NORTHERN MICHIGAN -- When I walked into the 7&4 Forecast Center this Tuesday morning, one of the first things I looked at were the temperatures. All of the airports across our viewing area were showing 36F or higher which is several degrees above the freezing mark. What made the morning interesting (besides analyzing our incoming winter storm tonight) were the dozens of schools that closed for the day due to extensive icing on local/secondary roads.

Basically, in a nutshell what happened was that rain from the overnight froze on contact with the pavement/gravel even though the apparent air temperature showed it was well above freezing. In a way, this is a tricky aspect to forecasting, especially so early in the morning. If you were to go outside in one of the school districts that closed and look at your thermometer in the backyard, it would most likely have shown a temperature somewhere between 35-42 degrees which one would think means the roads are in fine condition since that is above the freezing mark.

What tends to happen, and what made this morning particularily tricky is that the actual pavement/gravel/surface is several degrees cooler. Items like the road/bridges/overpasses tend to hold onto cold longer. Last week, it dropped below zero in many spots, so while your thermometer might have read 35-42 degrees,  when rain touched the surface, it was more like 30-32 degrees (actual surface temperature) which again lead to many schools unable to get busses out of the garages. That 2-3 degree temperature differential between the ground and air made all the difference and is why thousands of students did not go to school today.

I often rely on those school/viewer reports for the aforementioned reasons since not many people are up that early, it's good to get a handle on where icing in occurring. As I wrote above, even though the temperature can be well above freezing, ice is still possible. -Meteorologist Joe Charlevoix