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Avalanche Forecast

Archived

Feb 7th, 2020–Feb 10th, 2020

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

Regions

Yukon.

Over the weekend, a break in the storm should improve avalanche conditions, although wind affected slopes need to be treated with caution. Another storm is expected Monday. Watch snow amounts with this storm and increase danger to HIGH if more than 25 cm new snow arrives.

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

Friday night: mostly dry. Light westerly winds. Treeline temperatures around -10.

Saturday: Flurries. Winds increasing to strong southwesterly in the afternoon. Treeline temperatures rising to around -6C in the afternoon.

Sunday: Flurries or light snow. Moderate westerly winds. Treeline temperatures around -6C.

Monday: Around 15 cm new snow expected. Strong southerly winds. Temperatures riding to around -2C.

Avalanche Summary

The most recent observations were on Wednesday, when one size 2.5 and several size 1 storm/wind slab avalanches occurred on lee slopes including on slopes at relatively low elevations (1200 m or so). From approximately Feb 1-4 there was an extensive avalanche cycle with many avalanches noted up to size 3, mainly on north aspects.

Over the weekend, I would only anticipate natural avalanches on steep slopes in very windy areas, although human-triggered avalanches remain possible on wind-affected slopes. Avalanche danger will rise in response to forecast new snow and wind on Monday.

Snowpack Summary

Recent new snow has been redistributed by winds blowing from the south to west quadrant. Wind effect is widespread in exposed areas. Recent snowpack tests indicate sudden "pop" results at the base of recent storm snow down around 50 cm. There is reported to be excellent powder and riding in more wind protected / sheltered areas.

Snow depths at White Pass are around 150 cm at our wind protected Fraser study plot. Deeper locations (higher terrain west of the highway) have more than 200 cm, while on the east of the highway depths are around 175 cm. It's reasonable to expect a thin snowpack composed mainly of sugary facets in the Wheaton Valley, and thinner wind-scoured alpine areas.

Terrain and Travel

  • Expect slab conditions to change drastically as you move into wind exposed terrain.
  • If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • Extra caution is needed around cornices under the current conditions.
  • Caution around slopes that are exposed to cornices overhead.

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.