Avalanche Forecast

Issued: Jan 17th, 2014 8:39AM

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

Avalanche Canada jlammers, Avalanche Canada

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 Saturday

Weather Forecast

A ridge of high pressure will continue to dominate the region bringing dry conditions and mainly clear skies for the foreseeable future. Winds should be light to moderate from the west on Saturday, becoming light and northwesterly on Sunday and Monday. An inversion is expected for Saturday bringing valley cloud and alpine temperatures reaching +5.0. More seasonal temperatures are expected for Sunday and Monday.

Avalanche Summary

Steep solar aspects saw numerous loose wet and slab avalanches on Thursday with some occurrences to size 3. On the same day in the south of the region, a snow cat was working on ridge and remotely triggered a size 3 deep slab avalanche from 30m away. The avalanche, which failed on basal facets, occurred on a southeast facing slope at 2160m.I would expect more loose wet activity and cornice fall with real potential for deep slab activity with continued warming.

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 skier triggering unlikely (maybe a heavy load on a thin spot in steep terrain, a cornice fall or rapid warming). The consequences of triggering any of these weaknesses would be severe..

Problems

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Continued warming will increase the likelihood of triggering a number of persistent weaknesses which exist in the snowpack. Triggers may include cornice fall or a surface avalanche in motion. Any persistent slab avalanche would be highly destructive.
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Avoid convexities or areas with a thin or variable snowpack.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Loose Wet

An icon showing 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

Expected Size

1 - 3

Wind Slabs

An icon showing Wind Slabs
Recently formed windslabs have likely gained significant strength; although triggering may be possible in steep, unsupported terrain. Watch for increased triggering with forecast warming.
Be aware of the potential for wide propagations due to the presence of hard windslabs.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 4

Valid until: Jan 18th, 2014 2:00PM