Could be the drift in the lowest 1000ft since it’s bending south on each side of the radar site. Near the surface you have ground reality and as you get further out it’ll be more to the north of ground truth.
I need a better cam with streaming, but if you view the last 20 images and loop them it gives you an idea. http://www.newenglandwx.com/northfield-nh/2-backyard-cam-previous-20.htm