A Robust El Niño Pattern is Set to Ramp Up the Moisture Across California

Posted: December 14, 2023 12:36 pm

While it has been largely dry throughout most of California in recent weeks, that is all about to come to an end heading into the holidays. This is typically the time of the year when the moisture train gets going in the Pacific Ocean and moves into California. The normal wet season has yet to materialize in the Golden State but forecasters are warning that this is about to change. Here is what you need to know about the forecast for California in the coming week and how El Niño is influencing the weather predictions.

Moisture Projected to Become More Widespread Across California in Coming Weeks

Forecasters are anticipating that the rain and snow is about to pick up in intensity and frequency across California. Unlike last year when the region saw an exceptionally wet November, the moisture has been conspicuously absent this season. Last November brought a major storm that dumped 1 – 2 inches of rain in the major cities of Los Angeles and San Francisco. It got even wetter in December with 9.66 inches of rain falling in San Francisco and Los Angeles picking up 2.81 inches.

Although the wet season is not likely to get off to a hot start like it did in 2022, forecasters are predicting that the rain and snow is on the way. The wet weather will get started this weekend when a weak disturbance brings rain to the lower elevations and snow into the higher terrains of Northern and Central California.

A more robust storm system is forecast to bring moisture in from the Pacific starting next week, signaling a harbinger of things to come into the Christmas holiday and beyond. The majority of the moisture will fall across the coastal areas of the Pacific Northwest, however, some of this rain will sneak into California. It is not out of the question that rain will push into coastal Southern California early next week.

Temperatures that support snow development will dip lower across the Cascades Mountains and into the northern Sierra Nevada. This will likely impact travel over some of the region’s busiest mountain passes.

Influence of El Niño on Weather in California

As is typical during a strong El Niño phase, the West Coast is bracing for a wetter than average winter. This climate phase is marked by warmer waters in the eastern subtropical Pacific Ocean. As of November, temperatures in this area of the Pacific basin were measuring about 3 degrees Fahrenheit over the average for the month, pointing to a powerful El Niño phase in place.

This warm zone of water produces a contrast zone that triggers a more active southern jet stream, intensifying the storm track over California. This subtropical branch coming off the jet stream has already led to heavy rain across the southeastern U.S. This persistent rain is forecast to continue through the weekend in this region. And now it is California’s turn to get in on the moisture machine that results from El Niño.

Up until now, an area of cooler sea surface temperatures located north of the tropical Pacific have kept the bulk of the moisture out of California this season. This zone of cool water has already been forcing the storm track to the south, taking the activity away from California and into the Gulf of Mexico.

Conversely, if this area of cooler waters starts to warm up, it will move the subtropical jet stream over Southern California. This position will then begin to carry the hallmarks of a stronger El Niño pattern with more rain in this part of the West Coast.

Heading into next week, the rain will pick up gradually across the Golden State. This differs from some of the more typical atmospheric rivers that impact the region this time of the year. However, do not rule out more intense periods of rain or snow that seem to come out of nowhere as the calendar inches deeper into December and into the beginning of next year. This is how El Niño will flex its muscles and make a bigger impact.

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