Avalanche Forecast
Regions: Glacier.
Rogers Pass and the surrounding Columbia Mtns have a weak basal snowpack this season, which is making all snow professionals work hard to manage avalanche problems that are atypical of these areas.
Drop your desires down a notch; ski/ride to the conditions we have this year.
Confidence
Moderate
Avalanche Summary
A field team today triggered a couple of size 1.0 slab avalanches on small convex rolls at the treeline - one of these failed on the Jan 3rd surface hoar layer down 35cm.
In neighboring areas there are continued reports of isolated human triggering of the recently buried surface hoar layers, as well as natural/explosive triggering of the deep persistent facet layer.
Snowpack Summary
Recent warm temperatures have left a melt-freeze crust at or near the surface below ~1600m.
Two surface hoar (SH) layers, present in the upper 40cm, are potential failure planes in areas where the surface snow has become slabby (ridgecrests, immediate lee features).
The mid-pack facets are slowly rounding and gaining strength, while the basal facets and Nov 17 facet/SH/crust weakness are still reactive when isolated in snowpack tests.
Weather Summary
A couple of weak fronts pass our area this evening, giving a few cms of new snow, with light ridgetop winds, and alpine temps dropping to -9*C.
This will be followed by a ridge of high pressure over our area until the weekend. Giving a mix of sun and cloud, seasonal temps (-12 to -6*C)and light winds.
Another cold front on Saturday will bring increased wind and up to 10cm of new snow.
Terrain and Travel Advice
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Avalanche Problems
Persistent Slabs
The Jan 3 surface hoar (5-10mm) is buried ~40cm and is more reactive at ridgeline or in immediate lee features, where wind has stiffened the surface. If triggered, this slab has the potential to step down to the deep persistent layer.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1.5 - 2.5
Deep Persistent Slabs
The Nov 17 layer, which consists of a faceted crust and decomposing surface hoar, highlights a weak basal snowpack.
Be particularly cautious in steep, rocky areas with thin snow coverage, where the majority of the snowpack is weak and faceted.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Unlikely - Possible
Expected Size: 2 - 4