Avalanche Forecast
Issued: Feb 19th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Deep Persistent Slabs and Persistent Slabs.
isnowsell,
Avalanche Canada
The current snowpack is very complex and requires careful terrain selection, and extremely diligent group management. Seek out low-angle, low-consequence terrain, and avoid areas where an avalanche could propagate widely.
Very large, full depth avalanches remain possible. This layer resulted in a fatal avalanche that occurred west of Golden on Thursday. Details can be found in this report.
Summary
Confidence
Moderate
Avalanche Summary
On Saturday a large (size 2.5), natural avalanche was reported from the far north of the region. It was initiated as a wind slab near ridgetop, before stepping down to basal facets and ground.
A couple of wind slab avalanches were also reported Saturday throughout the region, in steep alpine terrain.
On Friday, our field team observed a size 3.5 avalanche in the Bull River area (South Rockies) on an east through southeast aspect that started high and ran nearly 2000 m to the river. They estimated this avalanche to likely have occurred on or around February 15. Given its size, this avalanche likely failed on a deep persistent weakness in the snowpack.
On Thursday, a size 3.5 avalanche failed on a deep persistent weakness, resulting in 2 fatalities west of Golden. More details regarding this avalanche can be found in this report.
Snowpack Summary
New snow over the long weekend has buried a layer of surface hoar that formed in open areas and a sun crust that exists on steep south aspects. In exposed terrain, recently formed wind slabs exist in leeward features.
A variety of persistent layers still exists in the middle snowpack and continue to see avalanches occur on them periodically. Don't let these layers surprise you.
The lower snowpack contains a widespread layer of large, weak facets that is typically 80 to 150 cm deep. This layer continues to periodically produce very large and destructive avalanches.
Snowpack depths at treeline range between 80 and 200 cm, with the shallowest snowpacks found on the eastern edge of the Purcells.
Weather Summary
Sunday night
Cloudy with trace amounts of snow. Moderate to strong west to northwest alpine winds. Treeline temperatures -5 to -10 C.
Monday
Cloudy with flurries, 0 to 5 cm. Moderate to strong west to northwest alpine winds. Treeline temperatures -5 to -10 C.
Tuesday
Cloudy with snowfall beginning Monday night, 10 to 20 cm by end of the day. Moderate to strong southwest alpine wind, switching to the northeast by the end of the day. Treeline temperature -10 to -15 C.
Wednesday
A mix of sun and cloud, with flurries and trace amounts of snow. Moderate northerly alpine winds. Treeline temperatures -15 to -20 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.
- Use careful route-finding and stick to moderate slope angles with low consequences.
- Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
Problems
Wind Slabs
Recently formed wind slabs remain reactive in wind exposed terrain features. Watch for ongoing wind slab formation with new snow and more wind forecast. Be especially cautious as even a small wind slab avalanche could step down to deeper weak layers.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
It remains possible for riders to trigger a weak basal facets at the bottom of the snowpack. The most likely area to trigger it is in shallow areas with variable snow depths. Avoid thin and rocky start zones and select routes that avoid traveling through or under large avalanche paths.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Large avalanches have been triggered on a layer of surface hoar and facets 40 to 80 cm deep which was buried in late January. This problem seems most concerning in the western and southern Purcells, where the layer is more deeply buried and primed for human triggering.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 20th, 2023 4:00PM
