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ARCHIVED - Forecasts expire after 24 hours.
Issued
Tue, March 5th, 2024 - 7:00AM
Expires
Wed, March 6th, 2024 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger is MODERATE above 1000’. Strong winds are expected to accompany 3 to 8” new snow by this afternoon, increasing the chances of triggering wind slab avalanches up to a foot deep by the end of the day. Be aware of increasing avalanche danger today through tonight as this round of wind and snow unfolds, especially in the upper elevations. The avalanche danger is expected to remain LOW below 1000’.

PORTAGE/PLACER: These coastal zones are expected to end up on the high end of the storm totals as usual, with around a foot of new snow possible by tomorrow morning. Look for increasing avalanche danger on all slopes, even those that are protected from the wind, as the storm snow starts to accumulate.

SUMMIT/JOHNSON PASS: The snowpack in the central Kenai is weaker and more concerning than the rest of our forecast zones. There is still a good chance a person could trigger a bigger avalanche on weak snow buried in the upper 2 feet of the snowpack, and a more cautious mindset is recommended in these areas.

Special Announcements

Turnagain Takeover Avalanche Awareness Day – Mark your calendars for our annual Turnagain Takeover day on Saturday March 23, 2024. Come grab a hot dog or burger and meet the forecast team to chat about current conditions or bring your burning questions about snow and avalanches. Local dealers will have demo sleds to ride and there will be stations to practice your avalanche rescue skills.

Tue, March 5th, 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
Wed, March 6th, 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
Wed, March 6th, 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
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

A snowboarder triggered a small wind slab avalanche in the Summit Lake area on the north side of Manitoba yesterday. The avalanche was about 8″ deep and 50′ wide, and the snowboarder was able to ride away from the slope without being caught. More info in this observation.

 

Looking down from the top of a small snowboard-triggered avalanche on the north side of Manitoba yesterday. Photo shared anonymously, 03.04.2024.

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

A weak system is expected to bring a quick round of snow tonight and tomorrow, with strong easterly winds expected to arrive with the snow. Most of the advisory area should see around 2-3″ snow during the day, with another 2-3″ possible tonight. As usual, this storm is expected to favor the coastal areas near Portage and Placer, with 6-8″ possible today and another 4-6″ tonight. We’re expecting a slight increase in winds, with easterly winds blowing 15 to 30 mph and gusts of 20 to 40 mph. With this active weather, the chances of triggering a fresh wind slab avalanche up to a foot deep will increase through the day.

Watch for unstable conditions on slopes that are getting actively loaded today. The most common areas to find reactive wind slabs will be in steep terrain just below ridgelines, convex rolls, and in gullies. Be skeptical of slopes with relatively stiffer snow sitting on top of a softer layer. These fresh wind slabs don’t necessarily need to be very stiff to make avalanches; any snow that has been drifted into a deeper slab will be suspect. Warning signs like shooting cracks and collapsing are clear indicators of unstable snow. Travel tests can be a very effective way to assess how sensitive theses surface problems are. This includes things like quick hand pits to see how easily the new snow is shearing off the surface, and traversing the top of short but steep test slopes to see if you can make a mini avalanche happen. Your best bet for staying out of trouble – and finding the best surface conditions – is to look for slopes that are protected from the wind today.

Dry Loose Avalanches (Sluffs) remain likely in steep terrain with loose snow on the surface. While it is unlikely these will be big enough to bury a person, they can be dangerous if you get carried through terrain traps like trees and cliffs, or into gullies that can collect debris into deeper piles.

Predicted 24-hour storm totals today through tonight. Graphic courtesy of NWS Anchorage, 03.05.2024.

 

Weather
Tue, March 5th, 2024

Yesterday: Clouds built through the day, with light snowfall beginning in the afternoon. Most of the advisory area received a trace of snow to sea level, while the coastal zones near Portage and Seward received 2-5” snow. Winds were out of the east at 5 to 15 mph with gusts of 10 to 25 mph. High temperatures were in the mid teens to upper 20s F with lows in the mid teens to low 20s F.

Today: A weak system moving through the Gulf will bring light snowfall with increased easterly winds today through tonight. Most of our forecast area should see 2-3” snow during the day and another 2-3” tonight. As usual, more precipitation is expected near Portage and Placer, which could see 6-8” snow during the day and another 4-6” tonight. Snow line is expected to stay below 100’ for the storm, with high temperatures in the mid 20s to low 30s F and lows in the low to mid 20s F. Winds will be out of the east to northeast at 15 to 30 mph with gusts of 20 to 40 mph.

Tomorrow: Snowfall is expected to taper off by tomorrow morning, with winds switching to the north at around 5 mph with gusts around 10 mph. Skies should remain mostly cloudy, but clouds are expected to slowly break up through the day. High temperatures should be in the mid 20s to low 30s F with lows in the mid teens to low 20s F.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 21 0 0 87
Summit Lake (1400′) 22 0 0 45
Alyeska Mid (1700′) 22 1 tr 90
Bear Valley – Portage (132′) 30 2 0.22 –
Grouse Ck (700′) 26 0 0 65

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 14 ENE 10 24
Seattle Ridge (2400′) 17 SE 11 20
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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.
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