FXUS63 KARX 191035 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 535 AM CDT Wed Mar 19 2025 .KEY MESSAGES... - An impactful winter/spring storm will move through the Upper Mississippi River Valley today and tonight bringing a narrow band of heavy snow, strong winds, and isolated to scattered morning storms. - Isolated to scattered storms in southwest Wisconsin, and parts of northeast Iowa and southeast Minnesota this morning. A few of these storms may produce small hail. - The band of heavy snow (4 to 8 inches - locally higher) was shifted southeast. At this time, the heaviest snow looks to fall from Mason City, IA northeast to Wausau, WI. - Strong north winds (sustained winds of 25 to 40 mph and wind gusts of 40 to 55 mph) from this afternoon into the evening. These strong winds will likely produce white-outs and blizzard conditions. In addition, there could be some power outages. && .DISCUSSION... Issued at 327 AM CDT Wed Mar 19 2025 Through Tonight The deepening low pressure area will move across southern and eastern Iowa this morning. A coupled 250 mb jet will be located across the region this morning and then shift east of the area this afternoon. This will enhance the upper level divergence across the region. In addition, up to 500 J/kg most-unstable CAPES will move into southwest Wisconsin, and parts of southeast Minnesota and northeast Iowa. This will result in isolated to scattered storms. With cold air aloft and elevated skinny CAPE, a few of these storms may produce some small hail. The 19.00z models shifted the heavy snow band slightly southeast Mason City, IA to Wausau, WI. The models continue to show that this band will likely produce hourly snow rates of 1 to 2 inches this afternoon. Snow totals still look to be in the 4 to 8 inch range. The 19.00z SPC HREF 24-hour ensemble probability-matched mean still has a narrow (1 county-wide) band of 10 to 15 inches. Due to strong north winds (strongest this afternoon and evening), the wet-nature (wetter than the typical 13 to 1 ratio which will result in more compaction) of this snow, and short-duration (6 to 8 hours), there is plenty of uncertainties on whether these higher snow will actually be observed. With the snow band shifting southeast, we decided to add a few more counties to the Winter Weather Advisory (Chickasaw, Allamakee, Vernon, Adams, and Juneau counties) and Blizzard Warning (Floyd and Howard counties). With the blowing and drifting snow expected to continue into this evening, the ending time was pushed back from 20.00z to 20.03z. The combination of a tight surface pressure gradient and steep surface to 875 mb lapse rates, surface winds will range from 25 to 40 mph and wind gusts will range from 40 to 55 mph. The strongest winds will be from this afternoon into this evening. The winds will gradually shift from northeast to north this morning and then continue out of the north through this evening, and gradually subside and shift to the northwest overnight. These strong winds will likely produce white-outs and blizzard conditions. In addition, there could be some power outages. Friday and Friday Night Another 500 mb shortwave trough will move southeast through the area. Unlike its predecessor, this system is initially moisture starved. As a result, much of the initial lift goes toward saturation. As far as the probabilities of at least 0.05 inches of QPF, the grand ensemble has up to a 15 percent north of Interstate 90 and 15 to 30 percent for the remainder of the area. Boundary layer temperatures continue to support that this precipitation will be mainly rain. High temperatures on Friday will range from the mid- 40s to mid-50s. Late Saturday Night into Monday The models show that an open 500 mb short wave will southeast into the area on Sunday. This system then deepens and closes off to form a 500 mb low. There continues to be some uncertainty on how progressive this system will be at moving out of the Great Lakes early in the week. This impacts how long the precipitation will remain across the Upper Mississippi River Valley and how fast the western CONUS ridge builds eastward across the region (this will impact temperatures). There continues to be quite a bit of spread in the Grand Ensemble on QPF amounts. The 10th percentile ranges from a trace to a few hundredths of an inch. Meanwhile, the 90th percentile ranges from a half of an inch to 0.65 inches. In addition, precipitation type remains uncertain. The NBM 10th percentile would keep the high temperatures on Sunday and Monday in the 30s. Meanwhile, the NBM 90th percentile would have high temperatures ranging from the mid-40s to near 60 on these days. && .AVIATION /12Z TAFS THROUGH 12Z THURSDAY/... Issued at 536 AM CDT Wed Mar 19 2025 Currently watching some convection moving through southern Iowa. If these storms hold together, they would impact KLSE around 19.14z. Snow will move into KRST around 19.14z and then persist through 20.02z. Delayed the onset of the blowing snow until the early afternoon. With no snow on the ground, we will have to wait until there is about 2 inches on the ground for this snow to become airborne again. As far as KLSE, the precipitation will start out as rain and than transition to snow around noon. North winds will increase into the 20 to 35 knot range with gusts of 35 to 50 knots this afternoon and then continue into this evening. Snow totals will likely range from 4 to 8 inches for KRST and 2 to 4 inches for KLSE. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...Winter Weather Advisory from noon today to 10 PM CDT this evening for WIZ041>044-053. Wind Advisory from 1 PM this afternoon to 7 AM CDT Thursday for WIZ054-055-061. Winter Storm Warning until 10 PM CDT this evening for WIZ017- 029-032>034. MN...Blizzard Warning until 10 PM CDT this evening for MNZ079-086- 087-094-095. Winter Weather Advisory from noon today to 10 PM CDT this evening for MNZ096. Winter Storm Warning until 10 PM CDT this evening for MNZ088. IA...Blizzard Warning until 10 PM CDT this evening for IAZ008-009- 018. Winter Weather Advisory from noon today to 10 PM CDT this evening for IAZ010-011-019. Wind Advisory from 1 PM this afternoon to 7 AM CDT Thursday for IAZ029-030. && $$ UPDATE...Zapotocny DISCUSSION...Boyne AVIATION...Boyne