Sun, February 14, 2016 Turnagain Pass Avalanche Forecast

Sun, February 14th, 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

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

Although there are many human triggered avalanche concerns out there, glide avalanches remain the primary concern due to their destructive nature. This season is turning out to be a season where mapping glide cracks and limiting/avoiding time under them is just part of the game. The most recent glide we know of that has released at Turnagain Pass was 3-4 days ago on the Eddies ridge.

Photo: Glide avalanche on Eddies, released sometime late 2/10-early 2/11.

Avalanche Problem 2

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

While many folks are waiting for the skies to clear and temperatures to cool off before venturing into the mountains, it has been snowing a bit and blowing quite a bit over the past several days in the Alpine – above 2,500′. Specifically, between 1 and 2 feet of new snow has fallen over the past 3 days with winds in the 20-25mph range on the ridgetops from the East. Due to lack of travel and visibility in these areas we don’t have first hand data as to how the wind driven snow is bonding, if cornices are falling and the like. However, we know from past experience that this warm snow is quite sticky and stabilizes relatively quickly. This will most likely be the case for today and into the week. Nonetheless, things to watch for at the upper elevations:

Wind Slabs: Steep slopes that have been, or are currently being, loaded with wind deposited snow are suspect for triggered a wind slab avalanche. These could be 1-2′ or more thick. Watching for cracking in the new snow and jumping on small terrain features and test slopes can be good ways to see how well slabs are bonding.

Cornice Falls: GIVE CORNICES a wide berth!! these are likely to be tender with the warm temperatures and could be deadly if you were to take a fall off a ridgeline with one. Also, similar to glide avalanches, limit time spend under cornices.

*Shallow snowpack zones: South of Turnagain Pass and the Summit Lake area. These areas have old weak layers in the snowpack that, if loaded with enough snow/wind, could produce a large avalanche. This is something to keep in mind if you are headed to these zones this week with the expected clear skies.

Additional Concern

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

It will be another moist day out there. Temperatures dipped to 32F at 1,000′ overnight and it is lightly snowing at the Pass this morning, but temperatures are forecast to climb up again today. Rain up to 1,500′ is possible and we have .2-.4″ of it with 2-4″ of snow in the Alpine. The snow at the mid-elevations is wet and saturated. These are prime conditions for triggering a wet loose avalanche on steep slopes. To initiate a wet loose slide the slope has to be quite steep, but once it starts moving can gain a lot of momentum and run to valley bottoms. Steering clear of steep slopes with ‘boot-top’ wet snow is an avalanche forecaster’s rule of thumb.

Weather

Sun, February 14th, 2016

Partly cloudy skies with some blue holes covered the region yesterday. Light precipitation fell, adding ~.2″ of rain below 1,000′, and was mostly centered around Turnagain Arm. Around 2″ of snow has fallen in the past 24-hours above 1,500′. Temperatures dropped to 32F at 1,000′ and are holding steady in the mid 20’s on the ridgelines. Winds have been sustained in the moderate range with averages 20-25mph from the East along the ridgetops.

For today, we are expecting mostly cloudy skies along with light precipitation. Between .2-.4″ of rain is expected to fall below 1,500 with 2-4″ of wet snow above this. The rain/snow line is currently around 800′ this morning but looking to climb a bit through the day. Ridgetop winds are expected to remain moderate from the East, 20-25mph. Temperatures remain warm, mid 30’s F at 1,000′ and mid 20’s F at 3,500′.

For Monday we remain in this unsettled warm and showery pattern, but for Tuesday we could see cooler temperatures and a real break in weather.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	32	3	0.3	104
Summit Lake (1400′)	34	0	0	30
Alyeska Mid (1700′)	33	1.5	0.15	84

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	24	NE	22	54
Seattle Ridge (2400′)	27	–	–	–

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
10/27/24	Turnagain	Observation: Tincan	Michael Kerst
10/21/24	Turnagain	Observation: Turnagain Pass Road Observation	Trevor Clayton
10/19/24	Turnagain	Observation: Tincan – Below Todds Run	Andy Moderow
10/18/24	Turnagain	Observation: Taylor Pass	Eli Neuffer
10/15/24	Turnagain	Observation: Tincan Common	John Sykes Forecaster
10/14/24	Turnagain	Avalanche: Tincan	CNFAC Staff
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

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