Overnight Parking at Shady Grove Metro (Washington DC)
 

I'll be visiting DC this weekend and was thinking I'd leave my car at the Shady Grove Metro Parking lot (Red Line, Maryland) instead of paying for expensive parking in town. I see the rates on the Metro site (free on weekends) but it doesn't say if overnight parking is or isn't allowed.
Does anyone know if there are any restrictions?

On weekends, you can park overnight