Avalanche: Hatcher Pass

Location: Rae Wallace

Route & General Observations

Today we covered quite a lot of area to see how conditions were changing with the current storm. We toured up to the Rae Wallace boot pack, started up the boot pack and turned around part way up after deciding we didn’t like the deteriorating conditions. Then we headed back downhill, skied the road run and then toured up Japanese trees.

Leaving the IM mine trailhead and on the way to Ray Wallace we encountered encountered a lot of graupel snow and poor visibility. The graupel helped us not feel the bottom so much and added a little body to the new snow. The real wind hadn’t really gotten going yet so storm slabs were nascent, soft and cracking was localized to our skis until we got to the couloir.

Shortly after we transitioned to booting we triggered a small slab within the new snow. With all the unconsolidated graupel the slide was loose and fast and just kind of washed around us. We felt like we had gathered enough information on how the new snow was bonding and setting up that we transitioned and headed for lower elevations.

Lower down we found a similar amount of new snow but the overall lack of wind effect limited any slabbing.

Avalanche Details
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Trigger Foot PenetrationRemote Trigger Yes
Avalanche Type Soft SlabAspect North
Elevation 4200ftSlope Angle 38deg
Crown Depth 4inWidth 30ft
Vertical Run 70ft  
Avalanche Details

We remote triggered a small (D1) soft slab on the Rae Wallace boot back. The crown varied from 2-8 inches thick and propagated about 50 feet uphill from us as well as along the side of the couloir.

Before triggering this slide we had encountered little cracking and no collapsing. The storm slab was still soft and shallow. I’d guess we were there at the height of instability and with the additional wind and loading throughout the day I’d expect the new snow to have set up a little more and become slightly more stiff and stubborn.

Red Flags
Red flags are simple visual clues that are a sign of potential avalanche danger. Please record any sign of red flags below.
Obvious signs of instability
Recent Avalanches?Yes
Collapsing (Whumphing)?No
Cracking (Shooting cracks)?Yes
Observer Comments

Active loading with periods of strong snow and wind were the biggest red flag. For the most part new snow seemed to be bonding well to the old snow surface but less so where the old surface was very firm or slick. Cracking was mostly localized to our skin track. The graupel helped add a little body to the slab, and with the additional wind and accumulation since we left the hill I’d expect storm slabs to have become a tad stiffer and more well connected.

*Note that we did not observe any recent avalanches prior to our tour because visibility was poor and deteriorated throughout the day.

Weather & Snow Characteristics
Please provide details to help us determine the weather and snowpack during the time this observation took place.

We arrived to the IM parking lot to heavy graupel, light winds and poor visibility. By the time we turned around in Rae Wallace winds had increased to moderate (gusts 25 on Marmot) and visibility was basically 0. The graupel continued most of our tour starting to switch back to snowflakes right at the end. The temperature was 25 degrees at the Archangel lot and 16 degrees at Marmot ridge at 1PM.

Snow surface

There was about 4-6 inches of fresh snow with 2-3 inches of graupel on top. It skis pretty well- you can still feel the hard crust underneath and skinning on steep sidehills is still tough but a giant improvement from what it was.


The graupel is adding enough weight at upper elevations to create reactive soft storm slabs. It is also worth noting that the graupel makes sluffs move quickly. Places with smooth crust underneath is an ideal bed surface for both storm slab and and dry loose. Down in the Japanese trees (around 1500') the new snow did not seem cohesive enough to form slabs and was not reactive on test slopes aside from dry loose.

Photos & Video
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