They were trying to do this hour without live updates to avoid staying even later, it seems, but they wound up breaking in with a radar update at 12:20 CT to update on yet another powerful tornado on the ground.
If things calm down as they sometimes do late at night, why don't they just make sure at least record one good (non-time sensitive) version of every segment between the two hours and play that one set of good segments twice during the rebroadcast time period? That way the broadcast will rebroadcast smoothly, and Rich and Sharon can get home on time.
Of course, if severe weather is still relevant during the rebroadcast timeslot, they should still go live.