On average Chicagoans can expect three intense cold waves every winter, and most do not last long (though, admittedly, they last long enough for the fancy of most of us). In the Chicago area they are unlikely to last more than four days. However, the cold wave that descended on Chicagoland on the last day of 2009 and continues today is giving strong indications that it's going to linger well beyond the normal four-day life span. Strong winds from the north and northwest at the 20-30 thousand foot level -- the level of "steering winds," so-called because they direct the movement of air masses at the surface -- are likely to persist for 7-12 days. In response, air masses originating from the frigid reaches of northern Canada will dominate Chicago's weather through that period.
Lake-effect snow to bury northern Indiana
Northwesterly winds and persistent cold at Chicago invariably mean persistent lake-effect snow in the snowbelt areas of northern Indiana and southwest Lower Michigan. Impressive snow totals, possibly measured in feet, are likely there in coming days.
Lake-effect snow to bury northern Indiana
Northwesterly winds and persistent cold at Chicago invariably mean persistent lake-effect snow in the snowbelt areas of northern Indiana and southwest Lower Michigan. Impressive snow totals, possibly measured in feet, are likely there in coming days.
