595
FXUS63 KARX 210606
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
106 AM CDT Tue Jul 21 2026

.KEY MESSAGES...

- Enhanced-risk of severe storms for much of the Upper
  Mississippi River from 3 pm and 9 pm. All severe weather
  threats will be possible.

- Dry weather from Tuesday through Saturday. Coldest day will
  be on Wednesday when high temperatures will be in the lower
  and mid-70s.

&&

.DISCUSSION...
Issued at 1239 PM CDT Mon Jul 20 2026

This Afternoon and Evening

We are already seeing rapid recovery taking place in the wake of
the mesoscale convective complex across north-central Iowa and
south-central Minnesota. Temperatures are currently ranging from
the mid-80s to lower 90s. Dew points are in the lower and
mid-70s. This is resulting in surface-based CAPES of 3-4K. As
the afternoon progresses, this air mass will spread into the
Upper Mississippi River Valley ahead of a cold front extending
from the Minnesota Arrowhead to the southwest tip of Minnesota.
There is already scattered showers and storms along this front.
These storms should impact the Upper Mississippi River Valley
between 3 pm and 9 pm.

Further south, moderate to strong capping (10-12C 700 mb
temperatures) has developed across western Iowa and far southern
Minnesota. This should keep this sector relatively clean; thus,
this instability reservoir should continue to be able feed
storms this afternoon and early evening.

As a vigorous shortwave moves into the region this afternoon,
the winds aloft will strengthen. This will result 0-6 km shear
of 60-65 knots. As a result, initial storms will be likely
supercells. The hodographs are exceptionally long from eastern
portions or northeast Iowa northeast through central Wisconsin.
If these storms can become orthogonal with the cold front,
there could be a few tornadoes. SigTOR parameter is 8 in
southwest Wisconsin.

In addition with large NCAPE and strong mid-level lapse, there
could be some large hail with the earlier supercells. Over time
as cold pools coalesce, damaging winds will become the primary
threat. In addition, any surges along the line will have to be
watched for the potential for a few QLCS tornadoes.

Tuesday through Saturday

High pressure will build across the area on Tuesday and then
provide dry weather through Saturday. High temperatures will be
primarily in the 70s and 80s. The coolest day will be on
Wednesday when highs will be in the lower and mid-70s.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 105 AM CDT Tue Jul 21 2026

VFR expected for much of the 21.06Z TAF period outside of a
short window for MVFR ceilings through the late morning into the
early afternoon due to a passing perturbation increasing lower
level cloud cover. Strong northwest winds through the daytime
hours weaken into the nighttime hours, gradually turning out of
the north.

&&

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

&&

$$

DISCUSSION...Boyne
AVIATION...JAR

NWS ARX Office Area Forecast Discussion