The forecast for thunderstorms with damaging winds is below. Fifteen percent is the significant threshold for both wind gusts and hail. Forty-five percent is very high!
And, the forecast of hail one inch in diameter or larger:
In the hatched area, the hailstones may exceed two inches in diameter.
Radar at 12:45pm EDT shows the derecho is now completely over the Atlantic. Thunderstorms will cause problems for Providence and Boston air travelers this afternoon.
The most important feature is the lines of thunderstorms developing from West Virginia to Tennessee. These will intensify this afternoon with the likelihood of damaging winds and some hail. Remember, wind-driven hail can cause a great deal of damage.