Wed, January 07, 2015 Turnagain Pass Avalanche Forecast

Wed, January 7th, 2015

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

1 - Low

Below Treeline

Below 1,000'

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

A large wind event last week has left the slopes scoured on ridges with hard-pack snow conditions above 2500’. This densely settled snow combined with time has added to the strength of the slab by making it supportable and difficult to trigger a buried weak layer below. In general normal caution is advised with the exception of very steep slopes.

Some uncertainty still exists in terrain steeper than 40° and where the snowpack is thinner. The current structure of the snowpack is a 1-3’ slab sitting on a weak layer, and there remains some potential on specific features for a slab to propagate. Avoid shallow areas of the snowpack, especially near rocks and steep convex rollovers.

In places like Girdwood and Summit Lake where the snowpack is thinner– triggering a layer of buried surface hoar or facets could be more likely. In these areas consider keeping your slope angles even lower.

If you choose to ski a steep slope identify features of concern and the consequences below you. Practice safe travel techniques like exposing one person at time, communicating route decisions, and always be aware of groups above and below you.

Over the last week new surface hoar growth has been widely documented and something to be aware of heading into our next warm storm cycle. A big thanks to everyone submitting observations this winter!

Surface hoar formation this week at 2000' in the Girdwood Valley

Photo Credit: Kyle Bates

Weather

Wed, January 7th, 2015

Over the last few days skies have been clear and an inversion has brought single digit F temps to valley floors with ridgetops in the mid 20’s F. Overnight Eastern winds have been light with no new precipitation.

Temperatures are expected to increase into the low 30’s F today as a low-pressure system approaches from Southeast Alaska. Winds will be out of the East 10-20mph. We may see a trace of new snow tonight, but it is more likely to be in the form of freezing rain at sea level.

Overnight and into tomorrow warm air will continue to override the cool surface air in Southcentral Alaska increasing the likelihood of freezing rain at lower elevations. Temps could be as high as the mid 30’s F at sea level with lows in the 20’s F at ridgetops. Winds are expected to be moderate from the East.

It is uncertain how much precipitation this warm air mass could bring, but it looks like lower elevation temperatures will remain warm (mid-high 30’s F) into the weekend.

PRECIPITATION 24-hour data (6am – 6am)

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	24	0	0	33
Summit Lake (1400′)	12	0	0	6
Alyeska Mid (1700′)	22	0	0	25

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	23	E	7	30
Seattle Ridge (2400′)	23	Var	8	29

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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