE values ramp up to about
1000-1500 J/KG and deep layer shear is a fairly strong,
unidirectional 40-50 knots. This would be lifting a parcel from
above the stratus layer, which would likely be in about the
800-750mb layer. The better chances will be from about 5 pm to 9
pm.

After this wave pushes the remaining instability out of the area
this evening, dry and cool conditions are expected for Tuesday and
Wednesday. The only concerns on these two days will be the potential
for frost and freeze conditions, mostly north of I-90, as surface
high pressure is in place. Another weaker wave moves through the
area on Wednesday but for now this appears to bring mainly mid level
cloud cover.

The next better chance for showers and thunderstorms will come
Thursday night into Friday night. At this time severe weather looks
to remain isolated as model instability fields are hinting at 1000
J/kg CAPE or less for the most part.

Once this wave passes a warming trend should move in as flat ridging
aloft develops ahead of a deepening low pressure in the Northern
Rockies. Saturday should be mild, likely in the 70s, while Sunday
sees the better chance to warm into the 80s.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1243 PM CDT Mon May 18 2026

Widespread stratus, mai.nly IFR but occasionally MVFR, will
persist through much of the night, but gradually improve later
tonight into Tuesday morning. Scattered showers and isolated
thunderstorms will increase in coverage through the afternoon
into the early evening, then gradually diminish through the
early overnight hours. The strongest thunderstorms will be in
parts of northwest IA, with the better chance from 5 pm through
9 pm. A few of these storms could contain hail.

&&

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

&&

DISCUSSION...08
AVIATION...08

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
331 AM CDT Mon May 18 2026

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ038>040-050-052>071-190845-
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-
331 AM CDT Mon May 18 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.

Scattered showers and isolated thunderstorms return to the area this
afternoon through tonight. A few strong to severe storms are possible
along and southeast of a line from Wayne to Sheldon to Windom. If
strong storms develop, ping pong ball sized hail and 60 mph wind
gusts are the main threats. However, locally heavy rainfall and a
tornado are possible.

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

Chances for showers and thunderstorms return Thursday through
Friday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
521 PM CDT Mon May 18 2026

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

0513 PM     Hail             7 SSE Moville           42.39N 96.03W
05/18/2026  E0.70 Inch       Woodbury           IA   Trained Spotter

&&

TRM

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
542 PM CDT Mon May 18 2026

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

0523 PM     Hail             3 WSW Correctionville   42.46N 95.84W
05/18/2026  M1.75 Inch       Woodbury           IA   Public

            Social media picture.

&&

ak

Preliminary Local Storm Report
National Weather Service Sioux Falls SD
548 PM CDT Mon May 18 2026

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

0539 PM     Hail             2 N Washta              42.60N 95.71W
05/18/2026  E0.88 Inch       Cherokee           IA   Trained Spotter

&&

TRM

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