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Avalanche Forecast

Archived

Jan 20th, 2018–Jan 21st, 2018

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

Stormy conditions will create very dangerous avalanche conditions on Sunday. Identify and avoid avalanche terrain including traveling below avalanche paths connected to higher terrain. 

Detailed Forecast

Another round of significant precipitation and wind are expected in the Olympics Sunday. High snowfall rates, significant snow loading, moderate to intense wind transported snow, and a slight warming trend will combine to create very dangerous avalanche conditions. Expect avalanche danger to increase throughout the day.

Sensitive wind and storm slabs developed over the last several days and will continue to grow in size and become more reactive. Extra caution should be taken when traveling Sunday. Pay attention to terrain around you and avoid traveling in the tracks and runouts of avalanche paths. Natural avalanches are expected during the day, especially above treeline.

Snowpack Discussion

A stormy and windy period, beginning Wednesday and extending into the weekend, deposited over 2 feet of snow in the Hurricane Ridge area. Moderate to strong southerly winds redistributed the surface snow forming wind slabs on lee slopes near and above treeline.

New snow is bonding well to the most recent 1/16 crust layer. Currently there are no layers of concern below this most recent crust.

Observations from this region are limited. A high degree of uncertainty exists in this area.

The height of snow across the terrain is quite variable with little snow in many areas below treeline. Numerous obstacles still exist at all elevations.

Observations

NWAC observer Matt Schonwald traveled in the Hurricane Ridge terrain Thursday, Jan 18. Matt found right side up new snow bonding well to the underlying old snow surface. In wind exposed terrain however, winds Thursday were actively transporting new snow and building sensitive slab layers.

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.