Biggest storm of the year is about to hit Northern California. When to expect the worst of it

Clear out the gutters. Plan some extra time for the morning commute Wednesday. And don’t even think about heading up the hill for a few days.

The biggest storm of the season is barreling down on Northern California.

The Sacramento region could see up to 3 inches of rain this week – perhaps doubling the amount of rain we’ve received for the entire winter season – as an extreme storm arrives Tuesday afternoon. The cold, wet system will bring dangerous winds to the region, localized flooding and up to 80 inches of snow – yes, that’s nearly 7 feet – to the summits on Interstate 80 and Highway 50.

“This is definitely looking like the storm of the year up to this point,” said Hannah Chandler-Cooley, a forecaster with the National Weather Service.

Mountain travel “will be EXTREMELY DIFFICULT to near IMPOSSIBLE,” the National Weather Service’s Sacramento office tweeted Monday. “If you must travel, carry chains, have an emergency kit & check road conditions before you go.” Road closures are likely. Wind gusts of close to 100 miles per hour are possible at the highest peaks.

If you’re a skier hoping to take advantage of the conditions, there might be some good news: Friday and Saturday might bring a reprieve from the dangerous conditions, Chandler-Cooley said, before another system potentially arrives on Sunday.

The NWS has winter storm watches or warnings in place from Tuesday through Friday for effectively all of the mountains, foothills and some of the northern third of the Sacramento Valley.

The anticipated snow totals are stunning. As of Monday, NWS predicted that 2 to 5 feet of snow could fall across the majority of the Sierra between Tuesday evening and Friday morning, with totals between 7 and 8 feet possible at some higher elevations. Blue Canyon, at around 5,000 feet elevation, could see up to 60 inches of snow.

Snow could fall at elevations as low as 500 feet Tuesday night into Wednesday morning, but those low snow levels are most likely in Tehama, Butte and Shasta counties in the northern reaches of Sacramento Valley. Closer to Sacramento, snow could fall as low as 1,000 or 1,500 feet, so areas around Auburn and Placerville may see another round of accumulations.

Snow levels are expected to rise to 2,500 to 3,000 feet Wednesday, and then to between 3,000 and 4,000 feet Thursday morning.

Sacramento rain forecast

The Sacramento Valley, along with the Bay Area, will get a dumping of rain. Forecasts show 2 to 3 inches falling between Tuesday and Friday in Sacramento; 7½ inches could fall in Grass Valley.

After a hard freeze warning Monday night into Tuesday morning for Sacramento, forecasts show gusts could reach 55 mph by Tuesday evening. An inch of rain is possible Tuesday night, and while Wednesday is expected to bring less precipitation, winds could again gust very high, up to around 45 mph in Sacramento.

That means the Wednesday morning commute will likely be a mess, Chandler-Cooley said. Rain will likely pond on roadways and some localized flooding is possible. Gusts near 50 mph will almost certainly knock down branches and small trees, and could lead to power outages.

The NWS in an infographic said the storm is expected to have “extreme” impact Tuesday and Wednesday in interior Northern California, “high” impact Thursday and may begin to subside by Friday.

The storm comes from an atmospheric river, which the weather services writes is “a flowing column of condensed water vapor in the atmosphere responsible for producing significant levels of rain and snow.”

Power atmospheric river systems like this week’s have been responsible most of California’s biggest storm and flooding in the past few years.