Wed, March 11, 2015 Turnagain Pass Avalanche Forecast

Wed, March 11th, 2015

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

1 - Low

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

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

After a three-day period of moderate Westerly winds accompanied by 6” of new snow, lingering wind slab instability remains our primary concern. Due to the unusual wind direction of this last storm pockets of wind slabs1-2′ thick are likely to be the more tender on steep Northern and Eastern slopes. These wind slabs could also be found on other aspects where cross-loading is more common like along gullies and on leeward aspects of terrain features.

Use caution in steep terrain and avoid smooth pillow shaped features. These wind slabs could vary from hard to soft and are likely to break above you. Be sure to practice safe travel habits. Identify safe spots, move between islands of safety one at a time, and always have an escape zone in mind.

On a side note… Skiing and riding conditions are better than they look in Turnagain Pass. Pockets of loose unconsolided (Powder) snow are easily found on good portions of Southwestern aspects. Surface conditions are variable along ridgelines, but wind erosion is softer and more forgiving than it appears.

A view of Hippy Bowl from 3200′ on Tincan. Soft Sastrugi (wind erosion) along ridges makes for easy access to nice powder stashes on Southwestern aspects.

Additional Concern

Dry Loose

Dry Loose

Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

More info at Avalanche.org

Cold temperatures are continuing to “dry” out the surface snow and fast moving snow “sluffs” could pick up enough speed to knock you off your feet. This is minor concern, but one worth keeping in the back of your mind if venturing in steep terrain.

Weather

Wed, March 11th, 2015

Yesterday skies were clear and day-time temperatures reached the teens F in the sun. Ridgetop temps and overnight lows hovered around 0 F. Winds were light 5-10 mph from the West. No new precipitation fell in the last 24 hours.

Today expect more of the same; clear skies and cold temps. Day-time temperatures may reach 10 F and lows should dip to -5 F. Ridgetop winds will increase later in the day, 10-20 mph from the West, and no precipitation is expected.

More cold dry weather is expected through the weekend. The next talk of precipitation is early next week as a large Sourtherly flow near Kodiak is expected to move North and East. There is uncertainty if it will reach Southcentral Alaska, but if it does, expect warm temperatures and moisture.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	8	0	0	44
Summit Lake (1400′)	4	0	0	9
Alyeska Mid (1700′)	8	0	0	27

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	1	W	5	13
Seattle Ridge (2400′)	2	W	6	17

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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