Avalanche Forecast

Issued: Jan 29th, 2013 9:08AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Wind Slabs and Persistent Slabs.

jfloyer, Avalanche Canada

Cariboos.

If more than 15 cm of snow lies on the ground Wednesday morning, consider danger to be HIGH in the Alpine and at Treeline.

Summary

Confidence

Poor - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

Synopsis: Continued northwesterly flow will bring moderate or locally heavy pulses of precipitation to the region interspersed with some dry patches.Tuesday night: 10-15 cm low density new snow.Wednesday: Another 10-15 cm new snow through the day. Treeline temperatures should peak around -4C. Northwesterly winds gusting to 60 km/h.Thursday: Light snowfall, 2-4 cm. Temperatures rising in the afternoon to around -1C at treeline. Moderate northwesterly winds.Friday: Some clear spells and some flurries. Temperatures around -4C at treeline. Moderate northwesterly winds.

Avalanche Summary

No new avalanches reported from this region.

Snowpack Summary

Around 40-50 cm recent new snow has settled into a 20-30 cm soft slab overlying a weak layer comprising of facets at higher elevations, surface hoar on shady slopes, and a sun crust on solar aspects. The recent new snow sitting above this interface has been slowly consolidating from fresh powder into a more cohesive slab. As this process continues, the avalanche character will change from relatively harmless loose sluffs to more dangerous slab avalanches. However, note this upper weak layer has been reported to be patchy and variable in distribution. A mid-pack layer buried in early January surface hoar layer is down 70-90 cm. While this layer is still on the radar of professional observers, with most likely trigger points being on steep rolls below 1600 m, there has only been one small avalanche (size 1 at 1200 m on a north aspect) reported on this layer from the region for approximately 10 days.

Problems

Wind Slabs

Forecast new snow and northwest winds will likely set up fresh wind slab on south and east aspects in exposed lee terrain. Old wind slabs exist on north aspects.

Avoid freshly wind loaded features.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

Two surface hoar layers lie buried under the surface, one approximately 40cm down and the other approximately 80cm down. Both are reported to be patchy and variable in distribution. Most likely triggered on steep convex rolls at treeline or below.

Whumpfing is direct evidence of a buried instability.>Avoid steep convex rolls at and below treeline where buried surface hoar may be preserved.>Dig down to find and test weak layers before committing to a line on steep slopes in open glades.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Jan 30th, 2013 2:00PM