-- Discussion containing changed information from previous version are highlighted. --
672
FXUS63 KARX 292339
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
639 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 /00Z TAFS THROUGH 00Z FRIDAY/...
-- Changed Discussion --
Issued at 632 PM CDT Wed May 29 2024

VFR conditions are favored through this TAF period across the
area. The chances for valley and river fog tonight have
decreased (roughly 10% chance of 1sm or less east of the
Mississippi) as drier air moves in from the NE. Surface high
pressure will bring light winds and good radiational cooling
tonight; however, 20kt winds 300-500ft off the surface is a
strong limiting factor as well as the 25 to 30 degree dewpoint
depressions. Will keep a 3sm br in at LSE for now and reassess at
the 06Z issuance.
-- End Changed Discussion --

&&

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

&&

$$

DISCUSSION...Boyne/Ferguson
AVIATION...JAW