A strong, persistent upper-air pattern has evolved that will establish a steady west-to-northwest wind flow over the Great Lakes and the Chicago area through the weekend.
A deep low-pressure center will be situated just off the coast of Newfoundland, and a huge ridge of high pressure will dominate western Canada as well as the western and southern United States. Caught up in the counterclockwise rotation, pin-wheeling elongated troughs of lower pressure will spin around the low pressure center, traveling through the Chicago area, repeatedly bringing reinforcing bursts of cold air along with periods of snow showers or flurries.
Cloudiness giving us zero sunshine on eight of the past 10 days is expected to continue into the first part of next week. As of Wednesday, we had only 25.6 percent of possible sunshine for the month, the third-lowest January sunshine percentage since records began in 1894.
