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Avalanche Forecast

Archived

Mar 31st, 2021–Apr 1st, 2021

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

Regions

Sea To Sky.

Changing wind has sifted the recent storm snow onto a variety of aspects at upper elevations. Wind slabs may be reactive to skier and rider triggering. Signs of wind slab instability include stiff snow and shooting cracks while you travel, whumphing and hollow sounds. 

Confidence

High -

Weather Forecast

A frontal wave will bring unsettled conditions including cloudy skies and light snow amounts.

Wednesday Night: Cloudy with alpine temperatures near -3. Ridgetop wind strong from the southwest and freezing levels 800 m. 

Thursday: Cloudy with flurries. Ridgetop wind light from the southwest. Alpine temperatures near -4 and freezing levels 1200 m. 

Friday: Cloudy with flurries. Ridgetop wind light from the southwest. Alpine temperatures -7 and freezing levels 1000 m.

Saturday: Snow amounts 10-20 cm with moderate ridgetop wind from the southwest. Freezing level 1200 m.

Avalanche Summary

No new avalanche reports by Wednesday afternoon.  

On Tuesday, reports indicated that small loose wet avalanches occurred from steep rocky terrain. Cornices also became weak and failed with daytime warming. No slabs were reported from the slopes below. 

Wind slabs may be reactive to human triggering on wind-loaded slopes at upper elevations. Cornices are fragile and pose a threat from above and below. 

Snowpack Summary

Up to 40 cm of snow fell throughout the region since the weekend. This was accompanied by strong southwest winds that switched to the northwest. Reactive wind slabs could be lingering on a variety of aspects at upper elevations, especially where they sit above a crust. 

The recent snow sits above a variety of old snow surfaces comprising mostly of a widespread melt-freeze crust with the exception of high north-facing terrain where it may be sitting on small surface hoar crystals. A melt-freeze crust exists at treeline and an isothermal trend exists below 1100 m.

Cornices along ridgelines are large, and the likelihood of them failing will increase when the sun comes out.

Terrain and Travel

  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Be aware of highly variable recent wind loading patterns.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.

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.