Precipitation associated with our winter storm is quickly spreading northeast across portions of central and northern Illinois late this afternoon and is actually ahead of scheduled compared to latest computer model guidance. There has already been reports of snow and sleet up to the I-80/88 corridors across far eastern Iowa, including the Quad Cities and into northwest and north central Illinois. The Chicago metro area is up next and should see precipitation across all of that area within the next hour or so.
We can see this by taking a look at a regional radar image below. A widespread area of precipitation is working its way northeast and this will continue gradually into the evening hours, overspreading all of northern Illinois.
Taking a look at latest high resolution model guidance, we can see that precipitation will continue expanding east and northeast with the movement of the surface low through the rest of the evening and it continuing through the overnight hours. This remains a very tricky forecast with still a wide range of precipitation types still expected. As you can see in the loop below, you go between several different precipitation types over a short distance which makes this a very tough forecast. Either way, the Tuesday morning rush hour could be quite problematic due to snow and ice accumulations by that time.
As mentioned in earlier posts, precipitation will eventually change to all snow across northern and central Illinois by late tomorrow morning and early afternoon after a lull in activity as colder temperature advect in from the northwest as the low pressure system moves into Michigan. This will mean additional snow showers that could lead to another inch or so of accumulations across the area. The loop below goes from tomorrow morning through late tomorrow night, showing the increase in snow during the afternoon and evening hours across northern Illinois and portions of central Illinois. Not only will temperatures be dropping off steadily into the afternoon an evening hours with low to mid 20's by evening, the winds will also be strengthening. So although not a lot of snow is expected tomorrow afternoon and evening, the combination of wind whipped snow and dropping temperatures could also impact rush hour to an extent tomorrow afternoon and evening.
Our latest TAM's (expected snow and freezing rain/ice accumulations) can be found below.