Avalanche Forecast

Fair - Timing or intensity of solar radiation is uncertain on Friday

Overnight and Friday: The temperature inversion should end overnight with freezing levels dropping down to valley bottoms. Cloudy overnight with flurries or light snow ending in the morning. Winds becoming Northwest during the day as skies clear and temperatures drop.Saturday: Cloudy with light snow and Southwest winds as a weak Low pressure system collides with the arctic air along the coast. Expect alpine temperatures to be around -15 with moderate Southwest winds.Sunday: Cloudy and cold with light snow and moderate Southwest winds.

A natural avalanche cycle on South aspects caused by strong solar radiation and warm alpine temperatures has resulted in loose wet avalanches up to size 2.0 and has triggered some slab avalanche up to size 2.5 on the February weak layer. I suspect that this activity will end as the arctic front moves cold air into the region over the next few days. Deep releases on the February layer are most likely to continue from North aspects in the alpine where shaded slopes have not settled and bonded and the weak layer is well preserved.

Strong solar radiation and warm air trapped in the alpine have developed a melt-freeze crust on Southerly aspects and caused a great deal of settlement in the old storm slab above the early February weak layer. The February weak layer of crusts and facets has been reported to be rounding and bonding in areas where the old storm slab is 200 cm or deeper ( there is between 2-3 metres of snow above the weak layer in the Coquihalla area). Shallow snow pack areas where the old storm slab is closer to a metre or less continue to give sudden planar shears in snow profile tests ( there is about 60-80 cm above the weak layer in the Duffey Lake area). North aspects in the alpine may have had enough warming to settle the storm snow into a cohesive slab, but not enough to improve the weak layer bond. Big un-supported alpine North aspects are the most likely place to find a well preserved deeply buried February weak layer that may continue to allow for long propagations resulting in very large avalanches.