Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, February 6th, 2021 - 7:00AM
Expires
Sun, February 7th, 2021 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 2,500′ and MODERATE between 1,000′ and 2,500′ due to an increase in northwest winds forecast today. Any slope seeing wind loading will be forming fresh and touchy wind slabs up to a foot or more deep, easily triggered by a person. Above 2,500′ the stronger winds may create naturally releasing wind slab avalanches and cornice falls. Today’s danger all depends on how much wind is impacting the mountains. Pay close attention to pluming and where winds are loading slopes. Out of the wind, watch for old wind slabs sitting on weak snow that could still be triggered and sluffing on steep slopes.

The avalanche danger is LOW below 1000’.

SUMMIT LAKE:  Strong NW winds are expected in this zone. Not only will new wind slabs be easy to trigger, naturals are possible. With multiple buried weak layers in the snowpack, wind slabs could step down and create a larger avalanche than expected. Extra caution is advised.

LOST LAKE/SNUG/SEWARD:  NW winds are also expected to impact the Kenai Mtns closer to Seward. Be suspect of any slope seeing wind loading as is mentioned above. Natural wind slab avalanches are possible here as well if the wind verifies.

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Sat, February 6th, 2021
Alpine
Above 2,500'
Considerable (3)
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
Considerable (3)
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)
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    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

Say it isn’t so…the northwest winds look to be arriving. It may be a sunny day out there, but expect cold and windy conditions along the ridgelines. The forecast is for sustained speeds of 25-35 mph. We know from past wind events, this can result in stronger winds along Turnagain Arm and Portage Valley, through Crow Pass and in Summit Lake. Turnagain Pass can sometimes be spared much of the wind, but not always. In fact, this NW flow is notorious for channeling through the Pass from the south, loading northerly aspects on the non-motorized side of the road. Sometimes this occurs just at the mid-elevations, while the peaks remain in the NW flow. This direction can also top-load Seattle Ridge as winds load the road-side SE face of the ridge. In short, it’s a day to watch for what the winds are doing, or hopefully not doing…

Areas the winds are impacting: With a foot or more of very loose unconsolidated surface snow available for transport at the mid and upper elevations, touchy wind slabs should easily form where wind loading is taking place. The higher in elevation, the more wind and loading is expected. Not only will fresh wind slabs be easy to trigger, natural wind slab avalanches are also possible. Expect them to vary in size, from shallow and only 6″ thick to up to 2′ in places. Although outside of our forecast zone, this flow will often produce a natural wind slab cycle in the central Kenai Mtns, including Summit Lake.

Areas out of the wind: If you find yourself in an area without wind effect, remember to watch for old wind slabs around a foot thick that could be resting on buried surface hoar and facets. Although becoming less likely to find, there is still a chance a persistent slab avalanche could be stumbled upon and triggered. What is more likely in areas out of the wind is sluffing in steep terrain. Sluffs have been running fast and gaining volume with the loose faceting surface snow.

Cornices:  Winds today may build and break off chunks of cornices, which could in turn trigger a wind slab below. Otherwise, it will be the normal caution routine of giving cornices a wide berth and limit time under them.

A look at the top foot of the snowpack on Tincan from yesterday. Note the loose snow above the buried surface hoar. 2.5.21.

Additional Concern
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

There have been no recent reports of glide cracks releasing. However, cracks are still opening up and moving. This tells us that releases are possible and as is common practice, avoiding being under cracks is prudent. These are completely unpredictable beasts.

Weather
Sat, February 6th, 2021

Yesterday: Overcast skies were over the region most of yesterday as a band of clouds moved through. No precipitation was reported and temperatures were pleasant (~20F) along ridgetops while valley bottoms hovered in the single digits. Ridgetop winds were light from the west.

Today: Skies have cleared again and a sunny day is on tap. The big news is the northwest winds. These increased overnight and are expected to continue through today along the ridgelines in the 25-35mph range with stronger gusts. Temperatures have dropped with more cold air streaming in. Upper elevations will be near 10F while mid elevations could stay in the teens and valley bottoms are in the single digits.

Tomorrow: Sunny skies and continued cold temperatures are expected for Sunday and into Monday. Ridgetop northwest winds are forecast to ease to the 10-20mph range. A hint of precipitation with cloudy skies is showing up on models for the mid to latter part of the week.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 17 0 0 119
Summit Lake (1400′) 7 0 0 44
Alyeska Mid (1700′) 13 0 0 109

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 16 NW 14 31
Seattle Ridge (2400′) 18 NW 8 24
Observations
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Riding Areas
Updated Tue, June 01st, 2021

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
Placer River
Closed
It is packrafting and jetboat season!
Skookum Drainage
Closed
The Skookum Valley is closed to snowmachines. This closure occurs annually on April 1 as per the CNF Forest Plan.
Turnagain Pass
Closed
Closed as of June 1. 188 day season, that\'s a wrap!
Twentymile
Closed
It is packrafting and jetboat season!
Seward District
Carter Lake
Closed
Closes May 1.
Lost Lake Trail
Closed
Closes May 1.
Primrose Trail
Closed
Closes May 1.
Resurrection Pass Trail
Closed
Closed for the 2020/21 winter season. Will be open for moto use in the 21/22\\\' winter season as per the CNF Forest plan.
Snug Harbor
Closed
Closes May 16th.
South Fork Snow River Corridor
Closed
Closes May 1.
Summit Lake
Closed
Closes May 1.

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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.