Avalanche Advisory Archive 2016 – 2018

Date Issued:2017-02-15 06:50:35
Primary Trend:1
Primary Probability:7
Primary Likelihood:2
Primary Size:2
Primary Description:

With several days of the warmest temperatures of the year and several inches of rain, wet slab avalanches remain the greatest concern. Both in the new snow layers from last week and full depth in isolated unanchored locations.

As temps continue to cool stability will increase.

Secondary Trend:1
Secondary Probability:6
Secondary Likelihood:2
Secondary Size:1
Secondary Description:

Wet loose avalanches also remain possible as snow cleans and falls off of rocks and other objects. This can easily start wet loose avalanches when conditions are continually this warm.


The National Weather Service Forecasts-

Today- Rain. Highs around 45. Southeast wind 10 to 20 mph diminishing in the afternoon.

Tonight- Decreasing clouds. Colder. Scattered rain showers in the evening. Patchy fog and freezing fog developing by late evening. Lows around 30. North wind 10 to 15 mph.

Thursday- Partly cloudy. Patchy freezing fog in the morning. Highs around 40. Northwest wind 10 mph.

From January 29th to February 10th we had essentially no new snow. It was mostly clear with some wind during this time. We did develop a faceted layer on much of Douglas Island.

Since last Friday Feb 10th at 10 am we have seen another big storm system roll through SE Alaska. This brought big warming, precipitation, snow, and rain both.. and continued 30-70mph winds.

This system started off quite cold at -6c at Eaglecrest and the Tram Summit both. We picked up 43cm of snow at Eaglecrest and 54cm of new snow off the tram summit before the warming hit too hard. Temps climbed by 10c at Eaglecrest and 12c on the Mt Roberts Tram summit. This combination of wind, warming, and heavy precipitation was enough to kick us into a widespread natural avalanche cycle. Most of our repeat offender avalanche paths have run in the last few days since the biggest part of the storm Saturday night. The storm left a total of 130mm of precipitation in the region (about 5\" over 5 days) This is significant loading. After the warming we continued to see these rains. Since that time the snowpack has lost nearly 10\" at Powder Patch on Eaglecrest and more than double that with 21\" of snow loss at the tram summit.

This large warming, rain, avalanche, and settlement event is slowly starting to create a more stable snowpack.

Temperatures have cooled this morning Eaglecrest was 41f mid mountain yesterday and is holding at 35f this morning. Mt Roberts was 43f yesterday morning and is 36f this am. The forecast calls for another 7f of cooling over the next 48 hours back to below the point of freezing.

By now the snowpack has developed the ability to process the precipitation. The forecast calls for another 1/4\" of precipitation today which isn't a great deal.

With cooling temperatures in the forecast during light rains onto an already settled snowpack with drainage in place... Avalanche Danger is MODERATE today. Natural avalanches are unlikely. Human triggered avalanches may still be possible.

Basically until the snow goes back to below freezing we have some instability remaining. We may see wet loose avalanches, glide avalanches, or full depth slab avalanches on super steep slopes. Especially convex unsupported rocky slopes with few or no anchors. These areas will continue to clean off until the snowpack freezes once again.

A great deal of activity is not in the forecast and yet with wet avalanches there always remains a concern.

Small wet loose avalanches may also be seen as the snowpack continues to clean off features.


here is an interesting link to an article on:

What Causes Avalanches and Can I Predict One??


Forecaster:Tom Mattice