A half-dozen law enforcement personnel huddled under the canopy of their search and rescue vehicle during a driving rain Monday as dozens more combed the rugged low mountains of Placer County in search of a missing Modesto trail runner.

The weather – occasionally including snow and freezing rain – hampered the search for Robert Root, 55, and heightened its urgency, said Lt. Kevin Borden, who is coordinating the effort.

“The wind and rain has made it that much more difficult,” said Borden.

The organized effort to find Root, an experienced trail runner, began at around 9 p.m. Sunday, almost 12 hours after he was last seen by his running group members, who were running the trail used for the annual Western States Endurance Run in June. Monday, the tiny community of Michigan Bluff, 12.5 miles east-southeast of Colfax, elevation 3,510 feet, was inundated with rescue and media vehicles.

Root went missing 15 miles into Sunday’s training run after he became separated from other runners. He was last seen about 9:30 a.m. Sunday, clad in running gear and unprepared for cold overnight temperatures in the mountainous region of Placer County. Snow was expected Monday evening in the Sierra foothills, according to the National Weather Service.

The Placer County Sheriff’s Department was notified of Root’s disappearance at around 3 p.m. Sunday, Borden said. Once a search team was assembled, professional rescuers searched through the night, lighting signal fires in hopes Root might be able to see the light and come to them. In the morning, the search grew to include 57 members with volunteers from Placer, El Dorado, Nevada and Sacramento counties. The effort involved horse teams, dogs, and people on all-terrain vehicles and on foot, Borden said. A helicopter also searched for a brief time Monday before being grounded by the weather.

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According to a post on the ShadowChase Running Club Facebook page, Root was running with some of its members. The group organized a 7:30 p.m. vigil at its running club in Modesto.

Monday afternoon, the club issued a statement about the search:

“The ShadowChase Running Club is anxiously awaiting the safe return of one of our beloved members. Robert “Bob” Root has been an avid trail runner for decades. A strong, experienced runner, Bob has logged countless miles on trails throughout Northern California,” the statement read.

Root, a well-known running enthusiast, was honored by the American Red Cross for helping another runner during the Modesto Midnight Half Marathon in 2010.

Root and Dr. Danielle Myers were running in the Modesto race when they came upon an unconscious runner about 40 minutes into the event. Myers found the man with a faint pulse, but then his breathing became labored and his heart stopped.

Root, who had been trained in CPR through his employer, the Modesto Irrigation District, helped Myers administer help until paramedics arrived. The man had regained consciousness by the time he was taken to the hospital.