Fri, December 16, 2016 Turnagain Pass Avalanche Forecast

Fri, December 16th, 2016

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. Dangerous avalanche conditions.	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

With skiers and riders eagerly anticipating a change in the weather pattern, yesterday afternoon did not disappoint with the first few flakes falling in over two weeks! Though yesterday’s surface is now buried, let’s not forget the poor foundation we’ve laid during the first half of December. Effectively we’ve got buried surface hoar (Nov.16^th) obscured by about 12” of loose faceted (sugar) snow capped off by more surface hoar now buried by last nights new snow. It’s unlikely we’ll get enough of a load today to build a slab on this weak foundation, but with an increase in easterly winds, a skier may be able to tickle out a shallow, tender wind slab. Any avalanche today is expected to be small and manageable. That being said, be mindful of terrain traps such as cliffs and rocks where the consequences of getting caught up in a small avalanche are compounded. Light snowfall is expected to continue throughout the day and increase in intensity after dark. If snowfall rates begin to intensify during daylight hours, the avalanche danger will rise to moderate, making small, human triggered avalanches possible, particularly in the alpine where wind will be more of a factor.

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

New snow falling today will not bond well to yesterday’s loose surface. Keep in mind that steep terrain may produce ‘facet sluffs’/ loose snow avalanches with more volume than we’ve seen to date this season.

Yesterdays surface: 2-3mm surface hoar, mostly laid down and resting on a 10-12″ layer of weak faceted snow. This thick layer of facets is likely to act as our next weak layer.

Weather

Fri, December 16th, 2016

The temperature inversion broke yesterday afternoon with temps at sea level rising from single digits to the mid to high 20’sF overnight. Ridgetops temps were comfortable in the low 20’s for most of the day and winds began to kick up from the ESE last night with the approaching storm. Skies were mostly clear with high clouds streaming in during the daylight hours yesterday and the first few flakes falling around 5PM.

Storm totals overnight were less than impressive with Summit Lake looking to be the winner with about 3 € new snow. Turnagain pass and Girdwood are reporting 1-2 € this morning.

Today we can expect a bit of a lull as this current short wave moves out of the area to be replaced by a slightly stronger wave of energy this evening and overnight. We can expect light snow during the daylight hours (another 1-3 €), ridgetop winds from the SE in the 10-25mph range and temps at 1,000′ in the 26-33 degree range.

In general we have entered a stormy period, where a parent low in the Bering Sea looks to be supporting unsettled weather across south-central Alaska at least through the weekend. For the most part temperatures appear to be cold enough to support mostly snow to sea level, though we may see a short period of rain/ snow at sea level overnight tonight before turning back to snow by the weekend.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	24	1-2	.1	21
Summit Lake (1400′)	19	3	.4	8
Alyeska Mid (1700′)	25	2	.15	11

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	22	E	6	22
Seattle Ridge (2400′)	22	SE	12	32

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
11/16/23	Turnagain	Observation: Tincan Common	William Finley
11/14/23	Turnagain	Observation: Sunburst/Magnum	Adrian Beebee
11/14/23	Turnagain	Observation: Seattle Ridge	Schauer/ Creighton/ Ellis Forecaster
11/13/23	Turnagain	Avalanche: Tincan Trees	Eeva Latosuo
11/12/23	Turnagain	Observation: Sunburst	Schauer/ Creighton/ Nave Forecaster
11/12/23	Turnagain	Avalanche: Goldpan – avalanche	Mike Records
11/11/23	Turnagain	Observation: Tincan Common	Andy Moderow
11/11/23	Turnagain	Observation: Taylor Pass – Sunburst	Wadsworth / Stwertka
11/10/23	Turnagain	Observation: Tincan	Andrew Schauer Forecaster
11/10/23	Turnagain	Observation: Tincan Trees	Michael Kerst

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