Hatcher Pass
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The Bottom Line
Persistent slabs will be possible to human trigger today on all aspects at upper elevation. Large avalanches will be possible in isolated locations on southerly aspects where stiffer snow overlies weaker snow. Persistent slabs will be unlikely to trigger on all aspects, at mid and low elevation. Low danger does not mean no danger.
Small, dry loose sluffs will be possible to human trigger in steep locations, on slopes 40º and steeper, on all aspects, at all elevation.
NWS is forecasting for 1-3″ of new snow above 1000′ today.
Terrain choice will be key today for avoiding avalanches and finding the best square powder in a environment that consists of highly variable snow conditions. Let’s hope that Winter Solstice brings us some snow!
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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. |
No recent avalanches have been observed since 12/5-12/8.
| 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 |
This problem’s behavior will be difficult to predict. Use safe travel protocol and choose slopes without terrain traps. Making conservative terrain choices will be our decision making tool of the weekend.
Persistent slabs 1-3 feet deep, will be possible to human trigger today in isolated locations at the upper elevation on all aspects. More likely locations for triggering a large persistent slab are on southerly aspects where previously cross-loaded features contain firm snow overly weaker snow. It will be unlikely to trigger persistent slabs on all aspects, at mid and low elevation.
Although the last human triggered avalanche occurred almost 11-14 days ago, the snowpack continues to resemble a sandbox (of facets) with a slab of varying thickness on top. Be cautious of varying slab thickness. It will be easier to trigger an avalanche from a location where the slab is thinner. Hard slabs tend to allow you to get out on slope before breaking above you, increasing the hazard and diminishing the likelihood of getting off the slab.
In isolated areas, remotely triggering a hard slab avalanche is still possible. In this case you will be able to trigger an avalanche in the flats below steeper slopes or in adjacent terrain. You could unknowingly remotely trigger an avalanche which puts other parties at risk, or trigger an avalanche above you.
A few test results are not indicative of the entire snowpack stability picture. Use multiple pole tests, hand shears, and instability tests for a more accurate assessment of the problem. Whumphing and shooting cracks are red flags.
Below is a video from a south facing slope at 3000′, showing the entire, shallow snowpack consisting of weak, faceted snow. These zones will be the best for riding and skiing.
Below is pit from the same area as the video above. It is showing consistent results with other recent pits: Poor structure, moderate to strong strength, and poor propagation potential.
Below is a good overview of the Persistent Slab Problem. Click on the photo to link to a page describing all avalanche problems.
Looking to the future: When another loading event occurs, such as 12″ of new snow or 6″ of new snow combined with strong wind, it will likely be enough to stress the weak layers and result in another avalanche cycle.
| 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 |
1-3″ of new, low density snow is expected today. In wind sheltered areas, approximately 3-4″ of old, low density snow exists. The combination of new snow and old snow will add up to 3-7″ of low density snow by the end of today, which could be triggered as loose dry avalanches in steep terrain.
Small dry loose sluffs will be possible to human trigger today on steep slopes, 40º and steeper , on all aspects, at all elevations. Even a small dry loose can can have a large consequence if the terrain funnels into a terrain trap, over a cliff, or drags you through shallow, rocky terrain.
New snow totals 12/13-19:
Independence Mine: 1-2″ overnight
Frostbite bottom: 1″ overnight
Last significant precipitation, 3-4″ on 12/8.
NWS is forecasting a 90% chance for 1-3″ of new snow above 1000′ today. Winds are forecasted to remain light. Overnight gusts at Marmot (4500′) were mostly light, with some moderate gusts. Temps should be in the lower 20’s today, dipping into single digits overnight at 1-3000′.
Marmot Weather Station:
Temps this week:
Winds overnight:
Independence Mine Snotel (3550′)
Temps this week:
Frosty Bottom Snotel (2700′)
Temps this week:
NWS Rec Forecast here.
NWS point forecast here.
State Parks Snow Report and Motorized Access information here.
