After a month of huge blizzards and “atmospheric river” storms, the Sierra Nevada snowpack — source of a third of California’s drinking water — is 177 percent of the historic average, the biggest in more than two decades. The last time there was this much snow on Feb. 1 in the Sierra was in 1995. Pete Wilson was California’s governor, “Seinfeld” was the top-rated show on television and Steve Young had just led the 49ers to a blowout win in Super Bowl XXIX.