The avalanche danger is MODERATE above 1000′. Moderate winds and a steady trickle of snow over the past two days will make it possible for a person to trigger a wind slab avalanche up to a foot deep. This new snow is falling on a snowpack with two different layers of buried surface hoar in the upper 2′ of the snowpack, which means it will also be possible for a person to trigger a larger avalanche. Be careful with terrain selection today, especially in parts of the advisory area that have seen the heaviest snowfall since Wednesday. The danger is LOW below 1000′.
Special Announcements
Join us TOMORROW for the Turnagain Pass Avalanche Awareness Day on Saturday, March 19th in the Seattle Ridge parking lot. Chat with CNFAIC forecasters, try out some avalanche rescue gear, and demo a snowmachine or two from local businesses such as AMDS and Anchorage Yamaha and Polaris.
Fri, March 18th, 2022
Alpine
Above 2,500'
2 - Moderate
Treeline
1,000'-2,500'
2 - Moderate
Below Treeline
Below 1,000'
1 - Low
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
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.
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
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.
Light snowfall and moderate winds are expected to continue today. Although this storm hasn’t exactly packed a serious punch, there is enough snow being blown around to start to make avalanches big enough to bury a person. Sensitive wind slabs will be most likely found at upper elevations near ridgelines, steep gullies, and convex rolls. They should give some warning signs like the shooting cracks we saw on Tincan Ridge yesterday.
These avalanches will be the most dangerous in the areas that have picked up the most snow over the past two days. In the upper elevations, the mountains around Girdwood have seen 6-10″ since Wednesday, with Turnagain Pass receiving 4-6″ and Portage and Placer likely approaching a foot of snow with more on the way. This snow has fallen on crusts and surface hoar in some places, making it a bit more reactive than usual. These older surfaces will also make loose snow avalanches likely in steep terrain.
Shooting cracks- like this one from Tincan yesterday- are a warning sign that the snowpack has all the ingredients needed to make an avalanche. Be on the lookout for similar clues today. 03.17.2022
Avalanche Problem 2
Persistent Slabs
Certain
Very Likely
Likely
Possible
Unlikely
Likelihood
Historic (D4-5)
Very Large (D3)
Large (D2)
Small (D1)
Size
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.
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.
The layer of buried surface hoar from early this month is a bit more challenging to manage than the avalanches associated with the new snow. John and I visited the same area on two consecutive days and got mixed results on this layer in our stability pits. In some places we found an obvious layer of buried surface hoar 1-2′ deep that was failing in stability tests, while in other places it was hard to find in the pits and wasn’t doing much in stability tests (details here and here). As far as we know, the last human-triggered avalanche on this weak layer was on Saturday, which hopefully is telling us that it is gaining strength. As the snowpack continues to get loaded by new and wind-transported snow, the layer is slowly experiencing more stress, nudging it just a little closer to its breaking point. With modest snow totals and light to moderate winds it is unlikely that we will see natural avalanches on this layer today, but it is possible that a person could trigger an avalanche on it.
There is a significant level of uncertainty with this layer, which should be good enough reason to be careful with your terrain choices. If you want to avoid the problem entirely, you can just avoid steep slopes. If you are trying to get into steeper terrain, be smart about it. Avoid steep slopes with high-consequence terrain traps like cliffs, rocks, trees, or gullies. As always, only expose one person at a time to steep terrain, and watch your partners from safe spots.
Poor stability test result (ECTP26) on the layer of surface hoar that was buried back on 3/2. This photo was taken on Tincan Ridge on a north aspect at 3200′, but we got similar results on a southerly aspect at 2300′ just a little earlier in the day. 03.17.2022
The layer that is giving us cause for concern. This sample was taken from a slope where we saw shooting cracks and small chunks of wind-loaded snow breaking on these surface hoar crystals. 03.17.2022
Click Here if our field video from yesterday doesn’t load in your browser.
Weather
Fri, March 18th, 2022
Yesterday: We saw mostly cloudy skies, with a little bit of sun filtering through the clouds at times. Light snowfall brought a trace to 4″ new snow through the area, with the heaviest snowfall near Portage and Placer, and hardly anything at Turnagain Pass. Winds were out of the east at 10-15 mph with gusts of 15-30 mph. The rain line started around 1000′ but dropped to sea level later in the day and overnight. Daytime high temperatures were in the upper 20’s to low 30’s F, with overnight lows in the mid 20’s F.
Today: Today is looking similar to the past two days, with mostly cloudy skies and light snowfall. Most of the advisory area will likely only see a trace to 2″ of snow, but Portage and Placer may see more like 3-6″ during the day. Winds will be out of the east to northeast at 10-15 mph with gusts of 15-25 mph. High temperatures are expcted to be in the mid 20’s to upper 30’s F.
Tomorrow: It is looking like the light snow will continue tonight, with a trace to 2″ in Girdwood, 2-4″ at Turnagain Pass, and 3-6″ in Portage and Placer. Winds are expected to pick up overnight, blowing 15-30 mph out of the northeast before calming down during the day tomorrow. Lows should be between 20 and 30 F, with daytime highs back in the upper 20’s to upper 30’s F. Cloud cover is expected to break up just a little tomorrow, with some periods of sun poking through the clouds during the day.
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.
Archives 
The Bottom Line
Special Announcements
