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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, March 23rd, 2024 - 7:00AM
Expires
Sun, March 24th, 2024 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger is MODERATE above 1000′. A frontal system is expected to head our way today, bringing strong easterly winds and light precipitation later in the day. Be on the lookout for fresh wind slabs forming at upper elevations, and expect to find increasing danger if the snow and rain arrives sooner than expected. Keep in mind, there are some weak layers lurking in the upper 2-3′ of the snowpack that may produce larger avalanches. The danger is LOW below 1000′, where surfaces are locked up with stout crusts. The avalanche danger could rise if these crusts start to break down during the day.

 

LOST LAKE/SEWARD: The storm is expected to arrive at these southern areas first, bringing 2 to 4″ snow at upper elevations and rain below 1500′ today with more on the way tonight. Look for increasing avalanche danger as the storm arrives, with wind slab avalanches becoming more likely later in the day.

Special Announcements

TODAY!!  Turnagain Pass Avalanche Awareness Day – March 23
Swing by the Turnagain motorized parking lot between noon and 4pm to grab a hotdog, practice your beacons skills, chat with the forecast team, and possibly test out a demo snowmachine provided by local dealers. We may not have the sunshine that we’ve had the past few days, but we’ll still be having a good time up there so swing on by!

Arctic Valley SkiMo Race with Alaska Avalanche School – Sunday, March 24
Dust off your best costume and come join Alaska Avalanche School for their 9th annual SkiMo race fundraiser at Arctic Valley. This is a super fun and family friendly event that is available to racers of all skill levels, with long and short format race courses. Follow the link for more information!

Sat, March 23rd, 2024
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
Sun, March 24th, 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
Sun, March 24th, 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 avalanches reported yesterday were two new glide avalanches seen in the Summit area on Fresno and Gilpatrick. There was also a chunk of a glide avalanche that released on Eddie’s Ridge on Thursday afternoon.

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

Active weather returns to the area today, with wind being the main player for most of the day before the precipitation picks up later this afternoon. Wind slab avalanches will become more likely as the winds increase, but the size will be limited by the amount of soft snow available to be blown into fresh slabs. They will most likely be around 6 to 12″ deep, and may be a bit more reactive than usual since they will be forming on top of slick crusts and possibly surface hoar on some slopes. The most likely places to find unstable conditions will be up on higher elevation slopes just below ridgelines, convex rolls, and steep gullies. You can stay out of trouble by avoiding these terrain features, and watching out for warning signs like shooting cracks, collapsing, or active wind loading.

Wet Loose Avalanches: If we get surprised by the weather and either see some sunshine or get more rain than expected, we will likely see some wet loose activity this afternoon. Look out for rollerballs releasing as snow surfaces melt and soften, and be aware of overhead hazard if you start to notice surface crusts breaking down. This is unlikely to happen today, but the weather is always full of surprises.

Glide Avalanches: It seems the glide avalanche problem is slowly starting to reawaken in the area. We have seen glide cracks opening up throughout the advisory area, and have seen a handful of glide avalanches release over the past few days. This includes two glide avalanches in the Summit Lake area yesterday (Gilpatrick and Fresno), and one in Turnagain Pass on Thursday (Eddie’s Ridge). This type of avalanche releases without warning, so be sure to avoid spending any time below open glide cracks.

If you’re feeling uninspired by the current surface conditions but still want to get outside today, come up to the Seattle Ridge motorized parking lot and say hi! We’ll be up there from noon to 4 pm, grilling up burgers and dogs, running some beacon practice drills, and hanging out with our friends from AMDS and Anchorage Yamaha and Polaris. More details here, hopefully we’ll see you up there!

The scene from a previous Turnagain Pass Avalanche Awareness Day. Always a good time!

Avalanche Problem 2
  • Persistent Slabs
    Persistent Slabs
  • Aspect/Elevation
  • 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.

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

We are still paying close attention the layer of weak snow that was buried two weeks ago, which produced a widespread avalanche cycle during the week following the storm and is still showing concerning signs in snow pits at Turnagain Pass. This is a combination of buried surface hoar and near-surface facets, which is sitting on top of an older melt-freeze crust on solar aspects. The layer is slowly becoming more stubborn and difficult to trigger but a person may still be able to trigger a large avalanche failing on this weak snow, now around 2 feet deep on average.

These layers are difficult to assess, since the are unlikely to give you clear warning signs even when conditions are dangerous. The only way to get a better idea of how the layer is behaving where you are traveling is to take the time to dig a pit and assess. If you are getting unstable test results, it is best to dial back your terrain objectives.  Over the past few days, we’ve gotten poor test results on Magnum, Sunburst, and Tincan Proper, with less concerning results on Seattle Ridge. These layers can be tricky to evaluate, so now is a good time to keep terrain objectives modest and be very careful with safe travel protocol like traveling one at a time in steep terrain and watching partners from safe spots outside of avalanche runout zones.

Sample of the buried surface hoar layer from a snowpit at 2500′ on Magnum Ridge. Photo: Aubrey Palmer, 03.22.2024.

Weather
Sat, March 23rd, 2024

Yesterday: Cloud cover was variable yesterday, with some areas seeing mostly sunny skies for some parts of the day and others staying in the clouds for most of the day. Winds were averaging 5 to 15 mph out of the east with gusts of 20 to 30 mph. High temperatures were in the upper 20s F at ridgetops and got up to the low 40s F at lower elevations. We did not receive any precipitation.

Today: A frontal system is expected to move into the area today, bringing stronger winds and light precipitation. Ridgetop winds will likely increase during the day, averaging 15 to 35 mph with gusts of 25 to 45 mph out of the east. Precipitation should start later in the day, with only a trace expected before sunset and more on the way tonight through tomorrow. Rain line may make it up to around 1200’ this afternoon, dropping down to around 600’ overnight. Skies should be partly to mostly cloudy, with high temperatures in the low to mid 30s F and lows in the upper 20s to 30 F.

Tomorrow: Stormy weather continues tomorrow, with 3 to 6” new snow expected for Turnagain Pass and Girdwood, and up to a foot at higher elevations closer to the coast. Rain line should drop down to around 600’ tonight, but creep back up to around 1100’ before the precipitation tapers off tomorrow. Winds are expected to remain strong out of the east at 20 to 25 mph, with gusts of 30 to 35 mph. High temperatures should be in the low to mid 30s F with lows in the upper 20s to low 30s F.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 33 0 0 97
Summit Lake (1400′) 35 0 0 44
Alyeska Mid (1700′) 35 0 0 99
Bear Valley – Portage (132′) 38 0 0
Grouse Ck (700′) 37 0 0 69

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 25 E 10 30
Seattle Ridge (2400′) 27 ESE 10 17
Observations
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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.