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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, May 1st, 2021 - 7:00AM
Expires
Sun, May 2nd, 2021 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is LOW this morning and expected to rise to MODERATE as daytime heating softens surface crusts this afternoon/evening. Human triggered wet sluffs will become possible on any slope ~35 degrees or steeper that warms enough to harbor boot-top wet and saturated snow. These sluffs could be small or large and dangerous pending the terrain. Pay close attention to aspect, overhead hazard, and changing surface conditions. 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, 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.

SUNDAY AVALANCHE OUTLOOK:  No avalanche forecast will be issued tomorrow. Expect similar to decreasing avalanche danger Sunday. Mostly clear skies tonight should produce a solid re-freeze Sunday morning with cooler temperatures and east winds through the day limiting surface melting.

Special Announcements

CNFAIC End Of Season Operations:  Avalanche forecasts have ended for the 2020/21 season. Look for our Springtime Tips to be posted Sunday afternoon. As there is still plenty of snow on the ground, we would be grateful for any observations if you happen to get out and about!

Sat, May 1st, 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

Clear skies overnight and temperatures in the 20’sF this morning have likely produced a solid re-freeze of any snow that warmed up yesterday afternoon. This is good news for those wishing to harvest some corn on this sunny Saturday, which also happens to be the first day of May! The main thing to watch for is how the surface is warming through the day. Light east winds and direct sunshine should start melting surface crusts fairly quickly, even without exceedingly warm ambient air temperatures. Here are some things to keep in mind:

  • How ‘punchy’, wet and unsupportable is the snow is becoming?
    • East aspects will warm first around noonish, then south in the early afternoon and last west in the later afternoon/evening.
  • What aspects harbor just the right corn conditions? This would be soft enough for fun turns or riding, but not too soft that you start sinking in past your boot. This is when it becomes easy to initiate ‘push-a-lanches’ (a wet loose avalanche) in steep terrain.
  • Wet loose avalanches can get quite big on steep sustained slopes.
  • Wet loose avalanches can also initiate wet slab avalanches if the slope is really baking in the sun and water is percolating through the pack.
    • We have not seen this for over a week, but it’s still something to keep in mind and why it’s not worth jumping on slopes that are really mushy, unsupportable and wanting to fall apart.
  • Overhead hazard late in the day. As always in the spring, be aware of what is above you and what you’ll be traveling through on your way back to the car.

Cornices:  What about cornices? These have not been falling off as readily as we’ve seen in past years. Nonetheless, they are feeling the heat and can’t be trusted. Steering well clear of them from above and limiting exposure under them will be prudent as the spring progresses.

 

Punchy wet snow our easy clue to look for – telling us the snow has lost strength and if the slope is steep enough, wet avalanches can occur. 4.30.21.

 

There is still PLENTY of snow out there. This photo is from yesterday, looking west from Taylor Pass with Sunburst on the right and Seattle Ridge in the back. 4.30.21.

Additional Concern
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

Watch for glide cracks and limit time, or avoid if possible, being under them. Glide cracks can release into a destructive avalanche at anytime. They are completely unpredictable and don’t follow any perfect patten. Although it has been several days since we’ve heard of any cracks releasing, there have not been many people out to see them if they have.


Seattle Ridge often sees many glide cracks in the spring. Some of these release and avalanche and some end up just melting out in place. It’s impossible to determine what crack will do what so avoiding time under them is always a good idea. 4.30.21.

Weather
Sat, May 1st, 2021

Yesterday:  After a cloudy morning, skies cleared up around noon with light northwest ridgetop winds (5-10mph). Temperatures peaked in the high 40’sF and ~30F around 5pm  in valley bottoms and ridgetops respectively, before dropping to the 20’s overnight at all elevations.

Today:  Clear skies remained overnight and sunshine is expected to last through today. Ridgetop winds are forecast to be light from the east ~5mph. Temperatures should climb back into the the warm springtime realm of the 50’sF in valley bottoms and up to 40F along ridgelines.

Tomorrow:  Cloudy skies, moderate to strong east winds and a chance for a little precipitation are all expected to move in Sunday as a low pressure in the Gulf pushes a front our way. Models are showing at most a trace-.1″ of light rain below ~2,000′ with up to an inch of light snow showers above this. Ridgetop winds are forecast to blow in the 25-30mph from the east through the day before quieting down Monday. Models are hinting at another, more powerful system moving in Tuesday. This one could add 4-6″ of snow above ~2,000′ by Wednesday.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35 0 0 87
Summit Lake (1400′) 33 0 0 25
Alyeska Mid (1700′) 35 0 0 96

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 26 NW 4 13
Seattle Ridge (2400′) 31 NW 7 12
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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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