Avalanche Forecast
Issued: Jan 19th, 2020 3:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet and Deep Persistent Slabs.
ghelgeson,
Avalanche Canada
It's incredibly difficult to forecast what will happen with dramatic warming and sun. Potentially large cornice failure and loose wet avalanche activity is likely to be widespread, probably best to avoid avalanche terrain Monday as the snowpack feels the heat for the first time.
Summary
Confidence
Low - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack. Uncertainty is due to rapidly fluctuating freezing levels.
Weather Forecast
Warm air invades the region Monday pushing the temperature to near zero from valley bottom all the way up to 3000 m with just a few clouds and strong southwest wind. Tuesday and Wednesday are still warm with the freezing level hanging out around 1500 m.
SUNDAY NIGHT: Freezing level at valley bottom, moderate to strong west/southwest wind, trace of snow possible.
MONDAY: A few clouds at dawn with clear skies in the afternoon, air temperature warming to near 0 C as high as 3000 m, light southwest wind at lower elevations, strong southwest wind at ridgetop, no significant precipitation. Freezing level returning to valley bottom Monday Night.
TUESDAY: Broken cloud cover, freezing level rising from valley bottom to about 1500 m, light southwest wind at lower elevations, strong southwest wind at ridgetop, 1 to 2 cm of snow possible at upper elevations with potential for light rain down low.
WEDNESDAY: Scattered cloud cover at dawn with clear skies in the afternoon, light southwest wind at valley bottom with strong west/northwest wind at ridgetop, trace of precipitation possible.
Avalanche Summary
No new avalanche activity to report from Saturday.
On Friday wind slab avalanches to size 1 were sensitive to control work on a southeast facing ridge crest around 2000 m. Small natural avalanches were also observed on steep rolls.
On Thursday a natural size 2 wind slab stepped down to the deep persistent basal facets below a rock band, details here. Â
Snowpack Summary
Recent snow has been loaded into pockets of soft wind slab in alpine lees, and is settling in the mild alpine temperatures. At lower elevations it may remain unconsolidated.Â
A well consolidated mid-snowpack overlies a generally weak basal snowpack. The bottom 10-20 cm of the snowpack consists of facets and deteriorating crusts. There is potential for this deep persistent layer to reawaken as temperatures warm on Monday.
Terrain and Travel
- Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
- Be aware that wet activity at low elevations is a classic situation for step-down failures in deeply buried persistent weak layers.
- A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
- Avoid exposure to sunny slopes, especially in the afternoon.
Problems
Loose Wet
Monday is going to be quite warm and sunny which is likely to initiate a loose wet avalanche cycle. Cornice failure could be a very serious hazard on Monday too. Once you start seeing roller balls and pinwheels loose wet avalanche activity is imminent.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
As temperatures trend warmer in the alpine Monday we are concerned about the deep basal facets reawakening in the form of large destructive natural avalanches. Deep persistent slab avalanches on these layers are most likely to be triggered from shallow snowpack areas near rocky outcroppings.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 20th, 2020 5:00PM
