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Avalanche Forecast

Archived

Apr 12th, 2015–Apr 13th, 2015

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

Regions

Northwest Inland.

This forecast was produced with very few field observations.  If you have back-country information you would like to share, here, we'd love to hear from you.

Confidence

Fair - Due to the number and quality of field observations

Weather Forecast

Chance of flurries today, with the freezing level near 1000m for the high today. Wind at ridge tops light from the SW. MONDAY:  cloudy with flurries, wind from the South, and the freezing level may climb to 1200m during the day.TUESDAY: A break in the weather, cloudy with some sunny periods, freezing level around 1000m, LIGHT wind from the SW.WEDNESDAY:  Cloudy with flurries, possible 5cm of snow.  Freezing level around 1200m and winds light to moderate from the South West.

Avalanche Summary

No reports of natural avalanche activity yesterday, most likely because of few observations during this storm, but one operator recently reported good results, up to size 2.5, with explosives in wind loaded terrain.

Snowpack Summary

What new snow we have received has been blown into wind slabs on exposed lee slopes. The main concerns right now are wind slabs over a variety of surfaces that include crusts, facets and surface hoar that formed in in sheltered places during the last spell of clear cool  weather.  Large ripe cornices are also of concern and will be a problem with additional loading, especially when the sun and warm temperatures come back.   The March 25th crust with facets appears to be inactive, but is worth  keeping in mind.

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.