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000
FXUS63 KARX 232004
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
300 PM CDT Tue Apr 23 2024

.KEY MESSAGES...

- Scattered showers and storms with small hail exit the area
  this evening.

- Cooler tonight into Wednesday. Low temperatures tonight will
  fall into the middle 20s to middle 30s.

- Active weather starting Friday with widespread rains
  through the weekend and some potential for severe storms
  at times...especially Sunday.

&&

.DISCUSSION...
Issued at 300 PM CDT Tue Apr 23 2024

Tonight through Thursday

Mid-level trough passing through the western Great Lakes this
afternoon with colder air aloft, decent mid-level lapse rates, but
limited CAPE to work with was leading to low based, scattered
convection. Some small hail reports but activity will wain quickly
as this wave passes and with loss of heating.

Passage of wave will lead to a quiet couple days with northwest
flow. Dry regime will allow for another chilly night with sub
freezing temperatures expected for parts of the area. Winds are
expected to remain up overnight so short term freeze risk is about
main concern versus frost. Even though temperatures likely to be
below freezing for a brief period of time, may need another headline
given setup.

With area in between systems next couple days, main concern will be
watching for any fire weather risks given continued dry airmass.
Nearly full sun and atmospheric mixing could drop afternoon relative
humidity values below 30 percent (and possibly near 20 percent) on
Wednesday. The good news is lighter winds and lower fine fuel
numbers expected, which should limit overall risk. Winds do increase
on Thursday as surface ridge exits, but so does the cloud cover and
low level moisture advection, limiting risk. Parts of central
Wisconsin would be last to notice these limiting factors so again,
will have to watch trends.

Friday through Tuesday

Larger pattern shift taking place late week will lead to a period of
more active weather, with widespread rains a given and a window or
two where severe storms could impact area. Models have two main
waves resolved that will have their biggest impact on our region
Friday and again Sunday.

Starting Thursday night we will see impressive moisture advection
northward across central CONUS with broad lift ahead of approaching
wave. This will lead to dramatic increase in convection coverage
that will move into the local areas Friday. Short wave will take on
a negative tilt as it ejects into the Plains but still looking like
timing will favor warm sector and higher risk of severe storms to
the southwest of us. Amount of convection could play into how things
evolve after that even as wave is forecast to lift northeast and
weaken heading into Saturday. Ensembles continue to suggest lower
confidence in surface based instability working into immediate area.

Saturday could be a slight lull in the extent of convection between
waves, but given the front could be layed up over area and no big
reprise in precipitable water values, redevelopment during daytime
is a possibility adding to the overall rainfall threat.

Even though we are talking about Day 6, the setup for Sunday might
be the most interesting at this point. Another strong wave progged
to eject out of the southwest and approach western Great Lakes.
Corridor of moisture ahead of this wave and previously mentioned
front will continue to parade convection. Track and more of a
neutral tilt wave suggest a less occluded but well defined frontal
structure working across the forecast area. Again, numerous days out
and lots of factors to resolve, but even model blends hint at well
defined warm and cold fronts leaving us in the warm sector favoring
a higher risk for severe storms. Will certainly have to watch trends
as we draw closer.

Examining total rainfall from Friday into early Monday via ensembles
suggests many areas could be in that 1 to 2 inch range. Convection
always makes exact amounts fickle but given we could have several
rounds of showers and storms, still feel fairly certain that
everyone will see another soaking bout of rain. Rivers and drainage
areas handled last event /Tuesday April 16th/ well but would still
expect rises on area rivers at the very least, and possibly a few
locations getting into action stage.

Looking further ahead, mean heights start to build for the Midwest
suggesting we could start another warming trend.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 114 PM CDT Tue Apr 23 2024

Clouds have increased across much of the region with isolated-
scattered showers developing across portions of MN and WI this
early afternoon. Observations show mainly VFR conditions and
have maintained that through the TAF period. With the developing
showers, have included a short window of -shra at KLSE and KRST
this afternoon, though coverage of these showers could be a
challenge to this. Will continue to monitor and make short term
adjustments if necessary. Increased west/northwest winds
continue with gusts 20 to 30 kts possible this afternoon and
early evening. Clouds are expected to begin to clear out tonight with
winds easing up and turning more northeast by the morning hours
Wednesday.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Freeze Warning from 2 AM to 8 AM CDT Wednesday for WIZ032-033.
MN...Freeze Warning from 2 AM to 8 AM CDT Wednesday for MNZ079-
     086>088-094>096.
IA...None.

&&

$$

DISCUSSION...Shea
AVIATION...EMS