Avalanche Forecast
Issued: Mar 13th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Cornices, Persistent Slabs and Loose Wet.
ldreier,
Avalanche Canada
We are expecting another hot day and temperatures will stay above freezing in the alpine overnight. The warmth will weaken cornices and may increase the reactivity of the persistent weak layers. Conditions may change rapidly with daytime heating and sun exposure.
Summary
Confidence
Moderate - Uncertainty is due to whether buried persistent weak layers become active, triggering avalanches, with the arrival of the forecast weather. Uncertainty is due to the fact that cornice falls are particularly difficult to forecast.
Weather Forecast
SATURDAY NIGHT: Clear, 30 km/h south wind, alpine low +1 C, above freezing layer between 1500 and 2700 m.
SUNDAY: Sunny, 20 km/h southwest wind, alpine high +7 C, freezing level 2500 m.
MONDAY: Mostly sunny, 20 km/h northeast wind, alpine high +6 C, freezing level 2300 m.
TUESDAY: Mix of sun and cloud, 15 km/h northeast wind, alpine high +5 C, freezing level 2200 m.
Avalanche Summary
A couple natural slab avalanches of size 2 were observed on sun-exposed slopes on Saturday as well as numerous small wet loose avalanches up to size 1.5 on steep solar features in the alpine. A few small avalanches were reported on east aspects on Friday. A few small loose and slab avalanches were triggered on sun-exposed slopes in the alpine during the heat of the day on Wednesday.
Snowpack Summary
A thick melt-freeze crust is present in many areas, with the exception being on north aspects above around 1700 m. Wind slabs may still exist on northerly aspects at alpine and treeline elevations. On solar aspects and below the freezing level, the snow will moisten during the heat of the day. Cornices will also weaken over the day.
Around 30 to 50 cm of snow overlies a variety of old interfaces that formed in mid-February. There hasn't been recent avalanche activity on this layer, but it remains possible to be triggered where it exists. The more active layer was buried late January, which is found 50 to 100 cm deep. This layer is mostly composed of sugary faceted grains, hard wind pressed snow, feathery surface hoar in wind-sheltered locations, and a melt-freeze crust on steep solar aspects. Periodic avalanches continue to be triggered on this layer. Check out this MIN for a photo of the positioning of these layers in the snowpack.
Terrain and Travel
- Cornices become weak with daytime heating or solar exposure.
- Cornices often break further back than expected; give them a wide berth when traveling on ridgetops.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
- Be alert to conditions that change throughout the day.
Problems
Cornices
Cornices will become weak with daytime heating and the freezing level staying at 2700 m overnight. Large cornice falls are a hazard of their own and can also trigger large persistent slab avalanches on the slopes below.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine.
Likelihood
Expected Size
Persistent Slabs
Two weak layers may exist between 30 and 100 cm deep. Widespread avalanche activity has already occurred on the layers, but they could still be triggered anywhere they haven't already failed. Look for signs of instability and continue treating the snowpack as suspect if you are uncertain whether the layer is still present in your riding area. The warm temperatures may increase the reactivity of these layers.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Solar input and warm temperatures may weaken the upper snowpack and form wet loose avalanches. These avalanches will most likely occur on steep solar slopes and around rock outcrops. The likelihood for wet loose avalanches will increase with daytime heating. Pinwheeling and a moist snow surface are signs that the stability of the upper snowpack is decreasing.
Even small avalanches can be a hazard in high consequence terrain and above terrain traps.
Aspects: South East, South, South West.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 14th, 2021 4:00PM
