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Avalanche Forecast

Archived

Jan 20th, 2023–Jan 21st, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Below Threshold.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Below Threshold.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Below Threshold.

Regions

Yukon, Tutshi, Wheaton, White Pass East, White Pass West.

Strong winds and new snow available for wind transport have heightened the avalanche danger rating and will continue to build upon already reactive windslabs.

Adopt a conservative terrain travel strategy that avoids steep north aspect terrain and seeks out low-angle well supported terrain.

Confidence

Moderate

Avalanche Summary

On Wednesday our field team observed a widespread natural avalanche cycle in the high alpine that was confined to north aspect and cross-loaded terrain features. These avalanches were small (mostly size 1 to 1.5) But a few noted large avalanches occurred (size 2). Everything observed, ran fast and far through the soft and faceted lower elevation surfaces.

Snowpack Summary

Thursday night strong southerly wind transported available new snow that cross-loaded and built windslabs at depths reported between 60 to 70 cm.

These new accumulations overlie an upper snowpack consisting of 15 to 30 cm of both new storm snow and unconsolidated faceted snow. The midpack presents as very dense with a reactive mid-December layer buried down between 40 to 55 cm.

Snowpack depths vary due to wind transport with averages at treeline reported as 125 cm and 200 cm in the alpine. In areas where the snowpack is less than 1 meter in depth, it is reported to be quite faceted and unconsolidated.

Weather Summary

Friday night

Cloudy with snowfall, up to 5 to 15 cm of accumulation. Strong southerly winds continue at 60 km/h to 100 km/h. Alpine temperatures around -2 °C. Freezing level rising to near 900 m.

Saturday

Cloudy with snowfall, between 1 to 3 cm of accumulation. Southerly winds are initially up to 100 km/h easing 20 to 40 km/h. . Freezing level falls to 500 m. Alpine temperatures are around -8 °C.

Sunday

Cloudy with snowfall, 1 to 5 cm accumulation. . Southerly winds 20 km/h strengthening to 80 km/h. Freezing level near valley bottom. Alpine temperatures are around -10 °C.

Monday

Cloudy with snowfall, up to 5 cm of accumulation. Strong southerly winds continue at 60 to 80 km/h. Alpine temperatures around -9 °C. Freezing level rising to near 500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • Wind slabs are most reactive during their formation.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.