Tue, March 11, 2014 Turnagain Pass Avalanche Forecast

Tue, March 11th, 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

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

Well, it sure looks like winter is taking a 3rd stab at coming to Southcentral Alaska this season. After a high and dry couple of weeks (not to mention our thin snowpack that sits roughly ~40% of average) we are now entering into a stormy weather pattern. Due to the meager snow year, we have been plagued with several weak layers in the snowpack. The most concerning one for this storm cycle is the preexisting snow surface. Before snow began to fall yesterday, we had a mix of 1-2″ of faceted snow and surface hoar sitting on a variable 1-4″ crust (for a better look at this check out Fitz’s video from Sunday). This is a classic weak layer and bed surface combo that now has a 2-3′ slab on top.

During our field day yesterday only 6-8″ of snow had fallen yet we were able to find and easily trigger a slab avalanche 10-14″ thick on a wind loaded slope (photo below). This is a look at things to come. With up to 2′ of storm snow currently and more on the way, slab avalanches up to 2-3′ deep, or deeper in wind loaded locations, are likely. Additionally, the weak snow underneath adds to the potential for slabs to propagate around terrain features and possibly break where you may not expect them to.

Photo: Human triggered slab avalanche in the Tincan Trees, ~1,700′ elevation, West facing.

For today, avoiding avalanche terrain is recommended due to the high volume of heavy snow sitting on a weak surface. Again, avalanches have the ability to propagate wider than expected and can be triggered remotely; this includes from below. Even “in the trees” avalanche terrain exists and there are dangerous terrain traps under small steep slopes/cliffs.

Weather

Tue, March 11th, 2014

Since 7am yesterday, heavy snowfall has deposited 20+ inches in the mountains around the Eastern Turnagain Arm. Winds were strong from the East with this “Chugach Special” and averaged in the 50-70mph range with a max gust at the Sunburst station of 114mph! Snowfall has tapered off overnight along with the Easterly winds, which are now blowing 20-30 with gusts to 50mph. The rain/snow line crept up from sea level to around 1,000′ overnight along with the ridgetop temperatures which have risen from ~20F to the mid 20’sF.

Storm totals (7am yesterday to 6am today – check this out on the Turnagain Pass snow stake loop!):
Turnagain Pass, 1880′ elev – 20″ snow (1.6″ water equivalent)
Girdwood Valley, 1700′ elev – 21″ snow (1.6″ water equivalent)
Summit Lake, 1400′ elev – 8″ snow (.6″ water equivalent)

An additional 7-10″ of snow (~.7″ water) is on tap today as the remnants of the large low pressure system continues to spin South of the Kenai pushing moisture our way. The Easterly winds are also expected to bump back up today into the 50mph range with higher gusts. Temperatures are expected to remain in the mid 20’sF on the ridgelines and the rain/snow line hover near 1,000′.

Looking forward: The weather models are showing a break in storms late tonight through Wednesday before another – and very similar – low pressure tracks through Thursday/Friday. This should bring another decent shot of precip our way.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
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
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

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