Chicago and the eastern third of the country better get used to Wednesday’s chill, since overwhelming forecast evidence points to a prolonged cold spell. With the jet stream locked south of Chicago for at least two weeks, temperatures should remain below normal through the period. Extended strings of cold, cloudy weather with flurries are not unusual in March, the most recent occurrence was just last year.
In the current regime, our jet stream remains well south, and begins to sink southward across the West, replacing the several weeks of warm weather there. The resultant cool pattern across the lower 48 is a difficult one to dislodge, hence the high confidence in extended chilly weather.
Snow Thursday could total an inch or more, and a new system with lighter amounts on Friday. The bulk of the energy with future systems should track south of Chicago.

The system that brought the cold air to the Midwest on Monday developed into another big nor’easter off New England, with interior Maine can expect over a foot of new snow. Meanwhile, frigid air by March standards settled into the Midwest. Embarrass, Minn. recorded a low of -30° Tuesday morning, with below zero readings speckled across the north.
This cold pattern is now well established across the northeast quarter of the country, and Chicago will remain along the western flank of this frigid air mass until further notice. However, just a few hundred miles to the west, more spring-like temperatures are in control, and some of this mild air approaches by early next week. Before then, the only weather maker of the next week races southeast from the Canada for some snow here on Thursday, before developing into the next big winter storm off the northeast coast on Saturday.