469 FXUS63 KARX 202326 AFDARXArea Forecast Discussion National Weather Service La Crosse WI 626 PM CDT Sat Sep 20 2025
.KEY MESSAGES...
- Scattered showers and thunderstorms through the weekend with localized heavy rain at times.
- Storm chances continue Monday with concerns for strong storms affecting the central CONUS.
- Temperatures stay near normal with highs in the low to mid 70s through much of next week.
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.DISCUSSION... Issued at 152 PM CDT Sat Sep 20 2025
Periodic Showers and Storms Through the Weekend:
The upper level low that has been giving us showers and storms over the last few days is gradually moving off to the northeast. Currently, the low is situated over over the CWA. With this location and increasing low level lapse rates, the best instability will build in central Wisconsin. While some instability builds in southeast Minnesota and northeast Iowa, the higher values (1000 to 1500 J/kg of MLCAPE) are located in central Wisconsin. As a result, scattered showers and storms will be possible this afternoon and evening. With the upper level low overhead, there may be some potential for some funnels to form this afternoon with light southerly winds in the lowest 10 to 15kft. The one caveat to this is that a boundary would need to be present to help increase the funnel potential. Another shortwave moves down Sunday afternoon increasing shower and storm potential later Sunday afternoon into the overnight period. Overall rain amounts through the weekend are generally less than 0.4 inches. Locally higher amounts of up to 1 inch will be possible especially in central Wisconsin and in portions of southern Minnesota.
Storm Potential Next Week:
A shortwave moves into the Upper Midwest as a frontal boundary sits near the Upper Midwest River Valley. This will allow instability to build in during the afternoon. While low level shear is decent (25 to 30 kts), low level lapse rates are not impressive, mostly around 6 C/km. Better instability and forcing remains to the south of the CWA. Despite this, machine learning severe probabilities give a 5 to 15% chance for severe weather to occur, mainly south of I-90. This will be something to watch as we get through the weekend.
For the rest of the week, ensemble guidance continues to show a trough digging down into the central CONUS. Over the past couple of days, ensembles have brought this trough further south, lowering our precipitation chances (15 to 25%) to just northeast Iowa and southern Wisconsin. If this trend continues a mostly dry week could occur. Temperatures over the next 7 days are staying mainly in the low to mid 70s.
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.AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 625 PM CDT Sat Sep 20 2025
Scattered showers/storms continue across portions of the area this evening, but are expected to be on the downward trend with sunset. Otherwise, VFR conditions are largely expected to prevail into the overnight hours. Patchy fog/mist is possible again overnight for portions of the region, primarily western Wisconsin and northeast Iowa, resulting in MVFR to IFR visibilities and ceilings. Not confident enough to include mentions of fog/mist at the TAF sites, but could see MVFR ceilings overnight where fog does not develop. Additional showers/storms cannot be ruled out Sunday afternoon, but coverage is not expected to be as widespread as compared to today.
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.ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None.
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DISCUSSION...Cecava AVIATION...Falkinham
NWS ARX Office Area Forecast Discussion