Snow to accompany early week warm-up

The Chicago area will temporarily emerge from the deep freeze early this week with temperatures expected to flirt with the freezing mark Monday for the first time since a 34º high back on Jan. 27. However, the brief warm-up will be accompanied by snow and followed by a midweek return to arctic cold.
A potent storm system moving along the southern branch of the jet stream threatens to produce a major snow from the southern Midwest into the middle Atlantic states. While the heaviest snow is still expected to fall south of Chicago, successive computer runs have been shifting the storm northward, increasing the city’s threat for significant accumulations. In addition, a period of lake-effect snow should develop here Monday night and Tuesday as a new slug of arctic air sweeps full-fetch down Lake Michigan. This means more subzero weather before a new moderating trend begins and continues through next weekend.
---By Steve Kahn, WGN Weather Center Meteorologist