090
FXUS63 KARX 170557
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1257 AM CDT Fri Apr 17 2026

.KEY MESSAGES...

- The risk for severe storms across the region is increasing for
  this afternoon with all hazards possible. The main uncertainty
  in the forecast revolves around when the storms form, which
  will dictate what areas see a certain threat.

- Near to below freezing overnight low temperatures through the
  weekend. A few snow flurries cannot be ruled out on Saturday,
  mainly along and northeast of I-94.

- Dry conditions and warming temperatures expected for the start
  of next week.

&&

.DISCUSSION...
Issued at 221 PM CDT Thu Apr 16 2026

Severe Storms Friday

A quiet and sunny Thursday is expected to give away to a rather
stormy Friday across the area. A busy forecast is expected with a
potentially significant severe weather event across the area. So
lets get into the details.

A deep trough is expected to move into the Rockies early tomorrow
morning, gradually sliding east into the plains. At the surface, a
series of lows will extend from North Dakota into the Central Plains
with a cold front connecting them. As the upper trough moves east,
ascent in the southwest flow ahead of it will overspread the area,
interacting with the cold front at the surface. A stout warm sector
is expected to develop out ahead of the cold front as moisture
surges northward with increased low level southerly flow bringing
60+ degree dew points into the region late tomorrow morning.
Combined with 70-80 degree ambient temperatures, this will allow
for 2500-3500 J/kg of CAPE to develop by early afternoon with a
weak capping inversion in place. Once this capping erodes with
daytime heating, its essentially game on for storms to form
along and ahead of the front with the combined upper level
ascent and surface forcing from the front. Storms are expected
to go up during the afternoon, quickly becoming supercellular
and likely severe amid 30-50 kts of effective shear. Initial
threats with this activity will be the potential for large to
very large hail given steep mid level lapse rates and
significant cooling aloft allowing for ample CAPE in the HGZ.
The other main threat with this supercell activity will be the
potential for strong tornadoes. An 850-700 mb jet around 40-60
kts out of the south will help to increase low/mid level
curvature in the hodograph. If surface flow can back more to the
southeast, a solution put forward by the 16.12 NAM, this would
create even more low level helicity. And given the proximity to
the surface low, an enhanced corridor of tornado potential is
looking more likely across portions of Wisconsin and Iowa
tomorrow. Eventually storms will grow upscale into more of a
QLCS type feature with the threats transitioning to damaging
winds and QLCS tornadoes (tornadoes will be a threat no matter
the storm mode tomorrow).

The main point of contention will be how early the low level capping
erodes and storms can start to initiate. Current thinking is that
this will take place during the early afternoon right around the
Mississippi River. The timing of the front will also be a point
of contention because is storms fire more to the west, they may
become more linear by the time they get to our eastern zones
(though this is a low confidence scenario at less than 20%). If
storms fire farther to the east than zones to the west might not
even see any severe weather. So the placement of initiation
will be a key detail as it will help define what hazards, if
any, a given area is likely to see. These storms will also be
efficient rainfall producers with the 16.12 HREF mean showing
widespread 0.5-1 inches of QPF across the region (highest
totals east of the Mississippi). If a situation where discrete
cells ahead of the front develop with a more linear storm mode
directly along the front, this could mean repeated activity for
some locations. Many places across Southwest and Central
Wisconsin do not need any more rain with continued areal and
river flooding ongoing. A current reasonable worst case scenario
would be 1.5-2+ inches, mainly east of the Mississippi. A lot
of it will depend on the exact track of the strongest storms and
higher localized amounts will certainly be possible.

Cooler and Drier Saturday and Beyond

As the front pushes through the region, cold air advection will
start up shortly behind it. This will usher in much cooler
temperatures across the area with lows Friday night into Saturday
falling into the upper 20s to mid 30s. The low is expected to move
in a northeasterly track into Ontario through the day Saturday.
Because this has trended a little further northeast with each
forecast update, the chances for snow showers Saturday morning
are looking lower and lower. Wouldn`t be surprised if we don`t
see any snowflakes by the time all is said and done. That being
said, if we do see a few snowflakes, they should not accumulate
given road and ground temperatures are well into the 50s with a
recent stretch of 70 degree temperatures. In any case,
temperatures Saturday will be 20- 30+ degrees cooler than where
they were on Friday - welcome to spring in the Midwest! The good
news is that with this cooler air comes a much drier airmass as
a surface high moves in from the Canadian Plains by Sunday.
This will create some minor fire weather concerns for Sunday as
RHs will drop to as low as 25% with winds gusting to nearly 20
mph out of the northwest on Sunday. This will be something to
monitor after Friday`s severe storms. RHs generally tend to
level out by Monday as temperatures start on a gradual upward
trend with southerly surface flow bringing warmer, more moist
air back into the region. Precipitation chances don`t look to
return until next Wednesday night.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1250 AM CDT Fri Apr 17 2026

VFR conditions continue for the rest of the night with an MVFR
CU field developing towards late morning and continuing into the
afternoon. Thunderstorms are expected to develop along and ahead
of a cold front that moves through during the afternoon, some of
which could be severe and produce large hail and damaging winds.
South to southeast winds of 10-20G25-30kts increase through the
morning with winds backing to the northwest at 10-20G20-25kts
behind the front for the evening and overnight.

&&

.HYDROLOGY...
Issued at 221 PM CDT Thu Apr 16 2026

A Flood Watch has been issued for Southwest Wisconsin and portions
of West Central Wisconsin given the chance for additional showers
and thunderstorms Friday afternoon and evening. These areas have
already seen copious amounts of rainfall over the last week with
many rivers experiencing signficiant flooding (enough to close
some roads in multiple counties). Outside of river flooding,
there remains a lot of ponding across the region in the valleys
The sunshine today will certainly help some but not nearly
enough. With another .5 to 1+ inches of rain expected with
Friday`s activity, any additional QPF will be problematic and
only exacerbate existing problems. Mudslides also look to be a
problem as we haven`t seen a full green up yet so roots have not
taken a strong hold yet. Rivers across Wisconsin are likely to
see additional rises, especially the Kickapoo, Yellow, Black,
and Wisconsin Rivers.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch from this afternoon through Saturday morning for
     WIZ042>044-053>055-061.
MN...None.
IA...None.

&&

$$

DISCUSSION...Barendse
AVIATION...Skow
HYDROLOGY...Barendse

NWS ARX Office Area Forecast Discussion