This is the time of year you’ll see various winter outlooks predicting how much snow and cold we are going to have in the upcoming months. Let me say at the outset I am not making a prediction in this article, but I am hopefully going to help you understand how to interpret the ones you do see.
In a general sense, winter is the most impactful season for us here in New England. We can have severe weather and even hurricanes in other seasons, but those are much less likely and in the winter we know it’s going to snow and be cold, it’s just a matter of degree.
For the National Weather Service, the winter outlook includes December, January, and February. For many other prediction sources, such as the Farmers’ Almanac, the winter outlook includes all the snow that’s going to fall between now and April.
Let me say at the outset that these snowfall predictions are fun and have some scientific merit but also are often highly inaccurate. The reason for this is the nature of snowfall here in New England and how variable it is.
Take a look at the three maps below representing the departure from average snowfall. I did not come up with the color scheme so you have to look at the key at the bottom. It shows whether snowfall is above or below average for a particular season.
Notice that last season most of the area, with the exception of Greater Boston, had below-average snowfall and in some cases it was significant.
The previous winter was close to average.
Our blockbuster winter back in 2015 showed above-average snowfall for parts of Southern New England, yet the farther west you went the anomaly decreased significantly and was even below average. The reason for this is that winter storms have very unique features that can often produce pockets of very heavy snow in one area, less snow in another, and even rainfall close by.
Most winter predictions look at the state of our oceans, which are the primary drivers of seasonal weather. This year, like the past two years, La Niña is our primary driver.
It is forecast to remain in place during the beginning of the winter but then may wane as we head towards late winter and spring. This is a triple La Niña, which is fairly unusual. This will only be the third triple-dip La Niña since 1950, the last one occurring from roughly the summer of 1998 until spring 2001.
The NOAA predictions are based on probability. Although NOAA’s map shows warmer-than-average conditions, this just means that conditions are favorable for that but doesn’t mean it’s going to be a warm winter. As a matter of fact, we’ve had winters that end up warmer than average but still have a lot of snow and cold because an extremely warm month can outweigh two slightly colder ones.
How December, January, and February will average out remains to be seen but do not take the odds of it being warmer than average to mean that we will have an easy winter ahead. The chart below shows the average temperature for the past 30 years as well as for a century earlier.
Most of our winters end up above average and if you compare all of our winters to what went on a century ago, they are warmer than average.
There’s actually been an increase overall in our snowfall average, which continues to be highly variable season to season.
Climate change does play a role in all of this, favoring warmer winters and more precipitation. Even a drier-than-average winter can produce above-average snowfall.
The average precipitation level from November through March is about 21 inches. If we only had 50 percent of average but it all fell as snow, we’d end up with roughly 100 inches of snow, far above average for what would have been a dry winter. Conversely, if most of the precipitation fell as rain instead of snow, we could end up with a wet winter.
I can guarantee we’re going to have cold weather this winter and it will snow but as far as exactly how much of either your specific town sees, we won’t really know until April.