Hatcher Pass
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The Bottom Line
The avalanche hazard is MODERATE for PERSISTENT SLABS on all aspects, at all elevations, on slopes steeper than 30º.
You are most likely to trigger an avalanche where the wind has formed drifts or stiffened snow surfaces. Slabs will be thickest above 3500 feet. Large avalanches failing on weak faceted snow near the base of the snowpack will be possible to human trigger.
Strong wind early in the week has transformed and scoured much of the terrain at Hatcher Pass creating variable conditions with firm surfaces, sastrugi, and few pockets of powder. Low angle protected terrain will be the best choice for enjoying the backcountry today.
Special AnnouncementsJoin HPAC as we host local guide, avalanche instructor, and author Joe Stock for a presentation marking the release of his newest book, “The Avalanche Factor.” Joe will talk about the book and dive into one of its topics, luck and avalanches.
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| Travel Advice | Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. | Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. | Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. | Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. | Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain. |
| Likelihood of Avalanches | Natural and human-triggered avalanches unlikely. | Natural avalanches unlikely; human-triggered avalanches possible. | Natural avalanches possible; human-triggered avalanches likely. | Natural avalanches likely; human-triggered avalanches very likely. | Natural and human-triggered avalanches certain. |
| Avalanche Size and Distribution | Small avalanches in isolated areas or extreme terrain. | Small avalanches in specific areas; or large avalanches in isolated areas. | Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. | Large avalanches in many areas; or very large avalanches in specific areas. | Very large avalanches in many areas. |
Two small natural wind slabs were observed in the Firn path off Marmot and Marmot 1 gully that occurred as a result of the wind event on 11/20 (no pics). No other recent avalanches were observed on Friday.
Two avalanches were remotely triggered on Saturday, 11/18 seen below. More info in obs here.
11.18 Cracking that occurred during a skier descent on the SW face of Marmot that additionally remotely triggered two avalanches on opposite sides of the mountain.
11.18 Death Gully, remotely triggered by skier on SW face several hundred yards away. SS-ASr-D2.5-O
11.18 Looking up at the Death Gully avalanche
11.18 Death Gully avalanche crowns and runnout
11.18 Marmot SE face (Marmot2 gully) remotely triggered by skier on SW face. SS-ASr-D1.5-O
Unfortunately, Mondays wind event transformed HP from the powder haven it was just a week ago.
11.22 Marmot south ridge wind textured surfaces are contributing to variable conditions.
| Signal Word | Size (D scale) | Simple Descriptor |
| Small | 1 | Unlikely to bury a person |
| Large | 2 | Can bury a person |
| Very Large | 3 | Can destroy a house |
| Historic | 4 & 5 | Can destroy part or all of a village |
Persistent slabs up to 3 feet thick will be possible to human trigger in specific locations, on all aspects, at all elevations. We saw evidence of this problem with last Saturdays two remotely triggered avalanches followed by Mondays wind event which loaded leeward slopes, adding stress to an already weak snowpack. The good news is the continuity of the weak layer does not exist everywhere so finding a slab/weak layer combo may be challenging/less likely. The bad news is if you do find a location where this recipe exists, triggering a large avalanche will be possible.
Remotely triggered avalanches will be possible from below, above, or adjacent to slopes. This type of avalanche problem often gives unreliable feedback. Cracking and whumping may or may not occur prior to triggering an avalanche. Pole/probe tests and formal stability tests will help you identify stiffer snow over weaker snow and where this problem exists.
Expect the persistent slab problem to become more reactive with the next storm cycle or loading event.
The video below is from our tour on Friday and shows propagation on the basal facet layer near the ground with ECT and PST instability tests. More info in Friday observations here.
Winds continued to gust from the southeast from 30-34mph for 7 hours overnight before calming down early this morning. You may encounter a few thin winds slabs today. Expect them to be isolated, stubborn and and bonded well especially with todays mild weather hovering around 30ºF at 3000 feet. Most importantly, wherever wind slabs exist expect the persistent weak layer to be more of a problem.
If you head into avalanche terrain today, utilize strict safety travel protocols, travel one at a time from safe zone to safe zone, only have one person on slope at a time, ensure all members of your party are carrying and know how to use beacons, shovels and probes, and avoid slopes with terrain traps.
