Warming temperatures will likely increase the probability of large human triggered avalanches. See the latest forecaster blog for more information on this atypical coast mountain snowpack: http://bit.ly/1HHQrK2
Weather Forecast
Thursday: No significant precipitation expected. Moderate SW winds at treeline, strong W/SW winds at ridgetop. Freezing level starting the day at 2500m, climbing to around 2700m by Thursday night.Friday: No significant precipitation. Freezing level starting around 2700m, lowering slightly to 2200m in the evening. Moderate to Strong SW winds at all elevations.Saturday: Freezing level starting at a more seasonal 1500m, rising to 1800m in the afternoon. Scattered convective flurries with no significant accumulations expected. Moderate W/SW winds at treeline, Strong ridgetop winds out of the NW in the morning switching to SW in the afternoon.
Avalanche Summary
Over the past week, there have been a number of avalanches to size 2.5 occurring on the mid-March persistent weak layer. Some avalanches have occurred naturally and many have been remote triggered from up to 100m away.
Snowpack Summary
5 to 20 cm of light storm snow fell in the last 48 hours. This snow rests on top of ageing wind slabs that formed over the last week in response to recent wind, snowfall and warm temperatures. At lower elevations, rain has saturated the snowpack. Cornices may also be fragile. A touchy crust/facet interface known as the mid-March persistent weak layer is 40 to 120 cm below the surface. This persistent weak layer continues to produce sudden test results at upper treeline and alpine elevations, especially in the north of the region. Below this, the snowpack is reported to be generally well-settled and strong.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.