Avalanche Forecast
Issued: Feb 27th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
wlewis,
Avalanche Canada
New storm snow will take time to bond and gain strength with layers below, expect increased reactivity in wind affected areas.
The lower snowpack remains weak, small avalanches may easily step down to deeper layers. Keep a large margin of error by avoiding thin start zones and large slopes.
Summary
Confidence
Avalanche Summary
On Sunday natural and human triggered avalanches were observed to size 1.5, primarily on north and east aspects at higher elevations. On Saturday, a size 1.5 machine triggered persistent slab avalanche was reported from a shallow alpine feature that had previously been controlled.
Earlier in the week during heavier precipitation, slab avalanches were reported to size 3 from natural and human triggers. Poor visibility has limited observations so far, we expect more widespread avalanche observations to be reported soon.
Deep persistent slab avalanches continue to be periodically reported throughout the region. This MIN post from Thursday observed a size 3 avalanche near Golden over 1 m deep. A very large fatal avalanche occurred on February 16th - while this was over one week ago, the snowpack structure and likelihood of triggering has not changed.
Snowpack Summary
Up to 20 cm of low density recent storm snow sits over wind affected surfaces. Expect deeper deposits on north and east facing slopes, from southwest winds.
Buried surface hoar sits 30-50 cm deep in sheltered terrain features, and a thin sun crust exists at the same depth on steep south-facing terrain.
The lower snowpack contains a number of buried weak layers such as surface hoar with variable distribution, as well as a widespread layer of large, weak basal facets and depth hoar in some areas. These weaknesses have been responsible for a number of recent very large, destructive avalanches and will continue to be a concern.
Weather Summary
Monday Night
Partly cloudy with isolated flurries, 2-4cm. Light southwesterly wind. Freezing levels valley bottom.
Tuesday
Mainly cloudy with isolated flurries, up to 4 cm. Light and variable winds. Freezing levels valley bottom, alpine high of -9 °C.
Wednesday
Mix of sun and cloud. Light westerly wind. Alpine high of -8 °C. Freezing levels 500 m.
Thursday
A mix of sun and cloud with freezing levels rising to 1000 m. Alpine highs reach -3°C. Moderate to strong southwest winds. Light snowfall possible.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
- Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
Problems
Storm Slabs
Moderate winds and 10-20 cm of storm snow have built reactive slabs at higher elevations. Storm snow may sit over a layer of surface hoar in sheltered terrain features, or over a sun crust on south facing slopes which may increase reactivity.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
The base of the snowpack remains very weak. Very large human triggered avalanches are possible at higher elevations. Avoid shallow and rocky areas, where the snowpack varies rapidly from thick to thin.
The mid and lower snowpack also contain several surface hoar layers. Due to the overall weak snowpack structure, small avalanches are likely to step down to any of these deeper weak layers creating large and destructive avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 28th, 2023 4:00PM
