310
FXUS63 KARX 200959
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
500 AM CDT Sun Apr 20 2025

.KEY MESSAGES...

- Soggy today into Monday morning with widespread rain spreading in
from the south this afternoon. Amounts in excess of 1" (60 to 100%
chances in the HREF) with spotty 10% chances to exceed 2". Bulk of
the rain falls tonight.

- Milder temps and periodic rain chances for the new week. Wednesday
is trending as the warmest, and driest day. Weekend also favoring
drier conditions.

&&

.DISCUSSION...
Issued at 215 AM CDT Sun Apr 20 2025

TODAY-MONDAY: Soggy. Widespread rain with the bulk falling tonight.
Amounts generally from 1 to 1 1/2". Breezy.

Upper level shortwave trough, currently churning across the TX
panhandle (per latest watervapor satellite imagery), remains on
track to lift northeast today. The trough acquires a negative tilt
and strengthens (thanks in part to a coupled, curved 300 mb jet) as
it moves over the upper mississippi valley overnight. The
accompanying sfc low is set to move over southern WI by 12z Mon. The
EPS is just shade slower and stronger compared to the GEFS mean
while also hinting that it still might be a tad too fast (the
majority of its members are a bit more west, slower). That said,
those nuances won`t have much/if any impact on the sensible outcomes
- as long as the favored track holds.

Leading the system across the region is hefty low level
thermodynamics with a strong, sloping Fgen response. Appreciable QG
convergence for the night time hours too.

Loads of forcing, but not much/if any instability to work with as
the system`s warm front is set to hold to the south. Thunder threat
looks minimal, elevated, and would hold south of I-90.

Appreciable moisture transport will feed all that forcing with a
deep layer of moisture in the 925:700 mb layer driving north across
the sfc warm front and wrapping westward into the storm`s
deformation region. NAEFS/EC PW anomalies are +1 to +2 tonight while
EFIs for QPF continue to increase run to run, roughly 0.8 to 0.9
tonight with a non-zero SoT. GEFS and EPS QPF continue to paint
around 1/2" of rain for the "basement" and 2+ inches for the
"attic". Means have gone up over the past few days too, mostly
around 1 to 1 1/4" now, much of which falls tonight.

Not anticipating any flooding issues (at this time) considering the
recent dry conditions. That said, some rises on area rivers/streams
should be expected. Ponding on roadways, other low lying areas will
also occur.


TUE-INTO THE WEEKEND: milder, periodic shower/storm chances

Long range guidance continues to favor increasing upper level
heights/broad ridging as we move through the new week. Fairly
progressive with a larger amplitude ridge progged to build across
the upper mississippi river come the weekend. The ridge will be a
deterrent to rain chances, but prior to that, the EPS and GEFS
continue to depict a few shortwaves and related surface reflections
that could bring periodic shower/storm chances to the local area.

The first one of note is a shortwave progged to kick east out of the
PAC NW to across the northern plains by Tue night. A very consistent
signal in the GEFS and EPS, and also consistently north of the local
forecast area. However, a sfc front will run southward of the upper
level feature with the low level jet/moisture transport nosing
into/along the boundary. Some instability in the mix, generally
south of I-90 and could be more elevated (depending on timing of the
convection and positioning of boundaries). This mix should lead to
area of showers, perhaps a few storms.

Thursday and Friday is another period the GEFS and EPS highlight for
rain chances. A mix of northern/southern stream shortwave activity,
related surface boundaries, along with branches of the low level
jet/moisture transport and instability will all have their roles.
How it comes together, timing and location, are more nebulous. "All"
the ensemble members in both models paint areas of QPF for the
region, but with enough variety that trying to pin-point a time/area
for higher chances, more impacts, is problematic this many days out.
Expect refinement on the when/where as we move through the new week.

As for temps, the increasing heights a loft followed by a stouter
shortwave ridge will allow for seasonable to mild air to pool
northward. EPS and GEFS suites have about 75% of their members
at/above normal - highs topping out in the 60s. Wed is a day both
highlight for the warmest temps of the work week - abetted by a dry
forecast. Both paint 10-30% chances for 70+ degree highs along/south
of I-90. Looking farther out the long range guidance continues to
favor at/above normal temps through the weekend into early next
week.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 500 AM CDT Sun Apr 20 2025

CIGS: increasing and lowering clouds from the south today.
Expectation is to drop into MVFR by late afternoon, then IFR
tonight. The low cigs should linger through Mon morning with
improvement to MVFR in the afternoon, scattering out toward 00z Tue.

WX/vsby: Rain spreads in from the south for the afternoon,
persisting into the overnight hours. Vsbys from 2-4SM with the rain.
Amounts of 1+" likely at KRST and KLSE.

WINDS: east winds will shift to northeast tonight then northwest Mon
morning with the passage of a sfc low. Gusty from the afternoon into
Mon afternoon (low 20 kts).

&&

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

&&

$$

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