Wahluke Slope is an AVA within the larger Columbia Valley wine region of Washington State. The wines made in this warm, dry part of the Pacific Northwest are predominately red, with Merlot as the front runner, producing concentrated, heat-ripened wines. There are also substantial plantings of Cabernet Sauvignon and Syrah.
Wahluke Slope is clearly defined geographically, and consists of a sloping, south-facing plateau situated in a bend of the Columbia River. The AVA covers a triangle of land measuring about 15 miles (25km) from east to west, bordered by the Saddle Mountains in the north (which separate it from the brand-new Ancient Lakes of Columbia Valley AVA). The Columbia River makes up the southern and western borders, and the Hanford Reach National Monument borders the appellation to the east.
The vineyards of Wahluke Slope sit on an alluvial fan. Like much of the Pacific Northwest, the terrain here was created by the Missoula floods of the last Ice Age, some 15,000 years ago. These floods, caused by waters from the then-sizable Lake Missoula in Montana breaking through the glaciers that held them in place, saw huge amounts of water wash through eastern Washington before flooding the Willamette Valley in Oregon.
The soils in Wahluke Slope are made up of sediments deposited by these floods and of windblown material from the flood-eroded material of the surrounding landscapes. Gravel and rocks are covered by a thin layer of sand and silt, providing a low-fertility, well-drained site for grape growing. The vines here are put under stress by the harshness of the dry soils, and as a result produce small, concentrated grapes in lieu of leafy foliage.
The soils are joined by the effects of the desert-like climate of Wahluke Slope. Like most of Columbia Valley, the AVA lies in the rain shadow of the Cascade mountain range, and Wahluke Slope is one of the warmest wine regions of Washington, along with Red Mountain. The south-facing aspect of the slope means that vines benefit from day-long sunshine, maximizing ripening, and the lack of rain means that growers have control over vigor and berry production through the careful use of irrigation.
Wahluke Slope is one of Washington's high-production areas, and the vineyards in the AVA are owned by producers from all over the state. While premium, single-AVA Wahluke Slope wines exist, a large proportion of the wines made here are blended into regional Columbia Valley blends, usually providing intensity of flavor and big structure to the wines.