Sketchplanations

Explaining one thing a week in a sketch

Lake-effect snow

Nature’s greatest snow machine, where crazy amounts of snow can fall in huge snowstorms on the downwind — leeward — side of a lake. Where the effect is pronounced, such as on the East of some of the Great Lakes in the US, it can generate regions known as snow belts because of the amount of snow they receive.

It works kind of like this: cold air blows over a lake. As the cold air passes over the warmer lake it picks up water vapour from the lake and it warms. This causes it to rise and in turn cool, such that when it reaches the downwind side of the lake it is now a lot of cold moist air which can cause some incredible snowstorms, like 2–3 inches of snow per hour. Satellite pictures like these show it in action pretty clearly. If the land rises after the lake the air can cool faster and increase the effect — and also cause a rain shadow — and if there’s a whole lot of convection and the air is rising fast you can get what’s called thundersnow — a thunderstorm in a snowstorm. I know.

Stay warm out there.

Find weather interesting? Me too. You might also be interested in: Dirty thunderstorms, thunderclouds, yesterday’s weather (applying weather forecasting to software engineering), rain shadow, lenticular clouds, know your cirrostratus from your altocumulus, and British weather.

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