Deadline reports that Michelle Harrison has been cast as Nora Allen, Barry Allen’s mother. We learned in Barry’s Arrow appearances that the show picks up on the post-Rebirth* and New 52 history, in which she was killed during his childhood, and his father was falsely accused and imprisoned for the murder. (In fact, the show hinted that, as in the comics, the Reverse Flash is her real killer.) So we’ll be seeing her in flashbacks.
The pilot for The Flash starts shooting early next month.
*In the original Silver Age and Bronze Age comics, Nora and Henry Allen were still alive throughout Barry Allen’s superhero career. Flash: Rebirth involved the Reverse-Flash changing history.