Each Map has its "Valid" time.
If there are no maps visible, it means that a new run has started, but not yet produced output. Maps from the previous run are available at the main High Resolution Site. All other available images are linked from this page at UW
4 AM or 4PM
7AM pr 7PM
10AM pr 10PM
1AM pr 1PM
4AM or 4PM
7AM or 7PM