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Archived

Avalanche Forecast

Jan 16th, 2023–Jan 17th, 2023
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
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
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.

Two persistent weak layers (surface hoar) are buried in the upper 40cm. These layers take additional time to bond with the new snow, necessitating folks to stick to well-supported, lower-angled terrain lest they tickle the underbelly of the surface hoar beast.

Surface slabs have the potential to dig deeper, triggering the deep persistent slab, resulting in large, destructive avalanches.

Confidence

Moderate

Avalanche Summary

Natural avalanche activity has slowed, with isolated sz 1.5-2 soft slabs observed from mostly steep S'ly terrain. The weekend's avalanche cycle saw numerous sz 2-3 storm and persistent slabs ripping out of Mts MacDonald and Tupper. The west side of the Pass saw smaller results (sz 1.5-2) on Mts Smart, Abbott, Ross Pk, and Cougar Mtn.

Snowpack Summary

Two surface hoar (SH) layers, present in the upper 40cm, are potential failure planes if the new snow stiffens up on top of them. The mid-pack facets are slowly rounding and gaining strength, while the basal facets and Nov 17 facet/SH/crust weakness are still reactive when isolated in snowpack tests.

Weather Summary

The Coastal storms don't seem to have enough punch to get to the Pass. General cooling trend and isolated flurries this week.

Tues: mainly cloudy, trace snow, Alp high -8*C, 1100m FZL, light SW ridge winds

Wed: mix of cloud and sun, trace snow, Alp high -8*C, 1100m FZL, light SW ridge winds

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

Expected Size: 1.5 - 2.5

Deep Persistent Slabs

The Nov 17 layer, which consists of a faceted crust and decomposing surface hoar, highlights a weak basal snowpack.

Be particularly cautious in steep, rocky areas with thin snow coverage, where the majority of the snowpack is weak and faceted.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3.5