Life-threatening flooding will continue to wallop northern and central California into the middle of the week.
Several moisture-laden storms will crash onto the California coast, unleashing torrential rainfall and significant snow into Wednesday.
The first wave of heavy rain pushed across California on Sunday.
The next round of heavy rain and mountain snow will slam into northern and central California Tuesday into Tuesday night, AccuWeather Senior Meteorologist Kristina Pydynowski said.
Cumulative rainfall into midweek could surpass a foot across the northern California coast ranges and west-facing slopes of the Sierra Nevada. Two to 8 inches of rain are expected across the Sacramento and San Joaquin valleys.
“The siege of storms has the potential to wipe out or greatly erase the long-term drought conditions in the region,” AccuWeather Senior Meteorologist Alex Sosnowski said.
The rain will have a hard time absorbing into the soil with each passing storm. As a result, incidents of urban flooding, river flooding, mudslides and rock slides will only increase into midweek.
Significant flooding, mudslides and rock slides were reported shortly after the first wave of rain moved ashore on Sunday.
“Communities protected from levees around Sacramento and Fresno will want to keep a careful watch on the water levels,” AccuWeather Meteorologist Jordan Root said.
"Rivers and streams that flow out of the Sierra into the lower foothills and valleys on California and also into western Nevada will likely see the worst flooding in a couple of decades," AccuWeather Senior Meteorologist Ken Clark said.
"The greatest potential for destruction comes from the rivers that have little or no flood control, such as dams and catch basins," Clark said.
Residents should heed all evacuation orders issued by officials. Motorists will not only need to be aware of the threat for ponding of water on roadways, but also blocked roads due to flooding and debris flows.
Trees and power lines will be compromised due to the saturated soil. Gusty winds with each storm could continue to easily knock down trees and cause power outages. Motorists will face dangerous crosswinds, while airline passengers should prepare for delays and cancellations.
Some rain will reach Southern California, including Los Angeles and San Diego. These areas will experience more dry breaks in between rainy periods, which will lower the flash flood threat to a localized level.
After remaining above 9,000 feet over the weekend, snow levels will fall to around 5,000 to 6,000 feet into Wednesday.
During the transition from rain to snow, travelers over the mountain passes should use extreme caution. Wet roads could quickly turn snow covered and slick.
As the snow intensifies, travel will be extremely dangerous, if not impossible, over the mountain roads. Officials may be forced to close I-80's Donner Summit for a time.
By Wednesday, the northern California coast range and Sierra will be buried under several feet of snow.
“The extreme snow will be a boon for the ski industry and for the region's water reservoirs in the coming warm months," Pydynowski said.
Outside of northern California, most of the state may experience a break from the storm onslaught late this week into next weekend.
"A pattern change later this week will cause the path of the best moisture to work into Washington and Oregon more often than California," AccuWeather Meteorologist Evan Duffey said.
"Central and southern California will be much drier toward the end of this week and into next week. It will be warmer as well toward the end of the week in the Sierra, so some of the recent snow will melt as well," he said.