Avalanche Forecast
Regions: Cascades - North West.
Dangerous avalanche conditions exist on slopes 35 degrees and steeper at upper elevations. Avalanches and cornice falls could be big enough to bury you where recent snow and wind have drifted fresh slabs and where rain has saturated old snow. Avoid wind drifted pillows, terrain with open cracks in the snow, and overhung cornices near ridge lines.
Detailed Forecast
Expect dangerous avalanche conditions today due recent and snow and wind forming Wind Slabs on leeward slopes near and above treeline. Pay attention to local wind directions and drifting patterns. Avoid drifts or pillowed features where the wind has deposited snow in terrain 35 degrees and steeper. Recent strong winds may have drifted snow into unusual places. Watch for crossloading and Wind Slabs lower on slopes than where they typically form.
Cornice fall and Glide avalanches are possible due to rain and rising temperatures this past weekend. Both could be very large and dangerous. While the likelihood of these avalanches is low, the consequences are severe. Avoid areas with visible glide cracks or where known rock slabs underlie the seasons snowpack. Give yourself an extra wide margin of safety near ridges that could hold cornices, and avoid slopes with cornices overhead. Without more rain, cooling temperatures will put an end to wet avalanche activity by mid-week.
Snowpack Discussion
Mild wet weather changed snow surface conditions in the Mt Baker backcountry over the weekend. Below 5500 feet, 1.3†of rain fell on Sunday during daylight hours creating wet snow surfaces. This fell on 2-3 feet of settled storm snow that accumulated last week.
Low visibility and difficult travel conditions limited observations over the weekend. Observers reported a natural Loose Wet avalanche cycle on all aspects and some cornice fall. A few large natural Wet Slab and Wind Slab avalanches occurred during peak warming and precipitation on Friday.
Observations
Mt Baker Ski Patrol reported rain to 5000 feet Friday and Saturday with a natural loose wet avalanche cycle occurring in the adjacent backcountry terrain. They observed debris from larger slab avalanches on the Shuksan Arm and Mt Herman as well as cornice fall near Table Mountain.
NWAC Forecaster, Dallas Glass, was greeting backcountry travelers at the Heather Meadows trail head on Saturday and reported snow lines wavering between Heather Meadows (4,200ft) and ridge tops. Dallas observed numerous wet loose avalanches in the Bagley Lakes area.
NWAC pro-observer Lee Lazzara traveled in the Canyon Creek area Thursday. Lee found 15-24 inches of recent snow over the 1/29 crust. Wind Slabs were noted in terrain near ridgeline but poor visibility limited observations near treeline.
Avalanche Problems
Wind Slabs
Release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..
Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.
Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1
Glide Cracks
A release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often preceded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
Predicting the release of Glide avalanches is very challenging. Because Glide avalanches only occur on very specific slopes, safe travel relies on identifying and avoiding those slopes. Glide cracks are a significant indicator, as are recent Glide avalanches.
This Glide avalanche broke to the ground on a smooth, grassy slope. From all the mud on the bed surface, water pooling at the base of the snowpack likely caused the failure.
Glide avalanches occur when water lubricates the interface between the snowpack and the ground. These avalanches are difficult to predict and best managed by avoiding terrain below glide cracks.
Elevations: Treeline, Below Treeline.
Likelihood: Possible
Expected Size: 1 - 2