Nor'Easter to Deliver a Cold, Windswept Rain Thursday for New England

A large upper-level low pressure system will begin to approach New England late in the day today. This system will spawn a surface low off the Mid-Atlantic coast tonight. This surface low will then slowly move northeastward across New England's coastal waters through Friday. The result is a late-season nor'easter producing a washout, gusty winds and possibly some mountain snow on Thursday and Friday.

Today will be very similar to yesterday, though likely a notch cooler. Scattered showers associated with the storm will likely hold off until at least the evening across the region. Showers will likely gradually fill in from southwest to northeast through the overnight hours into Thursday morning. By mid-morning Thursday, widespread showers will likely be ongoing across southern and central New England. It will take longer for precipitation to reach northernmost New England and all of Maine due to drier air and high pressure.

Below: HRRR showing potential weather overnight tonight (1st image) and mid-morning Thursday (2nd image):

For southern and central New England, the bulk of the storm will be Thursday afternoon and evening. This steady shield of rain will continue to lift northeastward through Thursday evening and night. Maine will see their heaviest rain Thursday night into Friday morning. With a blocked-up pattern in place, the system will be very slow to exit, with scattered showers continuing to cycle into New England through at least Saturday.

Below: HRRR showing potential weather Thursday late afternoon (1st image) and very early Friday morning (2nd image):

Southern and central New England will likely end up seeing a widespread 1-3 inches of rain. Rain amounts will gradually taper off moving northward in New England as a ridge of high pressure north of the region will delay the storm's arrival. Across the northern tier, a quarter to three quarters of an inch is more likely. In the end, exactly how much rain falls will come down to the system's track. While guidance has come into better agreement on a track very close to Cape Cod, there does remain some variation among ensemble members.

Being a nor'easter, gusty winds are also likely with this system. At this point, wind gusts don't look to be overly high, but 40mph+ gusts will be possible for the coastal plain. Should the storm track closer to land and achieve better mixing, gusts of around 50mph will be possible, mainly for eastern Massachusetts. Winds of this strength with the trees now fully leafed would cause higher impacts than a similar storm with bare trees in the winter. Winds will dwindle moving away from the coastline.

With a strong northeasterly flow, thick clouds and steady rain, afternoon highs will struggle to rise very much at all from morning lows, which will be pretty chilly as is, given the time of year. Many areas will likely struggle quite a bit to reach into the 50s. Daily record cold high temperatures for May 22nd are in the mid 40s to low 50s region-wide. Some of these records are likely to fall. Wednesday night and Thursday night lows will be well below average as well.

While this will be a cold, windswept rain for much of New England, some of the region's highest peaks could see some snow. Snow levels may be able to drop well below 3,000 feet above sea level Thursday, possibly to as low as 1,500 feet for a time. Accumulating snow should still be limited to the highest mountain summits of Vermont and New Hampshire. Wednesday night and Thursday night will continue to be very chilly as well. The record latest observed snowfall for mountainous counties in New England are all in late May or June.

This system involves a primary low moving inland through New England with a secondary low forming off the Mid-Atlantic coast and moving northeast over New England's coast. The secondary low will strengthen as the primary low transfers energy to the coastal low. This is a very winter-like storm setup and would result in a widespread snowstorm if this was a few months ago.

The driving easterly wind will create the possibility of some minor coastal flooding as well, mainly across eastern facing shores of Massachusetts. While astronomical tides aren't particularly high, they are high enough where a strong easterly wind could create pockets of minor flooding issues. It wouldn't be surprising to see a coastal flood statement or advisory issued later today for eastern Massachusetts (as well as a wind advisory).

The main storm system will lift into the Canadian Maritimes by Friday morning, ending the widespread rain chances from west to east. With that said, the upper-level low which spawned this system will be much slower to depart. This will keep scattered showers in the picture, very gradually decreasing in coverage through the weekend.