A double-barreled storm will affect a large part of California from Friday to Monday with areas of drenching rain and mountain snow.
The two rounds will bring needed moisture to some abnormally dry areas, including areas hit hard by wildfires in recent weeks. However, too much rain may fall and cause problems in terms of travel delays and isolated minor flooding.
Storms to deliver soaking rain in low elevations of Northern California
Up to a few inches of rain is forecast to fall along the west-facing slopes of the Coast Ranges and Sierra Nevada into early next week.
"While less rain will fall along the east-facing slopes, enough rain may still fall to cause flash flooding and mudslides, especially in recent burn scar areas," according to AccuWeather Senior Meteorologist Mike Doll.
In lieu of any flooding or debris flow from the rains, the storms will help to soak the soil and dampen brush and other potential fuel for the blazes.
As a result of the rainfall, many areas of Northern California will be much less prone to wildfire ignition this weekend and next week.
In San Francisco and Sacramento, California, one round of rain is forecast from Thursday night to Saturday. A second and perhaps heavier round of rain may occur late Sunday night into Monday.
Airline delays are possible with both rounds in Northern California.
Some rain is also likely to reach Southern California
The first batch of rain is likely to be light and spotty in the Los Angeles and San Diego areas from Friday to Saturday. However, even a small amount of rain mixed with oil and other residue on area roads can lead to slippery streets, highways and intersections.
A second and perhaps more widespread bout of rain is possible in Southern California later Sunday to Monday.
While the first batch of rain will do little to soak the ground, the second batch might be enough to have the same short-term impact as Northern California. The rain may lower the risk of wildfire ignition for at least a few days following the storm.
A little rain is likely to survive the trip east of the Sierra Nevada across northern Nevada this weekend. However, any rainfall farther south toward Las Vegas is likely to be limited to spotty showers early next week.
Storms to deliver snow to mountains, passes
While colder air will be drawn southward from the Northwestern states with the first storm this weekend, not enough cold air is likely to be around to bring snow to Tejon and Cajon passes in Southern California.
The high country of the Sierra Nevada will receive 1-2 feet of snow from the storm combination as the freezing level lowers over the weekend.
Periods of rain and snow are likely over Donner Pass, along Interstate 80 in California.
"It may not be until Friday night before it is cold enough for accumulating snow at Donner Pass," according to AccuWeather Lead Storm Warning Meteorologist Eddie Walker.
"Because of marginal temperatures during the day, the most likely time for slippery travel over Donner Pass will be at night on Saturday and Sunday," Walker said.