Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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113 FXUS63 KARX 021737 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1137 AM CST Tue Dec 2 2025 .KEY MESSAGES... - Light snow chances (20-40%) tonight and into Wednesday morning. Snow accumulations of a trace to 1/2" possible along and north of I-90. - Very cold Wednesday night and into Thursday with wind chills of 10 to 25 degrees below zero Thursday morning. High temperatures on Thursday will remain in the single digits to lower teens for most. - Additional snowfall possible Friday thru Saturday night. Probabilities are currently low (10-40% chance) for accumulations for an inch or greater across the area. && .DISCUSSION... Issued at 321 AM CST Tue Dec 2 2025 Today - Thursday: Light Snow Tonight, Very Cold Thursday GOES-19 water vapor imagery and 02.06z RAP 500mb heights depict a departing upper-level shortwave trough that will continue to push east towards the Atlantic Coast. Behind this trough, northwesterly flow situates itself across the local area for the day today with temperatures falling to around the 10 degree mark. Given the shallow cold air advection and relatively calm winds overnight, would expect some freezing fog formation early this morning given the snowpack. While probabilities in the recent HREF are low (10-30% chance) for 1/4-mile visibilities, would not rule out some pockets of this especially given that Oelwein, IA has already observed 1/4 mile visibilities. Otherwise, limited mixing and northwesterly flow will keep our skies mostly cloudy with temperatures remaining below normal with highs in the lower to middle 20s for today. As we head into the overnight, a surface cold frontal passage will instigate an area of light snow out ahead of it. Overall the forcing is not overly impressive but with ample saturation, some of the CAMs develop snow overnight. The probabilities for measurable snowfall in the 02.00z HREF are modest (30-60% chance) near and north of I-90, however for amounts greater than 0.5" are very low (0-20% chance). Consequently, would expect some light snow to be around but accumulations will likely be kept to only a few tenths tonight. The bigger story as this front passes through will be the sharp drop in temperatures. With high pressure building west of the local area, this subsidence will allow cloud cover to clear out which will allow for efficient radiational cooling Wednesday night and into Thursday morning. As a result, median low temperatures during this period in the NBM fall below zero areawide with even some potential for temperatures to fall below minus 10 degrees across portions of southeast MN. With still a lingering surface pressure gradient, surface winds at around 10 mph will allow wind chills to fall to 10 to 25 degrees below zero. With the passage of the upper-level trough that the aforementioned surface cold front was associated with, reinforcing cold air advection in northwesterly flow will keep highs on Thursday quite cold with median high temperatures in the NBM only in the single digits to lower teens across the area. So be sure to wear multiple layers and dress appropriately, particularly if heading out on Thursday morning. Friday - Sunday: Additional Snow Chances By the time Friday rolls around, upper-level flow trends slightly more zonal which in turn will allow our temperatures to "rebound" slightly with highs back into the 20s for Friday. The main feature that will be worth watching Friday and into Saturday will be a shortwave trough that descends into the Great Plains. Overall timing and location of this system remain in question as the strength of an upper-level trough situated in Ontario will be key in how much room to come north this wave has. Cluster analysis of the grand ensemble (GEFS/EC/Canadian ensemble) would suggest one scenario (this one currently seeming more likely with about 70% of members) where the strength of the upper-trough and timing of the shortwave would be favorable for bringing accumulating snow to the region as the shortwave swings into the local area. In this scenario, roughly 30 to 60% of members bring an inch of snow or greater to the local area. In other scenarios the shortwave gets pushed south of the local area due to the upper-level trough being stronger and would result in little snow for the local area. So, certainly looks like the next period that could bring accumulating snow but still much uncertainty on where this shortwave tracks. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1137 AM CST Tue Dec 2 2025 The IFR/MVFR ceilings and visibilities will gradually become VFR this afternoon. The ceilings will then lower back into the IFR/MVFR late this evening as an arctic cold front moves southeast through the area, and remain that way through the remainder of the TAF period. Visibilities will be lowered into the IFR/MVFR for about 4 hours as snow falls ahead and just behind the cold front. For KRST, this will most likely occur between 03.03z and 03.07z. For KLSE, this will most likely occur between 03.04z and 03.08z. Snow totals will range from a dusting to around a half-inch. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Naylor AVIATION...Boyne