All Weather News

Steam Fog

7 Dec 2013, 1:45 pm

It was a cold start to the day across much of the country!  In fact, as temperatures warm up, they will still be well below daytime average high temps for this time of year.  The only warmer than average spot can be found in Florida and southeastern Georgia and South Carolina.

The cold air, while a pain to deal with, made for an interesting sight recently.  Steam fog, also known as evaporation fog, occurs when evaporation happens from a relatively mild body of water into a colder air mass just above the surface.

Here is this image from Duluth, MN (from Beacon Pointe Resort) of steam fog forming off of Lake Superior.  When this image was taken on Friday, air temps in the morning hours were in the negative single digits.  The water temperature was around 40°.  It made for a very cool picture as a ship was passing by.

This webcam shot from the same area, except taken further back, shows the extent of how far the fog rises up into the air.  It goes up and beyond the Aerial Lift Bridge in the middle of the photo.

The steam fog wasn’t just around Duluth, MN.  We saw this wonderful image on our webcam in Glacier National Park in western Montana.  The steam fog was very thick early this morning but started to thin out as the daylight hours continued to progress.  Lake McDonald looked like a steaming bowl of soup with the steaming rising off its surface.

Steam fog needs the air temperature to be cold, typically 32°F or below, so that even a small amount of moisture can produce saturate the air, otherwise the heating process will outweigh the tendency towards saturation.  The fog is typically found close to the nearby cold surfaces, such as the shore or a floating chuck of ice.

From The COMET Program, this graphic helps to show the process of Steam Fog.

Temps today will warm up, but not by a whole lot.  Here is the forecast for Saturday.

By tomorrow, temperatures will try to warm up, but many locations, which nearly all of the lower 48, will see high temps about 10 to 30° on average, below normal! Brrr!

I hope you have some place warm to go and stay at while this early season chiller lingers across the country.  Here is a look at a Sunday’s forecast.   A flight to Florida looks really good right about now, especially to anyone that lives in the Dakotas or Montana where temps will not break zero degrees in some spots.

Enjoy the rest of your weekend!

Meteorologist Addison Green ~ twitter: @agreenWNTV

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