New snow and strong winds Friday night will continue to build wind slabs at treeline and above. The new snow may bond poorly to the underlying crust. Watch for sluffing in steep terrain and loose, wet releases on sunny slopes.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
TONIGHT: Mostly cloudy, flurries. Accumulation 5-15 cm. Ridge wind strong to extreme, southwest. Alpine temperature near -5. Freezing level 1200 m.SATURDAY: Mainly cloudy, flurries. Accumulation up to 5 cm. Ridge wind strong easing to moderate, southwest. Alpine temperature near -5. Freezing level 1700 m.SUNDAY: Cloudy, flurries. Accumulation 4-8 cm. Ridge wind light to moderate, southwest. Alpine temperature near -5. Freezing level 1700 m. MONDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind light, east. Alpine temperature near -5. Freezing level 1500 m.
Avalanche Summary
Wednesday there was a report of an icefall-triggered size 1.5 wind slab (50 cm deep and 50 m wide) on a north aspect at 2400 m, as well as small, loose wet sloughs out of steep rocky alpine terrain.On Tuesday a skier intentionally triggered a size 1 wind slab 20 cm in depth on an east facing feature at 2400 m. Explosive control work produced numerous avalanches to size 2.5 in north-facing, lee terrain. On Monday intense wind loading produced natural wind slab avalanches to size 2 on north facing terrain around 2400 m. Solar radiation (direct sun) also produced natural storm slab and loose wet avalanches to size 2.5 on on a variety of aspects between 1700 and 2600 m. We received the following information second hand, and all the details may not be accurate. On Sunday six riders were involved in an avalanche up Doctor Creek. One was stuck, the second went to help and also got stuck, the third rode up the slope to help and triggered an avalanche that buried all three, "up to their faces." The riders credit airbag packs with saving their lives and although one sled was wrecked, the group was able to extricate themselves. The slope was reportedly north facing and failed as a wet slab.
Snowpack Summary
A thin surface crust is now present on all aspects to at least 2000 m. This crust likely goes even higher on south facing aspects, while 5-25 cm of cold snow can be found on high elevation north facing features. There are now a few different crusts within the top 40 cm of the snowpack, with only the mostly recently buried crust posing a concern in wind-loaded areas.There is some lingering concern around the mid-March Persistent Weak Layer (PWL) in the alpine where it is found 40 to 90 cm below the surface. This buried crust/surface hoar interface was widely reactive last week, but has not produced any avalanche activity in the last few days. It is likely trending towards dormancy, but we need to keep it in the back of our minds as it is capable of producing large avalanches should it be triggered (think step-down from a surface avalanche or cornice collapse)Deeper persistent weak layers from December and January are dormant at this time.
Problems
Wind Slabs
Wind Slab avalanches are the 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.
Loose Wet
Loose Wet avalanches are the 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. 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.