Avalanche Forecast

Issued: Feb 21st, 2015 8:06AM

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.

jlammers, Avalanche Canada

Purcells.

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

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Mainly sunny skies will persist throughout the forecast period as the dry ridge continues to occupy our province. Daytime freezing levels should hover around 1500m for each day, although an inversion is possible on Tuesday. Winds will remain generally moderate from the northwest.

Avalanche Summary

Avalanche activity has gradually tapered off throughout the week. On Thursday explosive control work on steep North and East facing slopes only resulted in loose snow sluffs. Earlier in the week there were reports of natural and explosive triggered cornice falls and slabs, typically size 2-3 and all from alpine terrain.

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, remains problematic 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

Gusty northwest winds are expected to redistribute recent accumulations into fresh wind slabs in higher elevation terrain. Due to the anomalous wind pattern, wind slabs may be found in unsuspecting locations.

Use ridges or ribs to avoid pockets of wind loaded snow.>Give cornices a wide berth when travelling on or below ridges.>Avoid travelling in areas that have been reverse loaded by winds.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

Persistent weak layers have been less reactive as of late. I'd be increasingly cautious in steep, unsupported terrain and watch my overhead hazard, especially with daytime warming.

Avoid common trigger points like convexities or areas with a thin or variable snowpack.>Do not travel on slopes that are exposed to cornices overhead.>

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Feb 22nd, 2015 2:00PM