968
FXUS63 KARX 160500
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1155 PM CDT Sun Jun 15 2025

.KEY MESSAGES...

- Some severe storms are possible Monday evening mainly
  southwest to north of La Crosse. Damaging winds would be the
  main threat with large hail also possible. There is still
  uncertainty in the timing and coverage of storms which impacts
  the overall risk. Forecast updates are likely.

- Tuesday could have a small but legit severe storm threat in
  northeast Iowa and southwest WI, with more widespread rains
  expected Tuesday night and Wednesday.

- A bit more stable weather pattern should evolve at the end of
  the week with highs in the 90s for some over the weekend.

&&

.DISCUSSION...
Issued at 302 PM CDT Sun Jun 15 2025

Severe Storms Possible Monday Evening

The stagnant pattern over the area will finally come to an end
Monday night as a cold front moves into the local area to become
a focal point for storms, possibly severe. However, as we have
seen the past week, predictability in that evolution is low and
uncertainty continues to hamper confidence in a given outcome.

The instability gradient / stationary frontal boundary remains
along a line from Aberdeen SD to about Dubuque IA with most
weather occurring near that over the past days. Tonight, a
shortwave trough currently in eastern SD will weaken and ride
southeast into southern WI, leveraging the weak instability for
shower and storm chances after midnight and into Monday
morning. Rain chances have been lowered for the afternoon and
evening except on and west of Highway 52 in MN/IA. The
circulation that has caused showers in swrn WI today will slowly
wind down and the SD wave will push it east. Still some
lingering spits of rain this afternoon tho.

Ridge building is now occurring across Neb/SD ahead of a
shortwave trough ejecting northwest over the ID/MT per GOES
water vapor imagery. This trough heads east across ND/MN
developing surface low pressure in the vicinity of Aberdeen by
midday Monday. The stationary frontal boundary ABR-DBQ will be
somewhat slow to move north Monday with widespread morning
cloud over MN expected. This causes some questions as the
surface front may be slow to shift north, while elevated
instability above the front would potentially cause some
elevated storms further northeast toward central MN with
increasing low-level moisture transport, just northwest of the
area. This would bring a late afternoon storm timing n/w of La
Crosse as surface instability tries to grow into those storms.
The other solution set is the cold front, approx located MSP-
Sioux Falls by 7 pm Monday, is the main player initiating
storms in the warm unstable air that has built north across
southern MN during the day. This brings the storms into the area
after 8-9 pm from the west.

So, the clearing over MN, instability growth and placement, and
the cold front placement, along with the trough timing aloft
are causing various solutions keeping confidence low. For now,
the forecast splits the middle on the solutions on timing until
more clarity can come about. The front will move east slowly as
the surface low moves northeast parallel to the front from
Aberdeen to Duluth. Should instability increase, wind shear is
good for storms to organize and become linear and shift east
into the area for a damaging wind threat Monday evening.
Because the main low track is north, the southern extent of the
severe storm risk is in question as well. Thus, the SPC slight
risk is appropriate for the area. The later these storms move
in, the weaker they will be. They are expected to weaken
eastward into Wisconsin.

Tuesday`s Severe Storm Threat and Wednesdays Rain

According to the latest 15.12Z deterministic model runs and
15.00Z LREF, the cold front is located somewhere over northeast
Iowa and southwest Wisconsin midday on Tuesday, and slowly
shifting southeast while building instability. An estimated
30-40% of the members have a joint probability of 30+ kts of
shear and 1000+ J/Kg of CAPE in the afternoon. Soundings from
the deterministic runs indicate uncapped environments with 2500
MLCAPE, and a variety of wind profiles from okay to good. It
would seem at least a pulse storm hail threat would exist
Tuesday afternoon if the front doesnt clear the area to the
south. AI/ML probabilities support this threat.

Good agreement in the Grand Ensemble on a rainy Tuesday overnight
into Wednesday with probabilities of 40-55% for 1" of rain
roughly south of I-90 per the 15.00Z runs. This rain is in
response to low pressure traveling along the stalled frontal
boundary with ample moisture and deeper trough support aloft.
There is still some movement on the location of the moisture
transport feeding the system with a set of solutions south of
the area. Depending on the strength of the low and southerly
inflow ahead of the wave, this has potential to ramp up into
higher rainfall amounts.

Drier and Warmer End to the Week

Large scale ridge building kicks in beginning Thursday taking
the storm track further north by the weekend. There may be some
rain chances early in the weekend as the pattern evolves but
highs in the 90s should appear across the area for Sat/Sun.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1155 PM CDT Sun Jun 15 2025

Very challenging forecast with a plethora of synoptic, meso and
micro scale features that will all have roles to play in clouds and
shra/ts production through tonight. Short term guidance having a
very tough time in capturing the smaller scale features and can flip
hour to hour in their predictive outcomes. Forecast confidence high
that the region will see bouts of shra/ts through this evening.
Timing/location questions...confidence is much lower. For now, will
paint with a very broad brush, trying to highlight more likely
outcomes based more on the synoptics. There will be adjustments to
cig and pcpn trends through the day.

All said, going to lean into a VFR cig forecast for the moment.
Scattered showers (isold thunder) into the early  morning hours
Monday, with higher threat/likely for shra/ts as a cold front sweeps
in this from the west this evening.

&&

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

&&

$$

DISCUSSION...Baumgardt
AVIATION.....Rieck