Avalanche Forecast

Issued: Mar 6th, 2018 4:10PM

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

pgoddard, Avalanche Canada

Purcells.

Avalanche danger will spike higher than forecast on slopes that are being cooked by the sun.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

WEDNESDAY: Mix of sun and cloud with flurries. Treeline temperature near -5. Light south-westerly winds.THURSDAY: Cloudy with flurries. 5 cm snow overnight. Treeline temperature near -5. Light south-westerly winds.FRIDAY: Mix of sun and cloud. Treeline temperature near -3. Light south-westerly winds.

Avalanche Summary

A natural cycle of wind slabs and storm slabs to size 2.5 was reported on Sunday/Monday. Explosives testing on Monday produced more storm slabs and wind slabs to size 2.5 on a variety of aspects.

Snowpack Summary

Recent storm snow continues to settle and dry out. Variable recent winds have left behind wind slabs on many slopes at treeline and above. These are expected to heal within a day or two. Direct sun is likely to weaken surface snow layers and give cornices a bit of an extra nudge too.A couple of layers buried in mid-late February (down around 50-100 cm) are variably reactive, but both have the potential to create surprisingly large avalanches if triggered. Initially, this interface was most reactive on solar aspects, where it presents as a buried sun crust. However, it has been triggered on shady aspects too, where surface hoar and/or facets exist.Deeper persistent weak layers from January and December are generally considered dormant, but could wake up with significant warming, a surface avalanche stepping down, a cornice fall, or a human trigger in a shallow or variable-depth snowpack area. These layers consist of sun crust, surface hoar and/or facets. Facets linger at the base of the snowpack.

Problems

Persistent Slabs

Persistent slabs are most likely to be triggered with a large load like cornice fall; or by a person in a thin or variable-depth snowpack spot. Solar warming could make a slab easier to trigger too.

Watch convoluted terrain with variable snowpack depth and multiple trigger points.Pay attention to overhead hazards like cornices which could potentially trigger the persistent slab.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 3

Wind Slabs

Recent variable winds have left behind slabs in the lee of ridges and ribs. Cornices are fragile and may fall with solar warming.

Extra caution needed around cornices with current conditions.Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Mar 7th, 2018 2:00PM