Here’s the surface weather map for 11 pm Thursday evening. There is a high pressure center along the Florida/Georgia border. The air circulates around a high in a clockwise fashion, so the high was pumping warm and humid air from the Gulf of Mexico up through much of the Eastern U.S., including Southern Michigan. There is another, cold high pressure center north of Montana. That high was pumping cold, winter-like air southward into the Northern Plains.
There are low pressure centers near Traverse City and in Eastern Kansas. A warm front extended from the low in Traverse City east to Delaware. A cold front extended from the low near Traverse City to the low in Kansas and down into the Texas Panhandle.
During the day Thursday, Lower Michigan was north of the warm front, with a cool east wind and temperatures in the mid 40s. In the evening, after the sun set, the warm front approached and came through…look how the temperature went up: 8 pm = 46°, 9 pm = 48°, 10 pm = 52°, 11 pm = 55°, 12 am = 59°. The temperature peaked at 62° shortly after 1 am. So, after the sun went down around 8 pm, the temperature then rose 16° in G.R. – pretty amazing.
Then the cold front went through. When it did, the wind howled and the temperature plummeted. Peak wind gusts included 37 mph in Gr. Rapids, 40 mph in Holland and 41 mph at Benton Harbor. In Grand Rapids, the temperature fell from 61° at 2 am to 51° at 3 am. South Haven fell 15° in just 40 minutes…from 63° at 2:15 am to 52° at 2:35 am to 48° at 2:55 am. The warm air never got north of Muskegon County. At the same time it was 62° in Holland, it was only 39° in Ludington. The cold front did go through Manistee, changing their wind from east at 11 pm to west at midnight…but the temperature actually rose one degree.