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Avalanche Forecast

Archived

Jan 11th, 2018–Jan 12th, 2018

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

Regions

Olympics.

Approach avalanche terrain especially near and above treeline with caution on Friday in the Hurricane Ridge area. Time and patience is advised to let recent storm snow instabilities heal. Recent and fresh wind slab, should exist near and above treeline on a variety of aspects.  

Detailed Forecast

Snow levels should eventually settle around 4000-4500 feet Thursday night and Friday across the region. Light showers seen through Friday morning should taper down in the afternoon. 

Approach avalanche terrain especially near and above treeline with caution on Friday in the Hurricane Ridge area. Time and patience is advised to let recent storm snow instabilities heal. Recent and fresh wind slab, should exist near and above treeline on a variety of aspects.  Small loose wet avalanches are possible below treeline and could push you into a terrain trap. 

Despite the recent snow, early season hazards still exist. Many creek beds have still not filled in for the winter.

Snowpack Discussion

12-14 inches (30-35 cm) of storm snow overlies the most recent rain crust in the Hurricane Ridge area in non-wind affected terrain. Below this rain crust, no notable layers of concern have been identified in the snowpack. 

The height of snow across the terrain is quite variable with low snow in many areas below treeline. Even in areas near and above treeline, specific slopes have low snow cover where wind, rain and warm temperatures have stripped much of the season's snowfall. Numerous obstacles still exist at all elevations. 

Observations

NWAC pro-observer Matt Schonwald was at Hurricane Ridge on Thursday 1/11. Matt found despite the significant storm snow still accumulating at day's end, the below treeline elevation band had quite variable snowcover.  Around Hurricane Ridge at 5200', the east side of the ridge had a snowdepth of 2.5 feet and the west side had about 5 feet. Reactive storm layers were identified in snowpit tests, but signs of natural slab activity were not observed. Winds were actively transporting new snow near and especially above treeline, but the loading pattern was variable.  Small loose wet avalanches were observed releasing in steep terrain above the road at about 4500' during gradual warming on 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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.