Avalanche Forecast

Issued: Mar 4th, 2014 8:46AM

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

rbuhler, Avalanche Canada

Kootenay Boundary.

Summary

Confidence

Poor - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Two frontal systems will cross the region during the forecast period. The first is expected early Wednesday morning and the second is expected Wednesday night or early Thursday. Dry conditions are expected for Friday with some clearing. There is some uncertainty with the forecast freezing levels and freezing levels have the potential to be lower than those listed below.Wednesday: Rain or snow 10-15mm, freezing level around 2000m, ridgetop winds 20-40 km/h SWWed. Night/Thursday: Rain or snow 15-25mm, freezing level around 1400-1800m, ridgetop winds 30-50 km/h SWFriday: A mix of sun and cloud, mainly dry conditions, freezing level around 2000m, ridgetop winds light km/h SW-NW

Avalanche Summary

Explosive control on Monday produced numerous size 2 storm slab avalanches.

Snowpack Summary

20-30cm of new snow sits on top of surface hoar up to 10mm, near-surface facets, and/or a sun crust on south facing slopes. Warmer temperatures and the upcoming snowfall will likely result in the formation of a touchy, widespread storm slab. The immediate concern is deeper, wind-loaded areas where a cohesive slab already exists and immediate leeward features where stiffer wind slabs have formed during recently strong SW-W winds. A major concern remains a persistent slab (typical thickness 50-90cm) that sits below the new storm snow. This slab sits on a tricky weak layer consisting of facets, surface hoar, and/or sun crusts which was widespread at all elevations and aspects. While avalanche activity on this layer has decreased recently, reports suggest that where the layer still exists it has the potential to produce large, destructive avalanches. The phase we are now entering is referred to a 'low probability/high consequence' problem. It is possible that with the weight of the new snow, we may see a resurgence of natural activity on the layer.

Problems

Storm Slabs

New snowfall will form a storm slab which overlies a variety of potentially weak surfaces. Moderate to strong SW winds have formed stiffer wind slabs in leeward and cross-loaded features which will be more sensitive to human triggers.

Avoid avalanche terrain during periods of heavy loading from new snow and wind.>Avoid freshly wind loaded features.>The new snow will require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

The thick persistent slab on the early-Feb weak layer still remains reactive in some areas and has the potential to produce large, destructive avalanches. The new snow may 'wake up' the weak layer and very large natural avalanches are possible.

Avoid unsupported slopes.>Use conservative route selection and resist venturing out into complex terrain, even if you observe no obvious signs of unstable snow.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 5th, 2014 2:00PM