Avalanche Forecast

Issued: Mar 3rd, 2014 8:24AM

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

rbuhler, Avalanche Canada

Kootenay Boundary.

Summary

Confidence

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

Weather Forecast

A series of weak disturbances will result in light intermittent snowfall during forecast period. Freezing levels are expected to rise to as high as 2000m by Wednesday. Tuesday: Scattered flurries 3-5cm, freezing level rising to around 1500m, ridgetop winds 30-50 km/h SWWednesday: Snow or rain 6-10mm, freezing level around 2000m, ridgetop winds 40-60 km/h SW-WThursday: Snow or rain 8-12mm, freezing level around 1800m, ridgetop winds 30-50 km/h SW

Avalanche Summary

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

Snowpack Summary

The primary concern remains a persistent slab (typical thickness 50-90cm) from the last series of storms that is sitting on a stubborn persistent weak layer consisting of facets, surface hoar, melt-freeze crusts, or any combination of these. This weak layer is widespread at all elevations and aspects. Recent test results are suggesting that the layer is still easy to trigger in some areas but may becoming harder to trigger in other areas. We are still receiving isolated reports of large settlements or whumpfing which suggests the layer still has the potential for large propagations. In many areas the layer has the potential to produce large, destructive avalanches. The phase we are now entering is referred to a 'low probability/high consequence' problem. Continue to use conservative terrain choices until you are sure the layer is no longer unstable in your local area. Strong forecast winds from the SW are expected to create touchy new wind slabs on leeward slopes and cross-loaded features. As more snow accumulates we can expect a more widespread storm slab. This slab sits on top of surface hoar up to 10mm, near-surface facets, and/or a sun crust on south facing slopes.

Problems

Persistent Slabs

The thick persistent slab on the early-Feb weak layer is still reactive to human triggers 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.

Remote triggering is a big concern, be aware of the potential for wide propagations and large, destructive avalanches at all elevations.>Use conservative route selection and resist venturing out into complex terrain, even if you observe no obvious signs of unstable snow.>Avoid unsupported slopes.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

3 - 6

Storm Slabs

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

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Mar 4th, 2014 2:00PM