The Shenandoah Valley sits between two mountain ranges, the Blue Ridge Mountains and the Allegheny Mountains.
Tucked in a valley, it does not have close proximity to urban centers as its neighboring wine regions (Middleburg AVA has Washington, D.C., and Monticello AVA has Charlottesville). What the Shenandoah Valley has is the town of Winchester to the north, which is the apple capital of the country, and the small town of Staunton to the south, a charming place.
In addition, the Shenandoah Valley is located at a higher elevation and gets less rain compared to the east side of the Blue Ridge Mountains and other wine areas in Virginia. It is a statistically drier and cooler area, and perhaps it is the most ideal place to be making wine in Virginia.