The latest evidence that snow angels have smiled on the Sierra this season? Mammoth Mountain will stay open into August. The massive resort has remained running that late only one time before, in 1995. The announcement follows Squaw Valley’s news that it may stay open right into the fall. Over Memorial Day, visitors reported that Mammoth’s parking lots were packed but lift lines were open and the slopes uncrowded. Guests said Broadway and Stump Alley were running with hardly any lines. Conditions were especially fine for boarders, who power through the slush better than skiers.