(CNN) — More than 10 million people in at least nine western states are under a winter watch, including cities like Seattle and Salt Lake City, as a winter storm sweeps through the region.
The storm will bring up to 30 inches of snow to the drought-stricken Sierras but will make travel “difficult or impossible.”
“Back-to-back winter storms will bring periods of very difficult to impossible travel over the Sierra passes through Sunday,” said the National Weather Service (NWS) office in Reno..
The snow and rain should begin to abate Friday for most areas before the next storm system enters late Saturday/early Sunday.
Snow rates could reach 2 to 3 inches per hour Thursday and early Friday. This, combined with high winds, could lead to near zero visibility conditions.
The beginning of the winter season
“Today is the first day of meteorological winter, and it feels like it in the Pacific Northwest,” the NWS Portland office said.
While nearly 1 meter of snow could fall in California, in the Rockies expect 12 to 24 inches of widespread snow in places like Montana, Utah and the Colorado mountains. Heavy rainfall along the coast could exceed 100mm.
For cities like Seattle and Portland a mix of rain and snow is expected. Although this will limit the amount of snow that accumulates on the ground, it will still cause travel problems thanks to muddy roads, and sub-zero temperatures will create patches of black ice.
For the city of Seattle, only 1 to 2 inches of snow is expected through Saturday, with a winter weather advisory through Friday night. This would be significant snow and quite rare for Seattle, a city that gets as average snow per year (9 cm) as Little Rock, Arkansas. In fact, Seattle could record more than half of its annual snowfall from this early winter storm.
A winter weather advisory has also been issued for Billings and Missoula, Montana, where snowfall is forecast to be between 2.5 to 7 cm and 7 to 15 cm, respectively.
For Reno, Nevada, elevation is everything. In the city itself and along the slopes, 2.4 to 10 cm are expected, but once you exceed 5,000 feet in altitude, the forecast becomes 7 to 17 cm.
Salt Lake City will also record a few inches of snow in the city, where 2 to 4 inches are forecast. However, in the mountains, including Park City, the totals will be closer to 12 inches.
In Aspen, Colorado, which is also under an avalanche watch through Saturday morning, skiers can expect 5 to 10 inches.
Back-to-back winter storms will bring periods of very difficult to impossible travel over Sierra passes through Sunday. See our Winter Storm Warnings for additional info: https://t.co/Hlck0YYqz8. Check with Caltrans for up-to-date road info: https://t.co/rYQgfWT4N2. #cawx pic.twitter.com/E2egHY3G8Q
—NWS Reno (@NWSReno) November 30, 2022
The largest amounts of snow will fall along the Sierra range, where 20 to 30 inches are forecast at places like Mammoth Mountain and Mount Shasta.
That’s why the NWS Reno office urges people to avoid all non-essential travel during high-impact periods.
A fast start to the snow season, with a long way to go
Although it can cause a lot of displacement problems, all that snow is good for one thing: helping with the drought. But one blizzard doesn’t mean the whole season will be the same.
Last year, California had its wettest start to the year in more than 40 years. However, precipitation quickly plateaued and the season’s snow cover was only 35% of what would normally be expected.
Regarding snowpack conditions in the region at this time, the Natural Resources Conservation Service SNOTEL network is currently reporting the following snowwater equivalent percentages to the region in the most recent update (November 29) :
Pacific Northwest 134%
Great Basin 157%
Lower Colorado 152%
Upper Colorado 98%
While these numbers are off to a great start, they need to stay that way to have a major impact on the drought conditions, and in turn the water supply, that have been plaguing the West for decades.
CNN’s Rob Shackelford contributed to this report.