There will be snow this weekend but not a blockbuster storm

Boston, MA -- 3/14/2017 - A pedestrian crosses Merrimac Street in Boston.  (Jessica Rinaldi/Globe Staff)

Topic: 15storm
Reporter:
A pedestrian crosses Merrimac Street in Boston on Tuesday. –Jessica Rinaldi / The Boston Globe

Blue skies, light winds, and melting temperatures Friday afternoon gave us the feeling that spring might actually be close at hand. And while this is true, we have another storm to watch out for this weekend.

On Thursday, I wrote that the storm won’t be big. I still believe this to be the case, but it’s another very close call.

There will be snow, so prepare yourself for a psychological hit, but not a blockbuster storm. Unlike Tuesday’s storm when the issue was rain vs. snow, this weekend’s forecasting challenge is just how close the storm will come and how organized it will be.

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via GIPHY

A new storm is diving south out of Canada and heading to New England. Credit: NOAA

What meteorologists are sure of is that a low pressure system will dive out out Canada, head for the coast, and, upon reaching the waters of the Atlantic, become more intense. While this is occurring, something else will be happening at about 18,000 feet into the atmosphere.

The gif below shows atmospheric energy traveling south from the Great Lakes, creating a loop of winds in the atmosphere. As the storm is captured by this loop, it will be forced to travel within it doing a loop of its own. This scenario slows down storms. Think of how far you would drive if you were stuck in a rotary for a day. It’s sort of the same thing, but the rotary itself is traveling east.

via GIPHY

Credit: Tropical Tidbits

The challenge is the exact position of the storm over the weekend and its precipitation shield. Areas like Cape Cod and the Islands, southeastern Massachusetts, and Cape Ann will be closest to the storm, so they’ll have the potential for the greatest precipitation.

Another issue is the time of day the storm occurs. This time of year, even with thick clouds, enough ultraviolet light reaches the surface of the Earth to warm it up. Roads, dark cars, and other non-white surfaces will be warm enough for any snow to have trouble sticking. Any accumulation forecast needs to be tempered by what sticks on the road versus the existing snow.

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Snow will break out across the area in the early morning hours of Sunday and then continue much of the day. The intensity of the snow determines how much sticks, but plan on a few inches with more than that south of Boston. The storm will wind down Sunday evening with cloudy skies early Monday before clearing moves in later in the day.

As of Friday, it appears snow is likely for much of the area Sunday. —David Epstein

There is the potential this turns into a bigger storm. Whenever you have this type of a scenario, a westward jog of the low pressure area would bring the heavier precipitation inland. New model data Saturday may change this forecast, either increasing or decreasing the snowfall, so check back for changes.

One final aspect of the storm will be the wind. There is a high wind watch for Cape Cod and the Islands. Winds could be gusting over 45 mph Sunday into early Monday with the closest pass of the storm to the coastline. Add in some heavy wet snow and there is the potential for power outages.

You can follow David Epstein on Twitter @growingwisdom.