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Avalanche Forecast

Archived

Apr 28th, 2014–Apr 29th, 2014

Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.

Regions

Little Yoho.

Tuesday will be an excellent day. A good freeze is expected on Monday night followed by a sunny, cool day on Tuesday. BUT, on Wednesday the warm air arrives with freezing levels to 3500m. The first big warm up day usually produces an avalanche cycle.

Weather Forecast

Clear skies and a low of -10 on Monday night followed by a sunny day on Tuesday with highs of 4. Tuesday is the day to get out there! Wednesday we finally get the big warm up we've been waiting for, with freezing levels expected to reach 3500m, and going higher on Thursday. Highs on Wednesday to  12 degrees, with valley bottoms in the upper teens.

Snowpack Summary

All areas of the park have a strong melt-freeze crust up to about 2400 meters, slightly bit lower on north aspects. Above that, dry snow persists with up to 20 cm of settled powder in shaded areas. Isolated, small windslabs exist in leeward areas in the alpine. Temperatures on Monday of -9 at 3000 m and a light north wind kept the snowpack stable.

Avalanche Summary

No new avalanches were observed or reported on Monday.

Confidence

on Wednesday

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.