Mon, April 01, 2013 Turnagain Pass Avalanche Forecast

Mon, April 1st, 2013

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

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

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

When figuring out how weather influences avalanches, we need to look at three main factors: precipitation, temperatures, and wind. Today temperatures will be the factor to pay the most attention to. Closely related to temp, and requiring your attention today, will be the sun. We have begun a melt freeze cycle around here. While this is a trend that generally encourages the stabilization of the snowpack, there is a critical period during the day when the snowpack de stabilizes. It’s during these times when it is important to move off of terrain to avoid avalanches. Paying attention to the surface snow and how deep your sled or skis penetrate is the best tool for recognizing this hazard. The further you are sinking in, the greater the volume of an avalanche will be. Looking for rollerballs and pinwheels is another way to anticipate wet avalanche activity. We received mutlple reports of natural wet avalanches in the mid and lower elevations yesterday. Both the sun and ambient air temp will help to weaken the snow surface and allow for humans to trigger low to medium volume wet loose and potentially wet slab avalanches today.

Avalanche Problem 2

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

These giant masses of snow dangling above many South, Southwest and some West facing slopes will be tested by the sun and warm temperatures today. Today is not your day to tempt fate. While it will be easy to figure out what is happening when you are near cornices (i.e. on ridgelines), it is a whole other story when that cornice is a thousand or more feet above you. When traveling up valleys today it will be best to treat any slope receiving direct sunlight with suspicion. Having groups spaced out to minimize exposure and not stopping directly below cornices, even if they seem far away, will be your best way to manage this problem today.

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Additional Concern:

(Old) Wind Slabs

There remains a chance for finding a lingering pocket of wind slab in steep upper elevation starting zones today. Wind slab avalanche activity peaked on Friday/Saturday, over two days ago, and remains a (lower level) concern.

Weather

Mon, April 1st, 2013

In the past 24 hours the mountains around eastern Turnagain Arm have experienced warm temperatures, with the Sunburst weather station (3,812′) averaging 22.6 degrees F and the freezing level climbing to the ~2,500′ elevation. Winds at Sunburst have been light, averaging 3mph out of the East with gusts to 12mph. Precip ended in the morning hours yesterday and totaled 6″ of snow in the Girdwood Valley and just a trace on Turnagain Pass.

Today expect a similar day to yesterday, with rising temperatures and sunlight being the main weather factors to incorporate into your terrain selection. Temperatures at 1,000 feet will be in the 35-40 degree range. Winds out of the north will be light, in the 5 to 10 mph range and will minimally help to lessen the effects of the sun and warm temps today.

The extended outlook calls for continued mild temperatures, sunshine and no precip until the end of the week.

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Wendy will issue the next advisory tomorrow morning, April 2nd.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
04/16/24	Turnagain	Observation: Cornbiscuit	Krueger / Matthys Forecaster
04/15/24	Turnagain	Observation: Taylor Pass	John Sykes Forecaster
04/15/24	Turnagain	Observation: Seward Highway – Tern Lake to Portage	Joel Curtis
04/14/24	Turnagain	Observation: Sunburst	T. Olsen-Lund, R. Sullivan I. Adams
04/14/24	Turnagain	Observation: Turnagain Pass Snomo	K. Gallaher
04/13/24	Turnagain	Observation: Spokane Creek	Everet Megli
04/11/24	Turnagain	Observation: Tincan	John Sykes Forecaster
04/10/24	Turnagain	Avalanche: Seattle Ridge	Schauer/ Keeler Forecaster
04/10/24	Turnagain	Observation: Cornbiscuit South Face	Todd Kelsey
04/10/24	Turnagain	Avalanche: Tincan	N. Dumont J. Carlberg

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