November 30, 2006
Winter weather forecasting is a very challenging aspect of a meteorologist's job. A single degree above or below the freezing mark can mean the difference between a foot of snow or an inch of cold, miserable rain. Wait! We can't forget about freezing rain and sleet! That being said, how can a forecast be made out several months in advance with all of these complex variables?
To create the building blocks of a winter weather forecast, it is essential to know what can be expected in a typical winter for a specific area. Average snowfall across central Virginia is slightly under two feet for the entire winter. While some winters bring more and some bring less, this is a good starting point for the forecast.
Next, El Niño is a large player in the weather all over the world. A moderate El Niño is developing as we speak. El Niños typically mean cooler and wetter than average conditions across the Southeast and the Gulf. Unfortunately, moderate El Niño events have brought widely varying amounts of snowfall to our area, which does not really help our forecast. Thankfully, there are other factors we can consider.
One of the oldest methods of forecasting is called the persistence method, meaning, the trend of weather now will carry over into the next few days or months. From January until August, most of the area saw much warmer than average weather and very dry conditions. Then in September, the pattern completely changed. Every month since September has been wetter and cooler than average.
This pattern that we are in now, combined with the fact that El Niño years are typically cooler and wetter than normal leads me to believe that this winter will see slightly above average snowfall totals. My official forecast calls for 25" - 30" before the winter season wraps up. Now the prediction has been made and we will just have to wait and see how it all pans out!