Avalanche Advisory Archive 2016 – 2018

Date Issued:2017-03-14 08:20:38
Primary Trend:2
Primary Probability:1
Primary Likelihood:4
Primary Size:2
Primary Description:

It wont take much snow moving to get thing rolling... as snow cleans off of steep faces trees and rocks it may be enough to trigger fairly large loose dry snow avalanches that will be traveling fast and far.

Use increase caution today on all aspects as these may occur anyplace. Be aware that skiers may also be kicking off loose snow slides that often step down and out to Slab Avalanches.

Secondary Trend:3
Secondary Probability:3
Secondary Likelihood:4
Secondary Size:2
Secondary Description:

Dangers are present in the form of windslabs. We had loading winds along the channel from the North and on Douglas additionally from the SE.

Soft slabs were noted yesterday and in areas with wind things were increasingly sensative. Please use caution in wind loaded areas and realize danger is HIGH today. Expect to see activity on steep faces.


The National Weather Service Forecasts-

Today- Snow and rain. Snow accumulation to 2 inches. Snow level rising to 200 feet. Highs around 34. Northeast wind 10 to 20 mph shifting to the southeast 10 to 15 mph in the late morning.

Tonight- Rain in the evening then snow. Snow accumulation to 3 inches. Lows around 31. South wind 10 mph shifting to the east late.

Wednesday- Snow and rain likely. Snow accumulation to 1 inch. Highs around 36. East wind 10 to 15 mph

We have received a fair amount of snow around the region over the last 48 hours. Eaglecrest is showing around 14\" of light density snow and the Mt Roberts Tram is showing closer to 16\".

The majority of that came in the first 36 hours. Yesterday the tram picked up about 6\" while Eaglecrest is showing around 4\"

At the beginning of the storm winds along the channel were strong from the north blowing 20 to 30 which surely laid down a wind slab on the aspects along the channel. Douglas Island saw less wind during this time but it still was enough to form soft slabs in places. Yesterday winds shifted direction and although they remained light along the channel they did pick up to 10-20 on Douglas. This light snow transports easily and I assume this was enough to build additional soft slabs in places that may be weak.

This new snow came to rest on a varied bed surface. Yesterday I noted facets in the trees. More old hardened windslab along ridgeline and summit. The new snow is not bonding well to the old snow surface in most places. We definitely have several weak layers present from the test I conducted yet in most places the slab had yet not formed enough to be highly reactive. Any areas with additional winds since that time may be even more reactive. My test scores were very low with CT5 and ECT7... PST of 35.

Temperatures are forecast to climb again today adding to the possible instability in the equation.

Yesterday some loose natural avalanches were noted as well as human triggered loose snow avalanches and soft slab avalanches.

The slides were fast and far and yet consequence was low with the light snow... as the slab stiffness increases danger will potentially increase and so will consequence.

Due to the large volumes of snow, and avalanche activity yesterday avalanche danger remain HIGH today.

Both natural and human triggered avalanches likely. Simply snow falling off of trees and cleaning itself from steep rock faces may be enough to triggers both loose and slab avalanches today in places.

Once again these would be fairly large fast avalanches. Please use additional caution in avalanche terrain.


Know the avalanche types.

There are several types of avalanches possible, each dependent on the terrain, steepness, and weather:

Loose dry-snow avalanches ? These can be very large. They start at a single point and can move at 40 mph / 64.3 km/h, and at that speed can easily become airborne.

Airborne powder avalanches ? Once airborne at a speed of around 40 mph / 64.3 km/h, these are very destructive and can reach speeds up to 175 mph / 280 km/h.

Slab avalanches ? If a slab of snow ceases to be supported, it is easy for it to fall away. Snow accumulates on leeward slopes due to wind and unsettled snow creates soft slabs that are easily triggered by avalanche victims. Hard slabs form on lee slopes where winds are over 30 mph / 48.2 km/h and the slab turns as hard as concrete. The breaking of such a slab can be heard as a huge cracking noise.

Wet avalanches ? These are common during spring months or following thaws, as water weakens any layers of snow, including down to the ground level. Wet avalanches can be loose or slab, fast or slow, and set like concrete once they stop making rescue time for victims extremely short. These often occur following heavy rain or a snowstorm that starts cold but ends warm.

Ice avalanches ? Ice peels off a crag and falls down the mountainside.

Cornice collapse ? Cornices (deposits of wind-drifted snow) can collapse under their own weight, or following a heavy snowfall.

Forecaster:Tom Mattice