A severe thunderstorm watch was issued for portions of Northern New England as an extreme thunderstorm warning threat built this afternoon and evening. The northern tier of Vermont, New Hampshire, and Maine faced a rare enhanced severe storm threat, with storms expected to weaken shortly after midnight.
The storms could produce heavy rain, hurricane-force winds, medium-sized hail, and damaging gusts of 60 mph or stronger. An embedded supercell or two could also spin up an isolated tornado, so the watch covered more than one hazard at once.
Vermont, New Hampshire, Maine
The setup began this morning when a mesoscale convective system tracked along the top of a ridge of high pressure down through Northern New England from Quebec. That earlier round of thunderstorms and showers may have taken some of the energy needed for the afternoon and evening storms, and cloud cover from the morning activity could have limited heating.
A potent cold front sliding in from Canada was lifting hot, humid air upward to form storms. The greatest instability in the atmosphere was likely to arrive after maximum heating this afternoon, which is why the threat focused on the later part of the day.
Massachusetts and Greater Boston
The thunderstorms were expected to peter out before reaching Massachusetts and Greater Boston. The Bay State and Greater Boston were not expected to be threatened into the night, which left the main watch area centered farther north.
Wildfire smoke could act like a bigger lid on the pot and keep the sun’s heating from reaching the surface, adding another brake on the storms’ strength. If that cap holds, the strongest storms should stay more scattered than the rare enhanced threat initially suggested for the northern tier.
Shortly After Midnight
Storms were expected to begin to weaken shortly after midnight. Until then, residents in the watched area faced the main period for strong wind, hail, heavy rain, and the chance of a tornado.
