Confidence
Fair - Forecast snowfall amounts are uncertain
Weather Forecast
A fast moving frontal wave will move onto the coast late today. It should move quickly across the province and be out of the area by Thursday morning. Another Pacific disturbance may bring light precipitation, then weather begins to dry out and cool off.Wednesday evening: Freezing level around 300m, light locally moderate snowfall, some parts of the forecast area may receive 10-15cm of snow, ridge top winds from the SW 30 at times gusting to 80km/h Thursday: Freezing around 600m. Snowfall amounts, 5-10cm, ridge top winds winds gusting from 40 to 80Km/hFriday: Freezing level around 100m. 5 to 10cm of precipitation in the forecast, ridge top winds winds from 15 to 40 Km/h
Avalanche Summary
The Coquihalla has had a large natural avalanche cycle in the past 24 hrs. with avalanches up to size 3.5, running full path. Some of these were in places not normally seen to run except on a 10 to 15 year cycle. Popular ski routes have had natural activity as well. A cornice failure earlier in the week triggered a size 2.5 slab avalanche on the slope below and explosives control has produced numerous very large avalanches.
Snowpack Summary
In the last week, the northern parts of the region have received over 1m of new snowfall and the Southern areas have seen over 1.5m. The Coquihalla has received over 45 cm of new snow in the past 24hrs with high winds, adding to the existing storm slab now 80 to 180cm deep in some parts of the region. In the southern portion of the region the slab sits on a crust/facet combination along with old wind slabs on lee slopes. In the northern part of the region one can add surface hoar to the crust/facet/slab combination. The storm slab seem to be unusually reactive at tree line and below tree line elevations. Whumpfing and widespread natural avalanche activity are a sign of a poor bond between the new snow and these old surfaces. Strong to extreme winds are redistributing the new snow into deeper, reactive wind slabs on the lee side of ridge tops.The mid and lower snowpack are generally strong and well-settled. Although basal facets and depth hoar are likely to exist in the north of the region, giving us a low probability, but high consequence of a large destructive avalanche.
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.