952
FXUS63 KARX 120555
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1255 AM CDT Tue May 12 2026

.KEY MESSAGES...

- Showers move through the region this morning with rainfall
  amounts generally under a tenth of an inch expected.

- Windy for today with winds gusting as high as 30 to 40 mph
  through the early evening hours. Wind gusts of around 50 mph
  cannot be ruled out (~10% chance) with showers this morning,
  however confidence is low in where/if this will occur.

- Temperatures cool down for the middle of the week with highs
  in the 60s and 70s. However, highs warm into the upper 70s and
  80s by Friday with an increasing risk for showers and storms.

&&

.DISCUSSION...
Issued at 1054 PM CDT Mon May 11 2026

Today: Windy with Showers This Morning

A fairly well pronounced shortwave will push through the region this
morning and throughout the day as it crosses into northern
MN/WI. As it pushes into the region, a fairly pronounced surface
low with a tight surface pressure gradient will both note an
increase in our winds during the morning as well as bring a
round of showers into the local area. The main immediate
question with these showers around sunrise will be how they
interact with a rapidly increasing low-level jet at 850mb with
the recent RAP having winds of 50-60 kts in this layer. This
coupled with momentum transfer to the surface within any more
robust showers may allow these winds to reach the surface.
However, given the fairly robust dry layer and nocturnal
inversion in place, it is unclear exactly to what extent this
would occur. However, given these strong winds off the surface,
cannot rule out some wake low potential on the back edge of
these showers which could bring strong to locally damaging wind
gusts. Overall the recent HREF only has low probabilities
(10% chance) for wind gusts over 50 mph where showers occur,
emphasizing that these may be more localized but still a
tangible threat this morning. All said, while some of the CAMs
have signal for these gusts to occur, it is not clear how this
would interact with the inversion in place. As far as rainfall
amounts are concerned, ensemble guidance is fairly unimpressive
in part due to the aforementioned low-level dry layer keep
precipitation rates on the lighter side. As a result, the recent
HREF only has low to medium (10-50%) for rainfall amounts of
0.05" or greater during the morning hours.

As we head into the remainder of the daytime hours, the lessening of
the nocturnal inversion will allow for diurnal mixing to mix
down low-level winds of 30 to 40 kts across the area. As a
result, expecting wind gusts to increase for much of the day to
around 30 to 40 mph. Eventually, a cold front passes through the
region later into the day shifting winds from southerly to
northwesterly before winds will decrease as the aforementioned
surface low begins to push eastward of the local area with the
surface pressure gradient lessening overnight.

Wednesday - Thursday: Cooler, Light Shower Chances Late Thursday

As we head into Wednesday, subsidence on the back edge of the
troughing regime will allow for surface high pressure to build into
the region for the day. Consequently, expecting clearing skies and
winds to gradually decrease by the time late afternoon and into the
evening rolls around on Wednesday. Given the northwesterly flow
regime, highs will be noticeably cooler for the daytime hours with
the inter-quartile range in the NBM generally keeping highs in the
lower 60s to lower 70s.

Surface high pressure moves directly overhead during the overnight
hours on Wednesday. As a result, sky cover and winds will lessen
considerably which in turn will allow for optimal radiational
cooling. Where winds are more likely to become calm across portions
of west-central WI, low temperatures in the 30s combined with these
light winds will likely result in frost formation. Upper-level
ridging and southerly surface flow on Thursday will allow for a
warming trend to begin with highs returning into the 70s on
Thursday. However, as some vorticity advection coupled with this
warm advection regime moves through the local area on Thursday
night, precipitation chances increase accordingly. Overall
probabilities for rainfall over 0.1" are respectable (40-70% chance)
within the grand ensemble (GEFS/EC/Canadian ensemble), however given
the weaker forcing and minimal instability, rainfall amounts greater
than this seem unlikely at this point.

Friday - Sunday: Warming Back up with Periods of Showers and Storms

By the time the end of the work week rolls around, warm air
advection is in full swing with highs returning into the upper
70s to 80s for the area on Friday and into the weekend. For
Friday and Saturday, the synoptic pattern favors a more quasi-
zonal flow pattern with periodic shortwave perturbations in the
flow. This coupled with southerly return flow will aid in
increasing our dewpoints along with more favorable instability,
the trouble that remains though is exact timing and exactly how
far north the moisture push gets into the region during the
weekend. Currently, ML/AI outlooks try to sneak some increasing
probabilities for severe weather into the area south of I-90 for
Sunday. However, remains fair to early to say how this would
manifest as both deterministic and ensemble guidance still
struggle to resolve any individual shortwave perturbation well.
Regardless, the grand ensemble (GEFS/EC/Canadian ensemble) has
high probabilities (70-90% chance) for measurable precipitation
heading into Sunday so confidence is high that there will be at
least some periods of showers and storms this weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1255 AM CDT Tue May 12 2026

A warm front will produce scattered showers and storms as it
move through the area overnight and Tuesday morning. Southeast
and south winds will be sustained in the 15 to 25 knot range
with gusts up to 35 knots. Ceilings will be 8-12K feet. A cold
front will move through the area late this morning and early
afternoon. As this occurs, the winds will shift to the
northwest.

&&

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

&&

$$

DISCUSSION...Naylor
AVIATION...Naylor