With each passing model cycle, confidence is slowly increasing on a snowstorm affecting portions of Illinois, beginning Wednesday morning and eventually departing the state early Thursday morning. Right now, Wednesday afternoon and evening looks to be the worst of this storm, potentially leading to a slow and treacherous evening commute across portions of the state. You'll find our first snowfall totals forecast below and can see that there is the potential for some areas to receive up to a half a foot of snow.
Our upper level low is sitting over Utah and Colorado this evening and about to cross the Rockies later tonight and tomorrow. By Tuesday night and Wednesday, a smaller wave or weather disturbance will come around the base of the trough, inducing our area of low pressure to develop across northern Mexico and the Texas gulf coast, as mentioned in the previous article. That wave will then quickly eject out into the southern planes, kicking our storm system northeast into the southern Midwest and Ohio River Valley.
What will be quite favorable for this system will be the open Gulf of Mexico, providing plentiful moisture into this system. Strong warm air and moisture advection on the wings of strong low level winds out of the south (shown below) will aid in transporting that moisture northward and eventually northwest of the surface low into the cold air, leading to a widespread area of snow by Wednesday afternoon and evening (rough estimate of that area in orange).
Not much has changed regarding the overall evolution of this snowstorm. Expect precipitation (including snow) to increase from southwest to northeast across portions of the state on Wednesday morning and then that area of widespread snow streaking northeast into central and northern Illinois during the afternoon and evening hours. Given temperatures in the upper 20's across the heart of the expected snow area over the northern half of the state, expect conditions to quickly deteriorate once snow begins and we expect roads to become snow covered, especially during the evening hours. It could be quite the slow go during the evening commute across northern Illinois and the Chicago metro area, as things look now.
Below is our first TAM/expected snowfall totals forecast. This is subject to change but this is our first thought on this storm system. Stay tuned for continued updates as we draw closer to this snowstorm.