Avalanche Forecast
Jan 9th, 2019–Jan 10th, 2019
Alpine
3:
Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2:
Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2:
Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3:
Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2:
Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2:
Moderate
The avalanche danger rating below treeline will be moderate
Regions: Cascades - East.
The Bottom Line: Even though the avalanche danger is slowly dropping you will still need to be heads-up Thursday. You may trigger avalanches in areas where the wind has formed firm slabs or in locations where weak old snow layers exist. You can stay safe by avoiding slopes greater than 35 degrees.
Snowpack and Avalanche Discussion
We have quite a bit of uncertainty around the weather forecast for the next 24 hrs. Weather models are struggling to determine freezing levels and precipitation amounts. This will add another layer of variability to an already variable snowpack in the East-Central zone. When conditions like this exist, it’s a good time to be heads-up. Is what you are seeing inline with the avalanche forecast? If not, stop and reevaluate. In general areas closure to the Cascade crest may exhibit features closer to snowpacks of Stevens and Snoqualmie Passes. Further east a much weaker and more complex snowpack exists.
Avalanche Problems
Wind Slabs
You will need to use your eyes and sense of touch to locate wind transported snow as you travel. Look for signs like blowing snow, fresh cornices, and the snow blown out of trees. Feel the snow under you as you travel. Does it feel more firm in one location than another? Does it feel hollow? If you see or feel any of these observations, wind slabs may be nearby. Recent winds formed slabs in some unusual locations like well below ridgelines, on the sides of gullies, and in places that are normally scoured. You can stay safe by traveling on ridges, scoured areas, and any slope less than 35 degrees.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 2 - 2
Persistent Slabs
This snow and wind loading event has stressed older weak layers in some locations. We don’t know yet how these persistent layers responded to the new load. What we do know is we have a weak snowpack structure in some locations and we just put more snow on top of it. Persistent slabs can be difficult to assess and predict. If you see any obvious signs of avalanche danger like recent avalanches, cracks in the snow, or feel sudden collapses, stay away from all slopes greater than 30 degrees.
There are two primary layers of concern in the snowpack. You may encoutner one or both depending on where you travel. You are most like to encounter persistent slab at higher elevations and in areas towards the eastern edge of the forecast zone.
A layer of buried surface hoar may be found 1-2 ft below the snow surface. This layer is mainly a concern above 6000ft.
A layer of weak sugar facets can be found near the ground, particularly in the eastern areas of the forecast zone. If an avalanche failed on this layer, it might be more than 4 feet deep. Use caution if you are traveling in areas where the snowpack is thinner.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 3 - 3