"Increases in snowpack of this size are not common, but also not unprecedented," Julie Kalansky, deputy director of operations for the Center for Western Weather and Water Extremes (CW3E), explained. Kalansky pointed out previous studies have shown a jump on this scale can happen about twice every three years, but usually over the course of an entire winter, not just the month of December. While they don't have the exact rankings for each month of the year, "most of the storm events in the study we referenced for the above calculation were in the second half of December and later into the season," Kalansky added.
The sudden change gives California its wettest start to the Water Year in more than 40 years, thanks to several drought-denting rain and snow systems pushing through the area in recent weeks. The Water Year runs from October 1 through September 30 of the following year. Parts of California are known for whiplash weather, but the rapid changes are quite remarkable given the snowpack was off to such a rough start, after a very warm and dry November for much of the state.