Here's an atmospheric riddle: How can you wake up to icy, snowy roads when there's no storm within 500 miles of home? The answer: ice fog.

When skies are clear with light winds, lazy clouds can form at ground level, a phenomenon better known as fog. Very light snow and freezing drizzle falling out of this grounded cloud deck can ice up roads and confound commuters. "Where did this come from?" Melting snow moistens the lower atmosphere, increasing the potential for these pesky ice fog events.

MSP has picked up 7.3 inches of snow so far this winter season. That's less than Omaha (9.1 inches), Lubbock, Texas (10), Chicago (13) and Roanoke, Va. (15). Roanoke?

That crusty, gently used 4 inches of snow on the ground in the Twin Cities may be down to 1-2 inches by the end of next week. A white Christmas this year? Touch and go.

Big storms track well south and east of Minnesota the next two weeks, with a milder, Pacific flow for the Upper Midwest. We may see a few days near 40 next week.