A large-scale rescue operation is underway in California's Sierra Nevada mountains after an avalanche swept away a group of skiers at Castle Peak on Tuesday. The incident occurred during a severe storm that has brought heavy snowfall to the region since Sunday. A group of 16 skiers, including four guides, were backcountry skiing when the avalanche struck. Authorities have confirmed that at least six skiers survived and remain at the site awaiting rescue, while ten others are still missing. The rescue effort involves 46 first responders, but conditions remain extremely dangerous due to ongoing severe weather, with an avalanche warning in effect until Wednesday evening.