mjw - my alternate route is mapped out here. As of this morning, all of the paths from the Pentagon along Washington Blvd across Columbia Island over to the Memorial Bridge were completely clear of snow, with the exception of one little 10-15 spot that had been navigated by a MTB judging by the tire tracks. I run slick city-type tires on my bike, so I walked it, but it's all clear otherwise. The ride through Crystal City is the closest thing to "high traffic" with the exception of crossing Four Mile Run on US1. But it is a very bike friendly route.

If you're coming from around Del Ray it's a straight shot. If you're coming from Old Town, I imagine you may need to hop over to Mt Vernon Ave and come through Del Ray to avoid 1 as much as possible. It's a good route though. Today's ride was about 40 minutes including traffic lights to go the 7.25 miles. My regular commute on MVT, fewer lights and a quarter-mile shorter is usually ~30 minutes total. A tad slower, but a he11 of a lot better than being stuck in metro!

PM me if you have any questions.