325 FXUS63 KARX 240827 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 227 AM CST Fri Jan 24 2020 .SHORT TERM...(Today) Issued at 227 AM CST Fri Jan 24 2020 Water vapor imagery early this morning reveals a pronounced closed upper low spinning over the Ozarks. Its warm conveyor belt was transporting Gulf moisture northward through the Appalachians, wrapping cyclonically into northern Illinois/southern Wisconsin and all the way back into Iowa. The deformation zone of this low is presently lifting into southern Wisconsin and northern Iowa with a large shield of light to moderate snow. As the surface low wobbles from Missouri into Indiana this morning, this deformation driven snowfall will continue to rotate more into the forecast area. However, overall snowfall intensity will gradually lessen the further north/west this snow shield progresses today as the strongest forcing progressively wanes. Models are also latching onto potential for some weak frontogenetic banding on the northwest edge of this system, so there may be somewhat of an "enhanced" band of snow (not expecting it to get out of hand) that rotates northwestward across the forecast area through this afternoon. Unfortunately that steadier snowfall will continue to expand across the area just in time for the morning commute (seems to be a pattern lately), so do expect some travel impacts once again this morning. However, not seeing signs of anything too out of hand even with the more moderate snowfall to our south at this hour, with the lowest visibilities over southeast Iowa/northwest Illinois down to 3/4 mile at times. The dendritic growth zone is not particularly deep (roughly 1 km) and maximum omega is only coincident with the DGZ for a few hours, so that will limit overall accumulation. Snowfall amounts through noon expected to range from 1 to 2 inches over southwest WI/northeast IA to around a half inch or less elsewhere. Heading into this afternoon, portions of western WI could briefly lose in-cloud ice as the dry slot wraps around into the area, so have introduced a chance of drizzle. Shouldn't pose any issues as afternoon temps will likely be in the mid 30s. Additional snowfall across the area this afternoon likely to be a half inch or less. .LONG TERM...(Tonight through Thursday) Issued at 227 AM CST Fri Jan 24 2020 The closed low responsible for our ongoing snowfall will continue to slowly progress northeastward into lower Michigan tonight into Saturday with wrap around precip remaining in at least far eastern portions of the forecast area. Still some questions just how far west it reaches, with some guidance getting as far west as the Mississippi River. Also questions as to just how strong the frontogenesis is in that band. Overnight short term guidance, albeit at the end of those particular model runs, has been a bit stronger with the mid-level frontogenesis signal compared to the longer term models from today aside from the NAM. However, the GFS has trended toward a stronger band as well with the 24.00Z run, so consensus is generally toward a bit more snowfall in central Wisconsin early Saturday morning. Model soundings indicate a pretty shallow dendritic growth zone with surface temperatures near freezing, so expecting a fairly wet snow that may have a little trouble accumulating at first. That said, should the stronger frontogenesis manifest itself in the form of heavier precip, those surface temperatures could be a few degrees too high and snow amounts could need to be raised a bit again. As it stands, looking like 1 to 2 inches of accumulation in central Wisconsin from Friday night into Saturday morning. Guidance is in pretty good agreement of that band fizzling rather quickly by mid to late Saturday morning. Model soundings indicate a loss of in-cloud ice for that time period with precip transitioning to rain or drizzle. Surface temperatures look to generally be above freezing by then, but it's not out of the realm of possibility that a few spots remain just below freezing and see some light icing. In addition, a few pieces of guidance hint at some (freezing?) drizzle or flurries persisting into Sunday, but given lack of strong, consistent signal between the models (lack of persistent saturation and lift in the low levels), have not included in the forecast at this time. Beyond Sunday, kind of a messy pattern with northwest flow aloft into mid-week with various bits of shortwave energy moving through and bringing snow chances. GEFS members differ quite a bit on exact timing and precip coverage, but anything that does fall looks to be rather light at this time. Otherwise, temperatures look to remain above the normals for this time of year, with highs in the lower to mid 30s through the week. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1010 PM CST Thu Jan 23 2020 Upper level shortwave troughs and persistent low level saturation will keep the region under clouds through the weekend, with periodic snow chances into Sat. Cigs: low clouds not expected to clear through the weekend, likely holding sub 1 kft through much of that time. WX/vsby: periods of light snow and fog look to continue into Sat. Mostly MVFR restrictions expected. See some potential for a narrow enhanced band of snow that could setup across KLSE for a few hours Fri afternoon. Vsbys could be reduced to 1/2SM in this scenario along with a quick inch of accum. Confidence not there to tempo, but it bears watching. Winds: northerly, mostly around 10 kts or less. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Kurz LONG TERM...CA AVIATION...Rieck