When can we expect snow again this winter?

Now that we’re midway through winter, I like looking into the meteorological crystal ball and attempting to figure out how the atmosphere might behave in the coming weeks. Generally, the next six-week period can be some of the snowiest of the entire year for New England.

The most forecasters can do at this point is make educated guesses. Mother Nature always loves throwing us surprises.

Let’s first look at some averages for the upcoming weeks and then evaluate some of the model data.

It’s worth noting that the distribution of snowfall in the final six weeks of winter leans heavily toward February. By the end of the month and certainly in March the chances of seeing more than 4 inches of snow dramatically decreases.

You can see on the graph below how the frequency of larger snowstorms ramps up during February but then quickly tails off. Of course, these are just averages.

New England did experience a major April snowstorm back in 1997, and another impactful storm unleashed several inches of snow in April 1982. But people usually remember well the winter of 2015, when Boston broke its all-time record for snowfall in one season — 110.3 inches — mainly from late January through February.

But that pattern was highly irregular and unlike that winter, we are still in an El Niño – albeit weakening. El Niño is a climate cycle, the result of interactions between the ocean and the atmosphere, that alters weather patterns, often leading to more precipitation and driving stronger storms.

The winter cold ‘peak’

Winter cold typically peaks before mid-February, but the coldest temperatures of the entire winter can occur just about until early March. The chart below gives a clear picture that the chances of subfreezing temperatures below 10 degrees go way down after February.

In fact, we’re in the middle of a warming trend at the moment. This week alone temperatures will gradually climb into the 50s, just in time for the weekend.

Then there is, of course, the sun and its growing angle across the landscape. Solar spring, the time when we gain over four hours of daylight between roughly Feb. 5 and May 5, is here. Each passing day we gain well over two minutes of daylight, and the strength of those UV rays is steadily increasing.

‘Strong’ jet stream offsets any chance of major snow

All of those things are averages, but here in New England averages are made up of extremes. Let’s look at the reality of what might occur in the coming weeks.

The ultimate configuration of the jet stream is paramount to what type of weather we experience. If the jet stream continues to be strong from the Pacific and doesn’t allow cold air to come down into the United States, snowstorms will be more difficult to occur in this part of the country.

The loop below shows the jet stream into the middle of the month. Notice that a band of strong winds continues to move in off the Pacific Ocean. This Pacific jet stream has been bringing a lot of mild air into the country.

In order for a snowstorm to develop, you need a combination of moisture from either the Pacific or the Gulf of Mexico combined with some cold air from Canada. Those types of scenarios give us our biggest snowstorms. The particular jet stream that is forecast is not conducive to generating any kind of hefty storm.

A weakening El Niño?

El Niño has been in the background since the fall and is weakening. And as forecasts note, as El Niño continues to wane, this can allow a new pattern to take hold and increase the possibility of snow and cold.

Winters with strong to very strong El Niño patterns tend to have most of their snow on the back end of winter. We’ll see if that holds true this year.

The oscillation factors

Another player in the rest of winter will be the Arctic Oscillation, the back-and-forth shifting of atmospheric pressure between the Arctic and the mid-latitudes of the North Pacific and North Atlantic.

When the Arctic Oscillation is strongly positive, most of the cold Arctic air stays locked up to the north. If the Arctic Oscillation enters the negative phase, Arctic air tends to spill farther south into the Northern Hemisphere. This doesn’t mean the flow of air is going to end up in New England. It could dip over into Europe or Asia.

So far, the long-range forecast has the Arctic Oscillation becoming negative later this month. This is at least one factor that would help bring us colder and perhaps stormy weather.

Another strong influence on winter weather is the North Atlantic Oscillation or NAO. When this is negative, it’s more favorable for snow here in New England. While oscillations can flip into phases more conducive to snow and cold, it isn’t a foregone conclusion. These phases just increase the probability.

Polar vortex revisited

One of the weather models also shows the polar vortex forecast to move from its typical spot over the North Pole to Scandinavia and stretch out from Siberia to New England.

According to Judah Cohen of Verisk Atmospheric and Environmental Research (AER) in Lexington, this type of configuration often, but not always, brings cooler air to New England. This forecast is quite complicated but something certainly to watch for around Valentine’s Day.

Warming winters

Finally, we can’t ignore the fact that winters are warming in general. Of the four seasons, winter is the fastest warming.

The warming is also accelerating. A hundred years ago, the atmosphere was colder. As we continue to warm, those late season storms which may have been snow decades earlier now can end up as rain — as we’ve seen so far this winter. Season-to-season weather is not climate, but climate plays a role and can’t be ignored.

For those of you who love the winter cold and snow, there is still time to see plenty of either, but the window is beginning to close as we nudge ever so close to spring.