More snow and more wind have created windslabs in the alpine. Approach larger slopes with caution. We are approaching the upper end of Considerable for avalanche hazard.
Confidence
Moderate - Due to the number and quality of field observations
Weather Forecast
Another 10cm of snow has fallen since Wednesday which brings our storm snow up to about 50cm. Thursday night is forecast to bring another 5-10cm of snow. Friday is to bring light flurries with alpine winds of 30km/hr SW winds with gusts up to 50km/hr. Temperatures for Friday in the alpine will be around -12c. If Friday brings more snow than forecasted, the avalanche hazard could easily tip towards a HIGH hazard. The outlook for the weekend is for a drier airmass with cooler temperatures.
Avalanche Summary
4 new avalanches were observed on Wednesday Dec.19: -Two size 1.5 and one size 2 avalanches East aspect in the alpine near the Tent Ridge zone.-One size 2 avalanche East aspect in the alpine was observed between Black Prince and Hero's knob-Keep in mind that human triggering is still likely.
Snowpack Summary
Another 10cm of snow that fell Tuesday night brings our storm snow up to 50cm. Lee features are much more loaded (up to 90cm of storm snow). These loaded lee features are a good indication of the recent wind transport; it will be important to look for windslabs before venturing into bigger terrain. Below this storm snow are surface hoar and facet crystals which are creating a weak sliding surface for the snow to be reactive; we are calling this the December facet layer interface and it is producing natural avalanches. There is still concern for this recent storm snow to trigger the October facet layer at the bottom of the snowpack.
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.
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.