Springlike warmth, storms to exacerbate avalanche threat in northwestern US

A persistently warm and rainy weather pattern will contribute to a heightened risk of avalanches and flooding in the Pacific Northwest.

Although the final weekend of January began on a seasonably chilly note, a powerful storm system will direct a river of tropical moisture northward toward the region to round out the weekend and kick off the new week.

"The arrival of mild Pacific air will cause snow levels to rise dramatically, limiting accumulating snow to the highest peaks," AccuWeather Meteorologist Jordan Root said.

Instead, copious amounts of rain are expected to fall in the Olympic Mountains and Washington Cascades, even at and above pass level.

The west-facing slopes of these mountain ranges, where the snow depth has reached several feet, will be at highest risk of flooding and avalanches.

"The risk for avalanches can increase over a particular area due to rapid warming, rain, wet and/or melting snow or high winds," according to AccuWeather Senior Meteorologist Michael Doll.

Doll warned that every one of these conditions will be met through Monday in the Washington Cascades.

Up to 2 or more inches of rain is forecast to inundate portions of the Cascades into early week, where modest warming on Saturday created a heavier layer of snow on top of more powdery snow.

This contrast in weight between the different layers of snow is expected to increase through Monday, significantly heightening the likelihood of avalanches.

According to the Northwest Avalanche Center (NWAC), there is a high risk for avalanches along the western and northern slopes of the Washington Cascades into Monday. Skiers and hikers are warned to avoid all avalanche terrain.

The NWAC also warns any avalanches that do occur may be larger and more destructive than usual and travel abnormally long distances.

Stream and river flooding will also be a major concern, and those living in flood-prone areas should be prepared to seek higher ground in such an event.

The Skokomish River near Potlatch, Washington, remains in minor flood stage and is projected to possibly reach moderate flood stage by Tuesday.

A reprieve from the onslaught of rain and springlike warmth will follow by midweek.

"It will turn colder starting Tuesday with falling snow levels, allowing a return of snow in the Cascades through midweek," Doll said.

Residents planning to engage in outdoor activities in the Cascades should be prepared for rapidly changing conditions.

Another surge of warm air is expected to return by week's end, once again increasing the risk of avalanche occurrence.