Pacific storm parade to aggravate flooding concerns in California
AccuWeather forecasters say the active weather pattern across the western U.S. will continue to deliver rain and snow to California and the interior Southwest.
A parade of storms from the Pacific will continue to hammer the West Coast of the United States, including California, this week. Each storm rolling in will have the potential to aggravate flooding and mudslide concerns and create life-threatening conditions, AccuWeather meteorologists say.
The stormy pattern will also continue to chip away at long-term drought conditions as it boosts snowpack in the Sierra Nevada, which have been picking up astounding amounts since New Year's Eve. There are indications that storms may arrive less frequently later this month with the potential for a break altogether for a time.
"Each round of rain falling on top of saturated and unstable ground will enhance the risk of new landslides and debris flows," AccuWeather Meteorologist Reneé Duff said. "Even seemingly moderate wind gusts can be enough to knock over scores of trees and trigger new power outages."
Rounds of gusty winds from the storms into early week will generally range between 40 and 60 mph at most locations but can be locally higher and double that over some of the ridges and peaks.
Following a break in the rain and mountain snow for much of the state on Thursday, the storm train ramped up again to end last week and will even continue into early this week. In some areas, rain and snow from one storm may blend together with the next.
While the long-term mega-drought condition in California has drastically improved from the recent onslaught of storms, the ground cannot handle more rain without immediate runoff and the potential for the topsoil on hillsides to let loose.
"Trees can topple over with no notice," Duff said. "The same saturated ground has top-heavy trees bobbing in the wet soil."
Another in a long series of storms reached California and caused a slew of more problems early this weekend. Evacuations were underway Saturday morning for part of Santa Cruz County as a new round of downpours swept through, quickly raising the water levels of the San Lorenzo River. Multiple areas of Napa County also began to flood Saturday morning.
Despite the seemingly endless storms that have delivered inches of rain and yards of high country snow, the weather pattern will begin to change ever so slightly in the coming days and more so late this month.
"The storms on track to impact California into early week will not be associated with a true atmospheric river like the events from earlier this month," Duff said. The storms will tend to be brief in nature with short plumes of moisture from the Pacific.
Still, storms may result in 6 inches of rain in as many hours and 6 inches of snow in 1 hour -- close to some of the output from recent storms. Even where less intense rain and mountain snow occur in the upcoming storms, major problems and disastrous conditions can unfold at the local level.
The storms coming in through early week will bring lower snow levels in the mountains, compared to many recent storms. That will translate to a bit less runoff at intermediate elevations in the Sierra Nevada, but it also means potentially more trouble for some of the passes along Interstate 5 in Northern and Southern California.
Motorists are encouraged to check local advisories for not only their destination but also high elevation points along their routes before they begin their journey. Rounds of heavy snow have the potential to shut down some of the passes periodically and not only along I-80 at Donner Pass, California.
During the new week, storms will begin to track from northwest to southeast along the Pacific coast. Storms that track like that can still bring locally heavy rain and intense mountain snow. Overall, the precipitation will tend to be more brief and sporadic in nature with increasingly drier episodes in between rounds.
By the end of the month, an area of high pressure may develop at most levels of the atmosphere over California and much of the Pacific coast, which can be strong enough to keep most moisture-packed storms away, AccuWeather Senior Long-Range Meteorologist Joe Lundberg explained.
Unlike in 2022, when storms vacated California during much of the winter, AccuWeather's long-range team of meteorologists expects the return of some storms later in February and March.
The storms thus far have already brought a tremendous amount of snow, loaded with moisture over the Sierra Nevada, which should gradually melt this spring. The relentless rain is filling reservoirs and runoff from rain that has already fallen or will fall into early this week will continue to flow into area streams, rivers, lakes and reservoirs. Many reservoirs have already recovered to levels not seen in a few years at this point of the season.
For example, water levels at Millerton Reservoir, located in the central part of the state, were hovering just above 150% of the average to date as of Friday, Jan. 13.
As the pattern begins to shift slightly this week, the brunt of storms will bypass California and dip across the interior southwestern United States, where and when mountain snow and desert rain are likely to be much more prolific, compared to much of the winter thus far. The moisture and runoff, later on, could be a boost for the depleted Colorado River.
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