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Avalanche Forecast

Archived

Apr 4th, 2022–Apr 5th, 2022

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

Regions

Yukon.

Keep an eye on the wind and snow transport. Slabs may be especially touchy where they overlie a crust.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

Monday night: Increasing cloud and wind, flurries in the morning. South wind increasing to moderate overnight. Ridgetop low -10 C.

Tuesday: Unsettled and windy, up to 5 cm. Models suggest Haines Pass will receive up to 15 cm. Moderate to strong southwest wind. Ridgetop high -6 C.

Wednesday: Flurries, trace to 5 cm. Moderate to strong south wind. Ridgetop high of -4 C.

Thursday: Flurries, trace to 10 cm. Models suggest Haines Pass could get up 20 cm. Strong and gusty southeast wind. Ridgetop high -3 C.

Avalanche Summary

On Saturday, skiers remote triggered a size 2 wind slab from 10 m away on a north aspect. They also saw evidence of a natural wind slab avalanche cycle in the last 2-3 days, with avalanches to size 2 failing in immediate lee features and steep terrain.

Snowpack Summary

Wind has redistributed recent snow into pressed surfaces and wind slab. Northerly and higher elevation terrain holds 10-30 cm settled and wind affected snow over previously wind affected surfaces. A crust is found on all aspects to 1200 m and to ridgetop on solar slopes. The middle of the snowpack is reported to be strong and well settled. Take note, cornices are large and looming.

Terrain and Travel

  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Wind slabs may be poorly bonded to the underlying crust.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.