After a day that brought a variety of weather across the Chicago area, including hail-producing thunderstorms and rain and sleet, the precipitation potpourri shifted to a heavy, wet snow across the area Sunday evening.

The temperature dropped below freezing and many areas quickly acquired a accumulative snow cover. Totals could vary dramatically because of melting and the potential for heavier bursts of thunder-snow, which appeared to be targeting the south suburbs and northwest Indiana. The snow should diminish to flurries Monday except for some heavier lake-effect snow that is expected. Wind-chills are expected to remain in the low 20s much of the day.

No two snowflakes are exactly alike, but their forms usually fall into several basic types. During snowfalls look closely at snow and you will see beautiful snow crystals made of ice. Many people think snowflakes are made from frozen raindrops, but this is simply not true. A snowflake forms when water vapor in the air condenses directly into solid ice. As more vapor condenses onto a nascent snow crystal, the crystal grows and develops. Amazing crystal structures appear during a simple act of water condensing into ice. The shape of snowflakes is formed by different air conditions during snowfalls. They are complex, symmetric and in varying designs. Snowflakes are the product of a rich synthesis of physics, mathematics, and chemistry. They are even fun to catch on your tongue :) Below you can see close ups of snowflakes, there's a lot more to see than you might think!

Also there are shapes that look totally different than usually imagined. Take a look at these beautiful ice crystals.

Pictures taken from SnowCrystals.com

Indiana snowbelt residents were hit Tuesday afternoon and evening with large amounts of snow - coming from the lake. In some areas of Lake, Porter, western La Porte counties in northwest Indiana reported snowfall rates of 3.5 to 4 inches per hour, which makes it a new record compared to the hourly snowfall rate in Chicago on February 23 1967. Final snow accumulations reached or exceed 20 inches in some areas of northwest Indiana. Take a look below at some pictures taken during the snowfall event. 

    

Based on trends observed during 124 year observations, Chicago land has 14 measurable snow days still to come beyond January 29. To date we had 31 days with measurable snow, which puts us in the top 3 rank in 124 years!

Looking back at the six snowiest winters to date since 1884, pace of snowfall slowed down in four of them (67%) after January 28. Below bar graph shows average snowfall after January 28 and full season totals (rounded to the nearest inch) for Chicago's six snowiest winters to date. 

 

In a historical perspective, in 6 previous winters (nearly as cold and as snowy as current one), 67% of those winters continued cold and recorded slower snowfall rates. Least observed snowfall was 9.5" and greatest was 27.5". 124 year average show snowfall after January 28 at 17.5" 

As you can see from the graph below, currently we have the 15th coldest winter in Chicago! The average temperature to date is 20.3° which is 7.8 degrees colder than last winter at this point. Additionally we are in the middle of the snow season. More than 50% of snow still to come! January is the snowiest month in Chicago - based on long-term average monthly snowfall (1884-2008).

 

As you can see, last years winter was the 7th snowiest winter in Chicago. Maybe we will beat the 89.7" in 1978-79?

Measurable snow fell Wednesday for the 19th time, totaling 2 inches at O'Hare International Airport since Tuesday and pushing the city's official tally past the 2 foot mark (24.5 inches). The 2008-09 season is one of only five in the past 124 years in which measurable snow (0.1-inch or more) has fallen that frequently. Over the term of official snow records dating back to 1884, an average of 10 measurable snows has visited the area by Jan. 8 with a seasonal snow tally to date closer to 12 inches—half as much as has fallen to date this season. Nearly 66 percent of the city's seasonal snow typically falls beyond this date.