The second round of accumulating snow arrives Thursday evening, lasting through Friday morning. Most of the snow early Thursday evening has been light, but should begin to pick up in intensity during the overnight as low pressure moves into southern and central Illinois. Copious amounts of moisture are streaming north ahead of low pressure diving southeast from the central Plains. Temperatures in the low to mid 30s across much of northern Illinois will allow some rain to mix in with the snow, but mostly for areas east and southeast of Rockford.
An additional 1-2 inches of snow will be likely Friday morning with light snow falling through mid-morning. Areas that see some rain will have lower snow totals. After that, drier air gets wrapped in around the low across central and northern Illinois. This will cause the steady rain/snow mix to end for a little while during the afternoon before picking back up Friday evening and overnight. It’s that time frame we may need to keep a close eye on for the potential for heavy snowfall over parts of northern and northeast Illinois.
Low pressure will lift north into northeast Illinois and northwest Indiana by Saturday morning. There is a little cooler air that gets pulled south behind the low and this could allow for a quick transition over to heavy snow Friday evening and night. If this were to happen the snow would be heavy and wet, and would quickly accumulate on the roads, possibly impacting the late evening commute. It’s still yet to be seen if enough warm air will remain Friday evening to keep the precipitation as rain or allow for a changeover to snow. But if we do see the snow, several inches could fall by Saturday morning.