Wednesday, January 30, 2008

Steam Fog

Steam fog rising up off Flathead Lake, MT

Driving home from Whitefish down Flathead Lake I was treated to a steam fog of incredible magnitude.

It was cold. Very, very cold. During the two minutes I was out of my truck to snap photos in the railyard my fingers had frozen to the point of complete numbness. Earlier that morning my truck had started grungingly after a 15 second performance. It was -15 degrees. Seeley Lake had reported -38. If I'm not mistaken, I believe spit bounces at that temperature. That's scary cold.

Danger Keep Off.

Steam Fog, according to Weather and Climate by Paul E. Lydolph is:
Formed by the injection of more water vapor into nearly almost-saturated air when cold air is advected across a relative warmer water surface. In middle latitudes this is a frequent occurrence over lakes and river during early winter, before the water surfaces freeze. Because the vapor pressure of the cold air above, moisture moves upward from the water surface into the air, even though the air might already be saturated. Almost immediately above the water surface, the water vapor will recondense into liquid water droplets and form fog. Since heat is also being added to the lower air, active turbulence will mix the water droplets upward into the air. Under such conditions it appears that steam is "boiling up" from the water's surface, hence the name "steam fog." With extreme water-air temperature differences, this sort of fog may take on the appearance of low cumulus clouds based near the surface and extending a hundred meters or more into the air.

This was the case, as at times the fog stretched completely across US93.

Fog stretching out onto US93 at the Lake County line.

Some wonderfully whimsical metalwork victim of a very irreverent sign-hanger.