Mt Washington Observatory is the best resource, in my opinion, since they have a forecast specifically for the higher summits and deal directly with mountain, as opposed to valley, weather, as well as always providing a discussion of the weather as well.
Obs website
They also post a forecast on a recording with telephone number every morning, and that's what I use closer: 1 (603) 356-2137, Press 1
The other resource I use is good old NOAA weather radio. My car receives it, as do my FRS radios. It's not as specific to the mountains but they do report the current conditions on Mt Washington which is an indicator of just how bad it can be.