Looks like there's a bug in the site and the app.
It looks to me (unless there's another explanation) like when you scroll time, the map data "presented" and the time "presented" that the data relates to are sometimes not updated atomically.
Within seconds of scrolling back and forth through the hours you can get completely different map data presentation for exactly the same hour, usually looks like the same as the hour just ahead or behind the one you just reached the current hour from in the scroll.
I realize the data itself is an estimate/forecast but this is different, so at key points of significant weather change this leaves you in significant doubt over which map hour data to use.
Any thoughts?