Avalanche Forecast

Issued: Mar 25th, 2016 9:16AM

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

bcorrigan, Avalanche Canada

Northwest Inland.

The hazard may go higher than forecast if temperatures rise unexpectedly. Pay close attention to the danger from cornices and wind slabs.

Summary

Confidence

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

Weather Forecast

The Northwest Inland will see light precipitation through the weekend. TODAY: Freezing level around 1200 m, trace of snow, light to moderate southwest winds. SATURDAY: Freezing level will drop overnight to around 700m, then rise to 1500 m during the day. 1 to 5 cm of snow in the forecast, light to moderate south/southwest winds. SUNDAY: Freezing level dropping to 700 m overnight, then rising to 1300 m during the day. 1 to 5 cm of snow, light winds from the west. MONDAY: Freezing level dropping to 600 m overnight, then beginning to rise to 1500 m by midnight. No precipitation in the forecast.

Avalanche Summary

Loose wet avalanches on solar aspects below treeline are in the news from yesterday. It is spring, after all ! Recently a cornice failure triggered a size 3 slab avalanche in the southwest corner of the region. This avalanche occurred on an east aspect in high alpine terrain and stepped down to persistent weak layers from January and December. A great example of the ability of a large load to trigger weaknesses that are buried deep in the snowpack..

Snowpack Summary

Recently, up to 20 cm of new snow has fallen in some parts of the region accompanied by moderate to strong southerly winds. At treeline and in the alpine small wind slabs are expected to have formed over a variety of surfaces that include a hard crust on solar aspects above 1300 m, moist or refrozen snow on all aspects below 1300 m, and settled wind slabs in exposed high elevation terrain. Of note is a surface hoar from early March that can be found down 50 to 70 cm but only seems to be a problem for the northern half of the region. Professional operators are still tracking two deep weak layers from early-January and early-February that are now down about 1 meter or more. These layers are generally dormant but might wake up with increased warming or a heavy trigger (like a cornice fall). Basal facets exist in most areas and have been shown to be reactive in the north of the region.

Problems

Wind Slabs

Small amounts of new snow with moderate winds will build wind slabs on lee slopes at treeline and in the alpine.

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.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Cornices

Cornices are large and ripe. Treat them with great respect.

Extra caution needed around cornices with current conditions.>Pay attention to overhead hazards like cornices.>Cornices become weak with daytime heating. >

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 5

Deep Persistent Slabs

Rapid warming and/or a large trigger could wake up deeply buried instabilities.

Be aware of the potential for full depth avalanches due to deeply buried weak layers. >Be aware of thin areas that may propagate to deeper instabilities. >Avoid exposure to sun exposed slopes.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 26th, 2016 2:00PM