Fri, December 12, 2014 Turnagain Pass Avalanche Forecast

Fri, December 12th, 2014

Alpine

Above 2,500'

1 - Low

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. 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

Snow pit test results and some substantial slope testing are pointing toward a snowpack that is gaining strength and losing energy in the upper elevations as we put time between now and the (Dec. 7-9) warm storm of earlier this week. Perhaps the most significant slope test in the backcountry yesterday was observed when a large cornice block failed unintentionally landing on a steep (~40 degree) slope pulling out only a small slab. Without investigating fully, this is where I’d expect to find isolated pockets of stubborn wind slab in the 12″ range. If entering steep, committing terrain just below ridges today, practice safe travel protocol and good situational awareness identifying both safe zones and escape routes. An avalanche today is unlikely large enough to bury a person but moving snow could be enough to knock you off your skis or sweep you into a terrain trap.

We have observed widespread surface hoar growth throughout the Turnagain zone over the last 2 days. Though not an issue today, this is sitting on a variety of surface types and could prove problematic if buried in-tact. We’ll be mapping this layer carefully with subsequent storms.

Early season hazards and a tenacious rain crust in the mid elevations (consistency of skiing over a coral reef) are legitimate concerns and require careful travel in order to avoid injury. Boot-packing in the 1,000 – 1,500’ elevation band was by far the most hazardous part of our tour yesterday due to ice, early season hazards and a lack of snow.

Avalanche Problem 2

Cornice

Cornice

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

More info at Avalanche.org

My partner and I witnessed 2 separate human triggered cornice failures in a matter of a half hour on the Tin Can ridge leading up to Hippy bowl yesterday. Cornices in our region are fairly well developed for this early in the season. Recognize them, and give them an extra WIDE BERTH if travelling on corniced ridges. This holds true today and always!

2 separate cornice failures resulted from skiers traversing the ridge. Hippy bowl on Tin Can.

Additional Concern

Glide Avalanches

Glide Avalanches

Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.

More info at Avalanche.org

Being nearly impossible to predict or forecast glide avalanche failure, your best bet will be to simply avoid exposure to glide cracks entirely. This avalanche concern is like a wild Horse; it has the ability to be tame through the entire season and melt out benignly or, release catastrophically without warning unleashing a fury of destruction.

Weather

Fri, December 12th, 2014

The welcomed cooling trend continued yesterday across our region with all the weather stations (except Whittier) reading below freezing temperatures and dipping to the low 20’s F. A lack of wind allowed a persistent fog bank to embed from the Anchorage bowl down Turnagain arm and south over Turnagain pass. Just a trace of snow was observed on vehicles in Girdwood yesterday morning, really just precip particles associated with a low fog bank. Above the fog (roughly 1,900′) the sky was blue, winds were calm and the atmosphere stable.

Weather looks to be quiet again today with weak surface flow likely not pushing the fog out of the region. It’ll likely be another grey day at sea level but if you are fortunate enough to be in the mountains today, sunshine abounds above the low cloud deck! We may see a small bump in temperatures to the high 20’s F at 1,000′ with ridgetop winds remaining in the single digits from the east. No precipitation is expected today.

Our next best chance for winter-ish weather appears to be tomorrow afternoon and into Sunday with a significant low tracking across the north Pacific today. There appears to be plenty of moisture associated with this system and temps appear to be hovering right around the freezing mark.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	21	0	.1	18
Summit Lake (1400′)	19	o	o	4
Alyeska Mid (1700′)	24	0	.1	11.8

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	21	W	5	13
Seattle Ridge (2400′)	23	SE	3	9

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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