After a fairly quiet and cold weekend across Illinois, attention will turn to a strong wave that will be diving southeast across Canada and eventually into the northern US by Sunday morning with its sights set on the Midwest to end the weekend. This is the system that is going to be our next shot of accumulating snow across about the northern half of Illinois.
This potent shortwave will have several things going for it to lead to a healthy and widespread area of accumulating snowfall. First, northern Illinois will sit on the nose or left exit region of a very strong upper level jet (seen below in red and purple coming southeast out of Canada) and this area is usually favored for enhanced large scale lift and rising air which is one of the ingredients needed for precipitation.
Secondly, a nice low level jet associated with the low level cyclone will lead to a fairly long period of broad warm air advection into our area, another way to get the air lifted and produce snowfall. This larger area of red you see below in the loop should lead to a fairly large area of snowfall across the northern Midwest and central Midwest (MN/WI/IA) by Sunday evening. Temperatures throughout the atmosphere will also be quite cold which will lead to snow accumulating easier.
Below is one models take on what could happen so take it with a grain of salt and also the fact that we are still several days away from this event occurring. I just wanted to write this article to give a few days heads up given there is already pretty good agreement among numerical model guidance at this range for accumulating snow. Based on this model (the 12z GFS) snow would move southeast into Illinois Sunday night and continue into Monday morning and early afternoon, with continued snow across northern and northeast Illinois into even the evening hours.
Updates on this system will continue to be sent out over the coming days as we get new closer to Sunday but as of now, plan for snow Sunday night and into Monday across a good portion of Illinois.