Mon, February 09, 2015 Turnagain Pass Avalanche Forecast

Mon, February 9th, 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

The last 3 weeks of clear and cool weather has helped to create very weak snow on the surface throughout the forecast area. A lack of significant loading from precipitation or wind has kept avalanche activity to a minimum. An exception to this was found over the weekend in the Girdwood Valley, where strong Northerly winds on Friday loaded fresh slabs onto this weak snow surface. Turnagain Pass was shielded by the Chugach Range from this outflow wind event.

What this leaves us with is a tale of two different snowpacks.

On Turnagain Pass, the core of the forecast area, you will find very shallow pockets of fresh slab 3-4” deep that have built as a result of light snowfall and moderate winds over the past 24 hours. Wind will help to build slabs as thick as 8” by the end of the day on leeward slopes. These pockets could become deeper if additional snowfall exceeds the forecasted 2-3” snow for today.

In the Girdwood Valley you can expect to encounter stiff wind slabs in the mid to upper elevations that are several days old. These slabs are hard and sitting on very weak snow. These slabs will grow slightly today with average depth in the 6-8″ range. It is important to be able to recognize wind loaded features. Wind loaded slopes will feel stiff and sound hollow. Shooting cracks radiating from your skis, board or feet are an obvious indicator of unstable snow.

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

In areas not affected by wind, expect sluffing to occur easily in steep terrain. New low density snow combined with the older weak snow will be easy to trigger and low in volume. If visibility allows travel into upper elevation steep terrain today, watch any sluff that you trigger and steer away from it.

Weather

Mon, February 9th, 2015

A frontal boundary pushing up from the south has helped to bring about a change over the past 24 hours. Light amounts of snow have accumulated, with 2 € of new snow on Turnagain Pass. Temperatures have seen a pronounced upswing, with ridgetop stations reading in the teens to 20 F range this morning. Winds out of the East have also picked up with Sunburst reporting averages in the teens to 20 mph overnight.

Today expect showery conditions. Snowfall amounts will be light, in the 2 € to 3 € range. Ridgetop winds will be out of the East at 10 to 15 mph. Temperatures at 1,000′ will be in the mid to high 20s F.

An unsettled pattern will help to bring chances for snow through the coming week. Temperatures will fluctuate and gradually rise as we move through the work week.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	11	2	.1	33
Summit Lake (1400′)	7	trace	trace	7
Alyeska Mid (1700′)	10	2.3	.12	24.5

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	13	E	12	35
Seattle Ridge (2400′)	12	var	6	18

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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