La Crosse, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

520
FXUS63 KARX 250300
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1000 PM CDT Thu Apr 24 2025

.KEY MESSAGES...

- Periodic showers and storms this afternoon through Friday
  morning with rainfall amounts of 0.5 to 1" expected across the
  area. A strong storm containing small hail cannot be ruled
  out.

- Seasonable temperatures expected through the weekend with
  highs in the upper 50s to middle 60s. Temperatures will warm
  above normal for Monday with high probabilities (70-90%) for
  temperatures to reach into the 70s areawide.

- Additional showers and storms (60-90% chance) move into the
  area for Sunday through Monday night with the potential for
  organized severe weather on Monday.

&&

.DISCUSSION...
Issued at 305 PM CDT Thu Apr 24 2025

Rest of Today - Friday:

Scattered showers have struggled to shift northeast through the
early afternoon in northeast Iowa. While radar reflectivity has
been evident, have not recorded much in the way of reportable
precipitation as the stronger signal lies slightly southwest into
central Iowa where a couple hundredths of rainfall has been reported
over the last couple of hours. A couple of surface fronts around the
circumference of the forecast area are causing a dry "dome" locally.
The weaker front along our south is responsible for the mostly dry
aforementioned radar returns with a 10 degree difference in
dewpoints caused by easterly flow through central Wisconsin. A more
pronounced stationary front, oriented from southwest to northeast
from the Central Plains through central Minnesota, has been
lingering over the Upper Mississippi River Valley over the last
couple of days. The associated surface low pressure is situated near
the Kansas/Nebraska border. A meager upper level open wave weakens
and lifts over the next few hours, advecting the surface low slowly
northeast along the aforementioned stationary boundary.

As seen on radar imagery early this afternoon, immediate confidence
for precipitation chances remains just to the northwest through the
afternoon where meager isentropic upglide resides. Confidence only
remains moderate as this meager boundary may fluctuate some,
affecting the extent of the drier easterly flow and resultant
eastern extent of precipitation.

Eventually, the aforementioned synoptic upper level wave receives
assistance from a southeast sagging weak open upper level wave
through the Northern Plains. This will finally rid the forecast area
of the lingering stationary front overnight. This long-awaited
forcing brings widespread precipitation chances shifting southeast
through the forecast area overnight into Friday morning. A more
easterly jog to the surface low has kept the higher moisture along
and to our south, limiting overall rainfall amounts locally to
southern counties in northeast Iowa and southwest Wisconsin.

Highest accumulations expected in a southwest to northeast oriented
band from the best moisture convergence along the frontal boundary.
Current confidence places this from northeast Iowa through central
Wisconsin. HREF LPMM suggests narrow strips of 1"+ while overall
mean remains near 0.75". Regardless, HREF maximum remains under 2"
albeit more widespread. Outside of most recent Fv3 (24.12Z),
individual member dProg/dt has been on a decreasing trend from a
weaker, more easterly advecting surface low. While river flooding is
ongoing early this afternoon, not much in the way of additional
impacts are expected given the overall /lower/ amounts. Will see
some rises albeit not overly concerning.

Additional Showers and Storms Move In This Weekend:

Saturday looks to be the more pleasant in the next few days as upper-
level ridging moves into the area which will aid in clearing out our
sky cover. Temperatures will moderate somewhat with progged high
temperatures in the national blend generally in the upper 50s
to middle 60s. However, as our next weather system begins to
approach the region, sky cover will increase late Saturday
evening and into the overnight.

As we head into the daytime hours on Sunday, a strong ribbon of low-
level theta-e advection associated with an incoming warm front. As
this occurs, some elevated instability will begin to work its way
into the area from the west as dewpoints begin to increase. As a
result, expecting some showers to develop initially with convection
becoming more robust showers and storms Sunday evening and into the
overnight as probabilities for MUCAPE in the grand ensemble
(GEFS/EC/Canadian ens) increase to 30-70% by 7pm on Sunday. Overall,
with fairly weak upper-level flow and a well pronounced capping
inversion for Sunday, thinking that any severe potential would be
kept to a minimum ahead of stronger dynamics working their way into
the region on Monday.

Much Warmer, Severe Weather Potential For Monday:

Monday has some potential to be an active day in the Upper Midwest
as the aforementioned trough pivots towards the area, subjecting our
region to southerly flow. After the previously mentioned warm front
pushes through the area, dewpoints will increase rapidly with very
high probabilities (60-90% chance) for values hitting 60 degrees in
the NBM on Monday afternoon and evening. Additionally, sounding
profiles within the grand ensemble (GEFS/EC/Canadian ensemble)
utilize this increase in moisture with every of the 100 members
having some MUCAPE present with the ensemble mean values between
1000-2000 J/kg, (90th percentile as high as 3000 J/kg). One of the
key questions that will need to be monitored over the coming days
will be a low-level capping inversion present in GFS soundings from
the warm advection. Depending on if and when this cap breaks, robust
instability profiles would easily instigate any convection with
present lifting mechanisms on Monday afternoon and evening. A
secondary consideration for Monday will be how shear profiles will
manifest. The 24.12z GFS and grand ensemble hodographs would suggest
some low-level curvature, however profiles become more messy aloft
and less ideal for deep, rotating updrafts. Another point to
consider as well with this though is there remains some timing
differences for when the main upper-level trough axis moves through
the area, if this later with the surface low to our north overnight,
then the highest threat will likely remain west/southwest of the
local area with the frontal passage towards Tuesday morning.
Regardless, confidence is fairly high for meaningful precipitation
during this period with the grand ensemble (GEFS/EC/Canadian ens)
having high probabilities (60-80% chance) for amounts of over 0.25"
Will need to see how convective trends pan out with 3-hr flash flood
guidance being between 1.75" to 2.25" across the area.

Overall, still many questions on the how the environment will shake
out as this remains a few days out. But all severe hazards at
this current juncture would appear to be in play depending on
how the aforementioned dynamics and shear profiles pan out. As
a result, much of the AI and machine learning severe hazard
models (CSU/FengWU/Pangu) models continue to highlight our local
area with increased probabilities for severe weather.
Consequently, be sure to monitor for changes in the forecast
closely over the coming days and be thinking about your severe
weather preparedness plan!

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 951 PM CDT Thu Apr 24 2025

Low end VFR to scattered MVFR conditions currently present
across the local area. Rain will continue to build in from the
west bringing more widespread MVFR ceilings and visibilities
with it. Overnight, ceilings will drop to IFR for RST but should
hold off for LSE until 12Z. Around that time there are low
probabilities that both LSE and RST could see some LIFR ceilings
develop so have covered those possibilities with PROB30s. Rain
will exit to the east through the morning hours with visibility
reductions from mist/drizzle potentially lingering into the
afternoon before VFR conditions return for the evening. Winds
out of the northeast will continue through much of the period
between 6-12 kts before becoming more northerly tomorrow
afternoon.

&&

.HYDROLOGY...
Issued at 328 AM CDT Thu Apr 24 2025

Additional rain of .25 to 1.25" through Friday morning.  Some rivers
are currently elevated/flooding (The Black River and the Yellow
River). The HREF ensemble max precipitation is 1.5 to 2.5"  from
southeast Minnesota into western Wisconsin.  The latest 6-hr flash
flood is around 2.25 inches.  With the storms through early this
morning, amounts were mostly trace to .5", however some
embedded .5 to 1.5" MRMS radar estimates occurred on a local
basis. Thus, most areas should be OK with the amounts currently
forecast, however some flooding can be expected on a local basis
where the higher amounts occur and where rivers are already
elevated.

&&

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

&&

$$

DISCUSSION...Naylor/JAR
AVIATION...Barendse
HYDROLOGY...Zapotocny