March chill lingers in Chicago, northern U.S.

The blustery, chilly winds of a March-style cold spell that began Monday will continue right through the seven day period. During this period, the hemispheric upper pattern does undulate considerably—not unusual in late March—but the massive polar vortex remains steadfast over in northeastern Canada, promising a steady diet of frigid arctic high pressure for the eastern half of the U.S.
The next weather-maker in this regime arrives early Thursday, with Chicago right on the rain-snow line. A compilation of current guidance suggests precipitation will begin as snow early Thursday, change to a rain and snow mix in the morning, and end as all snow Thursday afternoon. A slushy inch or two is possible in the city, with more snow north near Wisconsin and mostly rain south. In any event, the next round of chilly air invades the entire region Friday.