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ARCHIVED - Forecasts expire after 24 hours.
Issued
Mon, March 4th, 2024 - 7:00AM
Expires
Tue, March 5th, 2024 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is expected to rise to MODERATE in the higher elevations (above 2,500′) as easterly winds increase today. Wind slabs, up to a foot deep, are expected to form along the ridgelines. Watching for winds strong enough to drift loose surface snow into shallow wind slabs will be the main concern.

Slopes sheltered from the winds and in the mid and lower elevations the danger remains LOW.

SUMMIT/JOHNSON PASS:  Winds are expected to reach the higher elevations in the central Kenai mtns as well, increasing the potential for new wind slabs to form. Additionally, a weak layer buried 1-2′ deep at elevations above 2,000′ is still a lingering concern for triggering a larger avalanche.

Mon, March 4th, 2024
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
Tue, March 5th, 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
Tue, March 5th, 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

No new avalanches were seen or reported from yesterday. The last known avalanche was on Saturday when a skier triggered a slab around 8″ deep while bootpacking up a couloir in the Winner Creek drainage just north of Girdwood.

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 quiet weekend, a more active weather pattern is again in store. For today, cloudy skies, a bump in east winds, and a chance for a few snow flakes is expected (trace-2″ of snow to sea level). For tomorrow, there is a chance for more east wind and more snow (4-10″ of snow to sea level with greater amounts in Placer Valley). We’ll see how these events really shake out, but the main story is, paying attention to changing weather.

Fresh wind slabs:  Along the higher ridges and the terrain close to Portage and Turnagain Arm, winds should be increasing from the east reaching sustained speeds of 10-20 mph and gusts to 30 mph. This is not that remarkable, yet should be strong enough to form shallow wind slabs on leeward slopes and the sides of gullies in certain areas. Any new slab is likely to be on the smaller side (6-12″) and soft. Hopefully these will be easy to see and avoid. The clouds may impede visibility making it harder to watch for wind drifting snow, but this ‘active loading’ will be the main concern for the forecast zone.

Dry Loose Avalanches:  Sluffs on steep slopes with soft surface snow should be expected. These were common on the steeper slopes over the weekend.

Persistent Slab avalanches south of Turnagain Pass:
In the central Kenai mtns a shallower snowpack exists with a buried weak layer that is producing avalanches now and again. The last one was on Friday when a skier triggered a slab roughly 2′ deep and 75′ wide. The slide was around 2,800′ in elevation, north aspect, and above Bench Lake in the Johnson Pass area. No one was caught. The avalanche on Saturday in Winner Creek is thought to have released within the newest snow from earlier last week, so does not appear to be associated with a buried weak layer.

In general it’s good to remember surprise avalanches can happen. Maintaining safe travel protocols is a great way to reduce our risk. This includes traveling one at a time in steep terrain and watching partners from safe spots outside of avalanche runout zones. It also means paying attention to any warning signs like changing weather and shooting cracks or collapsing, which indicate unstable conditions.

 

Great photo of the large cornices looming on Magnum Ridge by Andy Moderow. Once the weather warms, these should begin to start destabilizin. Spring is not that far away! 3.2.24. 

Weather
Mon, March 4th, 2024

Yesterday:  High clouds with light and variable ridgetop winds were over the region yesterday. No precipitation was recorded. Temperatures have warmed dramatically over the past 24-hours from the -10 to 5 F range into the teens to 20s F.

Today:  A weak weather system is passing through today which should bring an increase in ridgetop winds (easterly 10-20mph gusts to 30) and a chance for a few snow flurries. Between a trace to 2″ of snow is forecast to sea level by tonight. Temperatures should remain in the 20s F at most locations and close to 32F at sea level.

Tomorrow:  Another more powerful low-pressure will push in for Tuesday. This looks to bring a further increase in ridgetop winds (easterly 15-30 mph gusts 40-50 mph) and heavier snowfall. Anywhere from 4 to 8″ is expected to fall between Tuesday morning and midnight on Tuesday, greater amounts in Placer Valley. Models show temperatures remaining near 32F at sea level and 20s in the mountains. Stay tuned!

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 16 0 0 87
Summit Lake (1400′) 16 0 0 45
Alyeska Mid (1700′) 18 0 0 87
Bear Valley – Portage (132′) 16 0 0
Grouse Ck (700′) 16 0 0 65

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 12 var 3 11
Seattle Ridge (2400′) 13 var 7 15
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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.