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Avalanche Forecast

Archived

Jan 25th, 2018–Jan 26th, 2018

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

Regions

Olympics.

Dangerous avalanche conditions will persist on Friday due to additional light snowfall, an uptick in wind transported snow, and cold temperatures preserving recent storm instabilities. Avoid steep open slopes connected to large avalanche paths until we exit this storm cycle. Give safe margins near and below growing cornices. Loose dry avalanches will run fast in steep terrain with plenty of loose snow available, avoid steep lines with terrain traps. Tree-well and snow immersion hazards are very dangerous, so keep communication with your partner at all times. 

Detailed Forecast

Dangerous avalanche conditions will persist on Friday due to additional light snowfall, an uptick in wind transported snow near and below ridges, and cold temperatures preserving recent storm instabilities. Due to lower density surface snow available for transport and light to moderate W-SW winds forecast, wind slabs may develop below treeline or further downslope than you might expect Friday.  Avoid travel on slopes if you encounter wind stiffened surface snow, especially on steeper exposed terrain and steep roll-overs.  

The potential for large and destructive avalanches remains in bigger terrain. Avoid travel on or below slopes connected to large avalanche paths until we exit this storm cycle. Give safe margins near and below growing cornices. There's plenty of good snow out there, so maintain a conservative approach to terrain selection. 

Loose dry avalanches will run fast in steep terrain with plenty of loose snow available, avoid steep lines with terrain traps.

Significantly transformed snow conditions have taken place during this extended storm cycle. Tree-well and snow immersion hazards are very dangerous, so keep communication with your partner at all times.

Snowpack Discussion

The NWAC weather station at Hurricane Ridge has received 8 inches of water equivalent over the past 8 days. It appears to have fallen as snow with the total depth at Hurricane Ridge increasing 50 inches since 1/17. 

An estimated 4 feet of snow rests above the most recent crust on sheltered slopes. Moderate to occasionally strong S-SW winds have continued to transport new and recent snowfall in the Hurricane Ridge area over the last several days. Several avalanche cycles may have occurred since Sunday. New storm snow instabilities have had little time to settle due to the consistent loading in the Hurricane Ridge area during this extended storm cycle. 

A high degree of uncertainty exists in this area due to the lack of observations over the last week, however weather station data would support significant storm and wind slabs exist in the Hurricane Ridge area.

Observations

No recent observations

Problems

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.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.