Avalanche Forecast
Issued: Mar 19th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Deep Persistent Slabs and Loose Wet.
lbaker,
Avalanche Canada
A layer of buried surface hoar is increasing reactivity and propagation in wind loaded features.
Watch for signs of instability increasing with daytime heating. Back off slopes as the surface becomes wet or moist from solar input.
Summary
Confidence
Moderate
Avalanche Summary
On Saturday, a few natural wind slab avalanches were observed up to size 2 in the alpine. Numerous loose wet avalanches to size 2 were observed in steep, rocky solar terrain and on all aspects below treeline.
On Friday, a size 3, naturally triggered, deep persistent slab avalanche was reported in the Stikine area, on a south facing slope at 1300 m. This avalanche occurred on the basal facets, up to 250 cm deep, likely triggered by a combination of warm temperatures and sun effect.
Snowpack Summary
Southwest winds have built wind slabs on north to east facing terrain features near ridge top. A melt freeze crust or moist snow exists on the surface at low elevations and on sun affected slopes.
A weak layer of surface hoar is found 10-25 cm down in sheltered terrain. On solar aspects, this layer appears as a melt-freeze crust.
The middle of the snowpack is strong and contains numerous hard crusts.
The lower snowpack is composed of weak basal facets. This layer has produced limited recent avalanche activity, however it can quickly become active again with any significant change to the snowpack, such as rapid loading (heavy snowfall or rain) or prolonged and extensive warming. Avoiding thin and rocky slopes is still recommended.
Weather Summary
Sunday Night
Partly cloudy. Strong southeast winds at ridgetop. Treeline temperature -1°C. Freezing levels remain around 1300 m through the night.
Monday
Mainly sunny. Strong southeast winds at ridgetop. Treeline temperature 0°C. Freezing levels 1500 m.
Tuesday
Mix of sun and cloud. Moderate southwest winds at ridgetop. Treeline temperature 0°C. Freezing levels 1500 m.
Wednesday
Mix of sun and cloud with isolated flurries, 1-2 cm accumulation. Moderate west winds at ridgetop. Treeline temperature -4°C. Freezing levels 1000 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
- Minimize exposure to sun-exposed slopes when the solar radiation is strong.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Problems
Wind Slabs
Storm snow has been redistributed by switching winds into deeper deposits in exposed alpine and treeline features.
A buried layer of surface hoar is increasing reactivity and propagation. Avoid sheltered and shaded slopes where surface hoar is more likely to be found. On other aspects this layer is present as a melt freeze crust which has also produced avalanche activity.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
Weak, sugary faceted grains exist near the base of the snowpack. Riders are most likely to trigger this layer on steep, rocky slopes where the snowpack is shallow. The likelihood of avalanche activity on this layer will increase during periods of rapid change to the snowpack, such as heavy snowfall, rain, or rapid warming. Cornices are also very large at this time of year and a cornice failure could trigger this layer.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
With freezing levels remaining elevated overnight watch for an increase in avalanche hazard when the sun directly impacts slopes tomorrow. Pinwheeling and recent avalanches are signs of a weakening upper snowpack.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 20th, 2023 4:00PM
