Fourth Alberta Clipper of past week on a more northerly track reducing its impact on Chicago; only a dusting or some freezing drizzle expected


Snow’s been so frequent in Chicago over the past 11 days that the city’s current 8.7″ tally represents a more than 5-fold increase in that short period of time! Measurable snow has fallen 7 of those 11 days.



Just  3.5″ was on the books for the current season last Thursday as the month of January came to an end.  Since then, three Alberta Clippers have raced across the metro area in rapid succession dropping 0.5″ this past Friday (Feb 1), 1.8″ Saturday (Feb 2), 0.5″ Sunday and—in the largest single-day snowfall of the season—2.4″ on Monday.



From just those three systems alone, the city’s seasonal snow total more than doubled in the space of less than a week.



Though a fourth Clipper traverses the Midwest Tuesday, its track is north of its predecessors.



Since the heaviest snowfall generally accumulates north of storm tracks, it’s the Upper Midwest which is to see the bulk of Tuesday’s accumulation. The Chicago area is likely only to experience light snow or flurries possibly mixed with some freezing drizzle at times, the product of a layer of comparatively warm air aloft.



Monday marked the fourth consecutive day of measurable snowfall here—longest such streak in 4 years



Monday’s snow tally marked a fourth consecutive day of measurable snow. The last time 0.1″ or more of snow fell on four days back-to-back was in 2009.  In that snowy spell, nine rather than four consecutive days logged measurable daily snowfalls.



After 4 full days, Feb 2013’s running 22.5-degrees behind the same period a year ago; it’s the coldest Feb open here in 2 years!



But snow hasn’t been young February 2013′s only attribute. The month has opened cold!  In fact, Feb. 1-4 has averaged 22.5-degrees colder than the same period a year ago.



The 14.6-degree average temperature is 9-degrees below the long term average dating back to 1871 and makes the four opening days of the month the 32nd coldest February start since weather records began 142 years ago. It’s the coldest early February period since during and right after the February 2011 Groundhog Day blizzard 2 years ago.



More moderate brand of cold air dominates the week ahead; mild air’s close: 50s downstate!



While no picnic, a more moderate brand of cold air now dominates Chicago’s weather—not the frigid arctic air which produced nighttime lows near zero and daytime highs which held to the low teens last week. The core of the arctic air has retreated north, taking the coldest readings with it.


Chicago is to see more seasonable highs in the low 30s in coming days, but areas of downstate Illinois and Indiana—-close to and just north of the Ohio River—will bask in late winter 50s Tuesday.


Chicago weather history is clear: the metro area has moved well past the mid-point of winter



While wintry weather isn’t yet completely behind us, the area has moved past winter’s mid-point.



An analysis of the city’s official observational record since 1871 reveals that, on average, 60% of its seasonal snow has occurred, as has 62% of the cold season’s sub-freezing temperatures and 20% of its 0-degree or lower temps.



The city’s “normal” high temperature breaks above 32-degrees for the first since Christmas (Dec. 25) on Wednesday.


Wintry cocktail could make for an icy spell Thursday; warming ahead of the next storm on Sunday to bring rain



Milder temperatures aloft mean the next disturbance to reach the area—this one to arrive Thursday—is likely to produce a wintry cocktail of precipitation ranging from some sleet, freezing rain, snow and/or rain .



Another storm system, lifting into the nation’s mid-section Sunday, should send mild enough readings into Chicago with its front-side southerly winds, that the bulk of its precipitation is to fall as rain.


Longer-range indications suggest arctic air may roar back into the area in the 11 to 15 day time frame



Cold weather isn’t behind us yet. Model forecasts indicate broad warming aloft across the arctic will produce a “wavy” jet stream pattern likely to tap frigid arctic air and drive it southward across much of the Lower 48 again by mid-February.