I'm using XCskies which requires a $39.95 yearly subscription. I believe it's similar to XCsoar as Mark described. You have the GFS, NAM and RUC forecasts. XCskies lets you do point and route forcasts which I find helpful. They show you likely places where it may not be fruitful to venture. However, as Mark said, they are just tools and you have to use a lot of judgement when using them.
The XCskies forcast my show good lift on your planned route but when you get into the route, there's a large blue hole ahead. Readjustng the plan is par for the course.