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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, January 15th, 2023 - 7:00AM
Expires
Mon, January 16th, 2023 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 2,500′ due to continued ridgetop winds. Wind slab avalanches 1-2′ deep are likely to be triggered by people on slopes with recent wind loading. Slabs could be sitting on buried surface hoar, making them larger and easier to trigger. It is also still possible to trigger a very large slab breaking in weak layers near the base of the snowpack. The danger is MODERATE between 1,000′ and 2,500′ where smaller wind slabs could be found in exposed areas. The danger is LOW below 1,000′.

*Tomorrow, Monday MLK Jr Day, avalanche danger could increase due to heavy snowfall forecast with stronger winds. 

SEWARD / LOST LAKE: This area is expected to be favored for higher snowfall totals over the next 48 hours. Avalanche danger will increase with active snowfall and wind loading.

SUMMIT LAKE: A very weak snowpack exists in this area and strong winds and snowfall will increase avalanche danger. Several buried weak layers could produce large avalanches during stormy weather (see 1.13.23 Tenderfoot observation).

Special Announcements

Forecaster Chat #2:  Join us at the Girdwood Brewing Co. from 5:30-7:00 p.m. on Thursday, Jan. 19! CNFAIC forecaster Andrew Schauer will open the night with an overview of the state of the snowpack, followed by a discussion on how safe terrain management changes depending on the type of avalanche problem at hand. More details here.

Sun, January 15th, 2023
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
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.
Recent Avalanches

No new avalanches were reported yesterday. The last known avalanches were shallow storm and wind slabs (4-8″ deep) on Thursday. The last deep slab avalanches were on Cornbsicuit a week ago (1/7/23).

Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Aspect/Elevation of the Avalanche Problem
Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.
Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.
Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

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
More info at Avalanche.org

Blustery weather continues today at the higher elevations. Although only a trace to a couple inches of snow fell yesterday (similar amounts expected today) the winds have been blowing along the ridges. Over the past 12 hours the easterly winds have averaged 15-20mph with gusts near 40. By this afternoon we should see a bump to 20-25mph with gusts closer to 50mph.

With plenty of loose snow on the surface a day ago, we can expect wind slabs to continue building in the higher elevations above treeline. Adding to the equation is a layer of surface hoar and near surface facets that was buried by Tuesday night’s 4-6″ of snow. This layer could be sitting under some, or many, of these new wind slabs. In this case, wind slabs could be fairly easy to trigger and could pull out larger than we might think. Watch for active wind loading, stiffer snow over softer snow, and cracks that shoot out from you. All these are the classic wind slab signs. It’s also good to remember a wind slab could trigger a much larger slab, discussed in Problem 2 below.

In areas out of the wind, it may still be possible to trigger a shallow soft slab. This would be the 4-6″ of snow sitting on buried surface hoar and small facets that may not yet be bonded. This would be a small avalanche but still something to keep in mind.

 

Buried surface hoar can be seen on its side near the glove. This was found under a 6″ slab from a quick hand shear test at 2,400′ on Pete’s North yesterday. Thank you to Kakiko Ramos-Leon for the photo. 1.14.23.

Avalanche Problem 2
  • Deep Persistent Slabs
    Deep Persistent Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
Aspect/Elevation of the Avalanche Problem
Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.
Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.
Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

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
More info at Avalanche.org

As you likely are aware, near the bottom of the snowpack is a crust from Thanksgiving with weak faceted snow around it. This combo produced a bunch of avalanches a week to 10 days ago from people riding or skiing along ridgelines or near slopes in the heart of Turnagain Pass. This layer will be with us for some time and people still could trigger it, creating a very big and deadly avalanche. We cannot use stability tests anymore, they are unreliable, and no signs of instability are likely to warn us until the whole slope releases. Slopes can be triggered after many people have been on them and it’s really easy to think ‘aw this snowpack seems fine’ when it may not be. Thin areas near rocks and ridgelines are likely trigger spots. The only way to avoid the problem is to stick to slopes 30 degrees or less with nothing steeper above us.

We went out to the crowns of several of these avalanches on Friday to get a better look at the snowpack along Seattle Ridge. We found no surprises, just more proof that the crust and facets exist over terrain features and ridgelines, making these avalanche triggerable from what can seem is just a shallow rocky ridge.

Five remotely triggered slabs on the SE face of Seattle Ridge from January 5th. On January 13th we got back up there and dug a pit to confirm the snowpack structure and weak layer.

 


Snowpit just off the ridge in a representative spot from the avalanches that occurred January 5th. 

Weather
Sun, January 15th, 2023

Yesterday:  Cloudy skies and light snowfall was over the region. Only a couple inches look to have fallen in areas close to Turnagain Arm with only a trace toward the interior mountains. Ridgetop winds were strong, averaging 15-25mph with gusts in the 40’s from an easterly direction. Temperatures were warm, in the mid 30’sF at the lower elevations and the mid 20’sF along the ridgetops.

Today:  Cloudy skies will again be over the region as a storm system slowly moves in. Only a couple inches of snow, at best, is forecast to fall above 1,000′ today (rain below). Another few inches is expected overnight. Ridgetop winds should continue to blow in the 15-25mph range with stronger gusts from the east. Temperatures will remain warm, mid 30’sF at the lower elevations and mid 20’sF in the higher elevations.

Tomorrow:  This storm is looking to peak Monday afternoon, tomorrow, into Tuesday morning. Snowfall amounts for Monday are 8-12″ for Girdwood and Turnagain Pass with a rain line lowering to around 300′ as temperatures cool during the storm. Another several inches should also fall Tuesday. Ridgetop winds will strengthen as well from the east, 25-35mph with gusts in the 60’s or so.

PRECIPITATION 24-hour data (6am – 6am)

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 33 trace trace –
Summit Lake (1400′) 30 0 0 32
Alyeska Mid (1700′) 31 2 0.1 51
Bear Valley – Portage (132′) 32 1 0.4 –

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 25 NE 15 43
Seattle Ridge (2400′) 27 SE 14 24
Observations
Recent Observations for Turnagain Pass
Date Region Location Observer
05/13/24 Turnagain Observation: Eddie’s, Sunburst, Seattle, Cornbiscuit, Pete’s South H Thamm
05/13/24 Turnagain Observation: Turnagain Pass non-motorized side Amy Holman
05/12/24 Turnagain Observation: Warm up Bowl Tony Naciuk
05/07/24 Turnagain Observation: Turnagain Pass Wet Slabs A S
04/29/24 Turnagain Avalanche: Turnagain aerial obs Tully Hamer
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04/23/24 Turnagain Observation: Turnagain Sunny Side Travis SMITH
04/21/24 Turnagain Observation: Bertha Creek Anonymous
04/20/24 Turnagain Avalanche: Spokane Creek Schauer/ Mailly Forecaster
04/16/24 Turnagain Observation: Cornbiscuit Krueger / Matthys Forecaster
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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.
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