Inches of rain and feet of snow fell across the Western United States during the past week thanks to a series of powerful low pressure systems. The Pacific coast will stay active during the week ahead as multiple systems line to keep the storm pattern going.

A big difference between last week and the week ahead will be the much warmer temperatures that build into the SW around a ridge of high pressure. This ridge will send storms up the coast, instead of across the interior, and will keep snow levels much higher. As rain falls on top of snow, it melts increasing runoff. This typically leads to an increase in river flooding potential.

Timing

Heavy rain and snow will continue to impact the Pacific Northwest through the weekend, with snowfall in mountain areas leading to difficult travel. The rainfall rates will increase into Monday and Tuesday as a stronger system moves onshore, bringing tropical moisture to the north. This system will shift a bit farther south to start the week, bringing heavy rain into Northern California Monday afternoon into Tuesday. Snow levels are expected to be quite high, upwards of 8,000 feet, leading to rain falling on top of the feet of snow California recorded last week.

Precipitation & Flood Potential

Rainfall totals in Northern California and Southern Oregon could surpass 5-7 inches in some locations, with snowfall totals in the NW topping a foot. Temperatures appear to be too warm for heavy snow in the Sierra, outside of the highest peaks.

Flood potential increases on Monday and Tuesday, with flash flooding possible from California to Southern Washington.