Bursts of snow turn thundery at Kankakee

Thunder and lightning accompanied a quick burst of heavy snow at Kankakee late Thursday. Thundersnow was also reported in sections of Indiana and Ohio. Still other snow showers slashed visibilities to a quarter mile late Thursday evening in north suburban Algonquin. The squally snows erupted beneath a frigid pool of cold air aloft which eased across the area and lingers Friday. The huge vertical temperature declines which developed produced what meteorologists refer to as an explosively unstable environment—one in which air is encouraged to ascend and cool to saturation. The result is clusters of clouds with tops to 10,000 to 15,000 feet capable of producing bursts of snow. Tiny upper air impulses embedded within the jet stream aid the process.
Thursday’s 0.2” of snow marked the 9th day with measurable snow of the month. That’s more than the typical number in a full December and triple the three measurable snows which occurred a year ago.
--Tom Skilling