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ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, April 29th, 2021 - 7:00AM
Expires
Fri, April 30th, 2021 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is MODERATE at all elevations. Triggering a wet loose avalanche is possible on slopes ~35 degrees or steeper that harbor boot-top wet and saturated snow. Pay close attention to the amount of re-freeze that may, or may not, have occurred overnight and how the surface is warming through the day. Avoid being under glide cracks and give cornices a wide berth.

CROW PASS, PORTAGE VALLEY:  Be cautious of summer trails that pass under/through avalanche paths, such as the Byron Glacier Trail and Crow Pass Trail. Although natural avalanches are not expected today or Friday, it is best practice to avoid being in any avalanche runout zone in the late afternoon/evening hours when daytime heating can destabilize snow from above.

FRIDAY AVALANCHE OUTLOOK:  No avalanche forecast will be issued tomorrow. Expect similar avalanche danger for Friday. If the sun shines tomorrow, watch for sunlit slopes to soften quickly.

Special Announcements

CNFAIC End Of Season Operations:  Daily avalanche forecasts have ended. Our last forecast will be Saturday morning with our Springtime Tips posted on Sunday afternoon. We are grateful for any observations if you happen to get out and about!

Thu, April 29th, 2021
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.
Avalanche Problem 1
  • Wet Loose
    Wet Loose
  • 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.
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 glorious 12-day stretch of sunshine, clouds streamed over the region yesterday evening and are slated to remain through today and into the beginning of tomorrow. There may be a few rain drops out there this evening, but those should stay closer to Whittier and Seward. Although temperatures are cooler, the cloud cover has limited the amount of overnight re-freeze; clouds tonight will likely limit the re-freeze for Friday as well. With temperatures in the upper elevations below freezing, those areas should have a solid crust, but it’s the mid and lower elevations that will be questionable. Hence, how much re-freeze has occurred? This is the question for anyone headed out to find some corn snow.

Keep in mind that triggering a wet loose avalanche is the main concern. This should be relatively easy to suss out as it completely depends on how wet the snow we are traveling on is. Slopes that are frozen, or those with just a few inches of soft snow over a hard crust are not an issue. But… once they warm enough that your boot or snowmachine starts to punch into 10+” of mush or so, it’s high time to head somewhere else. Either out of avalanche terrain or to slopes with less wet snow.

As for Wet slab avalanches, these remain on our mind, especially with the potential for a limited re-freeze and water slowly making its way down into the pack. For the next couple days this concern is mainly below around 3,000′ due to the colder temperatures in the high elevations. The rules are the same for this avalanche issue; steer clear of slopes with boot-top wet and saturated snow. Wet slabs are often triggered by a wet loose avalanche and can turn a small avalanche into a much larger and dangerous one.

Cornices:  The past 12 days of warm temperatures is causing looming cornices to slowly droop. These are most unstable in the heat of the day, but should be suspect anytime. A cornice fall could trigger a wet avalanche on the slope below when conditions are ripe. Be aware to not accidentally travel onto one and limit any exposure under them.

Tincan’s west face, just above treeline. A lot of snow still remains out there! 4.27.21. Joe Kurtak.

Pastoral Peak, seen from Sunburst/Taylor Pass, last Friday, 4.23.21 by Troy Tempel.

Additional Concern
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.
More info at Avalanche.org

Glide cracks will be something to keep our eye on as long as snow covers the hillsides. These cracks can release into a destructive avalanche at anytime. It has been several days since we’ve heard of any cracks releasing. That said, there have not been many folks out in general to see them if there have been some failing. As always, watch for these and limit time, or avoid if possible, being under them.

Glide crack on Tincan. Photo taken Tuesday (4.27.21) by Joe Kurtak.

Weather
Thu, April 29th, 2021

Yesterday:  Mostly sunny skies turned cloudy late in the day as a weak front pushed in from the south. Ridgetop winds were easterly in the 10-15mph range with gusts in the 20’sF during the day and have quieted down overnight. Temperatures climbed to the 40’sF in the mid elevations and have dropped back to the 30’s overnight.

Today:  Mostly cloudy skies are expected to remain through today. A rain drop or two might fall but no measurable precipitation is expected in Girdwood or Turnagain Pass. Ridgetop winds are slated to shift northwesterly midday (5-10mph) as a trough pushes in from the west. This will bring in cooler temperatures and daytime high’s look to be in the low 40’sF at the lower and mid elevations and mid 30’sF along the ridgelines.

Tomorrow:  Skies should begin to clear tomorrow with the potential for sunshine later in the day and into Saturday. Ridgetop winds look to be 5-15mph from the northwest Friday and switching back to the east (5-10mph) on Saturday. Temperatures will remain on the chiller side with high’s in the 40’sF at mid elevations and low’s in the 30’sF.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 40 0 0 89
Summit Lake (1400′) 42 0 0 27
Alyeska Mid (1700′) 42 0 0 99

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 30 NE 13 28
Seattle Ridge (2400′) 33 SE 8 18
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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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