When you say the web map has evolved, I wanted to check if the web map has just been updated, or do you want to switch to a different web map. The Story Map apps automatically show the web map as-is, so the latest changes will be reflected on the map you see in the story. To switch to a different web map, in the Story Map Series builder, go the tab or section you want to edit, click Edit, then in the Edit dialog that appears click the Map dropdown list and choose the Select a Map options.
Rupert
