Sun, February 02, 2014 Turnagain Pass Avalanche Forecast

Sun, February 2nd, 2014

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

Deep Persistent Slabs

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

More info at Avalanche.org

We have relatively little information from the last 5 days because so few people are getting into the backcountry right now. Conditions are challenging with a hard “chattering” crust below treeline that is a prerequisite before you gain the slightly softer zone above treeline.

The last major high elevation deep slab that we know of was a week ago on Goat Mountain in the Girdwood valley. Remember that this problem doesn’t stabilize quickly like a storm slab problem.

Above treeline the snowpack is thick, with weak snow at and near the ground. We have been able to cause failures on these layers in test pits.

Managing this low likelihood, high consquence problem can be accomplished by limiting travel in steep terrain. If that isn’t an option, then exposing one person at a time to steep terrain will reduce risk exposure.

Avalanche Problem 2

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

Recent wind has been limited, so wind slabs are generally older. Above treeline there can be found some soft snow and some wind stiffened snow. Watch out for pockets of stiff wind slab that may fail in small avalanches. Unstable cornices are another subcategory that fits into wind slab concerns.

Additional Concern

Announcement

Announcement

More info at Avalanche.org

Wendy posted this summary yesterday, which gives us a good look at the recent weather.

With many days of unseasonably warm weather during January, some of us are wondering just where did we stack up in the monthly averages. There is more data to crunch so stay tuned – but we do have a few sets of interesting numbers. Below are graphs of precipitation, SWE (Snow Water Equivalent) and Temperature.

Weather

Sun, February 2nd, 2014

We have not had any significant precipitation for the past week.

Current weather has a temperature inversion across the region. Sea level temperatures are in the mid to high teens, ridge top temperatures are in the high 20s. Valley fog has dominated Turnagain Arm for a few days, and this will likely continue today. Wind has been light for several days now. These conditions are building surface hoar crystals, which could become a buried weak layer the next time it snows.

The blocking high pressure pattern is expected to continue this week. By the end of the week – computer models are showing a pattern change but the exact nature of that weather remains uncertain.

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

Riding Areas

The riding areas page has moved. Please click here & update your bookmarks.