454
FXUS63 KARX 052326
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
626 PM CDT Sat Jul 5 2025

.KEY MESSAGES...

- Scattered showers and storms rest of this afternoon-evening
  with a low chance (<20%) for any strong to severe storms;
  localized gusty winds and heavy rain the main threat but can`t
  rule out a funnel cloud

- Seasonable summer stretch next week with on/off chances
  (20-40%) for showers and storms; plenty of dry breaks in
  between

&&

.DISCUSSION...
Issued at 153 PM CDT Sat Jul 5 2025

Rest of today: messy, weakly organized potential for storms

A 500mb trough continues to build into the Upper Mississippi Valley
today. A embedded shortwave / vort max along its leading edge,
in conjunction with favorable low level moisture transport, has
sustained a narrow band of showers and isolated storms since
last night from Iowa into northern Wisconsin. Despite the
moisture transport weakening toward midday, the vort max is now
encountering favorable daytime heating as it works into
Wisconsin, allowing the activity to expand northeastward.

As for convective trends for the rest of today, guidance paints a
pretty murky picture overall. The boundary layer west of the
Mississippi River, where rain was more prevalent this morning,
will likely struggle to recover much until later afternoon.
Morning sunshine over portions of western/central Wisconsin
allowed for decent but not strong low level lapse rates there
and better instability. SPC mesoanalysis and HREF suggest
1000-2000 J/kg CAPE this afternoon, but forecast sounding
profiles depict this as tall/skinny, so updraft acceleration
will be pretty limited. Add to that paltry deep layer shear,
which will prevent storms that do develop from becoming
organized, limiting their lifespan. Main threat today will be
localized gusty winds, but even that isn`t a significant risk as
the pool of favorable DCAPE is rapidly retreating eastward. All
in all, can`t rule out a few stronger storms this afternoon
into early evening and perhaps an isolated severe storm. There
have also been a couple reports of landspouts/funnels early
this afternoon upstream in parts of south-central MN and
northwest IA. Conditions are more favorable out that way with
weak surface vorticity along a wind shift line and some better
low level instability, but can`t rule out a small chance (20%)
of a funnel cloud or two west of the Mississippi this afternoon.

Eventually a weak cold front will drop southeast from MN and
northwest WI into this evening. By that time, the atmosphere
west of the Mississippi River should recover sufficiently to
allow for somewhat of a linear multicell cluster across the
area, diminishing and exiting our east by early Sunday morning.

Localized heavy rain may accompany some of the stronger storms
today-tonight. HREF localized probability-matched mean suggests
rainfall amounts through tonight should average around 1/2 inch
or less across most of the area. There will likely be pockets
of 1.5 to 2+ inches where stronger storms track or repeat over
an area.

Next week: Seasonable summer stretch with occasional storm chances

After a dry Sunday, the upcoming week looks pretty seasonable for
early July, without any significant changes in airmass but with
typical on and off chances for showers/storms. Flow aloft turns
somewhat zonal to start, but a couple embedded shortwaves cut
through the region Monday afternoon and again on Tuesday. Then an
amplifying ridge out west yields a more northwest flow pattern aloft
for our region heading into midweek, and there look to be multiple
disturbances in the flow to provide continued on and off rain
chances at times through late week. Expecting there will be some dry
periods here and there, but for now will let NBM handle it given the
wide spread in model guidance and lower predictability signals in
that timeframe. For now it holds mostly 20-40% PoPs from Monday
night through the end of the week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 625 PM CDT Sat Jul 5 2025

Showers with a few embedded thunderstorms gradually slide to the
east and dissipate this evening. Expect brief pockets of IFR
visibilities in the heaviest rain before 03Z. There is some
uncertainty in whether any fog will develop late tonight and
have added some MVFR fog to a few locations along and south of
I-90. VFR conditions are expected for the day on Sunday. Winds
switch to the NNW this evening and remain from the north at 5-10
kts for Sunday.

&&

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

&&

$$

DISCUSSION...Kurz
AVIATION...Skow