Avalanche Forecast

Archived

Feb 7th, 2017–Feb 8th, 2017

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural and human triggered avalanches likely.

Regions

Mt Hood.

An approaching storm Wednesday will load and stress the deep recent storm snow Wednesday. Watch for changing conditions and be prepared to alter tour plans and leave plenty of safety margin. Natural or triggered avalanches will become increasingly likely later Wednesday.

Detailed Forecast

An approaching storm will bring increasing clouds and strengthening winds through the morning Wednesday. Snowfall will arrive Wednesday morning and increase through the afternoon with warming.

The warming and beginning of the new snow loading Wednesday, will begin to stress the significant recent storm snow. The avalanche danger will increase through the afternoon Wednesday, however the significant loading and heavier precipitation rates are likely to hold off until Wednesday night and into Thursday.

If the approaching storm arrives sooner than forecast or with, initially heavy precipitation, the avalanche danger could increase more rapidly than expected. Watch for changing conditions and be prepared to alter plans accordingly.

Natural and triggered avalanches will become increasingly likely through the day Wednesday.

Snowpack Discussion

Weather and Snowpack

A strong storm cycle began Friday with 3-4 feet of snow recorded at the Mt Hood area stations on average, through Monday afternoon. A warming trend affected all areas Sunday. Moderate W-SW transport winds were recorded near and above treeline for much of the weekend. Strong westerly winds persisted Monday.

Light snowfall occurred Tuesday, depositing about 2-3 inches of new snow with fairly light winds.

Recent Observations

Mt. Hood Meadows pro-patrol had a busy day on Saturday with sensitive but generally shallow storm slabs easily releasing during control on a density change in the storm snow. Wind loaded NE slopes between 5500-6500 ft ran well during control work with crowns locally up to 2'.

On Sunday morning Meadows pro-patrol found storm slabs on all aspects of about 1 ft that were especially sensitive below treeline. E-NE aspects were being continuously loaded near and above treeline throughout the day.

By Tuesday, reports of settling storm snow made avalanche control work less exciting, as avalanches were very limited to isolated wind loaded pockets. This is a good indication of improving conditions, at least for Tuesday!

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.