Avalanche Forecast

Spring weather and snowpacks can be tricky. General rules-of-thumb used during the winter often do not apply. With the amount of recent new snow and more on the way, this is a good time to be cautious. Avoid all slopes greater than 35 degrees and limit your exposure to large overhead avalanche terrain.

You will be able to trigger large wind slab avalanches Saturday on steep wind loaded slopes near and above treeline. Use visual clues such as blowing snow, new drifts, or fresh cornices to identify and avoid wind loaded features.

Fluctuating temperatures during the storm created an “up-side-down” snowpack with heavier strong snow over lighter weaker snow. This is a classic strong over weak slab avalanche scenario. You are likely to find this snowpack structure in all sheltered avalanche startzones above the rain line. Storm slabs will be easiest to trigger in the morning as strong overnight precipitation tapers off. Storm slabs may extend into the upper below treeline zone depending on air temperatures and precipitation type.

At lower elevations, expect wet surface snow conditions. New rollerballs, fresh fan shaped avalanche debris, and rain on snow are all key signs that loose wet avalanches are likely. Some loose wet avalanches this week have entrained large amounts of old wet snow and traveled father than normal.

Other spring time avalanche hazards exists. Glide cracks have formed on some slopes. Glide avalanches are difficult to predict and can release at any time. Limit your exposure to any slope with glide cracks. Creeks are beginning to open up at lower elevations. Choose your travel routes wisely if you are planning to over larger creeks

Over a foot (30cm) of new snow has fallen as of Friday afternoon with more on the way overnight. Moderate to strong winds during the storm transported snow forming wind slabs near and above treeline. This new snow is falling on a melt-freeze crust formed and buried on 4/11. The strength and thickness of this crust is largely dependent on elevation.

Mild weather earlier this week allowed the upper snowpack to gain strength. Observations show the snowpack is comprised of several melt-freeze crusts, refrozen snow, and strong rounded grains. This has created a strong spring-like snowpack. Avalanches should be limited to the snow above the most recent (4/11) crust layer.

Observations

North

On Friday Mt Baker Ski Patrol reported wind slabs up to 16” (40cm) deep near treeline.  Loose wet avalanches were observed below 4500 feet despite lower snow levels.

NWAC professional observer Lee Lazzara traveled in the Baker backcountry Thursday. Lee found 8 inches (20cm) of new snow well bonded to the old snow surface. While Lee did see wind slabs, no wind slab activity was reported. Warming air temperatures and thin clouds resulted in several small (D1) loose wet avalanches in the afternoon.

Stevens

NWAC forecaster Dallas Glass traveled in the Stevens Pass area Wednesday. Dallas found the upper 5 feet (1.5m) of the snowpack to be generally strong. He did not find any significant layers of concern below the wet surface snow.