Tuesday's unlimited sunshine is likely to put a bounce in the step of many Chicagoans while dazzling still others. No wonder! Sunshine's been an incredibly rare commodity here, especially over the past 12 days. December 2009 has been the cloudiest and least sunny of any December in two years. For sunshine to be in short supply this month isn't a surprise. December has historically been the area's cloudiest month---but this year's limited sun is paltry even by December's undemanding standards. Through sunset Monday, only 3,994 of the month's possible 15,475 minutes of sun occurred here, reports veteran National Weather Service observer Frank Wachowski. That's just 26 percent of the area's possible sunshine--far from the 39 percent most Decembers produce. Over 7 consecutive days--from Dec. 17 through Dec. 24---the sun never even put in an appearance. Fleeting rays did show up for 10 minutes Dec. 25 only to disappear Dec. 26, then appear for a fleeting 8 minutes on Dec. 27.
Lack of sun not the only story--December snow has been plentiful
This month's nearly 20 inches of snow is almost three times the normal tally of 7.4 inches through Dec. 20--heavy enough to rank the 9th snowiest Dec. 1-28 period in 125 years. Not only is the tally to date impressive but the frequency of measurable snows this month has been running at twice the average pace. There have 12 days with at least 0.1-inches (the amount considered "measurable" snow) compared to the long term average of 6.
But the break in the weather Tuesday may not last long. A new weather system is targeting the Midwest with snow Wednesday afternoon into Thursday followed by an outbreak of frigid arctic air likely to render New Year's Eve and Day (Thursday evening and Friday) more than a bit nippy.
Early thinking on potential mid-week snow accumulations
The system predicted to bring Chicago clouds and snow Wednesday afternoon into Thursday moved into the West off the Pacific Monday. It is predicted to cross the Rockies in coming days emerging in the Plains before making its move on the Midwest. Details of Chicago's potential mid-week snowmaker will become clearer as the system moves over land where weather balloons are able measure its structure with special clarity. Raw computer model snowfall estimates suggest an average of 2.2 inches of snow may fall here from the 0.14 inches of moisture the system is to produce. This suggests another dry, fluffy snow may be in the cards. But yet another snow accumulation forecast technique, which takes into account the rate at which temperatures change 39,000 ft. above the ground---the so-called B.J. Cook technique---hints at possible 3 to 5.5-inch tallies. Forecasters will be monitoring this system carefully in coming days.
December 2009 on the books as the city's 9th snowiest to date
December has already logged a monthly snowfall of 19.7 inches---nearly three times its long term (125-year) average average of 7.4 inches.
Lack of sun not the only story--December snow has been plentiful
This month's nearly 20 inches of snow is almost three times the normal tally of 7.4 inches through Dec. 20--heavy enough to rank the 9th snowiest Dec. 1-28 period in 125 years. Not only is the tally to date impressive but the frequency of measurable snows this month has been running at twice the average pace. There have 12 days with at least 0.1-inches (the amount considered "measurable" snow) compared to the long term average of 6.
But the break in the weather Tuesday may not last long. A new weather system is targeting the Midwest with snow Wednesday afternoon into Thursday followed by an outbreak of frigid arctic air likely to render New Year's Eve and Day (Thursday evening and Friday) more than a bit nippy.
Early thinking on potential mid-week snow accumulations
The system predicted to bring Chicago clouds and snow Wednesday afternoon into Thursday moved into the West off the Pacific Monday. It is predicted to cross the Rockies in coming days emerging in the Plains before making its move on the Midwest. Details of Chicago's potential mid-week snowmaker will become clearer as the system moves over land where weather balloons are able measure its structure with special clarity. Raw computer model snowfall estimates suggest an average of 2.2 inches of snow may fall here from the 0.14 inches of moisture the system is to produce. This suggests another dry, fluffy snow may be in the cards. But yet another snow accumulation forecast technique, which takes into account the rate at which temperatures change 39,000 ft. above the ground---the so-called B.J. Cook technique---hints at possible 3 to 5.5-inch tallies. Forecasters will be monitoring this system carefully in coming days.
December 2009 on the books as the city's 9th snowiest to date
December has already logged a monthly snowfall of 19.7 inches---nearly three times its long term (125-year) average average of 7.4 inches.
