A potent Alberta clipper system will drop southeast out of Canada on Sunday night, bringing a round of heavy snowfall to the Madison and Milwaukee metro areas during the overnight hours. The timing of the snowfall will result in significant travel impacts during the Monday morning commute.
This fast-moving system is located way up in the Canadian Rockies as of early Saturday evening, but will quickly moves south into the Northern Midwest during the day on Sunday. By Sunday night, we see the surface Low approaching from the west, at which point some of the heaviest snow will be falling (image source: pivotalweather.com).
Look for snow to reach the Madison and Milwaukee areas by early evening Sunday, before really picking up later Sunday night with the heaviest snow expected between about midnight Sunday night and sunrise Monday morning. The next image shows the NAM Model projected radar reflectivity, with snow filling in across the area Sunday evening (image source: College of DuPage).
Southerly flow ahead of the low pressure center will transport warm air aloft into south central and southeast Wisconsin during the overnight hours – or what meteorologists refer to as “warm air advection”. This will act to enhance precipitation rates, with 1-2″/hour snowfall rates expected at times during the overnight hours across Southern Wisconsin.
The advancing warm air aloft will also have impacts on surface temperatures, with a significant rise in temperatures during the overnight period. In Madison, temperatures are expected to rise from the upper single digits Sunday evening into the mid to upper 20s by Monday morning. In Milwaukee, temperatures are expected to rise even higher into the low 30s by Monday morning, with perhaps a brief period of time with sleet and/or freezing rain mixing in.
The advancing warm air will make snow-liquid ratios a tricky forecast, and any mixed precipitation could potentially cut into snowfall totals across the Milwaukee area. Regardless, this will still be a high impact even through Monday morning with difficult travel conditions.
Most models are in general agreement with precipitation amounts with this system. Overall, snowfall totals are likely to range from 6-10″ from Madison to Milwaukee. The image below is one model’s projected snowfall totals through Monday afternoon (image source: pivotalweather.com). Notice this particular model projects even heavier amounts up toward Appleton, Sheboygan, and Green Bay. This likely is a result of potential lake enhanced snow due to southeast winds, as well as colder air farther north leading to higher snow-to-liquid ratios.
Light to moderate snow showers will continue through much of the day Monday, with temperatures quickly falling again after Monday morning’s brief warm-up, as a cold front moves through around mid to late morning. Gusty NW winds behind the cold front during the day Monday will add to the travel problems by result in blowing and drifting snow. In addition, if any melting occurs around Milwaukee on pavement Monday when temperatures briefly warm up, it will quickly turn to ice again by later Monday as temperatures drop.
Following this potent storm system, the bottom will really drop out this week as a powerful surge of arctic air arrives, plunging temperatures to near record levels through the middle of the week. High temperatures on Wednesday are likely to remain well below zero region-wide.