These things happen very often and there could be many explanations. Every time the President moves one is declared. There is a permanent one at Beale AFB, CA.

These things happen very often and there could be many explanations. Every time the President moves one is declared. There is a permanent one at Beale AFB, CA. And there are permanent ones at Disneyland and Disney World. Any aviation mapping source and many weather apps with aviation data (MyRadar is my choice) shows these come and go.