Turnagain Pass RSS

Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, March 9th, 2022 - 7:00AM
Expires
Thu, March 10th, 2022 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger is MODERATE above 1000′. Up to 3″ of snowfall and moderate winds today will create fresh wind slabs up to 2′ deep which are most likely to be found at upper elevations. Active weather will make natural avalanches possible in the afternoon and the avalanche danger will trend towards CONSIDERABLE in the alpine. In addition, persistent weak layers exist in the upper snowpack across the forecast area which could create wider propagating avalanches with the potential for remote triggering (being triggered from above, below, or to the sides of steeper terrain). The avalanche danger is LOW below 1000′.

Wed, March 9th, 2022
Alpine
Above 2,500'
2 - Moderate
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.
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • 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.
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

After a few days of sunny skies we are heading back into a stormy weather pattern. A weak low pressure system is forecast to produce 4-8″ of snowfall over the next two days in coastal areas (Girdwood, Portage, Placer) and closer to 1-3″ of new snow in Turnagain Pass. Winds are also expected to increase into the 15-25 mph range out of the southeast and redistribute the surface snow into fresh wind slabs. The primary avalanche problem today will be wind slabs up to 2′ deep which will be most likely at upper elevations along ridgelines, cross loaded gullies, and convex roll overs. The 1-3″ of new snow expected today will add some loose snow at the surface for the winds to redistribute.

The visibility could make it challenging to travel in areas seeing the most wind loading today, but keep an eye out for active wind transport, shooting cracks, and hollow feeling snow to locate fresh wind slabs if you get into alpine terrain. An added complication is that we have a variety of persistent weak layers in the upper snowpack that could become more active from the new snow and wind loading (check out problem 2 for more details). We recommend evaluating the terrain and snowpack carefully and being aware of the potential for avalanches to be remote triggered if you are in an area harboring persistent weak layers.

Winds expected to be stronger along the coast and Turnagain Arm today. Photo 3.9.22

Avalanche Problem 2
  • Persistent Slabs
    Persistent Slabs
  • 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.
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 upper snowpack is harboring a variety of different persistent weak layers which were created about a week ago before the last significant snowfall. The most prominent are buried surface hoar and near surface facets which have both been found about 1′ deep in the snowpack in a variety of locations throughout the forecast area. The distribution of these weak layers is variable and the only way to know if they exist where you are travelling is by digging into the snowpack. Luckily they are not buried very deeply right now so this is a pretty easy task, but as the new snow starts to pile up on top of them it will get harder to locate the weak layers and the potential size of avalanches they could produce will increase.

There have been several observations of avalanches that were remote triggered or the person who triggered them was not the first on the slope (examples in Lynx Creek, Eddies, Seattle Ridge). These are classic signs of persistent weak layers and should be a warning sign moving forward. These weak layers might become more capable of producing avalanches with a new snow load or simply by wind creating a firmer slab on top.

Buried surface hoar underneath a soft slab on Tincan, this could become a larger issue once the slab is more cohesive (see ob here). Photo Kit Barton 3.7.22

 

Weather
Wed, March 9th, 2022

Yesterday: Mostly cloudy with temps in the mid to upper 30s at lower elevations and mid 20s at ridgetops. Winds were consistently in the 10-20 mph range with gusts between 20-30 mph. No significant new snow accumulation.

Today: Another storm system is moving into the area today with new snowfall totals of 1-3″ expected during the day. Snow totals should be on the higher end of that range in Girdwood, Portage, and Placer, with Turnagain Pass on the lower end. Snow line should be down to sea level today. Winds are forecast in the 15-25 mph range at upper elevations.

Tomorrow: More snowfall is expected overnight tonight and tomorrow, with storm totals from now to Thursday night between 1-3″ for Turnagain Pass and 4-8″ for Girdwood, Portage, and Placer. Snow line is expected to creep up to about 500′ tomorrow as the temperatures increase. Winds will increase slightly overnight, ranging from 20-30 mph at upper elevations.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 34 1 0.1 94
Summit Lake (1400′) 32 0 0 40
Alyeska Mid (1700′) 32 1 0.1 NA

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 20 ENE 15 37
Seattle Ridge (2400′) 26 SE 13 25
Observations
Recent Observations for Turnagain Pass
Date Region Location Observer
10/27/24 Turnagain Observation: Tincan Michael Kerst
10/21/24 Turnagain Observation: Turnagain Pass Road Observation Trevor Clayton
10/19/24 Turnagain Observation: Tincan – Below Todds Run Andy Moderow
10/18/24 Turnagain Observation: Taylor Pass Eli Neuffer
10/15/24 Turnagain Observation: Tincan Common John Sykes Forecaster
10/14/24 Turnagain Avalanche: Tincan CNFAC Staff
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
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.
Become a Member
If you think a public avalanche center is important please support our organization.
Donate Now
Become a Sponsor
Supporting the CNFAIC proudly shows that your business or organization values the safety of our snow sports community.
Become a Sponsor