Hatcher Pass
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The Bottom Line
Small human triggered Wind Slabs are possible in isolated areas. These wind slabs will be found at upper elevations, on Northwest thru East aspects. Natural avalanches are unlikely.
A rain crust 2” thick can be found up to 4500’ in Hatcher Pass. Falling on any steep slope could result in sliding hundreds of feet.
A Significant rain event occurred on Dec 26th in Hatcher Pass. Time and cold temperature have allowed the snowpack to gain stability rapidly. Riding quality is poor.
Persistent slab avalanches are possible in isolated areas at upper and mid elevations, on all aspects. Avalanches will be small to large in size, natural avalanches are unlikely.
Special AnnouncementsJoin the forecasters on Thursday, January 13 from 4-5pm at the Hatcher Pass Lodge for our first “Forecaster Chat.” Come hear what we have to say about the snowpack and check out our new Swag!
You may have noticed the Marmot wind speeds were not reporting since December 27th. Forecasters were up at the weather station yesterday clearing 1.5” of ice from the station and the anemometer is now up and running again!
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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. |
There were several natural avalanches that occurred during 12/26’s weather event. On 12/29 several natural avalanches were observed.
Sky Scrapper, small natural avalanche. This likely occurred on Dec 28th late in the evening.
2″ rain crust on lower Marmot.
| 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 on Dec 28th and 29th were able to transport some small amounts of snow and form wind slabs in isolated areas. These wind slabs will be found on Northwest to East aspects at upper elevations and will be up to 4” thick. These wind slabs have bonded well to the underlying snow, this problem will likely be short lived.
Marmot weather station was completely frozen under 1.5” of ice so there is some uncertainty on wind speeds and direction at upper elevations. HPAC forecasters were in the field on 12/29 and experienced strong winds from the west, with gusts estimated around 40 mph.
Smooth wind drifted snow will be a sign that wind slabs are present. Use hand pits and poles/probes to identify this avalanche problem. Cross loaded gullies and leeward features are areas where this problem will be found. This problem should be pretty easy to identify since most slopes are covered in a rain crust up to 2” thick.
The rain crust that formed on Dec 26th is widespread and was observed up to 4500’ feet. This crust is up to 2” thick and is supportable. This has left us with horrendous riding conditions. Another problem with this rain crust is that it has created extremely challenging travel conditions. Sliding for your life on smooth, firm surfaces is a real concern if you choose to travel on steep slopes.
Thousand Dollar Run. This photo is a great example of the current distribution of wind slabs.
2″ rain crust on lower Marmot.
Exposed rocks are covered in ice.
| 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 slab avalanches are possible in isolated areas at upper and mid elevations, on all aspects.
On Dec 26th an abnormal weather event occurred in Hatcher Pass. Rain and warm weather decimated the snowpack and dropped 1” of water on the snowpack. On Dec 28th another inch of water fell on the snowpack. During this storm natural avalanches occurred.
The peak of avalanche activity occurred on 12/27, see forecaster observation here for photos. Several factors are contributing to a significant increase in stability. Recent water saturation of the snowpack, significant surface crust formation, a melt/freeze cycle with cold temperatures dropping into the teens, and several days out from the peak of the avalanche cycle have all allowed for the snowpack to gain stability.
While stability has improved, it will still be possible, but difficult to trigger a persistent slab avalanche. Areas that may be problematic include broad slopes above 3000’ where the snowpack was not saturated with rain water. Snowmachiners and large groups of people crowded together could be enough weight to trigger a persistent slab avalanche in an isolated location.The rain crust that formed is not uniform in all areas. While it supports body weight in most areas it is breakable in other locations. In areas that crust doesn’t support body weight, it will be easier to affect the weak sugar facets underneath.
At lower elevations the snowpack was saturated with water. We believe that the snowpack has likely refrozen due to cold temperatures and that persistent slab avalanches will not be an issue.
If you do trigger an avalanche it will likely fail at the ground and be large in size.
If you choose to play on some of the worst riding conditions imaginable, practice low risk travel techniques. Space out when ascending slopes, descend one at a time and stop well out of harm’s way.
