Since You Asked: 'February thaw' can bring rain, snow, sun

I think these warm, clear February days need a news story. What is going on in mid-February that creates some of the most pleasant days of the year? Surely someone at the weather bureau knows what is going on. Surely readers want to know.

Here is my guess. God is smiling at the thought that there is less than one year left in the term of GWB, by far the worst president in the history of our republic. Of course, that explains THIS February, but what about February weather most years?

-- Peter S., Medford

We can't speculate about the Divinity's political proclivities, Peter, but there's solid atmospheric science behind the "February thaw," the well-known and much-loved phenomenon of Southern Oregon winters.

After months of sodden gray chill and damp, the weather gods often reward us with a taste of spring in February. It doesn't happen every year, but when it does, the sun returns and days feel downright warm, which demonstrates the principle of relativity -- 50 degrees in the sunshine in February feels positively tropical after two months of winter. If we had a spell like this in August, we'd be freezing.

To understand what's actually happening, it helps to know the basic forces that drive the world's weather. We got a brief explanation from Mike O'Brien, a meteorologist at the National Weather Service office in Medford. With apologies in advance for any errors, we'll try to pass it on:

Think of the atmosphere as a fluid, like water, with currents, turbulence and eddies. At the most basic level, warm air around the equator rises and cold air around the poles sinks, creating a circular flow. As the planet rotates, air flows from west to east. Storms happen around the areas of greatest turbulence, when huge masses of warm air run into equally titanic volumes of cold air. During winter in the northern hemisphere, we get storms.

The whole system is incredibly dynamic. Immense streams of air undulate across the continent like a Chinese dragon, bringing storms to the Pacific Northwest for a while, then going somewhere else. Right now the flow has moved north. We get mild sunny days and crisp, clear nights, while the East Coast and Midwest get cold and snow.

Enjoy it while it lasts. The seven-day forecast looks like we'll be wet again by the weekend, and maybe sooner.

Send questions to "Since You Asked," Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; by fax to 541-776-4376; or by e-mail to We're sorry, but the volume of questions received prevents us from answering all of them.

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