Avalanche Forecast

Issued: Jan 15th, 2014 9:21AM

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

jlammers, Avalanche Canada

South Columbia.

Warm temperatures and sunny skies forecast for the next few days will have a significant weakening effect on the snowpack. If solar radiation is particularly strong, the avalanche danger could rise to HIGH.

Summary

Confidence

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

Weather Forecast

Generally clear skies are expected for the forecast period as a ridge of high pressure becomes established over much of the province. Winds are forecast to be light to moderate from the northwest becoming southwesterly on Saturday. Daytime alpine temperatures are expected to hover between 0.0 and +5.0.

Avalanche Summary

Several natural storm slab avalanches to size 3 were reported in the region on Tuesday, most occurring in alpine terrain on various aspects. I would expect avalanche occurrences to include loose wet activity with the potential for deeper slab activity with forecast warming on Thursday

Snowpack Summary

Parts of the forecast area have received up to 90cm of storm snow which has been blown into dense windslabs in exposed areas. The new snow overlies a variety of old surfaces, the most reactive of which appears to be the Jan 8th surface hoar. There are reports of "sudden" test results on this layer, now buried anywhere from 55cm to 90cm below the surface. There are 2 other layers of note which professionals are keeping a close eye on: The late-November persistent weak layer consists of a sun crust on steep south facing slopes and surface hoar in sheltered areas and may sit well over 200cm below the surface. At the base of the snowpack you may also find the October persistent weak layer which consists of facets sitting on a crust. This layer is predominantly found on northerly aspects at tree line and in the alpine. The depth of both these layers makes directly triggering an avalanche on them unlikely (maybe a heavy load on a thin spot in steep terrain), but the consequences would be large and destructive.

Problems

Persistent Slabs

Forecast warming will increase the likelihood of triggering a number of persistent weaknesses which exist in the snowpack. Triggering a persistent slab avalanches would have nasty consequences.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Avoid convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Loose Wet

Forecast warming will likely produce loose wet avalanches in steep, sun-exposed terrain. A loose wet avalanche in motion may also "step down" triggering deep and destructive slab avalanches.

Avoid exposure to solar aspects overhead, large avalanches may reach the end of run out zones.>Sluffs may trigger deeper instabilities.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: North, North East, East.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Storm Slabs

Although storm slabs may be gaining strength, they may be particularly reactive in steep, wind-affected terrain, or in areas where they overlie buried surface hoar.

Be cautious as you transition into wind affected terrain.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Jan 16th, 2014 2:00PM