Wed, December 09, 2015 Turnagain Pass Avalanche Forecast

Wed, December 9th, 2015

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

1 - Low

Below Treeline

Below 1,000'

1 - Low

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

The sustained winds from Monday night into Tuesday morning changed the snow conditions in the Alpine. Observers reported pockets of wind slab and scoured ridgelines. While traveling today look for areas that have had recent loading and avoid stiff snow in steep terrain. Watch for cracking and listen for hollow sounds that could indicate the shallow wind slabs may be reactive.

The Turnagain Pass area received an inch of snow yesterday and more is forecasted for today and tonight. Pay attention to changing conditions and expect avalanche danger to increase as we load up the weak surface snow that formed during the period of high pressure and low danger.

What has changed or is changing? These should be the questions in the next few days. Look for Red Flags: recent avalanches, cracking, whumfing, recent snowfall and signs of recent wind. These signs of instability indicate heightened avalanche danger and the need for cautious travel behavior.

Good travel habits, such as exposing one person at a time, watching your partners, grouping up in safe zones and having an escape route planned are, as always, key ways to minimize risk.

Wind effect and rime crust on Big Chief. Photo: Billy Finley

Weather

Wed, December 9th, 2015

The low in the Gulf is impacting the forecast area today. Skies will be cloudy with snow showers likely throughout the day. New snow accumulation of 1 to 3 inches is possible. Highs will be in the mid 20Fs to upper 30Fs. Winds will be variable from the North.

Snow will continue tonight with an addtional 3-6 inches possible. There is more unsettled weather and snow on tap for later in the week as the pattern continues to push a series of lows into the region.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	27	1	.1	23
Summit Lake (1400′)	25	0	0	11
Alyeska Mid (1700′)	24	0	0	18

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	26	NE	7	22
Seattle Ridge (2400′)	26	NE-SE	7	13

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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