Avalanche Forecast

Issued: Feb 22nd, 2015 7:54AM

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

Avalanche Canada jlammers, Avalanche Canada

Keep an eye on the temperatures on Monday. Solar radiation and rising freezing levels can weaken the snowpack and make destructive avalanches more likely.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Monday

Weather Forecast

The dry ridge will persist throughout the forecast period bringing a mix of sun and cloud until Wednesday. Winds will generally remain light from the northwest, although strong gusts are likely on Tuesday. On Monday we can expect an inversion with above-freezing alpine temperatures. Freezing levels will hover around 1500m on Tuesday, and then drop to about 800m on Wednesday.

Avalanche Summary

Last week there were reports of natural and explosive triggered cornice falls and slabs, typically size 2-3 and all from alpine terrain. Avalanche activity of this nature has gradually tapered off throughout the week. Looking forward, thin wind slabs may still be sensitive to triggering in high elevation terrain. Warming forecast for Monday may spark some loose wet avalanche activity on sun-exposed slopes while increasing the likelihood of deeper persistent slab avalanches.

Snowpack Summary

Generally light amounts of new snow cover the previous variable snow surface of crusts, surface hoar, dry facetted snow, or wind affected snow depending on aspect and elevation. Thin new wind slabs are likely in exposed lee terrain, and cornices remain large and weak. The 'Valentine's Day' crust is thick and supportive below 2100 m. The late-Jan crust/surface hoar layer is 1-2 m deep in the west, and can be found within the upper metre of the snowpack further east. It is variably reactive in snowpack tests and still the main concern in many areas. The mid-January surface hoar, deeper again, is also a concern in some areas. The mid-December and mid-November weak layers of crusts and facets can still be found near the bottom of the snowpack, particularly in shallower eastern parts of the Purcells.

Problems

Wind Slabs

An icon showing Wind Slabs
Gusty northwest winds may have redistributed recent accumulations into fresh wind slabs in higher elevation terrain. Warming on Tuesday may reactive these wind slabs and also promote loose wet avalanches on sun-exposed slopes.
Avoid travelling in areas that have been reverse loaded by winds.>Give cornices a wide berth when travelling on or below ridges.>Use ridges or ribs to avoid pockets of wind loaded snow.>Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
Persistent weak layers have been generally dormant as of late. That said, I'd watch my overhead hazard and be increasingly cautious in steep, unsupported terrain, especially with warming forecast for Monday afternoon.
Do not travel on slopes that are exposed to cornices overhead.>Avoid common trigger points like convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Feb 23rd, 2015 2:00PM

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