Atmospheric river to bring rain, snow to Northern California. Here’s when
Time to pull out umbrellas and rain boots.
Northern California is forecast to see thunderstorms as an atmospheric river rolls through the region, according to the National Weather Service.
“A weather system brings active weather back to (Northern California) mid- to late week, with widespread rain, isolated thunderstorms, gusty winds and mountain snow,” the weather agency wrote on X on Sunday, Nov. 9.
The atmospheric river will center on Northern California and the Central Valley.
“While forecast specifics will become more apparent in the coming day, users are encouraged to stay tuned as isolated flooding and heavy elevation snowfall are possible with this upcoming system,” the National Weather Service said in a news release Monday, Nov. 10.
Here’s when and where to expect rain:
Which parts of California will see rain?
The atmospheric river is forecast to bring heavy rain, lightning and thunderstorms to parts of California, the National Weather Service said.
In Northern California and the Central Valley — including Sacramento, Modesto, Merced and Fresno — rainfall is expected to begin Wednesday, Nov. 12.
How much snow will fall in Sierra Nevada?
Areas across the Sierra Nevada are forecast to see snowfall.
“An incoming storm system is expected to bring widespread precipitation and mountain snow above 5,000 feet,” the National Weather Service wrote on X.
South Lake Tahoe will see up to 6 inches of snowfall, according to the weather agency.
What is an atmospheric river?
According to the National Oceanic and Atmospheric Administration, an atmospheric river is an area in the atmosphere that carries water vapor outside of the tropics.
“The average atmospheric river carries an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River,” the administration’s website says.
When an atmospheric river “makes landfall,” it often releases this water vapor in the form of rain or snow.
“Those that contain the largest amounts of water vapor and the strongest winds can create extreme rainfall and floods,” the weather agency said.
During the atmospheric river event, the National Weather Service said, there is a high risk of heavy precipitation that could lead to flooding and snowfall.
Am I at risk for flash floods?
According to the National Weather Service, flash floods can happen for several reasons, but they’re most often triggered by heavy rain from thunderstorms.
How fast flooding happens depends on several factors, including where the rain falls, how intense it is, the shape of the land, soil type and how wet the ground already is.
Starting Wednesday, Nov. 12, there are risks for flash floods in parts of the Bay Area, Northern California and the Central Valley — including Merced and Fresno.
However, the “probability of rainfall exceeding flash flood guidance” is less than 5%, according to the National Oceanic and Atmospheric Administration.
What’s in the weather forecast for Modesto?
On Tuesday, Nov. 11 — Veterans Day — Modesto will see cloudy skies with a high temperature near 75 degrees and a low temperature around 56 degrees, according to the latest forecast from the National Weather Service.
Wednesday will bring a high of about 73 and a low near 59, with an 80% chance of rain after 4 p.m.
Rain will continue Thursday, with a 90% chance of precipitation after 10 a.m., the weather service said.
The high will be around 62, while the low will be near 48.
Friday’s forecast calls for a chance of showers, with a high near 59 and a low around 47 degrees.
Clear and sunny skies are expected to return to Modesto by Saturday, Nov. 15, according to the weather service’s seven-day outlook.
How much rain will Modesto get?
According to the National Weather Service, the atmospheric river is expected to bring around 1.5 inches of rain to Modesto.
Modesto has received approximately 1.2 inches of rain this season, which began on July 1 and will continue through June 30, 2026.
How to drive safely on roads during rain
Drivers should watch out for slick roads as rain returns.
Rain, coupled with speeds of 50 mph or more can result in your tires losing contact with the road, according to the Department of Motor Vehicles’ California Driver Handbook.
When it rains, drive up to 10 mph slower.
“Slow down at the first sign of rain, especially after a dry spell,” the DMV said on its website. “A slippery road will not give your tires the grip they need.”
If your vehicle starts “riding on water” or hydroplaning, slow your car down gradually. Do not use the brakes.
