Confidence
Fair - Freezing levels are uncertain on Friday
Weather Forecast
Synopsis: The interior of BC will come under the influence of a strong ridge of high pressure and warm temperatures for the next few days.Overnight: Light precipitation, winds changing to mod to strong,W-SW, freezing levels may rise to 1200m.Wednesday: Some sunny periods, winds moderate to strong from the west, freezing levels to 1200 M in parts of the forecast area.Thursday: No precipitation in the forecast, sunny periods,. light winds at ridge tops freezing level rises to 1600m.Friday: No Precipitation , sunny periods, light winds at ridge tops, freezing levels may rise to 2300m in some parts of the forecast area.
Avalanche Summary
A natural avalanche cycle has been reported throughout the forecast area with avalanches running full path up to size 3.5. Buried persistent weaknesses have now become reactive with heavy loading from snow and wind. Until the snow pack adjusts to the new load, heightened avalanche awareness and caution is needed to travel safely in avalanche terrain.
Snowpack Summary
Parts of the forecast area have received over 80cm of storm snow, now overlying a variety of old surfaces ranging from wind slabs, to a soft layer of facetted snow and / or surface hoar from earlier in January, now buried in the snowpack between 60 and 85cm. There are recent reports of shears in the new storm snow that may be the result of heightened wind activity or changes in the nature of the snowfall during the storm.100cm or more below the surface there is a thin melt freeze crust below 2100m elevation, as well as other buried weak layers (surface hoar, facetted snow, and/or a crust) that continue to be reactive in snowpack tests. There are two deeper layers of note. The late-November persistent weak layer is a sun crust on steep south facing slopes and surface hoar in sheltered areas and now may be 200cm below the surface. The October deep persistent weak layer consists of a layer of facets sitting on a crust at the base of the snowpack. This layer is predominantly found on northerly aspects at tree line and in the alpine. An avalanche stepping down to this layer might dramatically increase the size of the avalanche.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.
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.