Have you ever wondered how or what decides whether the precipitation falling from the sky is in the form of rain or snow? Sometimes the air temperature is 32 degrees F and we get rain, while other times it’s 33 and it snows.
Much depends not only on the temperature at ground level (where you happen to be), but also on the temperature of the air above you. Sometimes-especially during March and April- there can be a layer of very cold air several thousand feet above you. As the atmosphere warms, this cold layer of air becomes increasingly unstable, which can eventually cause some form of the precipitation. If at the higher altitudes it is below freezing, the precipitation falls as snow. Near the ground, there might be a very shallow layer of warmer-than-freezing air. As the snowflakes descend through the warmer air, they don’t have enough time to fully melt; instead they turn into very large snowflakes (sometimes the size of silver dollars!) in such very special conditions, you can have a snow fall, even if your backyard thermometer is reading well above freezing.
This is reversed when there is a very shallow layer of below- freezing air near the ground, while the air several thousand feet above you is unusually mild and warm. Precipitation that falls is liquid (rain). Upon falling into the shallow cold layer near the ground, either it freezes upon contact with surfaces forming a glaze (freezing rain) or the raindrop itself freezing before hitting the ground (sleet).
When will it snow in your neck of the woods? Check out the Farmers’ Almanac forecast for your zone.