GW2 The Gathering Storm achievement can be completed in Wayfarer Foothills and Diessa Plateau.
Wayfarer Foothills Events
Use Dolyak Pass Waypoint in Wayfarer Foothills and complete event Recapture the homestead from invaders, or use Solitude Waypoint and complete event Destroy the Flame legion portal and drive out invaders.
Diessa Plateau Events
Use Butcher’s Block Waypoint and complete event Recapture the ranch from invaders.