Turnagain Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, January 26th, 2018 - 7:00AM
Expires
Sat, January 27th, 2018 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

Today there is CONSIDERABLE  avalanche danger above 1000′ (in the Alpine and Treeline zone) where triggering a storm slab 1-2 feet deep will be likely in areas exposed to recent wind. If ridge top winds remain elevated today, natural slab avalanches and loose snow avalanches will be possible. Evaluate snow conditions as you move up in elevation and keep your terrain choices mellow, less than 30 degrees. Cautious routefinding, and conservative decision making are essential. In places protected from wind triggering a loose snow avalanche will be likely on steep features. Also don’t forget – high in the alpine above 3000′, Deep Slab avalanche (3-8+ feet) will be stubborn to trigger, but could have high consequences.  

Below Treeline (1000′) and in places protected from recent wind the avalanche danger is MODERATE where triggering a storm slab 1-2 feet deep or loose snow avalanche is possible. Be aware of runout zones, terrain traps and other people around you.  

Thanks to our sponsors!
Fri, January 26th, 2018
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
Moderate (2)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Considerable (3)
Below Treeline
Below 1,000'
Avalanche risk
Moderate (2)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    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.

Likelihood of Avalanches
This graphic depicts how likely you are to trigger avalanches or encounter natural avalanches while traveling on avalanche prone slopes. Unlikely means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. The chance of triggering or observing avalanches increases as we move up the scale. Certain means that humans will be able to trigger avalanches on many slopes, and natural avalanches should be expected.

Size of Avalanches
This graphic depicts the potential size and destructive force of expected avalanches. 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, large enough to bury or destroy vehicles and break a few trees, and large enough to destroy railway cars, buildings, or a substantial amount of forest. Historic avalanches are massive events capable of destroying villages and gouging or altering the landscape.
More info at Avalanche.org

A sneaky storm overnight produced an estimated 10-20”  (0.5”-1.0” water weight) of low-density snow across our region and ridge top winds increased into the 20-40mph range last night. This snow started out with light wind and single digit temps, but temperatures suddenly bumped into the 20F’s along with a spike in Easterly winds. This means storm slabs in the alpine could range from 1-2’ deep, have an upside down quality, and could be easy to trigger. This snow fell on 5” of low density snow that was covering a widespread layer of buried surface hoar and near surface facets. Below 2000′ these layers are sitting on a slick bed surface crust. Bonding along these older interfaces is expected to be poor. Triggering a storm slab could be big enough to bury a person, but will depend on how deep the snow in the area you are traveling. The deeper the new snow the bigger the consequence. Clearing skies combined with high quality skiing/riding conditions may be hard to resist. Evaluate snow conditions as you move up in elevation and avoid terrain traps and being on or underneath larger steep slopes. Triggering a storm slab could run farther and faster than expected, which is the nature of cold snow. Shooting cracks, ‘whumpfing’, and any avalanche activity will be obvious clues that the snow is unstable.  Be aware of other groups of people in the same area and practice safe travel protocols. 

Notice the sudden spike in temps and winds last night. This combined with an estimated 10-20″ of new snow are all red flags warning signs that avalanche danger is elevated. 

Web cam at DOT weather station is one of the only views of how much snow has accumulated overnight at Turnagain Pass.  24 hr snow water equivelent was not reporting at this site this morning. 

 

Avalanche Problem 2
  • Dry Loose
    Dry Loose
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

Likelihood of Avalanches
This graphic depicts how likely you are to trigger avalanches or encounter natural avalanches while traveling on avalanche prone slopes. Unlikely means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. The chance of triggering or observing avalanches increases as we move up the scale. Certain means that humans will be able to trigger avalanches on many slopes, and natural avalanches should be expected.

Size of Avalanches
This graphic depicts the potential size and destructive force of expected avalanches. 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, large enough to bury or destroy vehicles and break a few trees, and large enough to destroy railway cars, buildings, or a substantial amount of forest. Historic avalanches are massive events capable of destroying villages and gouging or altering the landscape.
More info at Avalanche.org

In places protected from the winds loose snow avalanches ‘sluffing’ will be likely on steep terrain features. Similar to a storm slab, this dry loose snow could run faster and farther than expected. This hazard could bury a person in a terrain trap or underneath a large slope. 

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

Unfortunately, the snowpack structure above 3000′ is composed of a hard slab (3-8 feet thick) sitting on a variety of weak layers in the mid pack (including buried surface hoar) and old November facets near the ground. Deep persistent slab avalanches remain a concern on these upper elevation slopes. Triggering a deep slab is becoming difficult, but is still possible. The most likely trigger spots are thin areas in the snow cover, often near rocks, or where the slope rolls over.  South of Turnagain Pass the snow cover is thinner, triggering a slab in this area could be more likely as well. Remember, this is a ‘low probability, high consequence’ situation. This issue can simply be avoided by sticking to terrain below 3000’ (which is a good portion of terrain at Turnagain) and is secondary to triggering a storm slab avalanche today. Choosing low-consequence terrain in the Alpine is recommended. 

 

Weather
Fri, January 26th, 2018

Yesterday a storm brought an estimated 10-20 € of snow across our region. Center Ridge weather station picked up 0.5 € of water and Alyeska Midway, 0.7 € water, and Portage Valley (at Bear Valley) had 1.1 € of water. This storm also started light winds and single digit temperatures. Yesterday evening temperatures suddenly increased into the 20F’s and Northeasterly ridge top winds picked up into the 15-40mph range yesterday evening and overnight.  

Today ridge top winds are expected to decrease, but could range from 5-20 mph from the East. Skies could range from partly cloudy to overcast and temperatures are expected to be in the 20F’s. Scattered snow showers are expected this evening.

Snow showers are expected through Saturday morning with only a few inches of accumulation expected. Temps will be in the teens (F) and moderate to strong winds are in the forecast for the weekend. In the long term forecast there is talk of warming temps and a chance for more precipitation mid week.  

*Snow totals are estimated from the Center Ridge Weather Station. They could be deeper, but snow depth sensor was not reading depths as of 6am.  

Web cam at Bear Valley in Portage. Looks like almost a 1.5′ of snow in Portage overnight.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 11   *10   .5   *67
Summit Lake (1400′) 6   7   .3   22  
Alyeska Mid (1700′) 10   12   .7   59  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 5   ENE   13   44  
Seattle Ridge (2400′) 3   E    8 21  
Observations
Recent Observations for Turnagain Pass
Date Region Location
12/06/19 Turnagain Avalanche: Sunburst
12/04/19 Turnagain Observation: Sunburst
12/03/19 Turnagain Observation: Hippy Bowl
12/01/19 Turnagain Observation: Tincan, All elevations
12/01/19 Turnagain Observation: Tincan
11/30/19 Turnagain Observation: Tincan Treeline Plateau/ Common Bowl/ Ridge
11/29/19 Turnagain Observation: Sunburst Ob #2
11/29/19 Turnagain Observation: Sunburst Ob #1
11/27/19 Turnagain Observation: Tincan
11/25/19 Turnagain Observation: Sunnyside
Riding Areas
Updated Mon, December 02nd, 2019

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
Closed
Closed.
Placer River
Closed
Closed.
Skookum Drainage
Closed
Closed.
Turnagain Pass
Closed
Closed.
Twentymile
Closed
Closed.
Seward District
Carter Lake
Closed
Closed.
Lost Lake Trail
Closed
Closed.
Primrose Trail
Closed
Closed.
Resurrection Pass Trail
Closed
Closed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor
Closed
Closed.
South Fork Snow River Corridor
Closed
Closed.
Summit Lake
Closed
Closed.

Subscribe to Turnagain Pass
Avalanche Forecast by Email