Avalanche Forecast
Issued: Mar 11th, 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.
zryan,
Avalanche Canada
Diligently maintain a conservative mindset. You may not see signs of instability on the surface however the deep persistent weak layer remains a major concern at the bottom of the snowpack.
Keep in mind that even short periods of sun can have a significant impact. Give steep solar slopes and overhead cornices a wide berth during periods of strong solar radiation.
Summary
Confidence
High
Avalanche Summary
On Thursday, a natural cornice failure triggered a size 2 persistent slab in the Dogtooth range north of Golden. This avalanche occurred on a northwest aspect in the alpine .
On Wednesday, two, size 3 cornice triggered avalanches were observed near Golden. The avalanches happened on northerly aspects and stepped down to the ground. Explosives control triggered a few avalanches on both the deep persistent weak layer to size 2 and on the persistent weak layer to size 3.
On Tuesday, a natural size 2.5 persistent slab avalanche was observed near Golden on a south aspect at 2600 m.
On March 1st, a fatal avalanche incident involving a group of skiers occurred in the Purcell Mountains west of Invermere BC. The size three avalanche was triggered on a southwest facing slope at 2500 m. The weak layer of facets buried in late November that sits at the bottom of the snowpack was responsible for this avalanche.
Snowpack Summary
Up to 10 cm of low-density new snow overlies hard, wind-affected surfaces in open areas, surface hoar and facetted snow in sheltered areas and a sun crust on steep solar slopes.
Buried surface hoar sits 50-70 cm deep in sheltered terrain features, and a thin sun crust exists at the same depth on steep south-facing terrain. Several other layers from January can also be found in the top 100cm of the snowpack.
The lower snowpack is made up of a widespread layer of large, weak basal facets and depth hoar in some areas. this weakness has been responsible for a number of recent very large, destructive avalanches and will continue to be a concern.
Weather Summary
Saturday night
Cloudy with clear periods and isolated flurries. Alpine temperatures drop to a low of -10 °C. Ridge wind light from the southwest. Freezing level at valley bottom.
Sunday
A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -8 °C. Ridge wind light from the south. Freezing level rises to 1300 meters.
Monday
Cloudy with mixed precipitation, 5-15 cm of new snow accumulation at higher elevations. Alpine temperatures reach a high of -4 °C. Ridge wind southwest 30-50 km/h. Freezing level rises to 1700 meters.
Tuesday
A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -9 °C. Light ridge wind from the southwest. Freezing level rises to 1200 meters.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
- Use conservative route selection and resist venturing out into complex terrain.
- Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
- Avoid areas with a thin or variable snowpack.
Problems
Deep Persistent Slabs
The base of the snowpack remains very weak. Very large human triggered avalanches are possible at treeline and above. Avoid shallow and rocky areas, where the snowpack depth is highly variable. This is a very concerning avalanche problem and should stay in your mind when traveling in the backcountry.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Numerous weak layers from January and February exist at all elevations on a variety of aspects. On shaded slopes, these layers generally present as surface hoar, and on sun-exposed slopes they present as facets and a crust.
Avalanches triggered on these layers can step down to the facets at the bottom of the snowpack resulting in a very large avalanche.
These layers can be remotely triggered. Avoid traveling below steep slopes.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 12th, 2023 5:00PM
