Wed, January 22, 2014 Turnagain Pass Avalanche Forecast

Wed, January 22nd, 2014

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

3 - Considerable

Below Treeline

Below 1,000'

3 - Considerable

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

The first avalanche problem that you will encounter from the trailhead is wet snow. The freezing line is reaching up to 2000 feet or higher. Water saturated snow is heavy and weaker than drier snow. This problem will be found below treeline, in terrain often considered “safer” from avalanche danger. Read more about Wet Slab Avalanches here.

Photo from January 21st showing low elevation terrain and several natural avalanches on Seattle ridge. Photo by Katie Johnston.

Avalanche Problem 2

Deep Persistent Slabs

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

More info at Avalanche.org

Above treeline we are accumulating significant snowfall through this warm storm cycle. The weak layers at or near the ground are now buried fairly deep (4-6 feet) and continue to be a problem for large and dangerous avalanches.

While we continue to have warm temperatures and snowfall, any steep terrain that could produce a dry deep slab avalanche should be avoided. We have many reports from the last 2 weeks of remotely triggered and natural avalanches on these old weak layers. The frequency of these events is decreasing, but the size is increasing as the snowpack builds.

Additional Concern

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

Above 2000 feet we will be getting more snow today. The National Weather Service is predicting up to a foot of new snow at higher elevations. With ongoing snowfall we need to wary of unstable storm snow in the top layers of the snowpack. This will be more pronounced in areas of stiff wind slab.

Weather

Wed, January 22nd, 2014

In the last 24 hours we received roughly 0.5 inch SWE (5 inches snow) at Turnagain Pass and over 1.5 inches SWE (15 inches snow estimate) at Alyeska. Wind was strong yesterday morning, with gusts into the 90s mph, but tapered down to the 30s and 40s for much of yesterday. Temperatures are consistently warm, in the 40s F at sea level and only reaching freezing (32 F) near 2500 feet elevation.

Today, we have another pulse of moisture headed our way. Roughly an inch of water is expected today, with another 1/2 inch tonight. Snow line will be near 2000 feet. Wind is from the southeast from 52-65mph.

This pattern is expected to continue the rest of the week until Saturday when the first break in the weather appears in the forecast.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
11/27/23	Turnagain	Avalanche: Tincan Ridge	Schauer/ Stiassny Forecaster
11/26/23	Turnagain	Observation: Road report: Slide with dirt on Repeat offender	Anonymous
11/26/23	Turnagain	Observation: Pete’s North	Ben Sullender
11/25/23	Turnagain	Observation: Tincan trees	John Sykes Forecaster
11/21/23		Observation: Spokane Creek	John Sykes Forecaster
11/20/23	Turnagain	Observation: Sunburst	Anonymous
11/19/23	Turnagain	Observation: Magnum – PMS Bowl	Schauer/ Cullen/ Jonas Forecaster
11/19/23	Other Regions	Observation: Sunnyside/Penguin	Jose Ramos-Leon
11/19/23	Turnagain	Observation: Eddies	Andy Moderow
11/19/23	Turnagain	Observation: Cornbiscuit	Anonymous

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