The climate of this appellation is unique, partly because its elevation frees it from the fog which blankets the valley below in the afternoon. Also, since it faces west, the region benefits from extended, direct afternoon sunlight. The soils are volcanic and porous, contributing greatly to radiant cooling. The temperature can drop as much as 30°F in the afternoon, allowing grapes to maintain good acidity. Zinfandel is emerging as the best varietal for the appellation’s growing conditions. However, Chardonnay, Cabernet Sauvignon and Sangiovese are also planted here. Located on the western slope of the Vaca Mountains, northeast of the city of Napa, this AVA has over 1,500 acres of vines in a region of 11,000 acres. Grapes have been grown within the region for well over 100 years.