Sun, January 22, 2017 Turnagain Pass Avalanche Forecast

Sun, January 22nd, 2017

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

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

Yesterday’s impressive snowfall event not only made the news, but also caused a bit of havoc on the Southern Kenai. Here is a rundown of the snowfall numbers around the region – including many areas outside our forecast zone:

Storm Totals: (estimates based on manual reports and station data)

Crown Point (7 miles South of Moose Pass): 40-52″ !!
Moose Pass: 28-32″
Seward: 24-30″
Hatcher Pass: 14-17″
Summit Lake: 12-16″
Anchorage: 10-14″
Girdwood Valley: 6-8″
Turnagain Pass: 6-8″

Another 1-3″ is expected in favored areas today. All this snow is very low density and fallen with relatively little wind. As you can see, our forecast zone (mountains around Girdwood and Turnagain Pass) were the losers in the event and avalanche danger remains at MODERATE for slab avalanches and sluffs. A party skiing the Cornbiscuit area triggered several shallow slab avalanches yesterday as well as high volume sluffs. Check out their report on the link.

If skies clear enough for travel to the upper elevation slopes, keep a lookout for where the winds drifted snow during the storm. Triggering a wind slab on the steeper slopes is possible, these are likely to be on the shallow side, 8-12″ thick, and could break well below the ridgeline as was the case with the folks on Cornbiscuit yesterday. Feel for hollow feeling snow, stiffer snow over softer snow and cracks that shoot out from your snowmachine, skis or board.

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

There is a significant amount of loose snow from not only yesterday’s storm but the snowfall earlier in the week. Expect sluffs to be triggered on slopes approaching 40 degrees. These are likely to be high volume and run fast and far. Sluff management will be key.

Additional Concern

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

At the lower elevations, below 2,000′, a layer of buried surface hoar exists under the last two snowfall events (12-18″ below the surface). Slab avalanches failing on this layer are possible where the snow on top is stiff enough to form a slab. In most locations, the snow is too loose and therefore triggering a slab in unlikely, but it seems the party on Cornbiscuit may have found one of these lower slopes that did indeed have enough of a slab on this suspected buried surface hoar. The lower terrain in Placer Valley is a prime suspect for this set up.

Photo: Buried Surface Hoar 18″ below the surface – seen as a thin grey line. This was at 1,700′ on the Southern end of Turnagain Pass – Pete’s North (Galoob and Haffener).

At the upper elevations, there are a variety of weak layers in the middle of the pack as well as the base of the pack. These are more pronounced in the Girdwood Valley and the Southern end of the Pass where the snowpack is thinner. Although, we have not seen avalanche activity break in these older weak layers, it is good to keep this in mind if venturing into the less traveled zones.

Weather

Sun, January 22nd, 2017

Yesterday’s snow storm, as mentioned above, brought very different snow amounts to the region. Snowfall tapered off at most locations during the day and skies have mostly cleared overnight. Ridgetop winds associated with the snow were 15-20mph from the East and have backed off to 5-10mph overnight from the East. Temperatures have been in the teens at all elevations during the past 24-hours.

Today, instability snow showers are expected to add 1-3″ in favored areas. This means, opening skies in some areas and cloudy with light snowfall in others. Ridgetop winds should be light from the South and East, 5-10mph and temperatures continue to sit in the 10-15F range at all elevations.

For tomorrow, there is a break between storms as a large low-pressure system heads our way. This storm should reach us sometime late Monday or Tuesday. Stay tuned!

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	13	4	0.3	45
Summit Lake (1400′)	11	6	0.4	27
Alyeska Mid (1700′)	11	4	0.2	42

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	16	E	8	27
Seattle Ridge (2400′)	14	E	7	25

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
04/15/24	Turnagain	Observation: Taylor Pass	John Sykes Forecaster
04/14/24	Turnagain	Observation: Sunburst	T. Olsen-Lund, R. Sullivan I. Adams
04/14/24	Turnagain	Observation: Turnagain Pass Snomo	K. Gallaher
04/13/24	Turnagain	Observation: Spokane Creek	Everet Megli
04/11/24	Turnagain	Observation: Tincan	John Sykes Forecaster
04/10/24	Turnagain	Avalanche: Seattle Ridge	Schauer/ Keeler Forecaster
04/10/24	Turnagain	Observation: Cornbiscuit South Face	Todd Kelsey
04/10/24	Turnagain	Avalanche: Tincan	N. Dumont J. Carlberg
04/10/24	Turnagain	Avalanche: Cornbiscuit	Tyler Grundstrom
04/07/24	Turnagain	Observation: Seattle Creek Headwall	Troy Tempel

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