Winter is getting well underway in the Northern Hemisphere. There is always the excitement of seeing the new snow on the ground, blanketing the trees and buffing the mountain slopes into a winter playground. This excitement manifests with avid backcountry skiers and riders searching for the first snow adventures of the winter.
It is important to temper that enthusiasm with a realistic analysis of the risk for any backcountry sojourn and plan the trip in accordance with a specific formula so that all controllable factors are recognised and mitigated.
Make sure you read and understand the Avalanche Bulletin for the area you intend to visit
Part of this preparation for any backcountry ski tour is reading and understanding the latest avalanche bulletin for the region you plan to visit. There is now more continuity in reports internationally, making it easier for visiting backcountry users to understand local assessments. However, differences do occur and it’s important if you are outside of your usual avalanche forecast location to recognise this.
Here we will take a basic look at how to read an Avalanche Bulletin. Remember this does not substitute in any way for avalanche education and alone the avalanche bulletin gives you only one piece of a complex puzzle when deciding on whether to head into the backcountry for your ski trip. Here at Intrepid Medical Conferences, we advise you take a course endorsed by your National Avalanche Association.
Intrepid Medical Conferences Medicine in the Mountains 2019 is being held in SilverStar Mountain Resort BC Canada. This lies in SilverStar Provincial Park, on the southern end of what is known as the Shuswap Highland. This non-contiguous foothill region leads west and northward to the Monashee Mountains, a branch of the Columbia Mountain Range. We will continue our discussion focussing on this area.
For this exercise, we will assume the ski tour goals are a to ski a gladed forest area that is not within any patrolled ski area boundary.
So if we go to www.avalanche.ca we can find Silverstar Provincial Park lies in the South Columbia forecast region. There is a brief summary for each region here, but we want more detail.
Looking at the at the region overview we can see the danger ratings for below treeline, treeline and alpine. “Treeline” is that relatively narrow subalpine zone where sporadic trees exist, being the transition from the gladed below treeline and the alpine environment.
Let’s assume the area we plan to ski is treeline and below. The rating is “low” (green) below treeline and “moderate” (yellow) at treeline.
You can scroll down to refer to see “danger ratings explained”.
The definition of moderate is:
“Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Natural avalanches unlikely; human-triggered avalanches possible. Small avalanches in specific areas; or large avalanches in isolated areas.”
Now we want to know what type of Avalanche Risk exists in more detail.
Click on the “Problems” section. For the date in question in the South Columbia Region, only one significant problem exists: wind slabs.
(At times there may be 2 or more problems, for example, wind slabs on North slopes and soft snow avalanches on southern sun-exposed slopes. )
These wind slabs can be expected at and above treeline (mountain diagram at left), on slopes facing northwest through to southeast (“which slopes” rose). Size 1-2 avalanches may possibly be triggered (“chances of avalanches” and “expected size”). These are small slabs forming due to light snow deposition with a prevailing southwest wind.
There is an additional brief travel advisory related to that avalanche problem, in this case analysing for wind redistribution and avoiding wind loaded pockets.
The next section of the bulletin is “Details”.
Here you can find an extensive report detailing observed avalanche activity, snowpack observations and a weather activity/forecast for the region. This is the deconstructed hard data from which the avalanche forecaster/s have prepared the rating scale and forecast.
As Avalanche Canada note “there is no simple or clear-cut formula as the knowledge, judgment, and intuition of the forecaster are the primary tools used in this process.”
From the “Details” section for our trip, we can see that the snowpack is in a phase of settling somewhat. After a recent storm cycle, the non-wind loaded new snow seems to be bonding well to the old layers. There still persists risk of slab release in those loaded areas however.
In addition, there is a persistent buried weak layer, and although it seems to be becoming more supportive, the forecasters feel a strong force may trigger it to release. The slopes at higher risk for this occurring at or below treeline would be steep North and East facing slopes.
It is important to note that in the weather forecast on that Avalanche Bulletin, a new storm was predicted to arrive within 24 hrs.
The snowpack can and does change over time.
The snowpack changes over time, and this can occur rapidly. The more obvious situation is during a storm cycle when increased loading from precipitation and /or wind may elevate the danger scale considerably.
Of interest here is what happened to the next days forecast as a case in point:
Another limitation to a forecast is the spatial differences in snowpack stability. Within any forecast region, there may at the same elevation and aspect be differences in the snowpack not reflected in the bulletin. As iterated earlier, the bulletin is an overview and alone is insufficient to make assessments of avalanche risk.
That is where education, knowledge and experience are required to REASSESS the situation in real time on site, irrespective of the forecast.
So we now have an overview of the forecast for the snow stability in the region we plan to ski. We then need to consider a host of other factors in planning our backcountry trip, including an evaluation of the proposed participants, the degree of terrain complexity we intend to ski, and so on.
We have created a Snow SAFETY Risk Assessment Checklist. Make it a Habit to go through these seven simple steps every time before you head out to the backcountry. Think of it as your own personal aide memoire.
Remember, before going into the backcountry, ensure you and your team has sufficient knowledge and experience for the undertaking. Use the Free Snow SAFETY checklist. Take an endorsed avalanche course as a starter.
Stay safe in the hills.