Predicting Snow in the Hampton Roads Area... Why is it so challenging?
It is never easy for meteorologists in our area when the rain/snow line is going to be close by. I am not trying to make excuses for meteorologists here locally, but I want to try to explain why they face a difficult and challenging forecast with situations when the rain/snow line is going to close by. Problem 1) The Ocean: We live next to a body of water that is in the 40s normally during the winter months. If the wind blows from the ocean, the temperature cannot be cold enough at the surface to support snow right along the coast. Further out to sea to our southeast is the warm Gulf Stream waters. A southeasterly wind blowing from water that is in the 60ís eliminates any chance of snow for our area. However, a northerly wind or even a north-northeasterly wind can be cold enough to support snow as long as the air to our north is very cold to start with. Problem 2): The Ocean again: The ocean provides storms their energy and moisture, so as a low pressure area moves towards the coast, it can intensify very rapidly, and sometimes surpass what forecasters were predicting. This rapid intensification can result in heavy precipitation. This brings us to Problem 3) When precipitation falls heavily, it can bring colder temperatures to the surface and change the rain to snow. Low pressure areas that are intensifying rapidly cool the upper air behind them, so storms intensifying to our east cool the atmosphere to their west (over our area) which also can change the rain to snow. There are other variables that affect our weather such as dry slots, but these are the major things that have to be considered locally when issuing a forecast for snow. Note that Norfolk averages just under ten inches of snow a year.