First of all, let me start off with some historical statistics about snowstorms compiled from John LaCorte of the NWS office in State College.
- Major blockbuster storms of a foot or more have occurred on average once every 3 to 5 years in the past. They are rare, but some years we have multiple events and we have gone through very long stretches without such a storm.
- Snows of 6" or more average about 1 to 2 times in an average winter.
- Snows of 1-3" occur on average 10 times a winter.
- Upslope areas near and west of Route 219 will get 2 to 3 times more in the number of 6" events. Often these will be called Lake Effect, but many times it is simply the air forced up the mountains that enhances these events.
Since rumors are abundant for events, here are some other important things to take when judging upcoming events.
- Forecasted amounts that are given 24-36" before the start of a storm should be treated as suspect. Often these are headline grabbers that may be off of a single model. There's simply too much that goes into snowfall and judging specific amounts that far in advance is not accurate. A simple change in the track of a storm of less than 60 miles can mean the difference between a foot and nothing.
- A winter storm watch means that there is a potential for an event to bring 6" or more. This is not a forecast of 6" or more but states the chance is there at a longer range. Three things will happen to a watch. It will be upgraded to a warning, go to an advisory or it will simply disappear because the event will not come together in the worst case scenario.
- For major storms, look for the storm to track somewhere between near Philadelphia and Harrisburg. Any farther to the east or west does not bode well to heave events here in Central PA.
- Once a storm gets north of your latitude, then the major accumulations are done east of I-99. Near and west of Route 219, the opposite is true. Often, the cold air wrapping in behind the storm on a westerly flow can enhance snow in these regions.
- Rain to major snow storms rarely pan out in our region.
- Light freezing rain and freezing drizzle events often can cause more problems than major events. The reason why is that they are tougher to forecast, get less attention and drivers don't perceive these events as a threat until it is too late.
Lastly let's take a look at average snowfall in Pennsylvania.