Avalanche Forecast

Archived

Jan 7th, 2023–Jan 8th, 2023

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Glacier.

The persistent weak layers are most likely to be triggered from shallow, rocky areas. Do your best to avoid these locations.

The snowpack is thin, the alders are tall and rocks are still hard. Regardless of these facts, good snow quality still exists in Rogers Pass.

Confidence

Moderate

Avalanche Summary

No human-triggered avalanches reported within the last few days.

MacDonald Gully 8 produced a sz 1.5 wind slab avalanche on Saturday.

On Thursday, the Macdonald gullies produced several large avalanches during a brief wind spike in the morning, notably gully #6 produced a size 3 slab avalanche.

Snowpack Summary

The top 30cm of snow is settling with warmer temps. Wind-affected snow can be found in the alpine and open areas at treeline. Steeper solar aspects have a thin sun crust that is now buried by 5-10 cm.

The December 23rd facet interface is down ~50cm and appears to be gaining strength, but remains a concern in shallow snowpack areas.

The November 17th facet/crust/surface hoar layer is down ~100cm and has become less reactive in snowpack tests, though when it does fail it is 'sudden' in character.

Weather Summary

Sunday will see mainly cloudy skies with up to 5cm of snow accumulation. Ridgetop winds will be 20-35km/hr from the South and the alpine temperature will range from -8 to -3.

5-10cm of snow is forecasted for Monday with a slight drop in temperatures and an increase in winds. Another 5-10cm on Tuesday.

Terrain and Travel Advice

Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.