Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Overnight and Sunday: Freezing levels dropping down to near valley bottoms overnight and then rising up to about 2200 metres during the day. Chance of some flurries overnight and a few cm of snow in the morning. Expect mostly cloudy skies and moderate Westerly winds during the day.Monday: Freezing levels climbing slightly overnight and then rising up to about 2800 metres during the day. Mostly sunny skies with strong solar radiation and light to moderate Westerly winds. Tuesday: Freezing levels remaining at 2700-2800 metres overnight and through the day. Sunny skies with strong solar radiation and strong Southwest winds. Becoming cloudy in the late afternoon with light precipitation beginning by the evening.
Avalanche Summary
Loose moist avalanches up to size 1.0 were reported that entrained surface snow in the track, but did not step down to deeper weak layers. Forecast warming on Monday and Tuesday with little or no overnight freezing may result in large avalanches stepping down to the February DPWL.
Snowpack Summary
In the Smith Basin area there is 140 cm below treeline and the top 40 cm was found to be moist and well consolidated. The March crust below was decomposing at this location. The February deep persistent weak layer was down 80 cm and well preserved. Higher up at about 2300 metres the height of snow was a little over two metres. The March crust was not intact at this location and did not result in any shears in snow profile tests. The February DPWL was down 100 cm and was a well defined layer of softer facetted snow below the hard (pencil) snow of the well settled mid-pack. Hard sudden collapse shears were recorded at the interface of the February DPWL. New snow was being transported by the strong gusty winds at the ridgetops. The foot penetration was 25-30 cm, which suggests that there continues to be snow available for transport at higher elevations. Cornices are very large and new growth is expected to be weak and easy to trigger.
Problems
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.
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.