Sun, December 23, 2012 Turnagain Pass Avalanche Forecast

Sun, December 23rd, 2012

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. 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

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

With a good chance for new snow Monday, we will likely be talking about a whole host of different issues and dangerous avalanche conditions but, until then, we are still dealing with the old and tired “dragon in the dungeon”. This is our weak snow underneath strong snow problem that is scattered about the mountains. The dragon (weak faceted snow) is widespread but the strong snow (old wind slabs) are hiding in pockets. Though these slabs are slowly deteriorating to the point of non-reactivity and becoming harder to find, they cannot be written off.

Areas to watch for are steep slopes sporting stiff supportable snow that has a hollow feel underneath. Many areas, including steeper slopes and starting zones, are missing this stiff and cohesive slab because they have either already avalanched, been wind scoured or, if you are lucky, harbor loose faceted snow with decent riding conditions. That said, the snow surface is quite variable.

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Weather

Sun, December 23rd, 2012

Enjoy the mostly clear skies today as we have snow in the forecast! But first today’s conditions, the frigid temperatures have bumped up overnight €“ at least at the mid and upper elevations. Treeline and above are in the mid-teens this morning, where they should remain, but the inversion will stick around with parking lots in the minus single digits. Winds are currently light from the east and will pick up to the 20mph range by this evening with the approach of, yes, a storm.

Okay second, the storm, snow is finally on its way and it has the potential to add up by mid-week. A low pressure system developing south of Kodiak is intensifying and will start moving over our region tonight and through Tuesday. Snowfall numbers are looking to be in the 10-16 € range by Monday night with another system right on its heels bringing similar snow amounts. This first system is cold enough for snow at all elevations. Stay tuned for tomorrow’s forecast and a better look as the systems get closer.

This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (this advisory does not apply to highways, railroads, or operating ski areas).

John will issue the next advisory Monday morning, December 24th.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
04/21/24	Turnagain	Observation: Bertha Creek	Anonymous
04/20/24	Turnagain	Avalanche: Spokane Creek	Schauer/ Mailly Forecaster
04/16/24	Turnagain	Observation: Cornbiscuit	Krueger / Matthys Forecaster
04/15/24	Turnagain	Observation: Taylor Pass	John Sykes Forecaster
04/15/24	Turnagain	Observation: Seward Highway – Tern Lake to Portage	Joel Curtis
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

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