Vigorous storm may produce snow, trigger severe weather in California next week

AccuWeather meteorologists say a storm will dip southward along the Pacific coast of the United States later this weekend to early next week. And while this storm may have limited moisture, it will likely cause travel disruptions as it spreads snow and triggers gusty thunderstorms, especially in Southern California.

Pacific storms have been tracking inland over the West Coast but mainly to the north of California over the past 10 days or so. Meteorologists sometimes refer to storms that track across the region in this manner as "inside sliders." Most of the impacts of these storms in California have been sparse precipitation and bouts of gusty winds.

Prior to the inside slider storms, multiple atmospheric rivers from late December through the first half of January drenched California and hacked away at the state's long-term drought at the cost of deadly flooding and mudslides. Reservoir levels have risen dramatically since the early autumn, and the Sierra Nevada snowpack is at its deepest level in years for this point of the season.

"A shift in the jet stream pattern over the northeastern Pacific will allow the caboose in the slider storm train to push farther south than predecessors and across California as a result," AccuWeather Lead Long-Range Meteorologist Paul Pastelok said. This is likely to be the last such storm for a few weeks, but it will have significant impacts.


Despite a lack of tropical moisture, intense jet stream energy associated with the strengthening storm as it drops southward will lead to some dramatic weather conditions across the Golden State.

"There will be very little precipitation in San Francisco and much of the Sacramento Valley, but there can be some strong northeasterly wind gusts from late Sunday into Monday," Pastelok said. "Any steady precipitation is likely to be confined to the Coast Ranges and Sierra Nevada and will be much less intense compared to most storms from the first part of January."

Sporadic showers and mountain snow showers with gusty winds will first reach Northern California Saturday night and spread southeastward on Sunday and Monday over the Southwest.

"In Southern California, the atmosphere will turn quite unstable and will allow gusty winds, showers and thunderstorms to erupt on Monday and Tuesday," Pastelok said. "The atmosphere could go wild over Southern California."

This is the type of setup that can trigger locally severe thunderstorms, packing strong wind gusts, brief intense downpours and hail in the Los Angeles, San Diego and Palm Springs, California, areas. While tornadoes are rare in California in January and February, a couple of tornadoes or waterspouts cannot be ruled out near the coast early next week.

Because a sharp dip in the jet stream will accompany the storm, much colder air will sweep in. Temperatures will average about 5-10 degrees below normal in Northern California but close to 20 degrees below normal in Southern California from Sunday to Monday. Typical highs around the end of January and the start of February range from the upper 50s in Redding, San Francisco and Sacramento to the upper 60s in Los Angeles and San Diego and the lower 70s in Palm Springs.

Snow levels will plummet with the burst of cold air, forecasters say.

"Only limited moisture will prevent a heavy accumulation of snow over the mountains in California and the interior Southwest states, including the Colorado basin," Pastelok said. "However, snow levels may dip below 3,000 feet, which is below the passes along interstates 15 and 5 in Southern California."

At this level, some of the hills surrounding Los Angeles and San Diego could experience some snowflakes.

As the snow showers develop, visibility could decrease in a hurry, and a quick accumulation can make for treacherous travel from later Sunday night through Monday night over the Grapevine. Accidents and road closures will be possible.

Farther north, along I-80 at Donner Pass and Truckee, California, up to a few inches of snow will fall from late Saturday night to Sunday evening. Slippery conditions cannot be ruled out over the higher terrain along I-5 in Northern California as well from Saturday night to Sunday.

AccuWeather's long-range forecasting team expects Pacific storms with more moisture to return during the first half of February.

"Storms with ample rain and mountain snow will return to California, especially the northern half of the state and the northern and central Sierra Nevada early in February," Pastelok said, adding that the pattern could persist for several weeks.

"One of the storms could be strong during that stretch but not close to the intensity of the group of storms that occurred in early January," Pastelok said.

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