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ARCHIVED - Forecasts expire after 24 hours.
Issued
Mon, February 7th, 2022 - 7:00AM
Expires
Tue, February 8th, 2022 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is MODERATE on all aspects above 2,500′. Triggering a lingering wind slab in the 1-2′ deep range remains possible on slopes that were wind loaded from Saturday’s strong easterly winds. Cornice falls also remain possible to trigger along ridgelines.

The avalanche danger is generally LOW below 2,500′. Although triggering an avalanche is unlikely, there could be the off chance a smaller old wind slab could be triggered in open areas such as steep cross-loaded gullies.

*A quick-hitting storm is moving in this evening, exiting tomorrow. Avalanche danger is expected to rise tonight into tomorrow as strong east winds and 4-12″ of snow is forecast.

Mon, February 7th, 2022
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
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.
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • 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 current break in stormy weather should continue through most of today’s daylight hours. Partly cloudy skies with light and variable winds are forecast until around sunset when winds look to pick up from the east and light snow begins to fall. Until this next round of weather increases the avalanche danger, we should be on the lookout for older wind slabs that have not completely bonded from Saturday’s strong east winds. Most of these lingering slabs are likely to be in the Alpine zones, above 2,500′, and in the 1-2′ thick range. However, it’s still good to watch for any exposed area in the trees, or steep cross-loaded gullies below 2,500′ that may have a lingering slab or two.

For anyone headed out today, pay close attention to the snow surface and any visible clues of prior wind effect (scouring and/or loading). This might be more difficult in Girdwood Valley where a couple inches of light snow fell yesterday afternoon, obscuring older wind patterns. Be suspect of any wind loaded steeper slope. Feel for stiffer snow over softer snow and any cracking in the snow around you. Older wind slabs could be quite stubborn and show no signs of instability, but we still should be on our toes in case one does release.

On the south end of Turnagain Pass and toward Summit Lake, where the snowpack is thinner, older wind slabs could be sitting on weaker snow associated with buried crusts. We are still keeping track of these deeper layers despite the unlikely chance someone could trigger an avalanche that steps down to them. In this case, a much larger and dangerous avalanche could result, which is something to keep in mind if headed into the less traveled and larger terrain.

Cornices:  These have been growing steadily with the active weather pattern over the past couple weeks. Giving cornices an extra wide berth is always a good idea.

Glide cracks:  Say it isn’t so….glide cracks are opening… There are a few on the back side of Seattle Ridge and this one pictured below from the front side. Unfortunately, this glide crack is sitting above and just to the looker’s left of the common motorized up-track. As always, limit time under these cracks, they are completely unpredictable as to when and if they decide to release.

Glide crack on Seattle Ridge’s Repeat Offender slide path that overhangs the common motorized up-track. Photo Andy Moderow, 2.6.22.

 

Avalanche danger is slated to rise tonight into tomorrow with this next weather system. Ridgetop winds will be strong from the east and up to a foot of snow could fall in the high elevations of Girdwood/Portage Valleys and about half that in Turnagain Pass. Stay tuned!

Thank you to the NWS Anchorage Forecast Office for the above graphics.

Weather
Mon, February 7th, 2022

Yesterday:  Mostly cloudy skies were over the region with a few snow flurries in the afternoon. Girdwood and Portage Valleys picked up around 2″ of light snow and just a trace was seen on Turnagain Pass. Ridgetop winds were light from the west yet picked up overnight (10mph, gusts 20’s). Temperatures were mild, in the 20’sF at most locations.

Today:  Partly cloudy skies with some chances of sun breaking through are possible early today before the next weather system heads in this evening. Snowfall should begin sometime around 4-6pm and continue through tomorrow morning with 4-12″ of accumulation above 500′ (favoring Girdwood). Ridgetop winds are expected to be light from the east until picking up around 4pm and peaking tonight in the 30-40mph range with gusts near 60mph. Temperatures will also warm with this system into the mid 30’sF at Sea Level and the mid 20’s along ridgelines.

Tomorrow:  Snowfall and wind will tapper tomorrow morning with a brief break between storms occurring during the daylight hours. Ridgetop winds should be light from the south before picking back up from the east late tomorrow night. This next storm (Tuesday night into Wednesday) should bring more precipitation, up to a foot in the Alpine.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 25 tr tr 88
Summit Lake (1400′) 22 0 0 36
Alyeska Mid (1700′) 23 2 0.1 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 20 W 5 28
Seattle Ridge (2400′) 22 NE 2 5
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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.