Sat, March 19, 2016 Turnagain Pass Avalanche Forecast

Sat, March 19th, 2016

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

Below Treeline

Below 1,000'

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

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

Today’s avalanche concerns will be based on how today’s changing weather affects our region. Should 4-8” of new snow and Moderate Easterly winds arrive as forecasted, expect surface instabilities (wind slabs, loose snow, and storm slabs) to increase in size throughout the day. Pay attention for rapid loading and blowing snow along ridgetops and how well this new snow is bonding with the surfaces below. If you see any obvious signs of instability like shooting cracks or recent avalanches be prepared to alter your plans. The following avalanche problems will be directly proportional to the amount of snow and wind we receive today.

Wind slabs – There is currently a lot of low-density snow available for transport on shaded (NE to NW) aspects. Expect wind slabs to grow in size by mid to late afternoon as winds starts to build from the East. Be on the lookout for blowing snow, shooting cracks and pillow shaped pockets on leeward aspects.

Loose snow: Dry loose avalanches will be possible in steeper terrain and will grow in size throughout the morning. If for some reason the sun makes an appearance today, slopes with a southerly tilt, may experience natural wet loose avalanches.

Storm slabs: Storm slabs will likely be more of an issue later today in places protected from the wind. Again this will be directly proportional to the amount of snow that falls and will be an added reason to avoid steep terrain later in the day.

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

This week has been one of our most active glide avalanche cycles of the winter with dozens of dirty streaks observed in Girdwood, Turnagain Pass and Summit Lake. Yesterday a new glide avalanche was seen on the East side Seattle Ridge and another that occured late afternoon on a South aspect of Raggedtop in Girdwood.

Glide cracks cover all aspects within the mid elevation band (between 1000-3000’) and remain a significant threat to popular terrain. As long as glide cracks continue to open up, move and release, we will stress the importance of avoiding them, which is THE ONLY WAY TO MANAGE THIS AVALANCHE PROBLEM. Remember these are totally unpredictable, release naturally and could be deadly if you were to get caught-up in one. It is the entire winter snowpack releasing at the ground.

There is a lot of terrain where glide cracks can be challenging to see from the groud level. Here’s an arial view taken of the SW face of Cornbiscuit on Wed, 3/16. Photo by Jared Gross.

Penguin Ridge has been very active this week. This is a good reminder that there are summer trails that are threatened by avalanche terrain from above. This trail will remain closed through the winter.

Weather

Sat, March 19th, 2016

Yesterday skies were mostly cloudy and winds were calm. Daytime temperatures reached the mid 30’s F and overnight temperatures dipped into the low 20’s F. A trace of new snow fell overnight at Turnagain Pass.

Today a low-pressure system is moving into our region and 4-8 € of new snow is expected today. Light Northerly winds will become East and will increase to Moderate by the afternoon. Temperatures will gradually warm throughout the day, with highs expected in the mid 30F’s. Rain is possible at lower elevations by later afternoon.

Snow showers are expected throughout the weekend and temperatures will steadily increase causing rain at lower elevations tonight into tomorrow. An additional 8-12 € snow is forecasted for the upper elevations tonight through tomorrow morning. Winds are expected to remain Moderate from the East.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	26	2	0.1	134
Summit Lake (1400′)	28	2	0.1	45
Alyeska Mid (1700′)	25	2	n/a	109

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	22	NE	3	6
Seattle Ridge (2400′)	22	NE	2	5

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
04/16/24	Turnagain	Observation: Cornbiscuit	Krueger / Matthys Forecaster
04/15/24	Turnagain	Observation: Taylor Pass	John Sykes Forecaster
04/15/24	Turnagain	Observation: Seward Highway – Tern Lake to Portage	Joel Curtis
04/14/24	Turnagain	Observation: Sunburst	T. Olsen-Lund, R. Sullivan I. Adams
04/14/24	Turnagain	Observation: Turnagain Pass Snomo	K. Gallaher
04/13/24	Turnagain	Observation: Spokane Creek	Everet Megli
04/11/24	Turnagain	Observation: Tincan	John Sykes Forecaster
04/10/24	Turnagain	Avalanche: Seattle Ridge	Schauer/ Keeler Forecaster
04/10/24	Turnagain	Observation: Cornbiscuit South Face	Todd Kelsey
04/10/24	Turnagain	Avalanche: Tincan	N. Dumont J. Carlberg

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