Get ready California, here comes the Pineapple Express and it’s expected to bring plenty of rain and snow.

That’s a stream of moisture in the sky — technically an atmospheric river — originating in the Pacific Ocean near Hawaii and landing in California. This one may touch off mudslides in areas scorched by last year’s wildfires and drop much-needed snow by the foot in the Sierra Nevada, said Dan Petersen, a forecaster with the U.S. Weather Prediction Center in College Park, Md.

Flash-flood watches have been posted across valley areas of Southern California including Santa Monica, Beverly Hills and Hollywood, the National Weather Service said. Rain may fall at 1 inch an hour in many places with a widespread area getting 4 to 6 inches (10 to 15 centimeters) before the storm winds down Thursday.

To maintain its water supply, California needs to build up a deep snow pack before the storm season ends in a few weeks. The state had been lagging in snow this season and, beyond the areas served by reservoirs and irrigation systems, just under half of California is facing drought conditions, according to the U.S. Drought Monitor in Lincoln, Neb.