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Avalanche Forecast

Archived

Mar 18th, 2023–Mar 19th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

North Columbia, South Columbia, Esplanade, Jordan, North Selkirk, Shuswap, Badshot-Battle, Central Selkirk, Goat, Gold, Kokanee, North Okanagan, Retallack, Valhalla, Whatshan.

30-50 cm thick storm slabs formed earlier in the week may continue to be reactive to human triggers in specific locations at upper elevations.

Minimize exposure to sun-exposed slopes when the solar radiation is strong.

Confidence

High

Avalanche Summary

A remotely triggered size 2 storm slab avalanche was reported on a north aspect in the alpine on Friday. The slab was 30-40 cm deep and failed on a crust. See MIN.

Additionally, one natural and numerous explosive triggered cornice falls up to size 2.5 were reported on north aspects in the alpine. Most of them did not trigger slabs on the slopes below.

Snowpack Summary

Expect to find a melt-freeze crust on the surface of all aspects at treeline and below and on sunny aspects in the alpine. Solar radiation will break down the crust on sunny slopes throughout the day.

Strong solar radiation has settled the 30-50 cm of recent snow into a storm slab which has remained reactive to human triggers in specific locations at upper elevations.

Strong southwest wind during the storm earlier in the week added to slab formation on lee aspects at treeline and above.

The recent snow is sitting on a variety of surfaces. These include sun crust on sunny aspects and surface hoar (3-10 mm) on some shady and sheltered slopes.

The mid-snowpack is generally strong but the lower snowpack is a different story..

The November facets are still prominent at the base of the snowpack. They are showing signs of improving but this layer remains a significant concern in rocky, shallow, or thin to thick snowpack areas at treeline and above.

Weather Summary

Saturday Night

Clear skies / 10 km/h east ridgetop wind / Temperature at treeline around -8 C / Freezing level valley bottom

Sunday

Sunny / 20 km/h east ridgetop wind / Temperature at treeline around -1 C / Freezing level 1800 m

Monday

Mix of sun and cloud / 10 km/h east ridgetop wind / Temperature at treeline around -3 C / Freezing level 1700 m

Tuesday

Mostly sunny / 10 km/h east ridgetop wind / Temperature at treeline around -5 C / Freezing level 1500 m

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • Cornice failure may trigger large avalanches.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.