Royal Slope AVA

Royal Slope is an American Viticultural Area (AVA) located within Adams and Grant Counties in central Washington state. Royal Slope is the state's 15th appellation recognized by the Alcohol and Tobacco Tax and Trade Bureau (TTB), Treasury on October 2, 2020, after reviewing the petition submitted by Alan Busacca, a licensed geologist and founder of Vinitas Vineyard Consultants, LLC, on behalf of the Royal Slope Wine Grower's Association, proposing the viticultural area named “Royal Slope.” The AVA lies between the Quincy Basin and Saddle Mountains surrounding the town of Royal City encompassing 156389 acre entirely within the vast Columbia Valley AVA. There are currently 13 producing commercial vineyards cultivating approximately 14100 acre with only one winery. According to the petition, the distinguishing features of the Royal Slope AVA are its climate, topography, geology, and soils.

History
According to local lore, the name originated when two Scotsmen climbed the Saddle Mountains in the 1880s and observed the view to the north of the south-sloped topography and exclaimed, “Now that’s a Royal Slope!” Historically, the name “Royal Slope” is printed on USGS topographic maps of various scales since the 1950s to mark the general area. The name has been in common usage for more than 50 years to describe the rich agricultural district of tree fruit orchards, row and field crops and since the 1980s, viticulture.

Topography
The topography of the Royal Slope AVA is characterized by the gentle, south-facing slopes of an east–west trending 30 mi range of hills called the Frenchman Hills. Slope angles are generally less than 15 percent, with very few slopes having angles of less than 3 percent. The slopes are gentle enough for agricultural purposes and are not as freeze-prone as flatter terrains such as valley floors. To the north of the AVA, the Frenchman Hills fall away to the Quincy Basin, which is a large, flat-floored valley. To the northeast are sand dunes and "pothole" ponds between the dune crests. To the east and south of the AVA is the Crab Creek Coulee gouged out by Missoula Floods, and on the west, the bedrock cliffs fall away steeply to the Columbia River, which has lower elevations and steeper, rockier terrain than the AVA. About 90% of Royal Slope's area consists of gently to somewhat steeply south-facing slopes. These southern slopes represent the best aspect for wine grapes in the Pacific Northwest due to the northerly latitude.

Climate
The climate of the Royal Slope AVA is described as warm but not excessively hot, making it a suitable climate for growing a variety of red and white grape varietals, including Cabernet Franc, Merlot, Syrah, Chardonnay, and Riesling. The AVA generally has greater growing degree day (In the Winkler climate classification system, annual heat accumulation during the growing season, measured in annual growing degree days (GDDs), defines climatic regions. One GDD accumulates for each degree Fahrenheit that a day's mean temperature is above 50 F, the minimum temperature required for grapevine growth.) accumulations and an average cool-climate viticulture sustainability index (The cool-climate viticulture sustainability index represents the number of days between the last temperature below 29 F in the spring and the first temperature below 29 F in the fall) number than all of the surrounding regions except the regions to the south and north. The AVA also has a lower risk of vine-damaging freezes, as it generally has fewer days per year with temperatures below 32 F than all of the surrounding regions except the region to the south. Finally, the AVA has an average of only 9 days a year with temperatures above 95 F, which is fewer than the region to the south, and has fewer very hot days per year than the regions to the north, east, and west. Grape vines shut down photosynthesis at temperatures above 95 F, which can slow or even stop the synthesis of sugars and other ripening factors and may delay harvest.

Soil
The Royal Slope AVA, like the rest of the Columbia Valley AVA, is underlain with Miocene-era basaltic bedrock and has been affected by Ice Age megafloods. Within the region of the AVA, the floodwaters followed flood channels to the east and northeast. The waters entered the region in a relatively smooth fashion, and the AVA remained largely above the floodwaters. As a result, the AVA was not heavily eroded and remained a landscape of gentle hills with deep soils suitable for cultivation. By contrast, the regions to the east and south of the AVA were eroded by fast-moving floodwaters which cut deeply into the landscape and formed the scablands of Crab Creek Coulee. Similarly strong floodwaters flowed through the region to the west of the AVA, creating the steep canyon of the Columbia River. North of the AVA, the floodwaters were smoother and gentler and deposited vast amounts of sand in what is now the Quincy Basin, creating a landscape of dunes and ‘‘pothole’’ lakes. Within the AVA, the soils are a combination of sediments from glacial floods and wind-blown post-glacial sand and silt (loess). The soils are generally deep enough for vines to extend their roots far into the soil before encountering bedrock or other impediments. The predominant soils are Aridosols, which are characterized as well-drained and low in organic material. Major soil series include Warden, Sagemoore, Adkins, and Kennewick, which together comprise approximately 59 percent of the soil in the AVA. By contrast, the regions to the east, west, and immediate south of the AVA are scablands, which have very little, if any, topsoil. Farther south of the AVA, within the established Wahluke Slope AVA, the soils are deep and fertile but are primarily Entisols, including the Quincy soil series, which comprise less than two percent of the soils in the AVA. The region to the north of the AVA is also primarily composed of Entisols, including the Quincy soil series.

Industry
Royal Slope AVA has the potential, situated between Wenatchee and Tri Cities and about two and half hours from Seattle, to become a popular destination within the state's growing enotourism industry. The region gained industry recognition when a Charles Smith 2006 Royal City Syrah was rated 100 points by Wine Enthusiast as the first vintage in the state to rank that high.