411
FXUS63 KARX 301756
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1256 PM CDT Sun Aug 30 2026

.KEY MESSAGES...

- Showers and storms move through the region this afternoon,
  mainly south of I-90.

- Increasing heat is expected Monday and Tuesday when heat
  indices climb into the mid 90s. Daily storm chances also exist,
  some of which may be strong, though confidence in if they
  develop is low (10-20%).

- The potential for showers, storms, and warmth continues into
  the late week.

&&

.DISCUSSION...
Issued at 1240 PM CDT Sun Aug 30 2026

This Afternoon - Tonight: Showers and Storms Then Drier

A weak shortwave trough lifting northeastward from Iowa atop
warm advection and moisture transport associated with an 850hPa
low level jet has been supporting some scattered shower and
storm development across Iowa this morning and is expected to
continue doing so through this afternoon (40-70%), mainly along
and south of a warm front situated around I-90. The biggest
question related to storm development is the degree of capping
present across the region and how it influences their evolution.
While MUCAPE reaches upwards of 1000-1500 J/kg per model
soundings, little, if any, of this instability is expected be
usable given the elevated nature of the storms and fairly dry
air below 10kft. Because of this, expecting primarily showers
and any storms that develop are expected to be on the weaker
side. Rainfall amounts generally less than 0.25 inches are
expected though could reach around 0.5 inches where thunderstorm
activity occurs.

After the wave this afternoon moves eastward, dry conditions
are expected overnight under partly to mostly cloudy skies.
Can`t rule out some additional shower activity towards daybreak
Monday from southwest into central Wisconsin associated with the
persistent low level warm advection although the issue of dry
air remains which leads to low confidence in any rain reaching
the ground. However, probabilities in the 30.12z HREF do
highlight this potential, currently around 10-20%.

Monday - Tuesday: Storm Chances and Increasing Heat

The warm front begins to lift northward Monday morning as a
closed upper low across southern Canada moves into the region
bringing a surface trough into the Upper Midwest. Additional
shower/storm potential exists along this boundary for Monday
afternoon though confidence is pretty low regarding
timing/location given the sporadic coverage depicted in the CAM
solutions, likely influenced by the fair degree of capping
across the region. The environment does appear to be conducive
to storm development, some possibly strong to severe, given
MUCAPE upwards of 2000-3000 J/kg and effective shear of 35-40kts
depicted in model soundings although this potential is highly
dependent on if storms can get past the cap. Probabilities for
storms developing sit around 10-20%, highest along/south of
Highway 18 where forcing along the surface trough will be
strongest, though recent CAM solutions are beginning to indicate
development may occur north of I-90 where capping is slightly
weaker. If storms do develop, gusty winds and hail will be the
main concerns.

Apart from shower and storm potential, Monday looks to be a hot
day as the persistent warm advection and southerly winds result
in surface temperatures in the mid to upper 80s and dewpoints
in the upper 60s to low 70s. While cloudiness associated with
the various waves may act to moderate temperatures slightly,
ensemble guidance is in fairly good agreement with the warm
temperatures with the 30.12z HREF suggesting an 60-90% chance
for highs to exceed 85 degrees area wide. Given the warm
temperatures and high dewpoints, heat indices Monday afternoon
are expected to climb into the mid 90s, potentially near 100
degrees within the river valleys.

The wave train continues Tuesday as a weak shortwave trough at
500hPa lifts northward out of the central Great Plains atop a
developing stationary boundary at the surface. This set-up may lead
to some additional showers and storms late Tuesday (20-30%) though
greater chances come early Wednesday morning. Heat also continues
Tuesday with highs in the upper 80s to around 90 degrees again,
resulting in heat indices in the mid to upper 90s, warmest south of
I-90.

Wednesday - Friday: Potential for Showers, Storms, and Warmth
Continues

Shower and storm potential continues through the mid to late
week as the active upper level pattern remains in place. As
previously noted, Wednesday morning has the highest agreement
regarding precipitation amongst the 30.00z LREF members as
another 500hPa shortwave traverses the surface warm front.
Current probabilities of precipitation sit around 40-70% in the
LREF grand ensemble and 40-60% in the 30.07z NBM, highest along
and north of I-90 at this point. A greater spread amongst the
ensemble membership exists past Wednesday, though daily chances
for showers and storms exist ranging from 20-50% per the 30.07z
NBM.

Apart from precipitation chances, continued bouts of warm
advection associated with predominantly southerly low level
winds should keep high temperatures around the mid 80s, which is
depicted in the 30.06z ENS/GEFS/GEPS interquartile range.
Depending on how the potential continuous barrage of rain plays
out, the forecast may ultimately trend towards a warmer or
cooler solution as the aforementioned divergence of the ensemble
membership does have outliers ranging from the low 90s to upper
70s. Would tend towards the cooler side given the potential
cloudiness and rainfall, but there`s still plenty of time for
the trend to make itself known.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1255 PM CDT Sun Aug 30 2026

Largely VFR conditions present across the area with a few lingering
instances of MVFR CIGs across North Central Wisconsin. A cluster of
showers and thunderstorms are moving east across Northeast Iowa
and Southwest Wisconsin early this afternoon, providing brief
instances of heavy rain and MVFR visibilities. This will
continue to move east and out of our local area later this
afternoon. VFR conditions will then persist areawide for the
remainder of the period. Surface winds will remain out of the
south through the overnight hours with speeds at or below 12
kts. LLWS will be possible for the KLSE terminal overnight as a
low level jet picks up and begins to veer winds above the
surface more to the southwest. Through the morning hours
tomorrow, winds at the KRST terminal will begin to veer to the
west/northwest along a weak frontal boundary but speeds should
still stay below 12 kts.

&&

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

&&

$$

DISCUSSION...Falkinham
AVIATION...Barendse