Hatcher Pass
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The Bottom Line
Triggering a slab avalanche 1-3 feet deep will be possible in specific locations at all elevations on slopes steeper than 30º. More likely locations are South to West aspects where recent winds have drifted snow.
Obvious signs of instability may not be present. Shooting cracks and whumphing are red flags.
Avalanches may fail above you, making escape difficult to impossible.
Avoid large slopes above terrain traps.
The historic Bora wind event (more info on Bora in AK) on January 2-3 which resulted in significant damages throughout the Mat-Su Valley and an emergency declaration by the Borough and State, were less significant at Hatcher Pass. While wind loading and drifted caused several large avalanches on Marmot Mountain, the peak gusts at the Marmot weather station were recorded at 44mph compared the the much stronger 90+mph winds recorded in Palmer.
Winds are forecasted to remain calm today, but spike again on Friday to 56mph, which could cause another increase in danger and avalanches. Special weather statement here.
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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. |
We observed several large natural avalanches failing at or near the ground occurring on 1/2-3 due to the strong Bora wind event. All of these occurred on the SE side of Marmot Mountain above the road between Gully 1-3, to the observer’s left of President’s Ridge. One avalanche came within 100′ of hitting the road. These avalanches are significant and an indication yet again that we are dealing with a dangerous snowpack whose problems are not going away.
1/3/2022 – Marmot Gully 2 Natural slab avalanche
1/2/2022 – Marmot Gully 1 Natural slab avalanche
1/2/2022 – Same avalanche as above, debris pile ~100′ from road
| 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 |
Widespread weak sugary snow buried in the snowpack is the layer of concern. The problem exists on all aspects, at the all elevations, on slopes steeper than 30º where stiff, strong snow (slabs), 1-3′ deep, sit on these weak layers and may be possible to human trigger. Triggering a slab avalanche will generally be large in size, making escape difficult to impossible. Locations lacking this hazard will be slopes 25° and less and clear of the runnout of steeper slopes from above.
Identifying exactly where this will occur will be difficult to predict, even for the expert. It may not be the first person on slope that triggers an avalanche, and it may be triggered well above the person, increasing the risk and consequence of the avalanche.
Some recent natural avalanches provide evidence for problematic areas where human triggering an avalanche may be more likely. These locations are mid to upper elevations on leeward slopes, S to W, where the recent ENE Bora winds transported and drifted snow on 1/2-3. The more southerly slopes have maintained thinner snowpacks through the season, weaker problem layers, now with recent drifted snow on top, and therefore may be easier to human trigger. While these slopes may be more suspect, it’s important to recognize that poor structure in the snowpack is widespread and triggering a slab avalanche will be possible in a variety of locations.
Bora Wind Event
When uncertainty is high for predicting avalanches, we increase our safety margins with stricter travel protocol. We will be doing this by making conservative decisions, traveling from safe zone to safe zone one at a time through exposed areas, avoiding large slopes above terrain traps, and using good communication including radios. As always we will all be carrying and know how to use the appropriate safety gear for companion rescue.
This video shows a propagation saw test. The results are less than ideal and indicate that the snowpack is capable of avalanching. Much of the testing we have conducted has been producing mixed results. This supports our assessment that there is a lot of variability in the snowpack, with some places that are more problematic than others. What we can not tell you is exactly where and when a person may trigger an avalanche.
