Sun, January 05, 2014 Turnagain Pass Avalanche Forecast

Sun, January 5th, 2014

Alpine

Above 2,500'

4 - High

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

Persistent Slabs

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

More info at Avalanche.org

Our tenuous snowpack is on the brink. During the past 24-hours we have added yet another load (1-1.5” of water equivalent). This may not sound like much for a coastal climate, but our snowpack has such a weak foundation that 12-14+” of new snow will impact it. The slab that overlies the weak faceted snow near the ground was around 2′ deep yesterday and today will be around 3′ deep.

There were multiple medium to large human triggered avalanches Friday. One of these claimed the life of a dog. A preliminary write-up can be found HERE. A party of a few skiers was able to initiate a collapse on a broad ridge and trigger 4 avalanches 50-300’ away simultaneously. Additionally, two large avalanches were remotely triggered in Seattle Creek. These avalanches are breaking in the weak snow near the ground and taking most of the snowpack along with it. The character of remote triggers and close to full depth slides is a scary combination. With this new load and warming temperatures expect avalanches to be easier to trigger and larger today.

Below is an image of the large Tincan avalanche from Friday. (Photo: Kevin Wright)

Avalanche Problem 2

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

Instabilities within the new storm snow will be prevalent today but these issues are trumped by the bigger problem at hand – mentioned above. The new snow came in with both strong East winds and warming temperatures. This means there are both wind slabs from the wind and soft slabs from the upside-down nature of the storm. These new snow issues are in the top 1-2’ of the pack and will result in avalanches around 1-2’ deep.

Weather

Sun, January 5th, 2014

A wet, warm and windy storm has moved through the Easter Turnagain arm beginning yesterday morning and is now exiting. During the past 24-hours we have seen 12-14 € of snow (likely more at the upper elevations) and rain below 500ft. Winds have been consistently strong from the East averaging 40mph with gusts up to 84mph. Temperature has been in the mid 20’s F on ridgetops and increased to the upper 20’s overnight with sea level temperature in the mid to upper 30’s.

Storm totals to date (beginning 7am yesterday, Friday 1/4):

Girdwood Valley (2800ft) €“ 14 € snow (1.28 € water)
Turnagain Pass (1880ft) €“ 12 € snow (1 € water)
Summit Lake (1400ft) €“ 2 € snow (.1 € water)

Today snowfall will taper off with a chance for 1-4 € additional accumulation. However, the strong East wind will remain with averages near 40mph. Temperature also remains warm €“ upper 20’s on the ridgetops and low 30’s at 1,000′.

For tomorrow, a smaller system develops that could add 4-8 € of snow. This looks to also be a warm and windy event. Stay tuned.

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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