Much of Grand Teton National Park is closed in winter, so finding easy access points for snowshoeing can be a little difficult, and you might need to get creative. The small parking lot on the south side of the Lake Jackson Dam allows you an easy place to access an un-groomed snowshoe route along the north side of the Snake River. You simply need to descend the stairs, which will likely be covered in several feet of snow. The handrails will probably still be sticking out, and they provide a sense of where the staircase is located and assist the relatively easy descent.
Once you are down the stairs you'll have an open stretch of stunning white snow along the Snake River as the mist rises off of the water's surface. This is a great walk for viewing winter wildlife: look for trumpeter swan and moose, among other species. The terrain is flat, so the route is pretty easy apart from the tricky descent down the stairs. There are some tributaries that must be crossed; they might be completely frozen, or they can be prone to breaking. Use your poles to test the strength of these crossings or bring a pair of waders so that you are not stopped by the conditions. Even though the bears will be hibernating, it is not a bad idea to bring some bear spray in case you encounter an aggressive moose or a rare appearance by wolves.
Within a mile or so you will be running out of hikeable terrain, so turn around when you feel comfortable. There is no trail, and people rarely snowshoe here, so hopefully the wildlife won't be spooked off by the crowds. It's a great place to snowshoe, and there is no avalanche danger anywhere along the hike.
Winter backcountry adventures can be dangerous outdoor activities that pose significant risks as conditions affecting safety (i.e. weather, snowpack stability, avalanche hazard) are constantly changing. Prior to engaging in these activities each individual should get the proper training to make safe decisions and be equipped to use avalanche safety resources and tools. Please visit our Backcountry Skiing and Avalanche Safety post to learn more.