Turnagain Pass RSS

Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, April 16th, 2023 - 7:00AM
Expires
Mon, April 17th, 2023 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

A MODERATE avalanche danger exists at all elevations today and into tomorrow. Loose wet avalanches releasing naturally as the sun melts surface crusts will be likely. These are often small but can become larger on big steep slopes or if they trigger a slab, creating more debris. For those hunting dry snow in high elevation shady aspects, watch for fresh wind slabs from a bump in winds overnight and lingering slabs up to a foot deep. Even a small wind slab can have big consequences in steep rocky terrain.

SEWARD: A layer of buried surface hoar 1-2′ deep has been reported. Large avalanches releasing on low angle slopes may still be possible so extra caution is recommended.

PORTAGE VALLEY hikers/bikers/xc skiers: Be aware of avalanches occurring overhead as the day heats up. This area can see large wet slides that can run close to commonly traveled areas.

*MONDAY AVALANCHE OUTLOOK:  There will be no forecast issued tomorrow, Monday, April 17. The next forecast will be Tuesday, April 18. Avalanche conditions are expected to be similar (MODERATE). Slightly cooler temperatures may not melt surface crusts enough to cause many wet sluffs on Monday.

Special Announcements

Hatcher Pass:  If you have not been following HPAC’s forecasts and observations, there has been a lot of avalanche activity with a large skier triggered avalanche yesterday.

Avalanche Center End of Season Operations:  Beginning today we will forecast 4 days/week (Tuesday, Thursday, Saturday, Sunday). The final forecast is scheduled for April 30th.

Sun, April 16th, 2023
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
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. 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

There was one significant avalanche we know of yesterday, a dry slab triggered by a skier on a high elevation northerly face in Lynx Creek. Additionally, there were several small to large natural wet loose slides on all aspects facing the sun (including northeast and northwest). Some of these wet sluffs triggered shallow damp slabs with one slab triggered by a snowmachiner near Whittier.

Lynx Creek, skier caught/carried:  Yesterday a skier triggered a dry slab avalanche on the upper face of Captain’s Chair in Lynx Creek. Skier was reported to have triggered the slab on their second turn and was caught and carried around 2,000′ down the face and over a large cliff band near the bottom. Skier pulled airbag and was not buried. They were able to get back to the parking lot on their own power with their group. We will be gathering additional details today and thank the group for reaching out to us.

 

Photo looking up at the Captain’s Chair face and the chute on the far right of the photo. The debris can be seen coming from the slab out of view and over the lower rock band into the apron. Photo by party involved 4.15.23.

Avalanche Problem 1
  • Wet Loose
    Wet Loose
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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

Another warm day is on tap. We can expect the snow surfaces that heated up yesterday to have refrozen to some degree this morning. Those crusts will likely soften by midday and turn into a wet loose avalanche issue. As seen in the photo below, even small wet sluffs can turn into a bigger issues if they trigger a slab or simply entrain a lot of snow on the decent. Paying attention to how soft and ‘punchy’ the snow gets will be key in avoiding getting tangled up in one of these. A general rule of thumb is once the wet/moist snow is around 6″ deep then these avalanche start becoming dangerous and it’s time to move to a cooler aspect. Note that even northerly aspects are seeing the sun this time of year.

Many slopes are still just starting the transition to warming up and these wet loose sluffs will not pose as much of a threat. Other things to keep in mind are cornices. Cornices start to ooze over and become much more likely to trigger this time of year. Keep giving them a wide berth. For those hunting dry powder, see problem 2 below…

 

Photo is from the Whittier area above the Shotgun Cove road. This is a westerly aspect around 2,000′. A good example of the surface snow heating up and losing cohesion to point these sluffs release. 4.15.23.

 

Slab triggered by a snowmachiner in the Whittier area. The snow at this lower elevation, around 1,000′, was fairly wet when it was triggered. This area sees the spring avalanche danger a bit before Turnagain. Photo by Graham Predeger 4.15.23.

Avalanche Problem 2
  • 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

Easterly ridgetop winds bumped up early this morning, averaging in the teens and gusting near 30mph. The winds are supposed to quiet down around 9 or 10 am, but with a bit of snow to blow around in the higher elevations, shallow fresh wind slabs may have formed. With high northerly aspects the last place to find dry soft snow, this is where these slabs will be the most likely seen. Older lingering dry slabs could also be lurking, similar to that triggered on Captain’s Chair.

If you are headed to the upper elevation shady slopes in search of dry snow, keep a close eye on cracking in the snow around you, hollow feeling snow, signs of wind loading, and any other signs of unstable snow. It’s good for us to remember, even a smaller avalanche can have huge consequences in big steep rocky terrain.

Additional Concern
  • Deep Persistent Slabs
    Deep Persistent Slabs
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.
More info at Avalanche.org

While our main concerns lie in the upper snowpack, we know there is a suspect layer of rounding facets buried deeper in the pack (3-6′). This layer was responsible for many very large human triggered avalanches in the second half of March, but we have not seen any activity on it for almost three weeks. Although the layer appears to have gone dormant, it is still something we are keeping in the back of our minds, especially as the snowpack slowly warms. Once the snowpack really starts seeing significant warming, we are feeling like some big wet slabs may be in the future. Something we are keeping close eye on.

Weather
Sun, April 16th, 2023

Yesterday:  Mostly clear skies with some high clouds were over the region. Ridgetop winds were light from the east. Temperatures warmed into the 40’sF at lower elevations and close to 30 at the higher elevations.

Today:  Partly sunny skies with high clouds are expected again today. Ridgetop winds increased from the east early this morning (teens gusting near 30mph) and should calm down into the 5-10mph range after 10am. Temperatures again look to warm into the 40’sF at lower elevations and near 30F in the higher terrain.

Tomorrow:  Mostly clear skies are forecast for Monday. Ridgetop winds swing westerly (5-10mph) bringing cooler air. Daytime temperatures may not increase as much as we have seen this weekend.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35 trace 0 92
Summit Lake (1400′) 34 0 0 44
Alyeska Mid (1700′) 35 1 0.1 89
Bear Valley – Portage (132′) 39 0 0.1

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 26 NE 12 27
Seattle Ridge (2400′) 29 SE 5 30
Observations
Recent Observations for Turnagain Pass
Date Region Location
03/02/24 Turnagain Observation: Bertha Creek
03/02/24 Turnagain Observation: Magnum & Cornbiscuit
03/01/24 Turnagain Observation: Tincan Backdoor
02/29/24 Turnagain Observation: Silvertip Creek
02/29/24 Turnagain Observation: Eddies
02/27/24 Turnagain Observation: Seattle Ridge
02/25/24 Turnagain Observation: Kickstep NE Bowl
02/24/24 Turnagain Observation: TinCan Backdoor/ Center Ridge
02/22/24 Turnagain Avalanche: Lynx Creek
02/22/24 Turnagain Observation: Turnagain, Seattle, Mt Ascension
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.