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Issued
Wed, March 8th, 2023 - 7:00AM
Expires
Thu, March 9th, 2023 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger remains MODERATE above 1,000′. Another unseasonably warm day with abundant sunshine will again melt the surface snow on southerly aspects creating wet loose avalanches on steep slopes facing the sun. These can occur on their own as well as be easy to trigger. There is a possibility that these smaller avalanches could pull out bigger slabs on isolated slopes. It is important to pay attention to signs of warming and head to shadier aspects when conditions heat up in the afternoon. The danger will remain LOW below 1000′.

Wed, March 8th, 2023
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.
Recent Avalanches

The southerly facing slopes in the region are becoming riddled with wet loose avalanches over the past few days of warm weather. It is getting hard to tell what avalanches are new and what are from a few days ago. It did appear that a few new wet loose sluffs occurred yesterday on Seattle Ridge and thanks to folks on Center Ridge, we know of one larger wet sluff that occurred on Tincan Proper yesterday at 4:10pm. Photos below.

A few new wet loose avalanches on the roadside (SE face) of Seattle Ridge at Turnagain Pass. These types of small avalanches have been occurring for the past three days of warm weather. 3.7.23.

The debris that runs the furthest in this photo is a from a larger wet loose avalanche that occurred yesterday at 4:10pm. This is the southerly face of Tincan Proper and photoed from Center Ridge. Thanks the the Alaska Guide Collective for the photo. 

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

Springtime conditions are expected again today as temperatures continue to be exceedingly warm overnight (40’sF at Sunburst!) and then set on overdrive as the sun beats down on the southerly aspects through the day. We have seen countless small and some large wet loose avalanches occur naturally for the past three afternoons and today should be the same. These are starting to become larger and entraining more snow. They could also start pulling out slabs, making for an even larger avalanche. Example of this in the photo below from a zone to the south of the forecast area near Moose Pass.

The good thing is we can easily avoid being in the way of these by doing a few key things. First, be sure to monitor the surface conditions when on a southerly aspect. Once the sun crusts start to melt and become very soft, that’s when the snow becomes so weak it can easily avalanche. At this point it’s good to move to a shadier aspect. Also, these can run a surprising distance- so when traveling in valley bottoms or under slopes, we have to be sure to give plenty of space in case debris does come down a slope or gully.

It’s also good to remember the hottest part of the day is around 3 and 4pm and when these avalanches are most likely to occur. This is a couple hours after the sun is directly over us, which is solar noon and is just after 1pm right now. Starting Sunday, daylight savings, solar noon will be just after 2pm and the hottest time of day 4-5pm.

 

This avalanche occurred either Monday or Tuesday in the Moose Pass area on Madson Mtn. It is a good example of how a wet loose avalanche can trigger a slab below. 3.7.23.

 

Cornice falls are much more likely with warm temperatures and strong sunshine, so we have to be aware of cornices overhead and try to give them a wide berth along a ridgelines. A big chunk of cornice falling also has the potential to trigger a slab avalanche on the slope below.

Glide cracks have been opening up over the past several weeks and the rapid change in temperature could make them more likely to release. These things have a mind of their own and can really release under any conditions, so it is important to be aware of any glide cracks overhead and try to minimize time spent underneath them.

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

The rapid warming of the snowpack over the past few days could cause some of those old wind slabs or even those older buried weak layers to become active again. This is most concerning in isolated areas that have a thin overall snowpack and where some signs of instability have been seen over past couple weeks, such as near Crow Pass, Pete’s North, and areas around Johnson Pass. There was a skier triggered avalanche above Johnson Pass in the Bench Pk area two days ago (Monday). This slab is pictured below and looks to have released on an older weak layer around a foot or so deep. If traveling in these more remote areas with a thinner snowpack, extra caution is recommended.

 

Skier triggered avalanche on Monday on the far southern part of the forecast area above Johnson Pass in the Bench Pk region. Skier was able to self arrest and was not caught. 3.6.23. 

Weather
Wed, March 8th, 2023

Yesterday:  Mostly sunny skies were over the region with a few high clouds. Ridgeop winds were light from the west and north (5-10mph). Temperatures were incredibly warm along ridgelines (35-45F) and warmed from the teens to the mid 30’sF in valley bottoms.

Today:  Another sunny and hot springtime day is on tap. Temperatures should again be in the low 40’sF along the ridgelines. In valley bottoms they should climb from the teens, where they cooled overnight, to the mid 30’sF. Ridgetop winds remain light from the north and west until this evening when they should start picking up into the 10-15mph range.

Tomorrow:  Clear skies remain for the next several days however there are some changes. Another NW outflow wind event is forecast starting Thursday into Friday with winds in the 15-25mph range, possibly stronger on Friday. The winds will usher in cooler air and we should see temps drop back down to the teens and 20’sF.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 36 0 0 66
Summit Lake (1400′) 32 0 0 36
Alyeska Mid (1700′) 35 0 0 67
Bear Valley – Portage (132′) 22 0 0

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 41 W 9 17
Seattle Ridge (2400′) 37 NNE 4 8
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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.