Sat, December 07, 2013 Turnagain Pass Avalanche Forecast

Sat, December 7th, 2013

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. 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

More info at Avalanche.org

Conditions right now are odd for December in Alaska. Total snow depth is only 15-30 inches, barely enough to justify putting boards on your feet. Exposed rocks and trees continue to be the primary backcountry hazard.

In some ways the snowpack is showing characteristics of typical Spring conditions with point release avalanches possible in the warmer and higher elevation areas. Unlike springtime, the wet/loose activity is entraining weaker faceted snow and volume is severely limited by the shallow snowpack. The freezing rain and temperature inversion started forming an ice crust a couple days ago, but in areas where temperatures have been above freezing for 24 hours, the crust has given way to soft and wetter snow.

This combination is allowing for low volume wet/loose avalanches that can travel at slow speeds for a reasonable distance if the slope is steep enough. Probably nothing to be afraid of, but something to watch for, and definitely atypical for December. Point release activity like this has been seen around Summit Lake and in the Girdwood valley.

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 got a report this morning of significant avalanche debris in the Portage valley near a popular ice climb, fresh in the last couple days. This is a great reminder that specific terrain features can harbor problems, especially when you are dealing with big, steep terrain and finicky weather in places like Portage.

Avalanches like this are the main reason why we don’t believe our avalanche advisory for Turnagain Pass is a good indicator for Portage, Whittier, or the heavily glaciated regions closer to Prince William Sound.

Weather

Sat, December 7th, 2013

Rain was falling across our region on Thursday. That trend dried out yesterday, but temperatures have been above freezing for most of the last 24 hours at all elevations.

This morning we can see a temperature inversion again. Sea level temperatures are cooling off and dipping below freezing. Ridge top temperatures are still in the upper 30s, the rain/snow line is predicted at 5600ft today. Wind is light from the northwest.

Looking into the future, a cooling trend is expected. No major snowfall is in the forecast. This means we can expect a stout melt/freeze crust to firm up this week.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
10/27/24	Turnagain	Observation: Tincan	Michael Kerst
10/21/24	Turnagain	Observation: Turnagain Pass Road Observation	Trevor Clayton
10/19/24	Turnagain	Observation: Tincan – Below Todds Run	Andy Moderow
10/18/24	Turnagain	Observation: Taylor Pass	Eli Neuffer
10/15/24	Turnagain	Observation: Tincan Common	John Sykes Forecaster
10/14/24	Turnagain	Avalanche: Tincan	CNFAC Staff
05/13/24	Turnagain	Observation: Eddie’s, Sunburst, Seattle, Cornbiscuit, Pete’s South	H Thamm
05/13/24	Turnagain	Observation: Turnagain Pass non-motorized side	Amy Holman
05/12/24	Turnagain	Observation: Warm up Bowl	Tony Naciuk
05/07/24	Turnagain	Observation: Turnagain Pass Wet Slabs	A S

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