California ushered in the New Year with a dry and disappointing snow pack in the Sierra Nevada — just 25% of the historical average. But in the month since, like the stock market and the 49ers playoff hopes, the picture has improved significantly. On Monday the snowpack, a vast 400-mile long frozen reservoir that provides nearly one-third of the state’s water supply, had jumped to 52% of normal, boosted by several big storms that have taken ski resorts out of the doldrums in recent weeks and tempered talk of a 2024 “snow drought” that was beginning to take hold. “We’ve come a long way from whe…