Avalanche Forecast
Issued: Apr 20th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Persistent Slabs and Deep Persistent Slabs.
istorm,
Avalanche Canada
It's a challenge to manage different avalanche concerns that vary by elevation and aspect. Observe local conditions and use that information to help select terrain and travel techniques. Match terrain to conditions!
The April Fools Day crust, up to 100 cm below the surface remains a concern, especially on east, south, or west facing slopes at treeline and higher elevations.
Summary
Confidence
Moderate
Avalanche Summary
On Wednesday a size 3 Glide Slab was reported on a south facing rock slab releasing near treeline. Explosive cornice control work mostly resulted in large chunks dropping but out of 10 events only 2 pulled size 2 slabs from the slopes below (in the Purcells).
A number of persistent slab avalanches were reported on Tuesday, up to size 2. They were a combination of explosive and skier triggered, and all appear to have failed on lingering and problematic April Fools Day surface hoar/crust combination. All reported avalanches occurred in the western Purcells.
In the Selkirks the avalanche activity appears to be slowing. However, many natural and human-triggered avalanches were reported last week. Many of these slid on the same April Fools Day crust, including a fatal avalanche in the western Purcells and a close call near Revelstoke.
Snowpack Summary
Dry, powder snow remains at higher elevations on north-facing terrain. While multiple melt-freeze crusts or moist snow are found in the snowpack on steep solar slopes and at lower elevations.
A layer of surface hoar from March 31 persists down roughly 50 to 100 cm appears to be variable in its distribution. The surface hoar may be sitting above a crust on all but true north-facing slopes. Despite a decrease in avalanche activity on this layer, avalanche professionals continue to closely monitor it. Additionally there are similar crusts dating from April 16 and April 7 higher up in the snowpack with similar characteristics and concerns.
The mid-snowpack is strong. However, the November depth hoar remains at the base of the snowpack and remains a concern in rocky, shallow, variable depth snowpack areas at treeline and above.
Weather Summary
Thursday Overnight
Cloudy with clear periods and flurries; only a trace of precipitation. Light, with moderate gusts, southwest winds. Treeline temperatures around -5 to -10 C. Freezing level at valley bottom.
Friday
A mix of sun and cloud with just a trace of precipitation, maybe as much as 5 cm at favoured high elevation upslope locations. Light southwest ridgetop winds. Treeline temperatures around -5 C. Freezing level around 1800 to 2000 m.
Saturday
Cloudy with sunny periods and isolated flurries.. Just a trace of new snow. Light southwest ridgetop winds. Treeline temperatures around -5 C. Freezing level around 1900 m.
Sunday
Mostly cloudy with flurries and just a trace of new snow except around 5 cm on favoured upslope areas. Moderate southerly winds. Treeline temperatures around zero and freezing level around 2100 to 2300 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.
- Be alert to conditions that change with elevation and sun exposure.
- Closely monitor how the new snow is bonding to the crust.
- Be carefull around freshly wind loaded features.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Problems
Storm Slabs
Scattered snowfall continues to build storm slabs and may need time to bond to underlying surfaces. Be especially cautious at higher elevations, near ridges and mountain tops were wind has likely increased slab depth and reactivity.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A layer buried on April 1, down roughly 50 to 100 cm from the surface, appears to be most reactive on solar tilted slopes where surface hoar may sit on a hard melt-freeze crust.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
A weak layer of facets exists near the base of the snowpack. The likelihood of human triggering is low given the layer's depth.
Suspect terrain includes steep, shallow, and rocky terrain where the snowpack varies between thin and thick.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 21st, 2023 4:00PM
