Avalanche Forecast

Issued: Mar 27th, 2016 8:43AM

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

bcorrigan, Avalanche Canada

Northwest Coastal.

Conservative route selection is essential now. Wind slabs, and cornices are prime concerns these days. Pay close attention to temperatures and solar input while riding in the back country.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

The Northwest Coastal will see light precipitation in advance of a ridge of high pressure that will bring clear skies and warm temperatures. MONDAY: Freezing level dropping to 600 m overnight, then beginning to rise to 1500 m by midnight. Winds begin to change from west to north west with no significant precipitation in the forecast for Monday. TUESDAY: Freezing level around 2500 m early in the day then begin a slow but steady rise to end the day around 3000 m. No precipitation on Tuesday and light to moderate north west winds. WEDNESDAY: The freezing level continues to rise, topping off the day at 3500m, with winds from the north and no precipitation. The day should be sunny with a bit of valley fog early in the day.

Avalanche Summary

A few storm slab avalanches up to size 1.5 on north and north east aspects above 1400m triggered by explosives and 2 skier controlled size 1 wind-slabs. Pay close attention to warming and solar radiation as the high pressure system moves into the area and spring heats up.

Snowpack Summary

5 to 10 cm of storm snow has fallen at higher elevations recently. At treeline and in the alpine small wind slabs will have formed. These wind slabs overlie a variety of surfaces which include a hard crust on solar aspects above 1300 m, moist or refrozen snow on all aspects below 1300 m. A layer of surface hoar from March 25th has been noted buried under 15 to 20 cm of storm snow and resting on a melt freeze crust. . A more widespread crust/facet layer buried in early February can now be found down over a metre. Both of these layers have the potential for large avalanches especially with a large trigger such as a cornice fall. Be cautious during periods of warming and intense solar radiation. As the winds from the incoming high pressure system change from west to north, the potential for reverse loading will exist, wind slabs may form on south slopes rather than north slopes, stay attuned to what the wind is doing!

Problems

Wind Slabs

Wind slabs overlying surface hoar in some locations, and be aware of the potential for reverse wind loading as the high pressure system moves into the region. Approach potentially wind loaded areas with great caution.

Be cautious as you transition into wind affected terrain. >Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Avoid cross loaded slopes at or above treeline.>The new snow will require several days to settle and stabilize.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Cornices

Cornices are large and mature, and may become weak with forecast warming.

Extra caution needed around cornices with current conditions.>Pay attention to overhead hazards like cornices.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 5

Persistent Slabs

Deeply buried weak layers may be hard to trigger, but a large event, such as a cornice failure might wake it up. Rapid warming make makes weak layers easier to trigger. The snow pack doesn't like rapid change.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar. >Conditions have improved, but be mindful that persistent instabilities are still present.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 28th, 2016 2:00PM