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Avalanche Forecast

Jan 23rd, 2020–Jan 24th, 2020
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
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
1: Low
The avalanche danger rating below treeline will be low

Regions: Sea To Sky.

An intense storm will continue to create very dangerous avalanche conditions on Friday.

Confidence

High - We are confident the snowpack will rapidly lose strength with the arrival of the forecast weather.

Weather Forecast

THURSDAY NIGHT: Heavy flurries continue overnight, especially near the coast, overnight accumulations of 15-30 cm above 1200 m, strong wind from the southwest, alpine temperatures around -3 C.

FRIDAY: Snow continues throughout the day with another 15-25 cm, moderate wind from the southwest, freezing level drops to 1200 m with alpine temperatures around -3 C.

SATURDAY: Cloudy with isolated flurries and 5-15 cm of snow, light wind from the south, alpine high temperatures around -3 C.

SUNDAY: A brief period of calm and clear conditions in the morning before the next system arrives in the afternoon bringing moderate accumulations of new snow.

Avalanche Summary

Preliminary reports from Thursday morning suggest large (size 2) storm slabs were easy to trigger with explosives, producing 40-60 cm thick slabs with wide propagation. Explosive control on Wednesday resulted in a very large (size 3.5) deep persistent slab on a west aspect the alpine, suggesting the deep persistent slab will likely remain reactive during this storm. With more loading on the way natural storm and deep persistent slab avalanches are serious concerns. 

Snowpack Summary

A frontal system crossing the region has already delivered 40-60 cm of snow by Thursday afternoon and another 30-50 cm is expected by Friday afternoon, resulting in very thick storm slabs at higher elevations. Thinner deposits of new snow are expected below 2000 m due to a mix of rain and snow during the storm. Wind over the past few days has been strong to extreme from the south, resulting in highly variable conditions in open terrain.

Prior to the storm there were reports of a 50 cm deep rain crust that had been the bed surface for small storm slab avalanches below 2000 m. Weak faceted grains and crusts near the base of the snowpack continue to be a concern in inland parts of the region such as the Spearhead Range.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Avoid traveling through runout zones during stormy periods when large avalanches are likely.

Avalanche Problems

Storm Slabs

As the intense storm continues into Friday morning large storm slab avalanches are expected to occur naturally.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 2 - 3

Deep Persistent Slabs

Weak snow at the bottom of the snowpack is being stressed by rapid loading which could result in very large, naturally triggered deep persistent slab avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 3.5