By Meteorologist Paul Merzlock
The 80 degree temperatures of a week ago will be a fond memory by midweek as much colder air arrives. Through Sunday, the warm start to October 2011-which included a string of five 80 degree days-has officially accumulated a net temperature surplus for the month of 96 degrees. This surplus is about to be reduced as colder air over central and southern Canada lies poised to descend on the Midwestern U.S. Sunday evening, satellite imagery showed a disturbance associated with a 150 mph jet stream moving across the central Rockies. This disturbance is forecast to amplify as it approaches the Midwest on Tuesday, when it will phase with another system dropping down from the north. This will combine to form a deep low pressure center just east of Chicago by mid day Wednesday. The resulting buckle in the jet stream will draw polar air south across the western Great Lakes resulting in temperatures about 12 degrees below normal. The cool down will be brief however. By Friday temperatures will already begin to moderate.
The 80 degree temperatures of a week ago will be a fond memory by midweek as much colder air arrives. Through Sunday, the warm start to October 2011-which included a string of five 80 degree days-has officially accumulated a net temperature surplus for the month of 96 degrees. This surplus is about to be reduced as colder air over central and southern Canada lies poised to descend on the Midwestern U.S. Sunday evening, satellite imagery showed a disturbance associated with a 150 mph jet stream moving across the central Rockies. This disturbance is forecast to amplify as it approaches the Midwest on Tuesday, when it will phase with another system dropping down from the north. This will combine to form a deep low pressure center just east of Chicago by mid day Wednesday. The resulting buckle in the jet stream will draw polar air south across the western Great Lakes resulting in temperatures about 12 degrees below normal. The cool down will be brief however. By Friday temperatures will already begin to moderate.
