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Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, November 29th, 2019 - 7:00AM
Expires
Sat, November 30th, 2019 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

The avalanche danger is CONSIDERABLE at all elevation bands. In the Alpine and Treeline triggering a slab avalanche is likely and natural avalanches are possible. Avalanches that release in higher elevation terrain could send debris into the lower elevation (below 1000′) runout. Cautious route-finding and conservative decision-making are essential.

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Fri, November 29th, 2019
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
Considerable (3)
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
Considerable (3)
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
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

Welcome to winter… ish. It’s currently 40F in Girdwood this morning. After two days of stormy weather precipitation is forecast to decrease today but easterly winds will remain fairly strong. Storm snow avalanches, including wind slabs along ridgelines, storm slabs in the sheltered zones, cornice falls and wet loose snow sluffs where rain is falling, should all be viewed as likely today. It’s a day to carefully evaluate terrain and consequences if an avalanche does release. The mountains need time to adjust.

Red flags to watch for:
– Recent avalanches – Are avalanches occurring today? Was there avalanche activity during the storm?
– Whumpfing (collapsing) of the snowpack
– Shooting cracks, likely to be seen near ridgelines where the wind has formed wind slabs.

Storm totals (beginning Wednesday through 6am Friday):

Turnagain Pass at 1,880′: 1.9″–  of water equivalent, roughly 1.5-2′ of snow above treeline
Girdwood Valley at 1,700′: 3.6″ of water equivalent, roughly 2.5-3.5′ above treeline
Portage Valley at sea level: 5.3″ of water equivalent, roughly 5′ of snow above treeline
Summit Lake at 1,400′: 1.2″ of water equivalent, roughly 1′ of snow above treeline.

It is early in the season and overall we have limited snowpack data, especially in the Alpine (above 2500′) where most of the snow fell. What we do know is that the existing snowpack just got a heavy load. The storm was upside down with heavier snow falling on lighter snow or rain falling on snow. The winds were sustained and strong. Caution is advised. There is a long winter ahead. Don’t let early season stoke get the best of you!

Scouring and loading in the Tincan Alpine, 11.27.19

Weather
Fri, November 29th, 2019

Yesterday: Rain and snow fell throughout the day with snow line increasing to approximately 2200′ as temperatures rose well above freezing at lower elevations. In the past 24 hrs Girdwood received 1.5″ of water, Turnagain Pass 0.9″, and Portage (Bear Valley) 3.4″ with upper elevations seeing snow. Easterly winds were in the 30s with gusts into the 60s. Overnight temperatures were in the 40Fs at sea level, 30Fs at mid elevations and 20Fs at ridgetops.

Today: Rain and snow showers will continue today with snow line forecast to be around 2400′, 0.3 inches of water and 0-6″ of snow. Temperatures will be in the low 40Fs at sea level and the high 20Fs along ridgetops.  Winds are forecast to be easterly 15-35 mph with gusts into the 50s. Overnight temperatures should cool a bit and rain/snow showers will continue with snow line dropping to 1500′. Winds will remain easterly gusting into the 40s.

Tomorrow: Cloudy skies with rain and snow showers and daytime temperatures just slightly cooler than today. Easterly winds will decrease to 5-10 mph. The pattern looks to remain active into next week with an overall cooling trend.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35 1 0.9 15
Summit Lake (1400′) 34 0 0.3 8
Alyeska Mid (1700′) 33 5 1.44 20

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 25 NE 32 68
Seattle Ridge (2400′) NA* SE* 15* 35*

*Seattle Ridge is not recording temperature and wind stopped recording at 10 pm.

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Riding Areas
Updated Fri, May 01st, 2020

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
Skookum Drainage
Closed
Turnagain Pass
Closed
Closed as of May 1. Thanks for a fun, safe season!
Twentymile
Closed
Seward District
Carter Lake
Closed
Lost Lake Trail
Closed
Primrose Trail
Closed
Resurrection Pass Trail
Closed
Snug Harbor
Closed
South Fork Snow River Corridor
Closed
Summit Lake
Closed

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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.