As relentless sunshine continued to pound California on Thursday, the Sierra Nevada hit a reckoning point: There’s less snowpack now than on the same date three years ago, when the winter went down as the driest in recorded history and sent shudders through cities, farmlands and the state Capitol. The troubling lack of snow during the winter of 2014-15 not only shortchanged the state’s drinking-water reservoirs but left the Sierra nearly unrecognizable.