Haines Avalanche Center

Forecast Expired - 12/12/2021

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

Avalanche Problems

Problem 1

Wind Slab:

Aspect: Most likely on wind loaded aspects and features SW-S-SE-E.

Elevation: Mainly at and above treeline.

 

Strong NW winds are expected today. You are likely to encounter fresh wind slabs and active wind loading in the alpine. Plenty of previous snowfall is primed for readily available transport. Additionally, while it has been a few days since recent snowfalls, there are unbonded weak layers between older wind slabs in the upper meter of the snowpack.

 

Identify wind-drifted snow by looking for stiff or hollow surface snow, and looking for cracking, whumphing and blowing snow – treat these areas as highly suspect. You can find safer conditions in wind-protected areas with softer snow. 

 

Natural avalanches are possible and human triggered avalanches are likely at and above tree-line.  Cautious route-finding and conservative decision-making is essential.

 

Beware of  terrain traps (e.g. gully, rocks, dense timber, cliff, crevasse) or areas where snow could pile up quickly. Avoid traveling above or below terrain traps.

 

 

 

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.

Elevation: All Elevations.

 

Incoming cold weather will only serve to weaken buried layers. The persistent slab danger is not healing, it is just standing by waiting for the right trigger. Don’t be the trigger!

 

Observations from Old Faithful last Sunday found a thin crust with weak snow down 60-70cm near 3,200′ and below. This bathtub ring effect, from lower-elevations to mid-elevation, where freezing levels are more likely to cause crusts and weak layers – should be carefully evaluated. Also, of note was surface hoar formation 12/8-12/9 that could be buried by the incoming snowfall and overloaded by wind slab.

 

It could still be possible that any surface avalanches could step down to the deeper weak layers, rain crust, or even the ground in alpine areas. 

 

  • One of the best ways to reduce your exposure to deeper 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.
  • Manage the terrain by only exposing one person at a time to the hazard, use group up spots out of harms way, and carry radios for communication.
  • Look and listen for whumping, and other signs of instability. 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

Avalanche Activity

Reports from the last week: A large natural avalanche was reported on a west aspect near 3920 in the Lutak Zone (See Persistent Slab problem). We also had reports of natural avalanches above Chilkoot Lake. These slides were likely dated Dec. 1 when temperatures increased with strong winds from the South.

Weather

Winds will switch Northerly and temps will drop.

  • Yesterday, moderate temps in the morning made way for the winds to switch northerly and a temperatures to begin to plummet. Expect to see single digits for the next couple days.
  • A low pressure system introduced 6-8″ of precipitation, moderate southeast winds gusting strong and warming temperatures, especially near sea-level.
  • We’ve had about 20″ of low-density new snow this week in the Lutak zone, and around 8″ in the Transitional zone.
  • Nov. 28 – Dec. 4th, 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″  0″ / 0.0*  10″ / 0.6*  0′  Strong, NW  0″ / 0.00*
Flower Mountain @ treeline  49″ *  0″ / 0.00  9″ / 0.70  0′  Strong, NW  0″ / 0.0*
Chilkat Pass @ 3,100ft  29″  0″ / 0.00  2″ / 0.10  0′  Strong, NW  0″ / 0.00*

( *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. Be prepared for an emergency and hypothermia. Winter is a high consequence environment. Carry bear spray.


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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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