Avalanche Forecast

Archived

Apr 2nd, 2016–Apr 3rd, 2016

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

Heat related avalanche problems will continue on Sunday. Due to the warm weather, loose wet avalanches will again be possible primarily on steeper solar slopes. Also, be aware of low likelihood/high consequence problems such as cornice failures.

Detailed Forecast

One more day of warm weather is in store for the Pacific Northwest Sunday before we briefly return to winter-like conditions early next week.

Increasing clouds due to an approaching frontal system should curb the loose wet problem in the afternoon in the Olympics.

Melt-freeze crusts can quickly break down in spring sunshine. In areas that have received more recent snowfall, small loose wet avalanches have the potential to entrain deeper layers. Be aware of terrain traps where even a small loose wet avalanche could have unintended consequences. Plan to avoid steep solar slopes by late morning/mid-day to minimize the problem.

Many areas have large cornices along ridge-lines so avoid slopes below these overhead hazards. Unlike the loose wet problem you will not get advance notice that a cornice is about to fail. Cornices can break much further back on ridges than expected and releases can be unpredictable during the spring.

In most areas previous wind slab will have become assimilated into the upper snowpack in the warm weather. The likelihood of triggering older wind slabs should be minimal.

Snowpack Discussion

Weather and Snowpack

A large upper ridge and warm air mass has been over the Northwest several days causing very warm weather. Temperatures on Friday reached into the 50's and 60's F at many NWAC sites on both sides of the Cascade crest including the Olympics. Temperatures on Saturday were slightly cooler but overall conditions remained mild. This weather has been causing a spring avalanche cycle in most areas and has shifted concerns to heat related avalanche problems the past couple days.

The frequent March storms have built unusually large cornices along many ridges, some noted recently in the Hurricane Ridge area.

The mid and lower snowpack in the Olympics should generally be a stable mix of crusts and layers of moist and rounded snow crystals.

Recent Observations

No recent observations have been received from Hurricane Ridge but a natural loose wet avalanche cycle likely occurred on most solar aspects over the past week similar to the Cascades due to the ongoing early spring warmth and sunshine.

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.

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.