Atmospheric rivers continue along the West Coast, as a parade of storms threaten high winds, heavy rain and flooding next week. FOX Weather Meteorologist Jane Minar analyzes the threat facing the Northwest.
After an extremely active week in the Pacific Northwest, a shift in the weather pattern across the west coast now takes aim at California, thus giving overwhelmed areas in the region a much-needed break.
Rounds of rain, snow and wind are set to slam California starting Sunday, elevating flash flooding concerns that start across portions of Northern California and last through the rest of the week.
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Three rounds of precipitation are expected to bring travel headaches to the entire state of California, affecting the state’s largest airports, including Los Angeles International Airport, San Francisco International Airport and Sacramento International Airport, as well as throwing a wrench in transportation for vehicular travelers on I-5, I-10, I-15, Highway 101 and I-40.
The activity begins Sunday as the next atmospheric river shifts south, positioning itself across Northern California. A strong area of low pressure moves into the Gulf of Alaska while high pressure over Southern California acts to funnel moisture from Hawaii—making this a classic “Pineapple Express.”
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Some areas could see a month’s worth of rain, while others could see most of their yearly average in just a few short days.
With the surge of moisture aimed directly at the California coast, widespread rain is now likely across most of Northern California starting Sunday. Flash flooding is expected from the Napa Valley north to Chico. A Level 3 of 4 (Moderate) flash flood threat now exists for Northern California and the northern Sierra Nevada foothills.
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Further south, a Level 2 of 4 (Slight) threat includes major cities like San Francisco and Sacramento. Flood watches have already been issued for most of Northern California through at least Friday.
Widespread totals of 3 to 5 inches of rain are expected across Northern California, including coastal regions. Higher totals are forecast for the northern Sierra Nevada foothills, where 5 to 8 inches are possible, with some isolated areas reaching up to 10 inches by Tuesday. Debris flows in recent burn scars are a distinct possibility, but river flooding will be more widespread, especially near the California coast.
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The snow-starved Sierra Nevada will finally see impactful snowfall, allowing ski resorts to thrive this season. Coastal impacts are also likely starting Tuesday into Wednesday, with wind gusts as high as 80 mph possible.
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From Tuesday night into Wednesday, a second round of flooding rain and powerful winds will move onshore in Northern California. This storm is expected to intensify as it moves inland, bringing wind gusts up to 80 mph to coastal areas and the potential for even more flooding, according to the FOX Forecast Center.
Some forecast models indicate this system could become a bomb cyclone as it approaches the coast early Wednesday morning. Flash flooding remains a threat across most of Northern California as additional heavy rain impacts the region. National Weather Service San Francisco has advised locals and tourists to stay away from the Pacific coast as the storm moves in.
FILE: A school bus drives through floodwaters in Rialto, California, US, on Tuesday, Feb. 6, 2024.
(Kyle Grillot/Bloomberg / Getty Images)
Moisture will also shift south during this second round. Rain is expected to move down the coast through Central and Southern California into Christmas Eve and Christmas Day, significantly impacting holiday travel along the I-5 corridor. Current forecasts call for 3–5 inches of rain in the Los Angeles metro area.
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If Los Angeles receives over 3.82 inches, it would mark the wettest two-day Christmas Eve/Day period on record. A final round of moisture is expected to move through the state late Thursday into the weekend. With soils already saturated from nearly a week of rain, the risk of flash flooding will be significantly increased.
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There is a silver lining for the mountains: snow levels are expected to drop to pass levels (5,000–6,000 feet) approaching Christmas Eve. While this will cause major travel impacts, it is much-needed relief for the Sierra Nevada, which is currently sitting well below average—northern zones are at just 5% of their normal snowpack, while southern regions are closer to 40%. Heavy snow is also likely across portions of the Rockies as moisture spills into the Intermountain West.
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