Execute Permissions for a Store Procedure that creates databases

I have a Stored Procedure that creates a Database for a specific project which needs to run every month by one of our Data Analysts. The question is how do I structure this to enable the Analyst to run this Stored Procedure without granting them Create Database Permission. I Tried WITH EXECUTE AS OWNER/USER_NAME The Analysts still get the below error: Msg 262, Level 14, State 1, Line 67 CREATE DATABASE permission denied in database 'master'. Any advice?