DAVIS, W.Va. --

More than 100 volunteers came out to the Dolly Sods Wilderness area to help search for an autistic hiker who has been missing since Sunday afternoon.

Command Center spokesman Chris Stadelman says the large number of volunteers will allow today's efforts to be in the form of a grid search, where the searchers line up in sight of the next person in line.

Any volunteers planning to help today are asked to gather at the Canaan Valley ski area.

Jacob Allen, 18, of Morgantown was hiking with his parents Sunday when he got ahead of them and didn't answer when they called his name.

While Jacob is described as severely autistic, he is in good physical shape and likes to hike. The family visits the Monongahela National Forest a couple of times a year.

Search crews are focusing on a primary area of 10 square miles of often rugged and brush-covered terrain.

Allen was wearing a long-sleeved T-shirt, a wind jacket, wind pants and hiking boots in the forest, where temperatures dropped to about 38 degrees Sunday night and to about 40 last night. He had no food or water with him.