Avalanche Forecast

Issued: Apr 5th, 2014 9:23AM

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

bcorrigan, Avalanche Canada

South Columbia.

Snowfall amounts and solar input are driving the hazard ratings at this time. More snow or more sun than anticipated may push the hazard higher than forecast. For more insight check out the latest Forecasters Blog.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Synopsis: A series of slow moving frontal systems will move through the BC interior.Tonight: Cloudy with flurries, possible 10 to 15cm of precipitation, freezing level will rise to 1200m and stay there overnight. Winds light, gusting moderate to strong from the south west.Sunday: Cloudy with flurries, no precipitation in the forecast, freezing level may rise close to 2000m, winds light, gusting to moderate from the south west.Monday: Cloudy with flurries, 5 to 10cm of precipitation in the forecast, freezing levels rise to 2500m and winds should be light to moderate from the south west.Tuesday: Cloudy with flurries, light to locally moderate precipitation, 10 to 15cm in the forecast, freezing levels around 2500m, winds from the south light to moderate.

Avalanche Summary

Reports of large avalanches have dropped off, but sluffing of new snow in steep terrain is being reported on all aspects.A low probability, high consequence avalanche problem persists in the Columbia regions. Smaller avalanches have been reported stepping down to old, deeply buried weak layers and producing very large avalanches. Solar input is a big factor as spring progresses. Watch out for large mature cornices!

Snowpack Summary

Recent warm temperatures have resulted in good settlement and bonding of the storm snow from earlier in the week, but wind slabs may still be touchy on north and east aspects.Three persistent weaknesses contribute to a highly variable snow pack with the possibility of triggering deeper instabilities. The mid-March sun crust/surface hoar layer down 50-80cm still has potential for human-triggering in isolated areas. The early-March crust/facet/surface hoar layer down around 80-120cm has become less susceptible to triggering by light loads, but still has the ability to produce large avalanches, we continue to hear reports of avalanches stepping down to this layer. The mid-February crust/facet/surface hoar layer is typically down at least 1.5m and one operator has reported it at 210cm! Direct triggering of this layer has become unlikely, however, al large load like cornice failure or a smaller avalanche gaining mass might still trigger this layer and produce a very large avalanche.

Problems

Wind Slabs

Surface slabs may be reactive to human triggers in wind loaded terrain. A small avalanche could easily injure a rider, or trigger something larger. Solar input is important, especially in the afternoon. Large mature cornices can fail at any time.

Pay attention to overhead hazards like cornices.>Be cautious as you transition into wind affected terrain.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

Weak layers buried earlier remain reactive to rider triggering on convex slopes, south aspects, and in steep alpine terrain. A small avalanche might gain enough mass to trigger a persistent weakness and produce a highly destructive avalanche.

Minimize exposure to sun exposed slopes when the solar radiation is strong.>Use conservative route selection, stick to moderate angled terrain with low consequence.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Deep Persistent Slabs

Highly destructive avalanches are possible. The variable nature of this problem makes it difficult to predict exactly when and where a big avalanche might happen. A cornice failure, solar radiation and warm temperatures could 'wake-up' weak layers.

Be aware of thin areas that may propogate to deeper instabilites.>Local knowledge of slopes that have yet to avalanche is valuable for knowing which slopes to avoid.>Avoid large convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Valid until: Apr 6th, 2014 2:00PM