National Weather Service United States Department of Commerce

We're all aware of the uncertainty that comes with a snowfall forecast during the winter.  For any snowstorm taking aim on our area, you will likely hear a number of snowfall forecasts that originate from us, local media and the always reliable grocery checkout line.  Snowstorms are very complicated events with many elements (temperature, moisture, forcing - some subtle, some obvious) that need to come together just right to produce snow. 

All meteorologists use extremely sophisticated numerical weather prediction models to help guide us toward what we hope is a reliable forecast of winter precipitation.  But, a major source of uncertainty is introduced when all too often these models disagree on how a particular event will unfold. 

What the Probabilistic Snowfall Experiment will try to do is corral, or more technically ensemble, all of these solutions (57 in all) and put a probability (or chance) on specific solutions occurring.  Here is more detail about how this is done.

Traditional forecasts have only given a single forecast for snowfall, though they can change from day to day as the event approaches. The goal of this experiment is to provide the "Goal Posts", or range of possibilities for a specific winter event.  We hope this enables better decision-making.  Another way to look at it, for a winter storm we want to be able to say, "You can expect at least this much" - "This is the most likely amount" - "You may want to prepare for the potential of this much"

You'll see these snowfall predictions on our Probabilistic Snowfall Experiment page.  Here is an example from an office out east:


In addition to the Min/Most Likely/Max snowfall graphics, we will provide graphics showing the probabilities of exceeding certain snowfall threshold amounts in whole inches.  See below:


Again, here is the Probabilistic Snowfall Experiment page.  There is other winter weather info on this page as well, we hope you find it useful this winter.

Now, all we need is snow!