Sunrise 6:04 AM   Sunset 8:10 PM Moonrise 11:41 PM   Moonset 6:52 AM

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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.

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