A major pattern change is to send arctic air packing and a flood of mild oceanic air across the nation’s mid-section in coming days. The unseasonably mild pool of air has an oceanic origin and is to sweep ashore off the Pacific sending virtually the entire Lower 48 into a spell of unseasonable warmth just as the new month of December gets underway this weekend.
The transition to 60+degree temps Sunday and Monday may even send Chicago readings within striking distance of some records.
Current indications are the area is to see a 5-day temperature increase of 46 degrees---from Tuesday morning's 17-degree low to Sunday's predicted 63-degree high.
With a powerful southwesterly surface wind flow predicted to take hold as early as this Saturday, it's even possible a 60 will occur before this coming Sunday or Monday arrive---on Saturday!
Storm responsible for sending Pacific "warmth" onshore prompting weather watches/warnings on/near the West Coast
The mild maritime air bound for Chicago and the Midwest, is being propelled into the country by a mammoth eastern Pacific storm. The system’s intensity has led to an array of weather watches and warnings being issued on the West Coast---covering everything from high surf (breakers up to 28 ft. are being predicted on the California/Oregon coasts) to flash flooding at low elevations and hefty, high-elevation snows.
A big temp jump's ahead for Chicago---but NOT the city's largest
Chicago's largest 5-day November temperature rebound in 13 years appears a good bet by Sunday. But, as impressive as a 46-degree temp surge would be, it's not the city's largest. That honor goes to 1959 when the city registered a 55-degree five-day November temperature surge, increasing from 3 to 58 degrees on Nov. 17-22
Tuesday's 33-degree high is meteorological fall 2012's second coldest and only the third day this season in the 30s
The 33-degree high Tuesday marked Fall 2012's second coldest late season temp and the third day to record highs in the 30s
Jet stream realignment driving the slow warming cycle
The frigid air of recent days was directed into Chicago by northwesterly jet stream steering winds flowing out of the arctic. That "polar" jet is retreating north and, in its place, a second jet stream roaring off the Pacific and into the Lower 48 with mild air in tow is to take over. This second jet stream is to dominate U.S. weather into early next week.
Five of seven computerized National Weather Service forecasts continue hinting at sticking snow in the 8 to 14 day time frame
Evidence that sticking snow may still be on the Chicago's meteorological horizon in the 8 to 14 day period continues. Five of the most recent 7 runs of the National Weather Service's GFS model indicate the potential for sticking snow.
While hardly carved in stone yet, generally when there's smoke, there’s fire. The series of GFS runs appears to suggest Chicago area weather is headed in a direction in which at least some sticking snow may occur. Stay tuned.