Avalanche Forecast

Issued: Jan 12th, 2019 4:09PM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Loose Wet and Wind Slabs.

dsaly, Avalanche Canada

South Coast Inland.

A major input of heat into the snowpack can wake up buried weak layers. A lot of uncertainty exists as to what will happen when temperatures climb. Uncertainty is best managed with conservative terrain.

Summary

Confidence

Low - Freezing levels are uncertain

Weather Forecast

SATURDAY NIGHT: Cloudy with clear periods. Light south wind with occasional moderate gusts. Alpine temps near 0 C, temperature inversion with above freezing layer between 1500-2200 m.SUNDAY: Cloudy with sunny periods. Light south-southeast wind with moderate gusts. Alpine temps reaching +4 C, temperature inversion with above freezing layer between 1500-3000 m.MONDAY: Mix of sun and cloud. Light variable wind. Alpine temps reaching +6 C, temperature inversion with above freezing layer between 1500-3000 m.TUESDAY: Sunny. Light variable wind. Alpine temps reaching +4 C, freezing level 1800 m.More details can be found in the Mountain Weather Forecast.

Avalanche Summary

On Friday morning in the Sea to Sky region, explosives triggered large (size 2) cornice failures. As the snowpack warmed through the day, 30-50 cm surface snow gained reactivity as small slabs on convex and unsupported features. Similar snowpack properties can be expected as the snowpack warms in the South Coast Inland.On Thursday, a recent natural wind slab avalanches to size 1.5 were observed on wind-loaded and cross-loaded terrain.

Snowpack Summary

Warm temperatures have moistened surface snow and promoted settlement. On Saturday morning, a melt-freeze crust was noted on all aspects up to 1900 m and south to southwest aspects in the alpine. Cold, dry snow may still be found on north aspects in the alpine along with wind slabs. Cornices are large and suspect with warming. Warm temperatures are expected to penetrate to high alpine areas, Saturday night poor overnight recoveries are expected up to 2000 m.Around the Coquihalla, the top 30-40 cm recent snow sits on a thick 10-15 cm crust up to 1550 m. This crust is not found in the north of the region.Professionals continue to monitor two suspicious layers in the mid-pack consisting of surface hoar (feathery crystals) in sheltered areas and a crust on steep south-facing slopes. The surface hoar is reported to be most prominent on north and east aspects at treeline, and has been well reported in the southern part of the region in areas like the Coquihalla Summit and Manning Park. In the lower snowpack, a crust/facet (sugar snow) layer may still be reactive to heavy loads such as a cornice fall in isolated areas.

Problems

Loose Wet

A major input of heat into the snowpack can stress deeper instabilities and activate buried weak layers. Use caution as the snowpack responds to the initial punch of rapid warming and spiking freezing levels.

Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. Watch for terrain traps where small amounts of snow will acumulate into deep deposits.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 2.5

Wind Slabs

Southerly winds have redistributed snow at higher elevations, including cross-loaded slopes on all aspects. Slabs can become more touchy with warming conditions. Cornices are large and looming, use caution as they weaken with warming.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Cornices become weak with heating, minimize exposure to cornices overhead and stay back on ridges.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: North, North East, East, South East, West, North West.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 13th, 2019 2:00PM