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A strong, intensifying storm system continued its trek across the Lower 48 early Wednesday, unleashing high-impact winter weather that could cause widespread power outages and grind travel to a halt. At least 75 million Americans are under winter storm, ice storm, blizzard warnings or winter weather advisories.

In addition to hefty precipitation in much of the Midwest and parts of the Plains, there could also be snow in notably low elevations — including in areas that rarely see measurable snowfall. Even the Los Angeles County mountains are included in a rare blizzard warning — the first issued by the National Weather Service office there since 1989. Snow levels could descend to below 1,000 feet elevation as extreme anomalous cold at high altitudes whips up a serious elevation storm.

That same lobe of frigid air aloft is also spawning a surface low that’s marching across the country. Over the Upper Midwest and the northern Plains, up to two feet of snow could fall in what the National Weather Service office in Minneapolis is calling a historic winter storm. It could prove to be a top-5 event in the Twin Cities, where blizzard warnings slice through the metro.

On the southern fringe of the snowfall, mild air a mile above the ground will favor freezing rain, with a quarter- to a half-inch of ice accumulation, or glaze, possible in some areas. Parts of the Corn Belt and Michigan are expected to be hardest hit, including places like Dubuque and Cedar Rapids, Iowa, or Lansing, Kalamazoo and Ann Arbor in Michigan.

The storm should finish its cross-country assault in the Northeast late Thursday into Friday, where additional winter storm warnings are in effect for northern New York, Vermont, New Hampshire and Maine.

West Coast mountain blizzard

The entire stretch of the Oregon Cascades and the California Sierra Nevada are included in winter storm warnings, with a general 2 to 4 feet of mountain snowfall likely. In the lower elevations and valleys, a frigid rain or mixed precipitation is likely, with damaging winds expected in Southern California.

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One round of mountain snow and strong winds already blew through the Golden State on Tuesday, bringing a gust of 63 mph to Oakland International Airport in the Bay Area.

Hayward, Calif., in the Bay Area, also gusted to 60 mph; Napa County Airport to 47 mph; and San Francisco to 59 mph. San Francisco Airport in San Mateo County reported a 68 mph wind gust. As of Wednesday morning, 109,000 customers had no power, according to poweroutage.us, which tracks outages nationwide.

Now the focus shifts to the new low pivoting down the coast, which was already bringing snow to the Klamath Mountains in Northern California early Wednesday.

Scattered low elevation downpours and high elevation snow showers will probably pinwheel ashore across Oregon and the northern two-thirds of California over the next 24 hours before a more robust layer of moisture heads into Central California early Friday.

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At that point, snow levels should descend to particularly low elevations, perhaps as low as 1,000 feet, with 1 to 4 inches of snow falling between 1,000 and 2,500 feet even in the Los Angeles County Mountains. There are blizzard warnings there and in the Ventura County Mountains, as well. By Saturday night, locations above 4,000 feet may be nearing 3 to 5 feet of snow accumulation with localized seven-foot totals.

“For the Blizzard Warning, heavy snow with winds gusting up to 75 mph and near zero visibility [is expected],” wrote the Weather Service in Los Angeles.

Similar snow totals are likely in the Sierra Nevada with this additional influx of moisture.

In the lower elevations, a cold rain is expected, with as much as 2 to 3 inches along the coast and in valleys. This will be true from Sacramento and Redding, Calif., all the way south to Interstate 15. There’s even a chance that a few snowflakes could sneak down into the San Joaquin Valley on Thursday night; Sacramento hasn’t seen measurable snow since Feb. 5, 1976, when two inches fell.

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Otherwise, wind advisories are in effect for coastal Central and Southern California, with northwesterly gusts of 35 to 55 mph anticipated.

Heavy snow for the Rockies, Midwest and Northeast

Winter storm warnings are posted across virtually the entire intermountain West, with predominantly high-elevation snow expected. Now, however, moisture falling north of a stalled front draped from the Corn Belt to near New York City is coming down as snow.

One band of light-to-moderate snow was working through the Sand Hills of Nebraska and much of South Dakota early Wednesday, with a band of more moderate snow in northeastern Iowa, central Wisconsin and parts of Michigan. A front-end thump of snow was also pushing through Pennsylvania toward New York City, but it should flip to rain by evening.

Snow is expected to continue in South Dakota, northern Iowa, southern and central Minnesota, much of Wisconsin, northern Michigan and parts of central and northern New England late Wednesday, likely increasing in intensity before waning west to east on Thursday.

A general 5 to 7 inches has already fallen across the northern Plains and Upper Midwest, including around the Twin Cities, with another 9 to 14 inches likely on the way. Winds of 35 to 45 mph out of the northwest are expected to loft freshly fallen snow and reduce visibility below a quarter-mile, which is why blizzard warnings are in effect across central and western Minnesota, the James River Valley of South Dakota and southeastern North Dakota.

“Storm totals [should be] close to if not slightly above 20 inches for the event, which would certainly support the historic classification,” wrote the National Weather Service office that serves Minneapolis.

To the east, a general 6 to 12 inches is likely before the snow winds down late Thursday across central and northern Michigan, with similar accumulations likely in parts of the Northeast that stay north of the mixing line.

Significant icing and perilous travel

At the southern edge of the main body of precipitation, warm air from the south at the mid-levels will overrun a shallow lip of cold, dense air near the ground. That moisture-laden warm air a mile up will trigger liquid precipitation — but it will freeze on contact with the subfreezing surface.

Ice storm warnings are in effect north of Interstate 80 in Iowa, as well as for places like Kenosha, Wis., Rockford, Ill., and into parts of Michigan along Interstate 94. A general 0.25 to 0.5 inches of layered ice accumulation is likely.

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