NORTHSTAR AT TAHOE (CBS SF) — A California Highway Patrol helicopter equipped with a high-tech detection device began crisscrossing the skies over the Northstar ski resort Thursday morning, hoping to pick up a signal from an avalanche safety beacon that missing Truckee skier Rory Angelotta may have been carrying with him.

The Placer County sheriff said Angelotta was an experienced skier and was believed to have avalanche equipment on his person when he disappeared amid blizzard conditions on Saturday.

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So far four days of searching in challenging weather conditions have failed to uncover any sign of Angelotta.

Tracks found in the deep snow in a remote mountain area had raised hopes Tuesday, but then they were determined to have been made by a bear.

The last in a series of fierce winter storms finally began moving eastward early Thursday. Since Dec. 21, officials said, 135 inches — more than 11 feet — of snow has fallen at Northstar.

According to the sheriff’s office, friends of Angelotta reported him missing when he failed to show up for Christmas dinner Saturday evening after a day of skiing. Authorities said his car was found in the resort parking lot and his calls went straight to voicemail.

Missing Truckee skier Rory Angelotta (Placer County Sheriff’s Office)

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The sheriff’s social media accounts posted on Tuesday that the Nevada Air National Guard was using a Blackhawk helicopter equipped with forward-looking infrared capabilities to help searchers in the current extreme weather conditions.

The sheriff’s office said other resources deployed to assist in the search included Tahoe Nordic Search and Rescue, Placer County Search and Rescue, Nevada County Search and Rescue, Butte County Search and Rescue, Bay Area Mountain Rescue, Tahoe Backcountry Ski Patrol, and Northstar California Ski Patrol.

The social media posts showed video and images of the search efforts.

The search for 43-year-old Truckee resident has been hampered throughout by harsh weather conditions that have dumped more than 4 feet of new snow. Angelotta was last seen Saturday morning at the Northstar ski resort.

The investigation has revealed that around 11:30 a.m., Angelotta’s ski pass was scanned at the Comstock lift. There was no other activity registered to his pass since that time.

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“Searchers responded and combed the mountain and surrounding areas, despite extreme weather,” the Placer County Sheriff’s Department said. “Rescue personnel were on skis, snowmobiles, and a snowcat during their search. They faced high avalanche danger, strong winds, whiteout flurries, frigid temperatures, and heavy snow loads.”