Tue, December 01, 2015 Turnagain Pass Avalanche Forecast

Tue, December 1st, 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

Upper elevation slopes that harbor dry and crust-free snow after Thanksgiving’s onslaught are the areas most suspect for triggering an avalanche. These slopes are also where most of us are looking to ride and sit at elevations over 2,500′. If you are headed out today (we may see clearing skies…?) there are two things to keep in mind:

1- A bump in wind from the Northeast last night may have created shallow wind slabs just off the ridgelines. These should be easy to identify by keeping an eye on the surface texture and looking for areas of stiff wind deposited snow. Quick hand pits can help assess the reactivity of any slabs found.

2- In general we have little information for terrain over 3,000′. What we do know is 2-4′ of ‘Thanksgiving’ snow sits on top a variety of old surfaces, one of these being a layer of small facets near the ground. With the lack of natural avalanche activity during last week’s storm cycle and snow pits showing stable snow at 3,000′, plus four days now since the end of the storm, all signs point to a stabilizing pack. However, caution is still warranted as an avalanche breaking in the facets near the ground would be large. Don’t forget your safe travel practices if venturing onto steep committing terrain, namely, only expose one person at a time and watch your partners carefully.

Terrain below 2,500′:

Rain that fell last week has now frozen and a crust exists under 2-6″ of new snow; dust-on-crust riding conditions. Freezing of the snowpack has stabilized these lower elevations. We did get a report yesterday of a large avalanche that was spotted in the Tincan Trees area – suspected start zone is above treeline and under the CFR ridgeline (2,500′). The slide is suspected to have occurred sometime late Sunday or early Monday. If you have any information about this avalanche please let us know!

Photo below of the CFR avalanche (credit: Ray Koleser).

Weather

Tue, December 1st, 2015

Cloudy skies covered the region yesterday and instability showers dropped a few more inches of snow above 1,000′; light ‘freezing’ rain at sea level. Winds were light from the NE and temperatures remained mild.

Overnight, winds picked up slightly from the Northeast with averages in the 10-20mph range and a peak gust at Sunburst of 41mph. These have decreased this morning. Temperatures continue to be mild (ridgetop mid-20’s F), yet cooler air has just begun filtering in from the Northeast. We may see a few more instability showers again today intermixed with clearing skies.

Another shot for a few inches of snow will come tomorrow as a pulse of moisture is pushed in by a low-pressure system in the Gulf.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	29	2	0.2	24
Summit Lake (1400′)	30	0	0	10
Alyeska Mid (1700′)	32	2	0.1	17

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	24	ENE	13	41
Seattle Ridge (2400′)	24	N/A	N/A	N/A

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
10/27/24	Turnagain	Observation: Tincan	Michael Kerst
10/21/24	Turnagain	Observation: Turnagain Pass Road Observation	Trevor Clayton
10/19/24	Turnagain	Observation: Tincan – Below Todds Run	Andy Moderow
10/18/24	Turnagain	Observation: Taylor Pass	Eli Neuffer
10/15/24	Turnagain	Observation: Tincan Common	John Sykes Forecaster
10/14/24	Turnagain	Avalanche: Tincan	CNFAC Staff
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

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