Fri, December 20, 2013 Turnagain Pass Avalanche Forecast

Fri, December 20th, 2013

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

Below Treeline

Below 1,000'

2 - Moderate

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

Wind and snow that came as a result of a quick hitting storm on 12/18 have left stiff wind slabs in upper elevation starting zones. Winds from this recent storm deposited slabs on generally West, Southwest and South facing slopes. These slabs are “upside down” where the wind was most prevalent and are sitting on weak snow on top of a crust. It has been 24 hours since this last storm abated. As a result the snow will be less reactive today. That does not mean that things have “healed”. Given the general makeup of our snowpack, it will still be possible to trigger old wind slabs that are not well bonded to the underlying snow.

If you experience collapsing like we did yesterday, it will be worth scaling back your objectives and terrain choices. Collapsing is one of three obvious signs of instability (the others are recent avalanches and shooting cracks). When any one of these signs are present it is the snow telling you to “back off”. Avoiding steep slopes with snow that sounds hollow or has a rounded, pillowy look to it will help in avoiding this problem today.

Weather

Fri, December 20th, 2013

In the past 24 hours no new snow was reported. Temperatures have risen overnight with increased cloud cover. Ridge top temperatures are currently in the low 20s F. Winds have been light out of the East and Southeast.

Today we can expect snow showers beginning in the morning and increasing late in the day into the overnight hours. Accumulation of 1-2 € is possible by the end of the day. Temperatures will continue a general upward trend and should remain in the mid to upper 20s F at ridge tops. Winds will be light out of the Southwest.

A trough of low pressure in the Bering Sea will continue to send small shots of moisture in our direction into the weekend. Continued light snow showers and rising temps are on tap for the next several days.

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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