How California's Reservoirs Will Change After Atmospheric River Hits

California will escape much of the rainfall from an incoming atmospheric river, but the storm will still benefit some of the state's reservoirs.

An atmospheric river is forecast to saturate much of the Pacific Northwest over the next week. An atmospheric river is a "long, narrow region in the atmosphere—like rivers in the sky— that transport most of the water vapor outside of the tropics," according to the National Oceanic and Atmospheric Administration (NOAA). More than a dozen similar storms battered California last winter, and although the deluge alleviated much of the state's drought, it also wreaked havoc through flooding and mudslides.

The incoming storm could bring up to 2 inches of rain to two of the state's northern lakes.

AccuWeather senior meteorologist Adam Douty told Newsweek that the rain will reach Lake Shasta and Trinity Lake in northern California, and although it might not be enough to raise the lakes' levels by much, the storm will boost the area's average rainfall for December. In November, both Lake Shasta and Trinity Lake fell below average for rainfall, with Lake Shasta receiving only 50 percent of its average monthly amount, and Trinity Lake getting 68 percent.

"It'll give them a jumpstart on December," Douty said of the rainfall.

Both lakes are in a far better state than this time last year when drought plagued the state. Trinity Lake has risen nearly 60 feet in the past year, with Shasta Lake rising almost 100 feet during the same timeframe. However, Shasta Lake's water levels have fallen by 50 feet since their high point earlier this year, when the lake was documented at 1,063 feet in May and June, only 4 feet from its capacity. Trinity Lake levels also have fallen by approximately 20 feet since they peaked at 2,297 feet in July.

The lakes remain below capacity, though, with Trintiy Lake still below the historical average, according to a graphic by the California Department of Water Resources.

Lake Shasta is at 126 percent its historical average, but still at only 68 percent capacity. Trinity Lake is at only 49 percent capacity, a far cry from its historical average of 86 percent.

Rainfall is anticipated to begin on Friday and continue through Wednesday. The brunt of the storm will fall north of California, in Oregon and Washington, bringing up to 20 inches of rain in some areas. The atmospheric river's southern tip will pass through northern California, dumping up to 4 inches of rain on the state and potentially saturating the two lakes.

In addition to supplementing the reservoirs, the heavy rain also will prove beneficial to dry regions in northern California. Earlier this month, a drought monitor map timelapse video revealed that California was free from drought for the first time in years. There are still some abnormally dry regions in the state, particularly in the far north.