Fri, January 24, 2014 Turnagain Pass Avalanche Forecast

Fri, January 24th, 2014

Alpine

Above 2,500'

4 - High

Treeline

1,000'-2,500'

4 - High

Below Treeline

Below 1,000'

4 - High

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

Wet Loose

Wet Loose

Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

More info at Avalanche.org

The West face of Pyramid slid sometime yesterday afternoon. This avalanche ran full path, approximately 3,000’ and took out what appears to be weak snow near the ground and the entire snowpack above it.
Pyramid

With over an inch of water that has fallen in the past 24 hours coupled with another .4” forecasted for today, expect very large natural avalanches like this to remain a possibility. Avoidance is the only way around this avalanche problem for now. As temperatures cool and precipitation diminishes over the weekend expect the likelihood of wet slab and wet loose avalanches to go down.

Up to 2,500′ in elevation the snowpack was isothermal yesterday. Temperatures overnight have remained elevated. In addition to large wet slabs, expect wet loose avalanches in steeper terrain. Avoid being in the runout of larger paths if you happen to find yourself in the lower elevations today.

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

Above treeline the snowpack has been growing over the past week. While our time on or near ridge lines has been limited of late, we know that rain in the lower elevations has equated to heavy snow above 3,000’. The general snowpack structure is poor in the higher elevations, with weak snow sitting at the base. Slabs up to 6’ in depth have the potential to release, take out entire slopes and run far. As freezing levels climb and more precipitation falls today, the likelihood of deep unsurvivable slabs releasing will go up.

Additional Concern

Cornice

Cornice

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

More info at Avalanche.org

Yesterday my partners and I were able to get a look up at several ridge lines. Cornices have grown exponentially over the past week. Similar to Deep Slabs and Wet Avalanches, cornices have the potential to drop onto slopes and trigger very large unsurvivable avalanches. Avoid being in the runout of large avalanche paths today, especially those with large cornices looming above starting zones.

Weather

Fri, January 24th, 2014

Yesterday brought a seventh day of warm and wet conditions. Another ~1.3 € of water in the form of rain fell in the Girdwood Valley. Freezing levels climbed as high as 3,800′.

Sunburst 24 hour summary:
29 F average, 32 F max
28 mph winds out of the East, gust to 74

Today expect another day of similar weather. Up to an additional .4 € of water will fall, winds will be out of the East at 25-35 mph with higher gusts. Freezing level with climb as high as 4,000′ today.

Tomorrow will bring the first break in the wet weather. Skies will clear with valley fog developing. Temperatures will remain mild.

The extended outlook points to a potential high pressure blocking pattern developing by the middle of next week. Pray for snow!

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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