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000
FXUS63 KARX 250158
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
855 PM CDT Wed Apr 24 2024

.KEY MESSAGES...

- Frost/Freeze Headlines are in effect for portions of southwest
  Wisconsin tonight through early tomorrow morning.

- An active weather pattern returns for the end of the week
  into the weekend with periods of rain and thunderstorms. Will
  continue to refine details revolving around the risk for
  strong to severe storms.

&&

.DISCUSSION...
Issued at 256 PM CDT Wed Apr 24 2024

Tonight - Tomorrow:

Surface high pressure will continue to slide eastward through the
period. With temperatures dropping around freezing to sub-freezing
for some areas across southwest WI, have issued a frost/freeze
headline for tonight through 8 AM Thursday morning. Another dry day
is expected tomorrow with afternoon relative humidity values
dropping into the 20 to 30 percent range, lowest east of the
Mississippi River. In addition, as we find ourselves in between the
departing high and an incoming low pressure system, southeast winds
will begin to increase across the region, especially as we head into
tomorrow night and through the weekend.

Tomorrow Night - Weekend:

As has been advertised, an amplified upper level pattern is forecast
for the end of the week and weekend as upper level ridging builds to
the east and troughing to the west. Will be keeping an eye on a
couple of shortwaves moving across the region, bringing increased
chances for rain and thunderstorms across the forecast area through
the period. Overall, precip amounts

The aforementioned trough over the southwest U.S. on Thursday is
forecast to take on a negative tilt as it moves into the Central
Plains by Friday. In turn, a surface low is forecast to lift
northeast from the Central Plains towards the Great Lakes Friday
through Friday night, with an associated surface warm front
lifting northward ahead of the low. Moisture will begin to lift
northward Thursday night into Friday with PWATs increasing to 1-
1.5" (90th percentile of climatology per NAEFS/ECMWF). This
along with broad lift will allow for increasing rain and
thunderstorm coverage across the forecast area Friday. There
remain some uncertainties in the progression of the warm front
and how earlier convection may have an impact. Even so, guidance
suggests timing/location of the warm sector may be displaced to
our south/southwest and in turn keeps the higher risk of severe
weather southwest of the local forecast area. However, SPC does
have portions of SE MN, NE IA, and SW WI in a marginal risk at
this time, so be sure to stay up to date with the latest
forecasts.

The shortwave trough and surface low will continue to exit and
weaken northeastward Saturday, leaving a boundary draped across the
forecast area. There is some indication for a short break in
precipitation for some Saturday. However, we will have to watch for
redevelopment later in the day with plenty of moisture still in
place. Model forecast soundings show capping in place through early
Saturday, but if that can be eroded through the day some
surface based convection may be possible east of the boundary.

Another shortwave trough and surface low approach the region from
the southwest Saturday night into Sunday. This will bring additional
rain and thunderstorm chances to the forecast area. Details remain a
bit less certain at this time, but this will be another time period
to keep an eye on favorable conditions for severe weather. To note,
SPC`s Day 5 Severe Weather Outlook does highlight portions of NE IA
and SW WI. Overall, with several rounds of precipitation over a few
days ensemble guidance suggest rainfall amounts may fall in the 1 to
2-2.5 inch range, with probabilities for >= 3" remaining around 10-
20%. With the convective nature there will likely be some
variability in exact amounts across the area, with some locally
higher amounts possible. Will keep watch for any response/impacts
to rivers with increased rainfall totals over the coming days.


Next Week:

Heading into next week, upper level ridging looks to
build in across the central CONUS. There is still plenty of spread
among ensemble solutions, but there is signal for a warm up into mid-
week with the temp trend leveling out for the start of May.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 855 PM CDT Wed Apr 24 2024

CIGS: SKC/SCT conditions through the period. Next round of
impactful/low cigs move in Friday morning as a spate of weather
systems promise widespread rain/a few storms for the weekend.

WX/vsby: no impacts expected. Next shot for rain with associated
vsby restrictions moves in Friday morning with periodic -shra and a
few ts through the weekend.

WINDS: light southeasterly tonight increasing by mid morning Thu. A
few gusts upwards of 20 kts for KRST. A stronger period of winds are
expected for Friday through Sunday as a couple weather systems march
across the region.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Frost Advisory from 2 AM to 8 AM CDT Thursday for WIZ053-054-
     061.
     Freeze Warning from 2 AM to 8 AM CDT Thursday for WIZ055.
MN...None.
IA...None.

&&

$$

DISCUSSION...EMS
AVIATION.....Rieck