Although we did not do a lot of touring in Napa, we did stop at Mumm winery where they make some lovely sparkling wines, They were harvesting 3 weeks early due to the heat and drought. We were allowed to taste the grapes in the demonstration plot, which were essentially all juice and seeds and were wonderfully sweet, having been allowed to ripen longer than the ones they harvest for wines. Here is the link to their website if you want to check it out.
Everyday Cheer 