Avalanche Forecast

Snow and Avalanche Discussion

Stormy weather continues for Snoqualmie Pass Saturday. This should increase the avalanche danger slowly throughout the day as additional precipitation impacts the area.  The models continue to struggle with the timing and strength of each round of precipitation. The weather pattern Friday night and Saturday doesn’t appear to favor Snoqualmie Pass. As a result, we aren’t expecting significant snow accumulations. Don’t let that lull you to sleep. Monitor conditions and pay attention when the weather you’re experiencing doesn’t line-up with the forecast. If your observations aren’t what you expected, dial back your travel to lower angled slopes.

Additional rounds of precipitation and potentially warming temperatures are expected Saturday night and Sunday. As the snow begins to pile up and the snow levels fluctuate, we could be looking at very dangerous avalanche conditions this weekend.

Over the past few weeks creeks opened, glide cracks grew, and cliffs shed their snow. This won’t stop just because the temperatures cool a bit. Continue to use caution if you travel around these spring transition features. The water needs time to drain from the snowpack. At the lower elevations, you may still find wet heavy snow. In these locations, loose wet avalanches aren’t out of the question. Avoid steep slopes greater than 35 degrees if you find wet punchy unfrozen snow.

Snow bridges across creeks collapsed during the recent warm weather. 04/05/19 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.