Well, there's good news and bad news, whatever happens. If the first snow hasn't hit by then (or is minor enough to have melted off), then all the trails from Yosemite Valley will be open, but Yosemite will be at about its worst (no waterfalls, no snow, probably too late for fall color). Alternatively, if the snows have started, then the snow will make Yosemite Valley very pretty, but fewer of the trails will be accessible. In late November, it's hard to tell which will be the case - that's about when the weather changes from autumn to winter conditions, but it varies quite a bit from year to year, so it's hard to tell at this point. Yosemite Valley is still a gorgeous place, even at its worst, though, so don't let worries about that put you off. Just also come back sometime later in the winter to photograph snow on trees, or sometime in late spring to photograph waterfalls on cliffs!
In any event, I think it's extremely likely that the high country roads (Tioga Pass, Glacier Point, etc.) will be closed by Thanksgiving, but the Valley is the most spectacular part anyway. Even if there are heavy snows by then, there will still be photogenic parts of the valley which are accessible.