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Sun, February 13th, 2022 - 7:00AM
Mon, February 14th, 2022 - 7:00AM
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger is MODERATE above 2500′, where it will be possible to trigger a wind slab avalanche up to a foot deep. Moderate winds this morning will be able to build sensitive slabs with the low-density snow at the surface before calming down early in the day. The most dangerous terrain features will be near ridgelines, on convex rolls, and in steep gullies. The danger is LOW below 2500′, where the main concern will be dry loose avalanches in steep terrain.

SUMMIT LAKE: The snowpack is thinner in the Summit Lake area, and there are weak layers deeper in the snowpack that make it possible for a person to trigger a large avalanche. Extra caution is warranted in the Summit Lake area, and steep slopes should be approached with caution. This is the type of snowpack that might not give any warning signs before producing a large avalanche.

Sun, February 13th, 2022
Above 2,500'
2 - Moderate
Avalanche risk
1 - Low
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Recent Avalanches

Portage/Placer: Skiers triggered two small but wide-propagating avalanches, suspected to be on a weak layer of surface hoar and stellars buried 1-1.5′ deep. They also saw a natural avalanche that they thought had stepped down to the same weak layer on Byron (photo below).

 Natural avalanche on Byron that looks to be a wind slab that stepped down to another layer, suspected to be a combination of surface hoar and stellar dendrites. Photo: Mike Welch, 02.12.2022.

Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Certain
    Very Likely
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
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

Wind slabs are once again the primary concern today, as moderate southwest to southeasterly winds overnight and early this morning will build a fresh round of small but reactive wind slabs with the low-density snow that was on the surface yesterday. The key terrain features to watch out for will be steep slopes near ridgelines, convex rollovers, and steep gullies. Because the soft snow on the surface is so light, it won’t take much wind to move it around. This was the case yesterday in the Summit Lake area, where we noticed snow blowing off some ridgelines with weather stations only registering winds at 5-10 mph. Luckily this problem is relatively easy to identify and thus avoid. Be on the lookout for stiffer snow on the surface, and pay attention to warning signs like shooting cracks, collapsing, and fresh avalanche activity. This will require taking a few seconds to hop off your machine or step off the skin track and poke around in the snow to see how it feels. If you are trying to get on steeper terrain, be sure to follow safe travel protocols. This includes only putting one person at a time on steep slopes and watching your partners from safe spots out of the way of avalanche hazard.

We might see a slight increase in winds late this afternoon, especially at the higher elevations. Pay attention to changing conditions, with the potential for more sensitive wind slabs developing if the winds do pick up even a little bit. Keep an eye out for blowing snow along ridgelines as well as the red flags mentioned above.

Cornices: Strong winds over the past week have created very large cornices. Skiers reported natural avalanche activity triggered by a cornice fall up Virgin Creek earlier in the week (details here), and we have seen debris from cornice falls throughout the area. Be sure to give cornices plenty of space if you are travelling along ridgelines, and limit the time you spend below them.

Loose Dry Avalanches: Sluffs will run fast on steep terrain with soft snow sitting on top of firm surfaces left from last week’s strong winds. These are unlikely to bury a person, but can be dangerous if they were to carry you over consequential terrain like rocks, cliffs, or trees.

Debris from natural dry loose avalanches on the north side of Cornbiscuit. Human-triggered sluffs will be likely today in steep terrain that has not been hit by winds. Photo: Andy Moderow. 02.12.2022

Debris from an avalanche triggered by a natural cornice fall up Virgin Creek earlier in the week. Photo: Peter Ostroski. 02.11.2022

Additional Concern
  • Persistent Slabs
    Persistent Slabs
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.
More info at Avalanche.org

For some time now we have been mentioning the potential for deeper avalanches failing on layers of facets surrounding crusts from New Year’s and all the way back to the Halloween storm. These layers are concerning in areas with a thinner snowpack, which are most likely found on the fringes of our advisory area (Lynx Creek, Silvertip Creek, Crow Pass area) and outside of the advisory are in Summit Lake. We saw natural and human-triggered avalanches failing on these layers during the strong wind event in the middle of last week (details here),  and have found concerning snow pit results over the past few days in the Crow Creek and Summit Lake areas. The same layers have not given any cause for concern recently in the rest of the Turnagain, Placer, and Girdwood areas. Keep this distribution in mind, especially if you are planning on getting out in the zones that have thinner and more problematic snowpack. Without a big loading event, these layers will be stubborn to trigger, but the potential is still there. This requires adjusting terrain accordingly, and avoiding steep and consequential slopes for the time.

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Sun, February 13th, 2022

Yesterday: High temperatures were in the mid 20’s to mid 30’s F under broken skies with some sun poking through periodically. Brief rounds of light snow brought a trace throughout the area, with light winds at 5-10 mph and gusts of 10-20 mph from the southwest during the day trending easterly later in the afternoon and overnight. Low temperatures were in the 20’s F.

Today: It is looking like another round of quiet weather is on tap for our area today, with light winds out of the south in the morning trending westerly later in the day. Sustained speeds are expected at 5-10 mph near ridgetops with gusts of 10-15 mph this morning backing off during the day and picking up again late in the afternoon and early this evening. Skies should be mostly cloudy with some sun making an appearance. Some periods of light snow may bring a trace of accumulation.

Tomorrow: Mostly clear skies overnight will allow temperatures to drop into the low teens, along with calm to light winds out of the west. Cloud cover increases during the day tomorrow, and chances for precipitation start to pick up late in the day. It is looking like the next round of precip will once again hit harder to the north of us, favoring the Hatcher Pass area, but we can expect to see around 3-5″ overnight Monday with snow to sea level. Daytime high temperatures will be in the 20’s F.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 31 0 0 90
Summit Lake (1400′) 25 0 0 38
Alyeska Mid (1700′) 32 tr tr 90

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 22 SW-E 8 25
Seattle Ridge (2400′) 25 SE 4 16
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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.