La Crosse, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

053
FXUS63 KARX 260818
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
318 AM CDT Sun Jul 26 2026

.KEY MESSAGES...

- Dangerous heat today across much of the area with heat indices
  reaching 105-115 degrees south of I-94. Heat will likely
  continue into Monday with increased probabilities (50-70%) for
  heat indices over 100 degrees south of I-90.

- Increasing confidence for storms this evening and overnight
  with highest probabilities (40-70% chance) east of the
  Mississippi River. Some storms may be severe with damaging
  wind gusts and large hail being the primary threats.

&&

.DISCUSSION...
Issued at 300 AM CDT Sun Jul 26 2026

Dangerous Heat Today:

The eastern extent of an upper-level ridge extending into the
local area will dictate daytime heat indices and storm chances.
Currently, the recent HREF has very high probabilities (over
80%) for heat indices to reach over 100 degrees areawide with
respectable probabilities (30-70%) for heat indices to reach
over 105 degrees south of I-94. This is mostly due to the fact
that the NBM has fairly high confidence (70-100%) for dewpoints
reaching over 75 degrees for areas south of I-94. While 80
degree dewpoints are likely (30-70% NBM), resulting in heat
indices over 110 degrees, have tempered 85 degree dewpoints from
select sites in northeast Iowa in collaboration with neighboring
forecast offices. Given the expected dangerous heat, an Extreme
Heat Warning is in effect for areas along and south of I-94.

Storm Potential Today:

The main forecast challenge will be how convection develops
later into the afternoon and into the evening. The ongoing
signal in CAMs is for early evening convective initiation from
a shortwave impulse and enhancing upper-level jet streak
progressing into northern WI. The main remaining question is
exactly how far west convective initiation occurs in lieu of
the aforementioned upper-level ridge. Overall, confidence is
increasing for portions of western WI at risk for storms as much
of the 00z CAMs favor convecting east of the Mississippi River.

A fairly conducive severe weather environment persists as storms
shift southeast due to stronger middle/upper-level flow in the
recent RAP supports both MCS maintenance and/or supercells with
any discrete storms. Consequently, current confidence for both
large hail and damaging winds as main threats, even some very
strong wind gusts (Over 74 mph) with favorable DCAPE values over
1000 J/kg, especially should any bowing segments occur in
linear modes.

Should the aforementioned ridge axis advect farther east,
convection will likely be east of the local area due to capping
from warmer temperatures aloft. Although, the recent 00z HRRR
suggested additional storm development farther west through the
Mississippi River Valley due to propagating outflow boundaries.

Summarily, a fairly complex setup this evening and overnight
into Monday, although confidence is increasing slightly for
storms to develop by evening across portions of west/north-
central WI with a risk for damaging wind gusts and large hail.
Thinking that extreme heat is high confidence (over 80%) as
confidence for afternoon storms is lower at this point with the
higher confidence period being more into the evening hours in
light of the recent CAMs and when the stronger flow aloft works
its way in.

Heat Risk Continues Monday:

As we head into Monday, a weak surface boundary will push into the
area during the afternoon and evening hours which will re-establish
northwesterly flow across the local area. As a result, expecting
dewpoints to decrease behind this front which should keep heat
indices tempered slightly for areas north of I-90. That being said,
the grand ensemble (GEFS/EC/Canadian ensemble) has been fairly
consistent with high confidence (50-70% chance) for heat indices
over 100 degrees for areas south of I-90, thus have upgraded the
ongoing Extreme Heat Watch to an Extreme Heat Warning. Should
diurnal timing and progression of the frontal boundary affect
realized Heat Indices, these areas may require additional
amendment to an Advisory or potentially removal. Given varying
criteria with more southern latitude forecast offices that near
climatologically warmer thresholds, collaboration in neighboring
forecast offices persisted Extreme Heat Watch.

Monday Storm Potential:

Some storms cannot be ruled out (10-30% chance) in west-
central WI for Monday morning and into the afternoon which may
contain some severe threat, however this window would be
relatively brief as the the main forcing with the associated
shortwave pushes east of the region fairly quickly. Would also
need to watch later into the afternoon with the aforementioned
weak boundary that pushes through which could initiate storms as
well which would be accompanied with a severe threat as the
aforementioned upper-level jet streak remains in place.

Tuesday-Saturday: Warm Temperatures Continue with Storm Chances

The ridge shifts westward just enough and northwest flow remains in
place. Both of these will mean temperatures cool down slightly, into
the mid to upper 80s but it also means that the 70F dewpoints would
be less likely to occur. Heat indices will also stay in the 80s to
around 90F. With this flow pattern, ensemble guidance has low
precipitation chances through midweek with better chances as we head
towards the weekend. Another thing to note is that given the
northwest flow pattern, we will have to watch for any waves that
ride around the ridge as these would impact portions of the Upper
Midwest.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1243 AM CDT Sun Jul 26 2026

Ongoing storms will be immediate concern a both TAF sites as
line shifts east through central Minnesota on local RADAR
imagery. Have accounted for overnight potential with PROB30 at
both TAF sites. Periodic storm chances continue through much of
the 26.06Z TAF period. While environment is conducive to storms,
exact timing and location remains less confident and therefore
have omitted from TAF inclusion in 26.06Z issuance.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Extreme Heat Warning from noon today to 9 PM CDT Monday for
     WIZ053>055-061.
     Extreme Heat Warning from noon today to 9 PM CDT this evening
     for WIZ032>034-041-042.
     Heat Advisory from noon today to 9 PM CDT this evening for
     WIZ017-029-043-044.
MN...Extreme Heat Warning from noon today to 9 PM CDT this evening
     for MNZ079-086>088-094>096.
IA...Extreme Heat Warning from noon today to 9 PM CDT Monday for
     IAZ008>011-018-019-029-030.

&&

$$

DISCUSSION...Cecava/Naylor
AVIATION...JAR