Regions
Vancouver Island.
A few loose wet on steep south were observed during daytime observation flight over 5040 and Mount Arrowsmith. Additionally widespread wind effect was evident on all upper alpine terrain. Cornices remained intact and are large and looming.
No new avalanche observations were summitted or observed in the norther zone of the forecast region.
Past Weather
This weekend continued with winter weather, cool temperatures and between 20 and 30 cm's of new snow all combined with moderate to strong south wind.
Weather Forecast
A ridge of high pressure will introduce warm air, provide clear sky and sunshine for the entire forecast period. Expect freezing levels and temperature to continue to rise daily.**Monday:** No new precipitation Winds light from the North East , Freezing levels at sea level rising during the daytime to 1600 meters. Temps at 1500 meters up to 1 degrees.**Tuesday:** No new precipitation, Winds light to moderate from East North East, Freezing levels 1800 meters. Temps at 1500 meters 3 degrees.**Wednesday:** No new precipitation, Winds light from the East North East, Freezing levels 2800 meters. Temps at 1500 meters 7 degrees.
Terrain Advice
**Please respect the current closures at Mount Washington, no access is permitted at anytime on the ski areas slopes or terrain.**During periods of intense warming and sunshine avoid solar aspect terrain.Avoid travelling both above and below cornices.
Snowpack Summary
New snow between 20 and 30 cm overlies a previously well developed surface crust. Warming daytime temperatures and moderate settlement of this new snow has promoted bonding of this new layer of snow. Highly wind effected upper alpine areas and continued cornice growth is evident. Expect in lee areas that wind slab depths could easily exceed a meter. The mid and lower snowpack are well settled and dense. Forecast temperature values are expected to rise rapidly and overnight cooling and snowpack recovery (refreeze) will begin to diminish. With these factors, the snowpack will begin to rapidly settle and is likely to become during the height of the warmth, very unstable. Expect cornice collapse, glide slab failures, waterfall ice failures and perhaps other anomalous geo hazard events to occur as the mountains are going to see a rapid change from winter conditions to near summer like conditions in a 72 hour period.
Snowpack Details
- Surface: Variable surface conditons dependant on aspect and elevation.
- Upper: Reactive crusts at 30 cm and 100 cm
- Mid: Well settled and dense.
- Lower: Well settled and dense.
Confidence
Moderate - Weather forecast models are very well aligned and provide support to forecast avalanche problems. **Avalanche danger ratings reflect the highest danger level expected over the course of the day.**
Problems
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.