Avalanche: Hatcher Pass

Location: Peak 5100 Two-Mile Creek Zone

Route & General Observations

Started tour at Gold Mint lot at around 9am heading for the Two-mile creek zone down gold mint trail with the objective of skiing one of two lines off of Peak 5100. Skier triggered slab avalanche on WNW aspect in couloir on Peak 5100, details below.

Avalanche Details
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Trigger SkierRemote Trigger No
Avalanche Type Soft SlabAspect West Northwest
Elevation 4900ftSlope Angleunknown
Crown Depth 10inWidth 25ft
Vertical Run 70ft  
Near Miss / Accident Details
Number Caught/Carried? 1Number Partially Buried?0
Number Fully Buried?0Number Injured?0
Number Fatalities?0  
Avalanche Details

While skinning up the couloir, partner, who was ~40' up slope of myself, noticed a shooting crack through a slab after a kick turn. After taking another step, a slab avalanche was triggered which released ~6' up slope of skier and immediately swept him off of his feet and carried him down about 60' at a moderate speed. Skier was able to 'swim' and poke over to where a small patch of rocks were and was able to get out of the debris and in a safe spot away from the problem slab. Debris continued on for roughly another 10' until slowly coming to a stop. Crown depth ranged from ~10" at the deepest and ~2" at the thinnest spot, propagating across ~25'. Time of avalanche: ~12:50pm; Skier was thankfully only shook and suffered no injuries.
Additionally, around 30mins before the avalanche was triggered, we observed a small dry loose avalanche naturally release off of some rocks shortly after the sun surprisingly came out. About 10mins after that first small avalanche, we heard a very loud, thundering sound and saw a slightly larger, but way louder, similar looking avalanche release on the same E facing slope neighboring ours.
Pictures of all of this below.

Events of the day

Before leaving for this tour, my partner and I discussed several weather models and recent observations and knowledge of slopes over the past few days in hopes to find something non-solar to ski. We both saw in the weather models and recent weather recorded on Marmot Ridge Wx Station, cold temps (10°F overnight at Marmot Ridge, ~12°F via WINDY), little wind, light snowfall during the day, and cloudy skies all day long with a midday lift in the cloud ceiling. This made us feel good about everything being dry and frozen and stable, with the thought of only needing to do some sluff management while skiing. Things were cold and dry all over as we left gold mint lot, with trace to S-1 snowfall and a low cloud ceiling, as predicted. Though around 11:00am, skies started to clear out to few-scattered clouds for about 45mins and sun effect was strong. Snow surfaces still felt dry and blower so as the clouds quickly came back in thick we continued to feel good about things. We dug a pit to the side of the apron of the couloir we were wanting to ski and had no test results and snowpack was very well consolidated and pretty bomber. As we started climbing up the couloir, well spaced out from each other, things started to firm up a bit but at first it wasn't very slabby and was only so off to the sides of the couloir. As we kept ascending, and after hearing/seeing two avalanches occur on an E face after some heavy sun effect, we were moving a little more cautious but still felt good as what we were on wasn't giving us any red flags. Then, as we got to about halfway up the line, the slab started to get more widespread and started to feel hollow underneath it. Quickly after discussing that we also noticed that the temperatures very quickly increased since we had been in the couloir, very shortly then afterwards, the avalanche occurred. See above for details and below for pictures.
After things settled out and partner gave the ok, I carefully poked over to a side of the couloir where the slab wasn't present and slowly stepped down to partner to regroup and transition. We carefully skied one at a time with eyes on each other the whole time and made it back to the car without further incident.

Rescue events

Thankfully no rescue needed

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

Saw somewhat recent loose avalanche debris in another couloir off of Peak 5100, observed shooting cracks (20' high energy) just before avalanche was triggered, saw multiple loose avalanches occur on a sun effected east face.
Midday we also observed rapid warming, mostly believed to be from an intense greenhouse effect as the sun was intermittently poking through the clouds.

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

Up until around 11am weather stayed consistent with forecast models, cloudy skies, low clouds lifting higher by midday, bad vis, light precipitation, and temps in the teens and low 20s. Around 11am, clouds lifted and nearly cleared for ~45mins and temps began to rapidly rise. Around 12pm clouds came back only then to clear out slightly to scattered by 1:30pm. Very very warm temps by midday and early afternoon, in the sun it felt like 40°F+. New snow accumulation of roughly 2-3cm.
Overall we were very surprised at how the weather took a turn, ended up being very different from the forecasted models we saw on windy.

Snow surface

In the morning surface was dry and blower new snow. By later in the day (12pm) snow surface began to quickly get moist on all aspects, and by the early afternoon surface was moist-wet and was glopping to our skis like crazy.


Dug a quick snowpit on a NNW aspect at ~4600', height of snowpack at location was ~215cm deep. Performed two CT tests and had no results, observed no concerning structure in our pit.

Photos & Video
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