The weather forecasting Web site said with heavy rainfall expected to hit the region through Saturday night, there is an increased risk for mudslides and debris flows because vegetation in the area was hit by multiple wildfires previously this year.
Meanwhile, heavy snow and rain is expected for parts of California, Colorado, Nevada and Utah through Sunday.
AccuWeather.com said snowfall could reach 1-3 feet in the mountains, while lower elevations could see up to 4 inches of accumulation.
The northeastern United States is also facing inclement winter weather with a rain storm expected for parts of the region Saturday into Sunday.
Freezing rain is possible in New York, Philadelphia and Washington.
AccuWeather.com said parts of Maine, Michigan, New Hampshire, New York and Vermont are expected to face up to 3 inches of snow through the weekend.