After years of severe drought in California, historic rain and snow has pummeled the state this winter. This has helped to ease some of the concerns from years of rainfall deficits. The precipitation this year has been a bit surprising given that La Nina conditions are once again present. La Nina is the presence of colder than normal water temperatures at the equator off the coast of South America in the Pacific Ocean. These conditions have been present for the past few winters and typically will push the jet stream well north of California. This results in less storms and drier than normal conditions. However, the opposite has happened this winter.
After a relatively normal wet period from early October through mid-December, the pattern changed drastically by the end of December. The jet stream sagged south and brought significant rain and snow to portions of California through the middle of January. This was aided by the presence of an Atmospheric River. This “River” is a long narrow region of air from the tropics that transports an unusually large amount of water vapor and strong winds.
The first in a series of six major storms fueled by this Atmospheric River arrived just after Christmas 2022. Additional powerful storms followed every few days through the middle of January 2023. As a result, rainfall totals of up to 45 inches occurred during this 3 week period for parts of California. Some areas received upwards of 70% of their normal rainfall totals for the entire year over a 3 week period. This rain helped move all areas of the state out of exceptional and extreme drought conditions, but also resulted in devastating floods and mudslides for many locations.
In addition, significant snow fell in the higher elevations in California. Most notably, Mammoth Mountain received nearly 20 feet of snow during this time. With additional recent storms in late February and early March, has already surpassed 550 inches for the season. Mammoth Mountain will have a chance to break their snowfall record of nearly 670 inches. This record occurred during the 2010-2011 season (records go back to 1969). Snow is beneficial for a number of reasons. It is helpful to ski resorts in the short term, but it also will help to replenish water tables throughout the spring as the snow slowly melts and absorbs into the ground. The threat for storms to hit the west coast is expected to continue into the spring.