Haines Avalanche Center

Forecast Expired - 12/09/2021

Above 2,500ftConsiderable

1,500 to 2,500ftModerate

Below 1,500ftModerate

The Avy Rose shows the forecasted danger by elevation and aspect.

It adds more detail about where you are likely to find the dangers mentioned in the forecast. The inner circle shows upper elevations (mountain top), the second circle is middle elevations, and the outer circle represents lower elevations.

Think of the Rose as a birds-eye view of a mountain, looking down from above. The rose allows our forecasters to visually show you which parts of the mountain they are most concerned about.

WNWNNEESESSW

Degrees of Avalanche Danger

Low
Moderate
Considerable
High
Extreme

Avalanche Problems

Problem 1

Storm Snow:

This zone received about 8″ of new snow this week, and about 6″ last week. South winds were blowing in the alpine during last week’s storms, which caused significant wind loading on W-NW-N-NE-E aspects. This week’s snow fell in light winds, but will add additional load to previous weak layers. You may find loose-snow (fast, large sluff) dangers in steeper terrain, and soft slab dangers in more wind-affected areas.

 

There is also significant Step Down potential right now. Any surface avalanches could easily step down to deeper weak layers that then trigger a wide, deadly avalanche. See the Persistent Slab problem below.

Likelihood:

  • Almost Certain
  • Very Likely
  • Likely
  • Possible
  • Unlikely

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Problem 2

Persistent Slab:

Aspect: All aspects and below terrain features

Elevation: Mainly Treeline and above

 

Observations from Ripinsky yesterday found collapsing and cracking on old wind slabs in the midpack. These slabs were failing on softer layers (facets) 1-3ft deep, that formed over the last two weeks. Snowpit results found clean, active shears 1 meter deep, which means potential for propagation and a lack of friction on the layer.

 

As if that isn’t enough to give you pause, we have also found significant weak facets at the bottom of the alpine snowpack in both zones, and the lingering October Rain Crust with weak layers above and below it. It is possible that any surface avalanches could step down to the deeper rain crust, or even the ground in alpine areas. 

 

  • One of the best ways to reduce your exposure to deep persistent weak layers would be to stick to areas of deeper snowpack (>1m deep). But be wary of hidden rocks that can act as trigger points, and thin areas around the margins of a slab.
  • Look and listen for deep whumping! Report any natural avalanche activity on these deeper layers!

 

Likelihood:

  • Almost Certain
  • Very Likely
  • Likely
  • Possible
  • Unlikely

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Weather

We’ve had about 20″ of low-density new snow this week in the Lutak zone, and around 8″ in the Transitional zone.

Last week, it snowed 6-14″. Winds switched from SE to NW and increased into typical northerly outflow as temperature plummeted into the single digits.

October brought heavy snow in the alpine, followed by a few rain/sun crusts, followed by regular heavy snowfalls in November.

 Snow Depth [in] Last 24-hr Snow/SWE [in] Last 3-days Snow/SWE [in]  Today’s Freezing Level [ft]  Today’s Winds Next 24-hr Snow/SWE
Mount Ripinsky @ treeline **   67″  8″ / 0.50*  18″ / 1.15*  0′  Light, NW  7″ / 0.40*
Flower Mountain @ treeline  50″ *  2″ / 0.10  8″ / 0.30  0′  Light, NW  5″ / 0.30*
Chilkat Pass @ 3,100ft  29″  0″ / 0.00  3″ / 0.15  0′  Light, NW  3″ / 0.20*

( *star means meteorological estimate )

** The Ripinsky weather station is in need of repair, and will likely be down until Summer.

Additional Information

Beware of deep treewells which can trap a person. It’s deep out there. Temperatures and wind chill are cold. Be prepared to prevent hypothermia.

Become a sustaining Haines Avalanche Center Member by clicking the poster or visiting dev.alaskasnow.org/joinHAC. Support local forecasts, observations, education and weather stations. Join a community of winter recreationalists. Benefit from collective knowledge and skills. Help keep your friends and family safe in the backcountry. Get a free limited edition mountain buff, or neck gaiter with a $50 membership (first 20 members!).

 

Practice like you play. Make sure all your rescue gear is fully functional and your beacon has NEW batteries. Make sure 1) everyone in the group has a functioning beacon, shovel and probe 2) knows how to use them and 3) has trained in companion rescue in the last year. Keep your skills fresh. If you head into the hills, watch out for red flag avalanche conditions, natural avalanches, whoomphing or collapsing, and shooting cracks.

 

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