Fri, February 05, 2016 Turnagain Pass Avalanche Forecast

Fri, February 5th, 2016

Alpine

Above 2,500'

4 - High

Treeline

1,000'-2,500'

4 - High

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. Dangerous avalanche conditions.	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

Storm Slabs: Today is day 3 of a warm and wet storm that has dumped 3″ of water (2-4′ of new snow in the upper elevations) in the advisory area. This has fallen on old weak (faceted) snow resting on a rain crust. The storm snow was not bonding well to this yesterday and was reactive in tests, whumpfing, cracking and became increasingly ‘slabby’ throughout the day. Because the crust/facet combo extends from 1000′ to approximately 3000′ avalanches could be very large and connected. The storm last week stabilized quickly. It is important to recognize the character of this set-up is very different and could elevate the hazard through the weekend. Travel in avalanche terrain is not recommended today.

Wind Slabs: Stormy conditions continue to make wind slabs a concern for the upper elevations. Sustained 30-40 mph ENE winds, gusting in the 70s yesterday, have made triggering a wind slab +3’ thick likely on wind loaded and cross-loaded features. Below 3000’ these wind slabs are sitting on the old snow/crust combo and may propagate further than expected.

Cornices: Cornices will be unstable today and may release naturally. These features have been tender over the last week and now have the added stress of high winds and new snow. These backcountry bombs can easily trigger a slab below and are another reason to avoid travel in avalanche terrain today.

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 Snow: Wet snow is sitting on a slick crust in the mid elevation band. Rain to 1600’ will be lubricating this poor interface making wet avalanches possible in the mid elevation band. This hazard will be especially dangerous under big open slopes and in terrain traps like gullies or abrupt transitions where an avalanche from above could have high consequences. Natural activity is possible in steep channeled terrain and will likely entrain wet snow. Areas like lower Seattle Ridge should be avoided.

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

Warm temperatures, rain and wet snow continue to add weight and stress to glide cracks throughout Turnagain Pass. These unpredictable hazards are widespread in steep terrain between 1000’ to 2500’ and can release without warning. Today’s limited visibility will make it challenging to identify existing glides, and is an added reason to avoid being in the mountains today.

Weather

Fri, February 5th, 2016

Yesterday was a storm day. Rain fell up to 1500′ and the advisory area recieved another 1.5″ of moisture. Snowfall was up to an 1″/hr for much of the day with over 1′ of new snow falling in the last 24 hrs. Since Tuesday evening 3″ of water and +3′ of snow have fallen. Winds were from the ENE blowing 30-40 mph gusting into the 70s. Temperatures were in the 30Fs at 1000′ and the mid-20Fs at 3000′.

Rain and snow showers are forecasted to continue today with an addtional 0-4” of snow and rain up to 1600′. Winds will be Easterly 15-25 mph and temperatures will be in the 30s.

Showers continue this evening tappering off overnight with a short break before the next Low impacts the area Sunday.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	31	10	1.7	114
Summit Lake (1400′)	32	3	.3	31
Alyeska Mid (1700′)	32	9.5	1.3	84

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	24	ENE	34	76
Seattle Ridge (2400′)	26	n/a	n/a	n/a

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
11/16/23	Turnagain	Observation: Tincan Common	William Finley
11/14/23	Turnagain	Observation: Sunburst/Magnum	Adrian Beebee
11/14/23	Turnagain	Observation: Seattle Ridge	Schauer/ Creighton/ Ellis Forecaster
11/13/23	Turnagain	Avalanche: Tincan Trees	Eeva Latosuo
11/12/23	Turnagain	Observation: Sunburst	Schauer/ Creighton/ Nave Forecaster
11/12/23	Turnagain	Avalanche: Goldpan – avalanche	Mike Records
11/11/23	Turnagain	Observation: Tincan Common	Andy Moderow
11/11/23	Turnagain	Observation: Taylor Pass – Sunburst	Wadsworth / Stwertka
11/10/23	Turnagain	Observation: Tincan	Andrew Schauer Forecaster
11/10/23	Turnagain	Observation: Tincan Trees	Michael Kerst

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