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ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, April 25th, 2024 - 7:00AM
Expires
Fri, April 26th, 2024 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger will start out LOW  but quickly rise to CONSIDERABLE as temperatures heat up and the chances for wet snow avalanches increase. The most likely avalanches to encounter will be wet loose avalanches, but we will also likely see continued glide and wet slab activity. All of these avalanches can be large and destructive, so it is important to pay attention to changing surface conditions and move to shaded aspects as the snow surface becomes wet and sloppy.

FRIDAY – AVALANCHE OUTLOOKWith mild overnight temperatures, cloudy skies, and a chance of rain tonight followed by another warm day tomorrow, avalanche conditions are expected to be dangerous. It is unlikely the snow will have a chance to freeze tonight, so be on the lookout for wet snow avalanches all day. Our next forecast will be posted Saturday morning.

Special Announcements

Avalanche Center End of Season Operations: We are continuing to issue forecasts on Tuesday, Thursday, Saturday, and Sunday mornings. For the non-forecast days we will give an avalanche outlook on the day prior. The final forecast for the season will be this Sunday, April 28.

Thu, April 25th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
3 - Considerable
Avalanche risk
Fri, April 26th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
3 - Considerable
Avalanche risk
Fri, April 26th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
3 - Considerable
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

With warm and sunny weather over the past few days, we have continued to see wet loose, wet slab, and glide avalanches release throughout the advisory area. Some notable activity includes a very active cycle on the front side of Seattle Ridge, as well as in the Girdwood Valley.

Wet slab avalanche on Penguin Ridge just above Girdwood. Photo taken 04.24.2024.

Avalanche Problem 1
  • Wet Loose
    Wet Loose
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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 in the full swing of springtime avalanche conditions right now, and we’re expecting to see more avalanche activity as things heat up during the day. With mostly clear skies overnight, surfaces were most likely able to freeze up at least a little bit. However, temperatures were hovering at or just above freezing for most of the night so it shouldn’t take very long for the surface crust to melt and the avalanche activity to pick up again today. Be on the lookout for rollerballs or pinwheels rolling down solar aspects as an initial sign of deteriorating conditions, and move to shaded aspects if you start to notice surfaces become sloppy and unsupportable. We’ve seen multiple loose wet avalanches gouging all the way down to the ground and entraining a large amount of snow this week, so be aware that even though a loose snow avalanche may start small, it has the potential to gain a lot of volume as it travels down slope.

Wet Slab Avalanches: We have seen a handful of wet slab avalanches release over the past week. These are bigger and not as easy to predict as loose wet avalanches, but the likelihood for these monsters increases as surfaces weaken and liquid meltwater starts moving through the snowpack. At relatively smaller loose wet avalanche may pull out a larger wet slab. This is just another reason to move out of the sun as surfaces begin to heat up.

Glide Avalanches: We have seen multiple glide avalanches release over the past two weeks, and it seems as though glide activity is increasing with the continued warm weather. These avalanches are very large since they involve the entire snowpack failing at the ground, and their timing is impossible to predict. Be sure to limit any time spent traveling under open glide cracks.

All three avalanche concerns on one slope in Summit: A small glide avalanche (left), and a wet loose avalanche pulling out a wet slab as it ran down slope (right). Photo: Joel Curtis, 04.24.2024.

A whole mess of glide activity near Portage Lake. Those debris piles are probably 30-40′ deep. 04.24.2024

Weather
Thu, April 25th, 2024

Yesterday: We had a beautiful spring day yesterday with clear skies and light easterly winds at around 5 mph with gusts of 10 to 15 mph. High temperatures were in the upper 30s F at upper elevations and up into the low 50s F down in the valleys. Lows overnight were in the upper 20s to mid 30s F. We did not record any precipitation.

Today: Skies should start out mostly sunny with increasing clouds through the day as a weak front moves in from the south. Winds are expected to remain light out of the east at 5 to 10 mph with gusts around 10 to 15 mph. High temperatures will be in the mid 30s to mid 40s F with lows in the upper 20s to mid 30s F. Chances for precipitation pick up later in the day, but we most likely won’t see any until tonight.

Tomorrow: There is a chance for light showers in the morning, with only a trace of precipitation expected and rain up to 1500 to 1700’. Skies should be partly to mostly cloudy, with clouds starting to break up in the afternoon. Winds are expected to remain light out of the east at 5 to 15 mph with gusts of 10 to 20 mph. High temperatures will be in the mid 30s to mid 40s F with lows in the mid 20s to low 30s F.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 40 0 0 83
Summit Lake (1400′) 39 0 0 37
Alyeska Mid (1700′) 44 0 0 96
Bear Valley – Portage (132′) 39 0 0
Grouse Ck (700′) 42 0 0 29

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 31 E 6 14
Seattle Ridge (2400′) 35 ESE 5 9
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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.