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Avalanche Forecast

Archived

Apr 28th, 2015–Apr 29th, 2015

Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.
Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.
Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.

Regions

Glacier.

A good plan is to avoid the backcountry until things cool down. Temperatures have already soared well into the positive values at 2100m this morning. The deterioration of the snowpack will be very rapid today combined with the weak overnight freeze.

Weather Forecast

Warm air ahead of a cold front will give us our highest freezing levels today reaching ~3200m. A Pacific system will be making its way inland by late tonight into Wednesday giving moderate amounts of precipitation, freezing levels will lower to around 1750m. Alpine winds will pick up to 30-50km/hr from the southwest.

Snowpack Summary

Another weak overnight freeze. The crust has been thinner between 1600-2000m and will break down faster there than at lower elevations. The April 10 layer is down 30-60cm. Moist snow will almost certainly be found on most aspects and elevations. Any dry snow that could be found in high alpine north aspects will be come moist by later today.

Avalanche Summary

2 loose wet avalanches observed in the highway corridor yesterday.

Confidence

Problems

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.