Winter Weather Alerts for 7 States as Lake-Effect Snow to Hit

Winter weather alerts are in place for parts of seven states as lake-effect snow is set to make a return to the Great Lakes region, while the West Coast will experience another atmospheric river storm late in the season.

The National Weather Service (NWS) has issued advisories for California, Idaho, Michigan, Montana, Oregon, Utah and Wyoming. Warnings are also in place for California and Michigan.

In its latest forecast, the NWS office in Marquette, Michigan said a broad area of low pressure was sustaining cold airflow with sub-freezing temperatures of 3-7 degrees Fahrenheit over Lake Superior, promoting lake-effect snow to the west.

Lake-effect snow is a phenomenon in which cold air picks up moisture from relatively warm bodies of water to produce precipitation. In the Great Lakes region, it is usually produced by a Clipper system moving cold air down from Canada.

The region has already seen several bouts of lake-effect snow throughout the winter, with the meteorological effect bringing as much as three feet of snow to the Great Lakes in January.

While snowfall is expected to remain fairly light across much of the region, up to three inches is possible under cloud bands, with possible localized higher totals.

In Michigan’s Keweenaw and Ontonagon counties, up to eight inches of snow is forecast, with the heaviest amounts predicted in higher terrains. Winds are anticipated to reach up to 35 miles an hour.

This is set to worsen for Houghton County, where up to 10 inches of snow is expected and 13 inches in higher terrains, while strong winds may cause areas of blowing snow.

On a national picture, the NWS said that a frontal system moving southwest will bring unsettled weather to the West into Friday, with locally heavy snow possible in mountain ranges. Wintry precipitation will push into the Plains on Friday and reach the Great Lakes by Saturday.

On Friday, a low-pressure system approaching the California coastline will combine with an atmospheric river—a narrow channel in the atmosphere that is able to carry a large amount of moisture—bringing the threat of excessive rain and flash flooding into the weekend.

In the Sierra Nevada mountains of California, up to 10 inches of snow is predicted, with 15 inches expected on the highest peaks. Winds are set to gust as high as 45 miles an hour.

In the Lake Tahoe area, up to a foot of snow is possible above 7,000 feet and up to 18 inches along the crest of the Sierra range.

Snowfall is set to continue into the mountain ranges of southern Oregon, where up to 15 inches of snow is anticipated along with winds as high as 45 miles an hour.

In Utah, up to a foot of snow is expected in the Wasatch Mountains—with snowfall rates reaching an inch an hour on Thursday afternoon—while in western Wyoming up to 14 inches of snow is forecast for the Wind River Mountains, along with winds gusting up to 60 miles an hour.

In Yellowstone National Park, snow accumulations could reach 16 inches.

In the Clearwater Mountains of northern Idaho, up to six inches of snow is expected above 3,000 feet. This will continue into the Sapphire Mountains of western Montana, where up to six inches of snow is also predicted.

Western states have already faced several bouts of snowfall so far this winter, having been subjected to a “prolific series” of atmospheric river storms from the Pacific.

Earlier in the month, a powerful winter storm from the Pacific brought in excess of 12 feet of snow to the Sierra Nevada range, as well as several feet of snow and blizzard conditions to higher-elevation regions of neighboring states.

Another winter storm made landfall earlier the same week before moving into the Intermountain West, bringing intense snowfall from Utah to Wyoming and Colorado.

Atmospheric rivers form when cold air from the Arctic meets warm, moist air from the tropics, cooling it to form heavy precipitation. According to the National Oceanic and Atmospheric Administration, a strong river is able to transport as much as 15 times the amount of water flowing through the mouth of the Mississippi River.

California naturally has an atmospheric river flowing towards it that travels from the subtropics, known colloquially as the Pineapple Express.