Avalanche Forecast

Issued: Mar 31st, 2014 9:55AM

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

mbender, Avalanche Canada

South Columbia.

Summary

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

A ridge of high pressure persists until Wednesday. A weak disturbance may cross the region on Wednesday night resulting in increased cloud cover and isolated light showers.Tuesday: Mostly sunny, freezing level am: 400m pm: 1800m, ridgetop wind: light NWWednesday: A mix of sun and cloud, freezing level am: 600m pm: 1800m, ridgetop wind: light SW-WThursday: Mainly cloudy. Winds light southwest. Freezing level 1700m.

Avalanche Summary

A low probability, but high consequence avalanche problem plagues the Columbia regions. These highly destructive and largely unpredictable avalanches are expected to be isolated, but certainly possible anywhere at any time. Avalanches continue to step down to old, deep weak layers. The most recent was a natural size 3 in the Cariboo region on Thursday. The S Columbia had one step down on Tuesday and the N Columbia on Monday. While these layers are typically dormant, they are expected to become reactive again with the new loading or the upcoming strong solar inputs.Most recent reports for the South Columbia include isolated human and explosive triggered avalanches up to size 1.5 in the recent storm snow down around 20cm. Loose sluffing from steep terrain features was also reported.

Snowpack Summary

Recent warm temperatures have resulted in good settlement and improved bonding of the storm snow from earlier in the week, and human-triggering has generally become stubborn. Three persistent weaknesses contribute to a highly variable, fundamentally unstable, complex snowpack with step-down potential. 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 human-triggers, but still has the potential to produce large avalanches, and we continue to see fractures stepping down to this layer. The mid-February crust/facet/surface hoar layer is typically down at least 1.5m and direct triggering has become unlikely. However, large loads like cornices or smaller avalanches stepping down can still trigger this layer and produce very large avalanches.

Problems

Wind Slabs

Stiffer wind slabs can be expected on leeward features on NW through E aspects.

Minimize exposure to sun exposed slopes when the solar radiation is strong.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

Weaknesses buried earlier this month remain reactive to light triggers in isolated areas (convex slopes, southern aspects, and higher elevations). Step down potential to deeper persistent weaknesses can result in highly destructive avalanches.

Use conservative route selection, stick to moderate angled terrain with low consequence.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Deep Persistent Slabs

Isolated highly destructive avalanches are expected to continue. But beware, the variable nature of this problem makes it difficult to predict exactly when and where avalanches are going to occur. Sun and warm temperatures may 'wake-up' this layer.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Valid until: Apr 1st, 2014 2:00PM