Avalanche Forecast
Issued: Apr 11th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
jpercival,
Avalanche Canada
The past storm snow has added additional weight and stress to a weak and unpredictable layer that remains a concern and undermines the base of the snowpack.
Thin, rocky and steep terrain is the most prominent terrain features that the deep persistent slab has continued to be problematic.
As the freezing level rises and the sun appears, you will find that conditions change drastically through the day.
Summary
Confidence
Avalanche Summary
On Monday, near Golden, explosives avalanche control produced a few large (size 2) storm or wind slab avalanches, and one very large (size 3) deep persistent slab avalanche. These avalanches occurred on steep, rocky, sparsely treed ridge features.
West of Invermere, a large (size 2.5), naturally triggered loose wet avalanche was reported that likely started just below treeline, and buried a road cut 2-3 m deep.
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
15-30 cm of recent snow in the alpine covers settling, dry snow on shaded (northerly) aspects, and a frozen crust on solar aspects. At treeline, the recent snow is likely to be denser, shallower, and moist or refrozen.
Below treeline, rain soaked surfaces are starting to freeze as temperatures drop, and a lot more dirt is showing at low elevations.
The mid snowpack is generally settled and strong, although west of Invermere, some professional operations are still monitoring a layer of weak, feathery surface hoar crystals that was buried in mid January.
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 last Thursday.
Weather Summary
Overnight cooling followed by afternoon rising freezing levels and warming is likely to unconsolidated and rapidly settle the upper snowpack especially on south aspect terrain when the sun appears. Prepare to continually evaluate the conditions, and change plans as necessary.
Tuesday Night
Clearing with cloudy periods. 1-5 cm of snow is possible in the alpine. Freezing level descending to 700m, Alpine temperature low of -8°C. Light southwest ridgetop wind.
Wednesday
Clear and sunny with no forecast precipitation. Freezing level rising to 1600m mid day. Alpine temperature high of -1. Light northwest wind.
Thursday
Clear and sunny with no forecast precipitation. Freezing level rising to 1500m mid day. Alpine temperature high of -1°C. Light northwest wind.
Friday
Clear and sunny with no forecast precipitation. Freezing level rising to 1700m mid day. Alpine temperature high of 0°C. Light northwest wind.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Be alert to conditions that change throughout the day.
- Be alert to conditions that change with aspect and elevation.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
Problems
Storm Slabs
Storm totals have been observed at between 15-30 cm in the alpine.
Past 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 ridgecrest, 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: All elevations.
Likelihood
Expected Size
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
Expected Size
Valid until: Apr 12th, 2023 4:00PM
