Rescue teams are battling fierce blizzard conditions to save six skiers trapped after a major avalanche struck the Sierra Nevada mountains in northern California. The Nevada County sheriff’s office confirmed nine other skiers from the group remain missing. The avalanche happened near Castle Peak by Frog Lake, northwest of Lake Tahoe. "It’s going to be a slow, tedious process because they also have to be very careful accessing the area due to the fact that the avalanche danger is still very high," said Captain Russell Greene from the sheriff’s office. The group had 15 skiers, including ski guides and clients. The six survivors have made a temporary shelter with a tarp and are communicating with officials via emergency beacons, which allow text messaging. "They are doing the best they can," Captain Greene said. Heavy snow and strong winds are expected to continue in the area. The National Weather Service warned that parts of the mountains could get up to 8 feet of snow with winds reaching 55 mph in the next 48 hours. Several nearby ski resorts have closed due to the extreme weather and avalanche threats.