February’s opening 2 weeks running colder than January

Longer days and stronger, more-direct sunlight generally drive February temperatures to levels above January’s.  But in a 2012-13 cold season filled to date with unusual meteorological twists and turns, it shouldn’t surprise us that February’s opening two weeks are traveling their own unique path.

 

With Chicago’s February average temperature at 25.6-degrees to date, the month’s in the unusual position of running colder than January (26.6-degrees). That’s not typical because January has most often ended up the city’s chilliest month of the year.

 

At this point, February, 2013’s opening 15 days are running 5.7-degrees colder than a year ago—but 1 degree milder than last month.

 

Saturday to feature the area’s coldest temperatures of the past 2 weeks; Sunday to see a modest temp recovery begin

 

Cold, late-season arctic air has posted a bit of a comeback as we head into February, 2013’s third weekend.

 

Saturday’s predicted 24-degree high is to be the city’s coldest since a 21-degree maximum on Feb. 3.  That’s a big change from a year ago when Chicago’s official high on this date topped out at 47-degrees—a reading 23-degrees warmer!

 

Meteorological spring’s arrival is just two weeks away yet the coming week is to host two storms

 

Weather forecasters close the books on the three-month (December through February) meteorological winter season March 1. The winter-weary will be pleased to know we’re just two weeks away from that bench-mark date and the start of meteorological spring. But, while the calendar signals the winter season’s move into its closing days, two storms—the second of them potentially the most wintry and strongest—loom for Chicago and the Midwest.

 

Storm number one sends roaring southerly winds into Chicago Sunday night and Monday—a development expected to send temps into the low 40s as the new week gets underway and promote “rain” rather than snow. The rain arrives by Monday afternoon and may switch briefly to a period of light snow or flurries Monday night.

 

Storm #2 is sending more wintry signals Thursday afternoon, Thursday night and Friday. The system’s strong front-side southerly winds out of the Gulf of Mexico are to send a rich stream of moisture north into the Midwest, a development expected to promote the formation of a messy shield of mixed sleet and snow starting Thursday afternoon.  Precisely how much snow may fall—and whether the system’s warm, moist inflow could force some liquid into the mix as well—are all questions far too early to answer.

 

Several models develop a sprawling and powerful high pressure to the north which could try to inject drier air into the lower atmosphere as the storm approaches. As moisture-rich air arrives and precipitates into this layer of dry air, evaporative cooling may overcome the usual tendency for snow to shift toward rain in this environment. That would be a development which would keep much of the precipitation in the form of snow. But, that’s hardly the only possible scenario. Another would have initial snow and sleet mix with rain.  It’s impossible at this early stage to know which scenario is likely to prevail. Details such as this will become clearer to forecasters over the coming week as newer data arrives.

 

One way or another, what is abundantly clear is that the late week system may well be the source of a period of messy weather in the Thursday afternoon to Friday time-frame. We’ll continue to keep you informed.

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