Mon, November 30, 2015 Turnagain Pass Avalanche Forecast

Mon, November 30th, 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

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

With an onslaught of warm, powerful storms since early last week we saw a peak in natural avalanche activity on Friday/ Saturday with rain up to 2500’ and 100+ mph winds through Turnagain pass. Overall the snowpack will continue to gain strength and adjust today with slightly colder temps and a lack of active weather but areas of instabilities may exist. Above 2500’ where the snow has stayed dry, steep leeward slopes may be harboring pockets of wind slab that could be susceptible to a human trigger. Shooting cracks, whumphing or a hollow drum-like feel to the surface are clues that you’ve stepped onto a wind slab. The snowpack is still quite shallow out there. Getting knocked off your feet from even a small avalanche will translate to an unpleasant ride.

General snowpack structure in the mid-elevations, Turnagain pass. Total height of snow here is about 28″.

Additional Concern

Announcement

Announcement

More info at Avalanche.org

Though we’ve seen a lack of avalanche activity since the peak of the storm post-Thanksgiving, keep in mind we have had 4+” of water over the last 5 days in the eastern Turnagain arm area. This translates to more than 4’ of snow in some upper elevation areas, potentially overlaying weak snow from our cold snap earlier in November. With a lack of information from periphery areas such as the Girdwood Valley, it’ll be prudent to approach any steep, upper elevation terrain with added caution today.

Weather

Mon, November 30th, 2015

Yesterday provided a reprieve from the rain with only light, intermittent showers across eastern Turnagain arm. Temperatures hovered around 36F all day at 1,000′ while ridge tops cooled slightly to the mid-20’s. Ridgetop winds were less than 20 mph out of the east.

Today we can expect patchy fog and mostly overcast skies. Temperatures appear to be dropping slightly to the low 30’s at 1,000′ and we can expect a few lingering showers to deposit 1-2 € of snow at and above ~1500′. Winds will be light out of the East.

Expect an overall decrease in temperatures (return toward normal) and more unsettled, active weather through the week as the next low pressure moves into our region.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	29	2	.2	22
Summit Lake (1400′)	27	1	.1	10
Alyeska Mid (1700′)	32	1	.06	16

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	23	ENE	11	32
Seattle Ridge (2400′)	26	N/A	N/A	N/A

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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