LAKE COUNTY, Calif. – Northern California is in the path of what forecasters predict to be another intense storm, the product of an atmospheric river.

Forecasters said a series of weather systems will move into the region early this week, with the wettest storm expected Monday and Tuesday.

The storms are the result of an atmospheric river, according to the National Weather Service.

The National Oceanic and Atmospheric Administration describes atmospheric rivers as relatively long, narrow regions in the atmosphere that transport most of the water vapor outside of the tropics.

“These columns of vapor move with the weather, carrying an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River. When the atmospheric rivers make landfall, they often release this water vapor in the form of rain or snow,” the agency said.

With such an impending heavy storm, the National Weather Service issued a flood warning for Lake and numerous other Northern California counties that’s in effect through 4 p.m. Thursday.

With the entire regional already saturated from recent storms, and many areas experiencing flooding, the National Weather Service expects interior Northern California to experience an uptick in flooding as well as impacts on areas that haven’t flooded in many years. There also are concerns regarding additional stress on creeks, levees, rivers and streams.

This winter’s rainfall has kept Clear Lake in flood stage, which resulted in the Board of Supervisors closing it to motorized vessels on Tuesday until the water recede to a safer level.

Clear Lake’s elevation was at 9.84 feet Rumsey shortly after 12 a.m. Sunday, according to the United States Geological Survey.

The California Nevada River Forecast Center predicts that Clear Lake’s elevation will continue to rise and on Tuesday will pass 10.5 feet Rumsey.

That would be Clear Lake’s highest elevation since the 1998 flood, when the lake topped out at 11.44 feet Rumsey, according to the United States Geological Survey’ historical data on the lake.

The specific Lake County forecast calls for rain on Sunday, followed by heavy rain on Monday. Rain also is likely on Tuesday and on Wednesday morning, before the weather clear through Friday night.

The expectations of more rain come as Lake County has just come through two days of rainy weather.

Forty-eight hour totals from local National Weather Service stations for the period ending just before 1 a.m. Sunday showed the following rainfall totals: 1.20 inches in Upper Lake, 1.33 inches in Hidden Valley Lake, 1.83 inches in Kelseyville, 2.39 inches on Putah Creek in Middletown, 2.56 inches in Whispering Pines, 2.64 inches on Cache Creek near Lower Lake, 3.23 inches at Indian Valley Reservoir and 4.14 inches in Boggs Mountain.

Around Lake County, there continue to be impacts on local roadways and facilities.

In Lakeport, Library Park is closed to the public after having been inundated by water and battered by wind and waves over the last several days.

Due to concerns about a landslide and road failure on New Long Valley Road – the main roadway into the Spring Valley community east of Clearlake Oaks – the Lake County Public Works Department reported that a full closure of the road will go into effect on Monday while a temporary bridge is installed.

Residents of the Spring Valley area are urged to evacuate or to be prepared not to be able to leave the community until as late as Thursday.

A closure of Highway 20 at Highway 53 for eastbound traffic, which had been implemented Friday due to flooding near Williams, was lifted on Saturday, according to the California Highway Patrol.

Additionally, Caltrans said early Sunday that Highway 20 at Highway 16 also had opened to one-way traffic with a fire escort.

Email Elizabeth Larson at This email address is being protected from spambots. You need JavaScript enabled to view it. . Follow her on Twitter, @ERLarson, or Lake County News, @LakeCoNews.