Regions
Northwest Inland.
Conditions are improving with cooling temperatures, but the lingering possibility of deep persistent slab avalanches warrants extra caution around big slopes.
Confidence
Moderate - The weather pattern is stable
Weather Forecast
SUNDAY: Cloudy, light southeast winds, alpine temperatures around -10 C.MONDAY: Cloudy, light southeast winds, alpine temperatures around -8 C.TUESDAY: Cloudy with sunny periods, light winds, alpine temperatures around -8 C.
Avalanche Summary
Recent avalanche observations are limited. On Thursday, a size 2 natural wind slab was reported on a northwest treeline aspect. During the warm storm earlier this week, a few small wet slabs were reactive to ski cutting in the Howsons and very large natural and explosive triggered avalanches were reported in northern parts of the region where deep persistent slabs have been more reactive.On Sunday, watch for reactive wind slabs at higher elevations. Also keep in mind that a basal weakness continues to drive a low probability/high consequence deep persistent avalanche problem for the region. Very large avalanches remain possible, especially in shallow snowpack areas.
Snowpack Summary
5-10 cm of recent snow sits above a rain crust and settling storm snow. Strong winds earlier in the week formed deeper deposits in exposed terrain at higher elevations. About 30-60 cm below the surface, you may find surface hoar that was buried on February 10th. There's a fair bit of uncertainty regarding the reactivity and distribution of this layer throughout the region. A stiff mid pack sits above weak sugary snow near the ground. This basal weakness woke up during the last storm and produced numerous large avalanches that released on the ground. The layer has recently been considered dormant but should still be monitored.
Problems
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
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.