Atmospheric river flowing our way; forecast: Back-to-back storms bring heavy rain to North Coast

The North Coast is forecast to receive significant rainfall through the weekend from two back-to-back storms, the first of which was predicted to hit around midnight on Tuesday, the National Weather Service said.

"The main thing for everybody to take away from this is we're going to get another good shot of rainfall this week, and this time it's going to be focused over the northern part of the area," meteorologist Scott Carroll said. "North of Cape Mendocino, especially Del Norte County."

The Eureka area is estimated to receive 3 to 5 inches and McKinleyville 5 to 7 inches, Carroll said. Higher elevations, especially those over the south and southwest facing terrain of Del Norte County, could easily see more than 10.

River basins such as the Smith could receive up to 12, and Redwood Creek might record 9 inches, according to the weather service.

While there is a potential for flooding, the rivers will most likely be OK because it's been so dry, Carroll said.

The weather service did issue an alert on Tuesday that the Smith, Mad and Van Duzen rivers may rise within 4 feet of the monitoring stage, and small streams and tributaries may occasionally exceed their banks, but at this point, the public just needs to keep an eye on the forecast, Carroll said.

Humboldt County Sheriff's Office Lt. Steve Knight said the office is not currently taking any extra precautions.

"The Office of Emergency Service is in communication with the weather service, but there's no indication there's going to be any issues for us at this time," Knight said.

The first storm is expected to taper off tonight with the second system hitting by Thursday.

During both events, southerly winds, which force air up the southern side of the hills and mountains and back down the northern side, are expected.

"Any time you have air going downward, it's a drying effect, so we end up having less rainfall around Humboldt Bay in Eureka, Arcata, McKinleyville, as opposed to heavier rains on terrain that faces south," Carroll said. "So that's why we expect heavier rains along the King Range and southwestern Humboldt County."

The storm systems are being caused by an "atmosphere river of moisture," according to Carroll.

"We get areas of low pressure over the Pacific that pump in tropical and sub-tropical moisture that comes up in bands from Hawaii," he said. "It's a combination of just a huge amount of moisture, and then the fact that we have a lot of terrain along the West Coast that it's forced over.

"The combination of those things leads to pretty heavy rainfall amounts," he added.

The persistent ridge of high pressure that has propelled storms away from the West Coast for more than a year is still there, but it's a lot weaker and has been pushed farther south, Carroll said.

Lorna Rodriguez can be reached at 441-0506 or Follow her on Twitter @LornaARodriguez.