Wednesday marks Chicago’s 7th consecutive day in a Deep Freeze—a period in which each day has finished substantially colder than normal.
Daily deficits over the past week have averaged an eye-catching 12.7-degrees below normal, a far cry from the milder than normal weather with which the month opened.
The area braces for still another blast of arctic air—this one expected to ride powerful post-Alberta Clipper winds over a fresh new 1-3 inch snowpack expected by the time Wednesday morning’s commute period snowfall comes to and end mid morning.
By nightfall, thermometer readings will have crashed from the mid to upper teens to single digits—ultimately headed sub-zero overnight when wind chills plunge as low as 20-below!
It’s the 11th day with a “trace” or more of snow in Chicago; 60% of the previous 129 winters have generated seasonal snow tallies equal or greater than this season’s 4.2” to date
The recent chill’s been just part of the story. Wednesday morning’s snowy open marks the 11th day a “trace” or more of snow has fallen in the young 2013-14 season.
To date, 4.2” is on the books. While substantially more than a year ago—when NO measurable snow had fallen—the tally is only modestly more than the “normal” 3.8”. And a scan of Chicago’s official snow record dating back to the 1884-85 season, indicates 58 of the past 129 seasons—-that’s 45% of them—have produced 4.2” or greater snow tallies through Dec. 10.
It’s also interesting to note that 11 days with a trace or more of snow through Dec. 10 is actually one day short of the 129 year average of 12 days which see a trace or more of snow for the period.
Tuesday morning’s -6 at O’Hare the coldest early season temp in 35 years and colder than any reading here the past 2 winters
Chicagoan’s haven’t had to deal with temperatures colder than Tuesday morning’s 6-below official minimum since just after the Groundhog’s Day blizzard of February 2011.
It’s been 35 years (1978) since a minus-6-degree or lower temp has occurred by the conclusion of Dec. 10. An analysis of the 143 year temperature record here since 1871 reveals only 8 other years have had a temperature as cold as Tuesday’s 6-below so early in the season. Those years include: 1871, 1876, 1882, 1893, 1919, 1958, 1977 and 1978.
What’s interesting is the average number of 0-degree or lower days which ended up occurring in those years was 14 versus the long term average of 8.
The past 6 days have averaged 12+-degrees below normal
Each of the past 6 days have finished far cooler than normal—and Wednesday promises to become the 7th.
Temperatures over those six days have averaged an eye-catching 12.7-deg below normal in a month running nearly 16-degrees colder than a comparable period a year earlier.
Attention next turns to weekend snow threat
A new snow system—this one with Gulf moisture available to it and the potential top entrain some lake moisture—marches onto the country’s weather stage late this week and over the coming weekend.
Model projections of this storm’s probable track suggest its heaviest snow would fall south of Chicago with several inches of snowfall possible here. A northward shift of that storm track amounting to 100 or 150 miles might well put Chicago and the entire metro area at a greater threat for more significant snows.
Winter off to quite a start out East too; Tuesday’s 2.2” snow in Philadelphia boosts seasonal total there beyond last winter’s
Midwesterners and Westerners are hardly the only folks dealing with the fall-out from one of the stronger arctic outbreaks in years.
Philadelphia was hit with 2.2” of snow on the eastern flank of that cold surge Tuesday, an accumulation which boosted the seasonal tally there to 10.8”. That’s more snow in Philadelphia than occurred ALL of last season.