A ground and air search is underway to find a missing senior with dementia who disappeared without a trace from Cypress Provincial Park.

Debbie Blair was out hiking with a seniors group Thursday but somehow became separated from her hiking companions.

She was last seen around the Donut Rock Trial junction.

Mike Danks of North Shore Rescue describes the terrain in the area as "very challenging."

The 65-year-old is an experienced hiker, but she was only wearing a t-shirt and not prepared for last night's chilly weather. She is also hard of hearing.

Blair left her jacket and some food behind in the parking lot.

While it was sunny when she went missing, the temperature overnight hovered not far above freezing.

Ground crews will be out today searching for Blair on trails, while North Shore Rescue members are using heat-seeking FLIR technology on board helicopters to see if they can find any sign of her by air.

A sniffer dog from the Abbotsford Police was brought in to assist in the search.

Anyone who believes they may have seen Blair is asked to contact West Vancouver Police at 604-925-7300.