Holiday Weekend Filled with Fog and Drizzle

The weather this weekend may have been a little frightful for travelers in the Midwest.  From blizzard conditions over the Dakotas to heavy rain producing thunderstorms in the mid-Mississippi River Valley, we had quite the range of weather.

Locally it wasn't as bad, but we did have quite a bit of cloud cover and dense fog Sunday evening.  The clouds and fog were caused by an inversion.  An inversion happens in the atmosphere when warmer air occurs over a relatively cooler surface.  Temperatures were warming into the 50's a few thousand feet above due to strong southwest winds, but temperatures at the surface were not able to warm as fast.  Inversions work to trap moisture close to the surface creating low clouds and fog. That's exactly what happened over the weekend.  Strong southwest winds ahead of a developing low pressure system pulled in an extremely warm air mass into the Great Lakes.  But because of the snow on the ground our surface temperatures were not able to warm as fast.

It wasn't until the rain and drier air aloft came in this morning that we were able to break out of the overcast and foggy sky.