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Archived

Avalanche Forecast

Jan 9th, 2016–Jan 10th, 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.

The main problem on Sunday should be loose wet avalanches. It is a bit hard to say how extensive the loose wet avalanches will be so pay close attention to snow conditions if you venture out on Sunday.

Detailed Forecast

Sunny warmer weather should be seen on Sunday. It may be significantly warmer at higher elevations and west of the crest.

The main problem on Sunday should be loose wet avalanches. It is a bit hard to say how extensive the loose wet avalanches will be so pay close attention to snow conditions if you venture out on Sunday. Possible loose wet avalanches should be mainly confined to steep southeast to southwest aspects during the late morning to early afternoon hours. Watch for surface wet snow deeper than a few inches, initial roller balls and initial small natural  or triggered loose wet avalanches.

We have lowered the likelihood of triggering an older wind slab avalanche. But it will still be wise to watch for firmer wind transported snow on specific terrain features. The most likely locations are steep slopes below ridges or cross loaded ribs mainly near or above treeline.

Some powder may still found out there on sheltered north slopes. Surface crusts will also abound to bring added enjoyment to your outing.

Snowpack Discussion

About a week of fair weather was centered around the New Year. This allowed the significant snow that fell during a strong storm cycle that ended about Christmas to settle and stabilize.

By New Years Eve through last weekend moderate to strong east-northeast winds had significantly scoured most of the available surface snow, mainly in the near and above treeline elevation bands.

Surface snow sculpted by recent 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. This was followed by about 8-10 inches of snow at Mt Hood early last week.

Laura was out again near the Mt Hood Meadows ski area on Tuesday and Wednesday and reported 5 inches of storm snow had formed small slabs, non-reactive to ski cuts, but some explosive triggered slides up to 10 inches were seen on steep slopes of varied aspects. These shallow slabs were becoming less sensitive by Wednesday as a result of warming temperatures.

On Friday the Mt Hood Meadows pro-patrol reported isolated rollerballs on solar slopes and 5-6 inches of lingering powder on the crust from Monday.

No avalanches have been reported over the past several days on Mt Hood.

Avalanche Problems

Loose Wet

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. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. 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.

 

Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.

 

Several loose wet avalanches, and lots of pinwheels and roller balls.

Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

Aspects: South East, South, South West.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1 - 1

Wind Slabs

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.

 

Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..

 

Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.

 

Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 1