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ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, March 6th, 2024 - 7:00AM
Expires
Thu, March 7th, 2024 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 2500′. Overnight 6-10″ of new snow fell with moderate east winds. This rapid addition of new snow and wind will make human triggered avalanches likely today. Wind slab avalanches could be 1-2′ deep at upper elevations. In areas with 6+” of new snow you could see avalanches even in wind sheltered areas.

Below 2500′ the avalanche danger is MODERATE. At lower elevations wind slabs are less likely but avalanches in sheltered areas within the new snow are still possible.

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 chat with the forecast team about current conditions. Local dealers will have demo sleds available and there will be stations to practice your avalanche rescue skills.

Wed, March 6th, 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
Thu, March 7th, 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
Thu, March 7th, 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

No new avalanches have been reported.

Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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 quick hitting storm moved through the area starting yesterday and increasing in intensity overnight, leaving 6-10″ of new snowfall across the forecast area. Winds were moderate during the storm with averages of 15-20 mph and gusts of 30-40 mph out of the east at upper elevations. Based on the weather station readings this morning it looks like Turnagain Pass, Girdwood, and Portage all received similar snowfall amounts, with about 0.5″ to 0.7″ of water which could range from 6-10″ of snow depending on elevation. Temperatures appear to have stayed just cold enough for snow to fall down to sea level overnight.

Yesterday’s new snow and wind will be the primary drivers of avalanche concerns today. In areas with 6+” of new snow it will be possible to trigger a storm slab avalanche at the interface with the old snow surface even in sheltered areas. The storm snow problem might be most prominent below 1500-2000′, where the prior snow surface consisted of just a few inches of soft snow on top of a firm crust. At treeline and alpine elevations wind slab avalanches 1-2′ deep will be likely for human triggering today. These tend to occur along ridgelines, gullies, and convex features that have been recently wind loaded. To assess how reactive the new snow is to the weight of a skier or rider you can use hand pits to see how well the new snow is bonding with the old surface and small test slopes to check for shooting cracks or small avalanches.

Loose snow avalanches are also likely in areas with soft snow on the surface. Dry loose avalanche (aka sluffs) will be likely on steep slopes and wet loose avalanches will be possible if the sun comes out on steep south facing terrain.

Small shooting crack near treeline in the Girdwood Valley yesterday, a good sign to watch out for if you are trying to identify where wind slabs are located. Photo 3.5.24

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Weather
Wed, March 6th, 2024

Yesterday: Light snowfall during the day with overcast skies. Light to moderate winds out of the east averaging 5-15 mph with gusts up to 40 mph. Snow accumulation of 6-8″ over the past 24 hours with snow falling down to sea level. Temperatures were in the upper teens F at upper elevations and mid to upper 20s F at lower elevations.

Today: Snowfall is expected to stop around 9-10 am this morning with a trend towards clearing skies during the day. Moderate east winds averaging 10-20 mph this morning should slow down as the snowfall stops and become light averaging 5-10 mph out of the south by this evening. Temperatures are hovering around 32 F at sea level this morning and are expected to stay close to the freezing level throughout the day at low elevations. At upper elevations temperatures should stay in the mid to upper 20s F today.

Tomorrow: Light winds and partly sunny skies are expected tomorrow with no new snowfall. Winds should average 0-10 mph out of the east. Temperatures should reach up to the low 30s F during the day at low elevations and mid to high 20s F at upper elevations.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 27 9 0.6 96
Summit Lake (1400′) 27 1 0.1 46
Alyeska Mid (1700′) 28 7 0.5 97
Bear Valley – Portage (132′) 32 5 0.7 5
Grouse Ck (700′) 32 2 0.2 65

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 19 ENE 15 38
Seattle Ridge (2400′) 23 E 6 14
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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.