Mon, April 15, 2013 Turnagain Pass Avalanche Forecast

Mon, April 15th, 2013

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

Below Treeline

Below 1,000'

2 - Moderate

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

The unusually cool temperatures of this last spell of clear weather has helped to preserve the snow quality in many areas. This same weather pattern has also helped to weaken the snow in the upper foot of the snowpack. Throwing moderate winds into the mix has helped to move around this weak snow and create pockets of wind slab. As a result we have seen activity in the form of shallow wind slabs releasing throughout the forecast zone over the weekend. These slabs have now been sitting for a few days and will be less reactive than they have over the weekend. Despite this, it will still be prudent to pay attention to steep rollovers and wind loaded features above treeline.

Avalanche Problem 2

Wet Loose

Wet Loose

Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

More info at Avalanche.org

The temperatures will rise enough today in the lower elevations to require careful observation of the snow surface on sunlit slopes. As the thermometer reading goes above freezing and the sun hits steep low elevation slopes, watch for small rollerballs, pinwheels and shallow point releases.

Additional Concern

Dry Loose

Dry Loose

Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

More info at Avalanche.org

Loose Snow Avalanches. Those venturing into big and steep terrain will need to manage sluff today. Volume will be generally low and will become a greater concern in exposed terrain and above terrain traps.

Weather

Mon, April 15th, 2013

The clear and relatively cold weather of the past week warmed slightly yesterday, with temps at Sunburst reaching a high of 20.8 degrees F and averaging 17 F. Winds calmed down (from an average in the teens in the morning) in the afternoon and have averaged 7 mph out of the northwest. No new precip has fallen in the past 24 hours.

In the mountains today temperatures will climb into the mid 30s F at 1,000′. Skies will remain mostly clear with potential for some clouds moving in late in the day. Winds will be very calm at 0-5 mph out of the north and northwest. No measurable precipitation is on the horizon for the next 24 hours.

The extended outlook is calling for continued dry conditions over the next several days.

Wendy will issue the next advisory tomorrow morning, April 16th.

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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