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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, March 10th, 2024 - 7:00AM
Expires
Mon, March 11th, 2024 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger is MODERATE at all elevations. 2-4″ new snow with light easterly winds will form small but sensitive slabs on wind loaded slopes. This round of snow is falling on a mix of crusts, facets, and surface hoar, so it is not expected to bond well. Be on the lookout for touchy wind slabs on any slopes that have been recently loaded, and expect to see dry loose avalanches on all slopes with soft snow on the surface today.

PORTAGE/PLACER: These zones are once again expected to be favored during the stormy weather today and tomorrow. In addition to the wind slab concerns, we’ll also be on the lookout for storm slab avalanches on sheltered terrain 6-8” deep. The extra snow in these zones warrants a bit more caution than in the rest of the advisory area.

SUMMIT/JOHNSON PASS: The snowpack in the central Kenai mtns is weaker than at Turnagain Pass. Check out the Weekend Outlooks for Summit Pass and Seward for more information.

Special Announcements

It is with a heavy heart that we share the loss of two avalanche professionals from the Pacific Northwest this week. Nick Burks, who was a forecaster for the Wallowa Avalanche Center died in an avalanche accident while skiing with a friend on Wednesday, March 6. Matt Primomo, who was an avalanche forecaster for the Northwest Avalanche Center, died in a non-avalanche related accident on Thursday, March 7. Our thoughts are with our friends down south – their friends, families, and to the communities which these people were such a major part of.

Sun, March 10th, 2024
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
Mon, March 11th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
Mon, March 11th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
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

The only new avalanche activity observed yesterday was widespread dry loose avalanches (sluffs) in steep terrain. We did see a few more bigger avalanches from last week’s storm, which is keeping us paying close attention to the weak layer buried on 3/5.

Wide-propagating avalanche on the north-facing side of Tincan’s CFR, to the looker’s right of Todd’s run. Avalanche likely from 3.5 or 3.6, photo from 03.09.2024.

Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Aspect/Elevation
  • 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.

Aspect/Elevation of the Avalanche Problem
Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.

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

After a few days of surprisingly sunny weather, we’re in the midst of a pattern change. Last night we received 1-4″ low-density snow, and we’re expecting another 1-3″ this morning before we see a brief break in the weather later in the day. The winds have stayed fairly light at around 10-15 mph and are expected to calm during the day. However, since that new snow is so light and fluffy, it won’t take much wind to blow it into thicker and more reactive slabs. This fresh round of wind slabs is forming on a variety of really weak surfaces including surface hoar, facets, and crusts, and we’re expecting it to be quite reactive today.

Expect to find small but touchy wind slabs at upper elevations today. These may not be huge, but they will probably be easy to trigger. With the amount of dry loose avalanches we’ve seen in the second half of the past week, we’re expecting relatively small avalanches to entrain a large amount of snow as they travel down slope. Conditions will be generally safer on terrain that is protected from the wind, and the skiing and riding should be better on these slopes as well.

Dry Loose Avalanches (Sluffs) should be expected on all steep slopes at all elevations today. We have been seeing a lot of activity this week, and are expecting more of the same with another round of light fluffy snow on the surface. These can be dangerous if they knock you off your feet or carry you through terrain traps like cliffs, rocks, trees, or depressions where debris will pile up deeper.

We saw this fresh round of surface hoar  from the parking lot to the ridgetop at Sunburst yesterday, and we also saw it on Seattle Ridge on Friday. 03.09.2024

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

Wenesday’s storm produced widespread activity throughout the advisory area, including many avalanches that propagated much wider than we would expect to see from a typical storm slab avalanche. We know this storm buried a layer of weak, faceted snow on top of firm surfaces, and we’re keeping a close eye on this weak layer. We’re not expecting the few inches of snow from last night and this morning to really tip the scales for this layer today, but it is something to keep in mind that has the potential to make bigger avalanches, and it will become more concerning as the snow slowly continues to accumulate over the next few days.

 

Weather
Sun, March 10th, 2024

Yesterday: Skies were surprisingly sunny yesterday for broad parts of the advisory area, with clouds slowly building through the day. Winds were light out of the west with high temperatures in the mid 20s to mid 30s F and lows in the single digits to mid teens F. The weather changed overnight, and we’ve received 1 to 4” new snow equaling 0.1-0.4” SWE along with easterly winds at around 10 mph with gusts of 15 to 25 mph.

Today: We should see another 1-3” snow this morning before we see a break in the weather this afternoon. Winds are expected to remain light out of the east, with average speeds of 5 to 15 mph and gusts of 20-25 mph, calming through the day. Skies are expected to be mostly cloudy, but depending on what model you’re looking at and how optimistic you are feeling, we may see some sun poking through the clouds later in the day. High temperatures are expected to be in the mid to upper 20s F with lows in the mid teens F.

Tomorrow: We are expecting another round of light snow tomorrow, with another 2 to 4” possible during the day and snow to sea level. Winds should remain light out of the east at 5 to 10 mph with gusts around 15 mph. High temperatures should be in the mid 20s F  with lows in the mid teens to 20 F.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 18 3 0.1 93
Summit Lake (1400′) 15 0 0 45
Alyeska Mid (1700′) 21 4 0.16 97
Bear Valley – Portage (132′) 17 5 0.4
Grouse Ck (700′) 21 tr 0.1 64

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 14 W-ENE 6 26
Seattle Ridge (2400′) 17 N 2 6
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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.