Saturday is trail-race day on Lookout Mountain.

A couple of hours after the fourth annual Lookout Mountain 50-miler starts on Covenant College property on top of the mountain, the 27th Wauhatchie Trail Race starts at the foot at the Chattanooga Nature Center.

Registration is closed for the 50-miler and accompanying 10-kilometer race in the Rock/Creek Trail Series event, with about 250 in each option, but Wauhatchie runners can sign up even Saturday morning, beginning at 8:30.

"We'll probably have about 120, maybe 150," Wauhatchie race director Jim Steffes said Wednesday. "A lot of people like to wait until race day to see what the weather's going to do, but we're going to have great temperatures and I think the rain is going to be cleared out."

The 6.7-mile out-and-back course on the lower slopes of the mountain uses gravel and dirt roads as well as single-track trails.

"The first and last mile are flat, but the miles in between are up and down," Steffes said.

It's a "no-frills" race with awards only for the overall winner and the top two-person family team, he noted, so it costs just $10. The postrace meal is a collection of what people bring, with hot cider, coffee and soft drinks also available, and participants are encouraged to bring old T-shirts and running awards for a "grab-bag table" for others to pick from, if desired.

The race's main distinguishing characteristic, though, is its staggered starts to give entrants of both genders and all ages a chance to win the top prize. Any 80-over females will begin at 9:30; the last group, males 25-29, will start at 10:10.

Tim Ensign won the Wauhatchie race for the sixth time last year and is ready to try for a seventh after finishing 47th in the national 10k masters cross country race last Saturday in Seattle. But at 49 he expects a strong challenge from 70-year-old Sergio Bianchini, who moved up an age group and added to his head start after being the last person Ensign passed in the 2010 race.

"Sergio will get like a 12:45 head start, and I think Tim's is five and a half," Steffes said. "And if [former University of Tennessee at Chattanooga star] Lanni Marchant shows up, she'll challenge Tim, too, because she gets a minute and a half on him and finished only 20 seconds behind him in the Joe Johnson 10k a couple of months ago."

Ensign noted that he has had "a lot of close races" in his wins and losses in the Wauhatchie.

"Whoever came up with the head-start times really knew what they were doing," he said. "This is the original trail run around here, and it's a lot of fun."

Troy Shellhamer of Louisville, Ky., won the Lookout Mountain 50-miler last year in 7 hours, 42 minutes, 23 minutes, and area runner Sarah Woerner was the top female in 8:51:49.

This year's entrants include runners from as far away as Florida in one direction, Vermont and Maine to the northeast, Michigan to the north and Kansas and Texas to the west.