849
FXUS63 KARX 041133
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
633 AM CDT Fri Apr 4 2025

.KEY MESSAGES...

- Generally dry conditions expected through early next week with
  chances for light rain tonight (accumulations less than .10 of
  an inch for most), mainly across Southwestern Wisconsin.
  Light snow will be possible east of the Mississippi River
  Sunday night into Monday (20-30% chance).

- Near to slightly below normal temperatures to continue through
  the weekend before a cold front Sunday brings much cooler
  temperatures for the start of next week.

- Warmer temperatures by mid-next week with additional chances (20-
  40%) for rain Wednesday and Thursday.

&&

.DISCUSSION...
Issued at 351 AM CDT Fri Apr 4 2025

Light Rain Tonight with Light Snow Possible Sunday Night into Monday

With the upper low responsible for the chaotic weather across our
area earlier this week finally out of the area, we are now in west
to southwest flow aloft, generally stuck between the two streams of
upper level flow. The southerly stream thanks to a cutoff upper low
across the Desert Southwest and the northern stream due to a
strong upper low across the Western Hudson Bay with extending
trough axis into the Northern Plains. As moisture surges north
through the Mississippi Valley today, an area of showers and
storms north of a stalled boundary across the Arklatex and Ohio
River Valley will begin to take shape. The northern extent of
this moisture and overall precipitation chances remains across
our southeastern counties. 04.00 HREF members all show an area
of an area of precipitation building northward into our local
area this afternoon and generally staying located across
Southwestern Wisconsin, co-located with 850-700 mb frontogenetic
banding, through overnight tonight before drier air begins to
move in late overnight and pushes this moisture to the south and
east. QPF totals look low overall with this activity as deep
moisture will stay well to our south. Another area of precipitation
could move in from the west with a weak, decaying cold front
moving in this evening from the Dakotas. Hi-res guidance shows
these showers dissipating as they move east of the Twin Cities
but should they hold on a bit longer, they could drop a few
hundreths of rain across our western counties.

Conditions stay dry through the weekend with our next chances for
precipitation coming with a cold front that`s expected to move
through our area late Sunday into Monday. The upper low over the
Hudson Bay begins to move east and starts to rotate Sunday/Monday,
sending a surge of cold air and a trough axis into our area. At the
surface, a low pressure system develops over the northern Great
Lakes and a strong surface high will begin to drop south out of the
Canadian Plains. This surge of cold/dry air from the surface high
will push the cold front attached to the aforementioned surface low
through our area. With this deeper cold air moving into our area,
precip chances along the front would likely be in the form of snow
as a weak mid-level frontogenetic band moves through with it. The
best chances for measurable snow look to stay east of the
Mississippi with roughly 2/3 of EC ensemble members showing
measurable snowfall at Medford and about 1/2 at La Crosse. In a
reversal from yesterday, the GFS ensemble has backed off
significantly on any precipitation for our area Sunday into
Monday with only a handful of members showing measurable snow
at Medford and virtually none at La Crosse. In any case,
snowfall is expected to be light with most places seeing totals
less than an inch.

Near to Slightly Below Normal Temperatures Through the Weekend with
Cold Temperatures Monday

Temperatures through the weekend are expected to remain fairly
stagnant overall. Northeasterly winds behind the weak cold front
tonight will keep temperatures a little cooler for Saturday in the
40s to near 50 and mid 40s to low 50s by Sunday. Temperatures behind
Sunday`s cold front will be noticeably colder, even with the light
winds overall, as a cold canadian airmass begins to move in behind
it. As northerly winds pick up through the day on Monday, temperatures
will struggle to get over 40 degrees outside of area river
valleys. These temperatures are roughly 10-15 degrees below
normal for early April. NBM probabilities of temperatures less
than 40 degrees range from 30-70% across the area with the
highest probabilities north of I-94 and across Southeastern
Minnesota.

Warmer by Mid-Week with More Precipitation Chances

The good news is that this cold is expected to be short-lived with
surface winds shifting back to the south by Tuesday and temperatures
already back into the 50s to near 60 by Wednesday. We see chances
for precipitation return for Wednesday and Thursday but details
remain very unclear at this point with differing upper level
patterns for midweek onwards. Cluster analysis shows more pronounced
ridging from the GFS ensemble across the Western CONUS with our area
in more turbulent northwest flow aloft. The deterministic model
shows a shortwave trough moving across the area with a developing
surface low and increased precipitation across our area. The EC
ensemble generally has flatter ridging and weaker, zonal flow. This
is highlighted in the deterministic outcome where the the shortwave
troughing doesn`t come to fruition until south and east of our area,
keeping the Upper Mississippi Valley much drier. Due to these
significant differences, have stuck with the low-end chance to
slight chance PoPs put forth by the NBM. This will be something
to monitor going forward as this looks to be our next best
chance at potentially heavier precipitation.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 633 AM CDT Fri Apr 4 2025

VFR today with higher clouds moving over providing a lowering
ceiling in the evening. A cold front will move through the area
while moisture will increase from the south. The combination
will cause lower ceilings to MVFR tonight. There is some signal
for IFR ceilings over northeast IA and southeast MN after 06Z
however that was not included in the 12Z TAFs. Felt this was
associated with the front later tonight after 09Z but confidence
is not high enough to include it yet (15-25%). By Saturday morning,
most of the area should be at least MVFR ceilings. Some very
light rain is expected over southern WI tonight.

&&

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

&&

$$

DISCUSSION...Barendse
AVIATION...Baumgardt