An avalanche alert was issued for parts of Washington and Oregon, as heavier-than-normal rains and blizzards are expected to hit part of the West Coast by Monday.
The alert was issued on Saturday by the Northwest Avalanche Center, which said at least 30 people in the United States were killed in avalanches this season. This is the highest number of fatalities since the 2015/16 season, according to the center.
The warning, a level 4 on a scale of 5, said there was a high danger of avalanche for parts of North Cascades National Park on the Canadian border, extending south through the Okanogan-Wenatchee National Forest and parts of the Gifford National Forest Pinchot, which is about 140 miles southeast of Seattle.
The alert is in effect until Sunday night and also covers part of Mount Hood National Forest, which is about 70 miles east of Portland, Oregon.
The center’s warning came when parts of the Pacific Northwest prepared for heavier-than-normal precipitation as a result of a “Atmospheric river,” said the National Weather Service on Twitter.
That type of weather event – “a long river of moisture” that can hover over concentrated areas for a period of time – should lead to very heavy rains or, at higher altitudes, heavy snowfalls, meteorologists from the Seattle Meteorological Service said.
The National Oceanic and Atmospheric Administration described these events as “rivers in the sky”. It stretches for about 3,000 miles, from the coast of British Columbia to the coast of Hawaii, said Dustin Guy, a meteorologist at the Meteorological Service.
Although Seattle can see only about half an inch of rain, coastal areas and mountainous regions can wait up to three inches, said another meteorologist from the Meteorological Service, Matthew Cullen. In high-altitude locations, such as the Cascade Mountains, 30 to 60 cm of snow can fall at altitudes above 4,000 feet, he said.
A handful of atmospheric rivers hit the area each season, and this one, so far, should be moderate in terms of precipitation and duration, said Cullen. Still, it is arriving in the region shortly after a particularly heavy snowfall.
A total of about half an inch of snow fell in Seattle in December and January, he said. Then, nearly a foot of snow fell in a three-day period that ended on February 14.
“There was definitely several hours of consistent snow on the order of about an inch an hour,” recalls Cullen.
Americans have seen very recently what low death temperatures can do. A bone-chilling winter storm that covered parts of the southern and central United States last week damaged Texas’s energy supply and left millions without adequate heating and water supplies.
According to the avalanche center, weather conditions on Sunday will make travel on avalanche terrain dangerous.
“Heavy snow, wind and rain will quickly carry the accumulated snow and produce large natural avalanches,” warned Andrew Kiefer, a center official, in a forecast. “Very dangerous conditions will continue until Monday.”
“The avalanche risk is likely to peak on Sunday night,” read the warning. “Large natural avalanches within new snow are likely, especially in areas loaded with wind at higher elevations.”
A snowmobiler in Wyoming and a skier in the interior of Colorado died in separate avalanches on December 18, the first victims of the season, according to the center.
The next day, two skiers from the interior of Colorado died in avalanches. The most recent death occurred near Sherman Peak in Idaho, when a snowmobiler was killed on Saturday.