Fri, March 25, 2016 Turnagain Pass Avalanche Forecast

Fri, March 25th, 2016

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

3 - Considerable

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

They keep going and going and going… The glide avalanche cycle in the advisory area continued yesterday. Observers saw new glide avalanches; new cracks appearing and existing glide cracks growing. These are on all aspects in the mid-elevation band (1000′-2500′). Please avoid spending any time underneath glide cracks. The glides are taking over the landscape. Poor visibility today may make it harder to see where they are. It is important to note that Seattle Ridge is littered with them and it is hard to travel without being in the line of fire.

Glide crack and avalanche activity on Seattle Ridge yesterday.

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

Yesterday temperatures reached the 47F at 1880′, and for the fifth night in a row the mid elevation zone remained above freezing with rain falling overnight. Wet loose natural activity was observed yesterday on all aspects. Observers in the Girdwood Valley reported it being very easy to trigger loose wet snow avalanches and once moving that they were quickly building mass and momentum.

Today’s weather forecast is for rain showers that will add moisture to an already wet snowpack and may cause natural wet loose avalanches. In addition, if the sun pokes out at all, it could also be a trigger for natural activity.

Today a skier or snowmachiner triggering a wet loose avalanche will be likely below 2500’ on slopes steeper than 35 degrees. Wet avalanches once initiated can entrain more snow rapidly and are very hard to get out of. They can be particularly hazardous if they push you into a terrain trap and bury you deeply. If your skis or snowmachine are sinking deep into wet snow this is an obvious clue that the snow is unstable. Stick to low angle terrain and avoid runout zones where avalanches from above may catch you.

Wet loose activity on the West Face of Lipps.

Additional Concern

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

Wind slabs and Cornices:

There may be some new snow and wind today creating new tender wind slab and/or adding weight to old lingering wind slabs and enormous cornices in the Alpine. Watch for cracking in steep wind-loaded areas and avoid travel on or under cornices. Today’s continued warm temperatures will make cornices more likely to fail.

Weather

Fri, March 25th, 2016

Yesterday was partly cloudy with light to moderate easterly winds. Temperatures were in the low 30Fs @ 3000′ and the 40Fs @ 1000′. There were a few light rain showers. The clouds rolled in overnight and brought rain to the advisory area up to appoximately 2000′.

Today will be mostly cloudy with rain and snow showers throughout the day. 0-2″ of snow possible (.2″ of h2o). Temperatures are forecasted to be in the 40Fs at 1000′ and low 30Fs @ 3000′. The sun may shine through at some point. Winds will be 15-25 mph from the southeast with locally higher gusts.

Saturday may bring a break in the showers as a ridge moves over the area before another storm impacts the forecast region into next week. Stay tuned for the temperatures and precipitation type associated with the system. The NWS forecast used the words “somewhat murky forecast for south central” in the discussion last night.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	39	rain	.4	126
Summit Lake (1400′)	37	rain	.5	41
Alyeska Mid (1700′)	36	rain	.2	104

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	29	ENE	25	55
Seattle Ridge (2400′)	30	SE	20	41

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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