ROCHESTER, N.Y. – One of the biggest challenges for a News 10NBC First Alert meteorologist is predicting the type of precipitation for this time of the year. It can be just about anything on the meteorological menu including snow, rain, freezing rain, or sleet. The variety of winter precipitation is due to a warm front, part of the components for a mid-latitude cyclone (a large storm). That warm front produces what is called “overrunning”. The overrunning occurs when warm air rises over the top of cold air. In this case, the cold air is heavier and more dense which means it hugs the surface of the Earth while the warmer, lighter air steams over the top.

Seems simple enough, but the complication comes about when determining how your location changes in relation to the shifting position of the warm front. As the warm moves from one location to another, so does the depth of the cold air. As a result, this changes the type of precipitation over a very short distance. Imagine a three-dimensional view of the atmosphere (our video will help with this). If we have warm air all the way down to the surface it will be in the form of rain, but if there is a wedge of cold air at the surface this may produce freezing rain. In this instance, as the rain falls into the cold air it then freezes on contact with any surface. If the wedge of cold air is a little deeper, the precipitation could be all sleet. However, if the column of air is entirely below freezing it will likely be an all-snow event.

As mentioned above, the real complication occurs when the warm front is moving and meandering from one location to another. At this point, we can get all the wonderful varieties of winter precipitation. This is just one of the many “joys” of living in Western New York.