Turnagain Pass Avalanche Forecast RSS

Archives
Issued
Thu, January 23rd, 2020 - 7:00AM
Expires
Fri, January 24th, 2020 - 7:00AM
Forecaster
Ryan Van Luit
The Bottom Line

Today the avalanche danger is MODERATE in the Alpine.  An increase in winds are forecast and triggering a fresh wind slab avalanche, composed of the loose snow from the storm on 1/20, is possible.  Where wind has not had an affect, and below 2500′, the danger is LOW where concerns for human triggered loose sluff slides remain predictable in steep terrain.  Any loose dry snow could quickly gain momentum and volume to take a rider off their feet, or potentially trigger a layer deeper within the snowpack.

SUMMIT LAKE: This region is just out of our advisory area to the south. The snowpack is shallow and extra caution is advised for triggering a slab avalanche in buried weak layers.

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Thu, January 23rd, 2020
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Low (1)
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
Low (1)
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
This graphic depicts how likely you are to trigger avalanches or encounter natural avalanches while traveling on avalanche prone slopes. Unlikely means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. The chance of triggering or observing avalanches increases as we move up the scale. Certain means that humans will be able to trigger avalanches on many slopes, and natural avalanches should be expected.

Size of Avalanches
This graphic depicts the potential size and destructive force of expected avalanches. 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, large enough to bury or destroy vehicles and break a few trees, and large enough to destroy railway cars, buildings, or a substantial amount of forest. Historic avalanches are massive events capable of destroying villages and gouging or altering the landscape.
More info at Avalanche.org

Weather models suggest that parts of the advisory will see a rise in wind from the northwest today with moderate speed, 15-20mph.  Continued cold temperatures have kept Monday’s 10″ of dry snow very loose, which can easily be blown around by these winds, creating wind slabs in the lee of ridges and gullies.  Winds slabs may form rapidly.  Where these conditions align, it’s possible for a human to trigger a wind slab.

Remain alert for signs of wind slab formation: watch for active wind loading, firmer surface conditions, cracking or drum-like sounds in the snow,  sometimes texture that appears rippled or wavy, and pillow-like features on the leeward side of wind exposed terrain.  And as always, if you see cracking in the snowpack or hear whumpfing sensations, it’s time to reassess your plan.

Persistent Slab:  Although unlikely, a loose dry avalanche or wind slab avalanche could step down and pull out a deeper slab. This is most suspect in Alpine elevation steep terrain.

Thick valley fog was over Turnagain Pass yesterday that extended from around 2,000′ to 3,000′. This photo was taken on Seattle Ridge and looking west toward Big Chief. 1.22.20.

Avalanche Problem 2
  • Dry Loose
    Dry Loose
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

Likelihood of Avalanches
This graphic depicts how likely you are to trigger avalanches or encounter natural avalanches while traveling on avalanche prone slopes. Unlikely means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. The chance of triggering or observing avalanches increases as we move up the scale. Certain means that humans will be able to trigger avalanches on many slopes, and natural avalanches should be expected.

Size of Avalanches
This graphic depicts the potential size and destructive force of expected avalanches. 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, large enough to bury or destroy vehicles and break a few trees, and large enough to destroy railway cars, buildings, or a substantial amount of forest. Historic avalanches are massive events capable of destroying villages and gouging or altering the landscape.
More info at Avalanche.org

Although the models predict wind, many areas have stayed calm since Mondays storm where 10″ of snow sits atop a 8″-12″ layer of loose facets.  We’ve not seen or heard reports of Mondays storm gaining any slab character, but it is settling over time.  As temperatures remain cold, the character of the recent surface snow is unlikely to create a slab unless it becomes wind effected.  Prior to Mondays storm, it remained easy for a rider in steep terrain to trigger sluff of loose facets.  Now, a relatively dry 10″ of snow adds to the volume of loose snow.  Triggering this loose snow is predictable and may be managed with forethought.  With that said,  20″ of loose snow could rapidly gain volume and momentum taking a rider through the fall line.

We’ve had a week with calm winds with light gusts at the Sunburst Weather Station.

 

Seattle Ridge weather station – relatively calm winds before and since the 1/20 storm

 

Cornices and Glide Cracks:  As always, limit exposure under glide cracks and give cornices a wide margin.

 

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Weather
Thu, January 23rd, 2020

Yesterday:  Thick valley fog remained in the 2000′-3000′ range for most of the day.  Temperatures were in the single digits above 3,500′.  At the lower elevations, temperatures remained in the teens trending into the single digits. Ridgetop winds were calm to light.

Today:  Mostly sunny skies with a high near 7°F, with a low around -5°F. No chance of precipitation today.  Winds will be out of the northwest from 15 to 20 mph and taper to light this evening.

Tomorrow:  Mostly sunny trending to cloudy into afternoon and evening with a high near 1°F and a low around -5°F. Light to calm winds around 5 mph.  No precip.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 9 0 0 44
Summit Lake (1400′) 8 0 0 16
Alyeska Mid (1700′) 11 0 0 46

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 4 W 2 5
Seattle Ridge (2400′) 5 NNE 2 6
Observations
Recent Observations for Turnagain Pass
Date Region Location
01/22/20 Turnagain Observation: Sunburst
01/22/20 Turnagain Observation: Sunburst
01/22/20 Turnagain Observation: Seattle Ridge
01/22/20 Turnagain Observation: Tincan
01/21/20 Turnagain Observation: Tincan
01/20/20 Turnagain Observation: Eddies
01/20/20 Turnagain Observation: Eddies
01/19/20 Turnagain Avalanche: south facing aspect on 3800ft bump just northeast of 4940
01/19/20 Turnagain Avalanche: Cornbiscuit & Magnum
01/19/20 Turnagain Observation: Eddie’s
Riding Areas
Updated Wed, January 22nd, 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
Open
Placer River
Open
Skookum Drainage
Open
Turnagain Pass
Open
Twentymile
Open
Open to over snow travel on 1/22.
Seward District
Carter Lake
Open
Lost Lake Trail
Open
Open to over snow travel on 1/22. Please stay on trail to prevent resource damage
Primrose Trail
Open
Open to over snow travel on 1/22. Please stay on trail to prevent resource damage.
Resurrection Pass Trail
Open
Open for the 2019/2020 winter season.
Snug Harbor
Open
South Fork Snow River Corridor
Closed
Closed due to thin snow coverage.
Summit Lake
Open

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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.