311
FXUS63 KARX 181729
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1229 PM CDT Tue Aug 18 2026

.KEY MESSAGES...

- Thunderstorms are expected to develop this afternoon and a few could
  become severe, with damaging wind gusts and large hail being
  the primary hazards.

- There are periodic chances for showers and storms Thursday into
  Friday and once again next week.

- Temperatures will remain around to slightly below normal in
  the 70s to lower 80s over the next week.

&&

.DISCUSSION...
Issued at 1224 PM CDT Tue Aug 18 2026

This Afternoon through Evening: Severe Storm Potential

A few isolated showers and storms remain across the forecast area
late this morning, mainly across the southern half of the area.
These storms are not in a prime environment to become severe at this
point, but that will change as we go into the afternoon.

Cloud cover has become much more sparse than previously forecast for
this morning, which is allowing temperatures to rise into the 70s,
with some upper 70s already being observed. This is in part due to
the rain shower/storm coverage from overnight not being as
widespread as model guidance was hinting at yesterday. With that
being said, the severe storm environment for this afternoon is
increasing. A weak surface front, with a north wind in its wake, is
forecast to move in over the area in the next few hours. The front
should set up near I-90 by early to mid afternoon and this front is
expected to be the focal point for additional thunderstorm
development beginning in the 1-3 PM window. Storms should form along
the boundary and move off to the east/southeast this afternoon into
this evening. Sufficient severe storm ingredients will be in place
at that time, with MLCAPE values of 1500-2000 J/kg and bulk shear
upwards of 40-50 kts. Isolated development of storms is expected
initially, with a threat for large hail and damaging wind gusts. The
storms may congeal and form a linear line at some point this
evening, just when or if that happens is uncertain and that is
when the main severe threat would turn to a damaging wind gust
threat. The tornado potential is very low, but with a surface
boundary in play, a tornado or two cannot be completely ruled
out. Storms should begin to exit off to the east/southeast early
this evening, but a few may linger into the 9-11 PM time frame
with the severe threat decreasing by that point.

Wednesday through Friday Night: Periodic Rain Chances

The forecast area should be in between two broad systems to end this
week with a trough to the east and a building ridge to the west.
This pattern will lead to northwest flow over the Upper Midwest
during the later half of this work week and temperatures will remain
near average in the upper 70s to low 80s each afternoon. The next
decent chance for showers and storms is expected to be Thursday
night into Friday morning as a H500 impulse moves over the region.
The better chances for a half inch of rain or more are across
northeastern Minnesota into northern Wisconsin, which are currently
dealing with drought conditions and would certainly benefit from
any rainfall that the system can provide. Some rain showers or
storms may linger into the day on Friday, mainly across the
eastern half of the forecast area.


This Weekend into Next Week: Generally Dry Conditions with Mild
Temperatures

The upper level pattern in the forecast guidance diverges beginning
Saturday through the remainder of this forecast period. There is
fairly good agreement that a trough will dig south over the eastern
CONUS as the ridge from the west moves slightly east over the
Plains. Northerly to northwesterly flow will remain over the region
during this time frame, but that will be dependent upon where each
feature exactly sets up. Rain chances may continue if mid level
moisture can remain far enough east over the Upper Midwest, but
mostly dry conditions are favored at this time. Temperatures will
continue to remain in the 70s to mid 80s.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1224 PM CDT Tue Aug 18 2026

The main aviation hazard over the next 24 hours will be the
potential for thunderstorms before 00z. Both KRST and KLSE have
the potential to be impacted by thunderstorms and PROB30 groups
have been included. If any storms move over the terminals, gusty
and erratic wind along with visibility/ceiling reductions should
be expected. VFR conditions are currently forecast after the
storm potential exits off to the east. There are chances for fog
at KLSE for a few hours near 12z, but confidence is not high
enough to include in the TAF at this time. The wind will
initially be out of the west but will become northerly
overnight but should remain at 10 kts or less.

&&

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

&&

$$

DISCUSSION...Muscha
AVIATION...Muscha