Petaluma Gap AVA

The distinguishing features of the Petaluma Gap are its topography and climate that sets the appellation uniquely from Sonoma Coast AVA. The 'Gap' literally describes the geological valley that is a 15 miles (24 km) wide by 30 miles (48 km) corridor between the coastal hills allowing the salty maritime winds and a cycle of morning fog, clearing sunny spells, more fog in the afternoon and clearer evenings to flow eastward through the region. A typical day in the valley can experience a temperature change of 40 to 50 °F (22–28 °C). These cycles contribute to a longer growing season benefiting cool-climate grape varieties. The lower elevations and rolling hills in Petaluma Gap allows the marine air to enter at a higher velocity than the surrounding regions where higher and steeper slopes disrupt the air flow. Although marine breezes are present during most of the day, the wind increases significantly in the afternoon hours because the rising inland hot air pulls the cooler, heavier marine layer from the coast causing a steady airflow. The effect of these prolonged high winds on the grapes is a reduction in photosynthesis to the extent that the grapes have to remain on the vine longer (hang time) in order to reach a given sugar level, compared to the same grape varietal grown in a less windy locations. Grapes grown in windy regions are typically smaller and have thicker skins than the same varietal grown elsewhere. According to the AVA's petition, the smaller grape size, thicker skins, and longer hang time concentrate the flavor compounds in the fruit, allowing grapes that are harvested at lower sugar levels to still have the typical flavor characteristics of the grape varietal. Also with the wind, there is no botrytis or mildew issues and the grapes have a higher skin-to-juice ratio.^[7] The USDA plant hardiness zones range from 9a to 10a.^[8]

The TTB modified the boundary of the North Coast AVA as described in Notice No. 163 because it determined the expansion area had the similar marine-influenced climate of the North Coast AVA. Therefore, the North Coast was expanded approximately 28,077 acres (44 sq mi) to include all of the Petaluma Gap and a partial overlap with the Sonoma Coast AVA. The Marin County portion of the Petaluma Gap remained outside of the Sonoma Coast AVA, while the Sonoma County portion remained within the Sonoma Coast AVA. TTB allowed the partial overlap to remain, primarily because the name "Sonoma Coast" is associated only with the coastal region of Sonoma County and does not extend into Marin County.^[1]

• Petaluma Gap Winegrowers Alliance
• TTB AVA Map

38°13′08″N 122°40′59″W / 38.2188587°N 122.682929°W / 38.2188587; -122.682929