022
FXUS63 KARX 081839
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
139 PM CDT Tue Sep 8 2026

.KEY MESSAGES...

- Showers and storms persist into the evening and overnight, particularly
  across northeast IA. Some storms may be strong to severe with
  damaging wind gusts, large hail and locally heavy rainfall.

- Additional showers and storms are likely (60-80%) for Friday evening
  and night with the potential for some strong to severe
  storms.

- Near-normal temperatures through Saturday with highs in the
  middle 70s to lower 80s. High temperatures trend below normal
  by Sunday, hovering around 70 degrees.

&&

.DISCUSSION...
Issued at 139 PM CDT Tue Sep 8 2026

This Afternoon - Overnight: Additional Showers and Storms, Some
Strong to Severe Possible

Showers and storms this morning have gradually exited the
region with an initial axis of 850mb moisture transport that is
interacting with the slowly eastward progressing front and was
responsible for much of the showers/storms this morning. As we
head into the evening, a secondary axis of 850mb moisture
transport related to the increasing nocturnal low-level jet will
aid in reinvigorating convective development by late afternoon
through the overnight. Overall, the environment looks somewhat
favorable for severe weather with hodograph presentation due to
favorable mid-level shear being present in RAP soundings across
northeast IA. This combined with initial MUCAPE values of
around 2000 J/kg would support the potential for some initial
discrete supercells before clustering into a multi-
cellular/linear complex as this moisture transport overrides the
front. As a result, thinking there is a brief window for some
severe hail before damaging wind gusts would be the primary
threat. One important caveat to note though is that the severe
potential in the local area is also contingent on exactly how
this moisture transport axis orients itself which may remain to
our south by evening and thus keeping most of the convection to
our south.

Heavy rainfall will be a possibility as well with the moisture
transport overriding the boundary allowing for storms to develop on
the front with precipitable waters also approaching 2 inches.
Additionally, warm cloud depths remain around 4km so overall a
fairly favorable environment for heavy rainfall. Currently, the
recent HREF has some higher probabilities (30-60%) for rainfall
amounts over 1 inch across northeast IA with the 90th percentile
amounts in the HREF suggesting some 2-3" amounts cannot be ruled
out. However, this again comes with the caveat that there remains
some uncertainty on the exact location of where the 850mb
moisture transport will set up this evening, so there is a
scenario where the bulk of convection remains to our south. One
additional scenario that a few of the CAMs depict as well is
additional convection developing with the actual synoptic front
pushing through the local area, not associated with the 850mb
moisture transport axis. Overall confidence in this scenario is
somewhat low as it is unclear if enough instability will be
present due to being clouded over for much of the daytime and
the main moisture plume remaining to the south. Regardless,
would expect convection to exit the region by early Wednesday
morning as the synoptic front passes through.

Wednesday - Thursday: Drier, Near-Normal Temperatures

As we head into Wednesday and Thursday, upper-level ridging and
surface high pressure build into the region. Consequently,
expecting fairly dry conditions during this period. With some
northwesterly flow into Thursday, expecting a slight dip in
temperatures with highs in the middle 70s to near 80. However,
even though the cold front passed through the local area
Wednesday morning, temperatures will still remain near-normal
due to upper-level ridging being in place.

Friday - This Weekend: Shower/Storm Chances Return, Slight Cool Down

By the time we reach Friday and the weekend, precipitation
chances will be on the increase as an upper-level trough and
attending surface cold front pushes through the Upper Midwest
later Friday and into Saturday morning. As a result, the grand
ensemble (GEFS/EC/Canadian) has fairly high probabilities
(75-95%) for measurable precipitation Friday night and into
early Saturday morning. The severe potential for this period
remains somewhat questionable as the timing of the wave would
favor convection reaching into the local area after dark when
instability would be waning. Consequently, much of the AI/ML
severe outlook guidance keeps our severe potential to the west
of the local area as the timing of the wave would need to be
slightly faster to push the probabilities eastward. Otherwise,
temperatures cool down past Saturday with highs potentially
falling into the 60s to lower 70s across the area as
northwesterly flow reinstates itself across the region. Some
guidance would suggest a wave that pushes through northern WI on
Sunday bringing the potential for rain back into the region, so
thinking that the medium probabilities (30-50%) are feasible in
the NBM for Sunday.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1159 AM CDT Tue Sep 8 2026

Showers and storms will continue to be the primary aviation concern
as we head into the evening with additional rounds of convection
likely into the overnight. Currently, the highest probabilities for
storms to develop remain south of I-90. However, given that some
CAMs attempt to develop some additional convection further north
this evening, have opted to include a prob30 for both KLSE and KRST.
As we head overnight and into Wednesday morning, IFR cigs and fog
will become the primary concern generally around 09z Wednesday and
onward given recent rainfall. Winds will begin the TAF period from
the south but will gradually shift to northwesterly by the end
of the TAF period as a front moves through the region.

&&

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

&&

$$

DISCUSSION...Naylor
AVIATION...Ferguson/Naylor