293
FXUS63 KARX 312344
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
644 PM CDT Sun Aug 31 2025

.KEY MESSAGES...

- Mostly dry conditions through Monday with an isolated shower
  or storm possible for portions of southeast Minnesota and
  northeast Iowa, with the better chances remaining west of
  I-35.

- The chances for widespread rain continues to increase (55 to
  75%) for Tuesday into Wednesday as a cold front moves through
  the region.

- Near-normal temperatures through Tuesday then below normal
  temperatures through the end of the week.

&&

.DISCUSSION...
Issued at 131 PM CDT Sun Aug 31 2025

Mostly Dry Early With Better Storm Chances Midweek

A shortwave continues to move through the Central Plains bringing
showers and storms to that area today and Monday. With the
associated surface boundary southwest of the area, rain chances
should largely stay out of our CWA, however cannot rule out a shower
or storm for areas just east of I-35 in southeast Minnesota and
northeast Iowa this afternoon and Monday afternoon. Ahead of a
longwave trough that dips down into the Upper Midwest and Great
Lakes regions, a shortwave comes into the Upper Midwest providing a
chance of showers and storms Tuesday afternoon.

As the trough comes down, a cold front will be associated with it.
This will bring an increased chance for storms Tuesday night into
Wednesday. There will be around 500 to 1000 J/kg of MLCAPE available
to work with for Tuesday afternoon and evening as well as a little
DCAPE, around 500 J/kg, a stronger storm could be possible if
convection occurs with the shortwave before the cold fronts arrival.
Current timing suggests the cold front arrives Tuesday night and
makes its way through the CWA during the overnight. Storm chances
continue to increase along the front (55 to 75%) for the forecast
area. As instability wanes during the later evening and early
overnight period, the thunderstorm potential decreases. PWATs with
this system are roughly between 1 and 1.25" and with the quick
progression of the front, QPF values remain on the lower side. The
most recent LREF has between a 40 to 75% chance for at least 0.25"
falling with the higher amounts in central and northern Wisconsin.
After this moves out, another cold front is set to move through on
Thursday night bringing another rain chance.

Seasonable Temperatures to Start the Week with Much Cooler
Temperatures Midweek

The beginning part of the week continues to remain quite seasonable
with highs in the mid to upper 70s through Tuesday. Then as the
longwave trough sweeps down, much cooler air will come with it. The
850mb temperatures, compared to the previous couple of days have
come up slightly for Thursday in the deterministic models. They are
now between -3C to 3C. This translates to high temperatures in the
mid 50s to near 60F with morning low temperatures in the upper 30s
to low 40s. Temperatures will gradually warm up as the trough shifts
eastward. Still, high temperatures are not expected to get back into
the 70s until Sunday.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 627 PM CDT Sun Aug 31 2025

Concerns continue to focus on potential for valley fog/stratus
overnight tonight into early Monday. While winds through the
troposphere are light, guidance has continued to point toward a
shallow light (11-13kts) low level jet which may have prevented
fog from fully breaking out last night despite favorable
conditions. Additionally, dewpoint depressions remain a bit
higher than ideal this afternoon. Have therefore continued to
hold with a BCFG mention and a SCT group at LSE. That said, any
of ONA/LSE/PDC/OVS may see LIFR conditions late tonight into
Monday morning. VFR conditions should return areawide by 15z
Monday.

&&

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

&&

$$

DISCUSSION...Cecava
AVIATION...Ferguson