Mon, February 03, 2014 Turnagain Pass Avalanche Forecast

Mon, February 3rd, 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

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

The unusually warm and wet weather of late January has given way to a period of cooling. This gradual cooling has allowed the once saturated snowpack to “lock up” in many locations. The end result is a stout crust on the surface. This crust is now over 2 feet thick in places and can support a tremendous amount of weight. Because of this, it will be very difficult to trigger an avalanche in all but the highest elevations of the forecast zone.

In steep upper elevation starting zones above 3,000’, the possibility still remains for triggering a deep, dangerous slab. Weak snow near the ground still exists. This weak snow is now covered with slabs up to 6’ in depth. The likelihood of triggering one of these slabs is low today. However, if you were to trigger one of these slabs the end result would be a high volume avalanche that would be unsurvivable.

This is a difficult avalanche problem to assess. The easiest way to deal with this problem is to avoid steep terrain in the upper elevations. Avoiding steep rollovers & thin spots in the slab will also minimize the possibility of triggering a deep slab avalanche today.

Avalanche Problem 2

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

It is also worth paying attention to old wind slabs that formed last week. These slabs exist in pockets in the higher elevations and will be on the shallow side, less that 10” in depth. Avoiding these pockets will help to minimize the greater hazard of losing control in steep terrain on a slick, hard crust. A fall in steep terrain today will be very difficult to arrest, hence the term “slide for life” conditions.

Weather

Mon, February 3rd, 2014

No precipitation has fallen over the past 6 days. Ridge top winds over the past 24 hours averaged 10mph out of the East with a gust to 32 mph. Temperatures at the Sunburst station at 3,812′ have averaged 25 F.

Today expect dry conditions with high clouds. Ridgetop winds will be in the 15-20mph range out of the SE and temperatures will be in the mid to high twenties F.

A large area of weak high pressure over much of the state will continue to dominate our weather through the week. A shift in the overall weather pattern looks to be on the distant horizon (next weekend). Stay tuned for timing and more details later this week.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
12/02/23	Turnagain	Observation: Seattle Ridge	Schauer / Keeler Forecaster
12/02/23	Turnagain	Observation: Tincan South Side	Anonymous
12/02/23	Turnagain	Observation: Eddies up track	Luc Mehl
12/01/23		Avalanche: Sunburst	John Sykes Forecaster
12/01/23	Turnagain	Observation: Eddie’s trees	Anonymous
12/01/23	Turnagain	Observation: Turnagain – God’s Country	Graham Predeger Forecaster
11/30/23	Turnagain	Avalanche: Tincan Trees	Kakiko Ramos-Leon
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

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