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ARCHIVED - Forecasts expire after 24 hours.
Issued
Tue, January 25th, 2022 - 7:00AM
Expires
Wed, January 26th, 2022 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

There is a CONSIDERABLE avalanche danger on all aspects above 1,000′. After yesterday’s storm, we can expect humans to be able to trigger wind slabs, storm slabs, and cornice falls. Wind slabs could be 1-3+’ thick and storm slabs will depend on the depth of the new snow. Cornices have grown and deserve an extra wide berth. It’s a day to watch for red flags, be cautious with our route-finding, and be conservative with our decision making.

LOST LAKE/SEWARD:  Dangerous avalanche conditions remain. Several natural avalanches were seen yesterday due to heavy snowfall and strong wind rapidly loading slopes. Today, the storm has died down, but human triggered large avalanches are still likely.

Special Announcements
  • AK DOT&PF:  There will be intermittent traffic delays today, January 25, 2022 on the Seward Highway and Portage Glacier Highway for Avalanche Hazard Reduction work. Motorists should expect delays of up to 45 minutes between 10:00 AM and 3:00 PM from mileposts 100 to 96.5 north of Girdwood, from milepost 88 to 83 on the Seward Highway, south of Girdwood, and near milepost 5 and Bear Valley on the Portage Glacier Highway. Updates posted on 511.alaska.gov.
Tue, January 25th, 2022
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
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

Although the visibility was somewhat poor, we did have reports of a handful of natural avalanches seen around the region yesterday. On our field day at Tincan, there was a quick shot of sun, giving us confirmation of the high degree of wind effect. Many ridges and sub-ridges were scoured and others loaded. We saw what appeared to be several wind slab avalanches that had been partially covered back in by the winds. These were along ridgelines, but also mid-slope and in cross-loaded gullies. Some of these were likely triggered by pieces of cornice falling off. One of those is pictured below.

 

Natural cornice fall and wind slab avalanche from the new snow and winds early yesterday morning. Photo by Aleph Johnston-Bloom 1.24.22.

Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    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

A brief break in stormy weather is slated for today as ridgetop winds are turning westerly, temperatures are cooling, and there is even a chance for some clearing skies. The storm that hit Sunday evening and lasted through yesterday morning has moved off. There was significant variability in storm snow totals, but the winds howled everywhere. Sunburst saw gusts to 96mph at 8am yesterday morning, for example.

Storm totals for mid to upper elevations since Sunday:
Turnagain Pass:  8-10″ snow (.5 – .7″ SWE)
Girdwood/Portage Valleys:  16 – 24″ snow (1.5 – 2″ SWE)
Summit lake:  3-5″ snow (.3″ SWE)

Today we are within the 24-48 hour period after the storm ended and that means we need to have a conservative mind-set and be on the lookout for the different ‘storm snow instabilities’ at the mid and upper elevations. These are: wind slabs, storm slabs, and cornice falls. The size of avalanches will be dependent upon how much snow has fallen. Paying attention to red flags is critical. These are recent avalanches, cracking in the snow around you and collapsing in the snowpack (whumpfing). At the lower elevations (below 1,000′) where rain fell, we can expect the wet snow to start freezing, which will limit avalanche issues.

Wind Slabs:  Most of the Alpine has been significantly affected by the strong winds. Wind slabs are likely to be lurking on most slopes. They could be near ridgelines, mid-slope on rollovers and as seen above, in cross-loaded gullies. Slabs could be anywhere from 1-3+’ deep and likely easy to trigger.

Storm Slabs:  Any slope with more than 8-10″ new snow should be suspect of avalanching simply due to the rapid loading of snow just over a day ago. This would be predominantly in the Girdwood Valley and Placer Valley areas with close to 2 feet of new snow near and above treeline.

Cornices:  From our quick peek yesterday, cornices have grown and been re-shaped. These could be teetering on the balance and just need a person to tip that balance. Give them an extra wide berth, they could break further back than expected.

Cracking in the snow between skiers yesterday at the top of the Tincan Trees. This is a shallow wind slab on relatively flat ground. 1.24.22.

 

 

Avalanches breaking in old snow deeper in the pack?
We are continuing to watch the buried New Year’s crust and how this latest storm impacted that, or any other layer, deeper in the snowpack. With only a brief look at a small area yesterday, there are still a lot of unknowns as to any avalanche activity that may have stepped down to a buried weak layer. The conservative choice right now is to be suspect of steep upper elevation slopes where a wind slab or cornice fall could step down and create a much larger avalanche. This issue seems to be most pronounced on slopes with a thinner snowpack such as exposed peaks and ridges that see a lot wind, as well as in areas such as the west side of the Girdwood Valley (toward Crow Pass) and south end of Turnagain Pass to Summit Lake.

Weather
Tue, January 25th, 2022

Yesterday:  Mostly cloudy skies with areas of clearing around Turnagain Pass. Light precipitation fell off and on through the day as the storm exited the region (adding 1-2″ in most areas). The rain snow line was roughly between 600-800′ with wet snow at 1,000′. The easterly ridgetop winds were very strong till 10am (60’s, gusting 90’s mph) when they decreased into the 20’s with gusts in the 40’s mph.

Today:  A break between storms is expected today with a chance for some clearing skies. Ridgetop winds will turn westerly (5-15mph) and usher in colder air (teens F). There could be some instability showers pop up and add another 1-2″ here and there.

Tomorrow:  Beginning Wednesday, another system will start to push in that looks to peak on Thursday. Tomorrow, light snowfall, moderate easterly ridgetop winds and warming temperatures are forecast. Heavier snowfall with a rising rain/snow line is expected Thursday into Friday.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 32 1 0.1 84
Summit Lake (1400′) 30 1 0.1 31
Alyeska Mid (1700′) 32 4 0.4 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 23 NE 33 97
Seattle Ridge (2400′) 27 SE 14 41
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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.