Wed, February 05, 2014 Turnagain Pass Avalanche Forecast

Wed, February 5th, 2014

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

In terrain above 3,500’, the last storm cycle laid down mostly snow (as opposed to rain). Terrain above this elevation is harboring old wind slabs up to a foot in depth. These slabs are resting on weak interfaces. It is on steep upper elevation leeward slopes where you are most likely to encounter unstable snow today. The likelihood of triggering an old wind slab is on the lower end of the scale but cannot be ruled out. If you were to trigger an old wind slab today and get knocked over or lose control, it would be very difficult to stop yourself. It is for this reason that it is worth avoiding steep (over 40 degree) upper elevation terrain.

Avalanche Problem 2

Deep Persistent Slabs

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

More info at Avalanche.org

Slabs 3-6 feet thick are sitting on weak snow near the ground in the upper elevations. It is less likely to trigger a deep slab today in comparison to a more shallow old wind slab. However, the possibility remains for triggering a slab that can pull out snow to the ground. Unlike the persistent (old) wind slab concern, deep slabs have the potential to move large volumes of snow and be unsurvivable. Avoiding likely trigger points, especially areas where slabs are thinner, will lower the likelihood of triggering a deep slab avalanche today.

Additional Concern

Announcement

Announcement

More info at Avalanche.org

In case you’re just tuning in, we have a very thick crust in the forecast area. This “bulletproof” crust exists on all aspects up to 3,500’ in elevation, and is over 2 feet thick in places. Travel in steep terrain warrants extra caution, as arresting a fall is very challenging at this time.

Expect all of these issues to remain until a shift in the weather pattern takes place and surface conditions change.

Weather

Wed, February 5th, 2014

In the past 24 hours temperatures at the Sunburst Station at 3,812′ have averaged 21 F. Winds there have averaged 5 mph out of a variety of directions with gust to 21 mph. It has now been 8 days since any precipitation has fallen.

Today expect clear skies. Temps will be in the low to mid 20s F at ridge tops. Winds will be light, in the 5 to 10 mph range out of the North.

The long term outlook shows more of the same. An uptick in winds for tomorrow and a general cooling trend will continue as high pressure dominates much of the state.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
11/27/23	Turnagain	Avalanche: Tincan Ridge	Schauer/ Stiassny Forecaster
11/26/23	Turnagain	Observation: Road report: Slide with dirt on Repeat offender	Anonymous
11/26/23	Turnagain	Observation: Pete’s North	Ben Sullender
11/25/23	Turnagain	Observation: Tincan trees	John Sykes Forecaster
11/21/23		Observation: Spokane Creek	John Sykes Forecaster
11/20/23	Turnagain	Observation: Sunburst	Anonymous
11/19/23	Turnagain	Observation: Magnum – PMS Bowl	Schauer/ Cullen/ Jonas Forecaster
11/19/23	Other Regions	Observation: Sunnyside/Penguin	Jose Ramos-Leon
11/19/23	Turnagain	Observation: Eddies	Andy Moderow
11/19/23	Turnagain	Observation: Cornbiscuit	Anonymous

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