Archived

Avalanche Forecast

Jan 15th, 2023–Jan 16th, 2023

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Glacier.

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.

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.

Avalanche 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: Possible - Likely

Expected Size: 1.5 - 2.5

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: Possible

Expected Size: 2 - 3.5