Heat wave creates dangerous avalanche conditions on PNW mountains

PORTLAND, Ore. (KOIN) – Although the sunny weekend weather that’s in the forecast might tempt some backcountry skiers to hit the slopes for a bluebird day, avalanche experts are warning this drastic jump in temperature makes snow likely to slide down. 

The Northwest Avalanche Center issued a special avalanche bulletin Wednesday evening warning people of the dangerous conditions that could exist on Mt. Hood, the Olympic Mountains and the Washington Cascades through Saturday evening. 

Experts say these dangerous conditions are in effect from 6 p.m. Wednesday to 6 p.m. Saturday, but could be extended through Sunday depending on how the weather pattern evolves. 

“The first significant and extended warm-up of the spring will lead to dangerous avalanche conditions. Mountain temperatures will stay well above freezing and freezing and freezing levels will soar to 12,000-14,000’ over the next several days,” the Northwest Avalanche Center wrote. 

In the Willamette Valley, high temperatures will reach 80 degrees in some places Thursday and up to the high-80s on Friday. This is an abrupt jump for a region that’s been experiencing one of its coldest springs on record. 

Currently, the entire state is well above its normal snowpack. The Willamette Valley area on Thursday was at 244% of its median snowpack. 

This means there’s a lot of snow that could melt, triggering an avalanche. The Northwest Avalanche Center said at mid and high elevations, the snowpack has not had time to transition to a more typical and uniform spring snowpack. 

“The likelihood of wet snow avalanches and cornice fall will be elevated over this period. The warm-up will also lead to rapid snow melt at lower elevations, challenging travel conditions, and other non-avalanche hazards,” the center wrote. 

Dallas Glass, deputy director and avalanche forecaster at the Northwest Avalanche Center told KOIN 6 News in mid-April that major weather changes make snow more unpredictable. 

“Any time the weather’s making a really big change you should expect big problems with the snowpack,” Glass said. 

When the temperature goes from below freezing to above freezing, more water is running through the snow, making it more likely for an avalanche to occur. 

Water can really cause problems after several consecutive days where the temperature does not dip below freezing at night. Water will start to melt the ice, pulling and breaking down the layers of snow. Sometimes it occurs on the surface of snow, but other times it’s melting old, weak layers in the middle of the snowpack or on the ground where water can get between the snow and the soil or rocks. 

In situations where that occurs, an entire season’s snowpack can come down in a single avalanche. 

The Northwest Avalanche Center recommends backcountry travelers consider recreating early in the morning during the coolest part of the day. They should also consider their return route and how conditions could change on the way back to the trailhead. 

Anyone who sees new or recent avalanches should avoid similar slopes. Experts say glide and wet slab avalanches are difficult to predict and may occur any time of day. 

“On the volcanoes and higher peaks, very large avalanches can release from higher-elevation terrain and run thousands of feet downhill,” the Northwest Avalanche Center warned in its bulletin. 

Backcountry travelers should also avoid spending time under cornices or steep rocks. Creeks, crevasses and buried rocks or cliff features also become more hazardous as the snowpack weakens and melts.