026
FXUS63 KARX 021725
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1225 PM CDT Wed Jul 2 2025

.KEY MESSAGES...

- Smattering of storm chances today and Thursday. A few stronger
  storms are possible but the threat for organized severe
  weather currently remains low.

- Steamy start to the holiday weekend with heat indices topping
  out in the mid to upper 90s for the 4th. Cooler end with
  Sunday highs in the upper 70s/lower 80s.

- Highest rain threat overnight Fri into overnight Sat. Smaller
  chances for storms Fri afternoon, but more uncertain.

&&

.DISCUSSION...
Issued at 247 AM CDT Wed Jul 2 2025

Today - Thursday: Scattered Storms, Some Strong Storms Possible

Upper level ridging is beginning to build across the High
Plains and Rockies, leaving much of the Upper Midwest under
broadly northwest flow aloft. West/southwesterly surface flow is
going to start to bring in some more rich boundary layer
moisture. This, coupled with daytime heating, will allow for
MLCAPE values to climb to between 500-1500 J/kg by this
afternoon. A belt of stronger 500 mb winds is expected to
overspread the northern Great Lakes/Wisconsin this afternoon,
generally between 18-00Z Thursday. This is going to help
increase the speed shear across the region, allowing for
effective bulk shear values to climb into the 30-40 kt range.
While the thermodynamics look favorable, the kinematics aren`t
quite so clear. Early this morning, we`re already seeing some
ongoing convection associated with a trailing cold front moving
into northwestern Minnesota. This is expected to continue
southeast and should mainly impact areas along and north of the
I-94 corridor later today. This batch of storms is being well
resolved by the 02.00Z HREF but more uncertainty remains in the
potential for scattered convective development further south
later today as overall forcing looks to be a bit more nebulous.
Coverage varies among the CAMs but most show development by mid
afternoon across portions of Southeastern Minnesota, likely
aided by a weak shortwave impulse rippling across the area. If
we can see some development across the area, there`s a decent
chance some storms could become strong to marginally severe
given the parameter space. The weak forcing is the main limiting
factor and is the reason we stay under a Marginal Risk (Level 1
of 5) for severe weather today. The main threat would be some
instances of marginally large hail and damaging winds.

Tomorrow looks to be a fairly similar story with the continued
northwest flow aloft and southwesterly surface flow bringing in
ample deep moisture. MLCAPE values will be even higher in the
1000-2000 J/kg range for areas south of I-94, especially across
Southeastern Minnesota. Shear is a bit weaker at around 25 kts
with the 500 mb jet out of the picture. Should we see some air
mass thunderstorms develop, the amount of shear present suggests
the development of more multicellular storms with a wind
threat. Soundings show a more favorable environment for
downburst winds compared to large hail as mid level lapse rates
look poor at less than 7 deg C/km. Hodographs overall are
decently straight and long, suggesting some storm splits will be
possible. The main hindrance again will be a notable lack of
broad forcing. Pinning down where exactly we will see convective
development will be hard this far out so have gone with more
broad chance PoPs for now.

4th of July Weekend: Hot, Humid, and Unsettled

By 12Z Friday, our area will be located at the crest of the
upper ridge. Unfortunately with this ridging we get all the hot
temperatures without the added benefit of dry conditions. We
will see another day with the potential for thunderstorms,
albeit these storms look much less likely to potentially become
strong/severe. Instability will not be hard to come by given
the warm temperatures in the upper 80s to low 90s and dew points
right around 70 degrees allowing for SBCAPE values to climb
into the 1500-3000 J/kg range. However, unlike the days prior,
shear -will- be hard to come by with less than 20 kts of bulk
shear present across the area. This leads us to believe that
convection will be more pulse-like in nature with little
organization. Some of the stronger storms could produce some
downburst winds with DCAPE values over 1000 J/kg. There is a
caveat to all of this though. 02.00 GFS soundings across the
area are showing some capping in the 850-700mb layer through
much of the afternoon. Given the lack of appreciable forcing, if
this cap holds, development would be stunted. And even if the
cap does break, it looks to be late in the day meaning storms
wouldn`t have as much time to fully develop before instability
wanes. Guidance is having a hard time resolving this storm
potential given the lack of forcing but this will be something
to monitor as CAMs start to come in range.

The aforementioned upper level ridging looks to become more
latitudinal by the weekend with quasi-zonal flow expected across
our area through at least early next week. At the surface, a
weak surface low should develop across the Northern US Rockies
early Friday and push east into the weekend. Ahead of this,
robust moisture transport is expected with pWats Friday/Saturday
climbing into the 1.5-2+ inch range (roughly 140-200% of
normal). A shortwave trough in the quasi-zonal flow aloft will
pass overhead Friday night, increasing rain chances ahead of a
cold front back in the Northern Plains. As the front gets closer
through the day on Saturday, rain chances will increase given
the better deep forcing. The front is expected to exit to the
southeast through the day Sunday. A weak surface high builds in
behind it on Monday, which should keep our area largely dry for
the start of the work week. Chances for rain continue Tuesday
onwards with the potential for shortwaves to traverse the area
aloft with the continued zonal flow. These are obviously not
well resolved this far out but the potential remains so will
leave the broad-brushed low PoPs of the NBM.

Temperature wise, Friday will be the hottest day with
temperatures in many locations pushing or exceeding the 90
degree mark. With the high dew points, it will feel
uncomfortable out there if you have any outdoor plans for the
4th. Heat indices look to stay below heat advisory criteria (100
degrees) but it will be close in some places. In any case, try
to limit time outside if you can and make sure you have plenty
of water and/or ways to stay cool. Temperatures will stay warm
into Saturday with most places in the mid to upper 80s before
the cold front and more significant rain chances bring
temperatures back down into the mid 70s to 80s for Sunday and
beyond.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1225 PM CDT Wed Jul 2 2025

Diurnal cumulus around 5-6kft has developed today, dissipating
this evening. Isolated thunderstorms are possible this
afternoon and evening, but not overly confident when/where
anything will develop given low probabilities (< 30%) and the
expected pulse-like nature to them. Probabilities are highest
north of I-94, where conditions are most conducive to
thunderstorm development. Winds will be from the south to
southwest today generally 5-10KT, decreasing to 5KT or less
overnight.

&&

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

&&

$$

DISCUSSION...Barendse
AVIATION...Falkinham