Turnagain Pass Avalanche Forecast
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The avalanche danger is expected to rise to CONSIDERABLE above 2,500′ today due to strong northwest winds forecast to impact the region. In this case, wind slab avalanches and cornice falls may occur naturally on upper elevation slopes seeing active wind loading. Human triggered wind slab avalanches around a foot deep will be likely on any slope with new wind deposited snow. In areas without wind effect, the danger is MODERATE where human triggered slab avalanches 1-2′ deep remain possible at all elevations due to buried weak layers.
*Gap winds squeezing through Crow Pass and Portage Pass are expected to be strong. Natural avalanches are possible in these windy areas.
SUMMIT LAKE/LOST LAKE/SNUG: The central Kenai Mountains often see the brunt of northwest winds such as these. If the winds verify here, a natural wind slab avalanche cycle is possible.
REGION-WIDE Winds: Strong northerly winds are impacting many areas around Southcentral, including Anchorage’s Front Range. A reminder that strong winds can increase the avalanche danger quickly on any slope seeing wind loading.
Girdwood Valley, under Notch Mtn (1600-1700′ elevation, WNW facing): A group of skiers knocked a small cornice chunk onto a small steep slope and triggered this persistent slab avalanche yesterday. It was up to 2′ deep at its max and 100′ wide. This avalanche failed in a weak layer of facets on top of a 3-4″ thick buried melt/freeze crust.
Photo of the persistent slab avalanche described above. 2.18.21.
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 |
It is a day to pay close attention to what the winds are doing and avoid slopes with fresh wind deposited snow. As of 6am this morning, the weather stations are still reporting light to moderate NW winds, however, that could all change quickly through the course of the day. How much snow is available for transport is somewhat variable, anywhere from 4-12″ (plus or minus) depending on your location.
If these winds do verify, we can expect to see plumes off the peaks and the potential for natural wind slabs and cornice falls, especially in areas such as Crow Pass and Portage Valley. Additionally, this will be most likely in the Alpine, above the trees, yet watching for wind loading at the mid elevations will be key as well. New wind slabs could be up to a foot thick and possibly thicker. If found, they are likely to be easy to trigger and could step down to old buried weak layers below. In this case, a larger avalanche is possible. Along with watching for active wind loading, feeling for stiff snow over softer snow and watching for cracks that shoot out from you will be signs you’ve found a wind slab.
This flow direction is tricky for Turnagain Pass. It can funnel through the Pass from the south and load north aspects on the non-motorized side, while at the same time load the SE face of Seattle Ridge. It can also split around the Pass and not affect much of the terrain in the heart of Turnagain at all. You might find you are in an area that is seeing no wind, or not enough to move the surface snow into wind slabs. If this is the case, see below as there are some buried weak layers still causing concern.
View from Tincan yesterday that looks SE over 4-6″ of low density snow from the past couple days. 2.18.21.
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 |
Buried in the top 2′ of the snowpack, likely deeper in areas near Portage and Placer Valley, are a couple of weak layers (facets and buried surface hoar). At the lower elevations, below 1,600′ at Turnagain Pass and 2000′ in Girdwood and Placer Valley, a crust sits just under one of these faceted layers. This was the setup in the avalanche triggered under Notch Mtn yesterday. Crusts can accentuate this persistent slab problem by providing a slick bed surface, encourage wider propagation if an avalanche is triggered and inhibit the weak layer from gaining strength.
In short, the reactivity of these weak layers continues to be quite variable around the region; meaning whether they are able to cause an avalanche or not. They may be sitting under old wind slabs and hard to identify. Snowpack tests are pointing to both good and not so good stability, making it difficult to truly assess how stable steep slopes are. As Aleph said yesterday, this uncertainty makes the whole situation tricky and the snowpack not that trustworthy… Simply knowing these weak layers exist, watching for signs of instability and following safe travel protocol can help hedge our bets if choosing to push into steeper terrain. Add to that, digging a representative snowpit and assessing the pack yourself is a great way to get more information for the slope in question.
Yesterday: Mostly cloudy skies were over the region with light and variable winds. Girdwood and Portage/Placer picked up an inch or two of snow early yesterday morning before the sun tried to poke through the clouds. Temperatures were in the 20’sF at the mid and upper elevations.
Today: Despite the sunny skies, a cold northerly wind has developed overnight, which is impacting much of Southcentral. Temperatures have plummeted to the single digits along ridgetops and valley bottoms should see temperatures dip to the teens through the day. The northwest winds are forecast to average 25-35mph along the ridgelines by this afternoon before decreasing late tonight.
Tomorrow: Mostly sunny skies are expected for tomorrow and Sunday along with light and variable winds. Temperatures will remain cold however, in the single digits and even the minus single digits in some valley bottoms.
PRECIPITATION 24-hour data (6am – 6am)
Temp Avg (F) | Snow (in) | Water (in) | Snow Depth (in) | |
---|---|---|---|---|
Center Ridge (1880′) | 28 | 0 | 0 | 116 |
Summit Lake (1400′) | 27 | 0 | 0 | 44 |
Alyeska Mid (1700′) | 28 | 2 | 0.1 | 115 |
RIDGETOP 24-hour data (6am – 6am)
Temp Avg (F) | Wind Dir | Wind Avg (mph) | Wind Gust (mph) | |
---|---|---|---|---|
Sunburst (3812′) | 18 | W | 6 | 21 |
Seattle Ridge (2400′) | 20 | NW | 9 | 24 |
Date | Region | Location | Observer |
---|---|---|---|
05/22/23 | Turnagain | Avalanche: Tincan | Nick D'Alessio |
05/12/23 | Turnagain | Avalanche: Tincan, Sunburst, Magnum, Cornbiscuit | Heather Thamm |
05/07/23 | Turnagain | Observation: Tincan – Bear Tracks | CNFAIC Staff |
05/05/23 | Turnagain | Observation: Seattle Ridge | AS/ WW Forecaster |
05/02/23 | Turnagain | Observation: Cornbiscuit | Schauer/ Sturgess Forecaster |
05/02/23 | Turnagain | Observation: Seward Hwy Turnagain Pass | Joel Curtis |
04/30/23 | Turnagain | Observation: Magnum | Ayla, Kit Crosby, Barton |
04/29/23 | Turnagain | Observation: Tincan | John Sykes |
04/28/23 | Turnagain | Avalanche: Taylor Pass/Pastoral | Schauer/ Creighton Forecaster |
04/28/23 | Turnagain | Avalanche: Tincan | Andy Moderow |
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 |
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Glacier District |
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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.