Manage alpine wind slabs by paying attention to how the snow feels underneath your skis/track, and backing off where it feels stiff. Increase your caution at and below treeline, buried surface hoar has been especially touchy between 1400 & 1800 m.
Weather Forecast
High pressure, cold temperatures and clear skies should allow for great visibility Monday and Tuesday. Cloud cover starts to build back in Wednesday, but the models are not showing any significant precipitation until Friday.SUNDAY NIGHT: Freezing at valley bottom, light to moderate north/northwest wind, trace of snow possible.MONDAY: Clear skies at dawn with a bit of cloud building in the afternoon, freezing level at valley bottom, light northerly wind, no precipitation expected.TUESDAY: Clear skies, freezing level at valley bottom, light variable wind, no precipitation expected.WEDNESDAY: Broken cloud cover, freezing level at valley bottom, light west/northwest wind, trace of precipitation possible.
Avalanche Summary
Over the last five days storm and persistent slab avalanches averaging size 2 have released naturally and been human triggered on the mid-January surface hoar which is 25 to 50 cm below the surface. The majority of these avalanches occurred at treeline and below, however, there have been a few noted at higher elevations in the alpine. On Saturday wet loose avalanches to size 2 were reported on south facing aspects between 1800 and 2500 m during the heat of the daytime warming. Wind slab avalanches to size 2 were also reported on a variety of aspects between 1700 and 2700 m.There were a few reports of remote triggering Friday on north, northwest and east facing slopes. One was triggered from a flat ridge 30 m away from the avalanche which ran on a moderately inclined north facing slope at 1900 m producing a size 2.5 avalanche.
Snowpack Summary
Saturday delivered warmth and strong to extreme wind out of the west, south, southwest and northwest. This left a crust on steep south facing aspects and likely redistributed quite a bit of snow into fresh and potentially deep wind slabs in lee alpine features. The warmth also allowed 25 to 50 cm of snow to continue to consolidate above the mid-January persistent weak layer (PWL). This PWL is made up of large surface hoar that is most prevalent at and below treeline, with enhanced reactivity noted between 1400 and 1800 m. On steep solar aspects this interface presents as a crust, there may be locations where the surface hoar actually sits on the crust.The middle and lower portions of the snowpack are generally well-settled and strong.
Problems
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.
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.