Unsettled weather pattern threatening far northwest suburbs with wintry cocktail while chilly rains are slated in Chicago in coming days

The threat of slushy accumulations of wet snow and possible mixed sleet loom over sections of Chicago’s far northwest suburbs while a chilly rain appears poised to fall at times in the city over coming days.

Two separate precipitation-producing systems are driving the Friday and weekend weather pattern here.

If snow actually occurs over far northwest sections of the metro area, which it may first do Friday night, it could be doing so even as the city proper moves toward establishing a new record for the longest string of days FREE of measurable snow.

Current string of 278 measurable snow-free  days now on the books just two days shy of tying record

Friday marks the 278th day since measurable snow last fell at O’Hare on March 4—and puts the city ever so close (just 2 days away) from tying the 1994 record of 280 days. That record was established 18 years ago.

With the demarcation between rain and more wintry frozen forms of precipitation expected to set up across the greater metro area with each of these two precipitation-producing systems in coming days, it’s not out of the realm of possibility a new record for lack of measurable snow will be set in the city even as a slushy accumulation of snow collects northwest toward Rockford, McHenry and Boone counties north into Wisconsin.

Friday’s 40s extends the early-December “mild streak” into a tenth consecutive “above normal” day, longest since late August/early September

It’s the tenth straight day of above normal temperatures at O’Hare—the longest stretch of above normal readings here in 4 months—since a string of 16 above normal days occurred from Aug. 23 to Sept. 7.

City’s lack of “official” measurable snow through December 7 open puts the 2012-13 season in league with six other years

With only a trace of snow on the books here in Chicago to date, the open of the 2012-13 snow season joins just six others which have seen so little snowfall at this point in the season.

December’s running  7.6-degrees warmer than a year ago

Even as warm as last December was, the six opening days of this month have still managed to beat the average temperature recorded over the same period last year by 7.6-degrees!

Markedly colder pattern to dominate the coming 2 weeks with reinforcing cold surges at regular intervals

All appears “go” for a strong, high-latitude blocking regime centered on Greenland to come together over the next two weeks forcing colder weather into the Midwest. A series of active weather systems embedded within the upper air pattern which results will have to be monitored for possible snow production here from time to time.