Crozet Weather Almanac: January 2011

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By Heidi Sonen & Roscoe Shaw

weather-chart-jan-2011bWicked Winds of Winter

As a fellow Crozetian, you know what we’re talking about. The weather will be calm and pleasant and then suddenly, the screen door starts whacking the house and the trees sway and you feel like you are in the Wizard of Oz. Worse yet, these winds last for 24 to 48 hours and blow a steady 30 mph and gust to 50 mph.

Meteorologically, these are called “downslope windstorms.” They happen just down-wind of a tall mountain ridge. Often, when we are gusting to 50 mph, the Charlottesville airport is only hitting 20 mph.

Heidi and I had a professor in college who was an expert in this. He would lecture with great enthusiasm and in great mathematical detail about how and why they happen. The description is complicated, involving gravity waves and complex differential equations. We would fight back sleep in class and never did really understand the physics. However, we have learned to forecast them pretty well.

This phenomenon happens in Crozet when strong winds blow perpendicular to Bucks Elbow. If this west-northwest wind combines with an unstable atmosphere near the ground and a stable layer aloft, watch out! This happens once every week or two in the winter and spring, usually after a snow or rain storm passes.

We email wind damage pictures to our former professor. He gets quite excited, since all the previous research suggested that the Appalachians were too small to produce these winds.

January in Review

January was another cold, dry month. Believe it or not, this winter has been three degrees colder than last winter’s record snow year and five degrees below normal. But snow is almost a random event here. Last year produced 52 inches of snow and this year just 5.4 inches so far. A dusting of new snow or more has accumulated 15 days this winter but we can’t seem to get a big snow.

February will bring longer days and the first hint of spring. The average daily high is just 45 degrees in the dead of January but rises to 52 by the end of February and up to 64 by the end of March.