Full disclosure or true confessions, I love the Cascades so much my wife considers herself a widow from Mid-March to Memorial Day. The Spring Equinox means longer days, a settling snowpack and longer tours. In the Northwest we look to the high alpine for long descents off the volcanoes, touring into the North Cascades and Olympics as road access opens up previously remote destinations. High alpine traverses get done under long sunny days so what is the catch? Avalanches, very dangerous avalanche conditions that surprise us when we were expecting to reap the rewards of a long winter. The factors that catch us center around our decision making and communication regarding our ability to actually see the transitional nature of the snowpack and our willingness to take more risk under warm, sunny skies.
Human Factors dominate because recent accidents in Washington and Colorado show high levels of education do not keep people from making mistakes. Errors that go beyond the actual hazard occur when trust creates the sense that everyone is thinking the same thing. People describe complete trust as not requiring communication, which does not
work in a complex environment such as a transitioning snowpack from winter to spring in challenging or complex terrain. The wide range of variables requires everyone to express both their personal and environmental observations. This free exchange of information keeps everyone engaged in risk management, which increases trust, not undermine it.
The other error educated and experienced people make (aka, the Confidence Curve) is not recognizing that their actual experience may not include extraordinary conditions that exceed what they have witnessed before. If you toured for 2-4 seasons and rode a variety of terrain, you may not have witnessed remote triggering, deep slab releases and surface hoar human triggered D 2.5 or larger avalanches. This relates to the confidence curve, which is reset when one actually experiences one of these events. One of these avalanches usually surprises us by exceeding what we anticipated the terrain could produce or that we triggered something that big and destructive. Hopefully this only results in a near miss or minor injuries and a brand new awareness of what is possible.
The Ides of March bring a whole new level of stress to the winter snowpack in the form of Solar Radiation. The heat of the longer days and more direct solar input into the snowpack add stress the surface as well as the mid-pack as melt water percolates into older layers and breaks down bonds. The initial period when the winter snowpack still holds variation of layers and temperature struggles with the rapid addition of heat.
Spring rain provides another dose of heat and stress to the snowpack and alters stability rapidly. Showers can arrive with warm air and transform lower elevation areas into dangerous isothermal conditions where the entire snowpack loses cohesion. New Snow Avalanches, Wet Loose Snow Avalanches, and Deep Wet Slab Avalanches (Climax slides) all occur due to the increase of heat from rain and sun.
Timing becomes an important part of your travel plan as the South/Southeast aspects heat up in the early am and can begin shedding by 10:30-11 and continue around to the southwest aspects by early afternoon. In the Rockies, spring storms bring warmer, denser snow that adds larger loads to fragile snowpack creating the threat of large avalanches like the Sheep Creek slide at Loveland, CO.
High alpine descents and traverses require good timing and a reasonable weather window to avoid increasing avalanche hazard preventing you from returning to the valley safely. Icefalls occur on glaciers, a result of glacier motion. They are triggers for large and deep avalanches as the ice can weigh thousands of pounds and fall great distances onto slopes below. It can snow in the alpine zone (above tree line which varies from the coast to the Rockies) year round. White outs increase the hazard with loss of visibility so trip planning is essential for high alpine adventures.
Options and several exit routes become a necessary part of your planning. I often look at my objectives and select several on both sides of the Cascade Crest to use the rain shadow to give me a bad weather option if the weather looks warm and wet.
The equipment necessary to tour in the spring includes several items that help manage the melt/freeze surface conditions.
• Ski Crampons-allow you to engage the skins on firm crusts and continue to skin versus continuing on foot.
• Boot Crampons-allow you to climb in the early am on glacial terrain and firm snow safely.
• Ice axe-for terrain steeper than 35 degrees one axe is necessary to ensure you have a tool capable of swinging into ice or neve.
• Whippets-work and are optional as they do not completely replace an axe as stated above.
• GPS-recommended for long trips above treeline.
The avalanche danger exists well into spring and we all need to remain attentive to the same issues with our decision-making. We need to understand we will never know everything and trust improves conversation, not negate it.