By Jan. 6, with umbrellas and snow shovels getting a workout, the statewide Sierra Nevada snowpack was a respectable 93% of its historical average. On Thursday, the Sierra snowpack had fallen to just 59% of its historical average. “And I don’t see anything of any significance in the forecast for the next week.”That means the Sierra snowpack number will continue to fall in the coming days. The big storms, which Tahoe-area ski operators have dubbed “the Christmas miracle” because they saved ski season, also sent reservoir levels rising fast. It’s only the fourth inning,” said John Rice, president of Ski California, an industry association.