Warm temperatures and freezing levels to 3,500m will increase the avalanche danger at all elevations.
Weather Forecast
Thursdays freezing levels are forecasted to spike to 3,500m with alpine highs of +5 C. The effect of the temperature on the snowpack and rock faces will be increased with direct solar radiation. The avalanche danger is expected to increase as this occurs. Ridge wind NW10-20 km/h. Cooling will take place on Friday and Saturday.
Snowpack Summary
The snowpack is well settled. Wind slabs are in exposed lee features at and above treeline. A significant crust (Nov.23) can be found down 30 to 70cms. A persistent slab overlays this crust and so far the bond appears to be strengthening at this interface. The Halloween crust sits well down in the snowpack at TL locations and as high as 2700m.
Avalanche Summary
No new avalanches have been observed or reported on Wednesday. The high freezing levels on Thur is expected to wake up the weaknesses within the snowpack. Small snowballs and sections of falling cornice may trigger deeper instabilities producing large avalanches. Solar facing avalanche terrain should be avoided at treeline and above.
Confidence
The weather pattern is stable on Thursday
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.