Since the 2015 SSA Convention, I've been using top Meteo integrated with SeeYou for planning these flights. Today was the largest deviation I've seen between the forecast and reality, and that mostly boiled down to a slightly later start and an earlier finish than forecast. The in-between 8 hrs or so of soaring was pretty much as forecast.

The 7 day prog chart on aviationweather.gov is very handy too for identifying upcoming good days.