A tornado was observed in southern New Hampshire Thursday afternoon, the National Weather Service said, and while the warning for that incident expired, more were possible before the end of the day as a line of storms was hitting New England.
Severe thunderstorm warnings and flash flood warnings were in effect across much of New England Thursday afternoon and evening, but they have since expired.
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The tornado warning had been issued in Cheshire and Hillsborough counties. The National Weather Service said it would be surveying the area of Keene and Dublin, New Hampshire, on Friday to confirm the reports of a tornado.
What’s been a near chart topping July for rain will get even wetter on Thursday as thunderstorms move through. Boston is running a surplus of nearly 5 inches of rain more than normal. The grounds are saturated and rivers are swollen.
Tuesday already showed us how quickly and efficiently the atmosphere is at producing rain and flooding, and Thursday is no different. While the excessive heat will energize the atmosphere, there are some limiting factors to the evening’s rain and storm threat as well.
U.S. & World
What could break Thursday's storms... or make them
As with any severe weather event, there are different conditions, or triggers, in the atmosphere that must be met. Moisture and heat are what we’ll watch. Those conditions are limiting factors that overall may break the severe weather threat. But when they are maximized, they can create damaging storms.
As of Thursday midday, we already have the moisture parameter increasing. Dew points throughout southern New England are in the mid-70s, to even upper 70s. This will increase the instability, along with daytime heating this afternoon. Temperatures will likely continue to rise near 90 degrees. At 1:30 p.m., Norwood was at 89 degrees. Much of Boston and Metrowest also sits in the upper 80s. Clouds are clearing out and a lot of fresh and untapped energy remains.
As we get into the warmer sector of air, and convection ongoing across the Hudson Valley in New York, the main source for lift is entering New England. This is a sure sign that severe weather is approaching the region.
A severe thunderstorm watch is in effect until 8 p.m. for virtually all of southern New England, except for the Cape and Islands.
The movement of the storm will be more linear, stretching from northeast to southwest. Thursday’s primary threats will include damaging winds until 9 p.m., and even 1-1.5 inch hail. Flooding shouldn’t be overlooked either. In fact, with recent rain, it perhaps may be the banner concern. Rainfall rates, at times, will near 1 inches per hour through the Merrimack Valley and North Shore, along with Leominster and Fitchburg. The inundating rain will create blinding rain at times around 5-7 p.m. through the evening drive.
Tornadoes can't be ruled out in Mass.
With shear present, weak and brief tornadoes are a threat Thursday. The likely culprits for brief spin-up tornadoes are along and slightly ahead of the main line of storms. While that threat is near equal for everyone, midday guidance is honing in on areas between Worcester and north central Norfolk County near Norwood, Westwood and Dedham, and through Quincy from 5-8 p.m. And a similar time for northern Middlesex County to the North Shore.
Though it isn’t an overarching concern, a low to moderate threat exists.
How can you prepare?
If you’re still reading this and heavy rain hasn’t started, it’s worth ensuring that loose tree-limbs are trimmed and patio furniture is secured. In the strongest downpours, gusty winds will prevail with winds between 60 and 70 mph.
Power could go out, and dependent on restoration time, some of the time without power could be spent without A/C, and with hot temperatures. So having a secondary area to go, like a cooling center, will be important, along with staying hydrated and having extra water on hand.
This is a tricky forecast. Given how potent and aggressive storms have been this season, you should remain weather aware. Download the NBC10 Boston app. You can sign up for weather alerts and get push notifications before the dangerous storms strike.
