Northern California is gearing up for a soaking wet week as an atmospheric river dumps heavy rain across the region. Forecasters say some areas could see up to 15 inches of rain, while the northern Sierra Nevada might get blanketed with multiple feet of snow.

This relentless stream of tropical moisture, often called a "pineapple express," is pulling water vapor from the subtropics near Hawaii. The result? A non-stop deluge that could last through Friday, raising concerns about potential flooding as the ground becomes increasingly saturated.

The coastal mountains are expected to bear the brunt of the rain, with six to 15 inches predicted. Meanwhile, the Sierra Nevada and Cascade Ranges are seeing snow—but only at the highest elevations, as the warm system keeps lower areas wet rather than white.

Meteorologists explain that this atmospheric river acts like a conveyor belt, channeling moisture from the Pacific Ocean straight into California. “It’s fueling periods of moderate to heavy precipitation as it moves inland,” said one weather expert.

Originally, forecasters thought two separate atmospheric rivers would hit the West Coast, but by Saturday, the systems had merged into one massive storm. Residents in flood-prone areas are being urged to stay alert as the soggy weather continues.

Whether you’re a fan of rain or not, one thing’s clear: Northern Californians should keep their umbrellas and rain boots handy this week.