Avalanche Forecast
Regions: Cascades - North West.
Avoid avalanche terrain at upper elevations and where slopes are steeper than 30 degrees. Use extra caution if traveling in areas where avalanches may run or stop. Wind slab avalanches may start at upper elevations and run long distances, entraining wet snow at lower elevations while becoming very large and destructive.
Detailed Forecast
Expect dangerous and complex avalanche conditions today due to heavy rain and snow and warming temperatures. Wind slab avalanches above treeline can be very large and can pose serious consequences. Avalanches big enough to bury a car are not out of the question today. The most dangerous slopes are above treeline, where previously dry snow will become either saturated with water for the first time or continuously loaded by wind driven heavy wet snow due to a snowline that oscillates between 5000-6000 feet.Â
Wind Slab avalanches hold today’s gravest consequences. Deep wind slabs may form on a variety of aspects today and will be difficult to manage. Use extra caution when crossing the tracks and runouts of avalanche paths and where you are exposed to overhead avalanche terrain. Wind slab avalanches may start at upper elevations and run long distances, entraining wet snow at lower elevations while becoming very large and destructive.Â
You are most likely to trigger or see Wet Loose avalanches. Many of these slides ran in the past couple days. While these avalanches may be the most predictable of today’s problems, they could still be forceful or large enough to injure or bury you. Avoid traveling through or above terrain such as or cliffs, gullies, or rocky slopes where the consequences of being caught in an avalanche could be increased.
Cornice fall and Glide avalanches have become possible due to rain and rising temperatures. Both could be very large and dangerous. 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.
Snowpack Discussion
Mild wet weather changed snow surface conditions in the Mt Baker backcountry Friday and Saturday. Below 5000 feet, warm temperatures and rain created moist to wet avalanche conditions. This was highlighted by a natural Loose Wet avalanche cycle on all aspects and some cornice fall.
Above 5000 feet, a few large natural Wet Slab and Wind Slab avalanches occurred during peak warming and precipitation Friday. These elevations will receive close to 2 inches of rain on Sunday, and have the potential to produce very large wet avalanches
Across the area 2-3 feet of settled storm snow accumulated over the past week.
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 waivering 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.
Likelihood: Likely
Expected Size: 1 - 2
Loose Wet
Release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Several loose wet avalanches, and lots of pinwheels and roller balls.
Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 1
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind lips of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
Cornices can never be trusted and avoiding them is necessary for safe backcountry travel. Stay well back from ridgeline areas with cornices. They often overhang the ridge edge can be triggered remotely. Avoid areas underneath cornices. Even small Cornice Fall can trigger a larger avalanche and large Cornice Fall can easily crush a human. Periods of significant temperature warm-up are times to be particularly aware.
A corniced ridgeline. A large cornice has formed at the top of the ridge. A smaller cornice has formed to the left of the trees from crossloading.
Cornices are easy to identify and are confined to lee and cross-loaded ridges, sub-ridges, and sharp convexities. They are easiest to trigger during periods of rapid growth (new snow and wind), rapid warming, and during rain-on-snow events. Cornices often catch people by surprise when they break farther back onto flatter areas than expected.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2