Avalanche Forecast

Issued: Mar 31st, 2014 9:15AM

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

rbuhler, Avalanche Canada

South Coast.

Use increased caution during afternoon warming, especially on sun exposed slopes.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

A ridge of high pressure will keep the south coast clear and dry for Tuesday and Wednesday. The next frontal system arrives on the north coast Wednesday and should reach the south coast on Thursday. Current forecasts have the precipitation starting late Thursday. There is some model uncertainty regarding overnight freezing levels.Tuesday: Sunny, freezing levels am: 400-800m pm: 1700m, ridgetop wind: light variableWednesday: Mostly sunny, freezing levels am: 700-1000m pm: 1800m, ridgetop wind: light SW-NWThursday: A mix of sun and cloud, light scattered flurries possible, freezing levels am: 1000m pm: 1700m, ridgetop wind: light S-SW

Avalanche Summary

Reports from Sunday include isolated natural and human triggered slab avalanche to size 2.5 and widespread sluffing from steep terrain. The natural size 2.5 released on a north aspect slope in the storm snow up to 50cm deep. Natural size 1 wet slabs were reported on southerly aspects below 1700m. A skier triggered a small storm slab on a northerly convex feature in the alpine.

Snowpack Summary

The weekend storm produced 30 to 50cm in the north and around 30 cm in the south. Moderate southerly winds have formed wind slabs in immediate leeward feature in wind-exposed terrain. Below 2000m the new snow rests on a thin melt freeze crust on all aspects, with the exception being north facing terrain features above 1500m. Mild temperatures and solar radiation on Monday are likely causing settlement of the storm snow and melting of the snow surface on most slopes expect maybe steep north aspects in the alpine. The persistent weak layers from early March and early February continue to be a concern. The March weak layer of wind-scoured crusts, melt-freeze crusts, and/or surface hoar is reported to be down 60 - 100cm. The February crust/facet/surface hoar layer is now deeply buried down 150 - 250cm and may still be triggered by heavy loads like cornice falls or storm slab avalanches in motion. Long fracture propagations resulting in very large avalanches are possible with this layer. Avalanches releasing on these layers may step down to the ground during periods of strong solar radiation or warm spring rain.

Problems

Storm Slabs

Recent storm snow may still be reactive to human triggers. Stiffer wind slabs in lee features may be more sensitive to triggering. Sun will increase the reactivity of the storm slab in the afternoon and loose activity is expected from steep terrain.

Use ridges or ribs to avoid pockets of wind loaded snow.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>The new snow will likely require another day to settle and stabilize.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

Two deep weak layers exist in the snowpack. These weak layers could be activated by cornice fall, a smaller avalanche stepping down, or a rider finding the sweet spot, likely near a rock outcropping, or anywhere the snowpack goes from thick to thin.

Be aware of thin areas that may propogate to deeper instabilites.>Extra caution needed around cornices with current conditions.>Be aware of the potential for large, deep avalanches due to the presence of buried facets and surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Apr 1st, 2014 2:00PM