Regional Available - Relicanth
The Pokemon World Championships are happening today, August 16th to August 18th, 2019 at the Walter E. Washington Convention Center in Washington DC.
To celebrate the large gathering of Pokemon fans, players of Pokemon GO will be able to find Relicanth, the Water and Rock-type regional from New Zealand, at the convention center. Aerodactyl will also be available.
Aerodactyl can be found in "Catch 10 Pokemon" research tasks at PokeStops located in and around the event area. Relicanth can be found in "Send 2 Gifts" research tasks.
Relicanth has been made available outside of New Zealand before as part of the Safari Zone Porto Alegre event in South America.
PvP Side Event
It also appears there is a Pokemon GO PvP mini-event happening at the convention as well.
Pokemon fansite Serebii posted the above picture which alludes to an event happening around the convention center but details are sparse. Check back to this post for full details on this officially sanctioned PvP event.