Avalanche Advisory Archive 2016 – 2018

Date Issued:2017-03-19 07:35:10
Primary Trend:3
Primary Probability:3
Primary Likelihood:3
Primary Size:2
Primary Description:

We have seen nearly 36\" of snow this week. WInds were strong during the first two days of the storm. Day one blowing out of the North along the channel... and day two blowing out of the SE and increasing on Douglas Island.

We saw both natural and human triggered slides on these layers this week and they remain reactive... we saw sizable slides human triggered in the backcountry yesterday. Be aware that things are still moving out there and use a little extra caution.

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

With a fairly large storm slab in place... that has multiple weak layers you may see human triggered slides on most any aspect.

Warming over the next 24-36 hours will increase this instability. New snow volumes forecast remain low and yet with moderate winds in the forecast, precip of nearly an inch over 24 hours, and 10f of warming danger levels are increasing on these deep weak layers over the next 24-36 hours.

Use a little extra caution today on all aspects... avalanche danger is lingering...


The National Weather Service Forecasts-

Today- Chance of snow early in the morning, then snow in the afternoon. Snow accumulation 1 to 2 inches. Highs around 35. southeast wind 10 to 15 mph.

Tonight- Not as cold. Snow. Snow accumulation 3 to 6 inches. lows around 34. Southeast wind 10 mph.

Monday- Snow. Rain in the afternoon. Snow accumulation to 2 inches. Snow level 500 feet in the afternoon. Highs around 39. Southeast wind 10 mph.

Earlier this week we saw a fairly good sized storm dump. We had nearly 70cm over a several day window. By the end of the storm the storm totals were roughly 53cm of snow deposited from 69mm of precipitation. Still pretty light density for storm totals not daily totals. This 53cm storm slab has settled quite a bit over the last few days and is now closer to 40cm. Even at that the total density is only roughly 17% which is still fairly light dry snow.

Early on in this storm we saw 20-35mph loading winds from the North. Then they rolled around to the SE for another blow in the same range. So this storm has not only a fairly large storm slab but has windloading on multiple aspects. The winds have been fairly light overall which has not created too much in the way of hard slabs. Most all aspects remain soft.

This weeks storm came after a ten day dry stretch... of cold clear weather which left surface faceting in places. We also had extreme winds at the end of the last storm leaving big hard slabs in places as well.

This March 1st storm also deposited a fair amount of snow in our region. Even today after settling that storm layer is close to 20cm in places.

We have a great deal of weakness in and above these two storm layers. If you look at both layers combined the total densities are still under 17%...

During the first storm we had a great deal of natural avalanche activity removing the deeper instability in many places... yet if you do not know which slopes have already avalanched you should be asking yourself if you are dealing with both slabs and problems...

Most of our primary offenders in the Urban environment slid during the first storm. Snowslide Creek on Thane. the Berhands Avalanche Path, Middle Path on Thane, The White Subdivision... All Slid... but slopes such as Chop Gulley have not and the deeper weak layer remains suspect.

This weeks storm also produced a fair amount of natural activity on Douglas Island. Most slide prone slopes saw activity at some level during the early part of the storm on all angles... yet those reloaded greatly since that time...

For the most part avalanche danger is decreasing... yet we have significant lingering danger in the form of Wind Slabs and Storm Slabs from the last event and two different wind directions. Even yesterday human triggered avalanches were occurring with fairly large slides.

Winds are forecast to pick up today from 10-15mph along the channel in town and closer to 20-25mph on summit. The forecast calls for 4-6\" of snow in the next 24 hours with a warming trend of 10f during that time to end above freezing tomorrow mid day into our mountain zones.

With natural avalanches possible and human triggered avalanches likely the avalanche danger remains CONSIDERABLE today.

Slide activity is not widespread and yet these slides are of size and will run far and fast as they remain low density. So danger is a little lower and consequence is high!

Use good practices in the backcountry. Remember only one person at a time on avalanche prone slopes. Safe spot to safe spot with spotters in place... Avalanche Transceiver, Probe, and Shovel! Don't leave home without them!


Here is a link to an article on: Simple Snowpack Assessment Errors That Can Get You In Trouble


Forecaster:Tom Mattice