Avalanche Forecast

Snow and Avalanche Discussion

Loose Wet Avalanches may be triggered in isolated areas where the snow surfaces soften. We expect a strong overnight refreeze with gradually increasing clouds during the morning hours on Monday. The refreeze and cloud cover should both help limit avalanche danger. However, if the overnight refreeze is weak and/or the morning sunshine is strong, check for surface penetration greater than 6” as a sign that loose wet avalanches are a hazard in your terrain. Be especially cognizant of the consequences of even a small avalanche around terrain traps like gullies or cliff bands.

Markedly cooler weather over the weekend created generally firm snow surfaces Saturday and Sunday, which softened 1-2” during the afternoon hours each day. On Saturday, NPS rangers saw evidence of a widespread small wet loose cycle that occurred early last week during a week of extremely warm March temperatures. Dry snow is believed to remain on NW through NE aspects, while a week of extreme March temperatures has transitioned the surface snow on other aspects.

On Sunday, a NPS ranger did not identify layers of concern, including the previously mentioned buried surface hoar layer (3/7), in snow pits on S and NE aspects around 5000 ft. In general, the upper meter of the snowpack appeared to be refreezing.

Keep your eyes open, and look for observations that seem out of place. It's these unique areas where you could find a lingering avalanche concern.

The mountains are still experiencing their spring transition. As a result, you may find a wide variety of snow surfaces Monday including breakable crust, firm icy surfaces, and wet heavy snow. During this transition remember to keep a lookout for potential springtime hazards such as opening creeks and glide cracks. Use caution if you travel near these features.

Forecast schedule

For the 2018-19 winter season, avalanche danger ratings will be issued for the Olympics every Friday through Sunday and during mid-week holidays.

During the week, No Rating will be issued but forecasts will include expected conditions and relevant travel advice. While this avalanche forecast is focused on backcountry avalanche conditions expected in the Hurricane Ridge area, we want to hear about your observations from other parts of the Olympics as well.

March 22nd, 2019

Enter Spring

If you’ve been in the snow recently, the wintery conditions of early March may seem worlds away. You may be in for a surprise if it’s been a while since you were in the mountains. The weather has taken a turn towards spring in the last couple weeks and the Cascade snowpack the has undergone major changes. Unseasonably warm temperatures and strong sun followed a month-and-a-half of cold, winter storms. Mid-elevation weather stations stayed above freezing from March 15th-22nd with high temperatures reaching the upper 50’s to low 60’s. For an in-depth survey of the regional snowpack, we’ll divide the terrain up by aspect and elevation.

A graph showing temperatures between 4,000-5,000ft around the Cascades from the 16th-21st.

Aspects

Northerlies

Along with the warm temperatures, the spring sun has played a major role in warming snow surfaces. The result is a snowpack that varies by aspect. In most regions, shaded and northerly slopes remain relatively unchanged. Aside from some settlement and firmer or moist surfaces, the snow on north aspects is almost entirely dry. Even some low elevation north slopes are still holding snow.

Sunny slopes

The snowpack on east through south through west aspects is a different story. The strong March sun melted snow surfaces and drove melt-water into the snowpack. This is most dramatic on steep (over 35 degrees) southeast through southwest slopes below 5,000ft.  In some areas, you can find meltwater up to 3 feet below the snow surface with drainage channels well established. Between this warm period and rain events in the first half of the winter, the entire snowpack has transformed to melt forms. An important point to note is that as of the 22nd, these solar aspects remain unfrozen and weak. Cooler weather ahead may help strengthen moist to wet layers.

A glide avalanche (D2) released from a rock slab late on the 20th. Lichtenberg Mtn, 5,100ft, SE aspect. Other glide avalanches occurred on the 20th at Snoqualmie Pass and in Tumwater Canyon. Photo: Josh Hirshberg

Elevation

Low elevations

As you travel from low valleys to higher peaks, you’ll notice a major difference in the snowpack based on elevation. With all the low-elevation snow this winter, there are still some cold, shaded slopes holding pockets of snow down to 1,000ft, especially east of the Cascade Crest. However, most slopes below 3,000ft have lost much of their snow cover. Many low elevation, sun-exposed slopes are bare, especially in areas that previously held less than 3 feet of snow. The low elevation snowpack is no longer substantial enough to allow for easy travel over snow or widespread avalanches.

Loose wet avalanches on the south side of Table Mtn, near Mt Baker. 3/17. Photo: Pete Durr

Mid-elevations

At mid-elevations, around 3,000-5,000ft, the snowpack is still deep and layered. Many slopes at this elevation band near and west of the Cascade Crest are holding 6-10 feet of snow. This is also where you’ll find the most dramatic variation in the snowpack based on aspect.

High-elevations

Above 5,000ft you’ll encounter a snowpack similar to what you may have found around the 1st of March. Upper elevations have stayed mostly dry. The most sun-exposed slopes have surface crusts but have not seen much water or change to melt forms below the surface.