New snow builds fresh, reactive storm slabs over weak surfaces and adds load to deeper buried weak layers. If you see more than 25 cm, treat avalanche danger as HIGH.
Buried persistent weak layers have produced large natural and human triggered avalanches recently. Additional snow load may increase sensitivity to triggering.
New snow is expected to bond poorly to old surfaces including crusts and widespread surface hoar. Storm slabs are most likely to fail in wind loaded areas where sufficient snow has been deposited to overload the weak interface.
Persistent slabs were reactive on the February weak layer early this week, with naturals up to size 3. Activity tapered dramatically by Tuesday when several natural cornice failures did not trigger slabs on slopes below, and on Wednesday explosive control work near Shames produced minimal results.
Looking forward, new snow means an increase in likelihood of both surface avalanches as well as renewed possibility of large persistent slab avalanche activity.
New snow accumulates over a widespread layer of large surface hoar crystals, which sit over a crust on solar aspects and low elevations.
A layer of facets, surface hoar and/or a crust from mid February are buried 50–100 cm deep. This layer produced large natural and human-triggered avalanches earlier this week.
The remainder of the snowpack is well consolidated with no concerns at this time.
Forecast snowfall amounts are highest on the immediate coast, tapering sharply as you travel inland.
Thursday night
Cloudy with 5 to 10 cm of snow. 50 to 70 km/h southwest ridgetop wind. Treeline temperatures -3 °C. Freezing level 800 m.
Friday
Cloudy with 5 to 15 cm of snow above 1000 m, rain below. 80 to 100 km/h southwest ridgetop wind. Treeline temperatures -1 °C. Freezing level 1300 m.
Saturday
Mostly cloudy with 5 to 10 cm of snow above 800 m, light rain below. 30 to 50 km/h southwest ridgetop wind. Treeline temperatures -1 °C. Freezing level 1000 m.
Sunday
A mix of sun and cloud. 10 to 20 km/h northwest ridgetop wind. Treeline temperatures -4 °C. Freezing level 1000 m.
More details can be found in the Mountain Weather Forecast.
