Winter is off to a promising start for California water managers. A handful of storms in late fall and over the holidays primed the state’s mountains with a solid base of snow, with such high-elevation spots as the Truckee River basin, the Mammoth Lakes area and Lassen Volcanic National Park reporting five or more feet of snow on the ground. On Thursday, as state water managers trudged through powdery fields to conduct the first snow survey of the season, the cumulative snowpack across the Sierra, southern Cascades and Trinity mountains measured 108% of average for the date. Snowpack was greatest, by far, in the north with some areas in the south missing out on the early winter weather.