Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, April 7th, 2022 - 7:00AM
Expires
Fri, April 8th, 2022 - 7:00AM
Forecaster
Graham Predeger
Avalanche risk The Bottom Line

There is a MODERATE avalanche danger on all aspects above 1,000’ today.  It will be possible to trigger a lingering wind slab 12-18” deep on wind loaded slopes given the moderate  southeasterly winds that we’ve seen impact the core advisory area between Tuesday morning and Wednesday afternoon.  Additional concerns include a crust/ weak layer combo buried on April Fool’s Day that was responsible for a skier-triggered slab on Monday and the potential for wet loose activity in steep southerly terrain late in the day.

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Thu, April 7th, 2022
Alpine
Above 2,500'
Moderate (2)
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
Moderate (2)
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 (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    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

The shocker over the past two days in the field was just how much snow there is available for transport above ~1,500’.  Moderate southeasterly winds have been able to move snow and build shallow wind slabs over the past two days.  Though winds began to subside yesterday afternoon, it will be possible to kick off a lingering wind slab today, particularly on north and west facing terrain above where the snow surface dries out.  Cross loaded gullies and mid-slope convexities that sport a smooth, rounded look or hollow feeling snow should be suspect.  Any shooting cracks as you step out of the skin track or off your sled should be a bull’s eye clue that you’re dealing with a wind slab issue.  Relatively benign weather today shouldn’t be adding much additional stress to the snowpack, but finding a lingering wind slab will still be possible in the upper elevation areas harboring dry snow.

Moderate southeasterly winds over the past two days have been enough to build wind slabs in leeward terrain.  Photo: Comet Peak in the Placer Valley, 4.6.22.

Wet loose: Expect mostly sunny skies to heat up southerly slopes this afternoon/ evening.  As we’ve seen the last couple of days, natural and human-triggered wet loose activity will be on the rise later in the day.  Though likely a manageable problem, there is potential a wet loose avalanche could step down to a known crust/ weak layer combo from the beginning of April.  More on that below.

Cornices:  They’re as big as they’ve been all season and today’s weather/ snowpack will allow folks to be travelling along ridges.  Give cornices an extra wide berth and don’t let your guard down as you move along a corniced ridge toward your objective.

Avalanche Problem 2
  • Persistent Slabs
    Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    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

The crust/ weak layer combo affectionally referred to as the ‘April Fool’s interface’ (given the date it was buried) is proving more stubborn in snow pit tests as the week goes on.  That said, this was the culprit in an active natural avalanche cycle last weekend and most recently, a skier triggered avalanche on Monday in the Seattle Creek area.  The interface is 1-2’ deep now and though unlikely to trigger, the structure (crust/ surface hoar/ facet combo) is concerning enough that we can’t forget about it.  A lingering wind slab, cornice fall or wet loose avalanche could provide enough of a punch to step down to this April Fool’s interface, particularly on steep, unsupported slopes.

Deep Persistent Slabs: 

If you’ve been following along over the past several weeks, you’ll know that buried 3-6’ down in our snowpack we have a couple other persistent weak layers we’re tracking.  This is a low probability, high consequence avalanche problem right now meaning it’s very unlikely to trigger an avalanche this deep but if you do, it’d be very large given the depth of the weak layer.  We’ll continue to track these layers with any new loads or rapid warming events as our snowpack continues its inevitable transition toward whitewater rapids and salmon habitat!

Weather
Thu, April 7th, 2022

Yesterday: No measurable precip to report yesterday as high clouds gave way to mostly clear skies by mid day.  Ridgetop winds were southeasterly gusting in the mid to high 20s mph.  Temps were in the low to mid 20s F at ridgetop locations and high 30s to low 40s F in Valley bottoms.

Today: Winds will be light and variable with temps in the mid-20s F at ridgetops and mid 30s to low 40s F at sea level.  No new precip is expected today.

Tomorrow: A weak low pressure over the eastern Gulf of Alaska is expected to track into western Prince William Sound late tonight/ tomorrow morning bringing with it a chance for a few inches of snow to sea level.  Cooler temps and increasing winds from the NW should be expected as this weak storm system gives way to sunshine and high pressure for the weekend.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 32 0 0 115
Summit Lake (1400′) 33 0 0 41
Alyeska Mid (1700′) 32 0 0 n/a

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 20 E 14 32
Seattle Ridge (2400′) 24 SE 10 20
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Riding Areas
Updated Wed, December 07th, 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
The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Placer River
Closed
The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Skookum Drainage
Closed
The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Turnagain Pass
Closed
The Forest has issued a closure order for Turnagain Pass due to inadequate snow cover for resource protection. Conditions are being monitored daily. 22” of snow exists at the parking lot. Another storm on Sunday/Monday 12/11 may just do it.
Twentymile
Closed
The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Seward District
Carter Lake
Closed
The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Lost Lake Trail
Closed
The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Primrose Trail
Closed
The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Resurrection Pass Trail
Closed
Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor
Closed
The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
South Fork Snow River Corridor
Closed
The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Summit Lake
Closed
The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.

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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.