Sun, January 26, 2014 Turnagain Pass Avalanche Forecast

Sun, January 26th, 2014

Alpine

Above 2,500'

4 - High

Treeline

1,000'-2,500'

4 - High

Below Treeline

Below 1,000'

4 - High

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

Wet slab and wet loose avalanches remain our primary concern once again today. The snowpack is wet, unconsolidated and literally falling apart. Today is our 9th day of unseasonably warm weather and last night was our warmest yet. We hit 54F at Portage, 40F at 2,400′ on Seattle Ridge and 37F at 3,800′ on Sunburst to name a few.

We did see large natural avalanche activity yesterday and I suspect it continued during the overnight hours with the spike in temperature. Most of yesterday’s activity was in the form of wet slab or wet loose at elevations below 3,500′. The one exception was a large deep slab with a start zone near 6,000′ that is suspected to be more of a dry slab avalanche. The rundown of yesterday’s larger avalanche activity:

Raggedtop – Natural wet/deep slab. Estimated up to 5′ deep x 600′ wide, start zone ~3,500′, Southeast facing
Goat Mtn – Natural deep slab. Estimated up to 10+’ deep x 1,000′ wide, start zone ~6,000′, Crown wrapped from Southwest to South to Southeast facing
Seattle Ridge – Several wet slabs. Most were 50-200+’ wide and around 2′ deep with start zones around 2,500′ and Southeast facing.

Photo below is of Raggedtop – sent in by Andy Dietrick, Alyeska Snow Safety program

Natural activity from yesterday on Seattle Ridge

The warm temperatures and rain on snow for over a week have combined to destabilize the snowpack. Yesterday was the first clear day with no added precipitation, but the warm conditions combined with the sun and wind seemed to tip the balance. Today the clouds and rain are back but the very warm temperatures will continue to destabilize the pack.

Avalanche conditions aside, travel conditions are difficult. The snowpack is isothermal and unsupportable with a variable and breakable surface crust.

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

At upper elevations (roughly above 3,500′) where snow has been falling for the past nine days we have a deep slab avalanche problem. We have received around 6-10′ of new snow which has overloaded the weak snow near the ground in many areas. The clear skies yesterday allowed for a good look at all the large avalanche activity from the past week. Check out these observations HERE and HERE for some of the older activity.

We did have one deep slab release yesterday on Goat Mtn (mentioned above and pictured below).

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 have grown substantially during the past two weeks. With these warm temperatures cornices are likely to start falling and could easily trigger a large avalanche below.

Weather

Sun, January 26th, 2014

Yesterday’s sunny and warm weather made it feel like springtime in January. Temperatures reached the mid 50’s F at sea level and the mid to upper 30’s F on the ridgetops. There was a spike in temperature during the overnight hours. Winds continued from the East with averages in the 30-40mph range.

Today we will see clouds move in as another pulse of moisture approaches from the South. Rain below 4000′ should start falling this morning with up to .2″ accumulating through the day (2″ of snow above 4,000′). Temperatures should remain warm – mid 50’sF at sea level and mid 30’s to 40F on ridgetops. Winds continue to be strong from the East averaging ~50mph with gusts up to 80 or more.

The long term forecast is showing signs that this warm, wet weather will move out mid-week with clear, slightly cooler weather moving in.

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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