Avalanche Forecast

Archived

Apr 18th, 2023–Apr 19th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

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

South Rockies, St. Mary, Bull, Elkford East, Elkford West.

Dial back your terrain choices where you are finding more than 20 cm of new snow. Avoid wind loaded areas where slabs are deeper, more cohesive, and are likely reactive to human triggering.

Confidence

Low

Avalanche Summary

No new avalanches were reported in this region on Monday.

We expect backcountry users will see evidence of a large avalanche cycle from last week's rain event when numerous wet loose avalanches reached the valley bottom.

If you head out in the backcountry, let us know what you are seeing by submitting a report to the Mountain Information Network.

Snowpack Summary

In the alpine and around treeline, 20-40 cm of snow covers a frozen crust.

The mid snowpack is generally settled and strong, except in areas with snow depths less than 150 cm. In these lower snow areas, the mid-pack is likely weaker and more faceted.

The lower snowpack includes a layer of large, weak facets and/or depth hoar crystals.

Below treeline, expect to find moist or refrozen surfaces, and a shrinking snowpack that is isothermal during the heat of the day.

Weather Summary

Tuesday Night

Cloudy with scattered flurries. 3-9 cm of snow is expected in the alpine. Light northerly ridgetop wind. Freezing levels fall to 1000 m. Treeline high around -5 °C

Wednesday

The Elkford region is forecast to be cloudy with scattered flurries, 10-20 cm of new snow in the alpine.

In the Purcells and Bull area, 2-3 cm of new snow is forecast.

Both regions will see light northwest ridgetop wind. Freezing levels of 1500 m and treeline highs around -1 °C.

Thursday

Mainly cloudy with sunny periods and isolated flurries, trace accumulations. Light west ridgetop wind. Freezing level at 1700 m. Treeline high around -1 °C.

Friday

Mainly sunny with cloudy periods. Light southwest ridgetop wind. Freezing level at 2000 m. Treeline high around 0 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Watch for changing conditions today, storm slabs may become increasingly reactive.
Be carefull around freshly wind loaded features.
Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
If triggered, storm slabs in-motion may step down to deeper layers and result in very 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.