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John Wheeler, WDAY, Published November 16 2013

Weather Talk: Snow cover keeps weather colder in two physical ways

Snow cover is really the key element of winter. There are two physical ways that snow cover keeps the weather colder: its radiative properties and its thermodynamic properties.

First of all, the whiteness of snow is important because it reflects a significant amount of sunlight back into space. Less obvious, but also important, is that white snow cover also allows more of Earth’s internal radiation to escape into space. So due to snow’s radiative properties, it makes the weather colder in the day as well as in the night.

Thermodynamics is also important. Specifically, the heat required to melt snow uses up energy that would otherwise have warmed the air. When the weather manages to warm above 32 degrees, it tends to remain in the 30s as long as the snow is melting.

Record highs this time of year are in the 60s and 70s whereas record lows are well below zero. The wide range is due to the absence or presence of snow cover.

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