Avalanche Forecast
Jan 3rd, 2019–Jan 4th, 2019
Alpine
3:
Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3:
Considerable
The avalanche danger rating at treeline will be considerable
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
3:
Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2:
Moderate
The avalanche danger rating below treeline will be moderate
Regions: Cascades - West.
The Bottom Line: Dangerous avalanche conditions exist. Give the snowpack time to adjust. Avoid steep slopes at mid and upper elevations where the wind is drifting thick slabs.
Regional Synopsis
Happy New Year!
Thanks to all of you who volunteer, send observations, and support NWAC in various ways - we appreciate it.
December of 2018 was fun (from a forecasting perspective) with three pronounced avalanche cycles, a couple different persistent weak layers, some rain events, and a flurry of human-triggered avalanches to ring in the New Year. Most importantly, it seems that we made it through the last days of 2018 without anyone getting seriously hurt by an avalanche.
The deep (Dec 9) layer responsible for many of the avalanches early in the month no longer seems to be a problem in the western zones. That said, it is still possible to trigger an avalanche on its counterpart (or basal facets) in the eastern areas.
A widespread layer of surface hoar formed around Christmas. Late December storms preserved this layer in areas above the rain line and we have numerous (more than a dozen) reports of people triggering avalanches on it in the last three days. At least 4 people were caught and carried during this period, but so far we have no reports of serious injury. Most of these avalanches were soft slabs, D1-D2+, but there were several harder wind slabs in the mix.
It appears that the layer is most reactive and/or prevalent in the Crystal Mountain backcountry and in the mountains around Leavenworth and west of Mazama.
Surface Hoar can be an especially tricky and persistent weak layer. Read more about it here.
Avalanche Problems
Wind Slabs
Strong winds are redistributing snow and building fresh wind slabs. Triggering an avalanche is likely within wind-drifted snow at upper elevations. These avalanches could easily bury you and run far distances to lower elevations. If you trigger a wind slab, it may step down to deeper layers resulting in a very large avalanche. Use caution in leeward areas. Avoid travel near and below steep wind-loaded terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 2 - 2
Persistent Slabs
New snow and wind are stressing a layer of feathery surface hoar that formed around Christmas. Observations from neighboring areas indicate the surface hoar has a spotty distribution and can be hard to find. Regardless, impressive and unusual recent avalanches still have us concerned. This layer can be found in the upper snowpack between 4500-5500ft primarily on north and east aspects. Carefully evaluate the snowpack before committing to avalanche terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 3 - 3