Avalanche Forecast
Issued: Jan 15th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Deep Persistent Slabs.
MH,
Avalanche Canada
Natural avalanche activity is tapering off, but there are a few surface hoar layers in the upper snowpack that will require some time to stabilize, stick to conservative, low consequence terrain. The possibility of avalanches stepping down to deeper weak layers persists, and would result in large destructive avalanches.
Summary
Confidence
Moderate
Avalanche Summary
Natural avalanche activity tapered off on Sunday with less inputs (cooler temps, minimal snow and light winds).
A fairly active avalanche cycle occurred Friday night until Saturday evening with numerous size 2-3 and one size 3 out of the steep terrain on Mt. MacDonald and Mt. Tupper, with some of these running over the snow sheds and full path into the creek. Elsewhere in the Park there were several size 1.5-2.0 from Mt. Smart, Ross Peak, Mt. Abbott and Cougar Mountain.
Snowpack Summary
~20cm of settled snow buries the Jan 12 surface hoar, and the Jan 3 surface hoar is ~20cm below that. The mid-pack consists of rounding facets and is gaining strength, while the bottom of the snowpack is weak and facetted with the Nov 17 facet/crust/surface hoar. This layer is ~50cm above the ground and has become less reactive in tests, but still shows 'sudden' results when it does fail.
At tree line there is ~160cm, which is 70% of an average snowpack
Weather Summary
Monday will be mainly cloudy with isolated flurries and sunny periods. Ridge-top winds will be light from the Southwest with alpine temps ranging from -10 to -6. Freezing level will reach up to ~1400m.
A ridge of high pressure builds on Tuesday into the end of the week.
Terrain and Travel Advice
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Use caution when approaching steep and rocky terrian.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Problems
Persistent Slabs
The Jan 3 surface hoar (5-10mm) is buried ~40cm and has been reactive to human triggering and explosive testing over the last week. If triggered, this slab could step down to deeper layers, resulting in a large avalanche.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
The lower snowpack remains weak from cold temps in December, and includes the Nov 17 layer which consists of a facetted crust in some locations, and decomposing surface hoar.
Be particularly cautious in steep rocky areas, with thin coverage, where the majority of the snowpack is weak and facetted.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 16th, 2023 4:00PM
