Lenticular clouds, also known as standing wave clouds, are really common in mountainous terrain. They are typically associated with high upper level winds. There was probably a cold front (southwest wind) approaching that day. The mountains push the air up, also known as orographic lifting. The moisture in the rising and cooling air condenses and that type of cloud forms. If you were to watch it, you would see that it is building on the windward side (west or soutwest) and dissapearing (entraining) on the leeward (east or southeast) side as the air descends and warms. Usually, when lenticulars (upper level winds) are seen, the next day will be very windy with surface winds. When a winter cold front comes through, it is not at all uncommon for the Sierra Nevada to have gusts over 100 mph on the highest ridges. The associated wind slab snow has been described as "variable" by ski area marketing. How was the next day? I'll have to read on now. Rippin' effort on the ride report, thanks for sharing.