Avalanche Forecast
Regions: Cascades - South East.
As the storm clears out, remnants of a very large, and recent avalanche cycle have been observed. Deep and large avalanches are still possible. Conservative terrain selection will be necessary to stay safe in avalanche country.
Discussion
Snow and Avalanche Discussion
The most dangerous slopes will be at upper elevations where thick slabs may have formed from deeper accumulations and wind. Stay off of steep slopes near and above treeline if finding these slabs. The storm snow is sitting on a thin crust buried on December 20th up to 5,500ft, and low-density old snow above that. This weak interface was inhibiting the bonding between the storm snow and the old snow surface. Carefully evaluate the new snow depth, it’s cohesiveness, and how it is bonding before choosing to travel in avalanche terrain. Use small, inconsequential slopes and tests to check if the storm snow will slide.
You may still be able to trigger Deep Persistent Slabs in the eastern portion of the zone near and above treeline. While these avalanches may be difficult to trigger, they are also very difficult to predict. If you hit the wrong place in the snowpack, it could result in a very large and dangerous avalanche. Large triggers are more likely to initiate a deep slab. Steep, unsupported slopes are the most likely terrain where these can occur.
When the sun comes out, expect small loose avalanches to occur on steep, rocky, sunny slopes. Don’t let them catch you off guard, especially if you are on slopes that could have dangerous consequences.
Below treeline, the avalanche danger may be mitigated due to low snow conditions, but coverage and snow depth has increased over the few weeks.
Check the adjacent zones for more information that may pertain to this area.
Snowpack Discussion
Areas in the East Central zone received from 2†to 7†of snow, with up to 0.7†of water equivalent. Temperatures were initially cold and winds werelight, but strong enough to move snow near and above treeline. Winds were moderate on Mission Ridge, where more snow is likely to have been drifted.
Between the Pacific Crest and the eastern slope there is a large difference between snowpack depths. This is nothing unusual, and more often than not west side of the cascades and the passes get more snow than areas further east. Over time, this adds up. Right now, we are starting to see that difference grow. Â
The persistent weak layer that we have been tracking since December 9th has been observed to be rounding out, gaining strength, and sintering near the pass. Further east in the zone we are still gathering information, but this layer is still in the forefront of our minds in areas with a more shallow snowpack. A very large natural avalanche cycle occurred between December 18th and 20th on these layers in the East Central and East North zones.