SAN FRANCISCO – A powerful bomb cyclone is slamming the West Coast through Thursday.
The cyclone is pulling in a narrow but concentrated feed of tropical moisture, called an atmospheric river, which extends from Hawaii to California. This specific type of atmospheric river is known as the Pineapple Express as its moisture source originates near Hawaii.
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The result of the atmospheric river will be intense lower-elevation rain and high-elevation snow that will fall across the entire state of California. This will be one of the most significant storms to impact the state in years.
The maps below from the FOX Forecast Center show the latest information on the storm’s path across the state, including active weather alerts and power outages as they unfold.
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Rain and snow are underway with the arrival of a well-defined warm front. This will produce heavy rain across the region, though the heaviest rain, and greatest risk for dangerous flooding, will unfold later in the day and continue into Wednesday night and Thursday as the trailing cold front and a coinciding plume of copious moisture moves onshore.
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With very high winds, combined with the saturated soils, numerous downed trees will be likely. Power outages are all but assured in California, especially across the northern part of the state.
With soils saturated after 3 to 12 inches has fallen in the past two weeks, the additional water will have nowhere to go. As a result, numerous instances of flash flooding and mudslides are expected. Over half the state is under a Flood Watch.
Considerable and life-threatening flooding is especially possible along the Northern and Central California coast. Around recent burn scars, there is a considerable debris flow risk. Rivers across the state are forecast to rise into flood stage.
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The powerful bomb cyclone will also cause very strong winds to sweep across California. High Wind warnings are in place as wind gusts could approach 60 to 70 mph.
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Widespread accumulations of 2 to 4 inches of rain are expected, with a high likelihood for totals approaching 10 inches in the higher terrain. While any rain is beneficial in California, this will likely come at a significant cost.
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Up in the mountains, dangerous travel conditions are developing and will continue through Thursday night.
Extremely heavy snow rates greater than 3 inches per hour are near certain above 5,000 feet in elevation. This will lead to dangerous, if not impossible, travel conditions.
In total, an additional 1 to 4 feet of snow is expected across the Sierra Nevada. In Southern California, the highest peaks of the mountains will pick up 1 to 2 feet.
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There’s no rest for the weary.
Another atmospheric river will blast the state this weekend and then yet another powerful one is likely next Tuesday and Wednesday. Each will bring a renewed round of dangerous flooding.
Over the next week, as much as 20 inches of rain may fall in the northern parts of the state.