(6:00PM - 12/29/20) A brief short term update regarding the winter storm that continues to affect the state this evening...
A large area of moderate to heavy snow is ongoing across a large portion of Northern Illinois. There was recently even an occurrence of thundersnow in Lee Co. Thundersnow has also been widespread in Eastern Iowa, with snowfall rates of 1-2"+ an hour being common. Snowfall accumulations in Northern Illinois have ranged anywhere from 1-6" thus far.
As warm air advection has been increasing, snow has been changing to sleet/freezing rain across portions of Western and Northern Illinois, south of I-80. With time, much of North-Central and Northeast Illinois will transition from snow to sleet/freezing rain, with only Northwest Illinois and areas near the IL/WI border likely to remain as all snow. Additional snow/sleet accumulation expected across much of Northern Illinois, highest amounts north and lowest south. Additionally, ice accumulation will be likely as precipitation changes over to a mix.