I need to do a long run today to get ready for a race. I had lake accotink (3x around) in mind or burke lake/mercer lake but wondered if they are too puddly/muddy. my usual runs are in the neighborhood on cement sidewalks but I wanted to give my knees a break and run on paths. if they are too muddy, any other suggestions?

If you're near I66 & Nutley, Marshall Rd elementary school has a well drained gravel track. The gravel is fine so it offers a stable packed surface that absorbs shock.

Likewise, good recommendation above, Fairfax HS's track is good after rainy conditions, and it also has the similar shock absorbing material, that we didn't have back in the day. Plus, well marked as well, and close parking if you go behind it on Rebel Run.