In my opinion, the target of Ansarallah's ballistic missile attack on Riyadh was most likely the King Salman Air Force Base, just south of Riyadh.
If the target was Prince Sultan Air Base, there would likely be no early warning for Riyadh, as it is located 80 km from the city. Early Warning Flash: Normally not activated for Riyadh when Prince Sultan Air Base was attacked by Iran earlier this year.