Coldest Christmas Eve in 9 years: 1-minute forecast

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Blog post by, Tom Skilling

The latest bone-chilling blast from the arctic restricts Tuesday’s high temperatures to the mid teens—the coldest of any day to date this season.  But even more impressive is the fact these readings translate to the coldest daytime temps on a Christmas Eve here in 9 years. Not since 2004 has a Dec. 24th been colder.

Tuesday opens with 10 to 20-below wind chills

The expansive cover of snow produced west of the city by this past weekend’s snowstorm has paved way for the bitter chill which greets Chicagoans Tuesday.

The snow pack reflects away a good deal of the incoming sunlight’s energy which might otherwise ease the chill.

Winds chills of 10 to 20-below greet those venturing outdoors Tuesday morning.

Monday’s frigid air plays important role in generating some eye-catching optical effects most common in the arctic; “sun dogs” and “light pillars” observed across greater Chicago area

Tiny ice crystals suspended in Monday’s bitterly cold air mass played an important role in producing stunning displays of “sun dogs” Monday. Sun dogs occur as a result of refraction of incoming sunlight as it passes through airborne crystals floating in the day’s frigid air. What results are bright patches of light on either side of the sun when it’s low on the horizon, as happens near sunrise and sunset.

We’re grateful for the myriad photos so many of you shared with us by way of e-mail and on Facebook Monday.

Another optical effect, most often seen in the arctic but visible across sections of the Chicago area Monday, were what are known as “sun pillars”.  These vertical shafts of light emanate from light sources—including the sun and streetlights.

The snow being predicted Tuesday night is the product of milder, moister Pacific air riding up and over the arctic air mass currently in place

Chicago may well be in line for its first “white Christmas” in three years Wednesday. Christmases are said to be “white” when and inch or more of snow is present on the ground at some point Christmas day.

A clipper-like disturbance, sinking southeast from Canada into the Plains and Midwest and associated with a disturbance embedded within the jet stream, is to bring clouds and a period of snow into the area late Tuesday night into Christmas (Wednesday) morning.

Mild, moist Pacific air is behind this predicted snow. The moisture is running up and over the arctic air currently in place, a process which encourages cloud and snow formation. The best estimates place potential late Tuesday night/Wednesday morning accumulations in the range of 1 to 3 inches.

Windy Saturday mild spell to be followed by an even stronger arctic blast late this weekend into next week in time for New Year’s Eve and 2014’s open

Impressive temp swings loom this weekend. Gusty southwest winds propel milder air into Chicago and the Midwest Saturday. Temperatures are likely to break above freezing as this occurs.

But, the development of ridging (northward buckling) in the North American jet stream pattern due to abnormal “warmth” predicted over Alaska and eastern Russia this weekend, is to contribute to the development of a full-blown “Siberian Express” pattern heading into next week. Such a pattern involves jet stream winds which blow from Siberia in Russia across the North Pole and into North America.

Early indications are that bitterly cold arctic air, which is to sweep into the Midwest as the flow pattern becomes established, may generate the coldest daytime temperatures observed here in the 5 years since 2009.

Temperatures are likely to fall Sunday to sub-zero levels by Monday morning.  And if our current forecast of a 5-degree high verifies on Monday followed by a low of 8-below Monday night/Tuesday morning, the frigid outbreak would become this area’s coldest since extremes of 1-below and 13-below occurred January 15, 2009—nearly 5 years ago!

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