Avalanche Forecast

Issued: Mar 12th, 2014 9:50AM

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

bcorrigan, Avalanche Canada

Kootenay Boundary.

The hazard may go higher than forecast below treeline with rising temperatures and solar input. Large mature cornices are also a serious concern these days. For more insight into these tricky conditions see the latest:Forecaster Blog.

Summary

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

Synopsis: The ridge of high pressure holds for the next few days with clear skies and warm spring-like conditions. There is a possibility of moisture by the weekend.Tonight: Cloudy with clear periods, freezing level around 600m, ridge top winds light, occasionally gusting to strong from the west.Thursday: Sunny with cloudy periods, freezing level around 1400m. Light ridge top winds occasionally gusting to moderate.Friday: Cloudy with sunny periods, light to locally moderate precipitation amounts, freezing level around 1400 metres, winds from the southwest , light to moderate, occasionally gusting to strong.Saturday: Cloudy with scattered flurries. freezing level around 1400 metres, ridge top winds light, occasionally gusting to strong.

Avalanche Summary

We've received reports of large ( size 2 and 3 ) natural avalanches in the region. Cornice failures and resulting large avalanches are being reported in the Kootenay-Boundary region and in the neighboring areas as well. Careful attention to daytime warming and aspect will be necessary to ride safely in the back country.

Snowpack Summary

Warm temperatures have promoted rapid settlement of the recent storm snow into a dense slab that sits above a variety of old surfaces. Overnight freezing will help seal up the surface from the weak layers buried below, at least until warm daytime temperatures break down the surface crust, then all bets are off ! Rain up to 1900m has saturated the upper snowpack in some parts of the forecast area and will crust-over as the freezing level lowers at night. At elevations above the freezing level strong SW winds have have formed significant winds slabs in lee features adding load to the storm slab overlying a variety of persistent weak layers.3 persistent weak layers are buried in the snowpack, A January 28th layer of surface hoar, facets and crusts, a Feb.10th layer of surface hoar, facets and crusts now almost 200cm down,... and the March 2nd layer of surface hoar, facets and crusts at approximately 120cm from the surface.. Of these layers, the Feb. 10th/Jan. 28th layers still appear to be problematic with field reports indicating easy and sudden planar shears on this layer, especially on north aspects. Some parts of the forecast region recently received 5cm of new snow.

Problems

Storm Slabs

Temperatures will rise over the next few days, Use caution on sun drenched slopes, south west winds have formed wind slabs on lee slopes at tree line and above. Storm snow on solar aspects may be on a sun crust that is touchy and quite reactive.

Choose conservative lines and watch for clues of instability.>Be alert to conditions that change with elevation.>The new snow will require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Likely

Expected Size

2 - 4

Loose Wet

Rain soaked snow as well as aspects exposed to solar radiation may be touchy during this warm period, even in areas not normally regarded as "avalanche terrain".

Avoid steep, open glades in the forest.>Watch for terrain traps where small amounts of snow will acumulate into deep deposits.>The new snow will require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Deep Persistent Slabs

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Avoid unsupported slopes.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 13th, 2014 2:00PM