Wednesday Weather Whys: Snow Above Freezing

A common question is how can it snow when the temperature is above freezing? This is a very complicated subject and a difficult question to answer. The concept is the wet bulb temperature. Basically, the air above the ground must be below 32 degrees; however, there is a very shallow layer of temperature at the ground above freezing. The air is not 100% saturated with moisture, so some of the snow is being evaporated into the air before it hits the ground. This evaporation is causing the air to cool, and the end result is the air temperature begins to cool. Eventually, the temperature will drop to freezing or the snow will change over to rain.