Update 5:30AM CST…
The Winter Weather Advisory for accumulation of 2 to 3-inches of wet snow NW of the city continues until 10AM CST this Tuesday morning (Purple-shaded area on the headlined map). Accumulations of an inch or so are expected elsewhere and closer-in to the city before gradually changing over to rain. Temperatures are generally at or above 32-degrees early this morning, so most snow accumulation will occur on grassy areas or very cold surfaces. Roads will be wet and become slushy and slick in spots with more intense snowfall, so if driving or out and about this morning, be prepared to be cautious and take a little more time to reach your destination. Snow will gradually change-over to rain from the south later this morning/by midday. Check the Regional Weather Radar Mosaic below for snow/rain progress.
Accumulating wet snow looks to spread over much of the Chicago area after midnight tonight. Snow will gradually change-over to rain from the south during the forenoon with heaviest accumulations 2 to 3-inches-plus possible along and west of Interstate-355 and north of interstate-80 where a Winter Weather Snow Advisory will be in effect from 2AM until 10AM Tuesday (purple-shaded area on the headlined map). Check the progress of the precipitation shield on the regional weather radar mosaic below.
Early on the snow will melt as it falls, but as the snowfall rate increases, accumulation will occur first on grassy areas and then on colder surfaces and eventually roadways. Travel before and a couple hours after sunrise, during the morning rush could become slushy and slick, so individuals expecting to be driving early Tuesday and Tuesday forenoon, should prepare for slowed traffic and slick spots. Snowfall amounts will be around an inch or so as you get closer-in to the city, but roads even there will be wet and potentially slick in spots.
Low pressure developing in SE Colorado will slowly make its way north during the next 24 to 36-hours, eventually reaching the Chicago area later Wednesday. Warm moist southerly winds will strengthen ahead of the approaching low pressure, initially flowing over the cold air in place over our area resulting in the period of wet snow, but with time, the warmer air will replace the cold air, with snow gradually changing over to rain, the last to experience this change-over will be Lake and McHenry Counties a little after midday Tuesday. Occasional rain is then expected to continue the remainder of Tuesday through Tuesday night and much of the day Wednesday.