This article states investigators have narrowed to 1-4am time frame. Neighbor of Savannah Guthrie's Missing Mom Nancy Details Crime Scene (Excl)
IMO a time period when activity drops, less witnesses and unusual movements stands out. This is probably the time of the suspect (s) movements they are prioritizing and hoping neighborhood cameras picked up something, someone saw something, etc. I think it’s likely, sadly, she was already gone. IMO