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Avalanche Forecast

Archived

Apr 11th, 2015–Apr 12th, 2015

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

South Coast.

The hazard may go higher than forecast if precipitation amounts are greater than expected. If you have field observations to share here, we'd love to hear from you.

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The cold front has passed through the area leaving cool unsettled conditions.  Expect convective showers over the next few days.SUNDAY:  A cool unstable air mass will continue to bring precipitation to the region overnight Saturday and Sunday. 10 to 15cm of precipitation, freezing level around 110 m and winds moderate to strong from the South West.MONDAY:  Cloudy with flurries and/or rain.  Freezing level will rise to 1600m and moderate to strong winds from the South West.TUESDAY:  A brief break in the weather pattern. Cloudy with sunny periods, freezing level around 1200m, winds light to moderate from the South West.

Avalanche Summary

No reports of avalanche activity from yesterday.  This is most likely as a result of few field observations. We expect wind slab activity with new loading and strong winds.  Solar aspect may become active again when the sun come out.

Snowpack Summary

20 to 30cm of storm snow now rests on a variety of crusts and old surfaces including surface hoar and facets that formed in sheltered locations during the recent clear weather. Moderate to strong south west winds are redistributing the storm snow into wind slabs on the lee sides of ridge tops. A facet/crust layer that was buried in mid-March is now approximately 50-100 cm down.  This remains a concern in the region because of it's potential for very large avalanches. Cornices are now large and mature and may collapse with increased loading, possibly triggering the deeply buried weak layer.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.