410
FXUS63 KARX 241750
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1250 PM CDT Sun Aug 24 2025

.KEY MESSAGES...

- Staying cool through Tuesday with highs in the 60s and lower
  70s before a gradual warming trend occurs through Friday.
  However, temperatures will remain below normal throughout the
  week with highs only warming into the 70s.

- Isolated to scattered showers this afternoon and evening with
  the highest chances (30-50%) near and north of I-94. The
  probability for any thunderstorms to develop is low (under
  10%).

- Additional small chances (10-20%) for showers on Wednesday
  evening.

&&

.DISCUSSION...
Issued at 1250 PM CDT Sun Aug 24 2025

Rest of Today - Monday: Staying Cool with Shower Chances Today

Our first taste of early fall is underway today with most areas in
the 60s early this afternoon. These cooler temperatures can be
attributed a remarkably cool airmass situating itself over the
region with 850mb temperatures in the 24.15z RAP falling to as low
as 5C. This cooling just off the surface combined with peak heating
this afternoon will contribute to the continued development of
isolated to scattered showers as 0-2km lapse rates increase to
around 8-9C/km. With a fairly noticeable inversion at 700mb
present in the recent RAP soundings, equilibrium levels will be
very low which would stunt any updrafts and thus making the
thunderstorm threat very low today. Overall really not expecting
much QPF with these showers as the 24.12z HREF has extremely
low probabilities (0-20% chance) for rainfall amounts of 0.05"
or more this afternoon. Any shower activity will likely wane
from west to east through the evening as instability begins to
diminish.

As we head into the overnight and Monday morning, the core of the
aforementioned cooler airmass becomes situated directly overhead. To
illustrate how potent this airmass is for this time of year, the
24.00z NAEFS standardized temperature anomalies even highlights
above normal temperatures at 200mb, consistent with some
stratospheric intrusion into this layer. Morning lows on Monday will
be cool to even chilly with most spots falling into the 40s, perhaps
even some 30s in typical cold spots of west-central Wisconsin.
Additionally, with the NBM inter-quartile range for high
temperatures on being between the middle 60s to lower 70s on Monday,
many locations outside of river valley areas are likely not to reach
the 70 degree mark. As far as precipitation chances are concerned,
an additional shortwave impulse tries to push into the area in the
northerly flow on Monday. However, given the very dry environment
with precipitable waters of around 0.5 to 0.6" in the 24.15z RAP,
most of the CAMs struggle to develop any shower activity and thus
confidence at this time for any precipitation during this period is
low.

Tuesday - Saturday: Gradual Warming, Occasional Shower Potential

As we head into Tuesday, the upper-level trough situated east of our
area will begin its very slow trek eastbound and allow for some
upper-level ridging to try and sneak into the area. As a result,
expecting a very slow warming trend to ensue through the work week
with highs returning into the 70s for most. Additional shortwave
impulses try to sneak into the area on both late Wednesday and
Saturday as shown in deterministic guidance shows two potential
waves during this period. Confidence in the later Wednesday wave is
higher in its position and tendency to move through the area in the
northerly flow. However, again lower precipitable waters would
likely limit rainfall extent some as the grand ensemble
(GEFS/EC/Canadian ensemble) only has low to medium probabilities (20-
40%) for measurable rainfall Wednesday evening. Saturday depicts
another shortwave that swings into the region however, at this
temporal range the confidence in the exact position of this wave
remains low at this time. Consequently, probabilities for measurable
precipitation in the grand ensemble (GEFS/EC/Canadian ensemble) are
fairly low (10-30% chance) granted with increasing moisture return
into the area, where this wave does end up manifesting will likely
have better chances for precipitation to occur.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1202 PM CDT Sun Aug 24 2025

VFR to high-end MVFR conditions currently present across the
area as another deck of scattered to broken stratus begins to
form over the area. All sites should lift to VFR in the coming
hours and this should continue for the remainder of the period.
Some isolated showers are expected to form this afternoon,
mainly for areas along and east of the Mississippi, but impacts
overall should be minimal with CIGs and visibilities remaining
VFR throughout. Northwest winds will continue to gust through
the afternoon and into the early evening hours around 25 kts
before tapering off around 00Z. Winds will become light out of
the west/northwest overnight and should stay at less than 10 kts
through tomorrow morning.

&&

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

&&

$$

DISCUSSION...Naylor
AVIATION...Barendse