It is now early Monday morning and everything looks to be still on track regarding the winter storm that will be moving into the Midwest from the plains later today. This is going to bring a conglomerate of precipitation types to Illinois as the wintry weather will mostly be confined to northern Illinois, as mentioned in the article post late yesterday afternoon. This system will have the potential to bring freezing rain, sleet, and several inches of snow to that area between this evening and through portions of Tuesday. This continues to be a very tricky forecast, especially along the I-88 corridor of northern Illinois up to the Wisconsin border.
To start off, we have upped both expected snow totals and freezing rain/ice totals. The new snowfall map you can see below and the forecast freezing rain/ice amounts are at the bottom of the article.
Our system overnight has continued slowly eastward and is now located across the Four Corners region of the Southwest U.S. early this morning. It will continue in the same direction, crossing the southern Rockies later this afternoon before emerging into the plains tonight.
Precipitation will continue to develop and blossom later this morning over the plains and slowly make its way east and northeast into the Midwest later this afternoon. The brunt of the action will begin from southwest to northeast across western and northern Illinois during the late afternoon and evening hours, potentially impacting the Chicago area during the evening rush hour. As things stand now, precipitation would start out as snow along/north of I-88 for a period before flipping over to freezing rain (potentially sleet) for a brunt of the late evening and overnight hours), leading to ice accumulations in that corridor. But, this remains a tricky forecast with continued uncertainty. Some model guidance keeps that area mostly snow with less ice. It is quite rare to have this much disagreement less than 24 hours away from an event. Either way, expect a impacful Monday evening along/north of the I-80 corridor in Illinois.
Rain, freezing rain, and snow will continue most of the night across the state with as mentioned, the snow and freezing rain threat confined to the northern portion of Illinois. Eventually, cold air will fully advect into the region, allowing for precipitation to changeover to all snow across northern and central Illinois during the day on Tuesday. This is where additional snow accumulations are possible but tough to nail down but does look like an additional inch or two is possible, especially across northern Illinois.
Lastly, as the surface low pulls off to the east and northeast of Illinois during the day on Tuesday, it will strengthen fairly quickly and this will lead to winds picking up in strength across the northern half of Illinois. This juxtaposed with the backside snow potential could lead to more hazardous travel conditions Tuesday afternoon and evening with winds potentially gusting over 30mph over a large area.
Below is our latest thinking on freezing rain/ice accumulations as we have upped totals now to a quarter inch of ice possible in the green swath.