Avalanche Forecast

Issued: Mar 31st, 2014 9:12AM

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

Sea To Sky.

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: 500-1000m pm: 1600m, ridgetop wind: light SW-NWWednesday: Mostly sunny, freezing levels am: 500-1000m pm: 1700m, ridgetop wind: light SW-NWThursday: A mix of sun and cloud, light scattered flurries possible, freezing levels am: 1000m pm: 1500m, ridgetop wind: light S-SW

Avalanche Summary

Reports from Sunday include several human and explosive triggered storm slab avalanches up to size 2. These were typically soft slabs and released down 20-40cm. No natural slabs were reported but natural sluffing was reported from steep features.

Snowpack Summary

The weekend storm typically produced 30-50 cm of new snow but up to 80cm was reported. Below 2100m, on all aspects, this snow rests on thin melt freeze crust that was very reactive on Saturday. (The exception is north facing terrain above 1500m where the crust is not present.) The first part of the storm was accompanied by strong southerly winds that formed isolated wind slabs immediately below ridge crest. The mid March surface hoar/crust interface is down around 80-110cm. The bond at this interface is improving making it less susceptible to human triggering. The early-March crust/facet layer is down about 100-150 cm and the early February layer is now down close to 200 cm. These layers are mainly dormant at this time but still have the potential to produce avalanches in isolated areas. The lower snowpack is generally strong and well settled.

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.

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

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

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