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Avalanche Forecast

Archived

Mar 22nd, 2016–Mar 23rd, 2016

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

Regions

Little Yoho.

Overcast skies on Wednesday should mitigate the effect of the sun, but warm temperatures in the valley bottoms remain a concern. Field ice climbers - go early and be done by noon - this time of year the sun bakes the slopes above the routes by 12:00.

Weather Forecast

Overcast skies and light now forecast for Wednesday with temperatures remaining in the -5 to -10 range as long as the sun doesn't come out, and light winds. This time of year it only takes a short burst of strong sun to have an influence on the snowpack - but right now it looks like Wednesday will be a pretty benign day in the mountains.

Snowpack Summary

Dry snow on shaded slopes above 1800m, but otherwise expect surface crusts in most locations. In the top meter of the snowpack, several buried suncrusts exist and are a concern on west, south and east aspects. Generally the snowpack is well settled, but we remain concerned for buried crusts and afternoon wet snow avalanches on the Field ice climbs.

Avalanche Summary

No new avalanches observed or reported today in the Little Yoho region - we did close the Field back road in anticipation of afternoon wet snow avalanches running down near Guiness Gully, etc. It reached 13 degrees down in Field on Tuesday - but Wednesday should be cooler and overcast.

Confidence

Due to the number and quality of field observations

Problems

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.