Early Season Update, Thursday, November 7, 2017

Issued: Tue, Nov 07, 2017 at 8AM

Expires: Wed, Nov 08, 2017

Above 3,500ft None

2,500 to 3,500ft None

Below 2,500ft None

Degrees of Avalanche Danger ?

1. Low
2. Moderate
3. Considerable
4. High
5. Extreme

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

Recent Avalanche Activity

Recent Weather

Additional Info & Media

UPDATE 11/7:

The peak of the Halloween Zombie Avalanche Cycle (HZAC) has passed. As of yesterday’s observations , the associated weak layers appear to be in a state of dormancy, slowly stabilizing towards inactivity. This does not mean that avalanches are not possible, it just means that the size and frequency of avalanches has decreased significantly. The last reported human triggered avalanche was on November 4, click here for more information.

Many layers in the snowpack are still a cause for concern, but they will need another load to activate on a large scale. A few crusts and weak faceted layers sandwiched between cohesive snow should be watched carefully as winds load the snowpack this week and potentially re-activate weak layers buried in the snowpack.

North to East winds yesterday were quite strong along the periphery of Hatcher Pass, mostly at the upper-most elevations, ridgelines, mountain peaks, and through passes at mid to upper elevations. The brunt of the wind appeared to be along the frontal mountains along the Matanuska and Susitna Valley’s. Winds have picked up this morning, but are forecasted to taper later today.

Wind slabs were beginning to build early yesterday and likely reached critical size overnight. They will continue to build today. These wind slabs are forming on top of near surface faceted snow which is weak and will be reactive. Expect wind slabs on the leeward aspects, South to West at upper elevations. With such limited data at this time, add some insurance and be on the lookout for wind slabs on all aspects at upper elevations and more sporadically at mid elevations. Any stiff, cohesive snow on the surface  (wind slab) will easily be triggered. The size of wind slabs is hard to estimate, but expect the potential size to be D1-D2, large enough in some cases to bury, injure or kill. Any avalanche that runs into terrain traps will compound the hazard. Wind slabs are not expected to reactivate HZAC weak layers deeper in the snowpack at this point.

Again, it’s early season and we have limited data. That means we have a moderate to low confidence in our assessment of the hazards. If you get out and about, please share your observations here, which assist in building a better, more accurate avalanche advisory.

Expect the first Avalanche Advisory on November 18.

Wind transport on Government Peak 11/7/2017

















UPDATE 10/31:

We are not issuing advisories at this time, however we are making a suggested avalanche danger rating for your use, as a baseline for your own snowpack and avalanche assessment.

A considerable avalanche hazard exists with the potential for the hazard to rise to high avalanche danger. The snowpack is currently in a tenuous balance.

Any combination of more precipitation, wind, warm ambient temperatures, and/or heating due to sunlight, or simply a human being weighing a slope may tip the balance. The danger may increase with diurnal heating.

Natural wet slab avalanches observed at HP today. Large enough to easily bury a person.  This wet slab was estimated to be 200′ wide X 1000′ long.

Swimming Tim’s, Microdot WS-N-D2-0





















Temperatures have recently been hovering at or just below the freezing level at 4500′. An inch of precipitated water was reported at Independence Mine yesterday, with a rain line observed at about 4000′.

Water percolating through the snowpack has triggered a cycle of natural wet slab and wet loose avalanches. Until the temperatures cool and the snowpack re-freezes, wet avalanche activity will continue. NOAA has indicated that temperatures could spike to 45ºF this week under high pressure. Pay close attention to the temperature over the next several days. A lack of overnight freezing temperatures is currently a big red flag.

We need a significant freeze overnight to “lock up” the snowpack and increase stability. Be especially cautious around South to West aspects in the afternoon (spring-time, diurnal mind set). These slopes will be more susceptible to avalanches due to their combined exposure to sunlight (heat) and warm ambient temperatures.

On colder aspects, such as North facing slopes, expect the weak basal layer and buried rain crust to continue to be an avalanche problem, however, this will slowly be stabilizing over time.

Be in the assessment mind set, slowly build observational data and snowpack testing on test slopes with minimal exposure to determine if your chosen slopes are safe. Recognize that the current conditions are tricky to assess and uncertainty and confidence in your assessment may be low. Hedge these types of bets by using terrain to keep you safe. Avoid avalanche terrain and stay clear of the runnout of slopes 30º and steeper.


UPDATE 10/29:

More snow today will increase the avalanche hazard. Many factors in the snowpack and weather are stacking up to produce avalanches.

Today the hazard is at least considerable and could increase to high.

Early season, weak basal snow, combined with a rain crust, provide a perfect weak layer/bed surface for avalanches. Winds last week transported snow into stiff slabs, and warm temperatures have allowed recent snow to consolidate into storm slabs. Both of these slab types will be reactive on the weak, basal snow and rain crust. Snowpit instability test results can easily be misleading. The snowpack has spatial variability that will make any single snowpit unreliable.

Travel advice: Avoid avalanche terrain. If you choose to enter avalanche terrain: Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route-finding, and conservative decision-making are essential.

UPDATE 10/28:

A significant human triggered avalanche up to D2 and a near miss (see observations) was reported today. This observation has some important educational nuggets. These folks did everything right up until their last decision on their exit route for the day.

All were avalanche level one certified. All tested their beacons before heading out for the day. All dug a snowpit that showed stable results (on a representative slope). All used travel protocol through the day, riding one at a time and spacing out when traveling and riding. The avalanche occurred at the end of the day as they were traversing a steep slope (37 degrees) above a terrain trap to exit the backcountry. One of the people involved informed us that they had rode a little too far down the mountain than intended, which changed their exit route plan. They then dropped their guard, and all crossed the avalanche slope at the same time, which could have resulted in one or all of them buried. One person was buried to their waist and lost a ski. All were uninjured.

No matter what your training or preparedness, this story highlights the importance of making good decisions every time. That’s a tall order for anyone. Slow down, don’t drop your guard and use your team to review your plan and change it as necessary. Conservative decisions and travel routes are very important under the current avalanche conditions and could save yours and others lives.

Widespread shooting cracks and whumphing, all red flags that mean human triggered avalanches are possible, have been reported over the last several days. Please review all the recent avalanche observations here.

While HPAC has not begun avalanche advisories for this season, we are studying observations, observing the snowpack, and posting information as it comes in. Check back here for more information periodically, and follow us on Facebook. Regular avalanche advisories will begin mid-november.



Older post from October 26:

Snow has arrived early at Hatcher Pass.  Many folks have been and will be jumping at the opportunity to play in the snow.

If you are seeing social media posts highlighting winter recreation at Hatcher Pass, take them with a large grain of salt. The snowpack is thin, hero shots are one or two ski turns long, followed by thin coverage, rocks and exposed hazards. Of course you can get out there and have a great day, but a thicker, safer snowpack is several snow storms away.

Early season conditions often catch people by surprise, as triggering avalanches is possible. Be prepared, treat the snowpack with respect. Use avalanche and snowpack assessment techniques, use safe travel protocol, employ conservative decision-making, and dial in your rescue practice and techniques.

The early snow that arrived at Hatcher Pass has rotted out and become a weak base. Rain up to 4,000′ has left a crust layer near the base of the snowpack. Winds transported snow into stiff wind slabs sitting over the weaker basal snow which have recently been reactive. Shooting cracks and whumphing are bulls-eye clues that human triggered avalanches are possible. On top of it all, we just received 6″ of new snow on the evening of the 24th that came in cold and warmed up, creating an upside down cake that could increase the chances of triggering storm slabs/persistent slabs.

Overall, there is actually quite a bit going on in the snowpack. Your understanding of the avalanche problem likely contains a fair amount of uncertainty. This means, SLOW DOWN, and carefully assess. You’ve got the time and resources to assess the snowpack, use your friends to double check your human factor and decision making, and hopefully you already practiced your rescue skills this season.

A good article on early season snow: http://avalanche.state.co.us/early-season-snow/

HPAC avalanche advisories are scheduled to begin mid-November.

A huge thank you to all the people who have been getting out there are reporting their observations through the HPAC observation platform and through facebook social media. Your observations are an integral cog in the wheel of avalanche safety.

Coming up…

November 4

HAX and HPAC present:





















Posted in HPAC Forecasts.
Jed Workman

Forecaster: Jed Workman