Solar input will be a significant factor on Wednesday leading to a rapid destabilization of the snowpack on solar aspects. A good day to start early and finish early. Non-solar aspects have also had some large skier and naturally triggered avalanches in the past 24 hours. Check out this MIN for photos of the skier-triggered slide in Miner's Gully,
There are two layers of concern here: 1) a buried sun crust (on solar) and facets (on polar) down 20-40cm, and 2) a facet/depth hoar layer down 80-100cm that was buried mid season. These layers have become more active within the recent additional snow load, and are more prone to triggering during periods of intense solar radiation.
The surface snow will quickly loose strength with the forecasted sunny skies and warmer temps on Wednesday. Limit exposure to solar slopes and be mindful of overhead terrain.
Thin, shallow areas or heavy triggers are what will set this layer off. Avoid terrain with those characteristics. Intense solar radiation and daytime heating may wake up this layer.
A skier triggered size 2.5 slab avalanche occurred in Miner's Gully sometime Tuesday morning. Parts of the avalanche look to have steeped to ground. It is unknown if skiers were taken down with the slide, or if they remained on top, but it appeared to be a fairly major close call. This avalanche occurred on an East aspect at 2300m.
A size 3 naturally triggered deep persistent slab occurred in the past 24 hours on a North aspect at 2700m in the Goat Range. This avalanche exhibited wide propagation.
A size 3 naturally triggered deep persistent slab occurred sometime in the last few days in the Pocaterra Ridge area. This avalanche had impressively wide propagation.
Recent storm snow of approximately 25cm of settled snow remains dry on polar aspects and has seen little wind effect. However, solar aspects have now seen several generations of sun crust, and this recent snow was moist on the surface today on solar aspects.
Forecasters are tracking 3 main weak layers in the snowpack. First, a buried sun crust on solar aspects, or a layer of facets on polar aspects, are producing some natural and human-triggered avalanches down between 20 and 40cm. Second, a weak layer of facets buried back in late January has occasionally been active down 80 to 100cm. A very large human-triggered avalanche occurred on this layer late last week. And finally, the basal weaknesses remain. Deep persistent slab avalanches are still possible, especially in shallow snowpack areas. This deep layer may also be prone to "waking up" as slopes start to get more significant solar input. Forecasters continue to have zero confidence in larger terrain features, and we continue to avoid significant overhead terrain.
Wednesday should be a beautiful day with lots of sun, temps near +1C and freezing levels climbing to 2200m. Winds will be light from a variety of directions. No new snowfall is expected.
More details can be found in the Mountain Weather Forecast.
