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Archived

Avalanche Forecast

Jan 6th, 2016–Jan 7th, 2016
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Mt Hood.

In specific areas, where the most recent storm snow has bonded poorly to the underlying crust, small human-triggered slab avalanches will be possible. Before committing to a slope, think about the consequences of the terrain if even a small avalanche occurred. 

Detailed Forecast

In general, the most recent storm snow overlying recently buried crust shallow and not thought to be especially sensitive to skier triggering. In specific areas, where the storm snow is more cohesive and poorly bonded to the underlying crust, small human-triggered slab avalanches will be possible. Before committing to a slope, think about the consequences of the terrain if even a small avalanche occurred. Note density changes in the upper snowpack throughout the day and as you change aspect and elevation.  

 

Snowpack Discussion

Fair weather was seen for almost a week around the New Year. This weather caused lots of consolidation and stabilizing of the heavy snow from December.

By New Years Eve through the weekend moderate to strong east-northeast winds had significantly scoured or transported available surface snow onto lee west aspects, mainly in the near and above treeline elevation bands.

NWAC pro observer Laura Green was in the Newton Creek drainage Friday and found good skiing in non-wind affected terrain. Even on wind loaded slopes near treeline, the denser wind slab was bonding to underlying snow and no natural or skier triggered avalanches were noted. Significant wind loading continued to occur on the upper mountain Friday and to lesser extent Saturday.

Surface snow sculpted by wind and active wind transport. Photo: Laura Green

On Monday the Mt Hood Meadows pro patrol reported warming and a widespread 1 cm freezing rain crust up to 7000 feet.

Laura was out again near the Mt Hood Meadows ski area on Tuesday and reported 5 inch sensitive small storm slab on steep slopes of varied aspects in all 3 elevations bands. These storm slabs were releasing on the rain crust from Monday. Wednesday's morning control results from Meadows pro-patrol showed predominately shallow storm slabs less sensitive and not running as far as earlier in the week. 

Avalanche Problems

Storm Slabs

Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. 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.

 

You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.

 

Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1 - 1