Great Lakes part of Christmas Storm system packing near-blizzard conditions, possible tornadoes. Updated Dec 24, 2020; An expansive storm system is crossing the eastern half of the U.S. today and Christmas Day. The storm will produce weather woes ranging from near blizzard conditions to possible tornadoes. First let’s cover the Great Lakes weather. Cold air has moved in, and the dangerous weather will be in the form of heavy lake effect snow. Lake effect snow is somewhat limited in areal coverage. The warning map below gives you a really good feel for where driving will be difficult. Winter storm warnings and advisories in effect as of 10:00 a.m. December 24, 2020.