Tornado and Hail in Wisconsin, April 13, 2026

Area Forecast Discussion
National Weather Service La Crosse WI
1238 PM CDT Mon Apr 13 2026

.KEY MESSAGES...

- Severe thunderstorms are expected (>70% chance) across
  southeast Minnesota and western Wisconsin this afternoon and
  evening. Large hail of 2+ inches, damaging winds of 60-70mph,
  and heavy rainfall of 1-3" are all possible from these storms.
  There is narrow window of opportunity for a tornado threat,
  but if this threat is realized, a stronger tornado (EF2+)
  cannot be ruled out.

- Additional severe storms are likely over northeastern Iowa
  and southwestern Wisconsin Tuesday afternoon. Large hail of 2+
  inches will be the biggest risk with these storms, but wind
  and heavy rain hazards remain on the table. Where exactly
  storms form will be dependent on how storms today evolve.

- Additional severe weather is possible both Wednesday and
  Friday. Details will become more clear as we get closer.

- Warm week ahead with high temperatures in the upper 60s to
  upper 70s, cooling down for the upcoming weekend.

&&

.DISCUSSION...
Issued at 1237 PM CDT Mon Apr 13 2026

Today: Severe Weather This Afternoon and Evening

A surface low sitting over northeast Nebraska continues to make its
way northeastward towards northern and eventually northeast Iowa.
The low-level jet begins to increase by mid afternoon and reaches
its strongest point during the evening with winds of 35 to 45 kts at
850 mb. Theta-e advection increases this afternoon, helping to
reduce or knock out any remaining EML by the mid afternoon. This
will result in rapid convective initiation along and north of the I-
90 corridor. Recent model trends have also started to show some
convective initiation starting earlier this afternoon in northeast
Iowa and far southwest Wisconsin. This will be something to monitor
to see how it affects the rest of the afternoon. Discrete supercells
look to be the dominant storm mode as the event gets underway. With
very high mid-level lapse rates of 7.5 to 8.5 C/km and plenty of
MUCAPE (2000 to 3000 J/kg), as well as curved and elongated
hodographs, large to very large hail will be the primary threat with
these initial storms. Right now, these storms appear to be strongest
around the I-94 corridor in western Wisconsin and eastern Minnesota.
There could always be some sort of wiggle with where exactly these
storms end up as where these storms occur will be important for the
next round of storms. Once these storms begin to congeal into a
line, then the hail threat would diminish, however a wind threat
would then be the primary threat.

Looking at the tornado risk, the main initial risk will be right
along the warm front, however given the favorable shear with a
couple counties of the warm front, the tornado threat does remain
for those locations, especially if cell mergers or other
interactions occur. The early afternoon convection could have a
tornado threat too as it rides along an elevated warm front. The one
caveat to this is that there remains quite a bit of CIN to overcome
to make these storms surface based, therefore the primary risk would
be hail with these storms. For the afternoon and early evening, if
storms can attach themselves to the warm front and have a somewhat
deviant eastward storm motion. With the amount of low level SRH
available, these right moving supercells would have the best chance
at ingesting the most SRH. Even further south of the warm front
provides a decent tornado potential given that by the mid afternoon,
there will be little to CIN needed to overcome so any boundary or
perturbation that kicks off a supercell would also have a tornado
potential. Lastly, as the supercells congeal into a line and shift
southeastward across portions of northeast Iowa, southeast Minnesota
and western Wisconsin the surface low moves up behind this line.
This extra lift with a close to perpendicular 0-3km shear
vector would indicate a QLCS tornado potential as this line
propagates through the forecast area. In addition to this
tornado threat, the wind threat would increase as the cold pools
begin to form along the line. Make sure to stay tuned as we
will have AFD updates during the afternoon and evening.

With these repeated rounds of storms, there is also a heavy rain
potential. PWATs of 1 to 1.3" are in the 99th percentile based on
the NAEFS. This means that there will be plenty of potential
moisture for storms to use up. The 12Z HREF LPMM shows a wide swath
of 1 to 3" across western Wisconsin from I-94 down towards the I-90
corridor. With this being a convective nature compared to stratiform,
there will be potential for the heavy rain corridor to shift. As a
result we have issued a Flood Watch for most of western and central
Wisconsin given that soils are saturated from the recent and that
the 6 hour flash flood guidance from the NCRFC is roughly 2 to 3.5"
across the watch area.

Tuesday: Severe Weather Potential for Northeast Iowa and Southwest
Wisconsin

Storms from Monday will be out of the local area by early Tuesday
morning. An upper level wave moves over the Upper Midwest and in
conjunction with the cold pools from overnight, the moisture gets
pushed southeastward setting up a moisture axis in far southwest
Wisconsin and into northeast Iowa. The main uncertainty for Tuesday
is how far south does the outflow from todays storm reach and if the
boundary can shift northward at all. The 15Z RAP shows this via the
theta-e advection where the boundary shifts into Grant county and
gets pushed slightly further north into Crawford and Richland
counties in Wisconsin and Allamakee, Clayton, Fayette counties in
Iowa.  Similar to today, the mid level lapse rates for Tuesday
remain high, around 7.5 to 8.0 C/km, and there will be even more
shear than today due to the upper level wave moving overhead. This
would indicate a large hail risk being the primary threat. That
being said, with the amount of low level SRH available, if a right
moving deviant supercell can get going, this will provide a tornado
risk. As cold pools develop from the storms in northeast Iowa and
southwest Wisconsin, this would push any severe threat out of the
forecast area by the middle of the evening.

Wednesday-The Weekend: Warm Week with Multiple Storm Chances

Heading into Wednesday, an upper level trough shifts over the
central Plains and the Upper Midwest. There will be some morning
convection in Iowa and into far southwestern Wisconsin. This may
inhibit any severe potential, however a surface low shifts into
central and into northern Iowa by the evening providing more lift as
theta-e advection increases during the day. Based on the NAM and GFS
there is a potential triple point that sets up in northeast Iowa,
far southeast Minnesota, and southwest Wisconsin that would
introduce a tornado threat near this occlusion. Other than this
threat, there will also a be damaging wind and hail threat across
the aforementioned areas.

Thursday looks to be dry as we begin to transition back to southwest
flow by late Thursday evening. The low-level jet increases during
Friday afternoon helping to bring in higher PWATs. Based on the
NAEFS, the PWATs for Friday are already in the 90th percentile for
this time of year. Another severe weather chance is possible as we
have this increased moisture ahead of a cold front that moves
through the area late Friday night. Temperatures through the week
will remain in the 60s and 70s until Saturday. Plenty of stormy
weather is expected this week so make sure to stay tuned for further
updates regarding todays severe weather threat as we will have
updated discussions throughout the afternoon and evening
highlighting any changes to the forecast.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1237 PM CDT Mon Apr 13 2026

Mostly MVFR to VFR conditions across the area currently with some
lingering fog creating some IFR/LIFR CIGs/visibilities across SE
Minnesota. All sites should improve to at least MVFR by mid
afternoon before we start to see storms develop along a frontal
boundary, currently just north of the terminals. Storms will likely
create MVFR/IFR CIGs and visibilities as they move east across the
region this evening and into tonight. After the storms move out an
area of low stratus and fog will redevelop, especially across NE
Iowa and SE Minnesota. This will mainly impact the KRST terminal but
KLSE could see a few hours of BR, and potentially FG. Conditions
should clear out through the morning hours tomorrow.

&&

.HYDROLOGY...
Issued at 1237 PM CDT Mon Apr 13 2026

Heavy rainfall potential for today as PWATs remain in the 99th
percentile. HREF LPMM shows a wide swath of 1 to 3" along and
north of I-90. Due to the convective nature of these storms for
today, the heavy rain swath could shift. With saturated soils,
if 2 to 3" falls, this may cause flooding to occur, especially
with 6 hour flash flood guidance of 2 to 3.5". Where the models
have the heavy rain band set up right now, would mostly impact
the Black and Wisconsin River basins. Another thing to watch out
for is mudslides as we have not greened up so any area that has
hills alongside a road could be susceptible to a mudslide.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch from 4 PM CDT this afternoon through Tuesday
     morning for WIZ017-029-032>034-041>044-053-055.
MN...None.
IA...None.

&&

DISCUSSION...Cecava
AVIATION...Barendse
HYDROLOGY...Cecava

Hazardous Weather Outlook
National Weather Service La Crosse WI
130 PM CDT Mon Apr 13 2026

IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029-
032>034-041>044-053>055-061-141100-
Mitchell-Howard-Winneshiek-Allamakee-Floyd-Chickasaw-Fayette-
Clayton-Wabasha-Dodge-Olmsted-Winona-Mower-Fillmore-Houston-
Taylor-Clark-Buffalo-Trempealeau-Jackson-La Crosse-Monroe-Juneau-
Adams-Vernon-Crawford-Richland-Grant-
130 PM CDT Mon Apr 13 2026

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

.DAY ONE...This Afternoon and Tonight

Severe thunderstorms are likely this afternoon and evening north
of Interstate 90 with a more conditional severe weather threat
further south. All storms will be capable of large hail of 2
inches or greater in diameter, damaging winds, and heavy rainfall.
The threat for a few tornadoes will be confined to somewhere
between Interstate 90 and Highway 10.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Additional severe storms are possible Tuesday afternoon, mainly
towards southern Wisconsin and eastern Iowa. Severe weather is
also possible Wednesday afternoon and Friday, but details are few
at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter reports may be needed this afternoon into the late
evening and Tuesday afternoon.

.EMERGENCY MANAGEMENT COORDINATION...

A webinar has been scheduled for 1 PM CDT Tuesday.

Special Weather Statement
National Weather Service La Crosse WI
319 PM CDT Mon Apr 13 2026

WIZ043-044-132045-
Juneau WI-Adams WI-
319 PM CDT Mon Apr 13 2026

...STRONG THUNDERSTORMS WILL IMPACT SOUTHEASTERN JUNEAU AND
SOUTHEASTERN ADAMS COUNTIES THROUGH 345 PM CDT...

At 318 PM CDT, Doppler radar was tracking a cluster of strong
thunderstorms over Reedsburg, moving northeast at 55 mph.

HAZARD...Wind gusts up to 30 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional
information and possible warnings from the National Weather Service.

A Tornado Watch remains in effect until 1000 PM CDT for central
Wisconsin.

&&

LAT...LON 4364 9001 4383 8960 4364 8960
TIME...MOT...LOC 2018Z 238DEG 48KT 4355 8999

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...30 MPH

JSB