December-level chill remainder of the work week
Temperatures were at 62° just before 1 a.m. Tuesday morning and had crashed 25° to a reading of 37° at 8:30 a.m., just a little over 7 hours later. The same cold air mass will force temperatures to start out today in the 20s over much of the metro area and struggle to warm far into the 40s despite abundant sunshine this afternoon.
Thursday this cold air mass will be reinforced with an even colder surge of Arctic-source air with origins in the Canadian Nunavut Territory some 1200 miles to the north. Winds aloft at jet stream level from northwestern Canada into the central plains are steering cold high pressure all the way from the Arctic through central Canada into the Midwest. During the day Thursday even though the air is very dry, an upper air impulse may give snow flurries to the metro area, but 30° temperatures riding over the 50° waters of Lake Michigan could give lake effect snows in northwest and north-central Indiana.
-Paul Dailey, WGN-TV Meteorologist