Sat, February 02, 2013 Turnagain Pass Avalanche Forecast

Sat, February 2nd, 2013

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

Wind Slabs

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

More info at Avalanche.org

Wind slabs have been popping with skier influence over the last few days, but everything we’ve seen or heard about has been relatively small and manageable. The biggest concern is related to higher consequence terrain if someone decides to step it up and gets surprised. With limited snowfall over the last few days windslabs are 6-18 inches deep and are isolated to wind loaded aspects. Check the observations page for more recent examples.

Cornices are building and may be more unstable than usual due to high temperatures. Watch out when approaching the edge of a ridge, especially in flat light conditions.

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

The deep slab problem is a minor concern in most areas. Below 2500 feet it is unlikely to affect the deeply buried facets through 6 feet of hard slab and crusts. Above that, especially above 3000 feet, there is more concern for a couple reasons. The facets up high have not had enough warmth to promote significant bonding and increased strength. Snow depth is more variable, and shallow areas can be found where the weight of a person could affect those weak layers. The slopes also tend to be steeper at the upper elevations with more avalanche terrain to navigate.

Weather

Sat, February 2nd, 2013

Yesterday it was warm and raining up to near 2000 feet in Turnagain Pass. Precipitation intensity was low, but the liquid water on top of snow made for sticky skiing below treeline.

Today’s weather looks to be similar with small amounts of precip expected and continued warm temperatures. Rain is expected at sea level and may reach to above 1000 feet.

An east wind will blow moderate to strong at the ridges, with enough intensity to redistribute snow and create windslabs. Sunburst is reading wind gusts into the mid 40s already this morning.

Wendy will issue the next advisory Sunday morning, Feb 3rd.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
05/13/24	Turnagain	Observation: Eddie’s, Sunburst, Seattle, Cornbiscuit, Pete’s South	H Thamm
05/13/24	Turnagain	Observation: Turnagain Pass non-motorized side	Amy Holman
05/12/24	Turnagain	Observation: Warm up Bowl	Tony Naciuk
05/07/24	Turnagain	Observation: Turnagain Pass Wet Slabs	A S
04/29/24	Turnagain	Avalanche: Turnagain aerial obs	Tully Hamer
04/27/24	Turnagain	Observation: Johnson Pass	Noah Mery
04/23/24	Turnagain	Observation: Turnagain Sunny Side	Travis SMITH
04/21/24	Turnagain	Observation: Bertha Creek	Anonymous
04/20/24	Turnagain	Avalanche: Spokane Creek	Schauer/ Mailly Forecaster
04/16/24	Turnagain	Observation: Cornbiscuit	Krueger / Matthys Forecaster

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