Avalanche Forecast

Moderate - Timing, track, or intensity of incoming weather system is uncertain

TUESDAY NIGHT: Cloudy with snowfall, accumulation 10 to 20 cm, moderate westerly winds, alpine temperature near  -10 C, freezing level below valley bottom.WEDNESDAY: Cloudy with snowfall, accumulation 10 to 15 cm, light to moderate westerly winds, alpine temperature near -6 C, freezing level near valley bottom.THURSDAY: Cloudy with light snowfall early morning, accumulation 10 to 15 cm, light to moderate westerly winds, alpine temperature near -10 C, freezing level below valley bottom.FRIDAY: Mostly sunny with possible valley cloud, light to moderate northwesterly winds, alpine temperature near -14 C, freezing level below valley bottom.

On Monday, loose dry avalanches were observed from solar aspects during the heat of the day.  Otherwise, more evidence of a natural avalanche cycle from Friday to Sunday was noted.  Many slabs were observed, which were expected to have released during the storm.  This includes many wind, storm, and persistent slab avalanches, from small to large (size 1 to 3).  The slabs were 30 to 200 cm deep, on all aspects, and most often at upper below treeline, treeline and alpine elevations.  Many of the releases were highly destructive, such as this one, highlighting the consequence if an avalanche is triggered.Looking forward, dangerous snowpack conditions will exist on Wednesday with new snowfall and strong winds. All of our buried weak layers (described in the section below) continue to produce large destructive avalanches from natural and human triggers. New storm slabs and wind slabs have the potential to step down to deeper weak layers, which could produce large, destructive avalanches.

Up to 40 cm of snow could accumulate in the region by Wednesday afternoon.  This overlies 40-100 cm of storm snow from the past two weeks that has formed a slab that sits over an unstable snowpack.  There are three active weak layers that we are monitoring:1) The first layer is buried around 70 to 100 cm and is formed of a crust and/or surface hoar layer that was buried in mid-January. The surface hoar is up to 10 mm in size, found at all elevation bands and has been very reactive on north through east aspects between 1900-2600 m.2) Deeper in the snowpack, the early-January persistent weak layer is found 60 to 120 cm below the surface. This layer was reported as the most active persistent weak layer during a recent natural avalanche cycle that took place in the region. It was also very reactive to recent explosives control.3) Another weak layer buried mid-December consists of a facet/surface hoar/crust combination, which is 100 to 180 cm deep. It has been most problematic at and below tree line.