Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Jan 3rd, 2019–Jan 4th, 2019

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

.

Heavy rain, snow, and wind will maintain very dangerous avalanche conditions. Avoid all avalanche terrain.

Discussion

Snowpack and Avalanche Discussion

Several natural and triggered avalanches were reported Thursday in the Mt. Baker area. These avalanches failed within new snow breaking 10-12” deep with wide propagation. Avalanches were especially easy to trigger near and above 5000ft where the snow stayed dry. Recent avalanches ran far distances and created large wet debris piles.

Although temperatures are forecast to cool over the next 24 hours, wet avalanches remain a concern especially below 4500ft. Heavy rain like we are experiencing can create glide avalanches - the release of the entire snowpack as a result of gliding over the ground. These hazardous conditions are very difficult to forecast. Avoid steep, lower elevation terrain where smooth ground cover exists.  

The Mt. Baker area received over 3” of water since Wednesday night. This fell as rain up to 4000ft. A mix of rain and 14” of snow fell up to 5000ft. Above, snow totals are significantly greater, but unverified. Up to 3” of additional water is forecast over the next 24 hours. Expect avalanches at all elevations.

Snowpack Discussion

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.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.