A strong and long-lasting atmospheric river is expected to hit Northwestern California this week, with moderate to locally heavy rainfall bringing the potential for rapid rises in rivers, streams and creeks across the region, the National Weather Service said.

The atmospheric river – a narrow corridor of concentrated moisture coming from the Pacific Ocean – marks one of the strongest storms to hit the region this season. The river storm is expected to bring a deluge of downpours, flooding and hazardous conditions to the region later this week.

An atmospheric river hit the Pacific Northwest last weekend, with a second round of heavy rain and snow earlier this week. Bad weather conditions are also expected in Oregon and Washington through Thursday.

On November 15, the Center for Western Weather and Water Extremes highlighted the potential for this event to reach an AR4 or even AR5 on its scale – indicating a strong to extremely atmospheric river – especially along the southern Oregon coast.

Meteorologists warn that rainfall from storms could easily reach between 15 and 14 centimeters over four days, with up to 21 centimeters forecast for the King Range, posing significant risks to communities and infrastructure.

Last winter, the West Coast experienced a slew of atmospheric rivers that caused devastating floods and landslides. However, the storms also brought a deluge of rain that replenished California’s lakes and rivers, easing the state’s drought.

If the atmospheric river hits as expected, northern parts of the North Bay will likely bear the brunt of the atmospheric river, but those effects could shift slightly southward, closer to San Francisco Bay, Fox News reported.

Cities on the North Coast could be inundated with more than 10 inches of rain, while San Francisco and Oakland could get 1 to 4 inches, according to the National Oceanic and Atmospheric Administration’s weather forecast web page, Fox reported.

Rain will be heaviest on Wednesday, the NWS said, with 2 to 4 inches of rain, while high peaks in the King Range could see 6 to 10 inches of rain in 24 hours.

The agency predicted more moderate but persistent rain would continue to fall Thursday through Saturday, with rainfall of 1 to 3 inches per day likely.

Further out, however, the predictions are more uncertain. Long range models show the chance of rain continuing into the week of Thanksgiving.

Newsweek contacted the NWS via email Monday outside of normal business hours for comment.

The greatest risk is in Humboldt and Del Norte counties, where soils are already near saturated, the NWS said. Significant rain is also expected in Mendocino and Lake counties, although drier soils should reduce flood risk.

Much of Trinity County’s precipitation will likely fall as snow, with snow levels reaching as high as 2,500 feet in the eastern half of the county, the agency said.

The NWS has warned of the risk of flooding in the region, especially for the northern half of the area, where previous rains have already saturated the soil.

It added: “Expect flooding in low lying areas, areas with poor drainage and an increased risk of debris on roads. Rivers, streams and creeks will rise quickly. There is about a 20 per cent chance of the Eel River exceeding flood stage on Thursday evening.

“The Mad River and Russian River are showing 5 to 10 percent reaching flood stage.”

Residents of the affected areas are advised to monitor weather forecasts in the coming days as confidence in the forecasts and details is likely to increase. In addition to rain, the storm is also expected to produce widespread damaging winds.

Emergency alerts, evacuation resources and real-time updates can be accessed through the NWS and local authorities.