Avalanche Forecast
Issued: Feb 13th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Persistent Slabs and Deep Persistent Slabs.
llarson,
Avalanche Canada
Continued convective flurries Monday evening, coupled with moderate variable winds will continue to form fresh and reactive storm and wind slabs primed for human triggering. Keep in mind that triggering a slab on the surface is probably the most effective way to cause a large and destructive step-down avalanche.
Summary
Confidence
Avalanche Summary
Several human-triggered and natural wind slabs up to size 2, generally between 30 to 45 cm deep have been reported throughout the region.
A revealing MIN post from the McBride area on Saturday showed concerning evidence of an emerging persistent slab problem associated with what is likely our initial storm interface from early February. Aside from easy test results in surface layers, a more problematic layer of surface hoar buried 65 cm deep in this below treeline area appears to be the culprit in numerous touchy persistent slab releases. This activity suggests extra caution is currently needed to manage overlapping storm/wind slabs and persistent slab problems.
Snowpack Summary
Continued accumulation of new snow, coupled with moderate winds will continue to develop wind slabs in open terrain features at treeline and alpine elevations. In sheltered terrain features, snow is less affected by wind but the recent accumulated snow is taking time to bond to previous surfaces.
Two layers of surface hoar crystals and/or melt-freeze crust sit in the mid-snowpack. The first varies in depth across the region from 45 to 100 cm and is most likely found around shaded treeline and lower alpine elevations. The roughly 150 cm-deep melt-freeze crust is found up to 1800 m on all aspects and into the alpine on sun-exposed slopes. These layers continue to be tracked by local operators, but only the surface hoar layer seems like it might currently be an active weak layer.
A final concerning weak layer in the snowpack is composed of large and weak facets from November located near the base of the snowpack. Although this layer hasn't produced avalanches recently, it continues to guide terrain selection by professionals in the region.
Weather Summary
Monday night
Cloudy with lingering flurries bringing 5 cm of new snow. 5 to 10 km/h northwest winds, treeline temperatures -7 °C.
Tuesday
A mix of sun and cloud, increasing overnight, trace accumulations, with 10 to 20 km/h northwest winds shifting southwest. Treeline temperatures -10 °C.
Wednesday
Mainly cloudy, 5 to 10 km/h southwest winds. Treeline temperatures -10 °C.
Thursday
Cloudy, Flurries with 5 to 10 cm accumulation, 10 to 20 km/h southerly winds increasing throughout the day, treeline temperatures -13 °C
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- 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.
Problems
Wind Slabs
Continuing, convective snowfall and moderate to strong variable winds are building storm slabs and wind slabs that will be reactive to natural and human triggers. Expect wind-loaded spots to be particularly touchy.
Keep in mind that storm slabs have the potential to step down to deeper weak layers, resulting in large and consequential avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A surface hoar layer found in the upper 100 cm of the snowpack has recently been touchy to human triggering and may be most problematic in open terrain below treeline. Be especially cautious around steep openings at low and mid elevations, especially where recent storm snow has been wind loaded.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
A layer of large and weak facets sits near the base of the snowpack. This layer is most prominent in upper treeline and alpine elevations. Riders are most likely to trigger an avalanche on this layer in steep, shallow terrain. Your best defence is to stay diligent in choosing low-consequence terrain away from overhead exposure.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 14th, 2023 4:00PM
