Avalanche Forecast

Archived

Feb 16th, 2018–Feb 17th, 2018

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

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Additional wind and snow will increase the avalanche danger throughout the day Friday. Identify and avoid wind loaded slopes where you will be able to trigger new wind slabs. Blowing snow, plumes, and fresh cornices all indicate wind slabs are present on the slopes below. As storm slabs grow, stay off of convex rolls and unsupported slopes where you are more likely to trigger a slab avalanche.

Detailed Forecast

Wind and storm slabs will become larger and easier to trigger Friday as additional snow and wind impact the Mt Baker area.

You will find wind slabs on lee slopes on exposed terrain features formed by moderate westerly winds. Use visual clues such as blowing snow, plumes, surface cracking, and fresh cornices to indicate wind slabs exist on slopes below. Stay off of steep wind loaded slopes where you will be able to trigger a potentially large wind slab avalanche.

Storm slabs will develop throughout the day as additional snow falls and temperatures warm. This new snow is falling on weak loose surface snow from earlier in the week. Avalanches may break down to older crust layers. Avoid convex and unsupported slopes where you are more likely to trigger these slab avalanches. Be ready to dial down your terrain if more snow falls than expected in the Baker area.

Snowpack Discussion

Six to ten inches soft surface snow accumulated Tuesday and Wednesday in the Baker backcountry. This new snow sits on a weak crust/facet combination. This poor snow structure was found on all but steep south facing slopes. As of Thursday avalanches have been reported on this layer.

Below this upper snowpack, warm wet weather from early February has created a strong well consolidated snow structure. There are no significant layers of concern in the mid and lower snowpack.

Observations

NWAC professional observer Lee Lazzara was in the Mt Baker backcountry Thursday. He found 10 inches of soft snow over a facet/crust combo in most locations. Observations of the crust indicate that it is not currently reactive due to insufficient snow loading. Lee reported natural loose dry avalanches from Wednesday but did not see any new avalanches Thursday.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.