Avalanche Forecast
Issued: Mar 30th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs and Persistent Slabs.
wlewis,
Avalanche Canada
A weak snowpack still exists throughout the Purcells. Avoid thin and rocky start zones.
The best riding conditions can be found at higher elevations on shaded slopes where weak layers may be preserved. Minimize your exposure to large, high consequence slopes.
Summary
Confidence
Avalanche Summary
Over the last three days wet loose avalanches have occurred primarily on steep south facing (sun affected slopes) at lower elevations with rising freezing levels and strong sunshine. Cloud and cooler temperatures on Friday will reduce the likelihood of wet avalanche activity.
No activity on the deeply buried weak layers has been reported this week. However thin and rocky terrain features in the upper treeline and alpine should still be avoided.
Snowpack Summary
Dry snow still exists at upper elevations on shaded slopes, where southwest winds may redistribute snow into small pockets of wind slab on north and east facing terrain. Faceted snow and surface hoar (up to 10 mm) may sit below in shaded and sheltered areas. Moist snow is present on most other aspects and elevations, sitting over a crust from previous melt freeze cycles.
In the middle of the snowpack there are lingering persistent weak layers, including layers of surface hoar in wind-sheltered terrain and a sun crusts on south aspects. Activity on these layers has tapered off, but triggering remains possible in isolated features.
The lower snowpack includes a widespread layer of large, weak facets and or depth hoar crystals. This weak layer has been responsible for a number of very large, destructive avalanches this season, including several last week and will continue to be a concern for the rest of the season.
Weather Summary
Thursday Night
Freezing levels drop back to 500 m, with light westerly winds around 10 km/hr. Partly cloudy skies.
Friday
Mostly cloudy with flurries delivering up to 5 cm of snow. Light southerly wind gusting 40 km/h. Freezing level rises to 1500 m, alpine temperatures of -5 °C.
Light snowfall continues overnight, around 5 cm.
Saturday
Cloudy with sunny periods possible in the afternoon. Light snowfall brings 5-10 cm. Light southwesterly wind gusting 40 km/h. Freezing level rises to 1500 m, alpine highs of -5 °C.
Sunday
A mix of sun and cloud with flurries delivering up to 5 cm. Freezing levels rise to 1300 m with alpine highs of -7 °C. Light southwest winds.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
- Be alert to conditions that change with aspect and elevation.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Problems
Deep Persistent Slabs
The base of the snowpack remains very weak. Very large human-triggered avalanches are possible at treeline and above. Avoid thin, rocky start zones and shallow areas with variable snowpack depths. Weak layers are most triggerable here as they sit closer to the surface of the snowpack.
Give careful consideration to the slopes overhead as large avalanches may run well into the runout zone or into lower-angle terrain.
Deep persistent avalanches are challenging to predict. This layer can suddenly become active again, typically when there is rapid change or stress to the snowpack - sudden warming, heavy snow or rainfall, or heavy loads eg. cornice fall.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Lingering weak layers are present at all elevations and on various aspects. On shaded slopes, these layers generally present as surface hoar or facets, while on sun-exposed slopes, they appear as facets and a crust. Uncertainty remains about the effect of solar radiation on this layer.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 31st, 2023 4:00PM
