Random tip:
Clicking the link button Permalink you get a map which does not time out relating to the chosen time step or run! (perfect to use in a discussion forum)
[Persistent time: target date of the map persists (!) but GFS data is refreshed]
[Persistent time+run: Target date and data persistent, map stays completely as it is]. You can obtain this option by selecting a certain GFS run (standard is "current maps")