Avalanche Forecast

Issued: Feb 4th, 2018 11:11AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Glide Cracks and Loose Wet.

Northwest Avalanche Center NWAC, Northwest Avalanche Center

Heightened avalanche conditions exist on slopes steeper than 35. Large and destructive Glide avalanches and cornice falls are possible where rain has saturated old snow. Avoid terrain with open cracks in the snow and overhung cornices near ridge lines.

Summary

Detailed Forecast

While avalanches will be difficult to trigger today, they could have serious consequences. Glide Avalanches and cornice falls could be big enough to bury or kill you.  Both of these types of avalanches form in specific types of terrain. The best way to stay safe is to avoid areas where these avalanches form and release. Watch out for slopes with visible glide cracks or where known rock slabs lie under the snowpack. Give yourself an extra wide margin of safety near ridges that could hold cornices, and avoid slopes with cornices overhead.

Many Loose Wet avalanches ran in the past couple days. This avalanche cycle is tapering off but is still possible today. While these avalanches may be the smallest and most predictable of today’s avalanche flavors, they could still be big enough to injure you. Avoid traveling through or above terrain that could increase the consequences of being caught in an avalanches such as or cliffs, gullies, or rocky slopes.

Snowpack Discussion

Wet weather over the weekend created moist to wet surface snow conditions up to 6500 feet. A natural Loose Wet avalanche cycle occurred Friday and Saturday. Observers reported both natural cornice falls and glide avalanches. We’ve received minimal reports of Wet Slab avalanches. Poor visibility and stormy conditions have limited observations at higher elevations. Across the region rain totals averaged 1” during daylight hours on Sunday with 1.06” at Steven’s Pass, .95” at Snoqualmie Pass, and .88” at Paradise on Mt Rainier.

Observations

Stevens Pass

NWAC Avalanche Forecasters and observers noted numerous natural wet loose avalanches on all aspects Friday and Saturday. These avalanches ranged from small to large, with some travelling 1000 vertical feet.

Snoqualmie Pass

On Sunday NWAC observer, Matt Schonwald, found a saturated snowpack with rain water more than 2 feet below the snow surface. Alpental Ski Patrol reported audible cornices collapses along ridges in the Alpental Valley on Saturday. Both patrol and NWAC observers reported Glide avalanches, visible glide cracks, and many wet loose avalanches

South

Crystal Mountain Ski Patrol reported skier triggered wet loose avalanches in terrain with an uncompacted, backcountry-like snow on Saturday.

Problems

Glide Cracks

An icon showing Glide Cracks

A release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often preceded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.

 

Predicting the release of Glide avalanches is very challenging. Because Glide avalanches only occur on very specific slopes, safe travel relies on identifying and avoiding those slopes. Glide cracks are a significant indicator, as are recent Glide avalanches.

 

This Glide avalanche broke to the ground on a smooth, grassy slope. From all the mud on the bed surface, water pooling at the base of the snowpack likely caused the failure.

Glide avalanches occur when water lubricates the interface between the snowpack and the ground. These avalanches are difficult to predict and best managed by avoiding terrain below glide cracks.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

An icon showing Loose Wet

Release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

 

Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.

 

Several loose wet avalanches, and lots of pinwheels and roller balls.

Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 1

Valid until: Feb 5th, 2018 11:11AM