Avalanche Forecast
Issued: Jan 23rd, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Persistent Slabs and Deep Persistent Slabs.
Mark Herbison,
Over the last week there have been periodic, very large, avalanche events involving the Dec 1st layer, which is a bit unsettling. This is a low probability / high consequence problem that will be lurking in the snowpack for the rest of the season.
Summary
Weather Forecast
The upper ridge of high pressure will break down, collapsing the temperature inversion, bringing freezing levels back down to valley bottom. Monday will see mainly cloudy skies with isolated flurries and sunny periods. Freezing level up to 1400m with an alpine high of -6 and 15-35km/hr North Westerly winds. No 'real' snow amounts in the forecast.
Snowpack Summary
Up to 35cm of recent snow now buries the Jan 20th (2-4mm) surface hoar. The Jan 11 (2-5mm) surface hoar is down ~70-90cm. The Dec 1 crust/facet combo is down ~1.5 - 2.5m. Widespread wind affect at tree line and above with pockets of wind slab.
Avalanche Summary
Avalanche Control on Sunday produced results up to size 3, one of which stepped down to the Dec 1st layer. Skiers were trigger small wind slabs up to size 1.5 on steep rolls.
Avalanche Control on Saturday, just West of the Park produced several size 4 - 4.5 avalanches, extending historical trim lines through mature timber.
Confidence
Problems
Wind Slabs
Moderate to strong winds on Sunday were likely building fresh wind slab in the Alpine and down into tree line. These may have buried surface hoar or a preserved stellar layer and could be sensitive to human triggering.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
- Convex features and steep unsupported slopes will be most prone to triggering.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
This layer has been recently active and in some instances has been enough to step down to the deeper Dec 1 curst/facet layer. Investigate the snowpack before committing to your line.
- If triggered the persistent slabs may step down to deeper layers resulting in very large avalanches.
- Be wary of slopes that did not previously avalanche
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
The Dec 1 crust/facet layer woke up this past week, resulting in numerous very large avalanches This is now a low probability / high consequence avalanche problem. It will be stubborn to trigger, but if it goes the results will be very large.
- Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.
- Avoid thin, rocky or unsupported slopes.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 24th, 2022 4:00PM
