Slick Morning Commute

A Winter Weather Advisory has been issued for Winnebago, Boone, McHenry, Ogle, Lee, and DeKalb counties through 9am. Areas of patchy freezing drizzle are mixing in with flurries this morning, creating areas of black ice on untreated roads. The freezing drizzle and glaze of ice has been more concentrated near the Chicago area and it's suburbs. But still poses a slick commute for many of us across the Stateline. Take it slow this morning and use caution while driving, but also on sidewalks, parking lots and bridges where a glaze of ice will still be possible. As we know, its very difficult to see black ice until you're on it, so take it slow through the morning.

The formation of freezing drizzle is all based on the thermal profile in the atmosphere. When the atmosphere all the way up is warm, well the precipitation falls as rain. When you get warm air aloft, and a shallow freezing layer then the precipitation melts and falls as rain, but then refreezes on contact with the freezing surface. This then creates a glaze of ice on untreated roads. When the atmosphere has an upper level layer of warm air, but also a fairly deep cold layer the frozen precipitation falls from the clouds, melting through the warm layer, and then refreezes before hitting the surface. Finally, when the atmosphere is all cold, then we get snow.