Avalanche Forecast

Warming temperatures, light rain, and snow have brought changes to the snowpack but not enough to dramatically change today's avalanche danger. With very warm temperatures, you can trigger Loose Wet avalanches at all elevations. Several old weak layers of snow have been reported in the snowpack over the last several weeks. You are most likely to trigger a persistent slab on shaded aspects near and above treeline. While snow profiles and snowpack tests can demonstrate the presence of a persistent weak layer they cannot prove its absence. The best way to avoid triggering a persistent slab avalanche is to stay off of large steep opens slopes in locations where persistent slabs are thought to occur.

In some locations near the Cascade crest you may find small shallow wind slabs. If you see more than 6 inches of soft snow on the ground, expect wind slabs in nearby terrain. Use visual clues such as blowing snow, new cornices, and snow drifts to identify and avoid wind loaded slopes.

A lower elevations rain fell, melting what little snow is still there. Expect new rollerballs, pinwheels, and small loose wet avalanches if you experience rain while traveling. If you experience areas of wet, unsupportive snow, avoid slopes over 35 degrees.

Around 2-4 inches (5-10cm) of new snow has fallen around the eastern zones in the Cascades. Locally higher snow totals may be found, particularly close to the Cascade crest. An observation on NWAC’s public observation page reported 6 inches (15cm) near Washington Pass. The new snow fell on a variety of snow surfaces including melt-freeze crusts, thin rain crusts, old wind textured snow, and settled soft snow.

Older layers of weak snow can be found in the snowpack. We have very limited information about the distribution and reactivity of these layers leading to a higher level of uncertainty. If you have any information or observations on layers within the snowpack please consider submitting them to NWAC via our public observations page. The exact weak layer and depth depends on your location. Several common weak layers are:

• 3/25: Buried surface hoar layer found on shaded aspects near and above treeline.
• 3/22: Buried surface hoar layer found on shaded aspects near and above treeline.
• 2/13 Facets above a firm and thick melt-freeze crust can be found in many locations near and above treeline. This layer is thought to be dormant at this time but may re-awaken with a substantial weather input.

Other weak snowpacks may be found in locations further east of the Cascade crest or in areas where shallow snow exists.  

Observations

North

On 3/23, professionals near Washington Pass reported the 3/8 buried surface hoar was reported as 1.5 feet (45cm) below the snow surface.

Central

On Saturday 3/31, an observer reported a large slab avalanche that likely failed on a persistent weak layer 4-5 feet below the surface in the Enchantment Mountians

On Friday 3/30, Matt Promomo was on Dirtyface Mountain where he found two buried surface hoar layers (3/22) on shaded aspects at variable depths within the two feet of the snowpack. Test results indicated the potential for propagation on both weak layers. Snow pits indicate a weakening 2/8 crust.