100″ of snow in a week: Atmospheric river bringing rounds of heavy snow to Sierra Nevada mountains

Moisture could could help ease Western drought, but also cause flooding

Estimated snow through Friday morning
Estimated snow through Friday morning

ORLANDO, Fl – It’s a snow lover’s dream. The Sierra Nevada mountains will continue to get pummeled with powder through the end of the week. A series of storms will ride down the West Coast of the U.S. bringing lower elevation rain and heavy mountain snow to California.

An atmospheric river (narrow green stripe) will set up on the West Coast of the U.S. by the middle of the week producing heavy rain and mountain snow for much of California.

An atmospheric river is a narrow flowing column of moisture responsible for producing significant rain and/or snow. These are most common along the West Coast of the U.S. with developing Pacific storms. The ribbon of moisture can extend back thousands of miles.

West Coast Storm

An upper-level low sliding down the California coast will induce the atmospheric river allowing for continuous heavy rain and snow for days.

A skiers paradise

A second component of the atmospheric rivers out west are the mountains. As the Pacific moisture is brought in by the upper low, it is then slammed up against the Sierra Nevada mountains in this case. The moisture is then forced up the mountains where it cools and condenses. This is known as orographic lift. This process enhances precipitation on the western facing slopes. If cold enough, significant snow will fall.

Through the end of the week, more than 8 feet of snow could fall along part of the Sierra Nevada range. That is up to 100″ of snow in about 6 days going back to Sunday night.

Estimated snow through Friday morning

For perspective, Mammoth Lakes, California receives 206″ of snow on average for the season! For the month of January, the average snowfall is 43.1″

A Catch 22

Much of the West and Desert Southwest have been dealing with an extreme to exceptional drought for quite some time.

From the USDA. Extreme to Exceptional drought conditions continue for much of the West and Desert Southwest

Too much rain at once, however, is never a good thing. The rounds of heavy rain will no doubt help to ease some of the drought, but it could also produce significant flash flooding and mudslides.

Estimated rain and liquid equivalent of snow

Mudslides and flash flooding will be most likely in areas that were just devastated by wildfires in 2020. In these areas, vegetation that would have otherwise helped “hold back” the land from sliding was burned in the fires.

This satellite image provided by the National Oceanic and Atmospheric Administration (NOAA) at 15:31 UTC (7:31 a.m. PDT) on Wednesday, Sept. 9, 2020, shows brown smoke from wildfires blowing westward, from California's Sierra Nevada to the Coast Ranges, at center to left, and from Oregon at top left, affecting air quality throughout the West. Smoke mixes with clouds and overcast along the coast. Millions of acres of wildland and many homes and other structures have been lost to the flames. (NOAA via AP) (National Oceanic and Atmospheric Administration)

About the Author:

Jonathan Kegges joined the News 6 team in June 2019 as the Weekend Morning Meteorologist. Jonathan comes from Roanoke, Virginia where he covered three EF-3 tornadoes and deadly flooding brought on by Hurricanes Florence and Michael.