- A stronger stream of moisture is heading toward California at the end of the weekend.
- Life-threatening flooding and landslides are possible impacts in Southern California.
- Several feet of snow will accumulate in the Sierra Mountains and Southern California.
A strong atmospheric river will bring life-threatening flooding, a landslide threat, damaging winds and feet of mountain snow to California during the first week.
This will be the second such event for the “Pineapple Express” in California in just two days. The first storm caused flooding across the state, but the second round will be the “biggest storm of the season,” according to the National Weather Service office in Los Angeles.
The worst impacts are expected to occur during lunchtime on Monday afternoon.
(More: What do you know about atmospheric rivers?)
Life-threatening flash floods expected: On Sunday, the flood threat will be highest along the inland to coastal areas from Monterey to Los Angeles, especially in Santa Barbara and Ventura counties where the National Oceanic and Atmospheric Administration's (NOAA) Weather Prediction Center has issued its highest flood risk level. This area, shown on the map below, is very likely to experience flooding, rain, landslides, rockslides and travel disruption.
Rainfall rates on Sunday could become extreme for several hours.
(I notice: Why should you take these “high-risk” forecasts seriously?)
On Monday, that threat will shift south to Los Angeles and San Diego.
Here's what we're tracking now: Rain and snow will spread at high elevations from the northern and central parts of the state to Southern California.
Storms, tornadoes, and many feet of snow are also possible: In addition to heavy rain, strong winds are expected. Wind speeds may reach 80 mph in mountainous areas and across canyons and passes. Wind speeds could rise to 60 mph in lower elevations and urban areas, including Los Angeles. These winds have the potential to down tree limbs and cause power outages. Driving may become difficult through mountain passes.
Some thunderstorms are likely as this storm system approaches the West Coast. A few hoses, a tornado or two and some hail are likely.
Snow levels will start at 6,500 feet as moisture begins to flow ashore this weekend, then drop to about 4,500 feet. This will include some Southern California mountain peaks.
(Enhance your forecasts with our hour-by-hour breakdown for the next eight days – available only on our website Premium Pro experience.)
Here is the amount of additional rain and snow expected until the beginning of next week: Rainfall totals of several inches are expected in parts of California through at least Tuesday.
Mountainous and foothill locations in Southern California below the snow level can see between 5 to 12 inches of rain. Lower elevations along the coast and in valleys, including Los Angeles, may pick up 3 to 6 inches of rain, with locally higher totals possible. Be prepared for potentially dangerous flooding and landslide impacts due to the expected rainfall totals and the longevity of this wet pattern
Most of the state will see at least an inch of rain.
(More: Flash floods pose a serious danger. Here's how to stay safe.)
Elsewhere, snowfall in the Sierra Nevada will be measured in feet above 4,500 feet with up to 10 feet possible on mountaintops. There are likely to be significant impacts on travel, so it is best to postpone any driving plans starting Sunday. The mountains of Southern California will also see heavy snow creating dangerous travel conditions.
You can check back on Weather.com or the Weather Channel app for updates.
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