Thu, February 07, 2013 Turnagain Pass Avalanche Forecast

Thu, February 7th, 2013

Alpine

Above 2,500'

3 - Considerable

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

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

Forecasted 40-55 mph east winds are guaranteed to build very tender and sensitive wind slabs with yesterday’s 4-8” of light powder combined with today’s storm snow. As you gain in elevation, slabs will be actively forming throughout the day on a variety of bed surfaces including breakable crusts, buried surface hoar (observed on Tuesday in Girdwood and Turnagain) and in the upper elevations older wind slab.

Below tree line where winds are not as intense, avalanche size is likely to be small though human triggered avalanches will be possible. Slabs will form mostly on a breakable crust at these lower elevations.

Above tree line expect slabs to form in all the usual places; below ridgelines on west-facing (leeward) slopes and cross-loaded gullies. With moderate to high winds, slopes tend to load further downhill than one would think, often luring a skier or snowmachiner mid-slope before finding the trigger point. The likelihood of triggering a slab in terrain greater than 35 degrees today is probable; there is however some uncertainty on just how big an avalanche may be.

As a fresh shot of wind and moisture rolls in today it is worth mentioning that at higher elevations there still exists weak, faceted snow at the bottom of our pack. Though we have not seen an avalanche fail on this layer in several weeks, deep slab instabilities are notorious for lying dormant for long periods only to suddenly awake and catch us off guard. At this point, safe travel protocol will be your best bet to avoid this avalanche concern.

Avalanche Problem 2

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

If you happen to find areas sheltered from the wind today, yesterday’s low-density powder combined with storm snow will create fast-moving loose snow sluffs in steep terrain. If expected, these loose-snow slides should prove quite manageable.

Weather

Thu, February 7th, 2013

Well it looks to be a bonafide storm day in the eastern Turnagain Arm region today. Expect this system to ramp up throughout the daylight hours bringing 8-16 € of snow (at all elevations!) and 40-55 mph winds from the east. Temps look to be in the mid to high 20’s at 1000′ and should stay below freezing at sea level. A BLIZZARD WARNING remains in effect today from 10 AM to 6 PM.

Tomorrow looks to be a break in action before another weather front moves into south-central over the weekend. This next system looks promising for more wind and precipitation.

Fitz will issue the next advisory tomorrow morning, February 8th.

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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