Sat, January 14, 2017 Turnagain Pass Avalanche Forecast

Sat, January 14th, 2017

Alpine

Above 2,500'

3 - Considerable

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

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

New snow (6+ inches at Turnagain and 12+ inches in Girdwood Valley) combined with moderate winds speeds ESE-ENE 15-25 (gusting to 40 mph) in the last 24 hrs have formed fresh, sensitive wind slabs on leeward slopes. Wind slabs may be 1-2′ thick. These slabs will be sitting on a variety of old surfaces and may not bond well. Slick wind crusts and soft facets covered most of the terrain prior to the storm. Places where the new snow landed on the slick crusts will be especially suspect. Look for new cornice formation, pillowed and drifted snow and cracking. Winds speeds have mellowed this morning but are expected to pick back up this afternoon. Watch for wind transporting snow and avoid travel underneath actively loading slopes as naturals will be possible.

Photos: National Avalanche Center

Yesterday afternoon. 1.13.17, Snow starting to drift and crack.

Avalanche Problem 2

Storm Slabs

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

In areas unaffected by wind new snow can still act as a slab especially in Girdwood where more snow fell. In addition temperatures warmed up overnight and the storm snow may be slightly upside down with heavier snow over lighter snow. The question during and right after a storm is “How well is the snow bonding to the old snow surface it landed on?” As noted above with the wind slabs, the storm snow landed on a variety of surfaces including slick wind crusts and may not initally bond well. Stepping off the skin track or jumping off your snowmachine to do quick hand pits will be a great tool for determining new snow depth and bonding. Also be on the lookout for loose snow avalanches in the steep terrain where the storm snow may not stick to old surfaces at all. Avoid terrain traps i.e. places where shallow avalanches could pile up more deeply and look for cracking.

As always practicing safe travel protocol is key:

1) Expose only one person at a time

2) Group up in safe zones

3) Have an escape route planned

4) Pay attention to other groups. This could be a busy holiday weekend!

Additional Concern

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

Glide cracks have been slowing opening this week; though we have not seen/heard of any new cracks releasing. Keep an eye out for cracks, which is difficult with new snow and wind, and limit time underneath them. Main Bowl is one of the spots where glide cracks threaten terrain that is commonly traveled.

Weather

Sat, January 14th, 2017

Yesterday snow fell throughout the day with intensity picking up late in the afternoon. Winds were easterly 15-20 mph with gusts into the 30s and 40s. Temperatures were mostly in the 20Fs with a band of warm air at road level in Turnagain Pass in the 30Fs. Overall temperatures warmed slightly overnight and winds speeds dropped.

This morning the skies are clearing on Turnagain but snow showers continue in Girdwood. These are forecasted to taper off to partly cloudy skies. Colder air will move in this afternoon with westerly winds to 15-25 mph. Temperatures will drop into the single digits tonight. The next storm system is forecasted to arrive tomorrow with another round of snow into Monday.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	33	7	.6	40
Summit Lake (1400′)	21	3	.4	14
Alyeska Mid (1700′)	28	13	1.4	35

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	22	ENE	18	40
Seattle Ridge (2400′)	24	SE	15	29

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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