065
FXUS63 KARX 300335
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1035 PM CDT Wed May 29 2024

.KEY MESSAGES...

- A recurrence of valley fog is favored tonight into early
  Thursday morning.

- Periodic Showers and Storms from Friday into Wednesday. Maybe
  some stronger storms from Tuesday into Wednesday.

&&

.DISCUSSION...
Issued at 213 PM CDT Wed May 29 2024

Fog tonight into early Thursday morning:

After Wednesday morning saw fog develop in many of the forecast
area`s river valleys and the cranberry bog area, a repeat is favored
tonight. Fog seems to comport well with the overall pattern, where
surface high looks to become centered over NE WI as an upper wave,
located over eastern Ontario, exits over MI, leading to very light
winds at the surface. With skies expected to be clear, excellent
radiational cooling should result in fog. Potential failure mode may
be winds a bit too strong at the top of the boundary layer and the
light northeasterly winds this afternoon bringing in enough drier
air to overcome the abundant surface moisture that is present due to
the well above normal rainfall over the past few weeks.

Friday through Monday Night: Periodic Showers and Storms

A longwave ridge will move east of the area on Thursday night.
As this occurs, a shortwave trough will move east through the
area on Friday and Friday night. 0-1 km mixed-layer CAPES ahead
of this trough are only up to 250 J/kg. 0-3 km shear remains in
the 20 to 35 knot range and the 3-6 km shear is generally less
than 15 knots. Due to this, not expecting to see any severe
weather.

For the remainder of this period, the 500 mb flow will become
zonal. Embedded shortwave troughs in the flow pattern will
bring periodic showers and storms. One will move through area
on Saturday night and another one from Sunday afternoon into
Sunday night. While the 0-3 km mixed-layer CAPES climb up to
1000 J/kg, the 0-6 km shear remains weak, so not anticipating
organized severe weather with either these systems.

Tuesday into Wednesday: Maybe Some Stronger Storms

A much stronger shortwave trough will move through the region. While
the 0-3 km mixed-layer CAPES climb up to 1000 J/kg, the 0-6 km
shear remains weak. From looking at just these parameters, it
does not look that favorable for severe weather. However, some
of the ensemble members are showing that this this system will
be potentially negative tilted and this would enhance the 0-3 km
and 0-6 km shear. In addition, the Colorado State machine
learning has up to a 15% chance of severe weather, so this
system bears watching.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1035 PM CDT Wed May 29 2024

Main taf concern is fog development in river valleys tonight.
With light winds...clear skies and an inversion developing
tonight...fog will possibly form in the river valleys after 09z
Thursday. However...winds do increase near the inversion over
10 knots and the region is slightly drier near the surface
compared to the last couple of nights/evenings. This will
inhibit fog development in river valleys. At this time...have
kept patchy fog in river valley and MVFR visibility condition at
LSE taf site. Otherwise...surface ridge will dominate the
area and VFR conditions will prevail. Southerly wind speeds
will increase to 10 to 15 knots late Thursday morning at both
taf sites. Then...wind speeds are expected to diminish near 10
knots or less after sunset Thursday evening.

&&

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

&&

$$

DISCUSSION...Boyne/Ferguson
AVIATION...DTJ