Wed, January 29, 2014 Turnagain Pass Avalanche Forecast

Wed, January 29th, 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

Without any reported natural avalanche activity again yesterday we have reason to believe that after a solid 12 days of rain and unseasonably warm temperatures the snowpack is adapting to this new normal. Natural avalanches will be less likely today but given the results from DOT and AKRR avalanche mitigation work along the Seward Highway yesterday, the faceted layer at the bottom of the snowpack is still proving to be quite reactive given the right (or large enough) trigger.

We still need several days and nights in a row with below freezing temperatures to really lock up the snowpack in these mid-elevations (1800’ – 3500’) where the vast majority of avalanche activity has occurred during this warm-up.

Below 1800’ our snowpack has literally deflated, losing perhaps 75% or more of its mass since January 15^th due to rain and unseasonably warm temperatures. When travelling through this elevation band, avoid avalanche runout zones such as funneled terrain.

Peterson Creek path @ MP 84. Helicopter bombing triggered wet slab avalanche running on basal facets. Debris ran all the way to sea level even though the snow line is at approximately 1,000′.

Photo: Kevin Wright

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

Broken skies yesterday gave us a few brief glimpses of the high peaks around the Girdwood Valley. From the binoculars, winter appears to exist at these upper elevations (above about 4,000’) where the snow surface appears thick and plastered onto steep terrain in true Chugach fashion. With evidence of a deep slab avalanche cycle over the weekend there is still reason to be suspect of high elevation terrain as the deep slab problem is not one to heal itself quickly. If travelling into these upper elevations pay attention to what’s above you, including looming cornices which if released can act as a trigger large enough to initiate an avalanche.

Weather

Wed, January 29th, 2014

Over the last 24 hours temperatures have continued a slow and steady decline at ridgetop locations with both Seattle Ridge and Sunburst maintaining temperatures below 32 degrees. Temps at sea level remained above average in the low to mid- 40’s. Winds continued out of the east averaging around 20mph. Precipitation was pretty limited with just a trace of rain and snow falling throughout the day. Rain/ snow line was around 2,000′ yesterday.

Temperatures today look to be in the mid-30’s at 1,000′ cooling to mid to low 20’s at ridgetop locations. We may see just a trace of precipitation today (with snow falling around 1,000′) as the current low pressure weakens and moves through our area. Winds will continue from the southeast in the 17-31mph range.

The trend for overnight and into tomorrow appears to be a building high pressure which should dry us out for a day or two though temperatures do not appear to drop dramatically.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
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
04/10/24	Turnagain	Avalanche: Seattle Ridge	Schauer/ Keeler Forecaster
04/10/24	Turnagain	Observation: Cornbiscuit South Face	Todd Kelsey
04/10/24	Turnagain	Avalanche: Tincan	N. Dumont J. Carlberg

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