Tue, December 08, 2015 Turnagain Pass Avalanche Forecast

Tue, December 8th, 2015

Alpine

Above 2,500'

1 - Low

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

Normal Caution

Normal Caution

Normal Caution means triggering an avalanche is unlikely but not impossible.

More info at Avalanche.org

The Turnagain Pass area saw another sunny day with moderate temperatures and no reports of significant instability. An observation from Saturday illustrates the potential for small slabs in steep areas, a typical LOW danger concern.

As the weather pattern shifts today, bringing showery weather and stronger winds, taking inventory of the surface characteristics is critical to get a picture of what may happen in the days to come as the conditions change. We know that any new precipitation will land on a combination of weak faceted snow and surface hoar that have formed over the past days during the cold clear weather. Underneath these persistent grain types, that could become persistent weak layers, is either a stout rain crust (up to around 2500′) or dense snow that could act as a future bed surface. A forecaster observation from Sunday speaks to what to keep in mind when thinking about near surface facets and surface hoar together.

***If winds increase today and snow is moved around pay attention to areas that are leeward and may develop small pockets of wind slab on the weak snow/bed surface combination.

Remember the surface conditions (facets and surface hoar to ridge tops) that may get buried this week.

Avalanche Problem 2

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

We are continuing to track the layer of basal facets from the cold period in early November. For the most part these have been non-reactive. With the potential for additional load in the coming week we will be interested to see if this changes.

Weather

Tue, December 8th, 2015

Today’s weather is forecasted to be a mixture of showery weather in the morning and then mostly to partly cloudy in the afternoon. There is the possibility of snow with up to an inch of accumulation. Temperatures will be in the upper 20Fs to mid 30Fs. Wind will be N-NE, 10-20 mph with gusts in the 30s.

Tomorrow the unsettled weather will continue as the low in the Gulf spins moisture into the region. Cloudy skies, snow showers and warmer temperatures are on tap for the week as the overall pattern shifts.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	22	0	0	23
Summit Lake (1400′)	15	0	0	11
Alyeska Mid (1700′)	25	0	0	19

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	22	NE	18	38
Seattle Ridge (2400′)	22	SE	15	38

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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