Snoweater
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Hi, I'm Dave Thurlow for the Weather Notebook. Here in the middle of the summer we have a cool question from New Hampshire Public radio listener Richard Carey. Last March, he wrote the following:

"I am watching the mist hovering over frozen Lake Winnipesaukee following a warm spring rain. Mindful of the old wives tale that "mist eats snow," I contend that the mist in the air is the result of moisture rising from the icy lake surface and condensing in the warm air. Which is cause and which is effect?

Does the fog-making moisture come from the ice or the air? Moreover, how does it eat snow? To start, the fog doesn't come from the lake surface. The air that accompanies a warm spring rain has a lot of moisture in it. If the air cools down, the moisture in IT will make fog. As the air over the frozen lake cools, the water vapor in the air condenses, turning into fog. The coolness of the ice and snow help make the fog.

The snow eating begins when water vapor in the air condenses to fog. It releases heat, while evaporation takes it away. This heat helps break ice crystal bonds, melting the snow below. Snow cools the warm air above. The moisture in it turns into fog, releasing heat that melts the snow. Let's get back to summer.

The Weather Notebook is a production of the Mount Washington Observatory in North Conway, New Hampshire. It is funded by the National Science Foundation. And, is underwritten by Subaru: The beauty of all-wheel drive.