sentences:  The cool evening temperatures help to preserve the natural acidity of the grapes over an extended growing season.Although many varietals are grown, the Petaluma Gap is best known for its Pinot Noir, Chardonnay, and Syrah grapes.In 2006, twenty-four local organizations and individuals formed a promotional group called the Petaluma Gap Grape and Wine Alliance, now known as the Petaluma Gap Winegrowers Alliance.