Avalanche Forecast
Issued: Jan 4th, 2020 4:30PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
astclair,
Avalanche Canada
Continuing snowfall and wind is out-pacing the snowpack's ability to adjust. Stay vigilant with simple terrain choices as this pattern continues.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
Saturday night: Mostly cloudy, scattered flurries with trace accumulations, moderate to strong southwest winds, alpine temperature -10 C.Â
Sunday: Cloudy, 5-15 cm of snow, strong southwest winds, alpine high temperature -6 C.
Monday: Mostly cloudy with isolated flurries, light southwest winds, alpine high temperature -6 C.
Tuesday: Cloudy, 10-15 cm of snow, light southeast winds, alpine high temperature -5 C.
Avalanche Summary
On Friday and Saturday there were reports of numerous large (size 2-2.5) storm slab avalanches releasing naturally on all aspects and all elevations. This MIN report from Saturday is a great example. Several avalanches have also been remote-triggered, like this one observed Wednesday.Â
Within the past week, a couple avalanches reportedly released on deeper buried weak layers. While avalanche activity on these deeper layers has tapered, it is not out of the question given the continual loading from new snow and wind.
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Snowpack Summary
50-80 cm of new snow has fallen throughout the past week creating a touchy storm slab problem. At high elevations, this snow has been redistributed by strong southwest winds, loading lee features near ridges and exacerbating reactivity. The storm snow overlies a weak layer of feathery surface hoar and a hard melt-freeze crust on sun-exposed aspects, also increasing the reactivity of these slabs.
There are a couple weak layers buried around 60 to 180 cm deep, including two more layers of surface hoar from December, and a weak facet/crust layer near the bottom of the snowpack from late November buried over 160 cm deep. It is possible that easier-to-trigger storm slab avalanches could step down to these deeper, persistent layers or that the weak layers could be human-triggered in areas in the alpine where the snowpack is thin, rocky, or variable.
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Be alert to conditions that change with elevation and wind exposure.
- Avoid freshly wind loaded terrain features.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
Snowfall continues to accumulate and storm slabs remain reactive as slab depths increase and stiffen over a recently buried layer of surface hoar. Thicker slabs are found in wind-loaded terrain features, particularly near ridges. Conservative terrain selection is required to avoid this avalanche problem.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
There is still concern for heavy loads (storm slab avalanches running) to step down and trigger deeper weak layers buried in December.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 5th, 2020 5:00PM
