Uncommon May nor’easter to bring rain, snow to New England states just before Memorial Day weekend

SCARBOROUGH, Maine — An unusual May nor’easter is set to wallop New England on Thursday, providing a soaking before the Memorial Day holiday weekend with weather more commonly associated with fall and winter.

Nor’easters usually arrive in the end of fall and winter and bring high winds, rough seas and precipitation in the form of rain or snow. This week’s nor’easter could bring wind gusts over 40 mph and up to two inches of rain in some areas. Snow is even possible at high elevations.

The storm has New Englanders preparing for a messy couple of days during a time of year usually reserved for sunshine and cookouts.

What is a nor’easter?

A nor’easter is an East Coast storm that is so named because winds over the coastal area are typically from the northeast, according to the National Weather Service. The storms are able to happen at any time of the year, but they are at their most frequent and strongest between September and April, according to the service.

The storms have caused billions of dollars in damage in the past. They usually reach the height of their strength in New England and eastern Canada. The storms often disrupt traffic and power grids and can cause severe damage to homes and businesses.

“We have a stronger jet stream, which is helping intensify a low pressure system that just happens to be coming up the coast. And so that’s how it got the nor’easter name,” said Kyle Pederson, meteorologist at the National Weather Service in Boston.

Who will see rain and snow

The heaviest rain is likely to fall in Rhode Island and southern and eastern Massachusetts, Pederson said. Localized, nuisance flooding and difficult driving conditions are possible on Thursday, and catastrophic flooding is not expected.

The storm is expected to pass, leaving light rain and patchy drizzle, on Friday, Pederson said.

“It’s just really a nice dose of rain for the region — not expecting much for flooding,” he said.

Snow is expected to be confined to mountainous areas, but accumulations there are possible.

Why nor’easters are rare in May

Nor’easters are usually a winter weather event, and it is unusual to see them in May. Nor’easters typically form when there are large differences in temperature from west to east during winter when there is cold air over land and the oceans are relatively warm.

But right now there is a traffic jam in the atmosphere because of an area of high pressure in the Canadian Arctic that is allowing unusually cold air to funnel down over the Northeast. The low pressure system off the East Coast is being fueled by a jet stream that is unusually south at the moment.

“It really is a kind of a winter-type setup that you rarely see this late,” said Judah Cohen, seasonal forecast director at the private firm Atmospheric and Environmental Research.

He said if this type of pattern in the atmosphere happened two months earlier “we’d be talking about a crippling snowstorm in the northeastern U.S., not just a wet start to Memorial Day weekend.”

O’Malley and Whittle write for the Associated Press. O’Malley reported from Philadelphia.