Resources were diverted from the search for missing Victorian man Michael Bowman, who failed to return to the visitor centre on Saturday, to search for the trio.

The adult and child were arrested in relation to a white Toyota Hilux that was stolen from Westerway on Sunday night or Monday morning.

Emergency services continue to search the Lake Pedder area for the third missing person - another child, with police holding grave concerns for the child's wellbeing due to the weather conditions.

The Westpac Rescue Helicopter is being used to sweep the Cradle Mountain-Lake St Clair National Park and the Walls of Jerusalem today, with walkers given the option to be evacuated.

Weather conditions are expected to worsen over coming days, with two cold fronts, rain, wind and snow predicted in the Central Plateau.