


Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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130 FXUS63 KARX 071737 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1237 PM CDT Mon Jul 7 2025 .KEY MESSAGES... - Storm chances overnight through Tuesday morning. Scattered cellular storms through Tuesday. - Storm chances return overnight Thursday through Friday. && .DISCUSSION... Issued at 302 AM CDT Mon Jul 7 2025 Storm Chances Tonight Through Tuesday: Building heights usher in a dry forecast today with low level moisture transport firing off convection in the Northern Plains. This line of convection follows a perturbation advecting east- southeast over the Canadian border on early morning water vapor imagery loops into tonight. High resolution model guidance agrees on a weakening trend as storms approach the Upper Mississippi River Valley late tonight into early Tuesday morning concurrent with the loss of diurnal heating and weakening moisture transport which can be attributed to splitting of synoptic forcing. The resultant split of higher confidence in precipitation (50%) chances passes to the north and south of the forecast area; tied to the better forcing from the aforementioned trough to the north and higher low level moisture transport and a subsequent Rocky Mountain Low to our south. The overnight timing limits overall instability, i.e. limiting storm potential. Precipitation chances increase through early Tuesday morning along a weak frontal boundary as the lagging trough axis passes by. This weak forcing/boundary will limit shear and subsequent storm potential. Any frontal passage becomes washed out with diurnal heating which also keeps pop up storms possible through Tuesday. Increased instability with little to no deep layer shear keeps storm chances to a cellular mode. Thus, nothing in the way of severe expected. Dry Midweek; Storm Chances Thursday Night through Friday: Building mid level heights (LREF) provide a /mostly/ dry midweek with higher precipitation chances returning overnight Thursday into Friday morning. Strongest low level moisture transport lifts through the Central to Northern Plains on Thursday, potentially grazing precipitation chances along our western peripheral counties in northeast Iowa and southeast Minnesota Thursday night. Disagreement in LREF cluster analysis stems from the strength of Tropical high pressure and resultant peripheral eastern extent of low level moisture penetrating through the Mississippi River Valley. Regardless, higher precipitation chances greet the Upper Mississippi River Valley overnight through Friday morning. Storm chances accompany frontal passage through Friday as a long wave trough with an axis bifurcating the central CONUS advects east.Much to be ironed out still as LREF cluster probabilities for 1000 J/kg of MU/SBCAPE vary widely due to variation in location and depth of said trough. Regardless of the behavior (i.e., amplification) of the trough, clusters show a comma head of 0.5" mean rainfall from the Northern through the Southern Plains. Lastly, the high res PANGU, machine learning severe weather models keep higher probabilities(15%) for severe to our south and west. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1235 PM CDT Mon Jul 7 2025 MVFR ceilings across western WI improve to VFR by mid-afternoon with an isolated shower or storm south of an OVS to DEH line this afternoon. A decaying line of storms moves in between 06-15Z, but confidence in having restrictions is low at any given site. Winds will be light and variable today and then back to the northwest at around 5 kts for Tuesday. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...JAR AVIATION...Skow