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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, January 19th, 2021 - 7:00AM
Expires
Wed, January 20th, 2021 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE today at elevations above 1000’, and large human-triggered avalanche are likely. Recent heavy snowfall, rain, and strong winds have created dangerous avalanche conditions. Cautious route finding will be important today, which means sticking to low-angle slopes and resisting the urge to move into big terrain as skies clear up.

The avalanche danger will be MODERATE for elevations below 1000’, where human-triggered avalanches will still be possible after mixed periods of rain and snow over the past 24 hours.

Summit Lake: Yesterday’s storm was one of the biggest 24-hr loading events in the Summit Lake area this season. With a thinner snowpack and multiple potential weak layers deeper in the snowpack, extra caution is warranted in this area.

Seward/Lost Lake/Snug: We have limited data on the snowpack in this area. If you do get out in the Central Kenai mountains, or around Seward, please share your observations here.

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Tue, January 19th, 2021
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
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
Considerable (3)
Below Treeline
Below 1,000'
Avalanche risk
Moderate (2)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Recent Avalanches

Seward Highway: There was debris from natural avalanches at the bottom of avalanche paths from Bird Flats to Portage and all the way down to Mile 21 near Moose Pass yesterday. Poor visibility yesterday made it impossible to tell what kind of natural activity had occurred near Girdwood or at Turnagain pass, but with skies clearing today we will surely see more recent natural avalanches.

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

The skies are clearing today, but make no mistake: we are still going to be faced with dangerous avalanche conditions as the snowpack adjusts to the major loading event over the MLK holiday weekend. Do not let the mild weather today lure you into a false sense of security. After receiving 1-3’ of snow in the past 24 hours, large human-triggered avalanches are likely today. Since 6 a.m. Friday, our new snow totals are as follows:

  • Center Ridge Snotel (1880’): 27” snow, equal to 3.9” snow water equivalent (SWE).
  • Alyeska Mid-Mountain (1700’): 31” snow, equal to 4.7” SWE. The base station recorded 3.4” water yesterday, which fell almost entirely as rain.
  • Summit Creek (1400’): 13” snow, equal to 1.4” SWE.

During days like these, people are more likely to find themselves getting into trouble with avalanche accidents and close calls. Although steeper slopes will look appealing under a fresh blanket of snow and with good visibility, conservative decision making will be imperative as the snowpack reacts to the recent heavy load. Be extra cautious with your terrain choices today, and pay attention to clear signs of instability like recent avalanches, shooting cracks, and collapsing. Until the snowpack has a little more time to adjust, we need to stick to lower angle terrain.

Cornices: Conditions have been perfect for building large cornices lately. If you find yourself traveling along ridgelines, be sure to give them plenty of space. It is also important to minimize travel below cornices, as they may release naturally and unexpectedly.

This was the scene at the motorized lot yesterday- 18″ on the ground at noon and heavy snowfall. 01.18.2021

This avalanche was triggered by a snowboarder under clear skies the day after a big storm in the end of December. The snowboarder was partially buried, but luckily was not injured. It is likely a human could trigger a similar avalanche today. 12.23.2020

 

Weather
Tue, January 19th, 2021

Yesterday: Intense precipitation starting early yesterday morning brought 2-3’ of snow at upper elevations, and over 2.5” of rain below 800’. The rain level snuck up to elevations around 1500’ periodically, with almost all snow above 1500’. Winds were 30-60 mph out of the east with gusts as high as 105 mph, but calmed down to 5-10 mph yesterday evening through last night. Temperatures were in the mid-20’s F at upper elevations, and in the mid-30’s F at low elevations.

Today: Mostly sunny skies and light winds are on tap today as an upper-level high pressure ridge passes over the area. Temperatures are expected in the upper 20’s to low 30’s F during the day, and will drop into the upper teens to low 20’s F tonight.

Tomorrow: There is a chance of light snow tonight, which may bring 1-3″. Cool temperatures should bring snow to sea level. Winds are expected to pick up tonight, blowing 25-30 mph out of the east at ridgetops with gusts to 35 mph. Skies are expected to be mostly cloudy during the day tomorrow, with another chance of light snowfall.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 31 20 2.7 144
Summit Lake (1400′) 33 12 1.3 105
Alyeska Mid (1700′) 32 25 2.9 126

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 23 NE 30 105
Seattle Ridge (2400′) 27 N/A* N/A N/A

*The Seattle Ridge anemometer is rimed over and not reporting.

Observations
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Riding Areas
Updated Fri, February 12th, 2021

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
No parking in turnaround at end of the road near the outhouse.
Placer River
Open
Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Skookum Drainage
Open
This area will close to machines on April 1 as per CNF Forest Plan. Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Turnagain Pass
Open
Twentymile
Open
Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Seward District
Carter Lake
Open
Lost Lake Trail
Open
Primrose Trail
Open
Resurrection Pass Trail
Closed
Closed for the 2020/21 winter season.
Snug Harbor
Open
South Fork Snow River Corridor
Open
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.