Avalanche Forecast

Winter-like weather returned to the Olympic Mountains on Monday and new snow avalanche problems are slowly developing after a week of dry and mild weather.

The Olympic Mountains picked up several inches of snow with a weak frontal system on Monday. Cold weather and snow showers should continue Monday night into Tuesday. We expect 3-6" of additional snow, with snow shower intensity heaviest Tuesday afternoon. Plan for dynamic weather if you are out, with rapidly changing conditions and difficult navigation at times above treeline.

You can stay safe and avoid shallow wind slabs by steering clear of steep slopes where you see wind deposited snow. Look for wind-scoured ridgelines or recent very small wind lip features to identify wind-loaded slopes below.  If you think you can trigger a slab avalanche, stick to lower angled terrain, ridgelines or scoured slopes. We don't know whether weak snow existed prior to the storm, but it was widespread on northerly aspects in the Cascades West North zone prior to the storm. Watch for shooting cracks and use small test slopes or column tests on northerly aspects to determine whether the weak grains may persist at the new/old snow interface. Widespread crusts also help to produce more widely propagating avalanches than you expect.

If the sun makes an appearance, change your aspect and seek lower angle slopes if you start seeing rollerball activity to avoid the potential for small loose wet avalanches that could get you into trouble above a terrain trap.

Forecast Schedule - New 3/19/20

The NPS has closed the Hurricane Ridge Visitor Center and road for the winter. As long as the road remains closed to the public, NWAC will maintain No Rating. However, we will continue updating anticipated avalanche conditions and relevant backcountry travel advice daily for the remainder of our season. 

https://www.nps.gov/olym/learn/news/olympic-national-park-is-modifying-operations-to-implement-latest-health-guidance.htm

March 19, 2020 (The regional synopsis is updated every Thursday @ 6 pm)

This week brought a whirlwind of change to our community, the mountains, and the snowpack. It’s mind-boggling to think of how everything changed in just a few short days. Last weekend, a strong winter storm brought frigid temperatures and fluffy powder to many mountain locations. While the calendar read March, conditions felt more like mid-winter. The hands-down winner during this storm was Mission Ridge and the surrounding mountains. As the skies cleared, sunshine and warm temperatures settled into the northwest. Now we’re in the midst of a prolonged spring-like pattern as the snowpack slowly transitions. The biggest change this week may be the impact of the Coronavirus on our community, local mountain operations, and backcountry travel. We continue to work through and adapt to all of these changes in our daily lives as we mark the first official day of spring. Read more about NWAC Operations under Covid-19. 

Wenatchees for the Win

We all know the Wenatchee mountains can receive serious dumps of snow, but this season conditions had been fairly dry. Prior to this past week, Snotel sites and weather stations in the Wenatchees reported only about 65% of average snow depth for the season. A strong low-pressure system began impacting the Pacific Northwest last Friday. However this storm did not follow the usual storm track, it meandered south off the coast, spinning moisture around its center, and sending snow into the Cascades from the SE. When moisture wraps around and approaches our mountains from this direction, it can pack quite a punch along the eastern slopes of the Cascades and in particular the Wenatchees. Early Friday morning, Mission Ridge entered a near 48hr stretch of continuous snowfall. A secondary impact of this low-pressure system was an influx of cold Canadian air which dropped snow levels to near sea level for nearly all locations. The cold air mass combined with the unusual storm track led to substantial accumulations of light fluffy snow; Mission Ridge quickly stacked up over 2ft of very light powder. This new snow and strong winds produced some of the spiciest avalanche conditions for this season in the East Central zone. Numerous natural and human triggered avalanches occurred during and following the storm, including some remotely triggered slides.

Skier triggered avalanche on the Diamond Head in the Wenatchee Mountains. NW, 5200’ 3/14 Photo: Adam Butterfield. 

Other locations in the region only added a few inches to their snow totals for the season. The position of the storm only brought dribs and drabs to the mountains from about Hwy 2 and south. A few standouts further south managed to ring out around a foot (Mt St Helens, White Pass, and Paradise). Strong easterly winds in most areas significantly redistributed the new snow and resulted in reports of numerous natural and human triggered slab avalanches Saturday and Sunday. 

Natural wind slab avalanche on Mt St Helens. W 5500’ 3/14: Photo Nate Berry 

Spring has Sprung

Thursday the 19th ushered in the first official day of spring. All winter, we’ve seen storms creating sometimes unique and occasionally similar snowpacks and avalanche conditions for each of our forecast zones. Following the storm last weekend, a sunny and warm springtime pattern took hold of the region. As it did so, it brought with it a prolonged gradual warm-up and loose wet avalanche cycle. Consequently, differences formerly found in each region slowly resolved as the mountains transitioned into spring. 

A natural loose wet avalanche near Washington Pass, Cutthroat Peak. 3/17. Photo: Gus Goldman

Two items still stand out about this spring transition. 1: the snowpack has not fully moved into a spring-like state. You can still find pronounced cold dry layers and firm icy crust in many areas. 2: We have not seen a spring “shed” cycle yet, where several large natural avalanches occur as the snowpack adjusts to percolating water and warmer temperatures. Forecasting spring shed cycles can be difficult, and it's still unclear when or even if a larger natural wet cycle will occur. 

You can continue to support your community-based avalanche center by submitting observations. 

Stay safe, stay healthy, and thank you for all your support. 

Dallas Glass