Thu, March 31, 2016 Turnagain Pass Avalanche Forecast

Thu, March 31st, 2016

Alpine

Above 2,500'

3 - Considerable

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

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

Will daytime temperatures reach a season high today?

Sunny skies combined with unseasonable warm weather could push temperatures into the high 40F’s to mid 50F’s today. Last night was the second night in a row of above freezing temperatures in the mid elevation zone and rain/snow line yesterday was observed around 2500’. At treeline 4-6” of wet snow is sitting on a supportable crust where wet loose avalanches will be a concern today on slopes steeper than 35 degrees. The size will be directly proportional to the size of the terrain, and larger slopes will be more dangerous where more snow is available to entrain and pick up momentum. In the alpine where drier snow is sitting on a smooth bed surface there is more potential for moist/wet slab activity. Pay attention for rollerballs and avoid being on or under steep slopes today. The danger will increase with warming temperatures and solar impact throughout the day.

In Girdwood and Portage Valley where more snow has fallen over the last three days, expect wet loose activity to be larger. Cautious routefinding and a conservative mindset will be the best strategy for travel in the backcountry.

Avalanche Problem 2

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

The glide avalanche cycle continues without interruption. Yesterday another handful of new glide releases were identified between Girdwood and Turnagain Pass including a large glide avalanche that stopped just short of the Turnagain Arm bike path on Penguin Ridge.

In Turnagain Pass a glide crack on Seattle Ridge has been growing and is starting to threaten portions of the common uptrack. A recent glide avalanche in this location, above this glide crack occurred on 3/29 in conjuntion with a storm slab. The debris pile is quite large and runs over well-traveled terrain. This should definitely warrant concern, today’s warm temperatures will only be weakening the snowpack. Glide avalanches are completely unpredictable and could happen at any moment, avoidance is strongly recommended.

Portions of the Seattle Ridge uptrack (in orange) are in the runout of a growing glide crack on Seattle Ridge.

View of recent glide activity on East face of Seattle Ridge with a large glide crack in the foreground on Tincan SW aspect.

Additional Concern

Cornice

Cornice

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

More info at Avalanche.org

Cornices remain extremely large and perched along many ridgelines. These features deserve extra space and can break farther back than expected. Triggering a cornice will become more likely later in the day with sun and warming temperatures.

Wind slabs: In the upper alpine (above 3500’) where temperatures have remained below freezing, wind slabs remain a concern on unsupported slopes and will be more suspect during the heat of the day with warming temperatures. These wind slabs could be extra touchy where they are sitting on a stout melt freeze crust below.

Weather

Thu, March 31st, 2016

Yesterday skies were mostly cloudy and with light scattered showers throughout the region. Ridgetop winds were averaged in the 20’s mph from the East. Temperatures ranged in the 30F to mid 40F’s, and remained above freezing overnight in the mid elevation zone. Temperatures in the alpine were just below freezing yesterday and overnight.

Today skies will be mostly sunny with patches of fog. Daytime ambient air temperatures may reach the 50F’s at sea level and 40F’s in the alpine. Winds are expected to be light to moderate from the East and no new precipitation is expected today.

Tomorrow a front will move through Southcentral Alaska bringing another round of rain showers. Temperatures are expected to remain above freezing in the mid elevations and rain/snow line is expected to be around 3000′.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	39	rain	0.2	123
Summit Lake (1400′)	39	rain	0.1	39
Alyeska Mid (1700′)	36	rain	0.13	108

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	29	ENE	17	54
Seattle Ridge (2400′)	31	SE	31	59

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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