My favorite weather site to see if its going to be ok is wunderground and for the island, I search Gilford not Alton.
There is a useful part on there that shows wind forecast throughout the day (see below) that we use to decide what times to come and go. WNW looks to make the worst waves on the broads side of Rattlesnake (Not a weather man, just need to give the family the smoothest ride possible).
Here is the link to the Gilford weather,
http://www.wunderground.com/US/NH/Gilford.html