You probably noticed a few times where the temperatures were slightly above freezing and it is snowing! How is this possible? Shouldn’t the snow melt when it’s above 32°F?
First, let’s take a look at how we get snowfall in any situation. In the lower atmosphere, temperature typically decreases with height and eventually drops below freezing. If a cloud forms in an area with temperatures below freezing and has enough moisture, snowflakes will start to form.
As the snowflake becomes bigger, it gains weight. At some point, the cloud can’t hold this weight anymore and the snowflake falls to the ground.
If the air from the cloud to the ground is below freezing the whole time, the snowflake will stay frozen. However, if warm air is in place between the cloud and ground, the snowflake will begin to melt.
Depending on the characteristics of the warm air, you can get sleet, freezing rain, rain, and even snow with temperatures above freezing.
For snow with ground temperatures above freezing, you want a very thin warm layer just at the surface. This is so the snowflakes don’t have enough time to melt completely as they fall. In fact, the snowflakes are starting to melt when they hit the ground.
As this happens, snowflakes can get stuck together and clump together. This is why the flakes may appear bigger than usual and accumulation is usually very minimal.
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