Northwest Coastal

Human triggering of large persistent slab avalanches remain possible; especially in rocky, alpine terrain with a shallow or highly variable snowpack depth.

Moderate - Due to the number of field observations

SATURDAY NIGHT: Partly cloudy / Light, southeasterly winds / Alpine low 1 C / Freezing level 1400 m.SUNDAY: Mix of sun and cloud / Light, easterly winds / Alpine high 2 C / Freezing level 1500 m.MONDAY: Mostly sunny / Light, northeasterly winds / Alpine high 2 C / Freezing level 1500 m.TUESDAY: Increasing cloudiness / Light, southwesterly winds / Alpine high 0 C / Freezing level 1200 m.

Natural avalanche activity has tapered off with the cloudy skies and cooling temperatures. Concern remains for human triggering persistent slab avalanches on a layer of facets that are down 50-100 cm. Explosive control work on Thursday produced several large avalanches, up to size 3, on this layer and there continue to be reports of skiers experiencing whumphing (collapsing) of this weak layer in shallow or variable snowpack areas in the alpine.

At upper elevations, 50-100 cm of well settled snow overlies weak facets (sugary snow) that were buried around March. 10th. which is currently the primary layer of concern for human triggering persistent slab avalanches.Not much further below the March 10th interface is a second weak layer of facets buried on February 19th. Recent loose wet and slab avalanches have been observed gouging into this faceted snow and entraining additional mass.The prolonged warm spell has transitioned sun exposed slopes in the alpine and all aspects at treeline and below towards becoming isothermal (0 C throughout the snowpack). In these areas that have entered spring conditions, the avalanche hazard will fluctuate greatly depending on the strength of the overnight freeze and how quickly the snowpack is warmed up each day. Check out this guide to managing avalanche hazard during spring conditions HERE.