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ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, November 30th, 2022 - 7:00AM
Expires
Thu, December 1st, 2022 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is MODERATE at the higher elevations, above 2500′. It remains possible a person could trigger a lingering wind slab up to 1-2′ deep. Additionally, we are still concerned a larger avalanche could be triggered, up to 3-4′ deep, due to weak snow at the base of the snowpack. Below 2,500′ the avalanche danger is LOW.

Special Announcements

Avalanche Education Scholarships: Get your application in TODAY! The Friends of the Chugach Avalanche Center host two scholarships; the deadline is December 1st. Several opportunities are available. See details HERE.

Wed, November 30th, 2022
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
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. Dangerous avalanche conditions. 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

The last known avalanche activity was some small natural wind slabs triggered by the strong NW outflow winds 4 days ago.

Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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

Despite the cold and clear conditions over the region, a welcome warm-up occurred overnight at the higher elevations. Sunburst weather station just hit 22F as of 6am – wow – while parking lots remain in the minus single digits. If you are headed out, it will be the warmer elevations, above 2,500′, where a couple lingering avalanche concerns exist.

There is still a chance a person could trigger a older wind slab from Saturday’s NW wind event. Although folks have found these wind slabs to be generally non-reactive, we should still look out for them in higher less traveled and exposed terrain. As always, watch for the tell-tale signs of stiffer snow over softer snow and cracks that shoot out from you.

The other issue is the October facets that sit at the base of the snowpack at elevations above 3,000′. Facets can be tricky and surprise us, which is why we aren’t quite ready to forget about this layer. If an avalanche is able to be triggered, it would be the entire depth of the snowpack, around 2-4′ deep, and dangerous. We should keep a feel out for any whumpfing of course, but really, using good travel protocol and simply being suspect of the snowpack is good way for us to approach the high terrain. This means maybe waiting to get onto a steep high-consequence slope, or if choosing to do so, expose only one person at a time and have escape routes planned.

Tincan’s Hippy Bowl photographed on Sunday. The cold temperatures are ‘eating away’ and loosing the wind stiffened snow and folks are finding some decent riding conditions. 11.27.22.

Weather
Wed, November 30th, 2022

Yesterday:  Cold, clear and mostly calm conditions existed yesterday. Ridgetop winds were 5-10mph with gusts in the teens from the north and west. Temperatures were in the minus single digits to plus single digits across all elevations.

Today:  Clear skies this morning will transition to some clouds later this afternoon. Temperatures have climbed into the low 20’sF at the higher elevations overnight, creating an impressive inversion with minus single digits in valley bottoms. Ridgetop winds are forecast to be 5-15mph from the northwest. Light snow flurries are expected tonight, adding 1-2″ of snow by tomorrow morning.

Tomorrow:  Skies look to clear back out tomorrow with winds bumping up from the north. Ridgetop winds look to be in the 15-25mph range. Temperatures are slated to remain on the warmer side, in the teens to 20’sF at all elevations. Clear and dry conditions look to remain through early next week.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 5 0 0 24
Summit Lake (1400′) -6 0 0 13
Alyeska Mid (1700′) 6 0 0 18
Bear Valley – Portage (132′) -2 0 0

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 13 W 8 17
Seattle Ridge (2400′) 10 NNE 4 9
Observations
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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.