Avalanche Forecast

Several winter storms continue to impact the West-South zone. As of Saturday afternoon, 6-12” of snow has accumulated with the highest totals near Crystal Mountain and Paradise. Crystal Mountain Ski Patrol reported an active avalanche cycle Saturday with natural and skier triggered avalanches over 2 feet deep.

The stormy pattern continues Sunday in the West-South. Even though the models decreased their expected precipitation amounts for Sunday, the combination of warming temperatures and additional precipitation should create very dangerous avalanche conditions. The bulk of the moisture appears to focus on Oregon and the Mt Hood area. The southern volcanoes like Mt St Helens and Mt Adams stand to receive more water than areas farther north. If you are traveling in the southern portion of this zone, be prepared for large natural avalanches to occur in many locations. Areas that receive less snow, should see lower avalanche danger.

Since the weather models are in such poor agreement about the incoming weather, we have a lower level of confidence in this forecast. Resist the urge to step into bigger terrain if you don’t find unstable snow early in the day. The weather could change quickly, and bring with it, rapid changes in the avalanche conditions. Monitor the weather, and recognize how the conditions you’re experiencing differ from the forecast.

Even though the recent weather felt like winter, there are several springtime hazards in the mountains. Creeks, particularly at low elevations, opened wide during the recent warm weather. Glide cracks continue to grow and a few glide avalanches have been found. Holes appeared near many trees and rock. Cornices continue to sag overhead. Use caution when you travel near any of these spring hazards that could be hidden by a few inches of new snow.

Snow bridges over many creeks are beginning to sag, crack, and fail. Choose your creek crossings carefully. Photo: Dallas Glass

April 3rd, 2019

Spring snowmelt

The snowpack in much of the Cascades has changed dramatically in the past two weeks. The weather has shifted solidly to spring-like patterns. The spring warm-up started in mid-March with a prolonged period of relatively clear skies and warm temperatures. Moving into April, we’re seeing periods of unsettled spring weather bringing rain to many low and mid-elevation slopes and snow to upper elevations.

Very bare southeast aspects of Rock Mtn/Nason Ridge. April 2nd. Photo: Josh Hirshberg

Since the peak height of snow in mid to late February, mountain weather stations in the 4,000-5,000ft range show an average of 27% decrease in height of snow. Looking at weather stations in nearly every zone, the percentage decrease ranged from 22-29%. This year's spring snowmelt is much earlier than normal. Traveling in the mountains the loss of snow coverage is most noticeable on southerly, sun-exposed slopes and below 4,000ft. On northerly aspects and slopes above 5,500ft, the snowpack has seen less dramatic changes and has even maintained some dry layers.

NWAC climatological snow depth data from April 1st. You can view it on our website here.

Spring avalanche considerations

As you head into the mountains there are a few questions to ask yourself common to spring avalanche conditions:

1. Is there any recent snow accumulation that could cause avalanches? If so, what kind of avalanches could you trigger? And where?

2. What are the high and low temperatures of the past 24 hours as well as the forecasted temperatures during the time you’ll be in the mountains? Could these create weak, wet snow surfaces?

3. How is the cloud cover contributing to the melting or freezing of surface snow? Did clear skies allow for a sufficient overnight freeze? Will the sun be strong enough to weaken surface layers?

Glide avalanches and holes opening up in rocky terrain near Mount Herman. Photo: Andrew Kiefer

Other considerations

In addition to daily avalanche hazard, the early snowmelt is creating some other travel considerations. Some roads and lower elevation slopes may not have enough continuous snow coverage for travel on snow machines. Holes melted around rocks, trees, and creeks could create a fall hazard. When nighttime temperatures and cloud cover allow for surface freezes, bring appropriate equipment to mitigate slip and fall hazard on steep slopes.

We are approaching the end of our daily avalanche forecasting season. The mountain weather forecast will continue into the spring, and the weather station data is available year round. Keep checking the forecast for conditions updates on the end of season information.