Eight people are dead, one is still missing, after a backcountry ski tour group got caught in an avalanche near Castle Peak, California.A group of 15 skiers, four guides and eleven clients, got caught in an avalanche Tuesday as a severe winter storm blew through the mountainous area of Northern California.The Sierra Nevada Avalanche Center released a forecast that read, "Large avalanches are expected to occur Tuesday, Tuesday night, and into at least early Wednesday morning across backcountry terrain."The group was on the last day of a three-day tour in which they skied through "rugged mountainous terrain" while carrying food and supplies.The avalanche that swept up the group was recorded as a D2.5 on a scale of D1 to D5. An avalanche of D2 and above can bury and kill people, according to avalanche.org. .It was initially reported that six people of the 15 missing had been saved, but an update from Nevada County Sheriff Shannan Moon has revealed that eight people have perished in this avalanche, with one more still missing.Of the 15 people caught in the avalanche, just four have seemed to make it out unscathed, with two of the six rescued having been sent to the hospital after their rescue..A spokesperson for the sheriff's office told local media earlier that the rescue would be a "slow, tedious process" due to the risk posed to rescue personnel working in the unstable terrain in the aftermath of an avalanche.He also commented that although it was not uncommon for tour companies to take out groups in extreme weather such as this, he added that he thought that taking the group out in those conditions was not "a wise choice."Comments on social media echoed this sentiment, with commenters saying things like, "What in God’s name were they doing up there today of all days! Hope they survive and learn a really important lesson,” and, "Praying for all but questions about how ‘guides’ took them out in these conditions. Really? Did they not read the warnings?”In addition to this, Kurt Gensheimer, a man who was in the area when the avalanche happened, was interviewed by the New York Post and said that the incident should have been avoided."I was at Frog Lake from Thursday to Sunday but we got out before the storm moved in," Gensheimer said, adding that the situation is, "absolutely a preventable tragedy.".A nearby ski resort had reported that 76 cm of snow had fallen in the last 24 hours, resulting in the resort, as well as nearby highways, closing down.High winds and extremely low visibility were also reported.The deaths of these eight people make this one of the most deadly avalanche disasters in American history and the most deadly since the 1981 Mt. Rainier incident, where 11 people died.