Avalanche Forecast
Regions: Dogtooth, East Purcell, Purcells.
Prepare for a wet and stormy day. Observe your local conditions, and let that guide your terrain choice. Forecasted snow and rainfall amounts are uncertain.
Carefully choose the terrain you play in. A weak, unpredictable layer continues to lurk near the bottom of the snowpack.
Confidence
Low
Avalanche Summary
No notable avalanches were reported before 4 pm on Sunday. Expect avalanche activity to increase on Monday with the arrival of a wet storm.
On Saturday, near both Golden and Invermere. Several small (size 1-1.5), naturally triggered loose wet avalanches were reported on steep slopes. Sun and/or warm temperatures were the most likely triggers.
On Thursday, north of Golden, just outside of the forecast area, a large (size 2), rider triggered, deep persistent slab avalanche was reported on a northwest aspect in the alpine. The avalanche started 50 m above the riders, and 2 sympathetic avalanches were observed on the adjacent slope. See the excellent Mountain Information Network (MIN) post here for more information, including photos, and reflections on a close call.
Snowpack Summary
10-25 cm of new snow in the alpine covers settling, dry snow on shaded (northerly) aspects, and a frozen crust on solar aspects. At treeline, this new snow is likely to be denser, shallower, and moist.
Below treeline, 10-25 mm of rain starts to soak frozen crusts or already wet surfaces, and will be eating away at the snowpack at low elevations.
The mid-snowpack may still contain a number of weak layers, primarily in sheltered treeline terrain. No recent avalanche activity has occurred on these layers, but rising temperatures or an input of rain to the snowpack will test if these layers have strengthened.
The lower snowpack includes a widespread layer of large, weak facets and/or depth hoar crystals. This weak layer has been responsible for several very large and destructive avalanches throughout the season, including one on Thursday.
Weather Summary
Snow/Rain amounts for the incoming storm are uncertain. Weather models are not agreeing on how widespread or intense the precipitation will be. Prepare to continually evaluate the conditions, and change plans as necessary.
Sunday Night
Cloudy around Golden, partly cloudy around Invermere. 5-10 cm of snow expected in the alpine. Rain below 1800 m. Treeline temperature around 0°C. Light southwest ridgetop wind, trending to strong at higher elevations.
Monday
Cloudy. 5-15 cm of snow expected in the alpine. Snow/rain line drops to 1300 m further north, holds around 1900 m further south . Light southwest ridgetop wind, trending to moderate at high elevations.
Tuesday
Mostly cloudy. 5-12 cm of snow expected as the snow line drops back to valley bottom. Light southwest ridgetop wind, trending to moderate at high elevations. Moderate west ridgetop wind.
Wednesday
Partly cloudy. Possible trace of snow expected. Snow/rain line around 1000 m. Light northwest ridgetop wind.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Storm slab size and sensitivity to triggering will likely increase through the day.
- Be careful to keep storm day fever from luring you out into bigger terrain features.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
- A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
Avalanche Problems
Storm Slabs
Storm slabs will be building through the day on Monday.
Strong southwest winds at high elevations could be building deeper, more reactive pockets of slab in leeward terrain.
Storm slabs in motion may step-down to deeper layers in the snowpack that may have been weakened by rising temperatures and/or rain.
Use extra caution around ridgecrests, rolls, and on convex slopes. Retreat to mellower terrain if you find signs of instability like shooting cracks, whumpfs, or recent avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 3
Deep Persistent Slabs
The base of the snowpack remains very weak. Avoid thin, rocky start zones and shallow areas with variable snowpack depths.
Deep persistent slab avalanches continue to be reported in this forecast area. See the avalanche summary for details of a deep persistent slab avalanche that were kindly shared by some backcountry users who had a close call.
This is a low-probability/high-consequence avalanche problem, and managing it is very tricky.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 2.5 - 4
Loose Wet
Below treeline, the precipitation will fall as rain, and through the day, the upper snowpack is likely to become wet and unstable.
If you see signs of a rapidly warming snowpack, like snow that feels like a slurpy, or clumps up and pinwheels down a slope, retreat to mellower terrain.
Aspects: All aspects.
Elevations: Below Treeline.
Likelihood: Possible
Expected Size: 1 - 2