Rounds of storms will target the West Coast into early next week, including several of the atmospheric river variety.
An active pattern is in place across the West. The first storm and atmospheric river arrived late Thursday, bringing Oregon the third round of freezing rain this week. After that storm, California will get a fire hose of rain through Tuesday while the Pacific Northwest gets a glancing blow.
Weather models show storms getting a tropical connection, which means heavier rain and snow but warmer temperatures.
“The first AR (atmospheric river) is forecast to bring heavy precipitation to the Pacific Northwest, including snowfall in the Northern Cascades and freezing rain in the Portland Metro area and regions along the Wahington/Oregon border through early Friday 19 Jan,” the forecast from the Center for Western Weather and Water Extremes (CW3E) read Thursday.
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The second and larger AR makes landfall late Sunday. A potential third follows on Tuesday.
“The second and third ARs are forecast to bring precipitation to the USWC (West Coast), with the heaviest precipitation expected from the second AR over the California coast and in the Sierra Nevada, where heavy snowfall is forecast through Tuesday 22 Jan,” wrote forecasters at the CW3E.
No rest for the weary, though. The CW3E said a potential fourth AR could bring heavy rain and snow with high winds to the Pacific Northwest Jan. 25-27 – the end of next week.
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As the ARs are generally warmer storms, watch for snow levels to rise and rain to fall on the fresh snow from this week to exacerbate inland flooding.
Heavy rains on Saturday into Sunday will make flash flooding likely along the coast and coastal ranges from Oregon to almost Los Angeles.
The mention of a parade of AR-charged storms instills fear in many Californians who are still repairing after the record rain and two-winters worth of snow that walloped the state last winter.
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Like last winter, soils are getting saturated this season. Locations around the San Francisco Bay Area could see landslides as that happens.
“USGS (U.S. Geological Survey) instrumentation throughout the San Francisco Bay Area indicates that shallow soils on steep hillslopes are approaching saturation,” wrote the San Francisco NWS Office in the hydrologic outlook. This coupled with the forecasted precipitation means widespread shallow landslides are likely.”
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Through Wednesday, the North San Francisco Bay coast and coastal ranges could see up to 5 inches of rain, more locally. Los Angeles could see widespread 1-2 inches of rain with up to 3 inches in the coastal ranges. The NWS warned that favored peaks and higher elevations could see up to 7 inches.
Points south of the Bay Area could see 4-6 inches.
Freezing rain continues through Friday morning for Oregon, especially the Columbia River Gorge, and parts of eastern Washington. Snow in the Cascades will wrap up during the day. Look for about 3-6 inches of snow in Washington with 6-12 inches of snow in Oregon.
Heavy rain moves into Northern California on Friday night along with breezy to gusty winds. Overnight, there is even a chance for a couple of thunderstorms.
The heavy rain peaks Saturday and gradually eases into the evening. The 49ers-Packers NFL playoff game on Saturday night will still be wet.
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Southern California, including Los Angeles, will see heavy rain Saturday afternoon into Sunday morning.
The next round of heavy rain makes its way to Northern California for Sunday afternoon and evening with possible thunderstorms.
Monday will be relatively drier for the Golden State, with occasional showers. Tuesday brings the next shot of heavy rain.