Tue, December 02, 2014 Turnagain Pass Avalanche Forecast

Tue, December 2nd, 2014

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

Wind Slabs

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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

A modest amount of new snow combined with older low density snow and steady winds out of the East/Southeast have formed wind slabs on leeward aspects. These slabs will be sensitive to human triggers and will be up to 10” in depth. Expect them to be easiest to trigger as they are forming. Keep in mind that while the predominant winds have been out of the East, wind changes direction as it interacts with terrain. Your best bet is to be on the lookout for shooting cracks in the snow, upside down snow, or surfaces that are smooth and pillowy. These are signs of recently formed wind slab. Avoiding these wind loaded areas, especially in terrain over 35 degrees will be the best way to manage this avalanche problem today.

Weather

Tue, December 2nd, 2014

A large Low pressure system centered in the Bering Sea that has made its way eastward along the Aleutians has brought with it precip and winds to the mountains around Eastern Turnagain Arm. Snowfall amounts have been greater to the West and less on Turnagain Pass. Weather station data from the Girdwood Valley is currently unavailable.

A warm front associated with this Low has brought slightly warmer air over the area this morning. Fortunately temps have remained cool enough to keep the precip in the form of snow. As this frontal boundary passes expect temperatures to cool and light snow to continue into the daytime hours.

Today we can expect another 3-5 inches of snow. Temperatures at 1,000′ will be in the low 30s F. Ridge top winds will be in the 10-20 mph range.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	25	2	.2	20
Summit Lake (1400′)	24	3	.3	5
Alyeska Mid (1700′)	n/a	n/a	n/a	n/a

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	19	E	13	30
Seattle Ridge (2400′)	21	SE	18	37

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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