Another day, another severe thunderstorm watch that goes until 10pm for towns and cities north and west of Boston. At one point, the National Weather Service issued a tornado warning in Rockingham County for rotation on the radar near Exeter and Portsmouth N.H. No confirmed tornado has been reported as of 6:30PM. The issue across northern Mass were storms that produce frequent cloud to ground lightning, torrential rains, strong wind gusts and hail. The best instability this evening takes a break for a few hours, but late evening and overnight, we'll have to watch all the storms that are in Upstate New York, move east. We'll likely be dry for the fireworks in Boston, but by midnight, may have a shower/storm chance back close to the city and a bit earlier than that outside 495.
Arthur Update: As of 5pm, the National Hurricane Center had winds sustained in Arthur of 90mph and just south of the Outer Banks of North Carolina. The track of Arthur will move the hurricane to the northeast, off the Outer Banks, and about 75-100 miles south of Nantucket Friday night. While that position keeps the strongest winds offshore, winds may get a bit feisty across the Cape and Islands from 11pm - 2am (Friday night -Saturday morning). We expect active northerly winds to develop, gusting to 30-40mph, with locally higher gusts near Chatham and Nantucket. A tropical storm warning is in effect for the Cape and Islands for wind gusts of 39+mph. The winds aren't prolonged or strong enough for major coastal flooding issues, but those that have marine interests, keep advised the seas will build and the surf rough.
For most of us, this is just a rain issue as a cold front across the area has enhanced downpours thanks to tropical moisture along it. Showers start scattered Friday morning, and increase in coverage through the midday and afternoon hours. The Cape and Islands don't see much rain until after 2PM. In terms of rainfall amounts, most towns along coastal New England will pick up between 2-3" of rain with locations farther inland between .50"-1.00". Given how dry June was for us, rivers & streams will welcome the big gulp of water. Some localized street flooding is likely across SE MA & the Cape tomorrow evening.
By Saturday, the cool front is offshore and Arthur is #Gotye. That means sunshine, low humidity & a healthy northerly breeze for the day. Sunday offers more sunshine. Temps both days in the low to mid 80s. Watch for rip currents and rough surf at the beach through the weekend.
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