Everything looks to be on track with our snow system that is going to move into and through the state of Illinois during the day on Sunday, bringing with it accumulating snow. As mentioned several times, this will be the first of several possible storm systems to affect the region over the next week to 10 days, some of which could bring more snow to Illinois.
Taking a look at our system early this morning out west, we can see it pushing across southern California at this time and will continue moving off to the east and northeast over the next 24 hours.
As low level winds (the warm air advection component mentioned yesterday) strengthen tomorrow night, precipitation, including an area of widespread light to moderate snow will begin to develop across the east central plains after midnight tomorrow, and begin moving through portions of Missouri and Iowa early Sunday morning.
Temperatures across the northern half of Illinois will be well below freezing at the surface Sunday morning in the low to mid 20's (shown below) so expect snow to begin sticking fairly quickly once it begins.
Model guidance continues to differ somewhat on just how long snow will last across the area with some models ending snow fairly quickly by early to mid-afternoon while other guidance continues light snow into the early evening hours. Either way, this isn't looking like a big time snow maker or headline maker for travel conditions, especially on a Sunday.
Below is a loop of one models take, showing snow moving in from the southwest Sunday morning and overspreading much of the northern half of Illinois by the lunch hour. It then (based on this model) snows into the evening hours, even though in a light fashion. Some places across portions of southern Illinois, including the St. Louis area could start out with a period of snow but as temperatures warm aloft, expect precipitation to change to a mix and eventually all rain.
Below is our latest TAM/expected snowfall map with not much change from the previous one.