Severe Thunderstorm Warning 74, NWS La Crosse, WI

Area Forecast Discussion
National Weather Service La Crosse WI
819 PM CDT Sun May 17 2026

.KEY MESSAGES...

- Severe weather possible between 7 PM and 1 AM tonight. All
  hazards are possible mainly west of the Mississippi River.

- Another round of severe weather possible on Monday night
  between 9 PM and 4 AM. The main threat will be damaging winds.
  With isolated threats of hail and maybe a few QLCS tornadoes.

&&

.UPDATE...
Issued at 805 PM CDT Sun May 17 2026

Ongoing non-severe scattered storms across the local area are
inhibiting northward progression of warm front seen through
north-central Iowa on surface observations this evening, keeping
local severe threat conditional, i.e., lower overall confidence.
Intensification of the low level jet, 45 kt south wind on DMX
VWP, suggests a northern shift in warm front surging instability
farther north in the next 1-2 hours. Therefore, initial threat
of surface based, semi-discrete storm mode remains a low
confidence scenario to remain cognizant of until the eventual
MCS on radar imagery quickly shifting east through central
Minnesota arrives in 3+ hours. While main threat with this line
will be damaging winds, should the warm front reach farther
north, a QLCS tornado threat would exist primarily along the
frontal boundary. Therefore, the ongoing Tornado Watch may
require a switch to Severe Thunderstorm Watch.

&&

.DISCUSSION...
Issued at 1257 PM CDT Sun May 17 2026

This Afternoon

The remnant MCV which brought rain mainly south of Interstate 94
will continue to move northeast away from the area this afternoon.
As it does, the showers and isolated storms currently along
Interstates 90 and 94 will move east northeast away from the area.
Additional rainfall amounts will be up to a half inch. As a warm
front gradually lifts northward, temperatures along and south of
Interstate 94 will warm into the 60s and lower 70s, and into 60s
north of this Interstate. This will result in surface-based CAPES
climbing into the 1000 to 2500 J/kg along and south of Interstate 90
by 7 pm.

Tonight

Late this afternoon and evening, 2-3K J/kg CAPES will develop ahead
of a squall line moving east across eastern South Dakota, eastern
Nebraska, northern Iowa, and southern Minnesota. with 0-6 km
shear approaching 40 knots, there could potentially be some
supercells located along the line (these would likely stay
west of the Upper Mississippi River Vally) and along the warm
front near the Minnesota and Iowa boarder. In addition to the
deep shear, there is 200-300 EHI along the Minnesota and Iowa
boarder and downdraft CAPEs up to 1K J/kg. The discrete
supercells ahead of the squall line would be capable of
producing wet microbursts, large hail, and isolated tornadoes
between 7 PM and 10 PM in southeast Minnesota and northeast
Iowa. The threat will then shift to more damaging winds and
maybe a few QLCS tornadoes as the squall line moves into
southeast Minnesota and northeast Iowa between 10 PM and 11 PM.
This line will then gradually weaken as the instability wanes.
The severe weather threat will likely wane by 1 AM Monday.

Monday night

A cold front will move east through the area. There will be 1-2K
J/kg CAPES ahead of this front. With much of the deep (0-6 km) shear
located post frontal, not anticipating any supercells. As a result,
if there is severe weather, it would be located along the cold front
as a squall line. The primary threat would be damaging winds with
secondary threats as hail and QLCS tornadoes. Timing looks to be
rather similar tonight with the squall line moving into northeast
Iowa and southeast Minnesota between 9 PM and 10 PM. It will exit
the area between 2 AM and 4 AM. By this time, the winds will likely
be sub-severe.

Friday into Saturday

A shortwave trough will move east through the area. This will result
in another round of showers and isolated storms. With CAPES less
than 250 J/kg and 0-3 km and 0-6 km shear less than 25 knots, not
anticipating any organized severe weather at this time.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 636 PM CDT Sun May 17 2026

MVFR to IFR conditions currently present across the region with
some isolated instances of LIFR along and south of the I-90
corridor. Low clouds are expected to linger for most areas
through later tonight with some low precip chances. The main
chance for storms looks to push east into the region late this
evening - likely between 04-08Z for the terminals. The main
threat with this line of storms will be strong winds and heavy
rainfall so have continued with the TEMPO groups that bring
stronger winds in for a short time period. Lower rain chances
will continue into tomorrow morning behind the line of storms
with most locations lifting back to VFR CIGs through the
morning. Some lower MVFR/IFR CIGs may linger across portions of
SE Minnesota and WC Wisconsin so have kept them at the KRST
terminal through the end of the period.

&&

.HYDROLOGY...
Issued at 106 AM CDT Sun May 17 2026

One to two inch totals are still forecast across the area, with
areas further west more favored for the 2 inch totals. This will
likely not cause river flooding, only within bank rises.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.

&&

UPDATE...JAR
DISCUSSION...Boyne
AVIATION...Barendse
HYDROLOGY...Baumgardt

Hazardous Weather Outlook
National Weather Service La Crosse WI
129 PM CDT Sun May 17 2026

IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ032>034-041-
181100-
Mitchell-Howard-Winneshiek-Allamakee-Floyd-Chickasaw-Fayette-
Clayton-Wabasha-Dodge-Olmsted-Winona-Mower-Fillmore-Houston-
Buffalo-Trempealeau-Jackson-La Crosse-
129 PM CDT Sun May 17 2026

This Hazardous Weather Outlook is for portions of north central
Iowa...northeast Iowa...southeast Minnesota and west central
Wisconsin.

.DAY ONE...This Afternoon and Tonight

Scattered severe storms are possible later this evening and
early overnight with damaging wind as the main threat as a line
of storms progresses from west to east.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

Scattered severe storms possible Monday evening and overnight
with damaging wind the main threat.

.SPOTTER INFORMATION STATEMENT...

Severe storm reports would be greatly appreciated.

.EMERGENCY MANAGEMENT COORDINATION...

No webinar is scheduled.

WIZ017-029-042>044-053>055-061-181100-
Taylor-Clark-Monroe-Juneau-Adams-Vernon-Crawford-Richland-Grant-
129 PM CDT Sun May 17 2026

This Hazardous Weather Outlook is for portions of central
Wisconsin...north central Wisconsin...southwest Wisconsin and
west central Wisconsin.

.DAY ONE...This Afternoon and Tonight

Scattered strong storms are possible overnight with wind gusts as
high as 45 mph as a line of storms progresses from west to east.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

Scattered severe storms possible late Monday evening and
overnight with damaging wind as the main threat.

.SPOTTER INFORMATION STATEMENT...

Severe storm reports would be greatly appreciated.

.EMERGENCY MANAGEMENT COORDINATION...

No webinar is scheduled.

Boyne

Preliminary Local Storm Report
National Weather Service La Crosse WI
1039 PM CDT Sun May 17 2026

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

1034 PM     Tstm Wnd Gst     Nora Springs            43.14N 93.01W
05/17/2026  M70 MPH          Floyd              IA   Fire Dept/Rescue

&&

Preliminary Local Storm Report
National Weather Service La Crosse WI
1100 PM CDT Sun May 17 2026

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

1057 PM     Tstm Wnd Gst     Austin Airport          43.66N 92.93W
05/17/2026  M61 MPH          Mower              MN   AWOS

&&