Temperatures on Friday jump to summer levels. It's a change guaranteed to capture Chicagoans' attention in a month that has averaged 2.5-degrees below normal to date. Wind trajectory forecasts, which allow the tracking of air movement, indicate Friday's warming originated 24 hours ago in Mississippi and Louisiana, where Thursday highs hit the mid-to-upper 80s. Powerful southwest winds--expected to reach 60 m.p.h. several thousand feet above the ground this afternoon--will transport that warmth into Chicago so swiftly that the usual level of cooling that occurs in northward moving air is likely to be overcome. This suggests Chicago’s official high Friday may well reach 85 degrees--a level 24 degrees above normal and more typical of July than April. It took another five weeks for similarly warm temperatures to occur a year ago.
Not only are temperatures to warm here, humidities surge in coming days as well contributing to a dramatically different, more spring-like feel to the air--but also possibly fueling thunderstorms as a cold front sags south toward the area late Saturday. That front could shift Saturday’s strong and unseasonably warm south/southwest winds to the east Saturday night into Sunday morning producing cooling before warm air resurges Sunday afternoon.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
