615 FXUS63 KARX 071748 AFDARXArea Forecast Discussion National Weather Service La Crosse WI 1248 PM CDT Sun Sep 7 2025
.KEY MESSAGES...
- Warmer week ahead! Highs return to the 70s for most, pushing to around 80 for the end of the week.
- The risk for rain showers for late Monday through Wednesday has shifted northwestward, but southeast Minnesota into central WI could still see periodic showers.
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.DISCUSSION... Issued at 1248 PM CDT Sun Sep 7 2025
Temperature Trends for the Upcoming Week
Surface high pressure is transiting the region this afternoon and departs this evening. Low to mid-level warm air advection is already underway and continues for the next 24-36 hours. However, low temperatures tonight over western and central Wisconsin could still fall into the mid to upper 30s depending on the degree of decoupling that takes place. Have pushed lows down to the NBM 5-10th percentile in the sand bogs and central Wisconsin to account for this possibility. These temperatures would be supportive of patchy frost in favored locales.
High temperatures on Monday bounce upwards by 10 degrees compared to this afternoon, hitting the low to mid 70s, then slowly inch upwards into the mid to upper 70s by midweek. There isn`t any significant airmass changes on the docket for the remainder of the week with highs remaining in the upper 70s to low 80s.
Periodic Light Rain Showers to Start the Week
Increasing 850-750-mb theta-e advection late tonight could be enough to spark a few elevated showers west of the Mississippi River as hinted at by a number of 12Z CAMs. These showers will be battling lower tropospheric dry air, so have added sprinkle wording to the grids to account for this potential.
A surface baroclinic zone develops across the High Plains to start the work week, but fails to advance eastward through the week with upper level ridging amplifying overhead. Recent trends from the LREF ensemble suite are pulling the higher precipitation probabilities for Monday night into early Wednesday--which were over the region yesterday--back to the northwest and closer to the higher theta-e corridor. While the forecast is certainly not dry, yet, areas to the north and west of a Waterloo, IA to Wisconsin Rapids, WI line have a better chance (40-50%) of seeing light showers compared to those further south.
Moving towards the middle to end of the week, the strengthening upper ridge and resulting subsidence will limit the risk for showers and the NBM has come in predominantly dry.
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.AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1145 AM CDT Sun Sep 7 2025
CIGS: a few fair weather cu this afternoon followed by SKC conditions this evening through most of the overnight. Low/mid level warm air advection favors the development of a mid level VFR deck of clouds across IA overnight, shifting northeast across the TAF sites after 12z. A few hours of 4-5kft cigs likely Mon morning.
Caveat for KLSE - while fog impacts overnight are not anticipated (see section below), a layer of stratus could develop across the Mississippi river with decoupled winds potentially bringing those across the airport. A low probability at this time (
NWS ARX Office Area Forecast Discussion