801
FXUS63 KARX 190958
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
500 AM CDT Sat Apr 19 2025

.KEY MESSAGES...

- Widespread rains from Sunday afternoon into Monday. Amounts from
3/4 to 1 1/4" on average currently expected. Wettest period Sun
night.

- Milder temperatures return next week (highs mostly in the 60s
from Tue on) with periodic rain chances.

&&

.DISCUSSION...
Issued at 200 AM CDT Sat Apr 19 2025

SUN/MON: widespread rain, perhaps a storm or two. Bulk of the rain
favored to fall from late afternoon through the overnight Sun.

The EPS and GEFS remain in solid agreement with lifting a shortwave
trough out of the desert southwest today, developing a negative tilt
as it spins over the upper mississippi river valley by 12z Mon.
Models not currently favoring a closed upper level low, but
cyclogenesis is ongoing as it moves in, thanks in part to
interaction with a curved 300 mb jet. The mean sfc low placement in
the GEFS and EPS is over southwest WI at 12z Mon. This is a shift
southeast for the EPS from some previous runs. Also, tHe majority of
its members in its most recent model run suggest a slower and
further west positioning. As for the GEFS, it too shows some
differences - slower, faster, north and south for the low. So still
some indecision in where the storm may track, but the overarching
scenario is to bring the storm across/near the local forecast area,
and widespread rainfall.

Speaking of rain, pronounced push of low level moisture on a 50 kt
850 mb jet set to nose into southern/central WI Sun evening,
rotating westward into the low pressure system`s deformation region.
NAEFs and EC anomalies are approx +1 to +1.5 for PWs. However, the
EFIs for QPF have increased over the past couple runs, pushing
upwards of 0.7 and continuing a non zero SoT. It`s a moist airmass
for April, perhaps not exceedingly so, but brings the potential for
higher end rain amounts. And as for amounts, there has also been an
uptick in potential amounts in the long range guidance as the EPS
and GEFS suggest 1/2" as a basement and upwards of 2+" for the
"attic". Means in the GrandEnsemble range from 3/4 to 1 1/4" and
look reasonable in this setup.

Even with the soaking rains some received yesterday, we have today
to dry out and it has been relatively dry - so we can take some
rain. Expect some runoff into area waterways, and if more "high end"
rainfall were to be experienced, perhaps some in bank rises.

Instability is lacking locally with the currently favored storm
track. A few storms possible across northeast IA/southwest WI, but
not expecting severe weather.

One more consideration is the potential for snow. Enough cold air on
the north side of the low could mix in snow for locations north of I-
94, especially if there is a shift southeast in the storm track. Any
accumulations would hold to hold/grassy surfaces, would be minor at
best, and wouldn`t last very long.


TUE INTO NEXT WEEKEND: warming (highs pushing back into the 60s for
most, perhaps some 70+ here and there). Periodic precipitation
chances.

Upper level height increases with mostly zonal flow takes over post
the Sun/Mon storm system. Long range guidance then favors broad
upper level ridging as we move into the following weekend. So, after
the cool conditions of the next few days expect milder/warmer air to
return to the region. 50-75% of the EPS and GEFS paint 60+ degree
highs from Tue on, with a handful suggesting some locations will
venture into the low 70s. The GrandEnsemble sits roughly from 5 to
20% for 70+ degree highs south of I-90. However you choose to "slice
and dice" the numbers, the probabilities (and confidence) continues
to trend "up" for a period of above normal temps next week.

While the ridging a loft will work against rain chances for the
latter half of next week, prior to that, the zonal flow will allow
for perturbations to spin across/near the forecast area.

One feature the GEFS and EPS have been depicting is a shortwave
trough driving across the northern plains then over the upper
mississippi river valley for Tue. Return flow on the low level
jet/moisture transport along a sfc front extending southward from
the shortwave should be enough to spark an area of showers/storms.
More bits of upper level energy could bring rain chances for Thu/Thu
night. More differences between the EPS/GEFS in timing and strength
of the various weather elements, but most of their members
(respectively) want to drop some QPF on/near the local forecast
area.


&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 500 AM CDT Sat Apr 19 2025

CIGS: bkn high clouds will exit later this morning leaving mostly
SCT/SKC conditions for the rest of the day, through tonight. Clouds
will be on the increase from the south Sunday, with a steady
lowering into MVFR/IFR Sun night.

WX/vsby: no impacts expected. Widespread rains return later Sunday
afternoon, persisting into Monday morning. Vsby reductions of
IFR/MVFR expected.

WINDS: northwest around 10 kts today. Light/vrb this evening
becoming southeast and picking up a few kts toward 12z Sun.

&&


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

&&

$$

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