487
FXUS63 KARX 291728
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1228 PM CDT Sun Jun 29 2025

.KEY MESSAGES...

- Showers and storms likely (50-60% coverage) this afternoon and
  evening, a few strong to severe storms will be possible with
  strong to locally damaging wind gusts being the primary
  hazard.

- Additional showers and storms possible Monday and midweek.
  However, confidence in overall coverage of these storms
  remains low.

- Seasonable temperatures to start the work week with highs in
  the upper 70s to middle 80s, but will slowly warm towards the
  end of the week.

&&

.DISCUSSION...
Issued at 1228 PM CDT Sun Jun 29 2025

Rest of Today: Showers & Storms Likely, Some Strong to Severe

Much of today will be characterized by a boundary that will
continue to push through central MN and into the local area
beginning this afternoon. This coupled with peak heating and
lingering differential heating boundaries, will enable
convective initiation to take place across portions of southeast
MN, northeast IA and west-central WI around 2-4 pm as portrayed
across several of the CAMs. Overall, instability is fairly
respectable with MUCAPE values of around 2500-3500 J/kg
suggesting that storms could develop fairly quickly but have a
difficult time organizing as 0-6km bulk shear values in the
29.15z RAP are unimpressive at around 20 kts. Will also have to
see how a low-level capping inversion manifests over the
afternoon, if this can erode effectively with peak heating and
not be hindered by upper-level cirrus, this will allow any
elevated convection to become become surface based (albeit with
relatively high LCLs), a strong to locally damaging wind threat
(40-60mph) could be realized with a few storms as DCAPE values
approach 800-1200 J/kg in the 29.15z RAP coupled with fairly
steep low-level lapse rates this afternoon.

Determining exactly where storms will develop is very challenging in
this environment as lack of appreciable bulk shear will make storms
outflow dominant somewhat quickly, hence expecting storms to be
pulse-like in nature unless they can cluster along the
aforementioned boundary. Regardless, general expectation is for
storms to slowly meander eastward throughout the afternoon and exit
the area over the course of the early evening.

Monday - Next Weekend: Periodic Storm Chances but Dry Tuesday

As we head into Monday, a broader shortwave trough pushes southward
out of Manitoba, Canada and swings through the Upper Midwest during
the daytime hours on Monday. As this occurs, a weak surface cold
front will push through the region providing the lift needed for
some showers and storms to pop up earlier in the day on Monday.
Overall, instability is more limited for Monday with MLCAPE values
around 1000-1500 J/kg and are shallower with your equilibrium level
across much of the CAMs being around 30-33kft in western WI.
However, with some stronger middle and upper-level flow in the exit
region of the synoptic trough, some marginally better 0-6km shear is
suggested in the 29.15z RAP of around 30-40 kts. This would suggest
some better organization is possible which could support some gusty
winds and small hail in western WI in spite of the less favorable
instability profiles.

Looking towards Tuesday, drier conditions are anticipated as
subsidence behind the aforementioned trough works its way into the
area. Northwesterly flow will aid in keeping temperatures seasonable
with highs in the upper 70s to middle 80s and minimal sky cover.
Will have to watch for any weak pieces of shortwave energy that
sneak through the flow on Wednesday and Thursday. With the grand
ensemble (GEFS/EC/Canadian ensemble) having medium (40-60%)
probabilities for measurable precipitation on Wednesday and
Thursday, would think that there would be some features trying to
sneak into the area. However given the lower resolvability of these
small scale features at this time range, will keep with the lower
end NBM precipitation chances for now.

By Friday, the deterministic global models (GFS/EC/Canadian) tend to
agree on developing some upper-level ridging into the area allowing
some warming of temperatures before quasi-zonal flow takes hold
keeping our temperatures steady, likely near to slightly above
average into the weekend. Some hints that a more robust shortwave
will move towards the area for next weekend with the grand ensemble
(GEFS/EC/Canadian ensemble) having high probabilities (60-90%) for
measurable precipitation. While it is far too early to
determine if there is any severe potential with this, have held
with the higher precipitation chances in the NBM for the weekend
as this is consistent with ensemble guidance.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1155 AM CDT Sun Jun 29 2025

CIGS: high/mid level cigs predominant through the forecast period.
Even with convection cigs likely to be above 6kft per the suite of
meso models.

WX/vsby: filtered sunshine and then a cold front will need to work
together to spark showers/storms this afternoon. Latest runs of the
CAMS suggest this won`t occur until the front has shifted east of
KRST. Will hedge bets and keep a brief PROB30 for thunder risk at
KRST for early afternoon, with TSRA more likely for KLSE (tempo)
from mid to late afternoon.

WINDS: southerly swinging west/northwest with the passage of the
front this afternoon/early evening. Some enhanced gustiness possible
around any collapsing storm (25-30kts).

&&

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

&&

$$

DISCUSSION...Naylor
AVIATION...Rieck