718
FXUS63 KARX 290837
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
337 AM CDT Mon Apr 29 2024

.KEY MESSAGES...

- Cooler weather today, with a rebound to above average
  temperatures for Tuesday and Wednesday. Seasonal temperatures
  for the remainder of the week.

- Several more rounds of showers and storms are lined up for
  Tuesday and late Wednesday through Friday. Overall severe
  threat looks low at this time, however the likelihood of
  widespread rainfall is high (between 60 and 90%) with these
  systems.

&&

.DISCUSSION...
Issued at 337 AM CDT Mon Apr 29 2024

Today through Tuesday:

The surface low continues to move off to the northeast during
the day. The progression of the low slows a little bit, allowing
for some showers to be possible for areas along and north of
I-94 through the day. Shortwave ridging will move over the area,
however with low stratus hanging around for most of the day,
temperatures will be on the cooler side. Heading into Tuesday, a
compact shortwave trough will dip down into the Central Plains.
This will be our next chance at seeing some precipitation.
Accompanying this shortwave will be dewpoints ranging from
around 50F to the low 50s, especially in northeast Iowa and
southeast Minnesota, a 50kt low- level jet, and good shear. The
one ingredient that is missing is instability. The greatest
instability lies west of the area in northwestern Iowa. There is
still some uncertainty in how far north the instability and
moisture transport gets. This will help in determining if severe
weather will be possible across the area. Combining the above
ingredients with recent model guidance that has a few hundred
joules of SBCAPE across northeastern Iowa and southeastern
Minnesota, SPC has gone with a Marginal risk (level 1 of 5) in
this area. Even though the severe threat is low, general showers
and thunderstorms seem likely during the evening and early
overnight hours on Tuesday into Wednesday.

Active Pattern Continues:

By Wednesday, a longwave trough shifts eastward. This will allow for
deeper moisture transport and warm sector spreading northward.
Periodic precipitation will be possible given this regime through
the end of the week. It is too early to tell if severe weather will
be possible, however the current guidance gives the Central Plains
the best chance at seeing severe weather through the week. That
being said, rainfall probabilities continue to increase. They
have increased slightly from the previous forecast. The Grand
Ensemble gives a 50% to 70% chance of at least 0.5" and 25% to
40% of at least an 1" occurring Thursday into early Friday.


&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1105 PM CDT Sun Apr 28 2024

MVFR/IFR conditions are expected through much of the TAF period as
low cigs persist with a passing surface low to our northeast. As the
the low progresses, an additional brief round of isolated
showers, perhaps a few storms, will progress through the region
around the 05z to 10z timeframe. However with instability being
very minimal, confidence remains low in coverage. As the low
progresses closer to our region, winds will diminish some which
combined with some fairly solid low-level moisture could result
in fog formation across the region during the pre-dawn hours.
Much of this is contingent on how any showers and storms
manifest overnight which could mitigate this potential. As a
result, have some visibility reduction mention in the TAF but
will monitor for any changes. Otherwise, winds will increase to
around 15 kts with a tightening surface pressure gradient
throughout the day tomorrow as the low ejects northeast.

&&

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

&&

$$

DISCUSSION...Cecava
AVIATION...Naylor