A fast-moving storm system located over Eastern Colorado this morning will quickly move across the Central U.S., bringing a round of winter weather to the upper plains with locally heavy snowfall amounts expected across Northeast Iowa and Southern Wisconsin. Precipitation will also start as light freezing rain across Central Iowa this morning, before transitioning to snow this afternoon, which will make for very difficult travel conditions.
This morning’s weather analysis shows the upper level low pressure system near the Colorado/Kansas border this morning (image source: College of DuPage).
By this evening, we can see this trough of low pressure has moved northeast into Iowa per RAP model projections, with strong upper level dynamics acting to enhance precipitation across Iowa and Wisconsin (image source: pivotalweather.com).
Shallow moisture in place across Central Iowa will result in some light freezing rain or drizzle this morning, with temperatures in the teens/low 20s. This will make for treacherous travel conditions initially. By this afternoon, we’ll see moisture spreading into the area with snow developing across Iowa and Southern Wisconsin (including areas that were previously freezing drizzle). The next image shows the HRRR-projected precipitation type radar for 2pm central time this afternoon (image source: pivotalweather.com).
Notice the sharp precipitation type transitions the farther south you go. Chicago will actually start out as freezing rain this afternoon, but warmer air arriving from the south will result in a transition to all-rain this evening for the Windy City.
The heaviest snow with this system will fall from Northeast Iowa across Southern Wisconsin, including Des Moines, Cedar Rapids, Madison, and Milwaukee. Many areas in this corridor could see snowfall totals of 6″ or more from Tuesday afternoon through Wednesday morning, with isolated higher end totals of 10″+ possible. Farther north, the Minneapolis-St. Paul area will be a bit too far north to see significant snowfall, with only minor snowfall totals expected here during the daytime hours Tuesday.
The next image shows one model’s projected snowfall totals across this region (image source: pivotalweather.com). While this shouldn’t be taken verbatim, it should give a good general idea of where and how much snow will fall across the area.
The highest snowfall rates across Iowa/Wisconsin are likely during the evening/overnight hours as the strongest upper level dynamics move across the area. Temperatures will be in the low 20s/upper teens throughout this event in the aforementioned areas, so snow will easily accumulate on road surfaces. The Tuesday evening commute and Wednesday morning commute will be significantly impacted across larger metro areas such as Des Moines, Madison, and Milwaukee.
In addition, gusty north/northwest winds will develop overnight and into Wednesday morning (strongest across Iowa), which will result in areas of blowing and drifting snow.