Wed, March 12, 2014 Turnagain Pass Avalanche Forecast

Wed, March 12th, 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

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

The storm snow that makes up our primary concern started falling on Monday. It tapered off substantially yesterday and transitioned to rain below 1000 feet. All told, more than 2 feet of new snow fell from this storm. Combined with a lot of wind, we have scoured areas between heavy wind loading.

Yesterday we were finding the storm snow would break easily on the new snow/old snow interface. This is the old surface layer about an inch above the late February crust. This is a very easy interface to identify, no need to pull out the shovel, just dig in with your hand to find it. Any avalanches today are likely to break a little above that crust, taking 2 feet of storm snow or greater amounts in wind loaded areas. Areas with now buried surface hoar may behave even worse with a persistent weak layer involved.

I’ll mention that avalanche activity yesterday seemed a bit sluggish – initiation was slow and avalanches were somewhat small in size for the amount of snow we got. This doesn’t mean much in terms of travel advice… It’s still an easy call when managing today’s problem. A lot of new snow on top of a crust with sporadic buried surface hoar – requires conservative travel in the backcountry.

Avalanche Problem 2

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

Below 1000 feet we did get rain at the later half of this storm. The lower you go, the more rain we got. This isn’t a big concern, just keep in mind that lower elevations have a water saturated surface layer.

Weather

Wed, March 12th, 2014

The recent storm is the big news. Storm totals listed below. Numbers are 48 hour snow totals. Keep in mind that the snow is settling and temperatures increased during the storm, transitioning to rain at lower elevations.

Girdwood midway – 26″ (2.25″ water equivalent)

Turnagain Pass – Center Ridge – 25″ (2.2″ water equivalent)

Summit Lake – 12″ (1″ water equivalent)

Wind blew hard during the peak of the storm, which caused visually evident scouring of ridges. Max gusts were recorded up to 114mph at ridge tops. That wind diminished yesterday.

Today will bring a short break in precipitation intensity. Snow and rain showers are expected throughout the day with an inch of accumulation. Wind is increasing through the day as another weather front approaches.

Tonight and tomorrow will bring another storm similar to the last one. Predicted snow totals for tonight and Thursday are 14-24 inches. There is a high wind warning in effect 2am to 8am Thursday for Turnagain Arm and Portage.

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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