596
FXUS63 KARX 271139
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
639 AM CDT Sat Apr 27 2024

.KEY MESSAGES...

- Drier conditions today. Strong to severe storms could develop
   this evening in northeast Iowa into far southwest Wisconsin.
   Large hail and damaging wind are the primary threats.

 - Widespread showers and thunderstorms likely on Sunday with
   expected rainfall totals between 0.5 and 1".

 - Active pattern continues next week with periodic disturbances
   moving through increasing rain chances.

&&

.DISCUSSION...
Issued at 352 AM CDT Sat Apr 27 2024

Severe Thunderstorm Potential This Afternoon/Evening:

Confidence continues to increase for today to be drier than previous
forecasts. This is due to weak shortwave ridging in between storm
systems. Gusty winds will continue into the afternoon across the
area as winds off the surface are between 25 and 30kts. This will
result in gusts between 30 and 35mph. Looking at the synoptic
setup for Saturday, a surface low is centered over the southern
Plains while in the Upper Midwest, a warm front pushes through
this morning leaving the area in the warm sector throughout the
day. As the afternoon approaches, a warm front lifts northward
associated with the next low, and almost stalls out and becomes
quasi-stationary somewhere in northeast Iowa and southwest
Wisconsin. Near this boundary, dewpoints in the low 60s, SBCAPE
and MLCAPE between 1500 and 2500J/kg, and good amounts of shear
will result in some severe threat for these areas during the
late afternoon and evening. Right now the focus area for severe
weather will be right along this boundary in northeast Iowa and far
southwestern Wisconsin. The main severe threat with these
storms will be damaging winds and large hail. If storms can
become surface based, then a tornado or two can not be ruled
out. As the atmosphere becomes more stable, the severe weather
threat will end. Scattered showers and thunderstorms will
continue and increase in coverage heading into Sunday as the low
moves towards the region.

Widespread Rain Sunday:

As the surface low gets closer widespread showers and thunderstorms
will take place. PWAT values are in the 95th to 99th percentiles.
These high percentiles indicate abnormally high PWATs, which will
range from 1.2 to 1.5". This will result in 0.5 to 1" of rain across
the area, with potential in far southwest Wisconsin for some totals
between 1 and 2". With the approach of the surface low and
shortwave there is some risk of strong to severe storms, but
confidence is low due to the widespread rain and storms which
might hinder destabilization. Rain will gradually lift off to
the northeast throughout the overnight period.

Active Pattern Next Week:

Next week is looking like another active period as the region ends
up being in a predominant zonal flow. This flow pattern will result
in periodic shortwave disturbances to bring more precipitation
chances throughout the week. With the current ensemble and
deterministic guidance, one shortwave moves through Tuesday with
another on Thursday.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 639 AM CDT Sat Apr 27 2024

Showers continue to lift north into northern WI early today with
drier conditions likely through the day. Additional
showers/isolated storms will lift north tonight, but there is
some uncertainty how quickly they approach I-90 and KRST/KLSE,
so have not explicitly mentioned. The southern fringe of a broad
IFR/MVFR shield may scatter/rise through the day, with a return
to VFR. Depending on the northward push of precipitation
tonight, MVFR ceilings may develop (40-70% chance) overnight.
Gusty southerly winds will shift southwest before becoming
northerly and diminishing tonight.

&&

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

&&

$$

DISCUSSION...Cecava
AVIATION...JM