Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Wed, March 16th, 2022 - 7:00AM
Expires
Thu, March 17th, 2022 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE on all aspects above 2,500′ due to strong east winds with several inches of new snow. Fresh wind slab avalanches in the 1-2′ deep range will be likely for people to trigger and may release naturally in the upper elevations. Winds may also build slabs below 2,500′ and a MODERATE danger exists where human triggered wind slabs are possible. Small wet sluffs could occur in the lower elevations as light rain on snow is likely this afternoon.

SUMMIT LAKE:  Despite almost no new snow expected for the Summit Lake area, strong winds may be able to form new wind slabs and increase avalanche danger here as well. Avalanches could step down into buried weak layers, resulting in a much larger avalanche.

Special Announcements
  • AKDOT&PF:  There will be intermittent traffic delays Wednesday March 16 on the Seward Highway from mileposts 100 to 90, Girdwood to Bird Creek for Avalanche Hazard Reduction work.  Motorists should expect delays of up to 45 minutes between 10:00 AM and 12:00 PM. See 511.alaska.gov for updates.
  • Don’t forget to stop by the Turnagain Pass motorized parking lot this Saturday!! The annual Turnagain Pass Avalanche Awareness Day is happening on March 19th. Grab a hotdog, chat with forecasters, practice with your beacon (beacon park provided by Anchorage Nordic Ski Patrol), and more. It’s always a fun event – see you there!
Thanks to our sponsors!
Wed, March 16th, 2022
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
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
Moderate (2)
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
  • 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

Well… we were hoping for a foot of new snow by today, but it appears we have to settle for half that, or less! As of 6am this morning, snowfall totals are 3-6″ in Girdwood Valley and only 1-3″ at Turnagain Pass. Weather models are showing only 1-3 additional inches to fall through the day with a rain/snow line rising to ~800′ by this afternoon. The easterly ridgetop winds however, are verifying. For the past 6-8 hours ridgetop stations have recorded 15-30mph averages and gusts into the 40’s and 50’s. That said, it’s a watch out for new wind slabs kind of day.

We can expect wind slabs to be forming predominantly in the Alpine, above 2,500′, and may be releasing naturally. How large they could be will depend on both the new snow amounts and how much soft pre-existing snow the winds will be able to move. The snow surface was a mixed bag before the storm; sun crusts on south aspects, stiffer wind crusts along ridgelines and soft settled snow on shaded slopes. Plus, all these surfaces were covered with a new batch of surface hoar. Hence, wind slabs could be anywhere from 6″ to 2′ thick. They could be quite touchy and easy to trigger as they are likely sitting on this new layer of surface hoar and possibly some loose near surface facets.

Taking stock of how much new snow has fallen along with active wind loading and areas with wind deposited snow will all be key. The classic red flags will also be useful in looking for unstable snow. These are any recent avalanches? Is the snow cracking around you and feel hollow? Any collapsing or whumpfing in the snow under you? All in all, we should steer clear of any wind loaded slope or cross-loaded gully. Exposed areas in the trees could also see some wind loading.

A new batch of surface hoar has been growing the past few days. It may have been blown over in many places before the snowfall, but it also may be standing up and not allowing the new snow to bond well. Photo by CNFAIC Intern Allen Dahl in Kern Creek around 2,600′ yesterday, 3.15.22.

 

Cornices:  Pieces, parts of even large sections of cornices may break off with these winds and could trigger an avalanche below. This is just one more thing to watch for, and avoid being near, if venturing out today.

Small dry and wet sluffs:  We can expect the new snow to sluff fairly easily on the older snow surface. With such meager new snow amounts, sluffs should be quite small. Dry sluffs are expected above ~1,000′ and wet sluffs below that due to rain/snow.

Glide cracks:  Warming temperatures through today and into the weekend may accelerate the opening of glide cracks and even cause a couple to release into avalanches. There are several of these cracks scattered about. Limiting and/or avoiding any time under them is highly recommended as they can release at any time.

Glide crack underneath the steep rocky bands. This crack was reported to be slowly opening in the past few days. It is on the Girdwood side of Crow Pass in the Crow Creek drainage. 3.15.22.

Avalanche Problem 2
  • Persistent Slabs
    Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
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.

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

Buried in the top 2 feet of the snowpack is an older layer of buried surface hoar and small facets. It was buried on March 2nd and was the cause of several avalanches over a week ago. The last known avalanche on this layer was last Saturday in the Bertha Ck drainage at Turnagain Pass. The layer has appeared to adjust and gain strength, but with a little new snow and especially wind loading, we are watching to see if any wind slab avalanches overload this layer and cause a larger slide today.

Weather
Wed, March 16th, 2022

Yesterday:  Mostly clear skies with valley fog was present yesterday morning before clouds move in midday. Ridgetop winds picked up from the E to SE midday (10-15mph) before climbing further overnight into the 20-30mph range with gusts into the 50’s.  Overnight between 2-5″ of snow fell to sea level (Girdwood Valley saw the higher amounts).

Today:  The storm that was hopefully going to add up to a foot of snow today has pushed to the east and we are expecting cloudy skies with only an additional 1-3″ by tonight. The rain/snow line looks to creep up to ~800′ by this afternoon. Ridgetop easterly winds should slowly lessen through the day from 20-30mph range (gusts to 50mph) this morning to 10-15mph (gusts to 30mph) by this evening.

Tomorrow:  Continued cloudy skies with light to moderate precipitation should remain through tomorrow and into the weekend. Sea level elevations should see fluctuations of rain and snow while all snow should fall above 600-800′. Ridgetop winds will remain easterly in the moderate range (10-30mph).

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 27 2 0.1 92
Summit Lake (1400′) 20 0 0 39
Alyeska Mid (1700′) 26 5 0.3 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) N/A* N/A* N/A* N/A*
Seattle Ridge (2400′) 21 SE 14 26

*The sunburst weather station has lost power, we are working to get it back online as soon as possible.

Observations
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Riding Areas
Updated Fri, May 13th, 2022

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 as of May 1 per Forest Plan.
Placer River
Closed
Closed as of April 25th due to insufficient snow coverage.
Skookum Drainage
Closed
Closed as of April 1st per Forest Plan.
Turnagain Pass
Open
Open. Extended opening through May 31.
Twentymile
Closed
Closed as of April 6th due to insufficient snow coverage.
Seward District
Carter Lake
Closed
Closed as of May 1 per Forest Plan.
Lost Lake Trail
Closed
Closed as of May 1 per Forest Plan.
Primrose Trail
Closed
Closed as of May 1 per Forest Plan.
Resurrection Pass Trail
Closed
Closed as of May 1 per Forest Plan.
Snug Harbor
Closed
Closed as of May 1 per Forest Plan.
South Fork Snow River Corridor
Closed
Closed as of May 1 per Forest Plan.
Summit Lake
Closed
Closed as of May 1 per Forest Plan.

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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.