A dangerous winter storm has arrived in California and will unload feet of snow, powerful winds and rare blizzard conditions in the mountains through the weekend.

The storm will bury California under its biggest snowfall of the year posing a significant danger to travelers – but provide a huge boost for the state’s water supply and tourism.

Winds gusted over 140 mph in the highest peaks of the Sierra Nevada alongside heavy snow Thursday. The powerful storm will unload these extreme winds and even heavier snow through the weekend, creating long-lasting blizzard conditions.

“Travel over Sierra passes has already become treacherous and will only deteriorate as we go into the weekend,” the the National Weather Service office in Reno, Nevada, warned Friday. “The time to hunker down is upon us.”

Snowfall rates are expected to reach extreme levels of 3 to 5 inches an hour from Friday through Saturday – especially along the Sierra Nevada.

The prolonged extreme snowfall means 6 to 12 feet of snow could bury parts of the mountains in just a matter of a few days.

The most extreme conditions will unfold at the highest elevations, with wind gusts in excess of 100 mph expected on the highest peaks of the Sierra in addition to feet of snow. Winds are expected to blow so hard that it may be difficult to measure snow accurately with the potential for huge snow drifts.

Winds started to roar Thursday with widespread gusts of 60 to 80 mph reported for elevations above 3,000 feet.

Heavy snow and roaring winds are expected to combine to produce rare and long-lasting blizzard conditions for much of the Sierra and parts of the northern ranges. Visibility could plummet to near-zero, meaning it’s impossible to see farther than a few feet – or at all – in the most intense blizzards.

Given these conditions, there is a “high chance of substantial, long-lasting disruptions to daily life in the higher elevations of the Sierra Nevada Friday through Saturday,” the Weather Prediction Center warned.

Yosemite National Park, which is under a blizzard warning through the weekend, is closed Friday through at least Sunday afternoon, the National Park Service said. Guests are encouraged to leave as soon as possible as the park could see around 8 feet of snow.

Unlike other storms this winter, snow will fall well below pass levels for all impacted ranges. Close to a foot of snow is expected through the weekend for areas as low as 5,000 feet. Several inches are also possible for even lower elevations, including Reno, Nevada. Wind gusts of up to 60 mph will be blowing through the lower elevations alongside snow.

The intense conditions at lower elevations increase the risk of danger on the road.

Travel will be “extremely dangerous to impossible” across the Sierra through the weekend, the weather service warned. Parts of major roadways like I-80 could be shut down for long stretches.

Strong winds will expand well beyond where the snow falls. Gusts in excess of 55 mph are likely for a majority of the West – including the Rockies – through Sunday.

Strong, prolonged winds could bring down trees and power lines, resulting in property damage and power outages.

The heaviest snow and strongest winds from this blockbuster storm are forecast to slowly wind down in California on Sunday.

But another quick burst of less-intense snowy weather could arrive as early as Monday across Northern California.

Storm will provide much-needed boost to critical snowpack

California’s Sierra Nevada snowpack got off to a slow start this winter.

“We’ve definitely been playing a catch up game (with the snowpack in the Sierra),” Edan Lindaman, a senior meteorologist with the National Weather Service in Reno, told CNN.

But recent storms have helped make a difference. Parts of the Sierra are closing in on erasing the snowpack deficit.

The snowpack was at 80% of its March average, a survey conducted by California’s Department of Water Resources found Thursday – which represents what was on the ground before the current storm.

Given the colossal amount of snow forecast to entomb the Sierra through the weekend, there’s a “good chance” to close the snowpack gap or exceed what’s typical, Lindaman said.

The storm currently hitting the Sierra, will be factored into the April snow survey. The April survey is viewed as the most consequential since officials use the measurement to forecast the state’s water resources for the rest of the year. The survey showed snowpack was 70% of the April average.

Millions of people in the West depend on a melting snowpack in the warmer months for hydropower, irrigation and drinking water, according to the US Environmental Protection Agency.