From CAP 413:
Military Safety Broadcast – Securité
10.78 Military ground stations may commence a broadcast message with
‘SECURITÉ SECURITÉ SECURITÉ’ (SEC-URI-TAY spoken three times)
to inform all traffic that the message contains information affecting
safety, but not an emergency situation. Aircraft acknowledgement is
not required, however aircraft may contact the ground station to obtain
further details.
I would say that the OP's scenario fits the bill here, but would a civil pilot/ATCO be familiar with the proword SECURITÉ?