Mon, January 18, 2016 Turnagain Pass Avalanche Forecast

Mon, January 18th, 2016

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

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

Saturday night brought a brief ‘refresh’ of snow to most areas in Turnagain Pass and Girdwood Valley. Around 3″ of wet snow fell at 1,000′ (which is now capped by a crust) and 6″ of low density snow at the higher elevations above treeline. Moderate to strong Easterly winds along the ridgelines accompanied the snowfall. It was no surprise to see shallow wind slabs along the Tincan Ridge yesterday. Although these slabs were present, they were quite stubborn and hard to initiate on test slopes. The wind slabs sit on old snow (broken precipitation particles) with buried surface hoar intermixed, essentially Saturday’s surface snow.

For today, Martin Luther King, Jr. Day, there are two types of wind slabs to watch for: Old and New.

Old wind slabs: These older lingering wind slabs are in the 6″ to a foot deep range. And, they can be tricky; meaning they may not release till you are well on the slope. They also may be obscured by a skiff of fresh snow. Quick hand pits and jumping on test slopes are good ways to suss these out.

New wind slabs: We are expecting an increase in East winds later in the day. Keep an eye out for active wind loading. Any fresh wind slab should be touchy and release easily (as opposed to the older, stubborn wind slab). These also can form on top of one another.

Photo below is Graham Predeger testing a fresh wind slab/cornice feature from the top of Seattle Ridge yesterday (credit: Sully). These small terrain features are good ways to test the snow without committing to steep avalanche terrain.

This photo below is from a test slope near Hippy Bowl on Tincan Ridge yesterday. What it shows are both a new wind slab (3-4″ thick) stepping down to an older wind slab (6″ thick). I know, it’s tough to see, but hopefully you get the idea…

Avalanche Problem 2

Glide Avalanches

Glide Avalanches

Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.

More info at Avalanche.org

After several days of glide cracks releasing on Turnagain Pass – some of which were ‘front and center’ on Seattle Ridge – there was only one new glide avalanche seen yesterday. This was a smaller glide on the South face of Wolverine Ridge around 1,500′ in elevation.

Again, we preach avoidance for this avalanche problem. Avoiding, or doing your best to limit your exposure time, under these glide cracks is advised. There are still many large cracks looming – most notably on the East face of Seattle Ridge and on the South and West faces of Tincan ridge. These are the two areas most easily accessed by backcontry travelers.

Below is Heather’s photo from Seattle Ridge on Saturday. You can clearly see the two glide avalanches from over the weekend as well as the looming brown crack on the next gully over to the right. With yesterday’s 3-6″ of new snow, many of these cracks are ‘dusted over’ and much harder to see now.

Weather

Mon, January 18th, 2016

Yesterday’s weather consisted of mostly overcast skies, gusty Easterly ridgetop winds and warm temperatures (mid 30’s at 1,000′, upper 20’s at 3,000′). Winds quieted down in the afternoon and have remained light from a generally East direction overnight. Warm air has been streaming in at the upper elevations overnight – Sunburst reported 32F at midnight, this station sits at 3,812′.

Today, we can expect mostly overcast skies again with a chance for sunny breaks in the clouds. Later in the afternoon and this evening, the Easterly winds should pick up along with light snowfall (rain below 1,000′). Ridgetop winds are forecast to be ~15mph from the East. Temperatures should cool to the mid-upper 20’s F at the upper elevations and remain around 30F at 1,000′.

Overnight tonight and into tomorrow, an embedded low-pressure in Northern Gulf will bring a quick shot of snow above ~1,000′-1,500′ with light rain below – accumulations look to be in the 3-6″ range. Winds are expected to be 20-30mph from the East on the ridgelines and strong gap winds along Turnagain Arm.

PRECIPITATION 24-hour data (6am – 6am)

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	33	1	0.1	83
Summit Lake (1400′)	32	1	0.1	27
Alyeska Mid (1700′)	33	0	0.1	63

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	29	ENE	11	38
Seattle Ridge (2400′)	30	N/A	N/A	N/A

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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