Fri, November 29, 2013 Turnagain Pass Avalanche Forecast

Fri, November 29th, 2013

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

Ah, the pesky northwest winds. These rolled in Wednesday night and blew much of the 3-6″ of new light snow either back to the atmosphere (sublimation) or into hard and stiff wind slabs. As can be seen in the picture below, the snow surface is a mixed bag of wind effect above treeline.

Photo: Seattle Ridge ~2,500ft

There were a few natural wind slab avalanches seen that likely released Wednesday night along with the onset of the wind. These were fairly small in size and on easterly aspects above 3000ft. The largest slab seen was on a SE facing slope around 3500ft – photo below. This is a classic catchment zone for the predominant NW flow.

For anyone getting out into the Alpine today, watch for areas of recent wind deposited snow and cracking around you. The slabs we found yesterday were scattered near ridgelines and stiff and stubborn – meaning hard to crack and release. However, in steep terrain these could pose a real issue by letting a person get out onto the slab before it releases. Even small slabs can be a problem if they knock you off your feet and down a steep rocky chute for example. Yet, most of us are waiting for more snow before getting into these places.

Weather

Fri, November 29th, 2013

Cold, clear and windy describes both yesterday’s weather conditions and as well as today’s. Over the past 24 hours temperatures continue to hover in the single digits in most locations while they are dipping down to the minus single digits above 3,000ft. We should not see much of a warm up, if any, in temperature throughout the day. The frigid Northwest winds have not backed off a whole lot and are forecast to continue to blow in the 10-15 mph range with gusts in the 30’s. It should be a bright sunny day however!

Our next shot of snow is on the distant horizon. There is a system forecast to move through for the middle of next week. As to what track it takes and how much snow we might get, it is still too far out to tell.

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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