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Avalanche Forecast

Archived

Feb 19th, 2023–Feb 20th, 2023

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

Regions

Lizard-Flathead, South Rockies, Flathead, Lizard, Elkford East, Elkford West.

The reactivity and size of storm slabs will increase throughout the day. Use extra caution in wind-exposed terrain and south-facing terrain where a melt-freeze crust has recently been buried.

A weak layer of basal facets remains a concern in shallow snowpack areas. Avoid high consequence avalanche terrain in these areas.

Confidence

Moderate

Avalanche Summary

On Saturday, several natural and skier-triggered size 1 loose dry avalanches as well as a few small pockets of wind slab. Last week, a couple of bigger wind slabs were reported including this MIN post and this MIN post.

The deep persistent slab problem continues to be a concern for parts of the region. In the nearby Bull River area, this very large older avalanche was observed on Friday by the Avalanche Canada field team which is expected to have occurred on Wednesday.

Snowpack Summary

New snow will bury an upper snowpack that is heavily wind affected in exposed terrain. While a sun crust on the southern aspects has been buried by the recent snowfall.

The middle of the snowpack is well consolidated and sits on a thick crust. The bottom of the snowpack still consists of weak, sugary crystals that are slowly gaining strength in areas with a deeper snowpack.

Deep persistent slab avalanches should still be on your radar in thinner snowpack areas outside of the Lizard Range such as the Elkford area, and the Flathead range.

Weather Summary

Sunday night

Cloudy with light snow, 2 to 10 cm. Moderate westerly alpine winds. Treeline temperatures around -5 C.

Monday

Snowfall continuing through the day, 5 to 15 cm. Light to moderate westerly alpine winds. Treeline temperatures 0 to -5 C.

Tuesday

Cloudy with periods of heavy snow, 10 to 30 cm. Moderate northeast alpine winds. Treeline temperatures drop throughout the day from around -5 to around -20 C by day's end.

Wednesday

Cloudy with sunny periods and trace snow amounts. Moderate northeast alpine winds. Treeline temperatures -20 to -25 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for fresh storm slabs building throughout the day.
  • Expect slab conditions to change drastically as you move into wind exposed terrain.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.