A cold front will sink south through the northern Illinois Sunday with Chicago area winds shifting more and more northeasterly as the leading edge of cold Canadian high pressure eases into the Midwest and western Great Lakes. For the next seven days a predominantly northeast flow will persist here as the huge high pressure air mass will pretty well hold in place as a series of low pressure systems track out of the southwest through the Tennessee and Ohio Valleys.
Chicago’s temperature was just a degree below normal Saturday – the first day with below normal temperatures this month - snapping a string of 24 days with above normal readings. The next seven days are expected to see temperatures within a couple degrees of late December norms.
Significant snows to the east
Current thinking is that Chicago will be positioned on the northern edge of significant snow-producing low pressure systems to our south this week. The first center of low pressure is forecast to move east up the Ohio River Valley Monday - producing snow over northern portions (including the Chicago area) and rain over southern portions of Illinois and Indiana. As that low moves off to the east, gusty northeast winds could give Chicago some lake effect snow showers Christmas Day. Wednesday Chicago will be grazed by snow as it appears the center of a winter storm will probably move east through Kentucky into southern Ohio dumping 5 to 10 inches of heavy wet snow over portions of Indiana and Ohio. Indications are that yet another winter storm system could move east out of the southern plains spreading snow over a good portion of the Midwest and western Great Lakes including the Chicago area next Friday night and Saturday.