015
FXUS63 KARX 052326
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
626 PM CDT Fri Jun 5 2026

.KEY MESSAGES...

- Isolated to scattered storms late this afternoon thru early
  overnight. Confidence has increased for severe storms later
  this evening near and north of I-90. Large hail and strong
  wind gusts would be the main hazards with any severe storms.

- Dry start to the weekend gives away to another round of rain
  on Sunday through Monday.

- Trending hot for the middle and end of next week with highs
  likely in the 90s and heat indices approaching the 100 degree
  mark.

&&

.DISCUSSION...
Issued at 131 PM CDT Fri Jun 5 2026

This Afternoon - Early Overnight: Isolated to Scattered Storms,
Some Strong to Severe

A continued difficult forecast remains for this afternoon and into
the evening hours for storm initiation. As has been stated in
previous forecast discussions, the environment trends more favorable
for organized convection later into the evening today, the key
question is will there be enough lift to generate convective
initiation as forcing mechanisms remain uncertain. But to take
a step back, current satellite trends this morning have depicted
a low-level cloud shield over the region which is generally
expected to mix out to some extent this afternoon. As this
occurs, surface destabilization will result in an increase in
MLCAPE values to around 1000-1500 J/kg across the local area.
With some degree of inconsistency where destabilization occurs,
this will likely set up some differential heating boundaries
during the afternoon which in turn may work as an axis to
initiate convection. As a result, the CAMs generally agree on
developing storms in the area later this afternoon and in the
evening, with low confidence on exact location but the earliest
timing likely being between 2-4pm. In this environment, storms
may pose some hail and strong wind risk, however the weaker
shear profiles initially would not make this a widespread
concern. However, how convection evolves earlier in the
afternoon will certainly impact how later storms may develop as
they could work to both increase the amount of available outflow
boundaries as well as work over the environment if convective
initiation is more widespread.

This will be important for later into the evening as a shortwave
trough pushes into the area, working to cool our mid-levels
slightly and increasing mid-level shear while elongating our
hodographs. As a result, any storms that do develop in this
environment (generally 6pm to 3am) would have a tendency to
become more organized, possibly supercellular as shown in the
HRRR. In this scenario, a hail threat would be on the table with
supercell storms and 40-50 kts of 0-6km bulk shear to work with
near and north of I-90 and mid-level lapse rates to around 6.5
C/km. Furthermore, with DCAPE values increasing during the late
evening with some dry air entrainment would suggest some strong
winds within these cells would be possible in addition to cold
pool organization resulting in linear/bowing segments.

So important to emphasize that there are a few scenarios here, much
of the CAMs agree on some level of convection during the afternoon
and evening in the local area but the severe threat is conditional
on if storms can develop during the late evening period when shear
profiles begin to become more favorable. However, it is becoming
more likely that if storms do occur in the evening hours for areas
north of I-90 where the shear profiles are more robust, they will
become severe. As a result, SPC has upgraded these areas to a Slight
Risk (Level 2 out of 5) for severe weather.

Saturday - Monday: Dry Start to Weekend with Increasing Rain Chances

As we head into Saturday, upper-level ridging will move into the
area with subsidence underneath it keeping precipitation chances to
a minimum. Additionally, with relatively clear skies underneath the
ridge would expect temperatures to climb into the middle and
upper 80s during this period. However, as we head later into
Sunday and into Monday rain chances will begin to increase as a
pronounced mid-level shortwave moves into the region in the
southwesterly flow regime. As a result, precipitation chances
increase fairly significantly during this period with the grand
ensemble having fairly respectable probabilities (40-60%) for
rainfall amounts of 0.5" into Monday. With fairly high dewpoints
and moisture coming in, cannot rule out some heavier rainfall
during this period as well. However, given the lack of strong
flow aloft with this wave, organized severe convection seems
unlikely with this system.

Tuesday - Saturday: Trending Hotter

As we head late into the week, an upper-level ridge will become
situated over the local area resulting in southerly low-level flow
across the local area. As this occurs, moisture advection will
result in dewpoints increase fairly dramatically across the local
area with the grand ensemble (GEFS/EC/Canadian ensemble) having high
probabilities (70-90%) for dewpoints in the 70s. This coupled
with highs approaching the 90s would suggest that we could see
heat indices approaching the 100F mark. Some conflicting
guidance between the bias-correction in the NBM and the raw
models leads to some uncertainty in exactly how warm we will
get. But given the EC Extreme Forecast Index has a fairly strong
probability footprint (70-90%) for temperatures to exceed model
climatology, thinking temperatures will be fairly above normal,
just a matter of how much above normal and if any finer details
such as precipitation potential would keep us cooler.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 626 PM CDT Fri Jun 5 2026

Main taf concern is the potential for thunder at both taf sites
early in the taf period. Weak cold front slowly moves over the
area this evening and has been the focus for showers and
isolated storms over western Wisconsin/central Minnesota this
evening. Instability is not great over the area this evening and
weakens after 03z Saturday. Coverage of storms is expected to be
isolated across the area. For now...have introduced showers into
the taf sites between 02-04z Saturday and a tempo group for an
isolated storm at both RST/LSE taf sites. After showers pass the
taf sites...the next concern is potential for fog formation
across the region. With residual cloud cover from the showers
not sure if area will clear out. However...low level moisture
and weak inversion could develop fog over the area after 06z
Saturday. At this time will leave mention out of tafs based on
confidence is low. After 14z Saturday...VFR conditions should
prevail at both RST/LSE taf sites.

&&

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

&&

$$

DISCUSSION...Naylor
AVIATION...DTJ