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Avalanche Forecast

Archived

Apr 21st, 2022–Apr 22nd, 2022

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

Regions

Purcells.

We are getting back into a seasonal spring trend with cool nights, warm days, and highly variable snow conditions with elevation and aspect changes. Be on the lookout for signs that suggest unstable snow.

Confidence

High - The snowpack structure is generally well understood.

Weather Forecast

THURSDAY NIGHT: Cloudy with snowfall in the north of the region, accumulation 2 to 5 cm with local enhancements possible, 10 km/h southwest wind, alpine temperature -5 C.

FRIDAY: Cloudy with snowfall in the north and mix of sun and cloud in the south, accumulation 1 to 3 cm with local enhancements possible, 10 km/h west wind, alpine temperature -3 C, freezing level rising to 2000 m.

SATURDAY: Partly cloudy with afternoon isolated flurries, accumulation trace to 5 cm, 10 km/h northwest wind, alpine temperature 0 C, overnight freeze and daytime freezing level rising to 2300 m.

SUNDAY: Clear skies with no precipitation, 10 km/h southwest wind, alpine temperature 1 C, overnight freeze and daytime freezing level rising to 2400 m.

Avalanche Summary

Wednesday saw small storm slab avalanches triggered in the west of the region at alpine terrain on north to east aspects, where they received up to 40 cm of recent snow. Otherwise, wet loose avalanches were triggered during the heat of the day.

Please consider posting your observations to the Mountain Information Network to supplement our data stream and help fellow recreationists.

Snowpack Summary

Around 10 to 20 cm of snow accumulated since Tuesday in most of the region with local amounts up to 40 cm in the deeper areas in the west. Locally deeper deposits may be found in lee terrain on shaded slopes at treeline and alpine elevations from southwest wind. Sun has moistened the snow on sun-exposed slopes. A consolidated and moist snowpack exists below treeline. At ridge top, remember that cornices are large and looming at this time of year.

Around 100 to 200 cm deep, faceted grains persist around a hard melt-freeze crust from early December. There's uncertainty on if and when this layer will wake up, but it could during the next intense or prolonged warm-up.

Terrain and Travel

  • Carefully evaluate steep lines for wind slabs.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • Make observations and assess conditions continually as you travel.

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.