Jan 6, 2017

California Will Be Pummeled By Atmospheric River Event This Weekend; Heavy Rain and Snowmelt to Cause Flooding and Landslides

Sierra Nevada, California
Jon Erdman
The Weather Channel
Image: The Weather Channel
Image: The Weather Channel

Another multi-day siege of flooding rain and Sierra snow will take aim on California starting this weekend, which will eventually prove to be too much of a good thing for residents still thirsting for relief from a five-year drought.

Winter Storm Helena brought the first round of heavy mountain snow and rainfall to the state Tuesday into early Thursday. Flooding and some landslides were reported, while feet of snow piled up in the Sierra Nevada.

Starting on Saturday and continuing through Monday, another very potent atmospheric river event will deliver even heavier rainfall to California, with rising snow levels resulting in a significant threat of flooding from snowmelt. The National Weather Service says that flooding with this event may be the greatest since December 2005.

Flood and flash flood watches have been posted for parts of northern and central California, including the Sierra Nevada, where the National Weather Service cautions rapid rises on small streams, flooding of roads, debris flows and rock slides are possible. Rainfall totals of up to a foot are not out of the question along the western slope of the Sierra Nevada this weekend into Monday.

With warmer air moving into the region, snow levels may rise as high as 9,000-10,000 feet in parts of the Sierra Sunday morning into Monday morning, leading to plenty of melting snow. The Carson, Consumnes, Merced, Susan and Truckee Rivers could all experience some flooding from the heavy rain and snowmelt runoff.

In the Yosemite Valley, the Merced River could top out near its record level set in a January 1997 flood that caused $198 million in damage. A closure of Yosemite National Park is possible in advance of the flood event, according to officials.