With no wet weather yet in sight this October, meteorological winter is just around the corner, officially beginning in less than two months Dec. 1. The season will have some meteorological twists and turns that may end with a surge of snow and blasts of bitterly cold air.
That’s what private forecast group AccuWeather is predicting this season – mild for most of the United States, similar to last winter, which was the warmest on record. However, that is only part of the story, as waves of frigid air will periodically send freezing air across the country, along with more chances for snow.
AccuWeather’s 2024-2025 U.S. winter forecast- just released – suggests California could see another wet winter punctuated by more atmospheric rivers. The forecast comes as California carryover of reservoir water is plentiful- about 120% of the 15-year average.
3 key factors in the winter forecast
One of the major elements considered by AccuWeather when crafting the winter forecast was La Niña. This phenomenon occurs when water temperatures near the equator in the eastern Pacific Ocean remain below the historical average for an extended period, which can significantly influence weather patterns across North America, including the trajectory of snowstorms.
“La Niña will be weak for most of the winter,” AccuWeather Senior Meteorologist and Long-Range Expert Paul Pastelok explained. “A weaker La Niña can allow other signals to drive the pattern, more variability throughout the winter.” A weak La Niña also makes it more likely that not just northern California will get wet this winter, but Central and Southern California as well.
Another player in the winter forecast is the polar vortex.
Based on data from previous winters with a similar setup to the upcoming season, Pastelok said that February is the most probable time frame for the polar vortex to usher a blast of bitterly cold air across the eastern U.S., but added that it is not a certainty.
A third factor is the temperature of the water in the Gulf of Mexico and the northern and northeastern Pacific. Water temperatures in the Gulf are expected to be higher than historical averages, which can translate to mild air masses for the central and eastern U.S. The warmer-than-average water temperatures in the northern Pacific could alter the storm track at times during the winter for the West Coast, impacting the entire U.S.
Wet Christmas in California?
It felt more like summer across part of the West as October kicked off with record-breaking temperatures, but Pastelok says the heat will soon fade and the wet season will shift into gear before the official arrival of winter.
The frequency of rain will gradually trend upward in November and December, along with snow in the mountains. “I think skiing in the West is looking really good,” Pastelok said. “I think it’s going to get kick-started right for the holiday season,” he added, saying Thanksgiving and Christmas look very good for skiers.
Atmospheric rivers and storms from the Pacific Ocean will focus on the Northwest and Northern California before traversing over the Rocky Mountains as winter gets underway in December. Forecasters are warning, though, that big changes will arrive around the time that 2025 begins.
“Look for a potential shift in the storm track midwinter,” Pastelok said. This new pattern will open the door for storms to track farther south over Central and Southern California and push inland.
January wettest?
January could be the wettest month of the winter for Los Angeles and San Diego, as well as areas farther inland across the Southwest, Accuweather predicts.
In February, the storms’ focus will shift north, once again focusing on the Pacific Northwest and northern and central Rockies. As a result, the ski season could come to an early end at the ski resorts in the mountains of Southern California, northern Arizona and New Mexico.
La Niña winters typically do not result in frequent atmospheric rivers in California, but with a weaker La Niña predicted this winter, it could allow for other factors to dictate the West Coast weather pattern. This is what happened in the La Niña winter of 2022-23 when nearly 40 atmospheric rivers hit the western U.S., many of which impacted California.
Of course that was the year Tulare Lake returned with a big bang.
More extreme weather?
The weather recently has been one of extremes driven by warming temps globally.According to the National Oceanic and Atmospheric Administration, August 2024 was the Earth’s hottest August in the agency’s 175-year climate record, and the Central Valley of California felt this.
UCLA climate scientist Daniel Swain has predicted extreme weather events across the US and California will be more frequent.Just look at what happened in the Appalachian Mountains experiencing “the worst regional flood catastrophe the United States has seen in some years (and likely the worst this region has experienced in recorded history). 20-35 inches of rain fell in less than three days in steep and mountainous terrain, causing rivers, creeks, and streams to not only spill their banks but literally carve new paths through mountain valleys — regardless of what was in the path.”“California faces a real risk of similarly catastrophic flooding.”
Other views
The Center for Western Weather and Water Extremes, or CW3E, based at Scripps at UC San Diego in La Jolla is modeling much of California with a very high chance (>90%) of the 2024-2025 water year being at least 75% of normal. For Sacramento, that would mean roughly 14 inches of rain. However, the chances of most of the state getting an average water year is not nearly as high, only about 20-50%. And the chances of an above average season? At least according to the CW3E data, less than 10-20% for most of the state.
Carol Connare, editor of the Old Farmer’s Almanac, forecasts a “calmer, gentler winter” for 2024-2025. “Temperatures are expected to be higher and snowfall lower throughout much of the United States,” Connare said. “While there will still be winter chill and plenty of powder to enjoy, the overall impact on costs and daily life should be less severe. This winter is anticipated to be relatively uneventful compared to the extremes of recent years.”
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