Tue, March 03, 2015 Turnagain Pass Avalanche Forecast

Tue, March 3rd, 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

Persistent Slabs

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

More info at Avalanche.org

Weak snow that has been buried for 3 weeks continues to lurk 1-2 feet below the surface. This layer has gained significant strength in that time. Bonding between the “late January” facets and overlying slabs has improved to the point where it has become difficult to trigger an avalanche on this layer. Some intermediate weak layers can be found in isolated locations and are buried about 1 foot deep. Slabs resting on these layers are also generally difficult to trigger. Tests have been showing propagation potential on the decline, but it is still possible for an avalanche, if triggered, to propagate across portions of slopes.

Despite these improving trends it is still important to treat steep and complex terrain with suspicion in the Alpine. Today it will be important to follow good travel protocol. Assess the terrain you are on and minimize your exposure accordingly. Avoid trigger points on terrain over 35 degrees, travel one at a time on suspect slopes, use islands of safety and communicate your decisions and plans within your group.

Avalanche Problem 2

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

Ridgetop winds have been in the 20-30 mph range since yesterday morning. Very shallow stiff slabs may be encountered today on steep (40 degrees and over) leeward slopes. These slabs will be small, around 4-6” deep and exist in small pockets. While the volume of any wind slabs triggered will be low, it will be important to avoid them when travelling above terrain traps such as cliffs, gullies and trees.

Weather

Tue, March 3rd, 2015

The past 24 hours saw mild temps with moderate ridegtop winds. Skies were mostly cloudy and less than a trace of new snow fell in the upper elevations.

Today expect more of the same. Winds will be out of the East at 15-20 mph. Very light snow under mostly cloudy skies will fall with a max of 2 € of accumulation. Rain/snow line will be around 1,000′. Temperatures at 1,000′ will be in the low to mid 30s F.

The extended outlook is showing a continuation of showery precipitation through the week, as a series of weak lows move through the area.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	34	0	0	40
Summit Lake (1400′)	34	0	0	7
Alyeska Mid (1700′)	34	trace	.06	22

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	24	ENE	20	51
Seattle Ridge (2400′)	26	NW	29	59

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

Riding Areas

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