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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KARX 202324
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
624 PM CDT Sat Apr 20 2024

.KEY MESSAGES...

- Frost/freeze risk remains high tonight and again Sunday
  night.

- Low RH and breezy winds may lead to elevated fire weather conditions
  Sunday/Monday afternoons.

- Shower chances return later Monday into Tuesday, but amounts
  look light (>70% chance for less than 1/4").

&&

.DISCUSSION...
Issued at 146 PM CDT Sat Apr 20 2024

Tonight-Sunday:

Clearing skies will occur overnight as the large upper level trough
across eastern Canada moves east and surface ridging edges closer
from the plains. It will be another chilly night with high
probabilities for overnight lows near/below freezing area-wide, and
medium (40-70%) chances for lows at or below 28F for non-river
valley locations west of the Mississippi River and 50-90% chances
for areas north and east of I-94. As a result, a freeze warning has
once again been issued for our susceptible counties tonight. Sunday
night will not be quite as cold, but low to mid 30s likely will be
common once again, especially slightly warmer valleys, so
additional headlines may be needed for one more night.

A mostly sunny and milder day is on tap for Sunday. High temps
should approach seasonable values in the 50s to low 60s. However,
with the dry airmass in place, elevated fire weather conditions are
possible. See the fire weather section below.

Monday-Tuesday:

Mild conditions are expected Monday with increasingly gusty south
winds ahead of a low pressure system passing to the north that will
drag a cold front through Monday night. The strongest winds are
expected in the more favored open areas west of the Mississippi
River with 20 to 40% chances for gusts to 40 mph west towards I-35
by Monday afternoon. Showers are possible by later Monday/Monday
night (50-80% chance, highest across Wisconsin) in the warm
advective regime ahead of the front with additional shower/isolated
thunder chances into Tuesday along with gusty (30 to 40 mph) winds
as the main shortwave trough/cold pool aloft drops through the area
and winds shift northwest. Moisture transport/instability continue
to look rather weak ahead of the system, limiting thunder chances
and rain amounts. Global ensemble probabilities for 0.10" of rain
are only 30 to 50% southwest of I-94 and 50 to 70% to the northeast,
while probabilities for 0.25" have decreased relative to yesterday
to 20 to 40% northeast of I-94.


Wednesday-Saturday:

Mid-level ridging will edge east for mid to late week with deeper
southwest flow forecast to develop by late week into next weekend.
Dry and relatively seasonable conditions are anticipated for mid-
week ahead of the ridge axis. As moisture returns northward late in
the week and into next weekend and a series of shortwave troughs
eject from the Rockies, a warmer, more unsettled regime is expected.
However, there is still plenty of uncertainty in the timing/strength
of these waves, which will impact precip timing, temps, and amount
of instability available. The global ensemble suite shows increasing
spread in high temps towards next weekend, owing to the lower
predictability in details of the pattern evolution.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
-- Changed Discussion --
Issued at 621 PM CDT Sat Apr 20 2024

Skies will continue to clear tonight and will remain mostly
clear through the rest of the TAF period, with VFR conditions
expected. On Sunday, expect another day with winds out of the
northwest around 10 to 15 kts.
-- End Changed Discussion --

&&

.FIRE WEATHER...
Issued at 146 PM CDT Sat Apr 20 2024

Elevated fire weather conditions may develop Sunday afternoon due to
a combination of mostly sunny skies, very dry air and breezy winds.
Deep mixing to near or above 800 mb by afternoon will promote
occasional gusts around 20 to 25 mph from the west to northwest,
although sustained winds will likely be closer to 10 to 15 mph.
However, the dry airmass and quick mix-out will allow RH to fall
rapidly by mid to late morning, bottoming out from 20 to 30% for
most areas. Slightly lower values cannot be ruled out if
warming/mixing is slightly greater than forecast, which is possible
given the favorable environment.

Southerly winds will increase ahead of an approaching front on
Monday. The strongest winds will likely be west of the Mississippi
River with the lowest RH (25 to 30%) across portions of
Wisconsin. With warmer temps in the low to mid 60s and drying
fuels, elevated fire weather conditions are again possible,
especially into Wisconsin.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Freeze Warning from midnight tonight to 8 AM CDT Sunday for
     WIZ032-033-041-053>055-061.
MN...Freeze Warning from midnight tonight to 8 AM CDT Sunday for
     MNZ079-086>088-094>096.
IA...Freeze Warning from midnight tonight to 8 AM CDT Sunday for
     IAZ008>011-018-019-029-030.

&&

$$

DISCUSSION...JM
AVIATION...JAW
FIRE WEATHER...JM