From Fairfax County Park Authority:
Although winter weather is often associated with traffic delays, sore backs, and broken shovels, many adults are just as eager as their children for the season's first snow to fall. Some people even argue that winter is the best time of year to visit Fairfax County parks. With crowds thinned like trees which have lost their leaves, visitors can savor the solitude found in quiet forests and meadows. There are numerous ways to enjoy the "off-season" in the parks. Here are a few:
Click into cross-country skis or snap on snowshoes and explore some of the 300 plus miles of trail maintained by the Park Authority. Take a birding guidebook along to identify the birds you see.
Wax up a sled and shoot down your favorite hill. (To protect fairways and greens, Fairfax County Park Authority golf courses prohibit sledding.)