Persistent weaknesses deeper in the snowpack remain the primary concern, especially in steep and rocky alpine features with a shallow or variable snowpack.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
SUNDAY: Mix of sun and cloud, light southeasterly winds, and treeline temperatures around -15. MONDAY: Cloudy with light snowfall bringing another 5-10 cm of new snow, moderate to strong southwesterly ridgetop winds, and treeline temperatures around -18. TUESDAY: Mix of sun and cloud, light northwesterly winds, and treeline temperatures around -20.
Avalanche Summary
On Friday, no new avalanches were reported in this region.
Snowpack Summary
10-15 cm of recent snow and light winds have created thin wind slabs in exposed terrain at treeline and above. This recent snow has also covered old, thicker wind and hard slabs from previous wind events. Persistent and deep persistent weakness in the mid and lower snowpack are giving variable results in snowpack tests, but are generally most touchy in shallow snowpack areas. Recent snowpack tests gave moderate but resistant results on facets and/or surface hoar buried mid-December where it was found down 45 cm, and hard but sudden collapse results on the facet/crust weakness down 116 cm near the base of the snowpack.
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.