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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, March 24th, 2024 - 7:00AM
Expires
Mon, March 25th, 2024 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger is MODERATE at all elevations, and there is a variety of concerns. Strong easterly winds are expected to continue to form reactive wind slabs up to a foot deep above treeline, and we are still concerned with the smaller chance of triggering a bigger avalanche up to 2 to 3′ deep on a buried layer of weaker snow. Terrain at and below treeline saw little or no refreeze in the past 24 hours and is expected to see rain on snow today, which makes wet snow avalanches another concern.

Roof Avalanches: Several roof avalanches were observed yesterday, and with continued warm and rainy weather on the way today there may be more on the way. Pay close attention to children and pets playing outside, be mindful of where you park vehicles, and keep an eye on overhead hazard as you enter and exit buildings.

PORTAGE/PLACER: These areas may see up to a foot or more of new snow by the end of the day, with heavy rain below 1400′. The chances for natural avalanches will increase as the storm picks up, and we may see very dangerous avalanche conditions in these zones by the end of the day. 

Special Announcements

TODAY! 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!

Sun, March 24th, 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 25th, 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 25th, 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
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

There were no new avalanches observed in the advisory area yesterday. The last reported avalanches were two glide avalanches seen in the Summit Lake area on Friday, and one small glide avalanche on Eddie’s Ridge on Thursday.

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

The weather today is looking similar to what we saw yesterday, and the avalanche problems are following the same pattern. Strong easterly winds are expected to slowly taper down today, but should still average up to 20 to 40 mph with gusts up to 50 to 70 mph. We may see up to 3 to 5″ new snow along with these winds, which will increase the potential size of avalanches. Even if we don’t get any new snow today, there is still cold dry snow on the surface at upper elevations that will provide material to build fresh wind slabs.

Watch out for unstable snow in the common suspect terrain features today. This includes steep slopes near ridgelines, steep gullies, and convex rolls. Pay close attention to red flags like shooting cracks or collapsing as clear signs of unstable snow. You can quickly assess this problem as you travel by poking into the snow and looking for stiff or ‘punchy’ snow on the surface.

Wet Loose Avalanches: Lower elevations did not see a refreeze last night, and are expected to see some rain today. This will increase the chances of natural and human-triggered wet loose avalanches on steeper slopes. These may not be huge, but they can be very dangerous if they push you into terrain traps like trees, cliffs, or creeks.

Predicted 24-hour snow totals for the area through tomorrow morning. Graphic courtesy of NWS Anchorage, 03.24.2024

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

The weak layer of facets and surface hoar that was buried two weeks ago still has the potential to produce big avalanches today. This is slowly becoming more and more stubborn, but has shown cause for concern in several snowpits this week. These persistent weak layers are tricky to assess, since they can sometimes make avalanches even when you don’t see any of the classic warning signs like cracking or collapsing. Unfortuantely, from what we have been seeing, it seems like this weak interface is most concerning right in the middle of our advisory area on Turnagain Pass. We are not expecting widespread avalanche activity on this layer, but you may still be able to trigger a large avalanche today. Keep this layer in mind when you are planning your day, and consider avoiding bigger and more consequential terrain. With higher uncertainty associated with stubborn weak layers like this, we like to increase our margins of safety by dialing back the terrain a bit. As always, be sure you are only exposing one person at a time to avalanche terrain and watch your partners from safe areas outside of avalanche runout zones.

Thanks to everyone who came out yesterday for the 2024 Turnagain Takeover! 

Weather
Sun, March 24th, 2024

Yesterday: We saw a day of warm, gray, and windy weather yesterday, with light precipitation overnight. Stations are showing a trace to 2” new snow above 1200’, with 0.2-0.4” rain at lower elevations. Skies were mostly cloudy with some pockets of blue skies later in the day. Winds were strong out of the east at 15 to 40 mph with gusts of 50 to 70 mph. High temperatures were in the mid 30s to upper 40s F, and lows remained above freezing at lower elevations and in the mid 20s near ridgetops.

Today: Today is looking similar to yesterday, with a bit more precipitation likely. We may see a trace to 3” snow at upper elevations, with the rain line moving up from 800 to 1100’ in Girdwood and Turnagain Pass, and up to around 1400’ closer to the coast. These coastal areas like Portage and Placer could see closer to 10 to 15” snow at upper elevations during the day. Winds are expected to remain strong out of the east at 20 to 40 mph with gusts of 50 to 70 mph. Skies should be partly to mostly cloudy.

Tomorrow: It is looking like the easterly winds should start backing off tonight, with average speeds of around 10 mph and gusts up to 30 to 40 mph during the day tomorrow. Light precipitation is still expected to trickle in, with 1 to 3” new snow possible and the rain line creeping back up to up to around 1400 to 1600’. Skies should be mostly cloudy with high temperatures in the mid 30s F and 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′) 36 0 0 96
Summit Lake (1400′) 39 0 0 43
Alyeska Mid (1700′) 35 3 0.16 98
Bear Valley – Portage (132′) 40 rain 0.49
Grouse Ck (700′) 39 0 0.2 67

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 25 ENE 26 69
Seattle Ridge (2400′) 28 SE 15 32
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.