Hatcher Pass
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The Bottom Line
It will be possible to human trigger 12 to 18″ thick persistent slabs at all elevations, on SW to NE aspects today.
It will be possible to human trigger 2 to 6″ thick wind slabs at mid and upper elevation, on W to N aspects today. Naturals are unlikely.
Winds events on 12/5-6 and 12/9 have transformed the snowpack and conditions at Hatcher Pass, scouring ridges, loading leeward aspects, and making powder hard to find.
Heads up! Winds are forecasted to increase Sunday which will increase the avalanche danger.
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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. |
Strong winds on 12/9 drifted snow which overloaded the persistent weak layer resulting in a number of mostly small natural persistent slab avalanche releases.
12/9 Marmot gully 1. Natural cornice fall/wind slab gouges out the facets 3200′ S aspect
12/9 Marmot South ridge. Natural avalanche, persistent slab, 3200′ S aspect
12/9 Near Marmot Mid-rib. Natural avalanche, small persistent slab, 3600′ NW aspect
12/9 Marmot, Death Gully. Natural avalanche, persistent slab, 4000′ NW
12/9 Marmot SW Face, Natural wind slab, 4500′ SE
12/8 Fishhook Creek. Human triggered slab avalanche 3000′, NE. New snow and wind blown snow have masked evidence.
| 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 |
12 to 18″ thick Persistent Slabs will be POSSIBLE to HUMAN TRIGGER today on SW to NE aspects at all elevations. Naturals avalanches are unlikely.
Until this week, the snowpack at Hatcher Pass has lacked a slab. Our least favorite but most talked about problem, the persistent slab, has returned to the forecast.
Persistent slabs are sitting on weak sugary snow which encompasses the entire base of the snowpack. Stiff snow sitting over weak snow is widespread. However the persistent slab problem is more prevalent and reactive on SW to NE aspects where winds have drifted and loaded snow.
This slab varies from 1F+hardness to 4F hardness. Hard slabs can be dangerous because they are capable of breaking above you and not just at your feet like soft slabs. Hard slabs can be stubborn to trigger, can propagate further, and can be harder to escape.
Stay out of harms way by identifying and avoiding these slabs, spacing out across the slope, and using appropriate safe zones. Use pole tests and hand shears to help identify the persistent slab with hard snow sitting over soft snow.
Whumping, shooting cracks, and recently human triggered avalanches will be red flags for this avalanche problem.
Expect this avalanche problem to persist in the snowpack for awhile.
The video below shows the persistent slab problem at mid elevation on Friday with reactive results.
| 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 |
Winds gusting ESE 20 to 37mph for 15 hours on 12/9 formed 2 to 6″ thick wind slabs on W to N aspects at mid and upper elevation. These wind slabs will be possible to human trigger today. Naturals will be unlikely.
It will be possible for these wind slabs to step down to the persistent slab, increasing the size and consequence of the avalanche.
Wind drifted snow, smooth lens shaped features, and scalloped snow can be used to identify this avalanche problem.
Whumping and shooting cracks will be red flags for this avalanche problem.
Expect this avalanche problem to heal within 24-48 hours.
12/9 Cross Loading/ Wind loaded. Avoid these loaded zones!
12/9 Wind scoured ridgeline on Hatch
1” of new snow accumulated overnight at Frosty Bottom (2500’) and IM snotels (3550’). Winds calmed down early yesterday morning, remaining calm overnight. Temperatures have dipped into the teens this morning, and are forecast to drop just below zero today and possibly as low as -15℉ Monday morning. A cold clearing trend is forecasted today through Monday. Winds may pick up beginning Sunday. Strong winds will have the ability to once again transport and drift snow, which will be able to overload our weak poor structure in the snowpack and increase the avalanche hazard.
NWS AVG Forecast here.
NWS Rec Forecast here.
NWS point forecast here.
State Parks Snow Report and Motorized Access information here.
