Tue, November 27, 2012 Turnagain Pass Avalanche Forecast

Tue, November 27th, 2012

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

1 - Low

Below Treeline

Below 1,000'

1 - Low

0 - No Rating

1 - Low

2 - Moderate

3 - Considerable

4 - High

5 - Extreme


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

Persistent Slabs

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.

More info at Avalanche.org

There has not been a whole lot of change in the avalanche conditions lately and we have not heard of any avalanche activity the past few days. The pack is becoming weaker and weaker every day under clear and cold weather. Surface conditions consist of surface hoar in most areas and near surface facets below. Very little wind for a while now has kept the recycled powder quite nice. The snow is still mostly supportable to skis and/or a board but once you step off, your boot goes straight to the tundra. Rocks are the biggest hazard where most folks are recreating right now.

That said, the steeper slopes at the upper elevations continue to harbor slabs that have the potential to avalanche to the ground and take someone on a nasty ride. Slopes that are most likely to be triggered are those at the higher elevations in the 40 degree range and unsupported from below. Probing with a pole to feel for stiff snow over hollow feeling snow and watching for collapsing and cracking are good ways to find suspect areas.

This problem is very slowly getting better and for the snow geek here is a pit profile of one such suspect slope HERE. There are a few reasons the pack is taking longer to rot away at the upper elevations. One is the snow is deeper and stiffer than the lower elevations so it simply takes longer. Another is the temperature has remained warmer (upper teens to mid 20’s) compared with the single digit temperatures below treeline, this is creating much lower snowpack temperature gradients at the higher elevations than the large gradients seen at the lower elevations. But the fact remains, the whole pack is well on its way to becoming one big weak layer.

Weather

Tue, November 27th, 2012

Clear skies and light easterly winds prevail once again today. A strong temperature gradient exists this morning with mid 20’s F above treeline and minus single digits below treeline, -10F in Portage (burr). Winds are clam currently and forecast to be around 5mph today from the east. Tomorrow, Wednesday, looks to me more of the same. In fact, it looks that way into the beginning of December:

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).

Kevin will issue the next advisory Thursday morning, November 29th.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
04/16/24	Turnagain	Observation: Cornbiscuit	Krueger / Matthys Forecaster
04/15/24	Turnagain	Observation: Taylor Pass	John Sykes Forecaster
04/15/24	Turnagain	Observation: Seward Highway – Tern Lake to Portage	Joel Curtis
04/14/24	Turnagain	Observation: Sunburst	T. Olsen-Lund, R. Sullivan I. Adams
04/14/24	Turnagain	Observation: Turnagain Pass Snomo	K. Gallaher
04/13/24	Turnagain	Observation: Spokane Creek	Everet Megli
04/11/24	Turnagain	Observation: Tincan	John Sykes Forecaster
04/10/24	Turnagain	Avalanche: Seattle Ridge	Schauer/ Keeler Forecaster
04/10/24	Turnagain	Observation: Cornbiscuit South Face	Todd Kelsey
04/10/24	Turnagain	Avalanche: Tincan	N. Dumont J. Carlberg

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