513
FXUS63 KARX 242223
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
520 PM CDT Sat May 24 2025

.KEY MESSAGES...

- Remaining cool for Memorial Day weekend and into much of the
  upcoming work week with highs in the 60s and lower 70s.

- Isolated showers (15-25% chance) in north-central WI continue
  this afternoon before diminishing by evening.

- More substantial areawide rain chances (20-50%) return next
  week beginning Tuesday.

&&

.DISCUSSION...
Issued at 211 PM CDT Sat May 24 2025

Rest of Today - Memorial Day: Isolated Showers North of I-94 Today,
Remaining Cool through Memorial Day

Weaker easterly surface flow combined with northwesterly flow aloft
has allowed much of the area to remain under a quite cool airmass
for this time of the year over the past few days with highs
generally in the 50s to 60s. GOES-19 water vapor imagery and 24.15z
RAP 500mb heights show the current pattern and expect evolution
fairly nicely as a weak vorticity lobe and 500mb shortwave will
continue to eject out south-central Canada and into the Great Lakes
region, continuing to reinforce the cooler air mass in place for the
weekend. Consequently, median high temperatures within the NBM
through Sunday fail to reach into the 70s, outside of more typical
warm spots.

As this vorticity lobe pushes south through the afternoon, continued
shower development is anticipated and has already been reflected in
satellite and radar trends over north-central WI. This forcing
combined with some weak instability (under 100 J/kg of MUCAPE in the
HRRR) should continue to maintain these weak showers throughout much
of the peak heating hours but will quickly wane towards sunset.
However, since its unclear how much of these echoes are reaching the
surface given a somewhat dry subcloud layer in the RAP/HRRR, have
kept the shower mention to isolated for now. Cannot rule out some
light QPF with these as the 24.12z HREF has some small probabilities
(10-40%) for amounts over 0.01" north of I-94. Otherwise, subsidence
under an 500mb ridge should keep us dry for Memorial day with some
ever so slight moderation in temperatures with highs hovering around
the 70 degree mark.

Tuesday - Friday: Rain Chances Return, Remaining on the Cool Side

Looking ahead into Tuesday, deterministic guidance suggests that a
more pronounced upper-level low pivots its way out of south-central
Canada and into the MN/WI region. As this occurs, some pieces of
shortwave energy will eject around the low increasing our
precipitation chances beginning overnight Monday and into Tuesday.
Overall the grand ensemble (GEFS/EC/Canadian ensemble) has fairly
high probabilities (60-80%) for at least measurable precipitation
and medium probabilities (40-60%) for amounts of 0.1" or greater
through Wednesday with this system across the entire local area.
Additionally, with the upper-low lingering throughout much of the
work week, have held onto some small precipitation chances in
accordance with the NBM through Friday. Overall with little signal
in the 24.00z EFI for any anomalous rainfall amounts and little
indication for any severe potential across the Machine learning/AI
severe outlook guidance, not expecting this to be an overly high
impact system based on the current synoptic setup. However,
certainly appears to be our next chance for meaningful rainfall.

As far as temperatures are concerned, this upper-low should keep us
fairly clouded over with little change in 850mb temperatures for
Tuesday and Wednesday. As a result, likely will perpetuate this cool
pattern with highs running near 10 degrees below normal with the
10th to 90th percentile spread in the NBM across the area being in
the lower 60s to middle 70s during this period. However, as we head
towards the end of the upcoming work week and into next weekend,
some indication that this upper-low phases into a boarder troughing
regime further east, allowing for some upper-level ridging to build
into the area. As a result, there is a some wider spread for Friday
and into the weekend in the 10th to 90th percentile NBM for high
temperatures (upper 60s to middle 80s). Consequently, how this upper-
low trends for the upcoming week will be the main feature to watch
for how our precipitation and temperature trends ultimately pan
out.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 520 PM CDT Sat May 24 2025

CIGS: variable high cloudiness persists into the start of the new
work week. SCT-BKN150 at times along with afternoon, diurnally
driven high based CU. For now will stick with SCT.

WX/vsby: no impacts expected.

WINDS: remaining light from the north to east. A few Sun afternoon
gusts into the low/mid teens possible.

&&

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

&&

$$

DISCUSSION...Naylor
AVIATION.....Rieck