Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, January 12th, 2023 - 7:00AM
Expires
Fri, January 13th, 2023 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger is MODERATE above 1000′ today. It is still possible for people to trigger a very large avalanche 3-6’+ deep on a buried weak layer. There have been several near misses on this layer in the past week and unfortunately this type of weak layer takes a long time to go away. We recommend conservative terrain selection and emphasize the potential to remote trigger avalanches above, to the sides, or below where you are travelling. It is also likely for people to trigger small avalanches 6-12″ deep in the recent storm snow. Below 1000′ the avalanche danger is LOW. 

Special Announcements

Alaska Avalanche School has several slots open in their upcoming Motorized Avalanche Rescue course in Turnagain Pass on January 15th. This is a great affordable opportunity to invest in your own skills and knowledge to help keep yourself and your partners safe in avalanche terrain!

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.

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Thu, January 12th, 2023
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
Low (1)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Moderate (2)
Treeline
1,000'-2,500'
Avalanche risk
Moderate (2)
Below Treeline
Below 1,000'
Avalanche risk
Low (1)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Recent Avalanches

We got some reports of shallow but sensitive storm and wind slabs yesterday. Despite only 6″ of new snow on Tuesday night into Wednesday, it fell on top of a layer of surface hoar and surface facets which is causing reactive conditions especially in wind loaded areas. A group on Tincan yesterday was able to trigger a few pockets of this storm snow. Prior to those shallow slabs the last know avalanches were two very large skier triggered avalanches on the SW and N face of Cornbiscuit on Saturday Jan 7th. See the Near Miss Report HERE.

Shallow storm slab releasing on top of buried surface hoar and surface facets on Tincan. Photo from Anonymous 1.11.23

Avalanche Problem 1
  • Deep Persistent Slabs
    Deep Persistent Slabs
  • Aspect/Elevation
  • Almost 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

We are still in a holding pattern waiting for a layer of facets above the Thanksgiving melt freeze crust to slowly gain strength and be buried deeper by future storms. This is a tricky avalanche problem because it requires patience to allow the snowpack to slowly heal itself. With that layer currently buried 3-6′ deep it is very hard to test using standard stability tests in snowpits. Unfortunately this is the type of weak layer setup that can last for weeks to months, but since it is already buried quite deeply hopefully a few more good storms will put that layer to rest until the spring.

We have seen ample evidence of very large natural and human triggered avalanches on this weak layer in the past week in Turnagain Pass and surrounding areas. Some of these avalanches had extraordinary propagation, which means avalanches can be very wide and connected across multiple terrain features. For now we are continuing to recommend sticking to smaller terrain features, low angle slopes, and being very aware of the potential for remote triggering a slope above, to the sides, or below where you are travelling. This layer is most concerning above 2500′. In the meantime, there is good skiing and riding to be found at lower elevations.

Avalanche Problem 2
  • Wind Slabs
    Wind Slabs
  • Aspect/Elevation
  • Almost 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

Tuesday night we received about 6″ of new snow that has been quite reactive to human triggering (see recent avalanches). These storm slabs and wind slabs are only about 6-12″ deep right now but could stay sensitive to human triggering for longer than normal since they are sitting on top of surface hoar and near surface facets. With wind speeds gusting up to 30 mph at ridge tops over the past 24 hours human triggered avalanches are still likely for these shallow surface instabilities today. To identify areas with reactive surface slabs keep an eye out for shooting cracks on steeper terrain features and use small test slops to check how well the new snow is bonding to the old snow surface.

Weather
Thu, January 12th, 2023

Yesterday: Snowfall stopped Wednesday morning with around 4-6″ falling overnight above 500′. Light to moderate wind speed at upper elevations with averages of 0-10 mph and gusts up to 30 mph. Temperatures in the low thirties at sea level and mid twenties at upper elevations. Skies cleared throughout the day, ending mostly sunny with some lingering clouds in valley bottoms.

Today: Light precipitation near coastal areas with snow line around 500-900′ today. Up to 1-2″ of snowfall possible near Portage. Wind speeds averaging 5-10 mph with gusts up to 25 mph trending towards decreasing wind speed throughout the day. Temperatures should remain in the mid thirties at sea level and twenties at upper elevations. Low and mid level cloud cover is expected in the forecast area today with a trend toward clearing in the evening.

Tomorrow: Friday looks very similar to Thursday except with lighter winds. No significant new snowfall expected until Saturday at the earliest.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 29 0 0 60
Summit Lake (1400′) 19 0 0 33
Alyeska Mid (1700′) 30 0 0 55
Bear Valley – Portage (132′) 34 0 0.1

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 12 ENE 8 22
Seattle Ridge (2400′) 25.5

* Seattle Ridge weather station is not reporting wind speed since 700 pm on Jan 10th

Observations
Recent Observations for Turnagain Pass
Date Region Location
01/29/23 Turnagain Observation: Tincan Backdoor
01/28/23 Turnagain Observation: Sunburst
01/28/23 Turnagain Avalanche: Seattle Ridge
01/28/23 Turnagain Observation: Tincan Common
01/27/23 Turnagain Observation: Sunburst
01/27/23 Turnagain Avalanche: Lynx Creek
01/25/23 Turnagain Observation: Cornbiscuit
01/22/23 Turnagain Avalanche: Tincan
01/21/23 Turnagain Avalanche: Seattle Ridge
01/21/23 Turnagain Avalanche: Lynx drainage – avalanche
Riding Areas
Updated Fri, January 06th, 2023

Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: mailroom_r10_chugach@fs.fed.us

Area Status Weather & Riding Conditions
Glacier District
Johnson Pass
Open
Opened Dec 13th.
Placer River
Closed
Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Skookum Drainage
Closed
Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Turnagain Pass
Open
Opened Dec 13th.
Twentymile
Closed
Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Seward District
Carter Lake
Open
Opened Dec 13th.
Lost Lake Trail
Open
Opened Dec 13th.
Primrose Trail
Open
Opened Dec 13th.
Resurrection Pass Trail
Closed
Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor
Open
Opened Dec 13th.
South Fork Snow River Corridor
Open
Opened Dec 13th.
Summit Lake
Open
Opened Dec 13th.

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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.