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Avalanche Forecast

Archived

Jan 26th, 2018–Jan 27th, 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 and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Mt Hood.

Significant new snow on Mt Hood over the past week deserves respect. Keep terrain choices dialed down as this very active weather pattern continues Saturday. Be aware of the terrain around and above you, where very large and destructive avalanches may run long distances to lower elevations. 

Detailed Forecast

Stormy conditions Friday night into Saturday morning will increase the avalanche hazard in the Mt Hood area.

Near and above treeline winds will continue to build on already sensitive wind slabs. As sensitive wind layers become buried deeper, they will become more difficult to trigger but can still result in a large and destructive avalanche. Identify and avoid firm wind deposited snow.  

Relatively warmer temperatures, gusty winds and occasional showers will make triggering storm slabs easier. As snow showers change to rain showers at lower elevations, expect loose dry avalanches to transition to loose wet on steeper slopes. Be aware of the consequences of a loose avalanche above terrain traps. 

With all the new snow, this is a time to stick to safer terrain. Utilize low angle slopes, and be aware of terrain above you. Large avalanches may originate at higher elevations and travel to runouts even below treeline.

Snow conditions changed significantly during this extended storm cycle. Tree-well and snow immersion hazards are very dangerous. Keep communication with your partner at all times.

Snowpack Discussion

A very active weather pattern continues to impact the Mt Hood area. Approximately 30 inches of settled snow now sits on top of the 1/18 crust. Fluctuations in precipitation intensity and temperature seen throughout the storm cycle created several sensitive storm layers within the new snow.  Depth and sensitivity of these layers varies depending on location and elevation.

Moderate winds over the last eight days redistributed snow on exposed features near and above treeline. Shifts in wind direction created wind slabs on a variety of aspects.

With the ongoing storm cycle, direct observations above treeline have been hard to come by. A high level of uncertainty exists above treeline. 

Observations

NWAC pro-observer Laura Greene was in the Newton Creek drainage Friday. She encountered low visibility with lots of new snow and wind transportation. Observations found 2.5 feet of storm snow. 

On Friday, Mt. Hood Meadows patrol reported 2-6" sensitive wind slabs during control work near treeline. Below treeline, snow was generally right-side up and no reactive storm layers were noted. No observations were made above treeline. 

On Wednesday, a professional ski patroller was caught, carried, and partially buried in an avalanche he triggered while on duty in a closed area of the Mt. Hood Meadows ski area (SS-AS-R2-D2-I). The avalanche released in an area known as God's Wall, running approximately 600 ft on the old/new snow interface. The bed surface was the firm 1/18 crust. Resources were dispatched immediately and the victim extricated after some difficulty due to low snow and open creeks. He was transported via ambulance to advanced care and is now discharged to recover from his injuries.

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.