Foggy Start Once Again

With these temperatures near and above freezing, we're seeing a lot of melting throughout the day giving us plenty of slush and melted snow on the roads. First we have the melting and once the snow is melted, we begin to have evaporation where the liquid transforms into a gas, or water vapor. Since temperatures are so warm, and warmer air can hold more moisture without clouds (water vapor) showing up, we're fine during the day. But when temperatures drop back off, we still have that same moisture in the air, and cold air can't hold moisture as well as warm air does, so the moisture in the air begins to condense and adhere to particles in the air (thus forming a cloud or water vapor). Since all the moisture was evaporating at the ground surface/near and on the roads, that's where most of that moisture stays in the air, so that's also where the "cloud" will form during the overnight. When this occurs it's the formation of fog, since fog is actually a cloud that's lower in the atmosphere - the lowest cloud you can get! Visibilities aren't so terrible to warrant a dense fog advisory - but it's always good to be aware of the moisture on the roads before you head off to the roadways. It seems we always have several accidents to report on when we have these type of conditions, so slow down a little and give yourself some time this whole week since we'll see the temperatures continue to stay above average for this time of year. So just be prepared for areas of patchy fog will pretty much be possible every time we see melting during the day.

Be safe!
~KDLT Meteorologist Jesse Ritka