Archived

Avalanche Forecast

Jan 14th, 2019–Jan 15th, 2019

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Cascades - East.

The Bottom Line: Expect one more day of warm temperatures. Use caution on steep, sunny slopes if you see rollerballs or find wet snow on the surface. Loose wet avalanches can be dangerous if they push you into trees, rocks, or off of cliffs. There is still an isolated chance of triggering a deeper slab on older weak layers.

Snow and Avalanche Discussion

There is a lot of variability of snowpack structure within the zone. The current snow surface is a mixed bag. On sunny aspects, it is likely crusted over, softening as the day warms. The snow has been remaining cold and dry above 5,000ft on shaded aspects, and small surface hoar growth has been observed. The storm snow from January 8th and 9th sits over a crust from January 3rd. A thin layer of weaker snow has been found just above this crust, and is worth checking out how these are bonding. A round of control at Mission Ridge on the 10th pulled out a number of large avalanches in wind loaded terrain. One of these on a Northwest aspect at 6300ft broke through the crust and ran on weaker snow near the ground, exposing rocks. On steep southerly aspects, a number of loose wet avalanches have been observed.

Avalanche Problems

Loose Wet

The concern for wet loose avalanches is being maintained by warm temperatures Monday night and sun in the first half of Tuesday. Otherwise, these avalanches have mostly run their course. You could still encounter them on steep slopes that face the sun. On Tuesday, southeasterly aspects may be the most avalanche prone. A project a cooling trend and building clouds should limit avalanches by the afternoon.

If you see roller balls, notice the surface crust is melting and becoming wet and heavy, or see small loose slides that begin entraining snow on any aspect, use caution on steep slopes and near terrain traps. You can find these avalanches around gullies, cliffs, and rocky slopes. These features can increase the consequences of an avalanche.

Aspects: South East, South, South West.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 1

Persistent Slabs

Deeper avalanches in old snow have become less and less likely. However, the consequences are still high. Obvious clues to danger like shooting cracks and whumphs probably won’t be observed, although a weak snowpack structure still exists in some locations. Recent wind loading at upper elevations, warm temperatures, strong sun, and potential melt-water in the snowpack all raise uncertainty about the likelihood of triggering a persistent slab. An avalanches in these deeper weak layers would be very large and surprising. You can minimize your risk by using lower angle, and well supported slopes, and staying out of extreme terrain. Shallow, shaded, and rocky slopes are also good places to avoid.

Two primary layers of concern in the snowpack are:

A layer of buried surface hoar found 1-3 ft below the snow surface. This is mainly a concern above 6000ft. Be suspicious of this layer the higher you go. Documented avalanches have been on North through Southeast aspects. Snowpack tests continue to reveal sudden results in some areas on this layer.

A layer of weak, sugary facets can be found near the ground in the Wenatchee Mountains, and other areas on the eastern edge of the forecast zone. If an avalanche failed on this layer, it could be more than 4 feet deep. Use caution if you are traveling in areas where the snowpack is thinner, and where any stiff snow overlies weak snow.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely

Expected Size: 3 - 3