Sat, January 09, 2016 Turnagain Pass Avalanche Forecast

Sat, January 9th, 2016

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

3 - Considerable

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

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

After a brief break in storms last week gave backcountry travelers an opportunity to get out into the mountains, we are back at it today with a warm, wet and windy storm rolling through for the weekend. Overnight there has been .5 to 1″ of rain below 2,000′ and roughly 5-8″ of wet snow above this. Today we are expecting another .5″ of precipitation; this equates to rain below 1,500′ and 3-5″ of wet snow above.

In the Alpine, above 2,500′, where dry snow is falling avalanche issues are expected to be confined to what we call ‘storm snow instabilities’. This means avalanches will be composed of the new storm snow and are not expected to break into layers deeper in the pack. The most likely avalanches will be on wind loaded slopes where fresh wind slabs 8-16″ have formed. These are always the most ‘touchy’ during formation or just after. Skies are not likely to clear enough today, but if they do and you find yourself in the dry snow, watch for how the winds have distributed the snow during the storm. Look for smooth rounded surfaces, hollow feeling snow and stiff snow over soft snow, these are signs of wind loading and something to steer clear of on steep slopes today.

*Cornice falls will again be a concern today with the warm temperatures. These can break at anytime on their own as well as with the weight of a person. They can trigger an avalanche below and be very dangerous.

Avalanche Problem 2

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

Wet loose avalanches are expected below 2,500′ where wet snow is falling and/or rain. These wet ‘sluffs’ have the ability to entrain large amounts of wet snow and run further than expected in some cases. However, today these should only entrain the top 6-8″ of snow cover and be more moderate in size. Areas such as Seattle Ridge, above the motorized lot, may see some wet loose avalanches running today.

Photo below is of the Seattle Ridge snowmachine ‘uptrack’. Many steep slopes and gullies sit along this ridge to either side of the uptrack as well as above it. Sticking to the mellow terrain and avoiding time under these slopes and gullies will be key today.

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

Several glide cracks are opening and some have released in the region. As with cornices, these are best dealt with through avoidance and limiting any exposure underneath them.

Weather

Sat, January 9th, 2016

Partly cloudy skies and light rain showers (below 1500′) and snow showers (above 1500′) covered the area yesterday. Ridgetop winds were generally Easterly around 20mph with gusts in the 40’s. Temperatures were warm…in the upper 30’s at l000′ and near 32 at 2000′.

Today, another warm pacific system is moving through. Overnight, between .5 and 1″ of rain has fallen from around 2000′ and below while 5-8″ of wet snow has fallen above. The Easterly winds have picked up to the 40’s mph at Sunburst ridgetop weather station with gusts in the 60’s. Through the day we are expecting to see another .5″ of rain below ~1500′ and 3-5″ of wet snow above. Ridgetop winds should remain strong, between 30-40mph from the East with stronger gusts.

On Sunday ridgetop winds are expected to remain strong and precipitation taper off slightly as we will still be in the midst of very warm moist air streaming in from the Gulf.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	34	0 (rain)	1.1	78
Summit Lake (1400′)	35	0	0	26
Alyeska Mid (1700′)	34	0 (rain)	0.72	59

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	28	ENE	31	67
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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