(PD) - Having celebrated 30 years as an official American Viticultural Area (AVA) last year, the Russian River Valley can say that many of its visionaries' dreams have come true. The region is now world-renowned for producing gorgeous pinot noir and chardonnay, among other wines.

With time and experience under their belts, today winemakers and growers are better able to determine the many nuances that differentiate the Russian River Valley's northern end from its south, its cool western edges from its warmer east, its benches and ridges from lower and higher elevations.

Those nuances are key to understanding how the region's starring grape, pinot noir, can take on perceptible differences in the glass. The aromas and flavors are both very much determined by the variations in climate — basically, how much fog creeps in — and soil.

At a new event in May called the Russian River Valley Pinot Classic, winemakers got together to talk about these differences, unofficially splitting the appellation into what they are calling “neighborhoods.”

For discussion's sake, the neighborhoods were broken firmly into three, from warmer north to cooler south: the Middle Reach, Laguna Ridge and Green Valley. The Santa Rosa Plain and Sebastopol Hills as two more neighborhoods are under consideration.

The reason to subdivide is because the AVA itself is so big. When it was first approved in 1983, the Russian River Valley comprised 96,400 acres. An expansion in 2005 bumped it to 126,600 acres; another boundary re-draw in 2011 added new areas to the south and east, near Rohnert Park and Cotati, an increase of 9 percent.

The appellation now encompasses 169,029 total acres, 16,000 of them planted to wine grapes. (For the sake of comparison, the entire Napa Valley is about 225,000 acres).