Turnagain Pass RSS

Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, January 4th, 2023 - 7:00AM
Expires
Thu, January 5th, 2023 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 1,000′ due to a short period of heavy snowfall and strong winds occurring this morning. Wind slab avalanches, up to 2′ deep, will be likely to trigger on any slope with recent wind loading and natural wind slabs are possible. Shallow soft slab avalanches could be triggered on slopes out of the wind seeing over 8″ of new snow from overnight. A cautious mindset is recommend if traveling into the backcountry.

The danger is MODERATE below 1,000′ where small wet snow avalanches could occur or debris from a slide above could run.

SUMMIT LAKE / SEWARD / LOST LAKE:  Increased avalanche conditions could exit in these areas due to strong winds and a short burst of intense precipitation this morning. Extra caution is advised.

Special Announcements

AK DOT & PF:  There will be intermittent traffic delays for avalanche hazard reduction today on the Portage Glacier Highway near Mile Post 5 and Bear Valley from 10:00 am to 12:00 noon. Motorists should expect delays of 45 minutes. Updates will be posted on the 511 system.

Wed, January 4th, 2023
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
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. Dangerous avalanche conditions. 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

A remotely triggered avalanche was reported in Girdwood Valley in the Notch Mtn area around 2,500′ on a SW aspect. The avalanche was witnessed by another group in the area. It was ~3′ deep and unknown how wide or far it ran due the view being obscured.

Otherwise, that last known avalanche was a natural avalanche cycle that occurred during heavy snowfall and strong winds early on New Year’s and morning.

Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

The active weather continues. Starting around midnight, snowfall intensity picked up (above 1,000′, rain below) and winds have really picked up. As of 6am 8-12″ of new snow has fallen at Turnagain Pass, 4-8″ in Girdwood Valley, and 3-4″ at Summit Lake. Easterly ridgetop winds have been 30-40mph with gusts as high as 74mph on Max’s Mtn. Both precipitation intensity and winds should be on the decline through the day. However, avalanches will still be prime for people to trigger in the new storm snow. Remember, watching for any recent avalanche activity will be a good place to start when evaluating our Red Flags (recent avalanches, cracking or collapsing in the snow, heavy snowfall and strong winds).

Wind slab avalanches are likely to be found and triggered on slopes that have seen, or are still seeing, active wind loading. Depending on how good the visibility is today, it could be hard to see these signs of wind loading. Be sure to always feel for stiffer snow over softer snow and any cracks that shoot out from you.

Along ridgelines, cornices could be teetering on the brink of failure. They have grown significantly since the holiday storms and could look much different. This is something to watch for as the skies clear and it’s much easier to travel along ridges.

Shallow soft slab avalanches, composed of the new snow, could be an issue anywhere over 8″ of snow falls. Stick your hand in the snow now and then to see how much new snow has fallen. If you are in area that got over 8″ of snow overnight, that new snow may not have bonded yet to the old surface and could slide easily.

 

Moderate winds along the lower Sunburst Ridge were taking minutes to fill tracks back in. Stronger winds were noted at the higher elevations. 1.3.23.

Click here to view the video below if it doesn’t load in your browser.

Avalanche Problem 2
  • Persistent Slabs
    Persistent Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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

Buried under this morning’s storm snow, the New Year’s snow, and the Xmas snow, are various layers of weaker faceted snow. These are the December facets that formed mid-December, and the facets surrounding the Thanksgiving crust. They are anywhere from 3-5′ deep. Could one of these layers be responsible for the Notch Mtn avalanche? Possibly. We’ll try and find out. For now, we all need to be aware there could be larger avalanches under just the storm snow issues. Another reason to be extra cautious.

As more snow falls, these layers are getting deeper and deeper and are also become more compressed. These two things really help them adjust and heal. It also begins the transition into a Deep Persistent Slab problem in the event they are not completely healed – something we are currently evaluating.

 

Snowpit tests at this site produced no signs of reactive buried weak layers. However, this area sees a lot of traffic. As skies clear and travel to other areas becomes easier, weak layers could turn out to be more reactive. 1.3.23.

Weather
Wed, January 4th, 2023

Yesterday:  Light snow showers and mostly overcast to obscured skies were over the region yesterday. Only a trace to an inch of new snow was reported. Ridgetop winds were easterly in the 15-25mph range with gusts near 40mph. Temperatures were mild, in the upper 30’sF at sea level and in the high 20’sF along ridgelines.

Today:  A pulse of moisture is over the region this morning bringing snowfall above 1,000′ and rain below. There has been around 10″ of new snow at Turnagain with lesser amounts in Girdwood Valley and Summit Lake. Another 3-5″ is expected through the day. Ridgetop winds are currently 20-40mph with gusts in the 70’s. Winds and precip should slow through the day as temperatures cool (bringing the snow line down to ~500′).

Tomorrow:  A break in stormy weather is expected to begin tomorrow with some clearing skies and extend into Friday; and possible into the weekend. Ridgetop winds should also take a break and look to be light from an easterly direction. Temperatures will be on a cooling trend, into the teens and 20’sF.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 31 8-10 1 64-66
Summit Lake (1400′) 31 4 0.4 34
Alyeska Mid (1700′) 32 3 0.3 46
Bear Valley – Portage (132′) 36 rain 0.75

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 22 NE 25 44
Seattle Ridge (2400′) 26 N/A* N/A* N/A*

*Seattle Ridge anemometer is rimed up and not reporting.

Observations
Recent Observations for Turnagain Pass
Date Region Location
11/16/23 Turnagain Observation: Tincan Common
11/14/23 Turnagain Observation: Sunburst/Magnum
11/14/23 Turnagain Observation: Seattle Ridge
11/13/23 Turnagain Avalanche: Tincan Trees
11/12/23 Turnagain Observation: Sunburst
11/12/23 Turnagain Avalanche: Goldpan – avalanche
11/11/23 Turnagain Observation: Tincan Common
11/11/23 Turnagain Observation: Taylor Pass – Sunburst
11/10/23 Turnagain Observation: Tincan
11/10/23 Turnagain Observation: Tincan Trees
Riding Areas

The riding areas page has moved. Please click here & update your bookmarks.

Subscribe to Turnagain Pass
Avalanche Forecast by Email

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.