Remnants of Debby move out of New England. Strong winds cause outages, some damage in Vermont. - The Boston Globe (2024)

Most of the heavy rain Friday was concentrated in central and northern Vermont, where nearly 3.5 inches fell in some spots. Rainfall totals ranged from 1 to 3 inches across much of Vermont, New Hampshire, and Western Mass. The most intense rainfall stayed to the west and targeted upstate New York.

Previous Debby coverage:

Power being restored across Vermont — 6:44 a.m.

Power has been restored to almost half of those utility customers in Vermont who lost power Friday due to post-tropical cyclone Debby’s strong wind gusts downing trees and power lines. About 26,000 homes and businesses still remained without power as of 6:45 a.m. Saturday, according to poweroutage.us. Outages peaked around 40,000 last night.

Most of the outages were in northern Vermont, including the hardest-hit area of Burlington. Winds gusted up to 62 miles per hour in parts of the state Friday afternoon and into the evening. Winds are expected to improve later today.

Thousands reported without power across Vermont — 12:15 a.m.

About 40,000 homes and businesses in Vermont were without power late Friday after gusty winds from Debby downed trees and power lines across the state, according to poweroutage.us.

Most of the outages were in northern Vermont, including the hardest-hit area of Burlington. Winds gusted up to 65 miles per hour in parts of the state Friday afternoon and into the evening. More calmer winds are forecast by Saturday afternoon.

Tornado watch expires — 10:10 p.m.

A tornado watch has expired for Western Mass., Vermont and Connecticut.

Tornado watch continues through 10 tonight in parts of Mass., VT and CT — 7 p.m.

A tornado watch remains in effect until 10 p.m. for Western Mass., much of Vermont and Connecticut. A tornado watch means that atmospheric conditions are favorable for developing thunderstorms to spawn a tornado.

When we talk about severe weather, particularly tornado watches or warnings, meteorologists will often touch on “helicity.” But what does that term mean?

Helicity is the measurement of how much low-level wind shear is likely present near the surface, which is a major component needed in order for tornadoes to form. Wind shear is the change of wind speed and direction as you move up into the atmosphere.

Helicity puts into context how much potential the lower levels of the atmosphere can cork-screw and twist — a portion of its calculation comes from comparing storm motion versus other wind motion in the atmosphere. Helicity values also take into account how freely air can move in the atmosphere, known as instability. The more freely air moves, the more instability is present.

In Mass., the tornado watch includes Berkshire, Franklin, Hampshire and Hampden counties; in Vermont, Addison, Bennington, Rutland, and Windham counties; and Hartford County in Connecticut.

If a tornado warning is issued, seek shelter right away. The safest place in your home is the interior part of a basem*nt. If there is no basem*nt, go to an inside room, without windows, on the lowest floor.

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Flash flood warning issued for southwest VT — 6:30 p.m.

A flash flood warning has been issued for Bennington County in the southwest corner of Vermont through 8:30 tonight. There is a pocket of heavy rain pushing into Vermont right now and anywhere from a half-inch to 1.5 inches are forecast within the next hour or so. That’s on top of the 1-3 inches that have already fallen across the area. Hilly terrain may lead to pooling water in valleys as well as flooding of small creeks, streams, and highways and roadways.

Debby’s strong wind gusts cause travel disruptions — 6:15 p.m.

Debby’s powerful winds caused numerous flight delays and cancellations at some of the busiest airports across the country on Friday, including at Logan International Airport.

More than 500 flights were delayed and about 200 were canceled at Logan as of 6 p.m., according to FlightAware. Logan, JFK, LaGuardia, O’Hare in Chicago, and Washington, D.C.’s Reagan airports led the country in delays and cancellations of flights within, into and out of the US, as of 6 p.m. Logan ranked fourth in the number of delays and cancellations.

At Logan, inbound flights were being delayed 2.5 hours while departure delays were around 40 minutes, according to FlightAware.

Debby has held a centralized core of low pressure that’s created a steep pressure gradient and caused strong wind gusts of 25 and 50 mph across the Northeast and Mid-Atlantic. The gusty winds are expected to continue through Saturday morning.

Flash flooding concerns remain up north as next round of rain moves in — 4:35 p.m.

With the heaviest rain still to come tonight, Vermont, New Hampshire, and Western Massachusetts will remain most vulnerable to flash flooding, with an estimated 1 to 3 inches of additional rain forecast for those areas.

The heaviest round of rain is expected between 6 p.m. and midnight. Another 1 to 3 inches may fall in those areas before Debby begins to pull away from New England and there may be a few instances of increased rainfall that can cause rivers to overflow.

The threshold for flash flooding across parts of northern Vermont and New Hampshire is low. The National Weather Service’s flash flood guidance shows an estimate of the amount of rainfall needed to cause flooding of streams and rivers over a certain period of time. With imminent widespread rain, the three-hour rain totals needed to reach flash flooding state ranges from an inch to 2 inches up north, which is possible given how moist the atmosphere is with steady to heavy rain on the way.

Vermont, N.H. seeing highest rainfall totals from Debby — 3:15 p.m.

Another round of rain is moving into Vermont with pockets of heavy downpours that could cause localized flooding in northern portions of the state. Parts of Vermont have already seen over 3 inches of rain since Thursday night.

Some rainfall totals as of 3 p.m.:

• Grande Isle, Vt. - 3.02 inches

• Johnson, Vt. - 2.40 inches

• Montpelier, Vt. - 2.03 inches

• St. Johnsbury, Vt. - 1.78 inches

• Colebrook, N.H. - 1.73 inches

• Burlington, Vt. - 1.64 inches

• Bennington, Vt. - 0.80 inches

A flood watch remains in effect through Saturday morning for northern Vermont.

Ken breaks down the latest developments on Debby — 2:45 p.m.

Globe lead meteorologist Ken Mahan gives us an update on the status of Debby this afternoon.

Tornado watch issued for Western New England through tonight — 1:35 p.m.

The National Weather Service has issued a tornado watch for Western Mass., much of Vermont and Connecticut through 10 p.m. tonight. The watch also extends to parts of New York, Pennsylvania, and New Jersey. A tornado watch means that atmospheric conditions are favorable for developing thunderstorms to possibly spawn a tornado. A tornado warning is when a tornado has been spotted, is radar-indicated or is all but certain to be on the ground. A warning means you must seek shelter right away.

In Mass., the tornado watch includes Berkshire, Franklin, Hampshire and Hampden counties; in Vermont, Addison, Bennington, Rutland, and Windham counties; and Hartford County in Connecticut.

Strong winds prompt high surf, rip current alerts through Sat. — 1:20 p.m.

Winds across New England are expected to ramp up as the afternoon progresses, with wind advisories across Western New England and high surf alerts issued for beaches along the coasts of southern Rhode Island and southeastern Massachusetts, including the Cape and islands. Beachgoers in those areas today may not see as much in terms of rain, but a strong southeasterly wind to 25 miles per hour with higher gusts will produce large breaking waves of 5 to 10 feet , which will make for strong rip currents. Dangerous swimming conditions will continue this afternoon through Saturday morning. This larger scale pattern of strong southerly wind is due in part to the remnants of Debby. The high surf advisory remains in effect through Saturday night.

Debby brings threat of tornadoes — 12:18 p.m.

As the cyclonic nature of Debby’s remnants move into New England, there is a slight chance for a tornado or two to spin up — possibly this afternoon and evening in Western Mass. and Connecticut as the core of the system gets closer to the region.

The combination of rising warm, moist air mixed with changing wind speeds and directions, especially with a weakening cyclone, help create tornadoes. Often surface wind speeds and direction change at different rates than higher in the atmosphere, creating a tornado inducing environment.

The specific risk area for New England stretches across Western New England and includes Springfield, Pittsfield, North Adams, and in Vermont: Bennington, Rutland and Burlington.

Flood warnings issued for northwest Vermont — 11:45 a.m.

Flood warnings have been issued just south of Burlington, Vt., and Lake Champlain region as reports of heavy rain and flooding have come in, including 3 to 4 inches of rain along Interstate 89 just north of Exit 16 in Colchester.

The warning is in effect until 3 p.m. for Addison, Chittenden, Franklin and Grand Isle counties in Vermont. Additional rainfall amounts of 1.5 to 2 inches are possible in the warned area. Rivers and streams are expected to rise, causing possible flooding in low-lying and poor drainage areas.

Parts of Vermont see over 2 inches of rain so far from Debby — 11 a.m.

A couple of rounds of rain fueled by moisture driven by remnants of Tropical Storm Debby pushed through portions of northern Vermont and New Hampshire overnight and into this morning. Already about 1 to 2 inches of rain have fallen across parts of Vermont with this initial wave, including within areas that have been hammered with previous flooding rains over the past month, including flooding from the remnants for Hurricane Beryl.

Another 1 to 3 inches can be expected through Friday night, with a few breaks in the rainfall mixed in. Some areas may see locally higher amounts to 4 or 5 inches.

Here are a few rainfall totals throughout New England through 11 a.m.:

• Johnson, Vt. - 2.38 inches

• Montpelier, Vt. - 1.81 inches

• St. Johnsbury, Vt. - 1.77 inches

• Colebrook, N.H. - 1.73 inches

• Burlington, Vt. - 1.61 inches

• Bennington, Vt. - 0.70 inches

• Manchester, N.H. - 0.53 inches

• Pittsfield, Mass. - 0.53 inches

Flood watches, wind advisories issued for parts of New England — 10:45 a.m.

• Flood watches are In effect for parts of Northern New England from noon, Friday until Saturday morning.

• Wind advisories have been issued for western Vermont and parts of southern Connecticut from Friday afternoon to early Saturday morning, with forecast wind gusts of up to 50 mph at times.

Storm timing for New England

Friday evening

Rounds of intense rain will continue through the night across much of central and western New England. Rain will become heavy at times, with the chance for localized flooding across parts of Vermont, New Hampshire, and Western Mass.

As heavy rains from Debby’s remnants approach New England, a strong southerly flow will develop and help bring in loads of moisture, which will build humidity levels throughout the day.

By Friday afternoon, dew points across much of the region, including Boston, will climb as high as the mid-70s — that’s a lot of water vapor — and it’ll feel like south Florida across New England.

Saturday

Morning

After bringing most of the heavy rain Friday night and into pre-dawn hours of Saturday, the system will quickly be swept away by the more dominant cold front shoveling the moisture into Nova Scotia. Rain should begin tapering off by sunrise with a handful of scattered showers lingering through late morning.

Five of the six New England states should be nearly completely dry by noon, with parts of eastern and northern Maine dealing with scattered showers from Debby into the afternoon.

Afternoon

Conditions should improve quickly with the passing of the front and a stark shift in the wind pattern. The moisture-rich southerly flow will switch over to a healthy westerly breeze and drop dew points throughout the day while bringing the sun back out in abundance by mid-afternoon.

Ken Mahan can be reached at ken.mahan@globe.com. Follow him on Instagram @kenmahantheweatherman. Marianne Mizera can be reached at marianne.mizera@globe.com. Follow her @MareMizera.