Afternoon rain and wintry mix will change to snow overnight in Massachusetts – The Boston Globe

A rainy day Sunday afternoon will become a snowy evening in Greater Boston, with wet snow expected overnight until around daybreak Monday morning.

That will likely affect the Monday morning commute in Greater Boston, especially for those coming from west of the city, according to the National Weather Service.

Though Boston is slated to get less than an inch of total snowfall, higher-terrain portions of the state, including the Berkshires and the hilly parts of Worcester, could see 4 to 6 inches of snow, with some local snowfalls in western Massachusetts approaching 8 inches, according to Matthew Belk, a forecaster with the weather service.

He said the shift to snow in that part of the state was “already taking place” before 11 a.m. Sunday.

Boston will see “predominantly rain” Sunday, with bouts of a wintry mix, before switching to snow when temperatures drop overnight, Belk said.

“The farther west you are, the more MetroWest, you could see a couple inches of snow,” Belk said. “As you get toward the city itself, like the Seaport District, it’s probably less than an inch.”

By 11:30 a.m., snow had begun to fall in parts of Cambridge and Allston, though it appeared to melt upon hitting the wet pavement.

Though temperatures in Boston are not forecast to dip below freezing until Monday evening, windchills in the mid- to low-20s are expected after 6 p.m., according to the weather service.

In Worcester, temperatures will fall below freezing around 3 a.m. Monday, according to the weather service, and windchills will stay below 30 degrees from noon Sunday onward.

By sunrise Monday, though, there will be only a slight chance of snow still falling west of Worcester, Belk said.

“Then that focus is going to shift down towards southeast Massachusetts as we get into Monday afternoon, where we’ll have a northeast wind, and there’s a possibility of some ocean-effect snow,” Belk said. “And that would be where southeast Massachusetts, the Cape and the islands, maybe get their little bit of snow.”

Ocean-effect snow, Belk said, is when cold air forms over relatively warm ocean water, creating wind with enough lift and moisture to generate bands of snowfall. “It generates kind of its own little microclimate,” Belk said.

That eastern snowfall is unlikely to stick, Belk said, as temperatures in the high 30s and into the 40s are forecast on the Cape starting early Monday.

“If the ground’s wet, it’s generally not going to accumulate much,” Belk said. “The snow will melt as soon as it hits the liquid water on the ground.”

To the west, the Sunday night snow will likely stick around until Wednesday or Thursday, Belk said, when temperatures rise above 40 degrees.

Belk said Sunday’s snowfall will generally be wet and heavy, which may make shoveling arduous.

“Sledding snow? Maybe not as much,” Belk said. “I’m not a skier, but [it will be] maybe not as good for those activities.”

Daniel Kool can be reached at daniel.kool@globe.com. Follow him @dekool01.