Thursday's snowfall will continue to add to the existing storm slabs which have been reactive recently and may have a poor bond to the underlying surface. Where the older storm snow has already stabilized, watch for new wind slab formation in exposed terrain.
The older storm snow from the weekend may still be reactive and it is recommended to assess the bond between this snow and the underlying surface which may still be weak in isolated terrain. The new storm snow will add to these older slabs or may form reactive new slabs, especially in wind loaded terrain features.
A relatively weak storm system is expected to impact the region Thursday. A break is then expected overnight before the next system arrives Friday afternoon.
Wednesday night: Cloudy with light flurries, moderate to strong SW wind, freezing level around 1000 m.
Thursday: Snowfall 5-15 cm, moderate SW wind, freezing level reaching around 1400 m.
Friday: Snowfall 3-5 cm, moderate SW wind, freezing level reaching around 1400 m.
Friday night and Saturday: Snowfall 15-20 cm, moderate SW wind, freezing level reaching around 1300 m.
An early report from Wednesday includes several natural storm slabs up to size 1.5 in the Coquihalla area which occurred in the past 24 hours. A small natural glide slab was also reported.
On Tuesday, a natural size 2 storm slab was reported in the Coquihalla area. In the north of the region, several human-triggered storm/wind slabs were reported up to size 2. These were on a variety of aspects between 1850 and 2400 m elevation. Slab thickness varied from 20-60 cm and a few were reported to be sliding on the underlying crust which was buried around March 12.
On Monday, natural and skier controlled size 1 storm slabs were observed in wind-loaded convexities around treeline in the north of the region.
Prior to Thursday's snowfall, 20-40 cm of older storm snow which started accumulating on the weekend typically overlies a melt-freeze crust on sun-exposed aspects and wind affected or well-settled old snow on shaded aspects. There have also been some reports of faceting at this interface but no evidence that the facets are large or weak. Recent and ongoing wind has redistributed this older storm snow into reactive wind slabs in exposed terrain. Ongoing wind slab formation is expected on Thursday with some new snow and moderate southwest wind.
In the north of the region, a crust/facet interface from February sits 30-60 cm deep and had been most problematic on north to northeast aspects around 1900-2100 m. This layer produced a number of avalanche in early March but is now considered dormant and no longer seems to be creating a problem in the region.
