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Archived

Avalanche Forecast

Feb 20th, 2023–Feb 21st, 2023
Alpine
4: High
The avalanche danger rating in the alpine will be high
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
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
1: Low
The avalanche danger rating below treeline will be low

Stormy conditions on Monday night will produce dangerous avalanche conditions for Tuesday.

Confidence

Moderate

Avalanche Summary

Small wind slabs were triggered by riders on Sunday as the recent snow was redistributed by wind.

On Saturday, explosives triggered a few large (size 2 to 3) deep persistent slab avalanches 200 cm deep on north to east aspects between 1900 and 2300 m.

Looking forward, large storm and wind slabs could be human-triggered within all the recent storm snow. Wind slabs could rapidly form on atypical aspects due to northeast wind on Tuesday.

Snowpack Summary

Monday night's storm snow will add to the 40 to 80 cm of recent storm snow, which may sit on a small layer of surface hoar crystals in wind-sheltered terrain. In wind-exposed terrain, the snow is being redistributed into wind slabs and large cornices. The wind was predominantly southwest but is switching to northeast, meaning that wind slabs may be found on all aspects.

The mid-pack is generally strengthening. A spotty surface hoar layer may be found about 80 to 150 cm deep. This layer is most likely found in openings around treeline elevations that are sheltered from the wind. The layer hasn't produced recent avalanches.

Large and weak facets that formed in November are found near the base of the snowpack. A cornice fall is a likely trigger for this layer.

Weather Summary

Monday Night

Cloudy with snowfall, accumulation 15 to 25 cm, 20 to 40 km/h southwest wind, treeline temperature -14 °C.

Tuesday

Mostly cloudy with isolated snowfall, accumulation 1 to 3 cm, 30 km/h northeast wind, treeline temperature -20 °C.

Wednesday

Mix of sun and cloud with no precipitation, 20 km/h northeast wind, treeline temperature -25 °C.

Thursday

Mix of sun and cloud with no precipitation, 20 km/h northeast wind, treeline temperature -26 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Travel in alpine terrain is not recommended.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Minimize your exposure time below cornices.

Avalanche Problems

Storm Slabs

Snow and strong wind on Monday night will add to the 40 to 80 cm of snow that recently accumulated. Both storm slabs and wind slabs could be triggered on Tuesday, particularly in wind-exposed terrain and where all this snow overlies weak surface hoar crystals.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2.5

Deep Persistent Slabs

A layer of large and weak facets sits near the base of the snowpack. This layer is most prominent in upper treeline and alpine elevations and continues to produce sporadic, destructive avalanches. Human-triggering is most likely on steep, shallow, rocky slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 4