Hatcher Pass

There have been a ton of folks out in the mountains over the last week. There have been a several human triggered slab avalanches, one of which could’ve had serious consequences. Click here to see observations. Some avalanches that have occurred are outside the forecast area. 

Snowmachine triggered avalanche on March 13th, Sydney Creek 4000′ NNW 40 agree slope. Click here for more info.

On March 16th, forecasters remotely triggered two avalanches on Stair Step. NW aspect, 3800′ on a 38 degree slope.

Winds from the ESE blew for 10 hours with gusts up 28mph at Marmot Station(4500’). These winds were able to transport low density snow and create stiff hard slabs 6-18” thick. Wind slabs will be found at upper elevations at and below ridge lines on West, Northwest and North Aspects, on slopes 35º degrees and steeper. Human triggered avalanches are possible, natural avalanches are unlikely. These avalanches will be small in size. Winds were stronger at the south end of the forecast zone. Anticipate thicker slabs on Arkose Ridge. The Independence Mine area will likely have thinner slabs. Forecasters remotely triggered two small wind slabs on wednesday, click here for more info.

To identify this avalanche problem use pole/probe, hand pits and formal stability tests. Look for stiff hard snow sitting on top of low density snow. Shooting cracks and whumping will be red flags for this avalanche problem. Look for smooth wind drifted snow to visually identify this problem. 

Obvious signs of wind loading. On the left side of the slope(windward) the snow was eroded by the wind down to the Feb24th melt freeze crust.

Winds were strong enough to create stiff hard slabs. Use safe travel protocol if you decide to venture into steep terrain. Spread out when ascending slopes, descend one at a time, and regroup well out of harm’s way. Even a small avalanche can have severe consequences if traveling above cliffs, gullies and other hazards. Wind slabs are typically a short lived problem and will gain stability quickly.

Remotely triggered wind slab on Stair Step on March 16th. 3800′ NW aspect, 38 degree slope.

We are confident that buried surface hoar(BSH) is responsible for several human triggered avalanches over the weekend. This BSH is sitting on top of a crust that formed on Feb 26th and sits 10-16” below the surface. So far we’ve found BSH at upper elevations(3500’-4500’) on West, Northwest, North and Northeast aspects. Human triggered avalanches are possible on slopes 30º and steeper. These avalanches will be isolated and  large in size. Although its possible to trigger this problem it will be hard to find a location where BSH is standing up. Natural Avalanches are unlikely.

Snowmachine triggered avalanche on March 13th, Sydney Creek 4000′ NNW 40 agree slope.

To identify this avalanche problem use hand pits, pole/probes and formal stability tests. Look for the Feb 26th crust and see if you find any BSH sitting above it. If you do please submit an observation here. Buried Surface Hoar can be tricky to find and can even be missed by seasoned backcountry travelers. 

Whumping and shooting cracks are red flags for this avalanche problem. However it will be possible to trigger an avalanche without observing these red flags prior.

Surface hoar in the center of the photo.

Warm temps and warming from the sun will cause snow surfaces to become moist in the afternoon. Human triggered wet loose avalanches are likely, Natural avalanches are possible. These avalanches will be small in size. These avalanches will be found at low and mid elevations on SE, S and SW aspects. Wet loose avalanches often occur underneath rock bands. 

Identifying this avalanche problem should be pretty easy and not take a lot of effort. Look for roller balls on steep slopes. If you can easily make a snowball, it’s a sign that surfaces are warming. Wet loose avalanches can gain mass and speed quickly. These avalanches can be dangerous if you’re above cliffs, rocks or other hazards.

Loose Wet avalanche on Marmot